Method and ue performing sidelink operation and device for controlling ue

Abstract

The disclosure relates to a method of performing a sidelink operation, a UE, and a device controlling the UE. The disclosure provides a vehicle-to-X (V2X) operation method performed by a V2X terminal in a wireless communication system, the method including: selecting, in a selection period, a subframe excluding a subframe related to a subframe in which transmission is performed during a sensing period; and performing V2X communication based on the selected subframe.

Description

[0001] This application is a divisional application of the original application No. 201780041795.2 (International Application No. PCT / KR2017 / 003844, filed on April 7, 2017, entitled "Method for selecting subframes excluding subframes related to subframes on which transmission was performed during a sensing period, in addition to subframes selected in a selection period, in a wireless communication system, and terminal using the same"). Technical Field TECHNICAL FIELD

[0002] The present application relates to wireless communications, and more specifically, to a method for selecting V2X transmission resources by a terminal in a wireless communication system, and a terminal using the same. BACKGROUND

[0003] The International Telecommunication Union Radio (ITU-R) is in the process of standardizing International Mobile Telecommunications (IMT)-Advanced, which is a next-generation mobile communication system after the 3rd generation partnership project (3GPP) long term evolution (LTE). The IMT-Advanced aims to support an Internet protocol (IP) based multimedia service at a data rate of 1 Gbps when a terminal is at a fixed location or moves at a low speed, and at a data rate of 100 Mbps when a terminal moves at a high speed.

[0004] The 3rd generation partnership project (3GPP) is developing LTE-A, which is an advanced version of long term evolution (LTE) based on an orthogonal frequency division multiple access (OFDMA) / single carrier-frequency division multiple access (SC-FDMA) transmission scheme, as a system standard that meets the requirements of IMT-Advanced. LTE-A is one of the strong candidates for IMT-Advanced.

[0005] Recently, there is increasing interest in a device-to-device (D2D) technology that allows direct communication between devices. In particular, D2D communication is being highlighted as a communication technology for implementing a public safety network. Although commercial communication networks are rapidly changing to adopt the LTE standard, the current public safety network still relies on 2G technology due to a conflict problem with existing communication standards and a cost problem. This technology gap, along with the demand for improved services, has led to efforts to improve the public safety network.

[0006] D2D communication can be extended to signal transmission and reception between vehicles, in which vehicle-related communication is specifically referred to as vehicle-to-everything (V2X) communication. The "X" in V2X denotes a pedestrian (communication between a vehicle and a device carried by a pedestrian (e.g., a handheld terminal carried by a pedestrian, a cyclist, a driver, or a passenger), in which case V2X can be denoted by V2P), a vehicle (communication between vehicles, V2V), infrastructure / network (communication between a vehicle and a roadside unit (RSU) / network, in which the RSU is a traffic infrastructure entity, such as an entity implementing a transmission speed notification in an eNB or a fixed UE, V2I / N). A device carried by a pedestrian (or a person) related to V2P communication is referred to as a "P-UE", and a device installed in a vehicle related to V2X communication is referred to as a "V-UE". The term "entity" in this document can be interpreted as a P-UE, a V-UE, or an RSU ( / network / infrastructure).

[0007] Further, in V2X communication, it can be problematic in which way a resource is selected when a P-UE attempts to transmit a V2X signal. Unlike a vehicular terminal, a P-UE tends to be sensitive to battery consumption. In addition, in V2X communication, it can be important to periodically transmit a signal and not impose interference on other terminals. The above facts need to be considered to determine a method of selecting a transmission resource for a P-UE. SUMMARY

[0008] TECHNICAL PROBLEM

[0009] The present application aims to provide a method for selecting a V2X transmission resource performed by a UE in a wireless communication system and a UE using the same.

[0010] TECHNICAL SOLUTION

[0011] In an aspect, a method of performing a vehicle-to-X (V2X) operation in a wireless communication system is provided. The method can be performed by a V2X user equipment (UE) and includes selecting subframes to exclude from subframes related to performing transmission in a sensing duration for a selection duration and performing V2X communication based on the selected subframes.

[0012] The excluded subframes can be subframes in the selection duration.

[0013] The related subframe can be excluded when a subframe corresponding to the subframe in which transmission is performed in the sensing duration based on a certain period overlaps with a subframe reserved according to a resource reservation period of the related subframe.

[0014] The subframe in which the transmission can be performed is subframe k, and k is a positive integer, the subframe corresponding to the subframe k based on a certain period can be subframe (k+100*i), and i can be a positive integer configured by the base station, and if the subframe (k+100*i) overlaps with the subframe (y+P*j), the subframe y can be excluded, and y can be a positive integer, P can be a resource reservation period, and j can be a positive integer.

[0015] The range of j can be determined based on a positive integer value proportional to a counter value randomly determined by the V2X UE.

[0016] The counter value can be equal to or greater than 5 and equal to or less than 15.

[0017] P can be 100 ms.

[0018] The sensing period can be 1 s, and the selection duration can be 100 ms.

[0019] The sensing duration can be a sensing window, and the selection duration is a selection window.

[0020] The sensing window can be specific to the V2X UE.

[0021] In another aspect, a user equipment (UE) is provided. The UE can include a radio frequency (RF) unit that transmits and receives a radio signal, and a processor that operates in combination with the RF unit. The processor can be configured to select, within a selection duration, a subframe that excludes a subframe related to a subframe in which a transmission is performed within a sensing duration, and perform vehicle-to-X (V2X) communication based on the selected subframe.

[0022] Advantageous Effects

[0023] According to the present application, when the UE performs V2X communication, resources involved in the V2X communication can be reserved in an efficient manner. Therefore, since the UE according to the present application efficiently utilizes radio resources, unnecessary occupation of the radio resources is minimized, so that the efficiency of the radio resources is maximized. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A wireless communication system to which the present application is applied is illustrated.

[0025] Figure 2 is a diagram illustrating a radio protocol architecture for a user plane.

[0026] Figure 3 is a diagram illustrating a radio protocol architecture for a control plane.

[0027] Figure 4 A reference structure for ProSe is illustrated.

[0028] Figure 5 An example of an arrangement of terminals performing ProSe direct communication and a cell coverage area is shown.

[0029] Figure 6 A user plane protocol stack for ProSe direct communication is shown.

[0030] Figure 7 A PC 5 interface for D2D discovery is shown.

[0031] Figure 8 is a flowchart showing a method of performing V2X communication based on a UE-specific sensing period according to an embodiment of the present application.

[0032] Figure 9 An example of a UE-specific sensing window is shown.

[0033] Figure 10 is a flowchart showing a method of configuring a selection window according to an embodiment of the present application.

[0034] Figure 11 and Figure 12 A proposed rule #1 is shown.

[0035] Figure 13 and Figure 14 A determination to re-reserve (or select) resources and to immediately perform a V2X message using the re-reserved (or selected) resources is shown.

[0036] Figure 15 and Figure 16 An example of a case where (from the perspective of a "single V2X UE") "control (or scheduling) information" and "(data associated with the corresponding control (or scheduling) information)" are transmitted on the same SF according to a frequency division multiplexing (FDM) scheme is shown.

[0037] Figure 17 An example of a case where (from the perspective of a system) a "control (or scheduling) information transmission pool" and a "data transmission pool" are defined (or configured) according to an "FDM" scheme is shown.

[0038] Figure 18 is a flowchart showing a method of performing sensing when a plurality of sub-channels are used to transmit a V2X message according to an embodiment of the present application.

[0039] Figure 19 An example of performing energy measurement (i.e., sensing) with a sub-channel size of data to be transmitted by a UE is shown.

[0040] Figure 20 and Figure 21One example of "sensing based on partially overlapping areas" (or "sliding window based sensing") is shown.

[0041] Figure 22 A case where the "System Frame Number (SFN wraparound) problem" occurs is shown.

[0042] Figure 23 is a flowchart showing a method of reserving a limited number of resources according to one embodiment of the present application.

[0043] Figure 24 is a flowchart of a method of selecting resources by a UE according to one embodiment of the present application.

[0044] Figure 25 One example of a method of performing resource reservation considering the above proposal is shown.

[0045] Figure 26 is a flowchart of a method of excluding (from the selection window) subframes related to subframes in which the UE failed to perform sensing according to one embodiment of the present application.

[0046] Figure 27 One example of (from the selection window) subframes related to subframes in which the UE failed to perform sensing is shown.

[0047] Figures 28 to 30 One example of reflecting resources in the "(PSSCH-RSRP measurement based) resource exclusion procedure" is shown.

[0048] Figure 31 One example of a case where the (existing) "DFN range" value (e.g., "10240" or "10176") is increased is shown.

[0049] Figure 32 One example of transmitting updated system information is shown.

[0050] Figure 33 One example of a super DFN is shown.

[0051] Figure 34 is a flowchart of a method of performing V2X communication on an allocated V2X resource pool according to one embodiment of the present application.

[0052] Figure 35 One example of excluding SLSS subframes from V2X transmissions is shown.

[0053] Figure 36 One example of excluding DL and S subframes from V2X transmissions is shown.

[0054] Figure 37is a flowchart of a method of performing reservation of V2X transmission resources when resource reservation is set with a relatively short period (e.g., 20 ms or 50 ms (shorter than 100 ms)) according to an embodiment of the present application.

[0055] Figure 38 is a flowchart of a method of performing sensing with a relatively short period when resource reservation is set with a short period according to an embodiment of the present application.

[0056] Figure 39 is a block diagram of a UE implementing an embodiment of the present application. DETAILED DESCRIPTION

[0057] Figure 1 A wireless communication system to which the present application is applied is shown. The wireless communication system can also be referred to as an evolved-UMTS terrestrial radio access network (E-UTRAN) or a long term evolution (LTE) / LTE-A system.

[0058] The E-UTRAN includes at least one base station (BS) 20 which provides a control plane and a user plane to a user equipment (UE) 10. The UE 10 can be fixed or mobile, and can be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a mobile terminal (MT), a wireless device, etc. The BS 20 is generally a fixed station that communicates with the UE 10 and can be referred to as another terminology, such as an evolved node-B (eNB), a base transceiver system (BTS), an access point, etc.

[0059] The BSs 20 are interconnected by means of an X2 interface. The BSs 20 are also connected by means of an S1 interface to an evolved packet core (EPC) 30, more specifically, to a mobility management entity (MME) by means of S1-MME and to a serving gateway (S-GW) by means of S1-U.

[0060] The EPC 30 includes the MME, the S-GW, and a packet data network gateway (P-GW). The MME has access information of the UE or capability information of the UE, which is generally used for mobility management of the UE. The S-GW is a gateway having E-UTRAN as a termination point. The P-GW is a gateway having a PDN as a termination point.

[0061] Layers of a radio interface protocol between the UE and the network can be classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the open system interconnection (OSI) model that is well-known in the communication system. Among them, a physical (PHY) layer belonging to the first layer provides an information transfer service using a physical channel, and a radio resource control (RRC) layer belonging to the third layer functions to control a radio resource between the UE and the network. To this end, the RRC layer exchanges RRC messages between the UE and the BS.

[0062] Figure 2 is a diagram illustrating a radio protocol architecture for a user plane. Figure 3 is a diagram illustrating a radio protocol architecture for a control plane. The user plane is the protocol stack used for user data transfer. The control plane is the protocol stack used for control signal transfer.

[0063] Referring to Figure 2 and Figure 3 , the PHY layer provides a higher layer with an information transfer service through a physical channel. The PHY layer is connected with a Medium Access Control (MAC) layer, which is an upper layer of the PHY layer, through a transport channel. Data between the MAC layer and the PHY layer is transferred through the transport channel. The transport channel is classified into a data channel for data transfer and a control channel for control signal transfer between the MAC layer and the PHY layer. The data channel and the control channel are also classified into a shared channel and a dedicated channel according to how they transmit data.

[0064] Data moves between different PHY layers, i.e., a PHY layer of a transmitter and a PHY layer of a receiver, through the physical channel. The physical channel can be modulated according to an Orthogonal Frequency Division Multiplexing (OFDM) scheme, and uses time and frequency as radio resources.

[0065] The functions of the MAC layer include mapping between a logical channel and a transport channel, and multiplexing and demultiplexing of a transport block provided by the physical channel into a MAC Service Data Unit (SDU) belonging to the logical channel. The MAC layer provides a Radio Link Control (RLC) layer with a service through a logical channel.

[0066] The functions of the RLC layer include concatenation, segmentation, and reassembly of RLC SDUs. In order to ensure various types of Quality of Service (QoS) required by radio bearers (RBs), the RLC layer provides three types of operation modes: a Transparent Mode (TM), an Unacknowledged Mode (UM), and an Acknowledged Mode (AM). The AM RLC provides error correction through an Automatic Repeat reQuest (ARQ).

[0067] The RRC layer is only defined on the control plane. The RRC layer is associated with the configuration, reconfiguration, and release of a radio bearer (RB), and is responsible for the control of logical, transport, and physical channels. The RB indicates a logical route for data transmission between the UE and the network provided by the first layer (PHY layer) and the second layer (MAC layer, RLC layer, and PDCP layer).

[0068] The functions of the Packet Data Convergence Protocol (PDCP) layer in the user plane include the transfer of user data and header compression and encryption. The functions of the PDCP layer in the user plane also include the transfer of control plane data and encryption / integrity protection.

[0069] RB is configured what means a procedure of defining characteristics of a radio protocol layer and a channel in order to provide a specific service and configuring various detailed parameters and operation methods. The RB can be classified into two types of a signaling RB (SRB) and a data RB (DRB). The SRB is used as a channel for transmitting an RRC message on a control plane, and the DRB is used as a channel for transmitting user data on a user plane.

[0070] If an RRC connection is established between an RRC layer of the UE and an RRC layer of the E-UTRAN, the UE is in an RRC connected state. If not, the UE is in an RRC idle state.

[0071] Downlink transport channels for transmitting data from the network to the UE include a broadcast channel (BCH) for transmitting system information and a downlink shared channel (SCH) for transmitting user traffic or control messages. Traffic or control messages of a downlink multicast or broadcast service can be transmitted through the downlink SCH or can be transmitted through an additional downlink multicast channel (MCH). Further, uplink transport channels for transmitting data from the UE to the network include a random access channel (RACH) for transmitting initial control messages and an uplink shared channel (SCH) for transmitting user traffic or control messages.

[0072] Logical channels mapped to the transport channels include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic channel (MTCH).

[0073] A physical channel includes a plurality of OFDM symbols in the time domain and a plurality of subcarriers in the frequency domain. One subframe includes a plurality of OFDM symbols in the time domain. An RB is a resource allocation unit including a plurality of OFDM symbols and a plurality of subcarriers. In addition, certain subcarriers of a certain OFDM symbol (e.g., a first OFDM symbol) of the corresponding subframe can be used for a physical downlink control channel (PDCCH), that is, an L1 / L2 control channel. A transmission time interval (TTI) is a unit time of subframe transmission.

[0074] Hereinafter, a D2D operation will be described. In the 3GPP LTE-A, a service related to the D2D operation indicates a Proximity Service (ProSe). Hereinafter, the ProSe is a concept equivalent to the D2D operation, and the ProSe can be used compatibly with the D2D operation. The ProSe will now be described.

[0075] ProSe includes ProSe direct communication and ProSe direct discovery. The ProSe direct communication indicates communication performed by two or more neighboring terminals. The terminals can perform the communication using a user plane protocol. The ProSe-enabled UE means a UE supporting a process related to requirements of the ProSe. Unless otherwise defined, the ProSe-enabled UE includes both a public safety UE and a non-public safety UE. The public safety UE indicates a UE supporting both a public safety-specific function and a ProSe process, and the non-public safety UE is a UE supporting a ProSe process but not a public safety-specific function.

[0076] The ProSe direct discovery is a process in which a ProSe-enabled UE discovers another ProSe-enabled UE. In this case, only capabilities of the two ProSe-enabled UEs are used. The EPC-level ProSe discovery indicates a process in which an EPC determines whether 2 ProSe-enabled terminals are close to each other and reports a proximity state of the two ProSe-enabled terminals to the two ProSe-enabled terminals.

[0077] Hereinafter, the ProSe direct communication can indicate a D2D communication, and the ProSe direct discovery can indicate a D2D discovery.

[0078] Figure 4 A reference structure for the ProSe is shown.

[0079] Referring to Figure 4 , the reference structure for the ProSe includes a plurality of UEs, a ProSe application (ProSe APP) server, and a ProSe function having an E-UTRAN, an EPC, and a ProSe application.

[0080] The EPC is a representative example of the E-UTRAN. The EPC can include an MME, an S-GW, a P-GW, a policy and charging rules function (PCRF), and a home subscriber server (HSS).

[0081] The ProSe application server is a user of the ProSe for generating an application function. The ProSe application server can communicate with an application program in the terminal. The application program in the terminal can use a ProSe capability to generate an application function.

[0082] The ProSe function can include at least one of the following functions, but is not limited thereto.

[0083] - Interworking with a third party application via a reference point

[0084] - Authorization and configuration of a UE for discovery and direct communication

[0085] - Function to enable EPC-level ProSe discovery

[0086] - handling of ProSe related new subscriber data and data storage, also handling of ProSe identities

[0087] - security related functions

[0088] - providing control to EPC for policy related functions

[0089] - providing functions for charging (via EPC or outside of EPC, e.g. offline charging)

[0090] In the following, reference points and reference interfaces will be described in the reference structure for ProSe.

[0091] - PC1: Reference point between ProSe application in the terminal and ProSe application in the ProSe application server. PC1 is used to define the signaling requirements at application level.

[0092] - PC2: is the reference point between ProSe application server and ProSe function. PC2 is used to define the interaction between ProSe application server and ProSe function. Application data update in the ProSe database of the ProSe function can be an example of the interaction.

[0093] - PC3: is the reference point between terminal and ProSe function. PC3 is used to define the interaction between terminal and ProSe function. Configuration for ProSe discovery and communication can be an example of the interaction.

[0094] - PC4: is the reference point between EPC and ProSe function. PC4 is used to define the interaction between EPC and ProSe function. This interaction can show when a ProSe service for 1:1 communication or real-time session management or mobility management is authenticated.

[0095] - PC5: is the reference point for discovery, communication and relay between terminals and 1:1 communication using control / user plane.

[0096] - PC6: is the reference point for functions such as ProSe discovery between users included in different PLMNs.

[0097] - SGi: can be used for application data and application level control information exchange.

[0098] <ProSe Direct Communication (D2D Communication)>

[0099] ProSe Direct Communication is a communication mode in which two public safety terminals can perform direct communication over the PC5 interface. This communication mode can be supported in case of receiving service within the coverage of E-UTRAN or in case of leaving the coverage of E-UTRAN.

[0100] Figure 5 An example of an arrangement of terminals performing ProSe direct communication and a cell coverage is shown.

[0101] Referring to Figure 5 (a), UEs A and B can be disposed outside the cell coverage. Referring to Figure 5 (b), UE A can be disposed inside the cell coverage and UE B can be disposed outside the cell coverage. Referring to Figure 5 (c), both UEs A and B can be disposed inside the cell coverage. Referring to Figure 5 (d), UE A can be disposed inside the coverage of a first cell and UE B can be disposed inside the coverage of a second cell.

[0102] As described above, ProSe direct communication can be performed between terminals disposed at various locations.

[0103] Further, the following IDs can be used in ProSe direct communication.

[0104] Source Layer 2 ID: The source Layer 2 ID identifies the sender of a packet in a PC 5 interface.

[0105] Destination Layer 2 ID: The destination Layer 2 ID identifies the target of a packet in a PC 5 interface.

[0106] SA L1 ID: The SA L1 ID represents an ID in a scheduling assignment (SA) in a PC 5 interface.

[0107] Figure 6 A user plane protocol stack for ProSe direct communication is shown.

[0108] Referring to Figure 6 , a PC 5 interface includes a PDCH layer, an RLC layer, a MAC layer, and a PHY layer.

[0109] In ProSe direct communication, there can be no HARQ feedback. A MAC header can include a source Layer 2 ID and a destination Layer 2 ID.

[0110] <Radio resource assignment for ProSe direct communication>

[0111] For resource assignment for ProSe direct communication, a ProSe-enabled terminal can use the following two modes.

[0112] 1. Mode 1

[0113] Mode 1 is a mode of receiving scheduling of resources for ProSe direct communication from a base station. A terminal should be in an RRC CONNECTED state in order to transmit data according to mode 1. The terminal requests a transmission resource to the base station, and the base station schedules a resource for scheduling assignment and data transmission. The terminal can transmit a scheduling request to the base station and can transmit a buffer status report (ProSe BSR). The base station has data that the terminal will perform ProSe direct communication, and determines whether a resource for transmitting data is needed.

[0114] 2. Mode 2

[0115] Mode 2 is a mode of selecting a direct resource. A terminal directly selects a resource for ProSe direct communication from a resource pool. The resource pool can be configured by a network or can be predetermined.

[0116] In addition, when the terminal includes a serving cell, that is, when the terminal is in an RRC CONNECTED state with a base station or is set in a specific cell in an RRC IDLE state, the terminal is considered to be within the coverage of the base station.

[0117] If the terminal is set outside the coverage, only mode 2 can be applied. If the terminal is set within the coverage, mode 1 or mode 2 can be used according to the setting of the base station.

[0118] If there is no exceptional condition, the terminal can change the mode from mode 1 to mode 2 or from mode 2 to mode 1 only when the base station is configured.

[0119] <ProSe Direct Discovery (D2D Discovery)>

[0120] ProSe direct discovery indicates a process for discovery when a ProSe-enabled terminal discovers another proximate ProSe-enabled terminal, indicates D2D direct discovery, or D2D discovery. In this case, an E-UTRA wireless signal through a PC 4 interface can be used. Hereinafter, information for ProSe direct discovery indicates discovery information.

[0121] Figure 7 A PC 5 interface for D2D discovery is shown.

[0122] Referring to Figure 7 , the PC 5 interface includes a MAC layer, a PHY layer, and a ProSe protocol layer (is an upper layer). Permission for announcement and monitoring of discovery information are processed in the upper ProSe protocol. The content of the discovery information is transparent to an access layer (AS). The ProSe protocol only allows valid discovery information to be delivered to the AS for announcement.

[0123] The MAC layer receives discovery information from the upper layer ProSe protocol. The IP layer is not used to transmit discovery information. The MAC layer determines resources for announcing discovery information received from the upper layer. The MAC layer generates a protocol data unit (MAC PDU) and transmits it to the physical layer. No MAC header is added.

[0124] In order to announce discovery information, there are two types of resource assignment.

[0125] 1. Type 1

[0126] Type 1 is a method that is assigned such that resources for announcing discovery information are not terminal-specific and the base station provides a terminal with a resource pool configuration for announcing discovery information. The configuration can be included in a system information block (SIB) to be signaled in a broadcast scheme. Alternatively, the configuration can be included in a terminal-specific RRC message to be provided. Alternatively, the configuration can be signaled through broadcasting or signaled in a terminal-specific manner from a layer different from the RRC message.

[0127] A terminal selects a resource from the indicated resource pool to announce discovery information with the selected resource. A terminal can announce discovery information through a resource that is optionally selected during each discovery period.

[0128] 2. Type 2

[0129] Type 2 is a method that assigns resources for announcing discovery information in a terminal-specific manner. A terminal in an RRC_CONNECTED state can request resources for announcing discovery signals to a base station through an RRC signal. The base station can assign resources for announcing discovery signals as an RRC signal. Resources for monitoring discovery signals in a configured resource pool can be assigned in a terminal.

[0130] For a terminal in an RRC_IDLE state, the base station can report a type 1 resource pool for announcing discovery signals as an SIB. A terminal allowed for ProSe direct discovery announces discovery information using the type 1 resource pool in an RRC_IDLE state. Alternatively, the base station 2) reports that the base station supports ProSe direct discovery through an SIB, but can not provide resources for announcing discovery information. In this case, the terminal should enter an RRC_CONNECTED state in order to announce discovery information.

[0131] For a terminal in an RRC_CONNECTED state, the base station can configure whether to use a type 1 resource pool or a type 2 resource to announce discovery information through an RRC signal.

[0132] <vehicle-to-X (V2X) communication>

[0133] As described above, the D2D operation generally provides various advantages because it supports signal transmission and reception between devices adjacent to each other. For example, the D2D UE can perform data communication with high transmission rate and low latency. In addition, the D2D operation can disperse traffic concentrated at a base station, and if the UE performing the D2D operation acts as a relay, the D2D operation can extend the coverage of the base station. As an extension of the D2D communication, vehicle-related communication including signal transmission and reception between vehicles is specifically referred to as vehicle-to-X (V2X) communication.

[0134] In one example, the "X" in V2X denotes a pedestrian (communication between a vehicle and a device carried by a person (e.g., a handheld UE carried by a pedestrian, a cyclist, a driver, or a passenger), in which case the V2X can be denoted by V2P), a vehicle (communication between vehicles, V2V), infrastructure / network (communication between a vehicle and a roadside unit (RSU) / network, in which the RSU is a traffic infrastructure entity, e.g., an entity implementing a speed notification in an eNB or a fixed UE, V2I / N). In addition, in one example, for the convenience of describing the proposed method, a device carried by a pedestrian (or a person) (related to V2P communication) is referred to as a "P-UE", and a device installed in a vehicle (related to V2X communication) is referred to as a "V-UE". In addition, in one example, the term "entity" in this document can be interpreted as a P-UE, a V-UE, or an RSU ( / network / infrastructure).

[0135] The V2X UE can perform message (or channel) transmission on a pre-defined (or signaled) resource pool. Here, the resource pool can refer to a pre-defined resource that enables the UE to perform a V2X operation (or is capable of performing a V2X operation). At this time, the resource pool can also be defined in terms of time-frequency.

[0136] In addition, various types of V2X transmission resource pools can be defined.

[0137] Figure 6 Types of V2X transmission resource pools are shown.

[0138] Referring to Figure 6 (a), the V2X transmission resource pool #A can be a resource pool that allows only (partial) sensing. In the V2X transmission resource pool #A, the UE must select a V2X transmission resource after performing (partial) sensing, and random selection can not be allowed. As shown in (a) of Figure 6 The V2X transmission resource selected through (partial) sensing is maintained semi-statically at a predetermined interval.

[0139] In order for the UE to perform V2X message transmission on the V2X transmission resource pool #A, the base station can configure the (partial) sensing operation to be (partially) performed (based on scheduling assignment decoding / energy measurement). This can be interpreted as not allowing "random selection" of transmission resources on the V2X transmission resource pool #A, but can be interpreted as (allowing) performing (only) (partial) sensing-based transmission resource selection. This configuration can be set by the base station.

[0140] Referring to Figure 6 (b), the V2X transmission resource pool #B can be a resource pool allowing only random selection. In the V2X transmission resource pool #B, the UE can not perform (partial) sensing, but randomly select a V2X transmission resource from a selection window. In one example, unlike the resource pool allowing only (partial) sensing, the resource pool allowing only random selection can be set (or signaled) such that the selected resource can not be semi-statically reserved.

[0141] The base station can set not to perform the (partial) sensing operation (based on scheduling assignment decoding / energy measurement) so that the UE can perform the V2X message transmission operation on the V2X transmission resource pool #B. This can be interpreted as performing ( / allowing) only "random selection" of transmission resources on the V2X transmission resource pool #B and / or not allowing (partial) sensing-based transmission resource selection.

[0142] In addition, although Figure 6 is not shown in the above, there can be a resource pool allowing both (partial) sensing and random selection. The base station can inform (the UE) that in such a resource pool, either (partial) sensing or random selection can be used to select a V2X resource.

