Method and apparatus for initiating an RRC (RADIO RESOURCE CONTROL) connection for V2X (VEHICLE-TO-EVERYTHING) communication

Abstract

A communication method and system are provided for converging a 5G communication system that supports a higher data transmission rate than a 4G (4th-Generation) system using IoT (Internet of Things) technology. The communication method and system include intelligent services based on IoT-related technologies and 5G communication technologies, such as smart homes, smart buildings, smart cities, smart cars, connected cars, healthcare, digital education, smart retail, security, and safety services. A method of user equipment (UE) for performing V2X (vehicle-to-everything) sidelink communication is provided.

Description

Technology Field

[0001] The present disclosure relates to a method for initiating a wireless resource control (RRC) connection for vehicle-to-everything (V2X) communication and a method for handling resources for retransmitting a Hybrid Automatic Repeat Request (HARQ) in V2X sidelink communication. Background Technology

[0002] Efforts are being made to develop improved 5G communication systems or pre-5G communication systems to meet the increasing demand for wireless data traffic following the commercialization of 4th generation (4G) communication systems. For this reason, 5G communication systems or pre-5G communication systems are referred to as 'Beyond 4G networks' or 'Post-LTE (long term evolution) systems'. To achieve high data speeds, the implementation of 5G wireless communication systems is being considered not only in low-frequency bands but also in high-frequency (mmWave) bands (e.g., 10 GHz to 100 GHz bands). To reduce radio wave propagation loss and increase transmission distance, technologies such as beamforming, massive array multiple input multiple output (massive MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large-scale antennas are being discussed in the design of 5G communication systems. In addition, to improve the system network, technologies such as advanced small cell, cloud radio access network (cloud RAN), ultra-dense network, device-to-device (D2D) communication, wireless backhaul, mobile network, cooperative communication, Coordinated Multi-Points (CoMP), and receiver interference cancellation are being developed in 5G communication systems.In 5G systems, advanced coding modulation (ACM) technologies such as FQAM (frequency and quadrature amplitude modulation), which is a combination of hybrid FSK (frequency shift keying) and QAM (quadrature amplitude modulation), and SWSC (sliding window superposition coding) are being developed, as well as advanced access technologies such as FBMC (filter bank multi-carrier), NOMA (non-orthogonal multiple access), and SCMA (sparse code multiple access).

[0003] From a similar perspective, the Internet, a human-centered connectivity network where humans generate and consume information, is now evolving into the Internet of Things (IoT), where distributed entities such as objects exchange and process information without human intervention. The Internet of Everything (IoE) has also emerged, combining IoT technology with big data processing technology through connections with cloud servers. As technological elements such as "sensing technology," "wired / wireless communication and network infrastructure," "service interface technology," and "security technology" are required for IoT implementation, research on sensor networks, Machine-to-Machine (M2M) communication, and Machine Type Communication (MTC) is currently underway. This IoT environment can provide intelligent Internet technology services that create new value for human life by collecting and analyzing data generated between connected objects. In this context, IoT can be applied to various fields—such as smart homes, smart buildings, smart cities, smart or connected cars, smart grids, healthcare, smart appliances, and advanced medical services—through the convergence and integration of existing Information Technology (IT) and diverse industrial applications.

[0004] Accordingly, various attempts are being made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, MTC, and M2M communication can be implemented using beamforming, MIMO, and array antennas. In addition, the application of cloud RAN as the aforementioned big data processing technology can be considered an example of convergence between 5G technology and IoT technology.

[0005] Recently, various broadband wireless technologies have been developed to meet the growing number of broadband subscribers and to provide more high-quality applications and services. Second-generation (2G) wireless communication systems were developed to provide voice services while ensuring user mobility. Third-generation (3G) wireless communication systems support data services as well as voice services. Fourth-generation (4G) wireless communication systems were developed to provide high-speed data services. However, current 4G wireless communication systems are struggling due to a lack of resources to meet the increasing demand for high-speed data services. Therefore, 5G wireless communication systems (also known as next-generation wireless or new wireless (NR)) are being developed to meet the increasing demand for various services with diverse requirements, such as high-speed data services, ultra-high reliability, and low-latency application support.

[0006] Furthermore, 5G wireless communication systems are expected to handle different use cases with significantly different requirements in terms of data speed, latency, reliability, and mobility. However, the design of the wireless interfaces of 5G wireless communication systems is expected to be flexible enough to serve user equipment (UEs) with significantly different capabilities depending on the use case and the market segment to which the UE serves end customers. Exemplary use cases expected to be addressed by 5G wireless communication systems include enhanced mobile broadband (eMBB), massive machine type communication (m-MTC), and ultra-reliable low latency communication (URLL). eMBB requirements (e.g., data speeds of tens of Gbps, low latency, high mobility, etc.) address a market segment representing wireless broadband subscribers who require internet connectivity while on the move, anytime and anywhere. m-MTC requirements (e.g., very high connection density, intermittent data transmission, very long battery life, low mobility handling, etc.) cover a market segment representing IoT / IoE that assumes the connection of billions of devices. URLL requirements (e.g., very low latency, very high reliability, and variable mobility, etc.) cover a market segment representing vehicle-to-vehicle / vehicle-to-infrastructure communication, which is predicted to be one of the enablers for industrial automation applications and autonomous vehicles.

[0007] Vehicle communication services, represented by V2X (vehicle-to-everything) services, include V2V (Vehicle-to-Vehicle), V2I (Vehicle-to-Infrastructure), V2N (Vehicle-to-Network), and V2P (Vehicle-to-Pedestrian) types. V2X services may be provided by the PC5 interface and / or the Uu interface. Support for V2X services via the PC5 interface is provided by V2X sidelink communication, a communication mode in which UEs can communicate directly with each other via the PC5 interface, and is supported when the UE is served by a next-generation wireless access network (NG-RAN) and the UE is outside the NG-RAN coverage area. Only UEs authorized to use V2X services may perform V2X sidelink communication.

[0008] UEs that support V2X sidelink communication can operate in the following two modes for resource allocation:

[0009] (1) Scheduled resource allocation (also called mode 1), where:

[0010] - The UE requires a wireless resource control connection (RRC_CONNECTED) to transmit data, and also

[0011] - The UE requests transmission resources from the next-generation node B (gNB), which schedules transmission resources for sidelink control information and data transmission.

[0012] (2) UE Autonomous Resource Selection (also known as Mode 2), where:

[0013] - The UE unilaterally selects resources from the resource pool, performs transmission format selection to transmit sidelink control information and data, and also

[0014] - The UE performs detection for the (re)selection of sidelink resources. Based on the detection results, the UE (re)selects some specific sidelink resources and reserves multiple sidelink resources.