[0143] Figure 7 A V2X transmission resource (re)selection ( / reservation) method according to a partial sensing operation is shown.

[0144] Referring to Figure 7 , the UE (hereinafter, denoted as a P-UE) can determine (or trigger) (re)selection (or reservation) of a resource for V2X signal transmission (according to whether a predetermined condition is satisfied). For example, it is assumed that transmission resource (re)selection (or reservation) is determined or triggered at subframe #m. In this case, the UE can (re)select (or reserve) a resource for V2X signal transmission from a subframe period ranging from subframe #m+T1 to #m+T2. Hereinafter, the subframe period ranging from subframe #m+T1 to #m+T2 is referred to as a selection window. For example, the selection window can include 100 consecutive subframes.

[0145] The UE can select at least Y subframes as candidate resources within the selection window. In other words, the UE can have to consider at least Y subframes as candidate resources within the selection window. Y can be a predetermined value or can be determined by the network. It should be noted that how to select Y subframes within the selection window can be affected by the problem of the implementing UE. In other words, assuming the value of Y is 50. Then which 50 subframes out of 100 subframes including the selection window can be selected by the UE for selection. For example, the UE can select 50 subframes with odd subframe numbers out of 100 subframes. Likewise, the UE can select 50 subframes with even subframe numbers. Similarly, 50 subframes can be selected by any rule.

[0146] Further, in order to (re)select (or reserve) a specific subframe (e.g., subframe #N (SF #N)) among Y subframes as a V2X transmission subframe capable of transmitting a V2X signal, the UE can have to link to the subframe #N or sense at least one associated subframe. The defined (entire) subframe period for sensing is referred to as a sensing window, which can include, for example, 1000 subframes. In other words, the sensing window can span 1000 milliseconds or 1 second. For example, the UE can sense subframes corresponding to subframe #N - 100*k (where k can be a set of elements in the range [1, 10] and can be pre-set or determined by the network) within the sensing window.

[0147] Figure 7 The case where the value of k is {1, 3, 5, 7, 10} is shown. In other words, the UE can sense subframes #N - 1000, #N - 700, #N - 500, #N - 300, and #N - 100, infer / determine whether subframe #N is used by other V2X UEs (and / or whether there is a relatively high interference (or an interference greater than a pre-set (or signaled) threshold) on subframe #N), and (finally) select subframe #N according to the result. Since P-UEs are more sensitive to battery consumption than V-UEs, not all subframes within the sensing window are sensed, but only a part of them, i.e., partial sensing is performed.

[0148] In one example, at the time of V2V communication, (A) a transmission resource selection procedure (or method) based on a sensing operation and / or (B) a V2V resource pool configuration (or signaling) procedure (or method) can be described as follows.

[0149] (A) Transmission resource selection procedure (or method) based on a sensing operation

[0150] Step 1: In the case of PSSCH resource (re)selection, if all PSCCH / PSSCH transmissions have the same priority, all resources can be first considered as selectable resources.

[0151] Step 2: In addition, the UE can exclude resources based on at least one of SA decoding and additional conditions.

[0152] The UE selects V2X transmission resources after excluding specific resources based on the scheduling assignment and additional conditions. At this time, if the scheduling assignment and data associated therewith are transmitted from the same subframe, a method of excluding resources based on PSSCH-based DM-RS reception power can be supported. In other words, resources designated or reserved by the decoded scheduling assignment and resources for which PSSCH reference signal reception power (RSRP) received from data resources associated with the scheduling assignment exceeds a threshold value are excluded. More specifically, the PSSCH RSRP can be defined as a linear average of power distribution on resource elements (REs) carrying DM-RS associated with the PSSCH within physical resource blocks (PRBs) indicated by the PSCCH. The PSSCH RSRP can be measured with respect to an antenna connection unit of the UE. The scheduling assignment can include a 3-bit PPPP field.

[0153] The threshold value can be expressed as a function of priority information. For example, the threshold value can depend on priority information of a transport block and priority information of the decoded scheduling assignment. The threshold value can be set to a value from -128 dBm to 0 dBm in units of 2 dBm. A total of 64 threshold values can be predefined.

[0154] It can be assumed that the UE decodes the scheduling assignment at subframe #m+c belonging to the sensing period, and the scheduling assignment reserves the same frequency resources at subframe #m+d+P*i. As described above, P can be a fixed value of 100. i can be selected from a range of [0, 1, …, 10], which can be set by the network in a carrier-specific manner or predetermined. If i = 0, it indicates that the frequency resources are not expected to be reserved. i can be set by a 10-bit bitmap or by a four-bit field within the scheduling assignment.

[0155] If a candidate semi-static resource X collides with a resource Y reserved by another UE through a scheduling assignment at a period P*I and the exclusion condition is satisfied, the UE can exclude the candidate semi-static resource X. I denotes a value of i signaled through the scheduling assignment.

[0156] If the remaining resources after excluding resources through scheduling assignment decoding, sensing processing, etc. are less than 20% of the total resources within a selection window, the UE increases the threshold value (for example, by 3 dB) and performs the process of excluding resources again, where this process can be performed until the remaining resources exceed 20% of the total resources within the selection window. The total resources within the selection window indicate resources that the UE must consider as possible candidate resources.

[0157] Further, during the process of selecting V2X transmission resources after excluding specific resources, if the counter of the UE reaches 0, the current resource can be maintained with a probability of p, and the counter can be reset. In other words, the resource can be reselected with a probability of 1-p.

[0158] The carrier-specific parameter p can be pre-set and take values from [0, 0.2, 0.4, 0.6, 0.8].

[0159] The UE measures the remaining PSSCH resources except for the specific resources, sorts the remaining PSSCH resources according to the total received energy, and selects a subset. The subset can be a set of candidate resources with the lowest received energy. The size of the subset can be aggregated to be 20% of the total resources within the selection window.

[0160] The UE can randomly select one resource from the subset.

[0161] When only one transport block is transmitted from one subframe, the UE can select M consecutive sub-channels, and the average of the energies measured at the respective sub-channels can become the energy measurement value of the respective resources.

[0162] Further, when a transport block (TB) is transmitted from two subframes, the following resource selection can be supported.

[0163] First, one resource using the mechanism defined for the case of transmitting a TB from one subframe can be selected.

[0164] And the other resource can be randomly selected under the following conditions. The selected resource should neither be the same subframe as the first resource nor be the subframe excluded from resource selection. Further, the SCI should be able to indicate the time gap between the two selected resources.

[0165] If no resource meets the condition for selecting the second resource, the TB can be transmitted using only the first resource.

[0166] Step 3: The UE can select a V2X transmission resource among the resources that are not excluded.

[0167] (B) V2V resource pool configuration (signaling) procedure (or method)

[0168] First, if the resources are configured such that the SA and data are always transmitted from the same subframe, it is expected that the UE will not transmit a hybrid PSCCH from different subframes.

[0169] In a pool in which the UE is configured to always transmit the SA and data from the RB adjacent to the same subframe, among the sub-channels selected for data transmission, the sub-channel with the lowest index can be used for SA transmission.

[0170] In case the UE is configured to transmit SA and data from a pool of RBs that are not adjacent to the same subframe, the number of SA candidate resources in the SA pool can be the same as the number of subchannels in the associated data pool. Among the SA resources selected for data transmission, the SA resource associated with the lowest index can be used for SA transmission.

[0171] The UE can perform resource selection / reselection at TTI m (≥ n). Here, TTI m can represent the reception time of the TB.

[0172] Regarding resource reselection, the UE must consider candidate resources available in the period of [m+T1, m+T2]. Here, T1 is a UE-specific parameter, T1≤[4]. In addition, T2 can be a UE-specific parameter, and 20≤T2≤100. Here, the selected T2 must satisfy the delay requirement.

[0173] In addition, the sensing window can change with [m-a, m-b). (Here, a=b+1000 and b=1).

[0174] In case the UE is configured to always transmit SA and data from a pool of RBs that are adjacent to the same subframe, the resource pool can include one or more subchannels in the frequency domain. Here, a subchannel can consist of a set of RBs adjacent to the same subframe. In addition, the size of the subchannel in the resource pool can be set by the base station (e.g., eNB) or be a predetermined value. Here, the candidate resources of the subchannel can be selected from the subset {5, 6, 10, 15, 20, 25, 50, 75, 100}.

[0175] In case the UE is configured to transmit SA and data from a pool of RBs that are not adjacent to the same subframe, the resource pool can include one or more subchannels in the frequency domain. Here, a subchannel can consist of a set of RBs adjacent to the same subframe. In addition, the size of the subchannel in the resource pool can be set by the base station (e.g., eNB) or be a predetermined value. Here, the number of subchannels can not exceed 200, and the minimum candidate size can not be less than 4.

[0176] The UE can select an integer number of adjacent subchannels for transmission, and can not decode more than 100 RBs in one subframe. In addition, the UE can not decode more than 10 PSSCHs in one subframe.

[0177] The SA pool can overlap with the associated data pool. In addition, the SA pool can also overlap with the non-associated data pool.

[0178] In case the UE is configured to transmit SA and data from a pool of RBs that are adjacent to the same subframe, the resource pool can consist of N consecutive PRBs. Here, N can be the same as (size of subchannel x number of subchannels).

[0179] A V2V pool can be defined such that the bitmap is repeatedly mapped onto all subframes except the skipped SLSS subframes. Here, the length of the bitmap can be 16, 20, or 100. The bitmap can define which subframes are allowed for V2V SA / data transmission and / or reception with respect to the pool.

[0180] Further, if a resource reselection is triggered, the UE can reselect resources related to all transmissions corresponding to one TB. Here, the SA can schedule transmissions corresponding to one TB. In addition, the PSSCH-RSRP measured in the TTI occurring before the reception of the successfully decoded associated SA can be applied. Here, the number of transmissions for one TB can be 1 or 2. In addition, each SA can indicate time / frequency resources for all data transmissions corresponding to the same TB.

[0181] Hereinafter, the present application will be described.

[0182] The proposed method described below addresses the case where a V2X UE (re)reserves (or selects) its own resources related to V2X message transmission. In this case, the present application provides (A) a method to efficiently define the boundaries in the time domain where the sensing operation is performed, and (B) a method to efficiently support the retransmission (RE-TX) of V2X messages that are omitted (or stopped) while performing the sensing operation. Here, as one example, the word "sensing" in this document can be interpreted as an RSRP measurement operation (e.g., S-RSRP) with respect to a (predefined or signaled) reference signal (RS) (on PSSCH scheduled by successfully decoded PSCCH) and / or an energy measurement operation (e.g., S-RSSI) with respect to a (sub)channel, or a decoding operation with respect to a predefined (signaled) channel (e.g., physical sidelink control channel (PSCCH)). In one example, in the present application, the word "duration" (and / or "period") can be extended to be interpreted as "range (or window)".

[0183] [Proposal Rule #1] The boundary (or location) of the time region (or period) in which the sensing operation is performed (for each V2X UE) can have the form (or characteristic) of a "UE-specific (time) boundary". Here, in one example, the boundary (or location) of the time region (or period) in which the (resource (re)reservation (or selection) related) sensing operation of a specific V2X UE is performed can be defined as a "V2X message TX time (SF#K)" (of the corresponding V2X UE). When this rule is applied, in one example, the V2X UE performs the sensing operation at the remaining (resource) time points other than the (resource) time points at which the V2X UE (actually) performs the V2X message TX operation on the resource period ranging from "SF#(K-D) to SF#K" (or the resource period ranging from SF#(K-1-D) to SF#(K-1)) (where "D" denotes a pre-defined (or signaled) "sensing duration") and then (re)reserves (or selects) its own resource related to the V2X message TX. Here, as another example, the V2X UE skips (or stops) the (last) transmission of its V2X message at "SF#K" (if necessary) according to the pre-defined rule, performs the sensing (measurement) up to the (SF#K) resource of the V2X UE (or the previously reserved (or selected) resource), and immediately performs the optimal (re)reservation (or selection) of the resource (and / or immediately transmits the V2X message using the (re)reserved (or selected) resource). Here, as another example, in the case where the V2X UE performs the sensing operation in the resource period, the V2X UE can perform the resource (re)reservation (or selection) (based on the sensing result) on the resource period ranging from "SF#(K+1) to SF#(K+1+R)" (or the resource period ranging from SF#K to SF#(K+R)) where "R" denotes a pre-defined (or signaled) "TX resource (re)selection duration".

[0184] For the convenience of understanding, the boundary of the time region in which the sensing operation is performed (for each V2X UE) according to Proposal Rule #1 can take the form (or characteristic) of a "UE-specific (time) boundary" and can be described with reference to the related drawings as follows.

[0185] Figure 8 is a flowchart illustrating a method of performing V2X communication based on a UE-specific sensing period according to an embodiment of the present application.

[0186] Referring to Figure 8, the UE can select a resource for performing V2X communication by performing sensing during a UE-specific sensing period S810. Here, the UE performs sensing and selects a resource for performing V2X communication during a specific period (i.e., a UE-specific sensing period (or UE-specific sensing window)) can be described from the following perspectives: (A) the period (i.e., the sensing window) in which the UE performs sensing is UE-specific; and (B) the period in which the UE performs sensing is 1 second (i.e., a period corresponding to 1000 subframes, in which each subframe occupies a period of 1 ms) and this 1 second corresponds to the length of an SPS period (or a maximum (possible) resource reservation period) (i.e., [N-1000, N-1]).

[0187] (A) First, the selection of a resource for performing V2X communication can be described from the perspective that the period (i.e., the sensing window) in which the UE performs sensing is UE-specific as follows.

[0188] As described above, the UE can select a resource for performing V2X communication by performing sensing, in which the UE can have different periods (i.e., UE-specific sensing periods) for performing sensing. Here, having a UE-specific sensing period does not mean that the sensing time itself is different for each UE, but rather that the location of the sensing period (i.e., the sensing window) is different for each UE.

[0189] In other words, the boundary of the time region in which the sensing operation is performed (for each V2X UE) can have the form (or characteristic) of a "UE-specific (time) boundary". In other words, the energy measurement window is UE-specific (in other words, in the case of an "[N-A, N-B]" energy sensing (or measurement) period, the value of N is UE-specific), which will be described below with reference to the relevant drawings.

[0190] Figure 9 An example of a UE-specific sensing window is shown.

[0191] Referring to Figure 9 , each UE (i.e., "UE 1" and "UE 2") has a sensing window that spans a different period of time, and the sensing window can be defined for each UE at different times.

[0192] More specifically, if the upper layer of the UE makes a request at a specific subframe (hereinafter, subframe N), the UE can determine a set of resources that must be transmitted to the upper layer together with the V2X message transmission (e.g., PSSCH transmission).

[0193] Thereafter, the UE monitors during a certain sensing period (excluding subframes in which the UE performs transmission) (e.g., subframes N-1000, N-999, N-998, …, up to N-1). Here, the UE monitors the certain sensing period (e.g., subframes N-1000, N-999, …, up to N-1) with respect to subframe N determined by the upper layer of the UE itself means that a sensing window in which the UE performs monitoring is determined by the corresponding UE.

[0194] For the sake of description Figure 9 of an example, in the case of the UE 1, it can be assumed that the upper layer of the UE 1 generates a request at N UE1 -1. In this case, the sensing period (i.e., sensing window) of the UE 1 spans subframes N_UE1-1000, N_UE1-999, …, up to N_UE1-1, and in this case, the sensing window is UE 1-specific, as shown in FIG. 10. Figure 9 In the same manner, in the case of the UE 2, it can be assumed that the upper layer of the UE 2 generates a request at N _UE2 -1. In this case, the sensing period (i.e., sensing window) of the UE 2 spans subframes N_UE2-1000, N_UE2-999, …, up to N_UE2-1, and in this case, the sensing window is UE 2-specific, as shown in FIG. 11. Figure 9

[0195] Thereafter, the UE can select a resource for performing V2X communication based on the S-RSSI measured in the above-described subframes (i.e., N-1000, N-999, N-998, …, N-1) and the decoded PSCCH. Here, a specific example in which the UE selects a resource for performing V2X communication is the same as described above.

[0196] (B) The following description is given based on the perspective that a period in which the UE performs sensing is 1 second (i.e., a period of 1000 subframes) and this 1 second corresponds to a maximum semi-persistent scheduling (SPS) (or maximum (possible) resource reservation period) length (i.e., [N-1000, N-1]).

[0197] ​In one example, if a V2X UE (re)reserves (or selects) a resource for (V2X message TX related) resource (re)reservation (or selection) using sensing results obtained by monitoring a period including "SF#(N-A), SF#(N-A+1),..., SF#(N-B) (or SC period#(N-A), SC period#(N-A+1),..., SC period#(N-B)) (A > B (e.g., considering processing time for resource (re)selection, the "B" value can be a positive integer greater than "0"))" in a triggered "SF#N" (or "SC period#N"), the "monitoring window size (i.e., "(A-B)")" can be set as a maximum value of a time at which resource (re)reservation (or selection) occurs (e.g., which can be interpreted as an interval between reserved resources). In one example, the corresponding V2X UE selects its transmission resource from a period of "SF#(N+C), SF#(N+C+1),..., SF#(N+D) (or SC period#(N+C), SC period#(N+C+1),..., SC period#(N+D)) (D > C (e.g., considering processing time related to PSCCH / PSSCH generation, the "C" value can be a positive integer greater than "0"))". As a specific example, if resource (re)reservation (or selection) is performed every 500 ms, "(A-B)" can become 400 ms (here, for example, "400 ms" can be interpreted as a remainder after subtracting one predefined "SC period (100 ms)" from "500 ms"). In addition, in one example, the corresponding "400 ms" period can be interpreted as a period ranging from "SF#(N-500MS)" to "SF#(N-100MS)". In other words, the "sensing duration" (or "(A-B)") can become a function of a predefined (or pre-set) "resource (re)reservation (or selection) period" (or it can be interpreted as performing a "sensing operation during a period derived from the "resource (re)reservation (or selection) period"). In summary, in one example, since the same resource will be selected (or used) until a "resource (re)reservation (or selection)" is performed, it can be meaningful to sense a resource just before the current ("resource (re)reservation (or selection)") period, without the need to sense a resource before a time at which "resource (re)reservation (or selection)" is bound to occur. Here, in one example, this rule can be particularly useful when the SA / data (pool) is implemented as a "TDM structure".

[0198] As another example, assume that a V2X UE performs an "SA (or PSCCH)" transmission related to a "data (PSSCH)" transmission associated with "SF#(N+D)" (e.g., D > C) in "SF#(N+C)". Here, in one example, "SF#N" can be assumed (or interpreted) as a time to perform a "resource (re)selection" operation (according to a pre-defined rule (or signaling)), and / or a period ranging from "SF#(N-A)" to "SF#(N-B)" (e.g., A > B > 0) can be assumed (or interpreted) as a zone to provide sensing results (or perform sensing) to be referred to when performing an "SA (or PSCCH)" ("SF#(N+C)") and / or data (PSSCH) ("SF#(N+D)") resource (re)selection operation. Here, in one example, when performing another TB related "potential data (PSSCH)" transmission on "SF#(N+E)" in "SF#(N+D)" (e.g., D < E), the V2X UE can indicate an intention to reuse a "(frequency) resource" (for a "data (PSSCH)" transmission on "SF#(N+D)") through a (pre-defined (or signaled)) channel (e.g., an "SA (or PSCCH)" ("SF#(N+C)") (or through a "data (PSSCH)"). Here, in one example, a field to (further) transmit an "(E-C)" value (or an "(E-D)" value or an "E" value) can be newly defined on an "SA (or PSCCH)" ("SF#(N+C)") for an application purpose. Here, in one example, the "(E-C)" value (E_CGAP) (or the "(E-D)" value (E_DGAP)) (or the "E" value (E_GAP)) can be interpreted as an interval between an "SA (or PSCCH)" ("SF#(N+C)") transmission time point and a "next TB" related (potential) data (PSSCH) transmission time point (or an interval between an "SA (or PSCCH)" ("SF#(N+C)") scheduled "data (PSSCH)" transmission time point and a "next TB" related (potential) "data (PSSCH) transmission time point) or a "V2X message generation (or TX) periodicity". Here, in one example, a "sensing window size" (e.g., "(B-A)") of a V2X UE can be determined (or configured) according to the following (partial) rules. Here, in one example, an "E-CGAP" (or E_DGAP or E_GAP) related (maximum (or minimum)) value can be set (or signaled) as a "single value" or "multiple values" (from a network or a (serving) base station in a "UE common" or "UE specific" manner), or can be considered (or assumed) to be the same as a (maximum (or minimum)) "message generation (or TX) periodicity" of a V2X UE.

[0199] (Rule #A) (A) "E_CGAP" (or E_DGAP or E_GAP) related (maximum (or minimum)) value and / or (B) (maximum (or minimum)) "message generation (or TX) periodicity" value can be considered (or determined) as a "sensing window size". As another example, a "sensing window size" can be set as a pre-defined (or signaled) (specific) value regardless of (A) "E_CGAP" (or E_DGAP or E_GAP) related (maximum (or minimum)) value and / or (B) (maximum (or minimum)) "message generation (or TX) periodicity" value. Here, in one example, if the above-mentioned rule is applied, a (relatively) small "sensing window size" can be used to perform a sensing operation (which can be interpreted as a kind of "partial (or limited) area sensing") even when a V2X UE performs a "V2X message" transmission with a (relatively) long "message generation (or TX) periodicity". In one example, in Rule #A, a "sensing window size" can be set in a "UE-common" (or "UE-specific") manner.

[0200] (Rule #B) A pre-defined (or signaled) "(V2X) SPS periodicity" value can be considered (or determined) as a "sensing window size". Here, in one example (applying a corresponding rule), if multiple different "SPS configurations (or processes)" are set (or signaled) with "SPS periodicity", it can be interpreted (or considered) as applying different "sensing window sizes" to each "SPS configuration (or process)". As another example, when multiple "SPS configurations (or processes or (transmission) operations)" with different "(V2X) SPS periodicity" are set (or signaled or allowed), a maximum (or minimum) value among the corresponding "(V2X) SPS periodicity" is determined (or derived) as a "(common) sensing window size", which can also be commonly applied to the multiple "SPS configurations (or processes or (transmission) operations). In one example, in Rule #B, a "sensing window size" can be set in a "UE-specific" (or "UE-common") manner.

[0201] Here, the SPS period can be determined as in the resource reservation field of the SCI format 1 of Table 1 as follows.

[0202]

[0203]

[0204] Here, a receiving UE (RX UE) can figure out a resource reservation period of a final transmitting UE (TX UE) based on a value that can be signaled to a resource reservation field of an SCI format shown in Table 1.

[0205] At this time, the RX UE can determine a "resource reservation period candidate value" that can be configured by the TX UE by multiplying the value of the resource reservation field by 100. For example, if the value of the resource reservation field is "0001", the resource reservation period can be 100 ms, and if the value of the resource reservation field is "0010", the resource reservation period can be 200 ms. In the same manner, if the value of the resource reservation field is "1010", the resource reservation period can be 1000 ms.

[0206] In summary, the RX UE can figure out that the "resource reservation period candidate" value that can be set by the TX UE by multiplying the value of the resource reservation field by 100 is "20, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 ms", and thus, the maximum value of the SPS period can have a value of 1000 ms (i.e., 1 s).

[0207] As described above, the period in which the UE performs sensing (i.e., the sensing window of the UE) can have a maximum semi-persistent scheduling (SPS) period (or a maximum (possible) resource reservation period), and thus, the period in which the UE performs sensing (i.e., the sensing window) can be 1000 ms (i.e., 1 s as the maximum value of the SPS period).

[0208] Referring again to Figure 8 , the UE can perform V2X communication using the selected resources S820. As described above (or below), the UE can select subframes within the selected window based on the sensing result obtained by performing sensing during the UE-specific sensing period, determine transmission reservation resources based on the selected subframes, and perform V2X communication on the reserved resources. Since the specific example in which the UE performs V2X communication based on the selected resources is the same as described above (or below), the specific details will be omitted.

[0209] In addition, an end-to-end delay must be considered for V2X communication. In other words, when the UE transmits a packet generated in the upper layer, not only the time required to transmit the packet generated in the upper layer down to the physical layer must be considered, but also the time in which the RX UE receives the packet and transmits the received packet up to the upper layer of the RX UE must be considered. Therefore, how to configure the period in which the UE selects resources for performing V2X message transmission (i.e., the selection window in which transmission resources are selected) becomes important. Hereinafter, a method of configuring a selection window will be described with reference to the related drawings.

[0210] Figure 10 is a flowchart illustrating a method of configuring a selection window according to an embodiment of the present application.

[0211] The UE can select a resource (or subframe, hereinafter, for convenience of description, resource and subframe can be used interchangeably) for performing V2X communication within a range satisfying a delay requirement S1010. At this time, the UE can select a resource by configuring a selection window within a range satisfying a delay requirement, can perform V2X communication in units of a plurality of subchannels, and can select a resource for performing V2X communication based on a sensing result obtained by performing in units of a subchannel having a size corresponding to the size of the plurality of subchannels. The sensing region in which sensing is performed can have a size corresponding to the plurality of subchannels. In addition, the UE can also perform sensing using an energy measurement average value of a subchannel belonging to the plurality of subchannels.

[0212] In summary, the UE can not only select a resource by configuring a selection window within a range satisfying a delay requirement, but also perform sensing in units of a plurality of subchannels when performing V2X communication in units of a plurality of subchannels. Specific examples of performing sensing in units of a plurality of subchannels when performing V2X communication in units of a plurality of subchannels will be described later.

[0213] Hereinafter, an example in which the UE selects a transmission resource within a range satisfying a delay requirement will be mainly described.

[0214] The UE can select a transmission resource (or subframe) within a range satisfying a delay requirement (and configure a selection window). Here, the UE can assume that a set of adjacent subchannels (e.g., L subCH ) in a V2X resource pool (e.g., a PSSCH resource pool) belonging to a specific period (e.g., [n+T1, n+T2]) corresponds to one candidate subframe (resource). At this time, the selection of information (e.g., T1 and T2) for determining a specific period can depend on how the UE is implemented. T1 can have a value less than or equal to 4, and T2 can have a value not less than 20 and not more than 100. Specifically, the selection of T2 by the UE must satisfy a delay requirement.

[0215] For example, the “sensing duration (D)” and / or the “TX resource (re)selection duration (R)” can be (implicitly) assumed to be the same as (and / or according to) the “V2X message generation period” (and / or the “(service) delay requirement”) (and / or can be assumed differently (or changed) according to the “V2X message generation period” (and / or the “(service) delay requirement” and / or the “(V2X message (or TB)) or “PPPP” (e.g., when (partial) different “PPPP” values are set (or allowed) for respective V2X messages (or TBs) with different “(service) delay requirements”)), and / or assumed to be a pre-defined (or signaled) specific value (e.g., a corresponding rule can be interpreted as the “TX resource (re)selection duration (R)” is configured to meet the “(service) delay requirement”). Here, in one example, (in particular, in the latter case), the “sensing duration (D)” and the “TX resource (re)selection duration (R)” can (always) be set (or considered) to have the same value, or can be defined to have independent (or different) values. As another example, the boundary of the time region in which the (resource (re)reservation (or selection) related) sensing operation of a specific V2X UE is performed can be defined as the “V2X message generation time” (of the corresponding V2X UE). As another example, when considering the “(TX) processing time” (of the V2X UE), a time point obtained by adding (or subtracting) a pre-defined (or signaled) offset to (or from) the above-mentioned “boundary criterion of the time region in which the (resource (re)reservation (or selection) related) sensing operation is performed” (e.g., the “V2X message TX time” and the “V2X message generation time”) can become the final “boundary criterion of the time region in which the sensing operation is performed”. As a specific example, a V2X UE performs a sensing operation in a resource period ranging from “SF#(K-D-S) to SF#(K-S)” (or in a resource period ranging from SF#(K-1-D-S) to SF#(K-1-S)) (where “D” and “S” denote a pre-defined (or signaled) “sensing duration” and a “(TX) processing time” (of the V2X UE), respectively, in one example) except for a (resource) time point at which the V2X message TX operation of the V2X UE itself is (actually) performed, and then (re)reserves (or selects) a V2X message TX related resource of the V2X UE itself in a resource period ranging from “SF#(K+1) to SF#(K+1+R)” (or from SF#K to SF#(K+R)) (where “R” denotes a pre-defined (or signaled) “TX resource (re)selection duration”, in one example).