[0015] Whenever a UE detects a cell on the corresponding carrier, it is considered to be within the coverage area on the carrier used for V2X sidelink communication. If a UE authorized for V2X sidelink communication is within the coverage area on the frequency used for V2X sidelink communication, or if the gNB provides a V2X sidelink configuration for that frequency (including cases where the UE is out of coverage on that frequency), the UE uses scheduled resource allocation according to the gNB configuration or UE autonomous resource selection. If the UE is out of coverage on the frequency used for V2X sidelink communication and the gNB does not provide a V2X sidelink configuration for that frequency, the UE may use a series of transmit and receive resource pools pre-configured for the UE. V2X sidelink communication resources are not shared with other non-V2X data transmitted over the sidelink.

[0016] If an RRC_CONNECTED UE is interested in transmitting V2X sidelink communication to request sidelink resources, it may send a sidelink UE information message to the serving cell. If the UE is configured by the upper layer to receive V2X sidelink communication and a pool of V2X sidelink receiving resources is provided, the UE receives communication from the provided resources.

[0017] For V2X sidelink communication, sidelink transmit and / or receive resources may be provided, including an exceptional pool of different frequencies for scheduled resource allocation and UE autonomous resource selection. Sidelink resources for different frequencies may be provided via dedicated signaling, System Information Block 21 (SIB21), and / or pre-configuration. A serving cell may display to the UE only the frequencies from which the UE can obtain resource configurations for V2X sidelink communication. If multiple frequencies and associated resource information are provided, selecting a frequency from among the provided frequencies depends on the UE implementation. If the UE detects a cell providing resource configurations for V2X sidelink communication or cross-carrier resource configurations, the UE must not use pre-configured transmit resources. Frequencies capable of providing V2X sidelink communication resource configurations or cross-carrier configurations may be signaled in SIB21 or pre-configured by the UE. During Wireless Resource Control Idle (RRC_IDLE), the UE may prioritize frequencies providing cross-carrier resource configurations for V2X sidelink communication.

[0018] If the UE supports multiple transmit chains, the UE can transmit simultaneously on multiple carriers via PC5. If multiple frequencies are supported for V2X, the mapping between V2X service types and V2X frequencies is configured at the upper layer. The UE must ensure that V2X services are transmitted on the corresponding frequencies. For scheduled resource allocation, the gNB can schedule V2X transmissions on frequencies based on Sidelink Buffer Status Reports (BSRs), where the UE includes a destination index uniquely associated with the frequency reported to the gNB by the UE in the Sidelink UE Information Message.

[0019] V2X sidelink communication technology has been defined and is referred to as LTE V2X sidelink communication in 4G systems. V2X sidelink communication has been enhanced to support improved V2X use cases in 5G systems, and this consists of four main use case groups:

[0020] 1) Vehicle platooning allows for the dynamic configuration of vehicles moving together. All vehicles in the platooning receive information from the lead vehicle to manage the platooning. Through this information, the vehicles can move together in the same direction by driving closer than usual in a coordinated manner.

[0021] 2) Using extended sensors enables the exchange of raw or processed data collected via local sensors or live video images between vehicles, road site devices, pedestrian devices, and V2X application servers. Vehicles can enhance their awareness of the surrounding environment beyond what their own sensors can detect and gain a broader and more holistic view of local conditions. High data rates are one of the key features.

[0022] 3) Advanced driving is capable of semi-automatic or fully automatic driving. Each vehicle and / or roadside unit (RSU) shares self-awareness data obtained from local sensors with nearby vehicles, thereby enabling the vehicles to synchronize and coordinate their trajectories or maneuvers. Each vehicle also shares driving objectives with nearby vehicles.

[0023] 4) Remote driving enables remote drivers or V2X applications to operate remote vehicles for passengers who cannot drive themselves or for remote vehicles located in dangerous environments. In cases where variability is limited and routes are predictable, such as in public transportation, cloud computing-based driving can be utilized. High stability and low latency are key requirements.

[0024] Problem 1: According to the current sidelink design, Mode 2 or common TX resource pool(s) must be used if Mode 2 or common TX resources are configured in the system information (e.g., V2X SIB) and the UE is in the RRC_IDLE or RRC_INACTIVE state. Mode 1 (i.e., dedicated resources) is useful for latency-sensitive advanced V2X use cases. To allow RRC_IDLE / INACTIVE UEs to acquire Mode 1 (i.e., dedicated resources), the network may not configure the mode or common TX resource pool(s) in the system information. However, this is not an efficient approach because it triggers all V2X UEs in the RRC_IDLE or RRC_INACTIVE state and all V2X UEs interested in V2X sidelink communication to initiate an RRC connection. Therefore, an efficient method for initiating connections is required.

[0025] Problem 2: There are two Radio Access Technologies (RATs) for V2X sidelink communication. LTE V2X sidelink communication supports broadcast communication and meets limited V2X use cases. NR (new radio) V2X sidelink communication supports unicast / broadcast / groupcast communication for advanced V2X use cases.

[0026] In the NR system, the following configurations are supported.

[0027] - The gNB (or NR Cell) can configure V2X sidelink communication for the NR sidelink.

[0028] - The gNB (or NR Cell) can configure V2X sidelink communication for the LTE sidelink.

[0029] - The gNB (or NR Cell) can configure V2X sidelink communication for LTE sidelink and NR sidelink.

[0030] Scenario 1: A UE is camped in an NR cell. It broadcasts the transmit resource pool(s) for V2X sidelink communication. The RAT corresponding to these resources is an NR sidelink. The V2X service that initiated sidelink communication must use the LTE sidelink. However, depending on the current situation, the UE cannot initiate an RRC connection because the system information broadcasts the transmit resource pool(s) for V2X sidelink communication.

[0031] Scenario 2: A UE is camped in an NR cell. It broadcasts the transmit resource pool(s) for V2X sidelink communication. The RAT corresponding to these resources is an LTE sidelink. The V2X service that initiated sidelink communication must use the NR sidelink. However, depending on the current situation, the UE cannot initiate an RRC connection because the system information broadcasts the transmit resource pool(s) for V2X sidelink communication.

[0032] Scenario 3: A UE is camped in an NR cell. It broadcasts the transmission resource pool(s) for V2X sidelink communication. The RAT corresponding to these resources is either an LTE sidelink or an NR sidelink. The V2X service that initiated the sidelink communication must use the NR sidelink as well as the LTE sidelink. However, depending on the current situation, the UE cannot initiate an RRC connection.

[0033] To overcome the aforementioned problems, the trigger that initiates the RRC connection must be strengthened.

[0034] In addition, HARQ feedback is supported for unicast and groupcast communication in NR V2X sidelink communication.

[0035] Scenario 4: The transmitter, i.e., the TX UE, is in coverage, and the gNB configures a Mode 1 resource for transmission.

[0036] Basic operation: The UE transmits a sidelink (SL) BSR to the gNB. The TX UE receives a Physical Downlink Control Channel (PDCCH) from the gNB addressed by the SL V2X radio network temporary identifier (SL-V-RNTI), where the Downlink Control Information (DCI) indicates the resource for SL transmission. The UE generates a MAC Protocol Data Unit (PDU). The UE transmits the Physical SL Control Channel (PSCCH). The UE transmits an SL Transmission Block (TB) (including the MAC PDU) on the Physical SL Shared Channel (PSSCH). The Receive (RX) UE transmits SL HARQ feedback (HARQ-ACK (acknowledge) or HARQ-NACK (negative ACK)) through the Physical SL Feedback Channel (PSFCH).

[0037] Problem 3: When the TX UE receives a sidelink HARQ-NACK from the RX UE, the question arises as to how to perform HARQ retransmission, for example, how the TX UE will acquire resources for HARQ retransmission.

[0038] Problem 4: In LTE, the V2X communication source Layer 2 identifier (ID) is always included in the SL Shared Channel (SCH) MAC header of the MAC PDU. NR V2X sidelink communication supports unicast, groupcast, and broadcast communication. NR V2X supports HARQ feedback for unicast and groupcast. HARQ feedback can be enabled or disabled. Considering the characteristics of the aforementioned NR V2X communication, it is not efficient to always include the source Layer 2 ID in the SL SCH MAC header. A method is needed to determine whether to include the source Layer 2 ID in the SL SCH MAC header.

[0039] The above information is presented merely as background information to aid in understanding the content of the present disclosure. It has not been determined and has not been alleged whether any of the above may be applied as prior art in relation to the present disclosure. The problem to be solved

[0040] The embodiments of the present disclosure are to solve at least the problems and / or disadvantages mentioned above and to provide at least the advantages described below. Accordingly, one embodiment of the present disclosure provides a communication method and system for converging a 5th generation (5G) communication system to support a higher data rate than a 4th generation (4G) system.

[0041] Additional aspects will be described in part in the following description, and in part, may become apparent from this description or be learned by practicing the embodiments presented here. means of solving the problem

[0042] According to one aspect of the present disclosure, a method of user equipment (UE) for performing V2X (vehicle-to-everything) sidelink communication is provided. The method comprises the steps of: determining to transmit a first radio access technology (RAT) V2X sidelink communication at a first frequency; receiving system information for the first RAT V2X sidelink communication from a base station associated with a second RAT at a second frequency; identifying whether the system information includes transmission resources for the first RAT V2X sidelink communication at the first frequency when the first frequency corresponds to the second frequency; initiating a radio resource control (RRC) connection for the first RAT V2X sidelink communication when the system information does not include transmission resources for the first RAT V2X sidelink communication at the first frequency; transmitting a sidelink UE information message for the first RAT V2X sidelink communication to a base station when the RRC connection is established; and receiving an RRC reconfiguration message from the base station that includes transmission resources for the first RAT V2X sidelink communication at the first frequency.

[0043] According to another aspect of the present disclosure, a user equipment (UE) for performing V2X sidelink communication is provided. The UE includes a transceiver and at least one processor operably coupled to the transceiver, wherein the at least one processor determines to transmit a first Radio Access Technology (RAT) V2X sidelink communication at a first frequency, controls the transceiver to receive system information regarding the first RAT V2X sidelink communication from a base station associated with a second RAT at a second frequency, and if the first frequency corresponds to the second frequency, identifies whether the system information includes transmission resources for the first RAT V2X sidelink communication at the first frequency, and if the system information does not include transmission resources for the first RAT V2X sidelink communication at the first frequency, controls the transceiver to initiate a Radio Resource Control (RRC) connection for the first RAT V2X sidelink communication, controls the transceiver to transmit a sidelink UE information message for the first RAT V2X sidelink communication to the base station upon establishment of the RRC connection, and also controls the transceiver to receive from the base station the first It is configured to receive an RRC reconfiguration message containing transmission resources for the first RAT V2X sidelink communication at a frequency.

[0044] According to another aspect of the present disclosure, a method of a base station for performing V2X sidelink communication is provided. The method comprises the steps of: transmitting system information for a first radio access technology (RAT) V2X sidelink communication to a UE based on a second RAT at a first frequency—wherein the UE is configured to transmit the first RAT V2X sidelink communication at a second frequency—wherein the second frequency corresponds to the first frequency and the system information does not include transmission resources for the first RAT V2X sidelink communication at the second frequency, initiating a radio resource control (RRC) connection for the first RAT V2X sidelink communication; receiving a sidelink UE information message for the first RAT V2X sidelink communication from the UE upon establishing the RRC connection; and transmitting an RRC reconfiguration message to the UE that includes transmission resources for the first RAT V2X sidelink communication at the second frequency.

[0045] According to another aspect of the present disclosure, a method of a base station for performing V2X sidelink communication is provided. The base station includes a transceiver and at least one processor operably coupled to the transceiver. At least one processor controls a transceiver to transmit system information for a first radio access technology (RAT) V2X sidelink communication based on a second RAT at a first frequency to a user equipment (UE) - the UE is configured to transmit the first RAT V2X sidelink communication at a second frequency -, if the second frequency corresponds to the first frequency and the system information does not include transmission resources for the first RAT V2X sidelink communication at the second frequency, initiates a radio resource control (RRC) connection for the first RAT V2X sidelink communication, controls the transceiver to receive a sidelink UE information message for the first RAT V2X sidelink communication from the UE upon establishment of the RRC connection, and also controls the transceiver to transmit an RRC reconfiguration message containing transmission resources for the first RAT V2X sidelink communication at the second frequency to the UE. Effects of the invention

[0046] An efficient method for initiating a connection is provided. The trigger for initiating an RRC connection is improved.

[0047] A method is provided to determine whether to include a source layer-2 ID in the SL SCH MAC header.