[0216] Thereafter, the UE can perform V2X communication using the selected resource S1020. Here, as described above, the selected resource can indicate a resource determined based on a selection window configured within a range satisfying the delay requirement (in other words, a resource on a selection window satisfying the delay requirement). Also, as described above (or below), the UE can select a subframe within the selection window based on a sensing result obtained by performing sensing in a UE-specific sensing period, determine a transmission reservation resource based on the selected subframe, and perform V2X communication on the reserved resource. Since a specific example in which the UE performs V2X communication based on the selected resource is the same as described above (or below), specific details will be omitted.

[0217] Figure 11 and Figure 12 Proposal Rule #1 is shown.

[0218] Figure 11 and Figure 12 It is assumed that a V2X message is periodically generated (e.g., "100 ms") for each V2X UE. Also, in one example, it is assumed that a "sensing duration (or TX resource (re)selection duration)" and a "V2X message TX related reception number" are set to "100 ms" and "1", respectively. In an additional example, Figure 11 A case in which a V2X UE performs a sensing operation on a resource period ranging from SF#(K-100) to SF#K except for a (resource) time point at which the V2X UE actually performs a V2X message TX operation, and then re-reserves (or selects) a V2X message TX related resource on a resource period ranging from SF#(K+1) to SF#(K+101) using a corresponding sensing result is shown. Figure 12 A case in which a V2X UE performs a sensing operation on a resource period ranging from SF#(K-1) to SF#(K-101) except for a (resource) time point at which the V2X UE actually performs a V2X message TX operation, and then re-reserves (or selects) a V2X message TX related resource on a resource period ranging from SF#(K+1) to SF#(K+101) using a corresponding sensing result is shown. In one example, in Figure 11 and Figure 12 In the above, the "transmission of the (N+1)th V2X message" is performed by reselecting a resource (e.g., SF#(K+Z+100)).

[0219] Figure 13 and Figure 14 A case in which it is determined to re-reserve (or select) a resource and immediately perform a V2X message using the re-reserved (or selected) resource is shown.

[0220] More specifically,Figure 13 and Figure 14 respectively show the same cases as in Figure 11 and Figure 12 , the V2X UE skips (or stops) the transmission of the V2X message on SF#K, senses (or measures) up to the resource (SF#K) which has been used (or previously reserved (or selected)) by the V2X UE, and determines the best re-reserved (or selected) resource and immediately performs the transmission of the V2X message using the re-reserved (or selected) resource. Here, in one example, the transmission of the (N+1)th V2X message is performed by re-selecting the resource (e.g., SF#(K+Z+100)).

[0221] [Proposal Rule #2] In order to sense (or measure) the resource used (or previously reserved (or selected)) in (Proposal Rule #1), the retransmission of the skipped (or stopped) V2X message (e.g., in Figure 13 and Figure 14 , the (Nth V2X message transmission) can be retransmitted according to the following (partial) rules.

[0222] (Example #2-1) If the (service) latency requirement condition can be met when the skipped (or stopped) V2X message is retransmitted by the re-reserved (or selected) resource after performing the resource re-reservation (or selection) according to the “sensing (measurement) result” and the “predefined (re-reservation (or selection) criteria (or rules)” (without considering the retransmission of the skipped (or stopped) V2X message), it can be defined so that the retransmission of the skipped (or stopped) V2X message is performed (using the corresponding re-reserved (or selected) resource) (immediately). On the other hand, if the (service) latency requirement is not met when the retransmission of the skipped (or stopped) V2X message is performed by the re-reserved (or selected) resource, it can be defined so that the retransmission of the skipped (or stopped) V2X message (using the corresponding re-reserved (or selected) resource) is not performed. As a specific example, in Figure 13 and Figure 14 , since the (service) latency requirement (100 ms) can be met when the retransmission of the skipped (or stopped) V2X message (SF#K) is performed by the re-reserved (or selected) resource (SF#(K+Z)), the retransmission of the skipped (or stopped) V2X message is performed (by the re-reserved (or selected) resource (SF#(K+Z)) immediately.

[0223] (Example #2-2) can be defined such that a V2X UE performs resource re-reservation (or selection) considering only “candidate resources” allowing retransmission of a “skipped (or stopped) V2X message” satisfying a “(service) latency requirement”. When this rule is applied, for example, a V2X UE finally re-reserves (or selects) the best resource satisfying a pre-defined (re-reservation (or selection)) criterion (or rule) among corresponding “candidate resources”. Here, in one example, by the resource corresponding to the final re-reservation (or selection), not only retransmission of a “skipped (or stopped) V2X message” is performed, but also transmission of a V2X message (to be generated) thereafter is performed. The above rule can guarantee retransmission of a “skipped (or stopped) V2X message” with high probability. In order to guarantee the above operation, a zone for a “TX resource (re)selection duration (R)” can be reduced. By this scheme, only those resources close to a current (skipped (or stopped)) transmission time can be selected, so that a (skipped (or stopped)) V2X message is re-sent while satisfying a “(service) latency requirement”. In this case, a zone for a “sensing duration (D)” can also be (correspondingly) reduced.

[0224] (Example #2-3) can be defined such that a resource (or pool) for retransmission of a (previously) “skipped (or stopped) V2X message” is (only) configured (or signaled) independently (or additionally), or can be additionally selected according to a (part of) rule (or criterion) pre-defined (or signaled) below for retransmission of a “skipped (or stopped) V2X message”. In one example, the corresponding resource additionally selected (in the latter case) can be used only temporarily (or limitatively) for retransmission of a (previously) “skipped (or stopped) V2X message”.

[0225] (Example #2-3-1) can be defined such that a V2X UE selects additional (retransmission) resources considering only “candidate resources” allowing retransmission of a “skipped (or stopped) V2X message” that meets a “(service) latency requirement”. In another example, within a pre-defined (or signaled) “TX resource (re)selection duration”, retransmission of a “skipped (or stopped) V2X message” is not performed, but resource re-reservation (or selection) for transmission of a “V2X message (to be generated) thereafter” can be performed. Here, resources re-reserved (or selected) for this purpose can be excluded from candidate resources for retransmission of a “skipped (or stopped) V2X message” (although the re-reserved (or selected) resources can meet a “(service) latency requirement” when retransmission of a “skipped (or stopped) V2X message” is performed). In other words, compared to resources for retransmission of a “skipped (or stopped) V2X message”, resources for transmission of a “V2X message (to be generated) thereafter” can be considered to have a (relatively) high priority (or transmission of a “V2X message (to be generated) thereafter” can be interpreted to be performed by a (most) optimal resource that meets a pre-defined (re-reservation (or selection)) criterion (or rule)).

[0226] [Proposal Rule #3] If one V2X message is transmitted “Q” times (according to Proposal Rule #1), a boundary of a time region in which a (resource (re)reservation (or selection)-related) sensing operation is performed can be defined according to the following (partial) criterion (or rule). Here, the “Q” value can be a positive integer greater than 1. Hereinafter, for convenience of description, it is assumed that (one) V2X message is “transmitted twice (e.g., SF#(N+K1) and SF#(N+K1))”.

[0227] (Example #3-1) (If not (one) V2X message is transmitted (repeatedly) over multiple SFs and / or independent resource allocation is made over individual SFs, then) the first (or last) "repeated transmission timing" (or "SF") can be defined as the boundary of the time region where the (resource (re)reservation related) sensing operation is performed. As a specific example, if the first "repeated transmission timing" (or "SF") (e.g., SF#(N+K1)) is designated as the boundary of the time region where the sensing operation is performed, then the V2X UE performs the sensing operation on the remaining (resource) time points other than the (resource) time point where the V2X UE actually performs the V2X message TX operation on the "resource period ranging from SF#(N+K1-D) to SF#(N+K1) (or from SF#(N+K1-1-D) to SF#(N+K1-1) (where "D" denotes a pre-defined (or signaled) "sensing duration"))", and then (re)reserves (or selects) the V2X message TX related resource. In another example, if the last "repeated transmission timing" (or "SF") (e.g., SF#(N+K2)) is designated as the boundary of the time region where the sensing operation is performed, then the V2X UE performs the sensing operation on the remaining (resource) time points other than the (resource) time point where the V2X UE actually performs the V2X message TX operation on the "resource period ranging from SF#(N+K2-D) to SF#(N+K2) (or from SF#(N+K2-1-D) to SF#(N+K2-1))", and then (re)reserves (or selects) the V2X message TX related resource.

[0228] (Example #3-2) If the part of "Q" repeated transmissions is skipped (or stopped) when attempting to sense (or measure) the resource used (or previously reserved (or selected)), then the first (or last) "skipped (or stopped) transmission timing" (or "SF") can be defined as the boundary of the time region where the (resource (re)reservation related) sensing operation is performed.

[0229] (Example #3-3) If one V2X message is transmitted “Q” times, the following (partial) parameters can be defined (or managed) differently (or independently) for each transmission (or for each different “Redundancy Version (RV)” transmission) (or between initial transmission and retransmission). Also, in another example, the following (partial) parameters can be defined (or managed) independently (or differently) according to different message “sizes (or types)” and / or “transmission (occurrence) periods” and / or “priorities” (or according to whether pre-defined (or signaled) “safety information” is transmitted together with the parameters). As a specific example, for a message with a low (or high) priority, a larger value can be set for the “sensing duration” so that the resource re-reservation (or selection) frequency is lower, while for a message with a high (or low) priority, a smaller value can be set for the “sensing duration” so that the resource re-reservation (or selection) frequency is higher.

[0230] (Example #3-3-1) “Sensing duration” (and / or “probability related to performing resource re-reservation (or selection)” and / or “backoff value related to performing resource re-reservation (or selection)” and / or “maximum reservation time” and / or “muting (or silence or transmission skipping (or stopping)) probability (or period or pattern)”.

[0231] In another example, it can be defined so that the “(resource (re)reservation (or selection) related) sensing operation” and / or “resource re-reservation (or selection)” is performed by the following (partial) rules.

[0232] [Proposal Rule #4] When a V2X UE performs a sensing operation on resources used (or previously reserved (or selected)) by the V2X UE according to “random muting (or silence or transmission skipping (or stop))” (or “pre-defined (or signaled) probability-based muting (or silence or transmission skipping (or stop))”, muting (or silence) is not applied (or skipping (or stop) is not performed) for all SFs for (repeated) transmissions of the (one) V2X message in an alternative manner (periodically) only for a part of SFs (or repeated transmissions) according to a pre-defined (or signaled) rule (or (frequency hopping) pattern). Here, the corresponding (frequency hopping) pattern can be randomized based on input parameters such as a “(source) UE ID” (and / or a “period index of a pool (or resources) for performing V2X message TX operation” and / or a “SA period index”). In another example, when performing “(random) muting (or silence or transmission skipping (or stop))”, the “(random) muting (or silence or transmission skipping (or stop)) probability (or period or pattern)” can be defined differently (or independently) between an initial transmission and retransmissions. Here, this rule can be interpreted such that the “(random) muting (or silence or transmission skipping (or stop)) probability (or period or pattern)” is set differently (or independently) between “RV 0” (initial transmission) and other “RVs” (retransmissions) (or can be interpreted such that the “(random) muting (or silence or transmission skipping (or stop)) probability (or period or pattern)” is set differently (or independently) for each “RV”). As a specific example, it can be configured such that “RV 0” (initial transmission) is applied with a relatively small probability of “(random) muting (or silence or transmission skipping (or stop))” compared to other “RVs” (retransmissions).

[0233] [Proposal Rule #5] If a (one) V2X message is sent through multiple SFs (or if one (V2X) message is sent “Q” times), it can be configured such that not all SFs (or resources related to “Q” times of repeated transmissions) are re-reserved (or selected) at once, but only “T” SFs (or resources related to repeated transmissions) pre-defined (or signaled) are re-reserved (or selected) one after another according to a pre-defined (or signaled) rule (or (frequency hopping) pattern). Here, the “T” value can be set to “1”. In addition, the corresponding (frequency hopping) pattern can be randomized based on input parameters such as a “(source) UE ID” (and / or a “period index of a pool (or resources) for performing V2X message TX operation” and / or a “SA period index”). If the above rule is applied, it can prevent the interference environment from being affected by a sudden change due to re-reservation (or selection) of (all) resources.

[0234] As another example, if a (semi-static) (re)reservation (or selection) of resources related to V2X message TX is performed and a "sensing operation" is performed through decoding of a pre-defined (or signaled) channel (e.g., PSCCH (or scheduling assignment (SA))), then a "data (or physical sidelink shared channel (PSSCH))" decoding operation can be performed according to the following (partial) rules.

[0235] [Proposal Rule #6] Assuming a V2X UE successfully performs SA (or PSCCH) decoding and sets (or turns on) resource reservation. (A) If SA (or PSCCH) is successfully received at the next period, then it is sufficient to perform data (PSSCH) decoding according to the corresponding SA (or PSCCH) (that has been successfully received). (B) (On the other hand) If the V2X UE fails to receive SA (or PSCCH) at the next period, then the V2X UE can be configured to attempt data (PSSCH) decoding by reusing various types of pre-defined (or signaled) information (e.g., resource allocation (RA), modulation and coding scheme (MCS), and RS sequence setting) of the existing (recently received) (or most recently received) SA (or PSCCH).

[0236] [Proposal Rule #7] If a "maximum time" that specifies a period in which a (re)reserved (or selected) resource can be maintained (e.g., in the case of defining a "resource reselection timer") is defined, or if how long a (re)reserved resource is maintained is specified by a "reservation field" of a PSCCH (or SA) (or on a PSSCH (or data)), then an RX V2X UE (that fails to receive SA (or PSCCH)) can be configured to attempt to decode data (PSSCH) using the most recently received PSCCH (or SA) and cause the location of the corresponding resource occupied (by other V2X UEs) to avoid "resource (re)allocation" during the corresponding period.

[0237] In another example, if a better resource satisfying a predefined (or signaled) criteria (or rule) is found while the V2X UE already has a reserved (or selected) resource, the V2X UE can be caused to“re-reserve (or select)” the resource (or the previously reserved (or selected) resource) used by the V2X UE. In an additional example, to sense (or measure) the resource currently reserved (by the V2X UE), instead of performing“muted (or silence),” the V2X UE can temporarily move to a different resource (or pool) that is predefined (or signaled) (and / or perform transmission of V2X messages on the corresponding resource (or pool) that the V2X UE moves to, which can be interpreted as a kind of“V2X message TX without reservation”), and then perform the sensing (or measurement) (of the resource that the V2X UE has reserved), (go back) to the original resource. Here, the“time period” that the V2X UE stays in the other resource (or pool) can be predefined (or signaled). If the above rule is applied, the situation that the transmission of V2X messages is skipped (or stopped) can be mitigated using the“muted (or silence) operation.”

[0238] In another example, the "boundary of the time region in which the specific V2X UE performs the (re)selection of the resource (re)reservation (or selection) related sensing operation" can be the "PIVOT SF (or reference SF)" (SF#P) selected based on a pre-defined (or signaled) rule. Here, when applying this rule, the V2X UE performs the sensing operation on the resource period ranging from "SF#(P-Y1) to SF#(P+Y2) (here, "Y1=FLOOR((D-1) / 2)" and "Y2=CEILING((D-Y1) / 2)" (or "Y1=CEILING((D-1) / 2)" and "Y2=FLOOR((D-Y1) / 2))", after which the V2X message TX related resource is (re)reserved (or selected). Here, "D" denotes a pre-defined (or signaled) "sensing duration", and "CEILING(X)" and "FLOOR(X)" denote a "function that returns the smallest integer greater than or equal to X" and a "function that returns the largest integer less than or equal to X", respectively. Here, the corresponding "PIVOT SF (or reference SF)" can be randomly selected (based on input parameters such as the "(source) UE ID" (and / or the "period index" of the (pool (or resource) period of the) (performing V2X message TX operation) and / or the "SA period index)"). In addition, the proposed rule can be applied only conditionally to the case where the (initial) sensing operation is performed after the (V2X UE) power up and / or the case where the transmission of the V2X message has never been performed (at all) at a previous point in time (or within a (previous) period (or window) lasting for a pre-defined (or signaled) length of time).

[0239] In another example, assume that a V2X UE performs an SA (or PSCCH) transmission associated with a data (PSSCH) transmission on SF#(N+C) (e.g., D > C). Here, in one example, when performing another TB related potential data (PSSCH) transmission on SF#(N+E) in SF#(N+D) (e.g., D < E), the V2X UE can indicate the intention of reusing the (frequency) resources (for the data (PSSCH) transmission on SF#(N+D)) through the (pre-defined (or signaled) channel (e.g., SA (or PSCCH) (SF#(N+C))) (or through the data (PSSCH)). Here, for convenience of description, the (frequency) resources indicated (or signaled) as not intended to be reused by the V2X UE#X when performing another TB related potential data (PSSCH) transmission on SF#(N+E) are referred to as un-booked resources. Here, when a V2X UE#Y performs a sensing operation based on energy measurement (and / or SA decoding), the (frequency) resources indicated as un-booked resources by a V2X UE#X showing high energy (currently (e.g., SF#(N+D)) or within the sensing period) can be assumed (or handled) according to the following (partial) rules (when the V2X UE performs resource selection (or reservation)). This is because, due to the high energy measured (currently (e.g., SF#(N+D)) or within the sensing period), the corresponding (frequency) resources indicated as un-booked resources by the V2X UE#X will not be selected (or reserved) by the V2X UE#Y, even though the corresponding (frequency) resources can not be used with high probability (within a predetermined time period including SF#(N+E)) thereafter. Here, the following rules can be extended to apply when a V2X UE indicates (to other V2X UEs) that the V2X UE no longer uses the previously (at the resource (re)selection (or reservation) period) reserved (or selected) resources (also referred to as un-booked resources) from a certain point in time through the pre-defined (or signaled) channel (e.g., SA (or PSCCH) (or data (PSSCH))). Here, the following rules can be applied only restrictively when the V2X UE performs a sensing operation based on energy measurement only or a sensing operation based on a combination of energy measurement and SA decoding (e.g., the rules can not be applied when performing a sensing operation based on SA decoding only).

[0240] [Proposal Rule #8] The V2X UE considers (or assumes) a remainder obtained by subtracting an “RSRP measurement value” (or a remainder obtained by subtracting a pre-defined (or signaled) offset value) from an energy value measured on a corresponding “(frequency) resource” as an energy measurement value of the “(frequency) resource” designated as an “un-booked resource”, and performs “ordering” of the energy measurement values of the respective resources. Here, the corresponding “RSRP measurement” can be performed based on a reference signal (e.g., “DM-RS”) on a pre-defined (or signaled) channel (e.g., “PSBCH (or “PSCCH” or “PSSCH”)). Here, if “FDM” is applied to “SA (or PSCCH)” and “data (PSSCH)”, the “(frequency) resource” (or “SA (or PSCCH)” or “data (PSSCH)”) related final “RSRP (measurement) value” can be finally derived (or assumed) by compensating (or adding) a (pre-defined (or signaled)) “MPR value” (differently) applied according to a separation distance (in a frequency region) between “SA (or PSCCH)” and “data (PSSCH)” from an actually measured “RSRP value”.

[0241] [Proposal Rule #9] The V2X UE can consider (or assume) a pre-defined (or signaled) value as an “energy measurement value” or an “ordering value” of the “(frequency) resource” designated as an “un-booked resource”. Here, the “ordering” value of the “(frequency) resource” designated as an “un-booked resource” can be set (or signaled) as a lowest rank (in which, for example, a probability of the corresponding “(frequency) resource” being selected (or reserved) is low) (or a highest rank (in which, for example, a probability of the corresponding “(frequency) resource” being selected (or reserved) is high)). In another example, a rule can be defined such that the “(frequency) resource” designated as an “un-booked resource” is always excluded (or (first) selected) at the time of resource selection (or reservation).

[0242] In addition, the sensing operation of the V2X UE can be performed as follows.

[0243] The proposed method describes a (valid) "sensing method" of a V2X UE selecting a "V2X message TX related resource". Here, if the "sensing operation" is applied, different V2X UEs (within a close distance) select a transmission resource at the same location, thereby mitigating the problem of exchanging interference with each other (when actually performing transmission). The word "sensing" can be interpreted as (A) an energy (or power) measurement operation and / or (B) a decoding operation on a predefined (or signaled) channel (e.g., a physical sidelink control channel (PSCCH)). Here, according to a predefined (or signaled) rule (or scheme) (e.g., in a similar manner to a reference signal received quality (RSRQ)), the "energy (or power) measurement" can be represented by (A) a received signal strength indicator (RSSI) (e.g., an average value of received power measured from a transmitted (predefined (or signaled) antenna port's "DM-RS" or transmitted data) symbol) and / or (B) a reference signal received power (RSRP) (e.g., an average value of received power measured from a resource element (RE) of a transmitted (predefined (or signaled) antenna port's) "DM-RS") and / or (C) a combination of "RSSI" and "RSRP".

[0244] In one example, in order to mitigate (A) a "topology" change of a V2X UE and make "sensing" information inaccurate and / or (B) a "half duplex" problem, (from the perspective of a "single V2X UE") "control (or scheduling) information" and "(data associated with the corresponding control (or scheduling) information" can be transmitted on the same subframe (SF) according to a frequency division multiplexing (FDM) scheme.

[0245] Figure 15 and Figure 16 One example of a case where (from the perspective of a "single V2X UE") "control (or scheduling) information" and "(data associated with the corresponding control (or scheduling) information" are transmitted on the same subframe (SF) according to a frequency division multiplexing (FDM) scheme is shown.

[0246] Figure 15 and Figure 16 A case where "control (or scheduling) information and associated data are transmitted on consecutive resource blocks (RBs)" and a case where "control (or scheduling) information and associated data are transmitted on non-consecutive resource blocks (RBs)" are shown. In another example, when considering the "link budget" of "control (or scheduling) information", (from the perspective of a "single V2X UE") it can be considered to transmit "control (or scheduling) information" and "(data associated with the corresponding control (or scheduling) information" on different SFs according to a time division multiplexing (TDM) scheme.

[0247] Figure 17One example of the case where the "control (or scheduling) information transmission pool" and the "data transmission pool" are defined (or configured) according to the "FDM" scheme (from the system's perspective) is shown.

[0248] In one example, the "control (or scheduling) information transmission pool" and the "data transmission pool" can be defined (or configured) according to the "FDM" scheme (from the system's perspective) to (A) (in an efficient manner) meet the "delay requirement" of the "V2X service" and / or (B) disperse the transmission of the "control (or scheduling) information" in the time domain. Figure 17 One example of the above case is shown. Here, it is assumed that the "data transmission pool" associated with a certain "control (or scheduling) information transmission pool" operates according to the "TDM" scheme.

[0249] In addition, although the UE (by default) performs sensing in the (respective) subchannel, the actual transmission of the V2X message can be performed in units of multiple subchannels. If the UE uses multiple subchannels for the actual transmission of the V2X message (i.e., if the transmission of the V2X message is performed in units of multiple subchannels), it is necessary to consider how to perform sensing. In this regard, hereinafter, a method of performing sensing when multiple subchannels are used for the transmission of the V2X message will be described.

[0250] [Proposed method] In one example, a rule can be defined such that the V2X UE performs a sensing operation in units of "resource size" (used by the V2X UE itself) for "V2X message TX". When the corresponding rule is applied, the "sensing resource unit size" of the V2X UE becomes the same as the "resource size" (used by the corresponding V2X UE) for "V2X message TX". For example, when the UE performs energy measurement through a sensing operation, it can be necessary to consider the unit or size in which energy measurement is performed. At this time, the proposed method according to the present application can set the resource unit or size (e.g., subchannel size) used by the UE for data transmission to be the unit or size of energy measurement. For example, when the UE performs V2X message transmission having a certain subchannel size, energy measurement for a sensing operation can be performed in units of resources having the certain subchannel size. Hereinafter, the proposed method will be described with reference to the related drawings.

[0251] Figure 18 is a flowchart showing a method of performing sensing when multiple subchannels are used for the transmission of the V2X message according to one embodiment of the present application.

[0252] According to Figure 18The UE performs sensing on a per-subchannel basis, with a size equal to that of the subchannel used for V2X message transmission, thereby selecting resources for V2X message transmission (S1810). At this time, the UE can select resources by configuring a selection window within a range that meets latency requirements, performing V2X message transmission on a per-subchannel basis, and can select resources for V2X communication based on the sensing performed on a per-subchannel basis, with a size equal to that of the multiple subchannels. The size of the sensing area used when performing sensing can be equal to the size of the multiple subchannels. Furthermore, the UE can use the average energy measurement of the subchannels belonging to the multiple subchannels to perform sensing.

[0253] In summary, when performing V2X communication on a multi-sub-channel basis, the UE can not only perform sensing on a multi-sub-channel basis, but also select resources by configuring a selection window within a range that meets latency requirements. Here, the example of selecting resources by configuring a selection window within a range that meets latency requirements is the same as described above.

[0254] The following section describes an example of a UE performing sensing on a multi-subchannel basis when transmitting V2X messages on a multi-subchannel basis.

[0255] The UE can perform sensing on a per-subchannel basis, with a size equal to that of the subchannel used for V2X message transmission, and select resources for V2X message transmission based on the sensing results. In other words, sensing (e.g., energy measurement) can be performed using the subchannel size of the data to be transmitted by the UE.

[0256] When performing sensing (e.g., energy measurement) using the subchannel size of the data to be transmitted by the UE, the linear average value of the subchannels can be used. More specifically, regarding the set S A The remaining candidate single-frame resources R in (the set of all candidate single-frame resources) x,y Sensing area (e.g., measurement E) x,y The value can be defined as the linear average of the S-RSSI measured at subchannel x+k. Here, k is defined as 0,…,L. subCH -1, where L subCH This indicates the number of sub-channels required to send actual packets. For ease of understanding, this operation can be described with reference to the relevant accompanying diagrams below.

[0257] Figure 19 An example is shown of performing energy measurement (i.e., sensing) using the subchannel size of the data to be transmitted by the UE. Figure 19 Assume the subchannel size of the V2X message (e.g., V2X data) to be sent by the UE is 2 (i.e., L). subCH =2).

[0258] existFigure 19 In the example of FIG. 9, the energy measurement can be performed in units of two subchannels corresponding to the subchannel size of the data to be transmitted by the UE. First, the UE can determine the sensing value with respect to sensing region #1 (i.e., subchannel #1 and subchannel #2) using the average of the energy sensing values with respect to sensing region #1. Also, the UE can determine the sensing value with respect to sensing region #2 (i.e., subchannel #2 and subchannel #3) using the average of the energy sensing values with respect to sensing region #2. In the same manner, the UE can determine the sensing value with respect to sensing region #3 (i.e., subchannel #3 and subchannel #4) using the average of the energy sensing values with respect to sensing region #3.