[0048] Other aspects, advantages, and notable features of the present disclosure will become apparent to those skilled in the art from the following detailed description disclosing various embodiments of the present disclosure in conjunction with the accompanying drawings. Brief explanation of the drawing

[0049] Specific embodiments and other aspects, features and advantages of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings. FIG. 1 is an exemplary illustration of a method according to one embodiment of the present disclosure. FIG. 2 is another exemplary illustration of a method according to one embodiment of the present disclosure. FIG. 3 is another exemplary illustration of a method according to one embodiment of the present disclosure. FIG. 4 is an exemplary illustration of a method according to one embodiment of the present disclosure. FIG. 5 is another exemplary illustration of a method according to one embodiment of the present disclosure. FIG. 6 illustrates a method for NR (new radio) connection initiation triggers for V2X (vehicle-to-everything) sidelink communication according to an embodiment of the present disclosure. FIG. 7 illustrates another method for NR connection initiation triggers for V2X sidelink communication according to one embodiment of the present disclosure. FIG. 8 illustrates another method for NR connection initiation triggers for V2X sidelink communication according to one embodiment of the present disclosure. FIG. 9 illustrates another method for NR connection initiation triggers for V2X sidelink communication according to one embodiment of the present disclosure. FIG. 10 illustrates a method for LTE connection initiation triggers for V2X sidelink communication according to one embodiment of the present disclosure. FIG. 11 illustrates another method for LTE connection initiation triggers for V2X sidelink communication according to one embodiment of the present disclosure. FIG. 12 illustrates a side link (SL) bandwidth portion (BWP) and an up link (UL) BWP according to a configuration according to one embodiment of the present disclosure. FIG. 13 illustrates an LTE sidelink media access control (MAC) protocol data unit (PDU) format according to one embodiment of the present disclosure. FIG. 14 illustrates a source layer 2 transmission mechanism according to one embodiment of the present disclosure. FIG. 15 illustrates another source layer 2 transmission mechanism according to one embodiment of the present disclosure. FIG. 16 illustrates another source layer 2 transmission mechanism according to one embodiment of the present disclosure. FIGS. 17, 19, 20, 21, 22, 23 and 24 illustrate timelines of operations for requesting a retransmission SL grant according to various embodiments of the present disclosure. FIG. 18 is a signaling flow between a transmitter UE, a receiver UE, and a gNB according to one embodiment of the present disclosure. FIGS. 25 and 26 are signaling flows between a UE and a gNB for acquiring V2X SIB(s) according to embodiments of the present disclosure. FIG. 27 is a block diagram of a terminal according to one embodiment of the present disclosure. FIG. 28 is a block diagram of a base station according to one embodiment of the present disclosure. Throughout the drawings, similar reference numbers will be understood to refer to similar parts, components, and structures. Specific details for implementing the invention

[0050] The following description, with reference to the accompanying drawings, is provided to facilitate a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. While the following description includes various specific details to aid understanding, they should be considered merely illustrative. Accordingly, those skilled in the art will recognize that various changes and modifications to the various embodiments described herein may be made without departing from the scope and spirit of the present disclosure. Additionally, descriptions of known functions and configurations may be omitted for clarity and brevity.

[0051] The terms and words used in the following description and claims are not limited to their bibliographic meanings and are used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it is evident that the following description of various embodiments of the disclosure is provided merely for illustrative purposes and is not intended to limit the disclosure as defined by the appended claims and their equivalents.

[0052] It should be understood that the singular form includes plural referents unless the context clearly indicates otherwise. Thus, for example, a reference to "component surfaces" includes a reference to one or more of such surfaces.

[0053] The term "substantially" implies that the mentioned characteristics, parameters, or values ​​do not necessarily have to be achieved exactly, but deviations or variations, including, for example, tolerances, measurement errors, measurement accuracy limits, and other factors known to those skilled in the art, may occur in an amount that does not exclude the effect intended to be provided by the characteristic.

[0054] It is known to those skilled in the art that blocks of a flowchart (or sequence diagram) and combinations of flowcharts can be represented and executed by computer program instructions. These computer program instructions can be loaded onto a processor of a general-purpose computer, a special-purpose computer, or a programmable data processing unit. When loaded program instructions are executed by the processor, they produce means for performing the functions described in the flowchart. Since computer program instructions can be stored in computer-readable memory available in a special-purpose computer or a programmable data processing unit, it is also possible to produce articles that perform the functions described in the flowchart. Since computer program instructions can be loaded into a computer or a programmable data processing unit, when executed as processes, they can perform the operations of the functions described in the flowchart.

[0055] A block in a flowchart may correspond to a module, segment, or code containing one or more executable instructions that implement one or more logical functions, or to a part thereof. In some cases, the functions described by the blocks may be executed in an order different from the order in which they are listed. For example, two blocks listed in a sequence may be executed simultaneously or in reverse order.

[0056] In this description, terms such as "unit," "module," etc., may refer to software components or hardware components, such as field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs), capable of performing functions or operations. However, "unit," etc., are not limited to hardware or software. Units, etc., may reside on addressable storage media or be configured to drive one or more processors. Units, etc., may also refer to software components, object-oriented software components, class components, task components, processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, or variables. The functions provided by components and units may be combinations of smaller components and units, or may be combined with others to form larger components and units. Components and units may be configured to drive devices or one or more processors on a secure multimedia card.

[0057] Prior to the detailed description, terms or definitions necessary for understanding the present disclosure are explained. However, these terms should be interpreted in a non-limiting manner.

[0058] A base station (BS) is an entity that communicates with user equipment (UE) and may be referred to as a BS, base transceiver station (BTS), node B (NB), evolved NB (eNB), access point (AP), 5th generation (5G) NB (5GNB), or next-generation NB (gNB).

[0059] A UE is an entity that communicates with a BS and may be referred to as a UE, device, mobile station (MS), mobile equipment (ME), or terminal.

[0060] Connection initiation triggers for Mode 1 resource allocation

[0061] According to the current sidelink design, if one or more common transmit (TX) resource pools are configured in the system information (e.g., the V2X (vehicle-to-everything) System Information Block (SIB)) and a UE is in the RRC_IDLE or RRC_INACTIVE state, Mode 2 transmit resources (also known as common TX resources) must be used for V2X sidelink transmits. Mode 1 transmit resources (also known as dedicated resources) are useful for latency-sensitive advanced V2X use cases. To allow RRC_IDLE / INACTIVE UEs to acquire dedicated transmit resources, the network may not configure common TX resource pools in the system information. However, this is not an efficient approach because it triggers all V2X UEs interested in V2X sidelink transmits to initiate an RRC connection while in the RRC_IDLE or RRC_INACTIVE state.