[0259] Although Figure 19 Assuming that the subchannel size of the data to be transmitted by the UE is 2, the subchannel size of the data to be transmitted by the UE can have a value of 3 or more. Although not shown in a separate figure, if the subchannel size of the data to be transmitted by the UE is 3, the UE can determine the sensing value with respect to the sensing region using the average of the energy sensing values in subchannel #1 through subchannel #3.

[0260] Referring again to Figure 18 , the UE can transmit the V2X message using the selected resources S1820. As described above (or below), the UE can select a subframe within a selection window based on a sensing result obtained by performing sensing during a UE-specific sensing period, determine a transmission reservation resource based on the selected subframe, and perform V2X communication on the reserved resource. Since the specific example in which the UE performs V2X communication based on the selected resource is the same as described above (or below), a detailed description thereof will be omitted.

[0261] Figure 20 and Figure 21 shows one example of "sensing based on partially overlapping regions" (or "sensing based on a sliding window").

[0262] In one example, the sensing operation can be implemented in the form of (A) "sensing based on non-overlapping regions" (see Figure 20 ) and / or (B) "sensing based on partially overlapping regions" (or "sensing based on a sliding window") (see Figure 21 ). When the former rule "(A)" is applied, the sensing regions in which the sensing operation is (continuously) performed do not overlap each other (for example, it can be seen from Figure 20 that "(sensing region #1)", "(sensing region #2)", and "(sensing region #3)" do not overlap each other). On the other hand, when the latter rule "(B)" is applied, for example, the sensing regions in which the sensing operation is (continuously) performed overlap each other in a pre-defined (or signaled) "ratio" (or "amount (or size) of resources") (for example, Figure 21The (sensing region #1) and (sensing region #2), the (sensing region #2) and (sensing region #3), the (sensing region #3) and (sensing region #4), and the (sensing region #4) and (sensing region #5) are shown to overlap with each other in a predefined (or signaled) "ratio" (or "resource amount (or size)"). In one example, the former rule ("(A)") can reduce the "complexity of performing sensing operation" compared to the latter rule ("(B)"). In other words, the "total sensing number" required for the same size of resource pool can be relatively small when the former rule ("(A)") is employed compared to the latter rule ("(B)"). On the other hand, when the latter rule ("(B)") is employed, (although the "total sensing number" required for the same size of resource pool can be larger compared to when the former rule ("(A)") is employed,) the "location of available resource candidate" related to the "V2X message TX" can be searched (or selected) in a relatively efficient (or thorough) manner.

[0263] As another example, the V2X UE can be caused to perform sensing operation (first) in a predefined (or signaled) "resource unit (size)" (e.g., "1 RB"), and a "(weighted) average" (or "sum") of multiple sensing (or measurement) values (or a maximum (or minimum or median) among the multiple sensing (or measurement) values) corresponding to the "resource size (or unit)" for "V2X message TX" can be considered as (or assumed to be) a representative sensing (or measurement) value for each "resource size (or unit)" (for "V2X message TX").

[0264] As another example, when the V2X UE performs "(V2X) channel or signal transmission" (e.g., "multi-cluster TX" (or "DVRB TX")) using resource(s) at "discontinuous locations" on a "frequency (resource) region", the V2X UE can be caused to perform sensing (or measurement) operation (or perform "non-overlapping region based sensing" or "partial overlapping region based sensing" (or "sliding window based sensing") in a resource block group (RBG) unit) in a predefined (or signaled) "sensing resource unit (or size)" (e.g., in K RBs unit) and (finally) select "V2X message TX" related resources among which the (energy) measurement is less than (or greater than) a predefined (or signaled) threshold.

[0265] In another example, assume that for transmitting a “(single) V2X TB (or message)”, a V2X UE performs “K” number of repeated transmissions (e.g., the “K” value includes the number of “initial transmissions” and the number of “retransmissions” (both)). Here, for convenience of description, the “K” value is set to “4”. Now assume that the “SA (or PSCCH)” transmission is performed in “SF#(N+C)” and the associated (four times) “data (PSSCH)” transmissions are performed in “SF#(N+D)”, “SF#(N+D+K1)”, “SF#(N+D+K2)”, and “SF#(N+D+K3)” respectively (e.g., C≤D, 0<K1<K2<K3). Here, a field for informing the location of “time resources” related to (A) “K” or (B) “(K-1)” number of repeated transmissions can be defined on the “SA (or PSCCH)” (“SF#(N+C)”), and for this, the following (partial) rules can be applied. In the latter case (“(B)”), the corresponding field can be interpreted to inform the “time resource location” related to “the remaining (“(K-1)”) transmissions” except for the “initial (or first) transmission”, and / or the “initial (or first) transmission” is interpreted to be (always) performed at the same time resource (location) as the “SA (or PSCCH)” (“SF#(N+C)”), and / or the “time resource location” related to the “initial (or first) transmission” is signaled to the (other) field informing the interval between the transmission time of the “SA (or PSCCH)” (“SF#(N+C)”) and the “initial (or first) transmission” time.

[0266] (Example #A) The "time resource locations" related to the "initial (or first) transmission" are signaled to the (other) "Field #F" that informs the gap between the (pre-defined) "SA (or PSCCH)" ("SF#(N+C)") transmission time and the "initial (or first)" time ("SF#(N+D)"), and the "time resource locations" related to the "remaining "(K-1)" transmissions" (e.g., "SF#(N+D+K1)", "SF#(N+D+K2)", and "SF#(N+D+K3)") can be signaled to the (new) "Field #S" that has the same size as the maximum gap (MAX_GAP) between the pre-defined (or signaled) "first transmission" ("SF#(N+D)") time and the "Kth transmission" ("SF#(N+D+K3)") time. Here, the "Field #S" can be implemented in the form of a "bitmap". The "Field #S" related "bitmap" can be applied using the "initial (or first) (data (PSSCH)) transmission" ("SF#(N+D)") time as a reference (or starting point). If the "MAX_GAP" is set (or signaled) as "10", the "Field #S" is signaled (or set) as "10", and the "Field #S" is signaled (or set) as "0100100100", the "second transmission", "third transmission", and "fourth transmission" are performed on "SF#(N+D+2)", "SF#(N+D+5)", and "SF#(N+D+8)", respectively. As another example, the "time resource locations" related to the "K" times of repeated transmissions (e.g., "SF#(N+D)", "SF#(N+D+K1)", "SF#(N+D+K2)", and "SF#(N+D+K3)") can be signaled to the (new) "Field #Q" that has the same size as the maximum gap (MAX_TVAL) between the pre-defined (or signaled) "SA (or PSCCH)" ("SF#(N+C)") transmission time and the "Kth transmission" ("SF#(N+D+K3)") time. Here, the "Field #Q" can be implemented in the form of a "bitmap". The "Field #Q" related "bitmap" can be applied using the "SA (or PSCCH)" ("SF#(N+C)") time as a reference (or starting point). If the "MAX_TVAL" is set (or signaled) as "10", and the "Field #Q" is signaled (or set) as "1100100100", the "first transmission", "second transmission", "third transmission", and "fourth transmission" are performed on "SF#(N+C+1)", "SF#(N+C+2)", "SF#(N+C+5)", and "SF#(N+C+8)", respectively. In the corresponding example, if the "Field #F" is defined on the "SA (or PSCCH)" ("SF#(N+C)"), the "Field #F" value can be set as 1.As another example, due to V2X communication related "congestion (or load or measurement) control, " the "mode (form or number of items)" (or "(maximum (or minimum)) value (or length)" or "(maximum (or minimum)) number of bits that can be set to "1" on a bitmap") that "field #S" (or "field #Q" (or "field #F")) can have can be limited. Here, the corresponding (limited) information can be determined by the V2X UE after checking the "congestion (or load or measurement)" situation (according to a pre-defined (or signaled) rule (or standard)), or set (or signaled) by the (serving) base station (based on the "congestion (or load or measurement)" information reported by the V2X UE or measured by the (serving) base station). Here, due to V2X communication related "congestion (or load or measurement)", "MAX_GAP" (or "MAX_TVAL" can also have a "maximum (or minimum) value (or length)" can be limited.

[0267] (Example #B) can signal the "time resource locations" (e.g., "SF#(N+D)", "SF#(N+D+K1)", "SF#(N+D+K2)", and "SF#(N+D+K3)") related to "K" times of repeated transmissions to "K" "field #F"s (of "(Example #A)") (e.g., "(Xth) field #F" informs the interval between the "SA (or PSCCH)" ("SF#(N+C)") transmission time and the "Xth transmission" time (in the time region).

[0268] (Example #C) (in the case of applying (partial) rules (e.g., (Example #A) and (Example #B)), if "SA (or PSCCH)" transmission is performed each time "data (PSSCH)" is transmitted ("K" times (e.g., "SF#(N+D)", "SF#(N+D+K1)", "SF#(N+D+K2)", and "SF#(N+D+K3)"), the following (partial) rules can be applied. Here, the following (partial) rules can be limitedly applied only in the case of performing "(data (PSSCH)) frequency hopping".

[0269] (Example #1) The part of the 'SF pattern' information (or field) and / or 'frequency resource (position)' information (or field) and / or 'MCS' information (or field) on the 'SA (or PSCCH)' ('SF#(N+C)') related to the 'initial (or first) transmission' ('SF#(N+D)') can also be transmitted on the 'SA (or PSCCH)' related to the'remaining ((K-1)) transmissions' in the same way. To distinguish the above operation, if one 'TB' is transmitted from multiple SFs, the 'counter' information (or information (or field) on which transmission the 'data (or PSCCH) transmission' corresponds to or 'RV' information (or field) related to the 'data (or PSCCH) transmission') indicating the corresponding ((data (PSSCH) transmission) SF can be included in the 'SA (or PSCCH)' scheduling the (data (PSSCH)) transmission on each SF. Here, the 'SA (or PSCCH)' ('SF#(N+C)') related to the 'initial (or first) transmission' ('SF#(N+D)') can define at least the 'initial (or first) transmission' related 'frequency resource (position)' information (or field) and / or 'MCS' information (or field) and / or (the above) 'field #S' (or 'field #Q') (or 'SF pattern' information (or field)) and / or 'field #F' (which, for example, can be (further) interpreted as a field informing the interval between the 'Xth transmission' related 'SA (or PSCCH)' transmission time and the 'Xth transmission' time) and / or information (or field) on which transmission is the '(corresponding) data (or PSCCH) transmission' (or '(corresponding) data (or PSCCH) transmission' related 'RV' information (or field)) (and / or information (or field) on whether the '(data (PSSCH)) frequency hopping' is applied).If the corresponding rule is applied, the "frequency resource (location)" information related to the "remaining (K-1) transmissions" can not be (directly) transmitted (or signaled) on the related "SA (or PSCCH)" and / or the "field #F" value is set to the interval between the "initial (or first) transmission" related "SA (or PSCCH)" transmission time and the "initial (or first) transmission" time; however, even if the V2X UE fails to receive (or decode) the "previous transmission" related "SA (or PSCCH)", once the V2X UE successfully receives (or decodes) the "subsequent transmission" related "SA (or PSCCH)", the corresponding "subsequent transmission" related "frequency resource (location) information" can be (in the form of backtracking) found (or derived) by combining (A) the "(data (PSSCH)) frequency hopping pattern" information and / or (B) the "initial (or first) transmission" related "frequency resource (location)" information related to the "subsequent transmission" related "SA (or PSCCH)" and / or (C) the "field #S" (or "field #Q") information (or "SF pattern" information) and / or the information about which transmission is the "data (or PSCCH) transmission" (or the "data (or PSCCH) transmission" related "RV" information). Here, the "subsequent transmission" related "time resource (location) information" can be made clear (or derived) by the "field #F" on the "subsequent transmission" related "SA (or PSCCH)". Here, when the proposed rule is applied, (in particular, when the "(data (PSSCH)) frequency hopping" operation is applied,) the V2X UE that has successfully received (or decoded) the "initial (or first) transmission" related "SA (or PSCCH)" can not attempt to decode (or receive) the "remaining ( "(K-1)") transmission" related "SA (or PSCCH)". As another example, (from the proposed rule,) the "field #F" (which, for example, can be interpreted as the "timing gap" between the "SA (or PSCCH)" transmission time and the "associated data (PSSCH)" transmission time) (or the field that informs the "intent" of whether to reuse the "(frequency) resource" adopted by the previous "data (PSSCH)" transmission when the other "TB" related "potential data (PSSCH)" transmission is performed thereafter (at a certain time)) can be defined (or signaled) independently on each "SA (or PSCCH)" transmission (or in the same way (for all "SA (or PSCCH)" transmissions)). Here, when the corresponding rule is applied, the V2X UE can be caused to attempt to decode (or receive) (all "K" times of transmission) with respect to the "K" transmission related "SA (or PSCCH)".In another example, (from the proposal rule,)(when one "TB" is transmitted from multiple SFs,) the V2X TX UE can perform a "resource reselection" operation (in the middle of the operation) according to a pre-defined (or signaled) rule (which includes, for example, a case where a "SA (or PSCCH)" (or "data (PSSCH)") with a "higher priority" transmitted by other V2X UEs is detected and a case where the "current resource allocation" does not satisfy a pre-defined (or signaled) "requirement" (e.g., delay, reliability, priority, fairness, and QoS)). Thus, when a (corresponding "TB" related) "subsequent SA (PSSCH)" is performed with a different schedule than a "previous SA (or PSCCH)", the V2X RX UE can be caused to follow the "subsequent SA (PSSCH)".

[0270] (Example #2) (In (Example #1),) when an "SA (or PSCCH)" related to the "Xth transmission" (e.g., "X > 1") is transmitted, the "field #S" (or "field #Q") can be configured by considering the corresponding "Xth transmission" as an "initial (or first) transmission". In another example, when "frequency resource (location)" information (or a field) is defined on the "SA (or PSCCH)" and a "(data (PSSCH)) frequency hopping" operation is performed, the "frequency resource (location)" information (or field) value itself can be set differently for each "SA (or PSCCH)" transmission (by considering a "(data (PSSCH)) frequency hopping pattern"). This is because, after applying a "(data (PSSCH)) frequency hopping" to the "frequency resource (location)" scheduled by the "Nth transmission" related "SA (or PSCCH)", the "(N+1)th transmission" related "SA (or PSCCH)" must specify (or signal) a (corresponding) changed "frequency resource (location)".

[0271] In another example, the V2X UE can be caused to reselect (during a predetermined time period (or repetition period)) the (transmission) resources reserved (or selected) by the V2X UE each time a pre-defined (or signaled) condition is met. Here, the V2X UE can be caused to select a counter value from a pre-defined (or signaled) range (“C_RANGE”), and reselect (during a predetermined time period (or repetition period)) the (transmission) resources reserved (or selected) by the V2X UE if the corresponding counter becomes “0” (or a value less than “0”). Here, the corresponding counter can (A) decrease (or increase) a pre-defined (or signaled) value (e.g., “1”) for each (new) TB transmission (e.g., a “TB transmission” can be interpreted to refer only to “actually (successfully) performed TB transmissions” and / or (due to “sensing results” and / or “conflict with (other V2X UE’s) message transmissions (with relatively high priority),) a “TB transmission” can be interpreted to include “skipped TB transmissions”), or (B) decrease (or increase) a pre-defined (or signaled) value (e.g., “1”) per a pre-defined (or signaled) (period) value (e.g., “100 ms”). Here, the operation of (re)selecting a counter value from a pre-defined (or signaled) range (or the operation of “resetting” a counter value) can be defined as a case where a “(all) semi-persistently selected resource” related “resource reselection” has been triggered. Here, the “C_RANGE” value can be set (or assumed) differently according to the following (partial) parameters. The “C_RANGE” value (according to the range of (particular) parameters) can be pre-defined or signaled from the network.

[0272] (Example #1) “V2X UE speed”. In case of a fast “V2X UE speed” (relatively fast or faster than a pre-defined (or signaled) threshold), a (relatively) long (or short) “C_RANGE” value can be applied.

[0273] (Example #2) “(transmission) synchronization reference type” (e.g., “eNB”, “GNSS”, “UE”). Here, when the “(transmission) synchronization reference type” is GNSS (or eNB or UE), a (relatively) long (or short) “C_RANGE” value can be applied. (The “C_RANGE” value is (relatively) long (or short) compared to the case where the “(transmission) synchronization reference type” is eNB (or UE or GNSS).)

[0274] (Example #3) “V2X message transmission (and / or generation) periodicity”. In case of a long “V2X message transmission (and / or generation) periodicity” (relatively long or longer than a pre-defined (or signaled) threshold), a (relatively) long (or short) “C_RANGE” value can be applied.

[0275] (Example #4) "V2X message (and / or service) type" (e.g., "event triggered message", "periodic message" (or "message with (relatively) small latency requirement (and / or (relatively) high reliability (or QoS) requirement and / or (relatively) high priority)", "message with (relatively) long latency requirement (and / or (relatively) low reliability (or QoS) requirement and / or (relatively) low priority)"). Here, in case of "event triggered message", (relatively) long (or short) "C_RANGE" value can be applied. (Compared to case of "periodic message", "C_RANGE" value is (relatively) long (or short).

[0276] (Example #5) "V2X message (and / or service) priority (and / or latency requirement and / or reliability requirement and / or QoS requirement)". Here, in case of (relatively) low "V2X message (and / or service) priority (and / or latency requirement and / or reliability requirement and / or QoS requirement)", (relatively) long (or short) "C_RANGE" value can be applied.

[0277] In another example, the V2X TX UE can be caused to perform (re)reservation (or selection) operation of transmission resource(s) (for V2X message) according to (all or part of) the following rules. The (corresponding) transmission resource (re)reservation (or selection) operation can be triggered when the (transmission resource (re)reservation) counter value (SEL_CNTVAL) randomly selected by the V2X TX UE within a pre-defined (or signaled) range (e.g., “5-15”) becomes “0” (and / or a “negative integer value”). In one example, after considering (or assuming) that as many transmission resources as the (selected) counter value (and / or a value derived from the (selected) counter value) have been reserved (or selected) for each (actual) transmission of a transport block (TB) (or packet) (and / or regardless of (actual) TB (or packet) transmission), the (selected) counter value can be decreased by a pre-defined (or signaled) value (e.g., “1”) each time the corresponding reserved (or selected) transmission resource passes (over a time region) and / or if there is (and / or is not) a TB (or packet) (to be transmitted or generated (or received)) on the (lower layer) buffer (and / or PDCP layer). In the present invention, the term “(re)reservation (or selection)” (generally) can be interpreted as (A) re-reserving (or selecting) transmission resource(s) (different (or same) from existing resource(s)) based on sensing result(s) (e.g., “Step 3 above”) (e.g., assuming that the previously selected (transmission) resource(s) is maintained only when a value randomly selected between 0 and 1 is less than or equal to a pre-defined (or signaled) probability value (KEEP_P)) (or regardless of the corresponding probability value (KEEP_P)), and / or (B) maintaining (or reusing) the previously selected (transmission) resource(s) based on a pre-defined (or signaled) probability value (KEEP_P) (or regardless of the corresponding probability value (KEEP_P)), and / or (C) re-reserving (or reusing) a limited number (or a pre-defined (or signaled) (other) number (which is, for example, interpreted as greater than (or greater than or equal to) the SEL_CNTVAL value (and / or a value derived from the SEL_CNTVAL value)) of subframes (or resource(s) (same as existing resource(s))) as the existing subframes (if (re)reservation (or selection) operation is generally performed, the (transmission resource (re)reservation) counter value can be (randomly) selected (or (instead of re-selecting the counter value), the (transmission resource (re)reservation) counter value can use (or maintain or apply) the existing value (SEL_CNTVAL) (or a remaining value (or a pre-defined (or signaled) (other) value)).

[0278] (Example #1) When a V2X TX UE performs a transmission resource (re-)reservation (or selection), after the V2X TX UE (first) reserves (or selects) an infinite number of subframes (or resources) (with a resource reservation (gap) period "P"), the V2X TX UE can be caused to use the (corresponding) reserved (or selected) resources until a transmission resource (re-)reservation (or selection) operation is triggered. However, if the corresponding rule is applied, a "System Frame Number (SFN wraparound" problem can occur.

[0279] Hereinafter, a case where the "System Frame Number (SFN wraparound" problem occurs will be described with reference to the related drawings for convenience of understanding.

[0280] Figure 22 A case where the "System Frame Number (SFN wraparound" problem occurs is illustrated.

[0281] Figure 22 It is assumed that a V2X TX UE #X attempts to perform a transmission resource (re-)reservation (or selection) with a resource reservation (gap) period of "100 ms" at a subframe #0 time point. It is also assumed that all 1024 subframes are set (or signaled) as V2X resources (pool). In this case, when the V2X TX UE #X needs to select subframe #0, subframe #100, …, subframe #10200, and subframe #10300, the V2X TX UE #X selects subframe #60 (due to the constraint on the SFN). As a result, when the V2X TX UE #X completes the selection of (all) subframes, a second transmission opportunity comes before subframe #100.

[0282] Further, to solve the corresponding problem, when performing a transmission resource (re-)reservation (or selection), the V2X TX UE can be caused to (first) reserve (or select) a limited number (FINI_SFNUM) of subframes (or resources) (with a resource reservation (gap) period "P"). Hereinafter, an example in which a UE reserves a limited number of resources (i.e., 10*SL_RESOURCE_RESELECTION_COUNTER) according to a pre-defined rule will be described with reference to the related drawings.

[0283] Figure 23 is a flowchart illustrating a method of reserving a limited number of resources according to an embodiment of the present application.

[0284] Referring to Figure 23, the UE can perform a reservation of a limited number of resources for performing V2X communication S2310. The UE can select resources on a selection window and perform a reservation of repeated resources based on a certain period using the selected resources, where the number of reserved resources is limited. At this time, the limited number can be proportional to a counter value (e.g., SL_RESOURCE_RESELECTION_COUNTER) randomly selected (or determined), where the counter value can have a positive integer. Also, the limited number can have a value that is ten times the counter value randomly selected for the UE. Hereinafter, an example in which the UE reserves a limited number of resources will be described in detail.

[0285] The UE can reserve a plurality of resources for performing V2X communication, and the number of reserved resources can be limited. When the UE reserves a limited number of resources, a pre-defined rule (e.g., 10*SL_RESOURCE_RESELECTION_COUNTER) can be applied.

[0286] As a specific example of the pre-defined rule, the number of subframes in one set of time and frequency resources of a transmission opportunity of a PSSCH can be set to a certain value (e.g., C resel ) at this time, (when a certain counter (e.g., SL_RESOURCE_RESELECTION_COUNTER) is configured) C resel may be defined as 10*SL_RESOURCE_RESELECTION_COUNTER, otherwise (i.e., when SL_RESOURCE_RESELECTION_COUNTER is not configured) C resel may be set to 1. Here, SL_RESOURCE_RESELECTION_COUNTER can be set to a random value of 5 or more and 15 or less.

[0287] For example, when SL_RESOURCE_RESELECTION_COUNTER is 5, a total of 50 subframes can be reserved for transmission of a PSSCH, and when SL_RESOURCE_RESELECTION_COUNTER is 15, a total of 150 subframes can be reserved for transmission of a PSSCH.

[0288] (corresponding) limited number (and / or TNUM_V2XSF value) can be interpreted as greater than (or greater than or equal to) the SEL_CNTVAL value (and / or a value derived from the SEL_CNTVAL value) (and / or (corresponding) limited number (and / or TNUM_V2XSF value) can be interpreted as a maximum number of subframes (or resources) of (a type of) which can be reserved (or selected)). By applying the corresponding rule, it is also possible to alleviate the problem that (all) reserved (or selected) subframes (or resources) (in a time region) pass even if the (selected) counter value is a positive integer. Here, although the V2X TX UE defines (corresponding) limited number (which can be interpreted as a maximum number of subframes (or resources) of (a type of) which can be reserved (or selected), for example), if the SEL_CNTVAL value (and / or a value derived from the SEL_CNTVAL value) is less than (corresponding) limited number, the V2X TX UE can be caused to (exceptionally) reserve (or select) SEL_CNTVAL (and / or a value derived from the SEL_CNTVAL value and / or a value less than SEL_CNTVAL) subframes (or resources).

[0289] The UE can perform V2X communication on a limited number of resources S2320. The UE performs V2X communication on the reserved resources in the same manner as described above.

[0290] Further, the UE does not perform V2X transmission on the reserved resources indefinitely. In other words, the UE can reselect the reserved transmission resources, and as described above, the (corresponding) transmission resource (re)reservation (or selection) operation can be triggered when the (transmission resource (re)reservation) counter value (SEL_CNTVAL) randomly selected by the V2X TX UE within the pre-defined (or signaled) range (e.g., “5-15”) becomes 0 (and / or a “negative integer value”).

[0291] At this time, when no more reserved resources are left, the V2X UE can perform resource reselection in the selection window. In addition, when the V2X UE does not perform V2X transmission for 1 second continuously, the resource reselection can be performed in the selection window, and when the V2X UE does not perform V2X transmission continuously for a predetermined number of transmission opportunities, the resource reselection can be performed in the selection window. In one example, when (corresponding) limited number (and / or TNUM_V2XSF) of reserved (or selected) subframes (or resources) (in a time region) (all) pass by (and / or pre-defined (or signaled) subframe index (e.g., 10240 (or TNUM_V2XSF)) pass by), if the (selected) counter value does not become “0” (and / or a “negative integer value”), the V2X TX UE can be caused to perform the transmission (re)reservation (or selection) operation, but reselect (the transmission resource (re)reservation) counter value (or (instead of reselecting (the transmission resource (re)reservation) counter value), the existing value (SEL_CNTVAL) (or remaining value (or pre-defined (or signaled) (other) value)) can be used (or maintained or applied).

[0292] Specific examples in which the UE reselects the transmission resources will be described later.

[0293] The (corresponding) term "transmission resource (re-)reservation (or selection) operation" can be interpreted as (A) (re-)reserving (or selecting) a transmission resource (different (or same) from an existing resource) based on sensing results when the V2X TX UE determines not to maintain (or reuse) a previously selected (transmission) resource based on (or irrespective of) a (pre-defined (or signaled) probability value (KEEP_P)), and / or (B) the V2X TX UE maintains (or reuses) a previously selected (transmission) resource based on (or irrespective of) a (pre-defined (or signaled) probability value (KEEP_P)), and / or (C) (re-)reserving (or selecting) a limited number (or a (pre-defined (or signaled) (other) number which is e.g. interpreted as being greater (or greater than or equal to) a SEL_CNTVAL value (and / or a value derived from a SEL_CNTVAL value)) of subframes (or resources (same as the existing resource)) (again) identical to an existing subframe.