[0062] In RRC_IDLE and RRC_INACTIVE, the UE can only access the Mode 2 (i.e., common) transmit resource pool(s) configured via system information. Therefore, in order to allow the UE to request and be configured with Mode 1 transmit resources, it is proposed that a UE interested in V2X sidelink transmission can initiate an RRC connection even if Mode 2 transmit resources are broadcast by a cell camped for a frequency (serving or non-serving) configured for the UE to transmit NR (new radio) V2X sidelink communication.

[0063] In one method of the present disclosure, the following is proposed:

[0064] - A UE that is camped in a cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmission resources initiates an RRC connection if the frequency at which the UE is configured to transmit V2X sidelink communication is associated with the camped frequency and the system information received / acquired from the camped cell (i.e., V2X SIB) includes V2X sidelink settings for the camped frequency.

[0065] - A UE that is camped in a cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmission resources initiates an RRC connection if the frequency configured for the UE to transmit V2X sidelink communication is included in the list of V2X inter-frequency information in the system information (i.e., V2X SIB) received / acquired from the camped cell.

[0066] - A UE that is camped in an NR cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmission resources for NR V2X sidelink communication initiates an RRC connection in the NR cell if the frequency configured for the UE to transmit NR V2X sidelink communication is associated with the camped frequency and also the system information received / acquired from the camped cell (i.e., V2X SIB) includes NR V2X sidelink settings for the camped frequency.

[0067] - A UE that is camped in an NR cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmission resources for NR V2X sidelink communication initiates an RRC connection in the NR cell if the frequency configured for the UE to transmit NR V2X sidelink communication is included in the list of V2X inter-frequency information in the system information (i.e., V2X SIB) received / acquired from the camped cell (i.e., NR cell).

[0068] - A UE that is camped in an LTE (long term evolution) cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmission resources for NR V2X sidelink communication initiates an RRC connection in the LTE cell if the frequency configured for the UE to transmit NR V2X sidelink communication is associated with the camped frequency and also the system information (i.e., V2X SIB) received / acquired from the camped cell (i.e., LTE cell) includes NR V2X sidelink settings for the camped frequency.

[0069] - A UE that is camped in an LTE cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmission resources for NR V2X sidelink communication initiates an RRC connection in the LTE cell if the frequency configured for the UE to transmit NR V2X sidelink communication is included in the list of V2X inter-frequency information in the system information (i.e., V2X SIB) received / acquired from the camped cell (i.e., LTE cell).

[0070] A camped cell may support only Mode 2 transmit resource configuration for the camped frequency and for other frequencies. To avoid unnecessary connection initiation for Mode 1 transmit resources, it is also proposed that the cell indicate in the system information whether Mode 1 is supported (commonly for all frequencies or individually for each frequency). In another method of the present disclosure, the following is proposed:

[0071] - A UE that is camped in a cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmit resources initiates an RRC connection if the frequency at which the UE is configured to transmit V2X sidelink communication is associated with the camped frequency and also if system information received / acquired from the camped cell (i.e., V2X SIB) includes V2X sidelink settings for the camped frequency and indicates that Mode 1 transmit resources are supported by the camped cell on the camped frequency.

[0072] - A UE that is camped in a cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmit resources initiates an RRC connection if the frequency configured for the UE to transmit V2X sidelink communication is included in the list of V2X inter-frequency information in the system information (i.e., V2X SIB) received / acquired from the camped cell and also indicates that Mode 1 transmit resources for V2X sidelink communication are supported by the camped cell at the relevant frequency.

[0073] - A UE that is camped in an NR cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmit resources for NR V2X sidelink communication initiates an RRC connection in the NR cell if the frequency configured for the UE to transmit NR V2X sidelink communication is associated with the camped frequency, and system information (i.e., V2X SIB) received / acquired from the camped cell (i.e., NR cell) includes NR V2X sidelink configuration for the camped frequency and indicates that Mode 1 transmit resources for NR V2X sidelink communication are supported by the camped cell on the camped frequency.

[0074] - A UE that is camped in an NR cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmit resources for NR V2X sidelink communication initiates an RRC connection in the NR cell if the frequency configured for the UE to transmit NR V2X sidelink communication is included in the list of V2X inter-frequency information in the system information (i.e., V2X SIB) received / acquired from the camped cell (i.e., NR cell) and also indicates that Mode 1 transmit resources for NR V2X sidelink communication are supported by the camped cell at the associated frequency.

[0075] - A UE that is camped in an LTE cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmit resources for NR V2X sidelink communication initiates an RRC connection in the LTE cell if the frequency configured for the UE to transmit NR V2X sidelink communication is associated with the camped frequency (i.e., the frequency of the camped LTE cell) and also if system information received / acquired from the camped cell (i.e., V2X SIB) includes NR V2X sidelink configuration for the camped frequency and indicates that Mode 1 transmit resources for NR V2X sidelink communication are supported by the camped cell at the camped frequency.

[0076] - A UE that is camped in an LTE cell in the RRC_IDLE / INACTIVE state and is interested in Mode 1 transmit resources for NR V2X sidelink communication initiates an RRC connection in the LTE cell if the frequency configured for the UE to transmit NR V2X sidelink communication is included in the list of V2X inter-frequency information in the system information (i.e., V2X SIB) received / acquired from the camped cell (i.e., LTE cell) and also indicates that Mode 1 transmit resources for NR V2X sidelink communication are supported by the camped cell at the associated frequency.

[0077] FIG. 1 is an exemplary illustration of a method according to one embodiment of the present disclosure.

[0078] Referring to FIG. 1, the UE is in the RRC_IDLE / INACTIVE state and is interested in V2X sidelink transmission on frequency F1. In operation 110, the UE acquires the V2X SIB(s) transmitted by the camped cell. The acquired V2X SIB contains the Mode 2 transmit resource pool(s) for frequency F1. The V2X SIB also contains information indicating that Mode 1 transmit resources are supported for frequency F1 (the Mode1SupportedInd indication may be common to all V2X frequencies or may be indicated individually for each frequency). In one embodiment, the Mode1SupportedInd indication may be ConnectionAllowedInd or ConnectionAllowedforMode1. Even if the Mode 2 transmit resource pool(s) for frequency F1 are included in the V2X SIB, if V2X sidelink transmission requires Mode 1 transmit resources and Mode 1 transmit resources are supported on frequency F1, in operation 120, the UE initiates the RRC connection setup / resumption procedure. To determine whether Mode 1 transmit resources are required for V2X sidelink transmit, a mapping between V2X services and Mode 1 / Mode 2 transmit resources may be (pre)configured. After the RRC connection is set up in Operation 120, in Operation 130, the UE transmits a Sidelink UE Information Message to the gNB / BS to indicate that it is interested in V2X sidelink transmit on frequency F1 and requires Mode 1 transmit resources. The UE may include a list of communication destinations, or at least one of a QoS flow identifier (ID) or a Quality of Service (QoS) profile ID, in the Sidelink UE Information Message. The destination list may be separated for each type (broadcast / unicast / groupcast). Alternatively, the UE may include the communication type associated with each destination instead of individual lists for each communication type.In operation 140, the gNB / BS configures V2X sidelink transmission resources (mode 1, additionally mode 2 can also be configured) and transmits information about the V2X sidelink transmission resources to the UE in an RRC reset message. In operation 150, the UE performs V2X sidelink transmission using the configured resources.