[0294] (Example #2) (When applying (Example #1),) whether a collision (or overlap) occurs according to a (limited) number (NUM_EXTX) of transmissions assumed (or considered) by V2X TX UE#X to be performed (on the corresponding candidate resources) (or when the transmissions are assumed (or considered) to be performed as many times as the limited number of subframes (or resources) reserved (or selected) by V2X TX UE#X (with the resource reservation (gap) period "P_X"),) V2X TX UE#X (e.g., resource reservation (gap) period "P_X") can determine (e.g., "Step 2" above) whether the transmission resources with resource reservation (gap) period "P_Y" reserved (or selected) by other V2X TX UE#Y collide (or overlap) with the candidate resources V2X TX UE#X can reserve (or select). Here, in one example (of applying the corresponding rule), if (from (subframe #(N-10)) PSCCH decoding) it is found that V2X TX UE#Y (with a resource reservation (gap) period of "100 ms") has reserved (or selected) transmission resources on subframe #(N-10) and subframe #(N+990) with a resource reservation (gap) period of "1000 ms", V2X TX UE#X can be caused to perform monitoring "subframe #(N+90), subframe #(N+190), subframe #(N+290), subframe #(N+390), subframe #(N+490), subframe #(N+590), subframe #(N+690), subframe #(N+790), subframe #(N+890) (subframe #(N+990))" (and / or "subframe #(N+(990-100*9)), subframe #(N+(990-100*8)), subframe #(N+(990-100*7)), subframe #(N+(990-100*6)), subframe #(N+(990-100*5)), subframe #(N+(990-100*4)), subframe #(N+(990-100*3)), subframe #(N+(990-100*2)), subframe #(N+(990-100)) (subframe #(N+990)") to determine whether candidate resources (at the same (frequency) location as V2X TX UE#Y) can be selected on subframe #(N+90) (within the pre-defined (or assumed) "(TX resource) selection window") when performing transmission resource (re)reservation (or selection) on subframe #N (current time).The corresponding monitoring performed by the V2X TX UE#X can determine whether the time point (e.g., subframe #G (e.g., “G = (N + 990)”) of the resource (or subframe) (further) reserved (or selected) by the (corresponding) V2X TX UE#Y (based on “P_Y”) overlaps with subframe #(Z + P_X*K) (here, for example, “0 ≤ K ≤ (the largest integer value M satisfying the condition that the value of “(Z + P_X*M)” is less than or equal to the value of “G”) (and / or subframe #Z and subframe #(G - P_X*R) overlap with each other (here, for example, “0 ≤ R ≤ (the largest integer value H satisfying the condition that the value of “(G - P_X*H)” is greater than or equal to the minimum subframe index value within the (predefined (or assumed)) “(TX_RESOURCE) selection window”)) overlap with each other) determines whether the candidate resource (subframe #Z (e.g., “Z = (N + 90)”) at the same (frequency) location reserved (or selected) by the V2X TX UE#Y (within the (predefined (or assumed)) “(TX_RESOURCE) selection window”) can be selected. When the proposed rule (of (example) #2) is applied, the number of resources reserved (or selected) by the V2X TX UE (e.g., (example) #1) can be different from the number of resources that must be monitored for future behavior to determine a conflict (or overlap) (e.g., (example) #2). At this time, as another example (of the case where the corresponding rule is applied), when it is found (from (subframe #(N-10)) PSCCH decoding) that the V2X TX UE#Y has reserved (or selected) transmission resources on subframe #(N-10) and subframe #(N+990) with a resource reservation (interval) period of “1000ms”, and the V2X TX UE#X (with a resource reservation (interval) period of “100ms”) performs (re)reservation (or selection) of transmission resources at subframe #N (current time), according to whether the candidate resources assumed (or considered) (a limited number (e.g., “9”)) (e.g., the corresponding (limited) number can be set by the (maximum) integer value at the time of monitoring the maximum value of the subframe index not to exceed the time point of the transmission resource (e.g., subframe #(N+990)) reserved (or selected) by the V2X TX UE#Y) of transmission (e.g., subframe #(N+90), subframe #(N+190), subframe #(N+290), subframe #(N+390), subframe #(N+490), subframe #(N+590), subframe #(N+690), subframe #(N+790), subframe #(N+890)) conflict (or overlap) with the transmission resource (e.g., subframe #(N+990)) reserved (or selected) by the V2X TX UE#Y, the candidate resource on subframe #(N+90) (at the same (frequency) location of the V2X TX UE#Y) can be (finally) selected.Since no collision (or overlap) occurs in the corresponding example, the candidate resource can be (finally) selected. In one example, the NUM_EXTX value and the FINI_SFNUM value (see (Example #1)) can be set (or signaled) independently (or differently) (or in the same way). The FINI_SFNUM value can be set (or signaled) by a common value (or independent value) in the V2X UE (group) on the same carrier (or frequency) (sharing the V2X resource pool) (and / or the NUM_EXTX value can be set (or signaled) by an independent value (e.g., set by the upper layer of the UE) (or a common value) in the V2X UE (group) on the same carrier (or frequency) (sharing the V2X resource pool)).

[0295] (Example #3) When the (selected) counter value is decreased by a pre-defined (or signaled) value (e.g., “1”) per (actual) TB (or packet) transmission, if (in the (lower) buffer (and / or PDCP layer)) there is no TB (or packet) to be transmitted to the V2X TX UE #M (for a long time) (and / or if no (actual) TB (or packet) transmission is performed), the decrease of the (selected) counter value will stop, and when (after a long period of time) a TB (or packet) to be transmitted is generated again (and / or when (actual) TB (or packet) transmission is performed), the (corresponding) V2X TX UE #M considers (or assumes) that the (previously) reserved (or selected) resource is still available (since the (selected) counter value is a positive integer value), thereby not using the (corresponding) resource properly.

[0296] The UE can re-select the reserved transmission resource, and (at least) when the (transmission resource (re)reservation) counter value (SEL_CNTVAL) randomly selected within the range (e.g., “5-15”) pre-defined (or signaled) by the V2X TX UE becomes “0” (and / or a negative integer value), the (corresponding) transmission resource (re)reservation (or selection) operation can be triggered. Here, when the UE actually performs transmission, the counter value can be decreased by “1”, and when the counter value becomes 0, the UE can perform the resource re-reservation operation. In other words, in this case, the transmission resource re-reservation can be (triggered) only when the UE actually performs transmission (on the (previously) reserved resource).

[0297] As described above, the counter value (triggering resource re-reservation) is decreased only when the UE actually performs packet transmission (on the (previously) reserved resource). In the case where a (limited) number of (previously) reserved resources pass (over time) in their entirety, if the corresponding counter value does not become “0” (and / or a negative integer value), a deadlock problem (a case where resource re-reservation is never triggered) can occur.

[0298] Therefore, to solve the above problems, hereinafter, a method of performing resource re-reservation (i.e., resource re-selection) even when the counter value does not become 0 will be described with reference to the related drawings.

[0299] Figure 24 is a flowchart of a method of UE re-selecting a resource according to an embodiment of the present application.

[0300] Referring to Figure 24 , the UE determines whether a resource re-selection condition is satisfied S2410. The resource re-selection can depend on a plurality of conditions. If at least one condition is satisfied among the plurality of resource re-selection conditions, the UE can perform the resource re-selection. In one example, (to solve the corresponding problem,) if there is no TB (or packet) to be transmitted (in the (lower) buffer (and / or PDCP layer)) over a pre-defined (or signaled) threshold (time) (and / or if (continuous) TB (or packet) transmission is not performed) (and / or if the (current) subframe index exceeds 10240 (or TNUM_V2XSF) and / or if (a limited number of) subframes (or resources) (reserved (or selected) by the V2X TX UE #M (in the time region)) (all) pass), the V2X TX UE #M (whose (selected) counter value is a positive integer value) can be caused to perform a transmission resource (re-)reservation (or selection) operation, but the (transmission resource (re-)reservation) counter value can be (randomly) selected (or (instead of re-(randomly) selecting the counter value), the (transmission resource (re-)reservation) counter value can use (or maintain or apply) the existing value (SEL_CNTVAL) (or the remaining value (or the (other) value pre-defined (or signaled))).

[0301] In summary, the resource re-selection conditions of the UE can include: (A) a case where no more resources remain for V2X transmission (e.g., a case of "all of the subframes (or resources) reserved (or selected) by the UE pass" as described above); (B) a case where the UE does not perform packet transmission for 1 second continuously (e.g., a case of "no (continuous) TB (or packet) transmission is performed over a pre-defined (or signaled) threshold time value" as described above); and (C) a case where the UE skips a predetermined number of consecutive transmission opportunities (e.g., a case of "no (continuous) TB (or packet) transmission is performed over a pre-defined (or signaled) threshold" as described above). Hereinafter, specific examples of the above resource re-selection conditions will be described.

[0302] (A) a case where no more resources remain for V2X transmission

[0303] The UE can perform resource reselection when no more resources related to the configured sidelink grant remain. In other words, if no more resources related to the configured sidelink grant remain, but there is a new MAC PDU to be transmitted to the UE, resource reselection can be triggered (in other words, the UE can perform resource reselection in the above case).

[0304] In one example, when a (corresponding) limited number of (and / or TNUM_V2XSF) reserved (or selected) subframes (or resources) (in a time region) are (all) passed through (and / or predefined (or signaled) subframe index (e.g., 10240 (or TNUM_V2XSF))), if the (selected) counter value does not become "0" (and / or "negative integer value"), the V2X TX UE can be caused to perform a transmission resource (re)reservation (or selection) operation, but the (transmission resource (re)reservation) counter value can be (randomly) selected (or (instead of re-selecting the counter value randomly), the (transmission resource (re)reservation) counter value can use (or maintain or apply) an existing value (SEL_CNTVAL) (or remaining value (or (other) value(s) predefined (or signaled))).

[0305] (B) Case where the UE does not perform packet transmission for a consecutive second

[0306] If the (MAC entity) does not perform transmission or retransmission on the resources indicated by the configured sidelink grant for 1 second, the UE can perform resource reselection. In other words, when the UE does not perform transmission or retransmission for a consecutive transmission opportunity for 1 second, resource reselection can be triggered.

[0307] (C) Case where the UE skips a predetermined number of consecutive transmission opportunities

[0308] If the UE is configured with a predetermined value and the number of transmission opportunities (on the resources indicated by the configured sidelink grant) is the same as the predetermined value, the UE can perform resource reselection. In other words, if a certain value is set for the UE and the UE consecutively skips as many transmission opportunities as the certain number, the UE can perform resource reselection.

[0309] In other words, if the UE skips N (a positive integer) consecutive transmission opportunities, resource reselection can be triggered. Here, when the above condition is applied, N is set for the UE, where N can be taken from [1, 2, 3, 4, 5, 6, 7, 8, 9].

[0310] For example, if the UE skips "5" consecutive transmission opportunities and is configured to perform resource reselection, the UE can perform resource reselection when transmission is not performed for 5 consecutive transmission opportunities.

[0311] Thereafter, if the resource reselection condition is satisfied, the UE can perform reselection of a resource for performing V2X communication S2420. In other words, if the resource reselection condition is satisfied, the UE can reselect a resource for performing V2X communication, after which the UE can perform V2X communication on the selected resource. For example, as described above, when (A) there is no more resource left for V2X transmission (e.g., as described above, the case of "all of the subframes (or resources) reserved (or selected) by the UE pass"), (B) the UE does not perform packet transmission for 1 second continuously (e.g., as described above, the case of "no (continuous) TB (or packet) transmission is performed for more than a threshold time value defined (or signaled)"), or (C) the UE skips a predetermined number of consecutive transmission opportunities (e.g., as described above, the case of "no TB (or packet) transmission is performed (continuously) for more than a threshold value defined (or signaled)"), the UE can reselect a resource for performing V2X communication and perform V2X communication on the selected resource.

[0312] Thereafter, the UE can perform V2X communication using the selected resource S2430. Here, as described above, the selected resource can indicate a resource determined based on a selection window configured within a range satisfying a delay requirement (in other words, a resource on a selection window satisfying a delay requirement). In addition, as described above (or below), the UE can select a subframe within the selection window based on a sensing result obtained by performing sensing in a UE-specific sensing period, determine a transmission reservation resource based on the selected subframe, and perform V2X communication on the reserved resource. Since a specific example in which the UE performs V2X communication based on the selected resource is the same as described above (or below), specific details will be omitted.

[0313] Here, in one example, the term (corresponding) "transmission resource (re)reservation (or selection) operation" can be interpreted as (A) when a V2X TX UE determines not to maintain (or reuse) a previously selected (transmission) resource based on a (predefined (or signaled) probability value (KEEP_P) (or regardless of the corresponding probability value (KEEP_P)), (re)reserve (or select) a transmission resource (different (or the same) from an existing resource) based on a sensing result, and / or (B) based on a (predefined (or signaled) probability value (KEEP_P) (or regardless of the corresponding probability value (KEEP_P)), the V2X TX UE maintains (or reuses) a previously selected (transmission) resource, and / or (C) (re)reserve (or select) a limited number (or a (different) number predefined (or signaled) (which is, for example, interpreted as greater (or greater than or equal to) than a SEL_CNTVAL value (and / or a value derived from a SEL_CNTVAL value))) of subframes (or resources (the same as the existing resource)).

[0314] (Example #4) In one example, (when a V2X TX UE #U performs (re)reservation (or selection) of transmission resources and / or determines the location of subframes (or resources) selected (or reserved) by other V2X TX UEs #Z,) if a finite (or infinite) number of (reserved (or selected)) subframes (or resources) with a resource reservation (gap) period "P" exceeds (a previous) 10240th subframe (e.g., a "Z"th subframe (here, in one example, "Z" is a positive integer value greater than "10240")), the V2X TX UE #U can be caused to consider (or assume) that (re)reservation (or selection) of subframes (or resources) is performed with a resource reservation (gap) period "P" from the "MOD(Z, 10240)"th subframe onwards (again).

[0315] (Example #5) (In the case of (Example #1) and / or (Example #2) and / or (Example #3) and / or (Example #4)) (re)reservation (or selection) of a finite (or infinite) number of subframes (or resources) can be performed (by a V2X UE) by itself, while allowing the reservation (or selection) to exceed the SFN range (or TNUM_V2XSF range) by applying SFN wrap-around, and the V2X UE can be caused to perform to skip exceptional (time point) subframes (or resources) (and / or extend the SFN range (or TNUM_V2XSF range) for (re)reservation (or selection) of a finite (or infinite) number of subframes (or resources)) from valid transmission subframes (or resources) while maintaining the resource reservation (gap) period "P" of the V2X UE.

[0316] (Example #7) In one example, the following description supports a method of efficient (V2X message (or TB)) transmission operation of a V2X TX UE. In the following, it is assumed that the UE reserves 10*C subframes at an interval of a resource reservation period P, where C can represent a SL_RESOURCE_RESELECTION_COUNTER determined by a MAC.

[0317] (A) As described above, the UE reserving 10*C subframes at an interval of a resource reservation period P can cause approximately two problems.

[0318] First, although the UE reserves a finite number of subframes, the SL_RESOURCE_RESELECTION_COUNTER can be decreased only when a MAC PDU is transmitted. Thus, when the upper layer stops packet generation for a certain period of time and skips transmission in a large number of reserved subframes, the resources reserved for the UE can become no longer valid, and no more resources can be available for transmission of newly arrived packets.

[0319] In addition, if the time period of the set of reserved subframes exceeds the D2D frame number (DFN) range (i.e., 10 * C * P > T max where T max is 10240 or 10176), the subframe numbers in the second DFN range cannot be divided by 100 (i.e., division by 100 can result in a remainder).

[0320] For example, as Figure 22 shown, if the V2X subframes have an index range of 10240, and the UE reserves subframes having indices {0, 100, …, 10200, 10300, …, 14900}, the subframe numbers from 10300 to 14900 exceed the DFN range; thus, only subframes having indices {0, 100, …, 10200, 60, 160, …, 3660} can be reserved.

[0321] (B) In this regard, a method to solve the above two problems will be provided hereinafter.

[0322] First, to solve the first problem, the UE can extend resource reservation when SL_RESOURCE_RESELECTION_COUNTER is still greater than 0 even though there is no more resource left reserved by other UEs.

[0323] To solve the second problem, the number of reserved subframes can be configured independently of the counter value. In addition, the number of reserved subframes can be configured to be smaller than the counter value. For example, when resource reservation is triggered, the UE can reserve a set of subframes up to the boundary of the DFN range.

[0324] Figure 25 One example of a method of performing resource reservation by considering the above proposals is shown.

[0325] According to Figure 25 , by considering the above two proposals together, the UE can first determine a set of subframes that terminates before the DFN boundary and if more resources are needed, repeat resource reservation at the same resource reservation interval.

[0326] (C) The above proposals can be summarized as follows.

[0327] Proposal 1: The UE can extend resource reservation when SL_RESOURCE_RESELECTION_COUNTER is still greater than 0 even though the UE no longer has reserved resources.

[0328] Proposal 2: When resource reservation is triggered, the UE can reserve a set of subframes up to the boundary of the current DFN range.

[0329] One example of a transmission resource (re)reservation (or selection) operation of a V2X TX UE can be described as shown in Table 2.

[0330]

[0331]

[0332]

[0333]

[0334] In one example, the V2X TX UE can be caused to perform the transmission resource (re)reservation (or selection) operation according to Table 2 (e.g., the above (or below) “Step 2 or 3”). Here, the “Resource Reservation Field (RR_FIELD)” value in the SCI format can be set by a quotient (or value) (I_VALUE) obtained by dividing a “Resource Reservation Interval (RR_INV)” value (set (or signaled) by the upper layer (of the UE)) by a pre-defined (or signaled) value (P_STEP) (e.g., “P_STEP = 100”). Here, I_VALUE can be set (or signaled) to have a range of (max) “1 ≤ I_VALUE ≤ 10”. Here, the selection (or allowance) of a specific I_VALUE can be determined in the form of “carrier (or pool) specific network (pre-)configuration” (through a pre-defined signaling (e.g., X-th bit of a 10-bit bitmap indicates whether X-th I_VALUE can be selected (or allowed) or not). Here, the limitation of the selection of a specific I_VALUE (I_RESVAL) can be interpreted as (A) not setting (or signaling) the RR_INV value of the “I_RESVAL*P_STEP” value (by the upper layer (of the UE)), and / or (B) having to set (or signal) a different I_VALUE (other than I_RESVAL) capable of expressing the closest value of the (actual) desired RR_INV (of the upper layer (of the UE)).

[0335] In addition, when the UE performs transmission while sensing (in the sensing window), that is, the UE can not be able to perform sensing on subframes within the sensing window in which V2X transmission is performed (due to the half duplex problem). At this time, when the UE performs V2X message transmission on subframes corresponding to subframes in which sensing cannot be performed for a certain period, the UE transmits a V2X message based on subframes in which sensing cannot be performed.

[0336] In this regard, hereinafter, in order to solve the problem that the UE transmits a V2X message based on subframes in which sensing cannot be performed, a method of excluding subframes related to subframes in which the UE cannot perform sensing (from the selection window) will be described with reference to the related drawings.

[0337] Figure 26is a flowchart of a method of excluding (from a selection window) subframes related to subframes in which the UE failed to perform sensing according to an embodiment of the present application.

[0338] Referring to Figure 26 , the UE selects a subframe S2610 excluding (from the selection window) a subframe related to a subframe in which a transmission has been performed during the sensing period (from the selection window). In other words, among a plurality of subframes in the selection window, a subframe related to a subframe in which a transmission has been performed during the sensing period is excluded from the selection window, the UE can select a subframe from among a plurality of subframes in the selection window except for the excluded subframe.

[0339] Here, according to a resource reservation period of a selected subframe selected by the UE within the selection window, a subframe related to a subframe in which a transmission has been performed during the sensing period in the selection window can overlap with a subframe corresponding to a subframe in which the UE fails to perform sensing. For the convenience of understanding, the present specification will be further explained in detail with reference to the related drawings.

[0340] Figure 27 An example of a subframe related to a subframe in which the UE fails to perform sensing (from the selection window) is illustrated.

[0341] Referring to Figure 27 , for example, the first subframe can be a subframe in which the UE fails to perform sensing. A subframe corresponding to the first subframe at a certain period can be assumed to be the third subframe.

[0342] Here, when the second subframe is selected from the selection window, a plurality of subframes can be reserved according to a resource reservation period of the selected second subframe, and if one (or more) of the reserved subframes overlaps with the third subframe, the UE can not select the second subframe within the selection window (i.e., the second subframe can be excluded from the selection).

[0343] Referring to Figure 26 , in summary of the above operations, for example, if the UE fails to perform sensing (within the sensing window) in subframe #k (due to performing V2X message transmission) and subframe #(y+P*j) and subframe #(K+100*i) overlap with each other, the UE can exclude subframe #y within the selection window from resource reservation selection. Here, as described above, subframe #k corresponds to a subframe in which the UE fails to perform sensing, and subframe #y can indicate a subframe within the selection window. In addition, P can represent a resource reservation period of the UE, in which, for example, P can have a value of 100 ms. j can assume a value of 0, 1, 2, …, C _resel -1. As described above, C _reselThis can represent a value proportional to a specific counter value (e.g., 10 * SL_RESOURCE_RESELECTION_COUNTER). Since the description of the specific counter (i.e., SL_RESOURCE_RESELECTION_COUNTER) is the same as above, its specific description will be omitted. Additionally, i can represent an element in a set restricted by carrier-specific settings. In other words, i can represent a value reserved by the eNB and a value associated with a specific time period (e.g., if i is 2, then the specific time period (e.g., 1 hop) is 100 * i = 200 ms). In this case, for example, i can have values ​​of 2, 4, 6, and 8.

[0344] In one example, in step 5 of Table 2, if no subframe is detected from the V2X message transmission operation of the V2X TX UE in step 2 # (and / or if due to V2X message transmission operation, no subframe # Performs PSCCH decoding and (associated) PSSCH DM-RS RSRP (and / or S-RSSI) measurement operations related to other V2X TX UEs and belongs to S A R X,Y R in X,Y+RR_INV*TjX With subframe # (and / or subframe#) If resources (partially reserved) that can be selected (or reserved) by other V2X TX UEs overlap, then the V2X TX UE can (additionally) access resources from set S. A Exclude R X,Y Here, in one example, "J" can be defined as "0, 1, ... or (C)". RESEL -1)(Refer to Table 2). Here, “RR_INVTX” can represent the “resource reservation interval” of the V2X TX UE (set from the upper layer (or notified by signaling)), and “I_CANVAL” can be (specifically) regarded as a value belonging to the selectable (or permissible) “I_VALUE set” specified (previously) in the form of “carrier( / pool) specific network(pre)configuration”. Here, if the above rules are applied and it is determined whether (additionally) from S A Set exclusion R X,Y (Because no V2X message transmission operation monitoring resources were detected from the V2X TX UE in step 2 (e.g., subframe #) If so, only the (actually) selectable (or permissible) "I_VALUE set" (and / or "resource reservation interval") from a specific carrier (or pool) can be considered.

[0345] Subsequently, the UE can perform V2X communication S2620 based on the selected subframe. As described above, the selected subframe (or resource) can indicate resources determined based on a selection window constructed within the range that meets the latency requirements (i.e., resources on the selection window that meet the latency requirements). Additionally, as described above (below), the UE can select a subframe within the selection window based on sensing results obtained by performing sensing during a specific sensing period of the UE, determine transmission reserved resources based on the selected subframe, and perform V2X communication on the reserved resources. As described above, the UE performing V2X communication on a subframe can indicate performing V2X communication on a subframe reserved in conjunction with the subframe selected by the UE. Specific examples of the UE performing V2X communication based on the selected resources are the same as described above (or below), and their detailed description will be omitted.

[0346] As another example, in step 5 of Table 2, if no subframe is detected from the V2X message transmission operation of the V2X TX UE in step 2 # (and / or if due to V2X message transmission operation, no subframe # Performs PSCCH decoding and (associated) PSSCH DM-RS RSRP (and / or S-RSSI) measurement operations related to other V2X TX UEs and belongs to S A R X,Y R in X,Y+RR_INV*TjX With subframe # (and / or subframe#) If resources (partially reserved) that can be selected (or reserved) by other V2X TX UEs overlap, then the V2X TX UE can (additionally) access resources from set S. A Exclude R X,Y Here, "I_CANVAL_X" can be set (or signaled) to the maximum (or minimum or specific) value among the selectable (or permissible) "I_VALUE set" values ​​specified in the form of "carrier( / pool) specific network(pre)configuration". Here, as another example, in step 5 of Table 2, if no subframe # is detected from the V2X message transmission operation of the V2X TX UE in step 2... (and / or if due to V2X message transmission operation, no subframe # Performing PSCCH decoding and (associated) PSSCH DM-RS RSRP (and / or S-RSSI) measurement operations related to other V2X TX UEs allows the V2X TX UE to (additionally) access the set S A Exclude R X,YHere, in one example, “(N-1001)≤(Y-I_CANVAL*P_STEP)≤(N-2)” (wherein one example, subframe #N time point can be interpreted as the time when (transmission) resource (re)reservation (or selection) is set (or signaled) for execution (by the upper layer)) (and / or “P_STEP=100”). In another example, in step 5 of Table 2, if subframe # is not detected from the V2X message transmission operation of the V2X TXUE in step 2... (and / or if due to V2X message transmission operation, no subframe # Performing PSCCH decoding and (associated) PSSCH DM-RS RSRP (and / or S-RSSI) measurement operations related to other V2X TX UEs allows the V2X TX UE to (additionally) access the set S A Exclude R X,Y Here, in one example, “(N-1001)≤(Y-I_CANVAL_Q*P_STEP*K)≤(N-2)” (where in one example, subframe #N time point can be interpreted as the time when (transmission) resource (re)reservation (or selection) is set (or signaled) for execution (by the upper layer)) (and / or “P_STEP = 100”), and / or can be defined such that “K = non-negative integer”. Here, “I_CANVAL_Q” can be set (or signaled) to a value (and / or minimum value (or maximum or specific value among the values ​​in the selectable (or allowable) “I_VALUE set)” that belongs to (previously specified in the form of “carrier( / pool) specific network(pre)configuration”). Here, if the above (partial) rules are applied and it is determined whether (additionally) from set S A Exclude R X,Y(Additionally), then (A) the J value is assumed to have (only) a specific value (e.g., "J=1 (or 0)") previously set (or signaled) (and / or "RR_INVTX*J" (or "P_STEP*J") becomes the same J value (or a value less than (or greater than) or equal to a corresponding derived J value) as a (maximum (or minimum)) "resource reservation interval" (or a specific "resource reservation interval" previously set (or signaled)) (on a specific carrier (or pool)) (actually) selectable (or allowable), and / or (B) the RR_INVTX value is assumed to have (only) a specific value (e.g., "RR_INVTX=1000ms") previously set (or signaled) (and / or a (maximum (or minimum)) "resource reservation interval" (or a value less than (or greater than) or equal to a corresponding maximum (or minimum) "resource reservation interval") (on a specific carrier (or pool)) (actually) selectable (or allowable)). Here, the proposed method can be limitedly applied only when a priority related to a message (or packet) to be transmitted by the V2X TX UE (and / or a congestion level value related to a (corresponding) carrier (or pool)) is less than (or greater than) a pre-defined (or signaled) threshold value.

[0347] (Example #8) In one example, a method of effectively reflecting resources (or subframes) not monitored (or sensed) due to a transmission operation (of a V2X UE) in a "(PSSCH-RSRP measurement based) resource exclusion procedure" will be described below.

[0348] When a single transmission of a TB is performed by other UEs at subframe #k, it can be difficult to obtain accurate information of PSSCH-RSRP on the skipped subframe #k. Thus, if subframe #(y+P*j) overlaps subframe #(k+100*i), UE #A can consider excluding subframe #k present within the selection window of the UE. At this time, as described above, P can denote a resource reservation interval of the UE, and j can assume 0, 1, …, 10*SL_RESOURCE_RESELECTION_COUNTER-1. In addition, i can indicate a (possible) element in a set limited by a carrier-specific network (pre-)setting.

[0349] Here, in one example, (when there exist (A) a V2X UE (and / or a V2X UE performing transmission of a V2X message (or traffic) having a (relatively) short period) having a "short resource reservation period (or interval) on a (pre-defined (or signaled) (specific) resource pool" (SHORTP_UE) and (B) a V2X UE (and / or a V2X UE performing transmission of a V2X message (or traffic) having a (relatively) long period) having a "(relatively) long resource reservation period (or interval)" (LONGP_UE) together), (A) if the SHORTP_UE performs a sensing operation, and / or (B) if the LONGP_UE performs a sensing operation (with respect to the SHORTP_UE), the value "100" in "subframe #(K+100*I)" can be set to a different value (pre-defined (or signaled)).

[0350] In conjunction with the above-described method, the UE #A can exclude all resources (within the selection window of the UE) that overlap with transmissions of other UEs that can be scheduled from the skipped subframe #k. Hereinafter, the above-described operation will be described with reference to the related drawings.

[0351] Figures 28 to 30 An example of reflecting resources in the "(PSSCH-RSRP measurement based) resource exclusion procedure" is shown.

[0352] Referring to Figures 28 to 30 , i can be limited to a set such as {2, 4}, and P and SL_RESOURCE_RESELECTION_COUNTER can be set to 200 ms and 5, respectively.

[0353] In the case of Figure 28 , due to "subframe #(k+100*2) (i.e., i=2) and subframe #(y+200*0) (i.e., j=0)" and "subframe #(k+100*4) (i.e., i=4) and subframe #(y+200*1) (i.e., j=1)", the subframe #k can be excluded from selection (within the selection window).

[0354] In the case of Figure 29 , due to "subframe #(k+100*4) (i.e., i=4) and subframe #(y+200*0) (i.e., j=0)", the subframe #k can be excluded from selection (within the selection window).

[0355] However, in the case of Figure 30 , since there is no subframe belonging to the selection window that occurs the above-described overlap, the subframe within the selection window can not be excluded from selection.

[0356] As a result, the following method is provided.

[0357] Proposal: To handle the skipped subframe #k in the resource exclusion procedure (due to the transmission of V2X UE), the following solution can be proposed. If subframe #(y+P*j) can overlap with subframe #(k+100*i), UE #a can have to exclude subframe #y within the selection window of UE #a. Here, P can represent the resource reservation interval of UE, j = 0, 1, …, (10*SL_RESOURCE_RESELECTION_COUNTER-1), and i can represent all (possible) elements in the set of (pre-)configured limit by the network of each carrier.

[0358] As another example, if the bitmap with a (pre-defined (or signaled) (specific) length (e.g., “16”, “20”, “100”) is repeatedly applied for the V2X resource pool configuration, it can cause the problem that the (application of) corresponding bitmap is “cut off” at the “DFN range end” (in particular, because the (candidate) subframes configured (or signaled) as V2X resource pool are excluded from the subframes configured (or signaled) for SLSS transmission). Here, to solve the corresponding problem, the (existing) “DFN range” value (e.g., “10240” or “10176”) can be increased (which can be interpreted in the form of so-called HYPER-SFN (or HYPER-DFN), for example). Here, the (increased) “(maximum) DFN range” value can be defined in the form of “10240 (or 10176)*H_VAL” (or “10240 (or 10176)*H_MAXVAL”) (and / or “MAX DFN range*H_VAL” (or “MAX DFN range*H_MAXVAL”)). Here, in one example, (A) the (currently applied) H_VAL value (or index), (B) the configurable (or used) H_VAL (index) range, and / or (C) the maximum value (or maximum index) of H_VAL (H_MAXVAL) (and / or the minimum value (or minimum index) (H_MINVAL)) can be pre-defined (or signaled) by the network (or serving cell) through the pre-defined (upper (or physical) layer) signaling (and / or through the (newly defined) field on PSBCH by (synchronization source) UE (or through the pre-defined D2D channel or signal) in the form of “carrier (or pool or cell) specific (pre-)configuration” and / or as a kind of “V2X pool (pre-)configuration”.

[0359] Figure 31One example showing a case where an (existing) "DFN range" value (e.g., "10240" or "10176") is increased. Here, it is assumed that an H_VAL (and / or H_MAXVAL) value is set to "5" (which is denoted as "H," for example). Here, the H_VAL value (and / or H_MAXVAL) (and / or a V2X resource pool configuration (or signaling) related bitmap value) can be (in a limiting manner) set (or signaled) such that the (increased) "(maximum) DFN range" value can be evenly divided by (without a remainder) a V2X resource pool configuration related (set (or signaled) bitmap length) (and / or such that (on (all) subframes of a V2X resource pool) a (maximum (or minimum) or pre-defined (or signaled) "resource reservation interval" (e.g., "100 ms") corresponding to (an actual) selectable (or allowable) multiple (on a particular carrier (or pool)) can be (properly) "wrapped around"). If the above rule is applied, each time the "(maximum) DFN range" value (e.g., "1024 (or 10240") is reached, the V2X UE increases the H_VAL value by a pre-defined (or signaled) value (e.g., "1") and uses (or considers) (V2X) subframes in an ascending order of index for (V2X message) transmission (and / or V2X communication) starting from a relatively small value within a (V2X) subframe set based on the same H_VAL value. As another example, in a sensing operation, a "subframe index" is used using a "logical index" within a (V2X) resource pool. Here, in one example, when a "TDM" scheme is applied to (pre-defined) other signals and (V2X) resource pools, a physical time interval can become relatively large. In this case, the V2X TX UE can make a smaller value for a "resource reservation interval."

[0360] Further, when the above rule is applied (e.g., as described above, when an (existing) "DFN range" value (e.g., "10240" or "10176") is increased (which can be interpreted as a HYPER-SFN (or HYPER-DFN) method, for example)), V2X communication can be performed as follows.

[0361] (A) (e.g., when a bitmap of V2V subframes is not repeated an integer number of times during a DFN period of [RAN1, RAN2]), V2V can be performed by multiplexing with other signals or channels.

[0362] (B) Currently, according to SLSS resource configuration, a DFN range of V2V (i.e., Tmax representing the number of subframes that can be allocated for V2V) can be 10240 or 10176.

[0363] Furthermore, the length of the bitmap representing the V2V subframes for the resource pool can be 16, 20 or 100. Thus, as mentioned above (e.g., in Figure 22 case), there can be cases where the DFN range is not exactly divisible by the bitmap length unit.

[0364] A basic solution to this problem can be to change the DFN range (i.e., Tmax) such that the DFN range can always be exactly divisible by the bitmap length. This can involve extending the DFN range such that it can be a multiple of the bitmap length. Thus, in order to extend the SFN range, the concept of a "hyper-SFN (H-SFN)" can be introduced.

[0365] Here, if the H-SFN is provided by SystemInformationBlockType1-BR, the boundary between the modification period of the BL UE within the CE and the UE can be defined by the SFN value, expressed as (H-SFN*1024+SFN) mod m=0. Here, the H-SFN can always be provided with respect to NB-IoT, and the modification period boundary can be defined by the SFN value, expressed as (H-SFN*1024+SFN) mod m=0. The modification period can be configured by system information.

[0366] In order to allow informing the RRC_IDLE UE with an eDRX period longer or equal to the modification period about a system information update, an eDRX acquisition period can be defined. The boundary of the eDRX acquisition period can be determined by the H-SFN value, expressed as H-SFN mod 256=0. In particular, in the case of NB-IoT, the boundary of the eDRX acquisition period can be determined by the H-SFN value, expressed as H-SFN mod 1024=0.

[0367] Figure 32 One example of sending updated system information is shown.

[0368] Referring to Figure 32 If the network changes (part of) the system information, the network can first inform the UE about this change. At the next modification period, the network can send the updated system information. If the update notification is received, the UE can obtain the new system information immediately from the next modification period using a DRX cycle shorter or equal to the modification period.

[0369] The sent system information (i.e., SystemInformationBlockType1) can be defined as shown in Table 3 below.

[0370]

[0371]

[0372] Here, "hyperSFN" denotes a hyper SFN that is increased by one each time the SFN wraps around, and the presence of the "eDRX-Allowed" field indicates whether DRX with extended idle mode is allowed in the cell. If eDRX is not allowed, the UE must stop using DRX in extended idle mode.

[0373] By applying a similar principle, the DFN range can be extended by defining a "hyper DFN". (In other words, in addition to the SLSS subframes, ) the V2V subframe index in the logical domain can be given by (H-DFN*T max +DFN).

[0374] H max The maximum value of H-DFN can be configured such that it can be exactly divided by the length of the bitmap of (total number of potential V2V subframes). max *T max .

[0375] Figure 33 One example of hyper DFN is shown.

[0376] In this example, H max may be set to 5. (In other words, H-DFN#5 is reset to H-DFN#0.) To support hyper DFN, the current H-DFN index needs to be synchronized not only among UEs sharing the same resource pool, but also between the eNB and the UE. The H-DFN index can be signaled between the eNB and the UE as part of the resource pool and signaled through the PSBCH. When GNSS is the synchronization reference, the H-DFN index can be derived from the current UTC value.

[0377] (C) Summary,

[0378] Hyper DFN can be proposed to handle discontinuity in repetition of the subframe bitmap as follows.

[0379] Proposal 1: Hyper DFN can be defined to increase the DFN range by H max amount. The V2V subframe index in the logical domain can be given by (H-DFN*T max +DFN), whereby H-DFN is increased by one after T max subframes, where H-DFN = 0, 1,..., H max - 1.

[0380] Proposal 2: H max may be set to the value obtained by dividing H max *T max by the length of the V2V subframe bitmap of the resource pool.

[0381] Proposal 3: The current H-DFN can be signaled from the eNB as part of the elements constituting the resource pool. And the current H-DFN can also be signaled through the PSBCH.

[0382] As another example, in the above example, the H max The value (without additional signaling) can be fixed (on the specification) as a predefined value. Here, the H max The value can be fixed as "25" (or a multiple of "25"). Table 4, Table 5, and Table 6 show analysis data related to the above description.

[0383]

[0384]

[0385]

[0386]

[0387]

[0388]

[0389]

[0390]

[0391]

[0392] As another example, (A) when a bitmap having a predefined (or signaled) (specific) length is repeatedly applied to designate a V2X resource pool and / or (B) when (periodic) transmission resources on a "resource reservation interval" (set (or signaled) from an upper layer (of the UE)) are reserved (or selected), (part of) V2X resources designated by the (corresponding) bitmap and / or (part of) (periodic) transmission resources (reserved (or selected) by the V2X TX UE) can be located on WAN communication related DL (time (or frequency)) resources (e.g., "DL SF and / or" (TDD) special SF" (and / or "DWPTS")).

[0393] Further, when the UE performs V2X message transmission on a specific carrier, the UE can not perform V2X message transmission using all subframes on the carrier. In this regard, a method of transmitting a V2X message will be described with reference to the related drawings by considering subframes in which the UE does not perform V2X message transmission.

[0394] Figure 34 is a flowchart of a method of performing V2X communication on an allocated V2X resource pool according to an embodiment of the present application.

[0395] Referring to Figure 34 , the UE can allocate a V2X resource pool to the remaining subframes except for a specific subframe S3410. At this time, the specific subframe can mean (A) an SLSS subframe, (B) a DL and S (special) subframe in the case of a TDD shared carrier, or (C) a reserved subframe. Hereinafter, a more specific example of excluding a subframe from V2X transmission will be described.

[0396] (A) Regarding SLSS subframe

[0397] First, the UE can allocate a V2X resource pool to the remaining subframes except for an SLSS subframe.

[0398] More specifically, the SLSS subframe can be excluded from the mapping according to a (repeated) V2V pool bitmap (i.e., a bitmap (or information) indicating a subframe to which a V2X pool can be allocated), at this time, the bitmap length can be 16, 20, or 100. The bitmap can define which subframe allows V2V SA and / or data transmission and / or data reception. An example of excluding the SLSS subframe from V2X transmission will be described as follows.

[0399] Figure 35 An example of excluding the SLSS subframe from V2X transmission is shown.

[0400] Figure 35 Assuming that a subframe number can have values 0, 1, …, 10239 (i.e., a total of 10240 subframes), a V2X bitmap is repeated in units of 10 subframes, and the V2X bitmap is [0110101101].

[0401] When allocating a V2X logical index, the UE can allocate a V2X logical index with respect to a subframe except for an SLSS subframe. For example, if it is assumed that subframe indexes #3, #163, etc. correspond to an SLSS subframe (where the SLSS subframe is repeated in units of 160 subframes), a V2X UE can allocate a V2X logical index to the remaining subframes except for the subframe indexes #3, #163, etc. (i.e., the remaining subframes except for the SLSS subframe) (S3510). Here, it can be assumed that a V2X resource is allocated with respect to a subframe allocated by a V2X logical index according to a V2X bitmap.

[0402] At this time, the V2X logical index derived through the above-described process can not correspond to an integer multiple of the V2X bitmap. For example, when the SLSS subframe is allocated in units of 160 subframes, 64 SLSS subframes can be defined among 10240 subframes as described above, and thus a V2X logical index can be allocated to 10176 subframes corresponding to 10240-10264.

[0403] As described above, when it is assumed that V2X logical indexes can be assigned to 10176 subframes and a V2X bitmap period is 10, the logical indexes are not exactly divided by the V2X bitmap period. In other words, when a V2X bitmap having a period of 10 is assigned to 10176 subframes, there can be a possibility that bits are not assigned to 6 subframes.

[0404] Accordingly, the UE can exclude, from the assignment of the V2X logical indexes, as many subframes as the number of unassigned subframes S3520. At this time, the unassigned subframes can be evenly distributed.

[0405] (B) Regarding DL and special (S) subframes

[0406] In the case of a TDD (shared) carrier, due to a (repeated) V2V all-bitmap, DL and / or special (S) subframes can be excluded from the mapping. Examples of excluding DL and / or special (S) subframes from V2X transmission will be described below with reference to the relevant drawings.

[0407] Figure 36 An example of excluding DL and S subframes from V2X transmission is illustrated.

[0408] Figure 36 It is assumed that subframe numbers can have values 0, 1, …, 10239 (i.e., a total of 10240 subframes), a V2X bitmap is repeated in units of 10 subframes, and the V2X bitmap is [0110101101].

[0409] When assigning V2X logical indexes, the UE can assign V2X logical indexes to subframes other than DL and / or special (S) subframes (and / or SLSS subframes). For example, if it is assumed that subframe indexes #7 (and the like) correspond to DL and special (S) subframes, the V2X UE can assign V2X logical indexes to the remaining subframes other than the subframe indexes #7 (and the like) S3610. Here, the UE can allocate V2X resources according to the V2X bitmap with respect to the subframes assigned by the V2X logical indexes.

[0410] Thereafter, the UE can additionally exclude, for the assignment of the V2X logical indexes, as many subframes as the number of unassigned subframes S3520. At this time, the unassigned subframes can be evenly distributed.

[0411] (C) In the case of reserved subframes

[0412] A resource pool is composed of a plurality of reserved subframes, such that a bitmap is repeated an integer number of times within a certain range (e.g., a D2D frame number (DFN) range). For example, V2X (e.g., V2V) logical subframe indexes can not be assigned to the reserved subframes. In addition, the positions of the reserved subframes can be implicitly marked.

[0413] In summary, a corresponding problem occurs due to the bitmap related to the V2X resource pool configuration being unconditionally applied to the WAN-communication-related DL / UL (time- or frequency-) resources except for the (pre-defined (or signaled) V2X synchronization signal transmission related (time- or frequency-) resources (e.g., V2X synchronization subframe) (and / or due to the DFN wrap-around problem (or phenomenon)). Here, to address the corresponding problem, the V2X TX UE can be caused to: (A) assume (part of) V2X resources (in terms of (V2X pool related) "logical index") on WAN-communication-related DL (time- or frequency-) resources (specified by the bitmap) as invalid; and / or (B) skip (V2X message (or TB)) transmission operation on (part of) (periodic) transmission resources (reserved (or selected) by the V2X TX UE) on WAN-communication-related DL (time- or frequency-) resources (and / or instead of skipping (V2X message (or TB)) transmission operation, (re-)perform (V2X message (or TB)) transmission operation on (the nearest) valid (or available) V2X resources after the transmission operation). Here, in the former case, the (V2X pool related) "logical index" can be considered to be performed by including (or excluding) invalid resources (e.g., DL (time- or frequency-) resources) (e.g., when determining transmission timing of a certain period on "logical index", a problem that an actual transmission period becomes (excessively) larger than an expected (target) period can be mitigated). In another example, when a bitmap with a (certain) pre-defined (or signaled) length is repeatedly applied, WAN-communication-related DL (time- or frequency-) resources (e.g., "DL SF" and / or "(TDD) special SF" (and / or "DWPTS")) can be (further) excluded (e.g., it can be considered that (V2X pool related) "logical index" is not performed (or applied) on the corresponding resources (further) excluded), and the bitmap can be caused to be applied (by considering only WAN-communication-related UL (time- or frequency-) resources). Here, the rule can be limited to be applied only to "in-coverage" environments (and / or TDD systems).

[0414] Referring again to Figure 34 , the UE can perform V2X communication on the allocated V2X resource pool S2420. Specific examples of the UE performing V2X communication are the same as described above.

[0415] In one example, the rule can be extended to apply to the case where (part of) V2X resources (specified by bitmap) and / or (part of) (periodic) transmission resources (reserved (or selected) by V2X TX UE) are not only located on WAN communication related DL (time (or frequency)) resources, but also on resources where V2X communication is not properly performed (e.g., (time (or frequency)) resources other than "UL SF" (and / or "UPPTS")) (and / or resources where (specific) V2X channel (or signaling) transmission (or reception) is set with relatively higher priority (compared to the priority of V2X message to be transmitted)).

[0416] In another example, a V2X UE (in coverage of eNB) can be caused to transmit an "offset value for DFN#0 based on GNSS" previously signaled (or defined) by (serving) eNB to other V2X UEs (out of coverage of eNB) through a pre-defined channel (e.g., PSBCH).

[0417] In another example, if I_VALUE (range) values and / or "resource reservation interval" (range) values (in the form of "carrier ( / pool) specific network (pre-)configuration") that are selectable (or allowable) on a V2X resource pool (and / or (V2X) carrier) are limited, based on (A) a period value (e.g., "I_MINVAL*P_STEP") that can be derived (or calculated) from a minimum value (I_MINVAL) (or maximum value) of I_VALUE (or a (specific) I_VALUE pre-defined (or signaled)), and / or (B) a minimum (or maximum) period value of "resource reservation interval" (or a (specific) "resource reservation interval" value pre-defined (or signaled)), a V2X TX UE can be caused to perform a sensing operation (e.g., step 5 of Table 2) (and / or an energy measurement operation (e.g., step 8 of Table 2)) on a corresponding V2X resource pool (and / or (V2X) carrier). Here, when a (specific) V2X resource pool is set (or applied) only for a P-UE performing V2X message transmission with a relatively long period (e.g., "500ms") (compared to V-UE) and the above rule is applied, the P-UE performs a sensing operation (and / or an energy measurement operation) based on the (corresponding) period (e.g., "500ms").

[0418] Further, as described above, the UE can select a random value from an interval between 5 and 15 and reserve resources as many as the selected value multiplied by 10 in case of a relatively long resource reservation period (e.g., a resource reservation period longer than 100 ms) (referred to as "L_PER"). However, it can not be suitable for L_PER UEs to sense S_PER UEs existing in the same resource pool to apply the above-described resource reservation method to a case where a relatively short resource reservation period (e.g., 20 ms or 50 ms (shorter than 100 ms)) (referred to as "S_PER") is used.

[0419] In this regard, if a (relatively) "short resource reservation period (or interval)" (e.g., "20 ms") is employed in order for the UE to support transmission of a V2X message (or traffic) having a (relatively) short period, (part of) the following parameters can be differently (or independently) set (or signaled) when compared to transmission of a V2X message (or traffic) performed with a (relatively) long period (or a (threshold) period pre-defined (or signaled)). In one example, it can be interpreted that (part of) the following parameters are applied to a case where (A) SHORTP_UE performs a sensing operation and / or (B) LONGP_UE (relative to SHORTP_UE) performs a sensing operation (when a V2X UE having a "short resource reservation period (or interval)" (and / or a V2X UE performing transmission of a V2X message (or traffic) having a (relatively) short period) (SHORTP_UE) and a V2X UE having a "(relatively) long resource reservation period (or interval)" (and / or a V2X UE performing transmission of a V2X message (or traffic) having a (relatively) long period) (LONGP_UE) coexist on a pre-defined (or signaled) (particular) resource pool). Hereinafter, the present method will be described with reference to the related drawings.

[0420] Figure 37 is a flowchart of a method of performing reservation of a V2X transmission resource when a resource reservation is set with a relatively short period (e.g., 20 ms or 50 ms (shorter than 100 ms)) according to an embodiment of the present application.

[0421] Referring to Figure 37 When a resource reservation is set with a relatively short period, the UE can perform reservation of a relatively large amount of V2X transmission resources S3710. Here, reservation of a relatively large amount of V2X transmission resources does not indicate that a random number is selected from an interval between 5 and 15 and resources as many as the selected value multiplied by 10 are reserved as described above, but indicates that the UE selects a random value from an interval between 5*K (where K is a positive integer greater than or equal to 2) and 15*K and reserves resources as many as the selected value multiplied by 10.

[0422] In other words, in case of a relatively short resource reservation period (e.g., 20 ms, 50 ms), the above counter value (a value of 5 or more and 15 or less) is multiplied by 5 or 2, which is further multiplied by 10. Then, as many resources as the final multiplication result can be reserved.

[0423] For example, if the resource reservation period is "20 ms", the UE can select a random value from an interval of [5*5, 15*5] (in other words, 5*2 or more and 15*5 or less), and can reserve as many resources as the random number is additionally multiplied by 10. According to the present example, the UE can reserve more than 250 and less than 750 resources.

[0424] In another example, if the resource reservation period is "50 ms", the UE can select a random value from an interval of [5*2, 15*2], and can reserve as many resources as the random number is additionally multiplied by 10. According to the present example, the UE can reserve more than 100 and less than 300 resources.

[0425] (Example #1) A limited number of subframes (and / or C resel values (e.g., "[10*SL_RESOURCE_RESELECTION_COUNTER]") are assumed (or used) when performing transmission resource (re)reservation (or selection) with a resource reservation (interval) period. Here, in case of transmission of a V2X message (or traffic) with a (relatively) short period, a corresponding limited number of subframes (and / or C resel values) with a relatively small number (which, for example, provides an effect of preventing excessive resource reservation (or selection) from being performed (in a short period of time)) can be set (or signaled).

[0426] Thereafter, the UE can perform V2X communication on the reserved V2X transmission resource S3720. Specific examples in which the UE performs V2X communication on the reserved V2X transmission resource are the same as described above.

[0427] Figure 38 is a flowchart of a method of performing sensing with a relatively short period when setting resource reservation with a short period according to an embodiment of the present application.

[0428] Referring to Figure 38If the resource reservation with a short period is configured, the UE performs sensing in a relatively short period in the sensing period to determine a resource S 3810 for performing V2X communication. In other words, as described above, if the resource reservation with a short period is configured (e.g., when the resource reservation is configured with a period shorter than 100 ms), the sensing (i.e., S-RSSI measurement) period can be configured as the resource reservation period for UE transmission. In other words, if the resource reservation is configured with a short period, the UE can perform sensing according to the short period for the resource reservation. Hereinafter, the above-described operation will be described in more detail.

[0429] (Example #2) V2X message priority (which may, for example, be configured (or signaled) with a relatively low (or high) priority) and / or "PSSCH-RSRP measurement" threshold in Step 5 of Table 2 (and / or "0.2*M total " correlation (or ratio) (which may, for example, be interpreted as a ratio for deriving (or determining) a minimum number of (candidate) resources that must be reserved in S A set after performing Step 5 of Table 2 (among all (candidate) resources) and / or a ratio for deriving (or determining) a (minimum) number of (candidate) resources that must be reserved in S B set after performing Step 8 of Table 2) can be configured (or signaled) to have different (or independent) values, and / or "PSSCH-RSRP measurement" increase (e.g., "3DB") and / or period value (and / or period value used for an energy measurement operation (e.g., Step 8 of Table 2) for a sensing operation (e.g., Step 5 of Table 2) (e.g., in Step 8 of Table 2, the value "100 ms" can be changed (to a relatively short (or long) value)) can be configured (or signaled) to have different (or independent) values when a minimum number of (candidate) resources that must be reserved within S A set after performing Step 5 of Table 2 (among all (candidate) resources) is not satisfied.

[0430] (Example #3) I_VALUE (range) and / or P_STEP value selectable (or allowable) on a V2X resource pool (and / or (V2X) carrier)

[0431] (Example #4) (Open-loop) parameter (or value) related to transmission power (e.g., "P o ", "ALPHA") and / or V2X resource pool (or carrier)

[0432] As another example, a V2X UE can be caused to perform (transmission) resource (re)selection as follows.

[0433] A V2X UE can select a transmission resource using the following method.

[0434] It is assumed that the UE operates in a mode where the UE itself performs resource selection. In the above mode, if resource selection / reselection for V2X message transmission is triggered, the UE can perform sensing and select or reselect resources based on the sensing result. The UE can transmit a scheduling assignment (SA) indicating the selected or reselected resources.

[0435] For example, in subframe (hereinafter, can also be referred to as TTI) #n, resource selection or reselection can be triggered for the UE. Then, the UE can perform sensing between subframe #n-1 and subframe #n-a (where a > b > 0, a and b are integers), and select or reselect resources for V2X message transmission based on the sensing result.

[0436] a and b can be values set commonly for V2X UEs, or values set independently for each V2X UE.

[0437] When a and b are common to V2X UEs, for example, a relationship such as "a = 1000 + b" can be maintained. In other words, if the UE is triggered to select resources for V2X message transmission by itself, the UE can perform a sensing operation for 1 second (1000 ms = 1000 subframes = 1000 TTIs).

[0438] The UE can consider all SA transmissions decoded over a period from subframe #n-a to subframe #n-b. The decoded SA can be associated with data transmissions over a period from subframe #n-a to subframe #n-b, wherein the decoded SA can consider data transmitted before subframe #n-a.

[0439] The UE that fails to perform a sensing operation in subframe #m can exclude subframe #(m+100*k) from resource selection or reselection (because a signal must be transmitted from subframe #m). In addition, the UE can skip subframes for transmitting a signal without performing a sensing operation.

[0440] After performing sensing, the UE can select time or frequency resources for PSSCH (i.e., a sidelink data channel).

[0441] The UE can transmit a scheduling assignment (SA) from subframe #n+c. c is an integer greater than 0, which can be a fixed value or a variable. For subframes for which the value of c is less than c min , the UE can not be required to transmit a scheduling assignment (i.e., PSCCH transmission). c min may be a fixed value or set by the network.

[0442] The scheduling assignment (SA) transmitted from subframe #n+c can indicate associated data transmitted from subframe #n+d. d can be an integer greater than or equal to c (d ≥ c). Both c and d can be values less than or equal to 100.

[0443] In addition, if any of the following conditions is met, reselection of V2X resources can be triggered.

[0444] (A) In case the counter meets the termination condition

[0445] The counter decreases its value each time a transport block is transmitted and can be reset if reselection is triggered for all semi-statically selected resources. The reset value can be randomly (e.g., with equal probability) selected between 5 and 15.