[0079] In one embodiment, if the Mode 2 transmission resource pool(s) are not included in the V2X SIB, Mode1SupportedInd may not be included in the V2X SIB.

[0080] In one embodiment, Mode1SupportedInd may not be included in the V2X SIB. When Mode 1 transmission resources are required for V2X sidelink transmission, a UE in the RRC_IDLE / INACTIVE state initiates an RRC connection.

[0081] FIG. 2 is another exemplary illustration of a method according to one embodiment of the present disclosure.

[0082] Referring to FIG. 2, the UE is in the RRC_IDLE / INACTIVE state and is interested in V2X sidelink transmission on frequency F1. In operation 210, the UE acquires the V2X SIB(s) transmitted by the camped cell. In this example, the acquired V2X SIB does not contain the Mode 2 transmit resource pool(s) for frequency F1. Since the V2X SIB does not contain the Mode 2 transmit resource pool(s) for frequency F1, the UE initiates the RRC connection setup / resumption procedure in operation 220. When the RRC connection is set up in operation 220, in operation 230, the UE transmits a sidelink UE information message to the gNB / BS to indicate that it is interested in V2X sidelink transmission on frequency F1. If Mode 1 transmit resources are required for V2X sidelink transmission, in operation 230, the UE indicates that Mode 1 transmit resources are required. The UE may include at least one of a list of communication destinations or a QoS flow ID / QoS profile ID in the sidelink UE information message. The destination list may be separated for each type (broadcast / unicast / groupcast). Alternatively, the UE may include the communication type associated with each destination instead of individual lists for each communication type. To determine whether Mode 1 transmit resources are required for V2X sidelink transmit, a mapping between V2X services and Mode 1 / Mode 2 transmit resources may be (pre)configured. In operation 240, the gNB / BS configures V2X sidelink transmit resources (Mode 1, additionally Mode 2 may also be configured) and transmits information about the V2X sidelink transmit resources to the UE in an RRC reset message. In operation 250, the UE performs V2X sidelink transmit using the configured resources.

[0083] FIG. 3 is another exemplary illustration of a method according to one embodiment of the present disclosure.

[0084] Referring to FIG. 3, the UE is in the RRC_CONNECTED state and is interested in V2X sidelink transmission at frequency F1. The UE acquires V2X SIB(s) transmitted by the camped cell. In operation 310, the UE transmits a sidelink UE information message to the gNB / BS to indicate that it is interested in V2X sidelink transmission at frequency F1. In operation 310, if Mode 1 transmission resources are required for V2X sidelink transmission, the UE also indicates that Mode 1 transmission resources are required. The UE may include at least one of a communication destination list or a QoS flow ID / QoS profile ID in the sidelink UE information message. The destination list may be separated for each type (broadcast / unicast / groupcast). Alternatively, the UE may include the communication type associated with each destination instead of individual lists for each communication type. To determine whether Mode 1 transmission resources are required for V2X sidelink transmission, a mapping between V2X services and Mode 1 / Mode 2 transmission resources can be (pre)configured. In operation 320, the gNB / BS configures V2X sidelink transmission resources (Mode 1, additionally Mode 2 may also be configured) and transmits information about the V2X sidelink transmission resources in an RRC reset message. In operation 330, the UE performs V2X sidelink transmission using the configured resources.

[0085] Connection initiation triggers for congestion control

[0086] In the RRC_IDLE / INACTIVE state, the UE performs autonomous resource selection. The eNB provides TX resource pool(s). The UE autonomously selects resource(s) from the TX resource pool based on detection. A UE in the RRC_IDLE / INACTIVE state may fail to acquire resources during congestion or transmission failures due to a very high Channel Busy Ratio (CBR). The CBR is a sub-channel where the S-RSSI exceeds a (pre)set threshold.

[0087] FIG. 4 is an exemplary illustration of a method according to one embodiment of the present disclosure.

[0088] Referring to FIG. 4, the UE is in the RRC_IDLE / INACTIVE state and is interested in V2X sidelink transmission at frequency F1. In operation 410, the UE acquires the V2X SIB(s) transmitted by the camped cell. The acquired V2X SIB contains the Mode 2 TX resource pool(s) for frequency F1. The V2X SIB also contains information about the duration during which the UE cannot select a resource, namely ResourceUnavailabilityDuration. The UE acquires the TX resource pool for V2X sidelink transmission from the V2X SIB. In operation 420, the UE performs a sense of the V2X Mode 2 TX resource pool to select a resource. In operation 430, if the UE cannot select a (sense-based) resource during the (pre)set duration (ResourceUnavailabilityDuration), the UE must initiate an RRC connection setup / resumption procedure. When the RRC connection is set up in operation 430, in operation 440, the UE transmits a sidelink UE information message to the gNB / BS to indicate that it is interested in V2X sidelink transmission on frequency F1. The UE may also include a congestion indication in the sidelink UE information message, and thus in operation 450, the network may accordingly set up the mode 1 resources or mode 2 resource pool(s) and transmit information about the mode 1 or 2 resources in an RRC reset message to the UE.

[0089] FIG. 5 is an exemplary illustration of a method according to one embodiment of the present disclosure.