[0446] (B) In case the transport block does not fit into the current resource allocation even using the maximum modulation and coding scheme (MCS) allowed

[0447] (C) In case reselection is indicated by the upper layer

[0448] In addition, if all PSCCH or PSSCH transmissions have the same priority, the selection or reselection of PSSCH resources can be performed by the following steps.

[0449] (A) Step 1:

[0450] First, assume that all resources are selectable anyway.

[0451] (B) Step 2:

[0452] Specific resources are excluded based on the scheduling assignment decoding and additional conditions. At this point, the UE can select one of the following two options.

[0453] The first option excludes resources indicated or reserved by the decoded scheduling assignment and resources for which the DM-RS power received from the data resources associated with the scheduling assignment is greater than a threshold.

[0454] The second option excludes resources indicated or reserved by the decoded scheduling assignment and resources for which the energy measured from the data resources associated with the scheduling assignment is greater than a threshold.

[0455] (C) Step 3:

[0456] The UE can select a V2X transmission resource among the resources that have not been excluded.

[0457] For example, after measuring the remaining PSSCH resources and ranking them based on the total received energy, the UE can select a subset. The UE can compare the energy of the currently selected resource with the energies in the subset and select one from the subset if the energy in the currently selected resource is greater than a threshold with respect to the energies in the subset. The UE can randomly select one resource from the subset.

[0458] Similarly, after measuring the remaining PSSCH resources and ordering based on total received energy, the UE can select a subset. The UE can randomly select one resource from the subset.

[0459] Similarly, after measuring the remaining PSSCH resources and ordering based on total received energy, the UE can select a subset. The UE can randomly select one resource from the subset that minimizes fragmentation of frequency resources.

[0460] In one example, when performing (transmission) resource (re)selection operation according to Table 2, the following (partial) rules can additionally be applied.

[0461] [Proposal Rule #10] In one example, according to the “delay (or QoS) requirement” (and / or the “priority” and / or the “service type” of the (to-be-transmitted) generated packet), which can be interpreted as a (maximal (or minimal)) range of (D or C-M) (which can be interpreted as a “TX resource (re)selection duration (or range or window”), for example), (M) is the (lower layer) buffer (and / or the time point at which the (to-be-transmitted) generated packet (or message) arrives (or is received) (on the “PDCP layer”)) (or the time point at which the packet (or message) is generated), for example. In addition, the word “D (or C)” (here) can indicate that the resource (re)selection (or reservation) operation is (exceptionally) triggered differently (which can be regarded as the transmission time point of (initial) data (PSSCH) (or control information (PSCCH)) after subframe #N), for example. In another example, the “C” and / or “D” ((maximal (or minimal)) range) (which can be interpreted as a “TX resource (re)selection duration (or range or window”), for example) must be determined to satisfy (or take into account) the “delay (or QoS) requirement”, which can be different according to the “service type” (and / or the “priority level”). Here, the “upper (or lower) bound” of “C” and / or “D” (which can be interpreted as a “TX resource (re)selection duration (or range or window”), for example) can not be fixed. Here, the corresponding “upper (or lower) bound” can be set (or signaled) differently according to the “priority level” (and / or the “service type” and / or the “delay (or QoS) requirement”). Here, if the currently selected “D” value (or “subframe #D”) is problematic in terms of satisfying the “delay (or QoS) requirement” of the newly arrived (or generated (or received)) packet (or message), the (transmission) resource (re)selection operation can be triggered. In one example, the maximum (and / or minimum) value or range of the “D” (and / or “C”) value (which can be interpreted as a “TX resource (re)selection duration (or range or window”), for example) can be determined by taking into account the (lower layer) buffer (and / or the time point at which the (to-be-transmitted) generated packet (or message) arrives (or is received) (on the “PDCP layer”)) (or the time point at which the packet (or message) is generated) (“M”), and / or the time point at which the (transmission) resource (re)selection operation is triggered (when a pre-defined (or signaled) condition is satisfied) (“N”), and / or the “delay requirement” (“L”) (e.g., “100 ms”), and / or the “PPPP” of the packet (or message) (when (partially) different “PPPP” values are set (or allowed) for individual packets (or messages) of different “delay requirements”), for example.As a specific example, the maximum (and / or minimum) value of “D” (and / or “C”) can be determined by “(L-ABS(M-N))” or “MIN(L,(L-ABS(M-N)))” (where, for example, “MIN(X,Y)” and “ABS(Z)” represent a function that returns the minimum value between “X” and “Y”, and a function that returns the absolute value of “Z”, respectively), or the range of “D” (and / or “C”) can be specified by “(L-ABS(M-N)) < D( / C) < 100 (or “delay requirement”)” (or “(L-ABS(M-N)) ≤ D( / C) ≤ 100 (or “delay requirement”)”). In one example, considering retransmission of a particular (one) “TB (or packet or message)”, a pre-defined (or signaled) “margin (or offset)” value (“MAG_VAL”) can have to be subtracted from the “L” value when calculating (or determining) the maximum (and / or minimum) value of “D” (and / or “C”). The maximum (and / or minimum) value of “D” (and / or “C”) can be determined as “((L-MAG_VAL)-ABS(M-N))” or “MIN((L-MAG_VAL),((L-MAG_VAL)-ABS(M-N)))” when the corresponding rule is applied. Here, the “MAG_VAL” value can have “dependency” on the number of retransmissions (e.g., the “MAG_VAL” value increases as the number of retransmissions increases). The rule can be limited to be applied only to the case where the “(transmission) resource (re)selection operation” is triggered (if the (pre-defined (or signaled) condition) is met), and there is (generated) packet (or message) (or when the packet (or message) is generated) on the “(lower layer) buffer” (and / or “PDCP layer”) (to be transmitted).In another example, when there is no (generated) packet (or message) (to be transmitted) on the (lower) buffer (and / or the PDCP layer) (or when there is no generated packet (or message)) although the (transmission) resource (re)selection operation is triggered (if the (pre-defined (or signaled) condition) is met), the (transmission) resource (re)selection operation can be performed by assuming (or considering) that "(N=M)" (which can be interpreted as, for example, the time ("N") at which the (transmission) resource (re)selection option is triggered is assumed (or considered) to be the time ("M") at which the (generated) packet (or message) (to be transmitted) is received on the (lower) buffer (and / or the PDCP layer)), or by postponing the (transmission) resource (re)selection operation until the (generated) packet (or message) (to be transmitted) actually arrives (or is received) on the PDCP layer (or until the packet (or message) is actually generated), or by assuming that the (generated) packet (or message) (to be transmitted) has arrived (or has been received) on the PDCP layer (or exists) (including (or not including) the time point "N" previously) (or the packet (or message) has been generated). As another example, the subsequent resources including (or not including) the time point corresponding to the maximum of (the above) "D" (and / or "C") (e.g., "(L-ABS(M-N))", "100 (or "delay requirement)") are assumed (or considered) to be unavailable, and can be excluded (from the (re)selectable candidate resources) (on "step 3 (or 2)"). In an additional example, the resources at the time point corresponding to the minimum of "C" (and / or "D") (C_MIN) (e.g., the "minimum" can be determined by taking into account the "processing time" of the UE (e.g., "4ms")) (e.g., the resources before the time point including (or not including) "(C+C_MIN)" (or the resources between the time point "N" and the time point "(C+C_MIN)" (here, in one example, the resources corresponding to the time points "N" and "(C+C_MIN)" can be included (or can not be included))) are assumed (or considered) to be unavailable, and can be excluded (from the (re)selectable candidate resources) (on "step 2 (or 3)").In another example, according to the (partial) proposal rules (e.g., [Proposal Rule #1] and [Proposal Rule #10]) of the present application, when the "TX resource (re)selection duration (or range or window)" ((max (or min) range) is differently set (or changed) by considering the "priority level" (and / or "service type" and / or "delay (or QoS) requirement"), according to whether a pre-defined condition is met, the following (partial) parameters related to the sensing operation (and / or (transmission) resource (re)selection (or reservation) operation (and / or V2X message transmission). Here, the (corresponding) condition can be defined as (A) the case of transmitting a V2X message having a "delay requirement" shorter (or longer) than a pre-defined (or signaled) threshold (and / or the case of transmitting a V2X message having a "PPPP" higher (or lower) than a pre-defined (or signaled) threshold), and / or (B) the case where the number of (selectable) (candidate) resources (e.g., subframes) existing (or reserved) within the "TX resource (re)selection duration (or range or window)" is less than (or more than) a pre-defined (or signaled) threshold (and / or the case where the minimum (or maximum) value of the "TX resource (re)selection duration (or range or window)" is less than (or greater than) a pre-defined (or signaled) threshold).

[0462] (Example #10-1) In case of a V2X message with a "delay requirement" shorter (or longer) than a (V2X message related) PPPP value (or range) (e.g., a pre-defined (or signaled) threshold), a corresponding transmission can be ensured by selecting a relatively high (or low) PPPP value (or range). Here, in case of a transmission based on a high (or low) PPPP value (or range), it is determined based on a relatively low (or high) PSSCH-RSRP threshold whether resources used for a corresponding transmission by other UEs are selectable (or idle or busy) (and / or in case of a V2X message with a "delay requirement" longer (or shorter) than a pre-defined (or signaled) threshold, even if the "delay requirements" have the same PPPP value (or range), by setting (or signaling) a relatively low (or high) PSSCH-RSRP threshold, a V2X message transmission with a "delay requirement" shorter (or longer) than a pre-defined (or signaled) threshold can be ensured). And / or when a minimum ratio (or number) of candidate (transmission) resources needed to be reserved after performing a candidate (transmission) resource exclusion operation based on a sensing operation execution interval (or period) (and / or a corresponding ratio (or number) of remaining candidate (transmission) resources) is smaller than a pre-defined (or signaled) threshold, and / or (a (maximum (or minimum)) period (or range) of selectable candidate (transmission) resources (selection window) and / or a determination (or selection) of a random value to define a range of a maintenance interval of (re)selected (or reserved) resources (and / or a multiplication with a corresponding selected random value (to be used for deriving a C RESELa minimum ratio (or number) of candidate (transmission) resources that must be reserved after performing the candidate (transmission) resource exclusion operation based on the PSSCH-RSRP threshold value, and / or (B) a ratio (or number) of corresponding remaining candidate (transmission) resources is less than a pre-defined (or signaled) threshold value, a minimum ratio (or number) of candidate (transmission) resources that must be reserved after performing the candidate (transmission) resource exclusion operation based on the PSSCH-RSRP threshold value, and / or (C) S-RSSI can be set to a relatively high value (which e.g. brings an increased effect of mitigating collision probability). And / or a CBR threshold value for determining whether a (sub-)channel is busy (or idle) and / or a set of allowed (or limited) radio layer parameters (e.g. maximum transmission power, number of retransmissions per TB (range), MCS value (or range), maximum limit of occupancy ratio (CR_LIMIT), etc.) [1 / 2 / 3] for each PPPP / CBR.

[0463] [Proposal Rule #11] In one example, a “(timer) expiry condition” related to (transmission) resource (re-)selection can be defined as a condition that (simultaneously) satisfies (part of) the following conditions. In one example, this rule can be interpreted as (in fact) (considering (or assuming) that a (transmission) resource (re-)selection operation has been triggered) only when (part of) the following conditions are simultaneously satisfied, such that a V2X UE performs a (transmission) resource (re-)selection operation.

[0464] Example #11-1) A case where a counter value (which decreases by a pre-defined value (e.g. “1”) for each TB transmission) changes to “0” (and / or a “negative integer value”).

[0465] (Example #11-2) A case where there is (a generated (or received) (to be transmitted) packet (or message) on the (lower layer) buffer (and / or the PDCP layer)

[0466] [Proposal Rule #12] In one example, while the counter value (which is reduced by a predefined value (e.g., "1") for each TB transmission) satisfies the "expiration condition" (e.g., the case where the counter value changes to "0" (and / or a "negative value")) (and / or the "(transmission) resource (re)selection operation" is triggered (if a predefined (or signaled) condition is satisfied)), if there is no (a generated (or received) (to be transmitted) packet (or message) on the (lower layer) buffer (and / or the PDCP layer) (or if the packet (or message) has not been generated yet), the V2X UE can be caused to assume that the (most recent) packet (or message) arrives (or is generated (or received)) at a previously (or recently) observed "interval (or periodicity)", and additionally perform the (transmission) resource (re)selection operation if (subsequently) a problem happens to actually occur after performing the (transmission) resource (re)selection (e.g., the case where the (re)selected (transmission) resource does not satisfy the "delay (or QoS) requirement").

[0467] In one example, the V2X UE can be caused to perform the (transmission) resource (re)reservation according to the following method (together with the rules described in Table 2).

[0468] d can be a value less than or equal to d max dmay be determined according to a priority such as a UE, data, or service type. max

[0469] The UE can inform whether the frequency resources used for a signal transmitted from subframe #n+d are reused for potential transmission of other transport blocks at subframe #n+e. Here, e is an integer, and d

[0470] A receiving UE receiving a V2X signal decodes a scheduling assignment (SA) transmitted by a transmitting UE transmitting the V2X signal. At this time, due to the scheduling assignment, it can be assumed that the same frequency resources can be reserved at subframe #n+d+P*j (j = I, 2*I,..., J*i). P can be a value of 100. The J value can be explicitly signaled through the scheduling assignment or be a fixed value (e.g., 1). The i value can be explicitly signaled through the scheduling assignment or be a predetermined or fixed value. Similarly, the i value can be an integer between 0 and 10.

[0471] [Proposal Rule #13] In one example, due to the V2X TX UE signaling the "I" value (refer to I above) through the SA (field), the V2X RX UE becomes able to figure out which time points the V2X TX UE (further) reserves (or uses) the same frequency resource indicated (or scheduled) through the (corresponding) SA (e.g., when the V2X TX UE signals the "I" value as "2", the V2X RX UE assumes that the same frequency resource indicated (or scheduled) through the (corresponding) SA on "TTI#(N+D)" and "TTI#(N+D+2*P)" has been reserved). In the following, for the convenience of description, it is assumed that the "I" value is selected from the pre-defined (or signaled) range "[0, 1, …, 10] (4 bits)" and / or the "J" value is fixed as "1" (refer to J above). In one example, when the V2X message generation period changes according to the pre-defined parameter (e.g., speed or (moving) direction change amount), it is difficult for the V2X TX UE to accurately predict the V2X message generation period, the reservation of (future) resources according to this method can not be efficient. As one approach to solve the corresponding problem, when a specific V2X TX UE signals the "I" value as "2" on the SA field, it is assumed that the same frequency resource (HARD_RSC) indicated (or scheduled) through the (corresponding) SA on "TTI#(N+D)" and "TTI#(N+D+2*P)" is reserved in a "definite (or hard)" manner, but the same frequency resource (SOFT_RSC) indicated (or scheduled) through the (corresponding) SA at the time points based on the remaining "I" values (e.g., "TTI#(N+D+1*P)", "TTI#(N+D+3*P)", "TTI#(N+D+4*P)", "TTI#(N+D+5*P)", "TTI#(N+D+6*P)", "TTI#(N+D+7*P)", "TTI#(N+D+8*P)", "TTI#(N+D+9*P)", "TTI#(N+D+10*P)") (which are not signaled through the SA (field)) is reserved in a "potential (or soft)" manner. Here, in one example, the corresponding rule (and / or SOFT_RSC reservation) can be applied only to a specific resource allocation mode (which, for example, can not be applied to the mode 1 based resource selection and / or the random resource selection (or partial sensing) of P-UEs). When the corresponding rule is applied, the V2X TX UE can be made to apply a different (DM-RS power or energy measurement) threshold pre-defined (or signaled) when determining whether the HARD_RSC and SOFT_RSC of other V2X TX UEs (determined based on the SA decoding) are selectable candidate resources or resources to be excluded (Step 2 of Table 2).In one example, a HARD_RSC related threshold (HARD_TH) can be set (or signaled) to be lower (or higher) than a SOFT_RSC related threshold (SOFT_TH) (which can be interpreted, for example, as HARD_RSC is protected with a relatively higher priority compared to SOFT_RSC). Here, the SOFT_RSC related threshold can be set (or signaled) in the form of an offset value (HARD_THOFF) relative to HARD_RSC (and / or the HARD_TH related threshold can be set (or signaled) in the form of an offset value (SOFT_THOFF) relative to SOFT_RSC). Here, in one example, (A) if HARD_THOFF is set (or signaled) to be “0”, the other V2X TX UEs determine whether to exclude HARD_RSC and SOFT_RSC (of the corresponding V2X TX UE) according to the “DM-RS power / energy measurement” values with the same priority (Step 2 of Table 2) (or interpreted as the (corresponding) V2X TX UE attempts to reserve the same frequency resources at the time point based on all “I” values set or scheduled by the SA), (B) if HARD_THOFF is set (or signaled) to be “infinity (or a relatively large value)”, the other V2X TX UEs always (or with a very high probability) determine SOFT_RSC (of the corresponding V2X TX UE) as a selectable candidate resource (Step 2 of Table 2). Here, in one example, (A) the V2X message priority of the other V2X TX UEs discovered from SA decoding (and / or the V2X message priority that the V2X TX UE itself attempts to send) and / or (B) the (corresponding) threshold (e.g., HARD_TH and SOFT_TH) (or the offset value (e.g., HARD_THOFF (or SOFT_THOFF)) set (or signaled) differently) and / or (C) the V2X message priority of the other V2X TX UEs figured out from SA decoding (and / or the V2X message priority that the V2X TX UE itself attempts to send) and / or (D) the (corresponding) threshold (e.g., HARD_TH and SOFT_TH) (or the offset value (e.g., HARD_THOFF (SOFT_THOFF))) can be adjusted according to the “congestion level”. Here, by applying different offset values pre-defined (or signaled) to the “DM-RS power / energy measurement” values related to HARD_RSC and SOFT_RSC of the other V2X TX UEs determined from SA decoding, the V2X TX UE can determine whether HARD_RSC and SOFT_RSC are selectable candidate resources or resources to be excluded (Step 2 of Table 2).Here, the HARD_RSC related offset value (e.g., which is assumed to be a "negative integer") can be set (or signaled) to be greater (or less) than the SOFT_RSC (e.g., which can be interpreted to protect the HARD_RSC with a relatively high priority compared to the SOFT_RSC). Here, only the offset value related to the SOFT_RSC (or the HARD_RSC) related "DM-RS power / energy measurement" value can be set (or signaled). Here, in one example, (A) the V2X message priority of other V2X TX UEs discovered from the SA decoding (and / or the V2X message priority that the V2X TX UE itself tries to transmit) and / or (B) the (corresponding) offset value set (or signaled) differently for each (measured) "congestion level" and / or (C) the V2X message priority of other V2X TX UEs figured out from the SA decoding (and / or the V2X message priority that the V2X TX UE itself tries to transmit) and / or (D) the (corresponding) threshold value can be adjusted according to the "congestion level". When the V2X TX UE selects (or reserves) the SA TX related resource with respect to the SA transmission resource associated with the data transmission on the HARD_RSC and the SOFT_RSC of other V2X TX UEs determined from the SA decoding, by (in the same manner) applying the different "DM-RS power / energy measurement" threshold values predefined (or signaled), the V2X TX UE can be caused to determine whether the HARD_RSC and the SOFT_RSC are the (SA) candidate resource to be selected or the (SA) resource to be excluded. Here, (A) the "time gap" (range) between the SA transmission time and the associated data transmission time can be set (or signaled) differently according to whether the corresponding data is transmitted with which resource type (e.g., the HARD_RSC and the SOFT_RSC) and / or (B) the data related (transmission) power value (or (transmission) power control parameter) (and / or the (maximum allowed) MSC value) transmitted with different resource types can be set (or signaled) differently (or independently). In one example, the V2X message transmission period (e.g., "1000ms") of a pedestrian UE (P-UE) (considering the relatively low measurement speed and / or the need for power saving) can be set (or signaled) to be relatively long compared to that of a vehicle mounted UE (V-UE) (e.g., "100ms"). Here, when the P-UE transmits the V2X message, the "I" value on the SA field can be caused to indicate a specific value (or a "reservation state") predefined (or signaled), thus, can be caused to be interpreted by other V2X RX UEs as (A) the (corresponding) SA (and / or the associated data) transmission has been performed by the P-UE and / or (B) as the SA based (scheduled) resource has been reserved with the predefined (or signaled) (different) period (which is relatively long compared to the case of the V-UE).

[0472] [Proposal Rule #14] In one example, (A) if multiple (sidelink (SL)) SPS procedures (or configurations) (related to different services and / or V2X message priorities) are operating (or being enabled) simultaneously, the V2X TX UE can be defined to exclude resources (in this case resources can be interpreted as subframes) related to other previously (or already) selected (SL) SPS procedures (or configurations) from (selectable) candidate resources when a particular (SL) SPS procedure (or configuration) related transmission resource is selected (step 2 of Table 2), and / or (B) predefined (or signaled) synchronization signal (primary sidelink synchronization signal (PSSS) / secondary sidelink synchronization signal (SSSS)) (and / or physical sidelink broadcast channel (PSBCH)) transmission (time (or frequency)) resources (e.g., “subframes”) can be defined to be excluded from (selectable) candidate resources (step 2 of Table 2).

[0473] [Proposal Rule #15] In one example, if V2X (TB) transmission operation (e.g., “WAN UL TX” (and / or synchronization signal transmission (resource)”) and V2X (message) TX partially or fully overlap with each other in time (or frequency) region according to pre-defined (or signaled) “priority” at a certain point in time, resource reselection related counter (Table 2) value can be defined to be simply decreased (and / or be defined to trigger resource reselection operation). In one example, if “synchronization source” of V2X TX UE changes, V2X TX UE can be defined to make resource reselection operation be triggered (and / or resource reselection operation can be defined to be triggered only when difference between changed “synchronization source” related time (or frequency) synchronization value and existing “synchronization source” related (time (or frequency) synchronization) value is larger than pre-defined (or signaled) (maximum allowed) threshold value). In one example, if “synchronization source” of V2X TX UE changes, V2X TX UE can be defined to randomly select (or reserve) transmission resource (e.g., randomly selected resource is defined to be used for transmission of pre-defined (or signaled) number of “transmission blocks (TB)”, after which “TB” transmission is performed by selecting (or reserving) resource based on sensing), and / or (B) transmission resource can be defined to be selected (or reserved) after performing sensing operation during pre-defined (or signaled) (time) period. Here, in one example, V2X TX UE can be made to perform sensing operation with respect to (based on pre-defined (or signaled) value) multiple (other) “synchronization source” related communications (including current “synchronization source”), and if one of multiple “synchronization sources” changes, corresponding (changed “synchronization source” related) sensing result can be used to select (or reserve) transmission resource.

[0474] [Proposal Rule #16] In one example, a V2X UE can be defined as a capability to report (A) simultaneous receptions (or transmissions) of some carriers which are (in time (or frequency)) synchronized (or (in time (or frequency)) synchronization difference is less than a pre-defined (or signaled) threshold) to each other, and / or to report (in time (or frequency)) simultaneous receptions (or transmissions) of some carriers which have different synchronization (or (in time (or frequency)) synchronization difference is greater than a pre-defined (or signaled) threshold) to each other, independently. In one example, a (serving) eNB which receives the (capability) information can consider the capability of the (corresponding) V2X UE and configure (or signal) an appropriate number of carriers for V2X communication (reception (or transmission)). In one example, in case of Mode-1 V2X communication, the (serving) eNB can signal information related to the V2X UE so that V2X TX operation can be performed with different MCS (range) values and / or different number of resource blocks (RBs) and / or different number of (HARQ) retransmissions according to the absolute speed of the V2X UE and / or "synchronization source type (e.g., GNSS and ENB)". Here, in one example, the (serving) eNB can configure (or signal) "location-based pool size" information differently according to the speed (or range) of the V2X UE (within the coverage of the (serving) eNB) and cause the V2X UE to perform V2X communication by applying (or using) the "location-based pool size" information corresponding to the speed of the V2X UE.

[0475] [Proposal Rule #17] In one example, (considering (A) HARQ combining operation with respect to receptions of different redundancy versions (RVs) (data) and / or (B) PSCCH payload size (increase) required for (time) resource location information signaling related to data (re)transmission), a V2X TX UE can cause to select multiple (NUM_RETX) data (re)transmission related time resources within a pre-defined (or signaled) window (LIM_TIMEWIN) related to a specific (one) TB. Here, if the corresponding rule is applied, the V2X TX UE can be caused to perform sensing based resource (re)selection operation according to (part of) the following method (e.g., Step 2 or 3 of Table 2). Here, the LIM_TIMEWIN value can be adjusted (or configured (or signaled) differently) according to (A) V2X message priority which the V2X TX UE tries to transmit and / or (B) (measured) congestion level and / or (C) V2X message (or service) related target delay (or reliability) requirement.

[0476] (Example #17-1) In one example, among the (non-excluded) resources (NOEX_RSC) derived from performing (Table 2) Step 2 (e.g., Option 2-1), if (TB-specific) NUM_RETX data (re)transmission related time resources are (all) not selectable within LIM_TIMEWIN (or the number of candidates that are selectable within LIM_TIMEWIN is less than a pre-defined (or signaled) threshold), then (A) (TB-specific) NUM_RETX data (re)transmission is defined to be (all) skipped, and / or (B) (TB-specific) data (re)transmission is defined to be (partially) performed using only the (maximum number of) time resources that are selectable within LIM_TIMEWIN, and / or (C) (TB-specific) NUM_RETX data (re)transmission related time resources are defined to be selected within another pre-defined (or signaled) window (FLIM_TIMEWIN) (e.g., “FLIM_TIMEWIN > LIM_TIMEWIN”) (e.g., resource selection can be skipped if there are no candidates selectable within FLIM_TIMEWIN), and / or (D) the PSSCH DM-RS RSRP threshold (related to resource exclusion) of (Table 2) Step 2 can be defined to be increased by a pre-defined (or signaled) offset value until (TB-specific) NUM_RETX data (re)transmission related time resources are (all) selected within LIM_TIMEWIN (or FLIM_TIMEWIN) (or until the number of candidates that are selectable within LIM_TIMEWIN becomes greater than the pre-defined (or signaled) threshold). In one example, (after performing (Table 2) Step 2 (according to the rule),) when (TB-specific) NUM_RETX data (re)transmission related time resources are selected according to a pre-defined rule (e.g., randomly), among these resources for which PSSCH DM-RS RSRP values have been measured for the lower (or upper) X% on (Table 2) Step 3, if the (partially) selected time resources are not within LIM_TIMEWIN (or FLIM_TIMEWIN), then it can be defined such that (A) re-selection is performed (until the corresponding condition is met), and / or (B) (TB-specific) NUM_RETX data (re)transmission is (all) skipped, and / or (C) (TB-specific) data (re)transmission is (partially) performed using only time resources that are within LIM_TIMEWIN (or FLIM_TIMEWIN).