[0090] Referring to FIG. 5, the UE is in the RRC_IDLE / INACTIVE state and is interested in V2X sidelink transmission at frequency F1. In operation 510, the UE acquires the V2X SIB(s) transmitted by the camped cell. The acquired V2X SIB contains the Mode 2 TX resource pool(s) for frequency F1. The V2X SIB also contains information regarding the CBR threshold for connection initiation, namely CBRThresholdforConnectionInitiation. The UE acquires the TX resource pool for V2X sidelink transmission from the V2X SIB. In operation 520, the UE performs detection on the TX resource pool and selects a resource. The UE also measures the CBR for the TX resource pool in operation 530. In operation 535, the UE determines whether the measured CBR for the TX resource pool is greater than the (pre)set threshold, namely CBRThresholdforConnectionInitiation. If the measured CBR for a TX resource pool is greater than a (pre)set threshold, the UE must initiate the RRC connection setup / resumption procedure. If there are multiple TX resource pools, and the measured CBR for all TX resource pools is greater than a (pre)set threshold, the UE must initiate the RRC connection setup / resumption procedure. After the RRC connection is set up in operation 540, in operation 550, the UE transmits a sidelink UE information message to the gNB / BS to indicate interest in V2X sidelink transmission on frequency F1. The UE may also include a congestion indication in the sidelink UE information message, and thus in operation 560, the network may accordingly set up mode 1 resources or mode 2 resource pool(s) for the UE and transmit information about the mode 1 or mode 2 resources to the UE in the RRC reset message.

[0091] NR connection initiation triggers for V2X sidelink communication

[0092] There are two Radio Access Technologies (RATs) for V2X sidelink communication. LTE V2X sidelink communication supports broadcast communication and satisfies limited V2X use cases. NR V2X sidelink communication supports unicast / broadcast / groupcast communication for advanced V2X use cases. V2X services are mapped to NR and / or LTE sidelinks. A gNB (or NR cell) can configure V2X sidelink communication settings for the NR sidelink, or a gNB (or NR cell) can configure V2X sidelink communication settings for the LTE sidelink, or a gNB (or NR cell) can configure V2X sidelink communication settings for both the LTE sidelink and the NR sidelink. To support the above settings, the NR V2X SI includes the following:

[0093] 1. NR V2X Sidelink (SL) Inter-Carrier Frequency List

[0094] - Optionally includes TX resource pool(s) for the listed frequencies

[0095] 2. LTE V2X SL Intercarrier Frequency List

[0096] - Optionally includes TX resource pool(s) for the listed frequencies

[0097] 3. NR V2X SL Settings for Serving Frequency

[0098] - TX resource pool(s) are optionally included

[0099] 4. LTE V2X SL Settings for Serving Frequency

[0100] - TX resource pool(s) are optionally included

[0101] Scenario 1: A UE is camped in a cell of the first RAT (i.e., NR) but is interested in V2X sidelink communication based on the second RAT (i.e., LTE) at the camped frequency.

[0102] FIG. 6 illustrates a method for NR connection initiation triggers for V2X sidelink communication according to one embodiment of the present disclosure.

[0103] As illustrated in FIG. 6, in one method of the present disclosure, a UE camped in an NR cell is proposed to initiate an RRC connection in the NR cell if the frequency at which the UE is configured to transmit LTE V2X sidelink communication is associated with the camped frequency (i.e., the frequency of the NR cell); and if system information (i.e., V2X SIB) received / acquired from the camped cell (i.e., the NR cell) includes LTE V2X sidelink communication settings / parameters for the camped frequency but does not include a transmission resource pool for LTE V2X sidelink settings for the camped frequency. In one embodiment, the NR cell may transmit LTE V2X sidelink communication settings / parameters and NR V2X sidelink communication settings / parameters in different V2X SIBs.

[0104] Referring to FIG. 6, a UE camped in an NR cell at frequency F1 is in an RRC_IDLE / INACTIVE state and is interested in LTE V2X sidelink transmission at frequency F1. In operation 610, the UE receives V2X SIB(s) from the NR cell at frequency F1. The V2X SIB(s) may include at least one of an NR V2X SL intercarrier frequency list, an LTE V2X SL intercarrier frequency list, an NR V2X SL configuration for the serving frequency, or an LTE V2X SL configuration for the serving frequency. Additionally, the V2X SIB(s) may optionally include NR and / or LTE TX resource pool(s) for the listed frequency or the serving frequency. Based on the received V2X SIB, the UE determines whether F1 is a camped frequency, whether an LTE V2X SL configuration has been received from the V2X SI, and whether an LTE V2X SL TX resource pool for F1 has been received. In the case of FIG. 6, it is assumed that the V2X SIB includes an LTE V2X SL configuration for F1 but does not include an LTE V2X SL TX resource pool for F1. In the case of FIG. 6 where F1 is a camped frequency, an LTE V2X SL configuration is received from the V2X SI, and an LTE V2X SL TX resource pool for F1 is not received, in operation 620, the UE initiates an NR RRC connection setup / resumption procedure. When the RRC connection is set up in operation 620, in operation 630, the UE indicates that the UE is interested in transmitting LTE V2X sidelink communication or requests resources for LTE V2X SL communication transmission by transmitting a sidelink UE information message to an NR cell (i.e., gNB) on frequency F1. In one embodiment, different sidelink UE information messages (e.g., an LTE sidelink UE information message and an NR sidelink UE information message) may be used for LTE V2X SL communication and NR V2X SL communication.Based on the received messages (LTE sidelink UE information message and NR sidelink UE information message), the gNB identifies whether the UE is interested in transmitting LTE V2X sidelink communication or NR V2X sidelink communication, and accordingly can provide resources for LTE V2X sidelink communication transmission or NR V2X sidelink communication transmission. Alternatively, the same sidelink UE information message may be used for LTE V2X SL communication and NR V2X SL communication, wherein this message includes separate fields / information elements (IE) for LTE V2X SL communication and NR V2X SL communication, and the UE includes them accordingly.

[0105] In operation 640, the gNB sets up LTE sidelink communication resources and transmits an RRC reset containing information about LTE sidelink communication transmission resources to the UE.

[0106] Scenario 2: A UE is camped in a cell of the first RAT (i.e., NR) but is interested in sidelink communication based on the second RAT (i.e., LTE) at a frequency other than the camped frequency.

[0107] FIG. 7 illustrates another method for NR connection initiation triggers for V2X sidelink communication according to one embodiment of the present disclosure.

[0108] In one method of the present disclosure as illustrated in FIG. 7, a UE camped in an NR cell is proposed to initiate an RRC connection in the NR cell if the frequency configured for the UE to transmit LTE V2X sidelink communication is included in a list of V2X inter-frequency information for LTE V2X sidelink communication broadcast in system information (i.e., V2X SIB) transmitted by the NR cell; and if the system information (i.e., V2X SIB) broadcast by the camped cell does not include a pool of transmission resources for LTE V2X sidelink communication at the associated frequency. In one embodiment, the NR cell may transmit LTE V2X sidelink communication settings / parameters and NR V2X sidelink communication settings / parameters in different V2X SIBs.