[0477] [Proposal Rule #18] In one example, PSCCH DM-RS related cyclic shift (CS) (and / or OCC) values are fixed to a pre-defined (or signaled) (specific) value (e.g., "CS index = 0", "OCC = [+1 +1]"). Here, if the corresponding rule is applied and PSCCH transmission resources (partially) overlap among different V2X TX UEs, PSCCH related reception performance can not be guaranteed. Here, to mitigate the corresponding issue, V2X TX UEs can be made to select a CS (and / or OCC) value according to a pre-defined rule (e.g., random selection) within a pre-defined (or signaled) CS set (and / or OCC set). Here, the CS (index) set can be set (or signaled) as "CS index 0, 3, 6, 9". Here, a V2X RX UE (since it does not know exactly which value is selected by a V2X TX UE) performs a blind detection (BD) operation with respect to (all) CSs (and / or OCCs) within the corresponding CS set (and / or OCC set). In one example, a CS (and / or OCC) value selected by a V2X TX UE within a CS set (and / or OCC set) can be defined to be randomized (or frequency-hopped) by a function (or equation) with input parameters (or seed values) such as (A) a (V2V) subframe (or slot) index and / or (B) a V2X TX UE ID (or a (target) V2X RX UE ID) and / or (C) an (X-bit) ID transmitted on a PSCCH (and / or a CS set (and / or OCC set) of a V2X TX UE (configuration) can be defined to be randomized (or changed) by a function (or equation) with input parameters (or seed values) such as (D) a (V2V) subframe (or slot) index and / or (E) a V2X TX UE ID (or a (target) C2X RX UE ID) and / or (F) an (X-bit) ID transmitted on a PSCCH). Here, a CS set (and / or OCC set) (configuration) can be differently set (or signaled) according to a V2X message priority (that a V2X TX UE attempts to transmit) and / or a congestion level (measured). In one example, (if the above rule is applied, to reduce a complexity related to a (PSCCH DM-RS) CS (and / or OCC) BD operation of a V2X RX UE, a maximum number of BDs that a V2X RX UE has to perform within one subframe can be set (or signaled) (from a (serving) eNB). In one example, a V2X UE can be made to report (to a (serving) eNB) a maximum number of BDs that a V2X UE can perform within one subframe through a pre-defined signaling.In one example, the PSCCH scrambling sequence generator can be initialized according to (pre-defined (or signaled) (all) CS (and / or OCC) values (and / or a pre-defined (or signaled) C_INIT value (e.g., “510”)) within a CS set (and / or OCC set) selected by the V2X TX UE. (If the corresponding rule is applied,) a CS field (e.g., “3 bits”) can be defined on the PSCCH, and the corresponding CS field value can be specified by the V2X TX UE according to a pre-defined rule (e.g., randomly selected) (one) CS value (SELCS_VAL) selected within the pre-defined (or signaled) CS set (and / or a value derived (or calculated) using a pre-defined (randomized (or frequency-hopping)) function with the input parameter SELCS_VAL value) (in the same way), and according to the corresponding (specified) CS field value, the PSSCH DM-RS CS value (associated with the PSCCH) can be set (or determined). Here, if the corresponding rule is applied, and the interference to the PSCCH DM-RS (CS) has been mitigated (or randomized), the interference to the (associated) PSSCH DM-RS (CS) can be (in the same way) mitigated (or randomized). In one example, (if the above rule is applied,) the PSSCH DM-RS value (associated with the PSCCH) (instead of defining a CS field (e.g., “3 bits”) additionally on the PSCCH) can be set by the V2X TX UE according to a pre-defined rule (e.g., randomly selected) (one) PSSCH DM-RS CS value (SELCS_VAL) selected within the pre-defined (or signaled) CS set (and / or a value derived (or calculated) using a pre-defined (randomized (or frequency-hopping)) function with the input parameter SELCS_VAL value) (in the same way). Here, the PSCCH scrambling sequence generator can be initialized according to the CS field value (on the PSCCH) (and / or the V2X TX UE ID (or (target) V2X RX UE ID (or X-bit ID)) (on the PSCCH)) and / or (V2V) subframe (or slot) index.

[0478] In one example, when performing V2V communication, the PSCCH and / or (associated) PSSCH related (A) (DM-RS) sequence generation rule and / or (B) (DM-RS) CS (or OCC) index selection (or determination) rule and / or (C) group or sequence frequency-hopping rule can be defined as in Table 7 and Table 8. In one example, the following proposed methods (partially) describe a method of effectively performing (DM-RS) sequence (or CS (or OCC) index) (and / or interference) randomization operation when PSCCH and / or PSSCH transmission resources between different UEs (partially or completely) overlap each other.

[0479] In the following, with reference to Table 7 and Table 8, examples of PSCCH and / or (associated) PSSCH related (A) (DM-RS) sequence generation rule and / or (B) (DM-RS) CS( / OCC) index selection( / determination) rule and / or (C) group / sequence hopping rule are described when performing V2V communication. At this time, the V2C WI only supports normal CP and can not deliver destination ID through SA. In addition, 16 CRC bits from SA can be used to generate PSSCH DMRS sequence and data scrambling sequence.

[0480]

[0481]

[0482]

[0483] Here,

[0484]

[0485]

[0486] Here, and n X represents X bits in SA used for generating PSSCH DMRS sequence.

[0487] [Proposal Rule #19] In one example, 2 bits among predefined(or signaled)(or randomly selected) 16 bits can be scrambled with the selected PSCCH CS index(or value)(e.g., “2 bits”) among 3 bits “C 15 ,C 12 ,C 13 ,C 14 ” among 16 bits CRC(C0,C1,…,C 15 ” of PSCCH when determining (associated) PSSCH DM-RS CS index(or value). In one example, when applying the above rule, (A) the (final) 16 bits CRC of PSCCH can be kept as(or applied to) “C0,C1,…,C 15) LSB (e.g., PSSCH DM-RS OCC index (or value) can also change when applying the corresponding rule) (or MSB) bits (and / or 2 bits at a specific location that are predefined (or signaled) (or randomly selected)) can be scrambled with the selected PSCCH CS index (or value) (e.g., “2 bits”). In one example, when applying the above rule, (A) the 16-bit CRC that is (partially) changed due to the (corresponding) scrambling operation can become the (final) CRC of the PSCCH, and / or (B) the (final) 16-bit CRC of the PSCCH is kept to (or applied to) the “C0, C1, …, C 15 ” value (e.g., considering (or assuming) that only the CRC (and / or bits (field)) that is used to determine the (associated) PSSCH DM-RS CS index (or value) is changed by the (corresponding) scrambling operation). In one example, the (different) 16 bits that are expected to be used for scrambling are predefined (or signaled) for each PSCCH CS index (or value) (e.g., “2 bits”), and the UE is made to scramble (A) the selected PSCCH CS index (or value) and the associated 16 bits (S0, S1, …, S 15 ) that are intended to be used for scrambling and the (generated) 16-bit CRC (C0, C1, …, C 15 ) of the PSCCH, such that the (corresponding) scrambling result (W0, W1, …, W 15 ) becomes the final 16-bit CRC of the PSCCH, and / or (B) the (final) 16-bit CRC of the PSCCH is kept to (or applied to) the “C0, C1, …, C 15 ” value, but only the 16-bit CRC (and / or bits (field)) that is used to determine the (associated) PSSCH DM-RS CS index (or value) can be used as (or assumed to be) the “W0, W1, …, W 15 ” value (and / or the 3 bits “W 15 ,W 12 ,W 13 ” from “W0, W1, …, W 14 ”).

[0488] In one example, (A) SCI format configuration fields for mode 2 V2V scheduling (MODE2_SCH) operation and / or (B) DCI format configuration fields for mode 1 dynamic V2V scheduling (MODE1_DYN) operation can be defined as follows. In one example, in the FRA_INRETX field (similar to the LVRB form of the existing LTE system), a resource indication value (RIV) value can be defined to inform (PSSCH transmission related) (A) starting subchannel index (or location) information (SUB_START) and / or length (or number) information of subchannels (in the frequency domain) allocated (or located) continuously (SUB_LENGTH). In one example, when two PSSCH transmissions are set (or signaled) for a specific (one) TB transmission, (A) the SUB_START value can be interpreted as starting index (or location) information of a subchannel for performing a second PSSCH transmission (SECDATA_SUBST), and / or (B) the SUB_LENGTH value can be interpreted as subchannel length (or number) information for a first PSSCH transmission and a second PSSCH transmission (SFDATA_SUBLN). Here, (instead of signaling directly through the FRA_INRETX field) the starting index (or location) information of a subchannel for performing a first PSSCH transmission (FIRDATA_SUBST) can be made to be figured out by RX UE implicitly through a (one-to-one) mapping (or linkage) relationship between a “((blind) detected) (first) PSCCH resource index (or location) information” and “starting index (or location) information of a subchannel for performing (associated) (first) PSSCH transmission” which is pre-defined (or signaled).

[0489] In the following, examples of (A) SCI format configuration fields for MODE2_SCH operation and / or (B) DCI format configuration fields for MODE1_DYN operation will be described.

[0490] The SCI can include 1) priority: 3 bits, 2) resource reservation: 4 bits, 3) MCS: 5 bits, 4) CRC: 16 bits, 4) retransmission index (RETX_INDEX): 1 bit, 6) time gap between transmission start and retransmission (TGAP_INIRETX): 4 bits, 7) frequency resource location of transmission start and retransmission (FRA_INRETX): 8 bits, 8) reserved bits (RSV_BIT): 7 bits.

[0491] The DCI can include 1) CIF: 3 bits, 2) minimum index of subchannels allocated for transmission start (PSCCH_RA): 5 bits, 3) time gap between transmission start and retransmission (as SA content): 4 bits, 4) frequency resource location of transmission start and retransmission (FRA_INRETX): 8 bits.

[0492] [Proposal #20] In one example, if one PSSCH transmission is set (or signaled) for a specific (one) TB transmission, part of the information of the (above-mentioned) FRA_INRETX field becomes unnecessary (e.g., "SECDATA_SUBST related information"). (In other words) In one example, the only information needed for the corresponding case is the subchannel length (or number) information (FDATA_SUBLN) for the first PSSCH transmission. Here, the (corresponding) unnecessary information related status (or value) and / or bit can be defined according to (part or all of) the following rules.

[0493] (Example #20-1) In one example, (A) when it is assumed that a maximum of 20 subchannels can be set (or signaled) as a (V2V) resource pool (on one subframe), the number of bits needed to express the FDATA_SUBLN information is "5" bits (i.e., "CEILING(LOG2(20)) = 5" (Here, as one example, CEILING(X) is a function that returns the minimum information value that is greater than or equal to X)), and / or (B) when it is assumed that K subchannels are set (or signaled) as a (V2V) resource pool (on one subframe), the number of bits needed to express the FDATA_SUBLN information becomes "CEILING(LOG2(K))". Here, in one example, when two PSSCH transmissions are set (or signaled) for a specific (one) TB transmission, and the (needed) FRA_INRETX field size is assumed to be "Q" bits (e.g., "Q = 8"), the remaining bits of "(Q - 5)" (and / or "(Q - CEILING(LOG2(K))") can be interpreted as (or considered as) unnecessary information related bits.

[0494] (Example #20-2) In one example, if two PSSCH transmissions are set (or signaled) for a specific (one) TB transmission, and the (needed) FRA_INRETX field size is assumed to be "Q" bits, a number of (pre-defined (or signaled)) (part or all of) SECDATA_SUBST values that can be specified together with a specific (one) FDATA_SUBLN (or SFDATA_SUBLN) value actually needed can be interpreted as (or considered as) unnecessary information related status (or value).

[0495] (Example #20-3) If one PSSCH transmission is set (or signaled) for a specific TB transmission, the RETX_INDEX related status (or value) can be interpreted as (or considered as) unnecessary information since the V2X RX UE is able to determine (corresponding) V2X TX UE performs one or two PSSCH transmissions (with respect to the specific TB) through the TGAP_INI RETX field. In another example, if one PSSCH transmission is set (or signaled) for a specific TB transmission, the RETX_INDEX related value (or status) can be specified by a (specific) value (or status) which is predefined (or signaled). Here, in one example, the (RETX_INDEX related) corresponding (specific) value (or status) can be used for “virtual CRC” application.

[0496] (Example #20-4) In one example, part of the RSV_BIT field related bits (e.g., “7 bits”) among which bits are predefined (or signaled) can be interpreted as (or considered as) unnecessary information related bits (or values).

[0497] In one example, the PSSCH (DM-RS) sequence (or CS (or OCC) index) collision problem occurred when PSSCH transmission resources of different UEs partially or fully overlap with each other can be mitigated (e.g., PSCCH CRC is randomized (by the corresponding operation), and due to the randomization, (finally) PSSCH (DM-RS) sequence (or CS (or OCC) index) is randomized) by randomizing the (above) unnecessary information related state (or value) and / or bit(s) according to (part of) the following rules. In one example, the case where the above unnecessary information related state (or value) and / or bit(s) occurs (e.g., the case where PSSCH transmission is set (or signaled) once for a specific (one) TB transmission) is only an example, and the (part of or whole of) proposed method of the present invention can be extended to apply to various cases (where the unnecessary information related state (or value) and / or bit(s) occurs) (e.g., (in the case of MODE1_DYN_DCI_FORMAT and / or MODE2_SCH_SCI_FORMAT,) (additional) extra bit(s) (e.g., "(8-CEILING(LOG2(K·(K+1) / 2))(FRA_INRETX size)") (and / or "(8-CEILING(LOG2(K·(K+1) / 2))(FRA_INRETX size)-CEILING(LOG2(K))(PSCCH_RA size)")") (and / or the (additional) extra bit(s) generated as the FRA_INRETX size changes can be considered as unnecessary information related bit(s) with respect to the pre-defined (or signaled) (target) payload size (e.g., the (target) payload size of MODE1_DYN_FORMAT and MODE2_SCH_SCI_FORMAT can be changed to (existing) DCI format 0 payload size (refer to the above description) and 48 bits (refer to the above description), respectively)) can be considered as unnecessary information related bit(s) as the FRA_INRETX size changes). In one example, by the corresponding randomization operation of the unnecessary information related state (or value) and / or bit(s), the 16-bit CRC (C0, C1, …, C 15) is randomized (or changed), the final PSSCH DM-RS CS (or sequence or OCC) (index) is also randomized (or changed) (refer to Table 7 and / or Table 8). Here, in one example, the (partial) following rule is applied to the (additional) extra bits generated as (A) (the above) (example #20-3) and / or (B) (example #20-4) and / or (C) the FRA_INRETX size is changed according to the total number (K) of sub-channels including the (pre-defined (or signaled)) V2V resource pool (within one subframe) (example #20-5). Here, in one example, the (partial) following rule is applied to the (additional) extra bits generated as (A) (the above) (example #20-3) and / or (B) (example #20-4) and / or (C) the FRA_INRETX size is changed according to the total number (K) of sub-channels including the (pre-defined (or signaled)) V2V resource pool (within one subframe) (example #20-5). Here, in one example, the (partial) following rule is applied to the (additional) extra bits generated as (A) (the above) (example #20-3) and / or (B) (example #20-4) and / or (C) the FRA_INRETX size is changed according to the total number (K) of sub-channels including the (pre-defined (or signaled)) V2V resource pool (within one subframe) (example #20-5). Here, in one example, the (partial) following rule is applied to the (additional) extra bits generated as (A) (the above) (example #20-3) and / or (B) (example #20-4) and / or (C) the FRA_INRETX size is changed according to the total number (K) of sub-channels including the (pre-defined (or signaled)) V2V resource pool (within one subframe) (example #20-5).

[0498] (Rule #20-1) In one example, the TX UE can set the (above-mentioned) unnecessary information related status (or value) and / or bit(s) to a randomly selected value (and / or a value pre-defined (or signaled) by the (serving) eNB (or network). Here, the condition to apply this rule to each of the (above-mentioned) unnecessary information related status (or value) and / or bit(s) (e.g., (Example #20-1), (Example #20-2), (Example #20-3), (Example #20-4)) can be defined (or signaled) differently. Here, since the (actually used) FRA_INRETX size becomes “0” when the number of sub-channels of the resource pool (for V2X communication) is set (or signaled) as “1” (and / or when one PSSCH transmission is set (or signaled) for a particular (one) TB transmission), this rule is applied to the unnecessary information related status (or value) and / or bit(s) of (Example #20-3) (e.g., the RETX_INDEX related status (or value)), otherwise (e.g., the case where the number of sub-channels of the resource pool (for V2X communication) is set (or signaled) not as “1” (and / or more than “1”)), the rule can be applied to the unnecessary information related status (or value) and / or bit(s) of (Example #20-2) (e.g., the number of (pre-defined (or signaled)) (part of or all) SECDATA_SUBST values (or status) that can be specified together with a particular (one) FDATA_SUBLN value (that is actually needed)). Here, in one example, (in the case where one PSSCH transmission is performed for a particular (one) TB transmission), regardless of the number of sub-channels of the resource pool (for V2X communication) set (or signaled) as, the rule is applied to the unnecessary information related status (or value) and / or bit(s) of (Example #20-3) (e.g., the RETX_INDEX related status (or value)), and only for the case where the number of sub-channels of the resource pool (for V2X communication) is set (or signaled) not as “1” (and / or more than “1”), the rule can be applied to the unnecessary information related status (or value) and / or bit(s) of (Example #20-2) (e.g., the number of (pre-defined (or signaled)) (part of or all) SECDATA_SUBST values (or status) that can be specified together with a particular (one) FDATA_SUBLN value (that is actually needed)).

[0499] (Rule #20-2) In one example, the (above-mentioned) unnecessary information related status (or value) and / or bit can be set as (A) the TX (or (target) RX) UE ID, and / or (B) a value derived (or calculated) by a pre-defined (random (or frequency-hopping)) function with the selected PSCCH CS index (or value) (e.g., “2 bits”) as an input parameter, or (C) the TX (or (target) RX) UE ID, and / or (D) a value derived from the selected PSCCH CS index (or value) (e.g., “2 bits”). In one example, if the (above-mentioned) unnecessary information related bit is defined in the form of (Example #20-1), and “(Q-5)” (and / or “(Q-CEILING(LOG2(K)))”) (e.g., “Q=8” and “K=20”) is greater than the bit value (PC_SELSCBIT) (e.g., “2 bits”) representing the selected PSCCH CS index (or value), then (A) among the “(Q-5)” (and / or “(Q-CEILING(LOG2(K)))”) bits, the (bit) position that must be designated for the PC_SELCSBIT bit (or value) (or the bit (or value) derived as the PC_SELCSBIT bit) is set (or signaled), and / or (B) the remaining bits (e.g., “1” bit) of “(Q-5-PC_SELCSBIT)” (and / or “(Q-CEILING(LOG2(K))-PC_SELCSBIT)”) can be padded with zeros (or set to a pre-defined (or signaled) specific value).

[0500] In one example, if one PSSCH transmission is set (or signaled) for a specific (one) TB transmission, the (above-mentioned) FRA_INRETX field size can be (exceptionally) reduced (e.g., “(Q-5)”, “(Q-CEILING(LOG2(K)))”).

[0501] In one example, (if the PSSCH (associated with the PSCCH) is transmitted in the form of “FDM”), the PSCCH CRC used to determine parameters such as the (DM-RS) sequence (or CS (or OCC) index) related to the PSSCH transmitted at a specific point in time can be defined as the PSCCH CRC transmitted at the same point in time as the PSSCH (and / or the PSCCH CRC (always) transmitted together for PSSCH transmission).

[0502] Since the examples of the proposed method described above can also be included as implementation methods of the present application, it is obvious that the examples can also be considered as a proposed method. In addition, although the proposed method described above can be implemented independently, it can be implemented in the form of combining (or merging) part of the proposed method. In one example, although the proposed method is described based on the 3GPP LTE system for convenience of description, the scope of the system to which the proposed method is applied can be extended to include other systems in addition to the 3GPP LTE system. As one example, the proposed method of the present application can be extended to be applied to D2D communication. Here, in one example, the D2D communication refers to communication performed by a UE directly to other UEs using a radio channel, where the UE means a terminal of a user in this example; however, when a network device such as an eNB transmits or receives a signal to or from a UE according to a communication method, the eNB can also be considered as a kind of UE. In addition, as one example, the proposed method of the present application can be limitedly applied only to mode 2 V2X operation (and / or mode 1 V2X operation). In addition, in one example, the proposed method of the present application can be limitedly applied only to a case where a "(transmission) resource (re)selection operation" is triggered (if a (predefined (or signaled) condition is satisfied), and there is (generated) packet (or message) (or when the packet (or message) is generated) (and / or when there is no (generated) packet (or message) on a "(lower layer) buffer" (and / or "PDCP layer")) (or when no packet (or message) is generated). In addition, in one example, the proposed method of the present application can be limitedly applied only to a case where a PSSCH (associated with a PSCCH) is not positioned (or positioned) on a neighboring RS on the same subframe. In addition, in one example, the proposed method of the present application can be extended to be applied not only to V2V mode 1 (or mode 2) dynamic scheduling operation but also to V2C mode 1 (or mode 2) semi-persistent scheduling (SPS) operation (and / or V2X mode 1 (or mode 2) dynamic scheduling operation and / or V2X mode 1 (or mode 2) SPS operation). In addition, in one example, the "transmission resource selection" in the present application can be (extended to be) interpreted as "transmission resource (re)reservation".

[0503] Figure 39 is a block diagram of a UE implementing an embodiment of the present application.

[0504] Referring to Figure 39 , the UE 1100 includes a processor 1110, a memory 1120 and a radio frequency (RF) unit 1130.

[0505] According to one embodiment, the processor 1110 can implement functions, operations, or methods of the present application. For example, the processor 1110, which performs sensing during a UE-specific sensing period, can select resources for performing V2X communication and perform V2X communication based on the selected resources.

[0506] For example, the processor 1110 can select resources for performing V2X communication within a range satisfying a delay requirement and perform V2X communication based on the selected resources.

[0507] For example, the processor 1110 can perform sensing in units of subchannels corresponding to the size of a subchannel used for V2X message transmission, select resources for performing V2X message transmission, and perform V2X message transmission based on the selected resources.

[0508] For example, the processor 1110 can perform reservation of a limited number of resources for performing V2X communication and perform V2X communication on the limited number of resources.

[0509] For example, the processor 1110 determines whether a resource reselection condition is satisfied, and if the resource reselection condition is satisfied, performs reselection of resources for performing V2X (Vehicle-to-X) communication and performs V2X communication based on the selected resources.

[0510] For example, the processor 1110 can select subframes excluding subframes related to subframes in which transmission is performed during a sensing period from a sensing window and perform V2X communication based on the selected subframes.

[0511] For example, the processor 1110 can allocate a V2X resource pool with respect to remaining subframes except for a specific subframe and perform V2X communication on the allocated V2X resource pool.

[0512] The RF unit 1130 connected to the processor 1110 transmits and receives a radio signal.

[0513] The processor can include an application-specific integrated circuit (ASIC), other chipsets, a logic circuit, and / or a data processing device. The memory can include a read-only memory (ROM), a random access memory (RAM), a flash memory, a memory card, a storage medium, and / or other storage devices. The RF unit can include a baseband circuit for processing a radio signal. When the embodiment is implemented by software, the above-described methods can be implemented by a module (process, function, etc.) that performs the above-described functions. The module can be stored in the memory and executed by the processor. The memory can be installed inside or outside the processor and can be connected to the processor via various well-known means.

Claims

1. A method in a wireless communication system, the method performed by a user equipment, UE, and comprising: determining a set of sidelink resources based on a set of candidate resources and a candidate resource, wherein the candidate resource is excluded from the set of candidate resources, wherein a time unit index of the candidate resource is determined based on a time unit index of a specific time unit for which the UE does not monitor for transmissions of the UE; and performing a physical sidelink shared channel, PSSCH, transmission based on the set of sidelink resources, wherein the time unit index of the candidate resource is Y, wherein the time unit index of the specific time unit is M, wherein the candidate resource is determined based on Y and M satisfying: Y + j*P = M + q*I, wherein * denotes multiplication, wherein j is at least one integer value from 0 to Cresel-1, wherein Cresel is a number of time units in a set of time and frequency resources for a transmission opportunity of PSSCH, wherein q is a positive integer, wherein P is related to a resource reservation interval of the UE, and wherein I is related to values allowed for a resource reservation period.

2. The method of claim 1, wherein, the candidate resource is in a time unit within a selection window of the UE selecting at least one sidelink resource.

3. The method of claim 2, wherein, the selection window has a duration of 100 ms.

4. The method of claim 1, wherein, the Cresel is proportional to a value of a resource reselection counter randomly determined by the UE.

5. The method of claim 4, wherein, the value of the resource reselection counter is greater than or equal to 5 and less than or equal to 15.

6. The method of claim 1, further comprising the step of: sensing is performed within a sensing window other than the specific time unit in which the transmission of the UE occurs.

7. The method of claim 6, wherein, the sensing window is specific to the UE. 8.A user equipment, UE, configured to operate in a wireless communication system, the UE comprising: a transceiver; at least one processor; and at least one computer memory operably connectable to the at least one processor and storing instructions that, based on execution by the at least one processor, perform operations including: determining a set of sidelink resources based on a set of candidate resources and a candidate resource, wherein the candidate resource is excluded from the set of candidate resources, wherein a time unit index of the candidate resource is determined based on a time unit index of a specific time unit for which the UE does not monitor for transmissions of the UE; and performing a physical sidelink shared channel, PSSCH, transmission based on the set of sidelink resources, wherein the time unit index of the candidate resource is Y, wherein the time unit index of the specific time unit is M, wherein the candidate resource is determined based on Y and M satisfying: Y + j*P = M + q*I, wherein * denotes multiplication, wherein j is at least one integer value from 0 to Cresel-1, wherein Cresel is a number of time units in a set of time and frequency resources for a transmission opportunity of PSSCH, wherein q is a positive integer, wherein P is related to a resource reservation interval of the UE, and wherein I is related to values allowed for a resource reservation period. wherein I relates to a value allowed for a resource reservation period.

9. An apparatus configured to control operation of a user equipment (UE) in a wireless communication system, the apparatus comprising: at least one processor; and at least one computer memory operably connectable to the at least one processor and storing instructions that, based on execution by the at least one processor, perform operations comprising: determining a set of sidelink resources based on a set of candidate resources and a candidate resource, wherein the candidate resource is excluded from the set of candidate resources, wherein a time unit index of the candidate resource is determined based on a time unit index of a particular time unit for which the UE does not monitor for transmissions by the UE; and performing a physical sidelink shared channel (PSSCH) transmission based on the set of sidelink resources, wherein the time unit index of the candidate resource is Y, wherein the time unit index of the particular time unit is M, wherein the candidate resource is determined based on Y and M satisfying: Y + j*P = M + q*I, wherein * denotes multiplication, wherein j is at least one integer value from 0 to Cresel-1, wherein Cresel is a number of time units in a set of time and frequency resources for a transmission opportunity of a PSSCH, wherein q is a positive integer, wherein P relates to a resource reservation interval of the UE, and wherein I relates to a value allowed for a resource reservation period.

10. A method of controlling operation of a user equipment (UE) in a wireless communication system, the method comprising: determining a set of sidelink resources based on a set of candidate resources and a candidate resource, wherein the candidate resource is excluded from the set of candidate resources, wherein a time unit index of the candidate resource is determined based on a time unit index of a particular time unit for which the UE does not monitor for transmissions by the UE; and performing a physical sidelink shared channel (PSSCH) transmission based on the set of sidelink resources, wherein the time unit index of the candidate resource is Y, wherein the time unit index of the particular time unit is M, wherein the candidate resource is determined based on Y and M satisfying: Y + j*P = M + q*I, wherein * denotes multiplication, wherein j is at least one integer value from 0 to Cresel-1, wherein Cresel is a number of time units in a set of time and frequency resources for a transmission opportunity of a PSSCH, wherein q is a positive integer, wherein P relates to a resource reservation interval of the UE, and wherein I relates to a value allowed for a resource reservation period.

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