[0109] Referring to FIG. 7, a UE camped in an NR cell at frequency F1 is in an RRC_IDLE / INACTIVE state and is interested in LTE V2X sidelink transmission at frequency F2. In operation 710, the UE receives V2X SIB(s) from the NR cell at frequency F1. The V2X SIB(s) may include at least one of an NR V2X SL intercarrier frequency list, an LTE V2X SL intercarrier frequency list, an NR V2X SL configuration for a serving frequency, or an LTE V2X SL configuration for a serving frequency. Additionally, the V2X SIB(s) may optionally include NR and / or LTE TX resource pool(s) for the listed frequencies or serving frequencies. Based on the received V2X SIB, the UE determines whether F2 is a serving frequency, whether F2 is included in the LTE V2X SL frequency list, and whether an LTE V2X SL TX resource pool for F2 has been received. In the case of Fig. 7, it is assumed that the V2X SIB includes an LTE V2X SL intercarrier frequency list, and that the LTE V2X SL intercarrier frequency list includes F2 but does not include an LTE V2X SL TX resource pool for F2. In the case of Fig. 7 where F2 is not a serving frequency, F2 is included in the LTE V2X SL frequency list received from the V2X SIB, and an LTE V2X SL TX resource pool for F2 is not received, in operation 720, the UE initiates an NR RRC connection setup / resumption procedure. When the RRC connection is set up in operation 720, in operation 730, the UE indicates that the UE is interested in transmitting LTE V2X sidelink communication or requests resources for LTE V2X SL communication transmission by transmitting a sidelink UE information message to the NR cell (i.e., gNB) at frequency F1.In operation 740, the gNB sets up LTE sidelink communication transmit resources and transmits an RRC reset containing information about the LTE sidelink communication transmit resources to the UE. In one embodiment, different sidelink UE information messages (e.g., LTE sidelink UE information message and NR sidelink UE information message) may be used for LTE V2X SL communication and NR V2X SL communication. Based on the received messages (LTE sidelink UE information message and NR sidelink UE information message), the gNB identifies whether the UE is interested in LTE V2X sidelink communication transmit or NR V2X sidelink communication transmit, and accordingly may provide LTE V2X sidelink communication transmit or NR V2X sidelink communication transmit resources. Alternatively, the same sidelink UE information message may be used for LTE V2X SL communication and NR V2X SL communication, wherein this message includes separate fields / IEs for LTE V2X SL communication and NR V2X SL communication, and accordingly the UE includes them.

[0110] Scenario 3: A UE is camped in a cell of the first RAT (i.e., NR) and is interested in sidelink communication based on the first RAT (i.e., NR) at the camped frequency.

[0111] FIG. 8 illustrates another method for NR connection initiation triggers for V2X sidelink communication according to one embodiment of the present disclosure.

[0112] In one method of the present disclosure as illustrated in FIG. 8, a UE camped in an NR cell is proposed to initiate an RRC connection in the NR cell if the frequency configured for the UE to transmit NR V2X sidelink communication is associated with the camped frequency; and if system information (i.e., V2X SIB) broadcast by the camped cell includes NR V2X sidelink communication settings / parameters for the camped frequency but does not include a transmission resource pool for NR V2X sidelink communication at the camped frequency. In one embodiment, the NR cell may transmit LTE V2X sidelink communication settings / parameters and NR V2X sidelink communication settings / parameters in different V2X SIBs.

[0113] Referring to FIG. 8, a UE camped in an NR cell at frequency F1 is in an RRC_IDLE / INACTIVE state and is interested in NR V2X sidelink transmission at frequency F1. In operation 810, the UE receives V2X SIB(s) from the NR cell at frequency F1. The V2X SIB may include at least one of an NR V2X SL intercarrier frequency list, an LTE V2X SL intercarrier frequency list, an NR V2X SL configuration for a serving frequency, or an LTE V2X SL configuration for a serving frequency. Additionally, the V2X SIB may optionally include NR and / or LTE TX resource pool(s) for the listed frequencies or serving frequencies. Based on the received V2X SIB, the UE determines whether F1 is a camped frequency, whether an NR V2X SL configuration has been received from the V2X SI, and whether an NR V2X SL TX resource pool for F1 has been received. In the case of FIG. 8, it is assumed that the V2X SIB includes an NR V2X SL configuration for F1 but does not include an NR V2X SL TX resource pool for F1. In the case of FIG. 8 where F1 is a camped frequency, an NR V2X SL configuration is received from the V2X SI, and an NR V2X SL TX resource pool for F1 is not received, in operation 820, the UE initiates an NR RRC connection setup / resumption procedure. When the RRC connection is set up in operation 820, in operation 830, the UE indicates that it is interested in transmitting NR V2X sidelink communication or requests NR V2X SL communication transmission resources by transmitting a sidelink UE information message to the NR cell (i.e., gNB) on frequency F1. In operation 840, the gNB establishes the NR sidelink communication transmission resources and transmits an RRC reset containing information about the NR sidelink communication resources to the UE.In one embodiment, different sidelink UE information messages (e.g., LTE sidelink UE information message and NR sidelink UE information message) may be used for LTE V2X SL communication and NR V2X SL communication. Based on the received messages (LTE sidelink UE information message and NR sidelink UE information message), the gNB identifies whether the UE is interested in transmitting LTE V2X sidelink communication or NR V2X sidelink communication, and accordingly may provide resources for LTE V2X sidelink communication transmission or NR V2X sidelink communication transmission. Alternatively, the same sidelink UE information message may be used for LTE V2X SL communication and NR V2X SL communication, wherein this message includes separate fields / IEs for LTE V2X SL communication and NR V2X SL communication, and accordingly, the UE includes them.

[0114] Scenario 4: A UE is camped in a cell of the first RAT (i.e., NR) and is interested in sidelink communication based on the first RAT (i.e., NR) at a frequency other than the camped frequency.

[0115] FIG. 9 illustrates another method for NR connection initiation triggers for V2X sidelink communication according to one embodiment of the present disclosure.

[0116] In one method of the present disclosure as illustrated in FIG. 8, a UE camped in an NR cell is proposed to initiate an RRC connection in the NR cell if the frequency configured for the UE to transmit NR V2X sidelink communication is included in a list of V2X inter-frequency information for NR sidelink communication broadcast in system information (i.e., V2X SIB) transmitted by the NR cell; and if the system information (i.e., V2X SIB) broadcast by the camped cell does not include a pool of transmission resources for NR V2X sidelink communication at the associated frequency. In one embodiment, the NR cell may transmit LTE V2X sidelink communication settings / parameters and NR V2X sidelink communication settings / parameters in different V2X SIBs.

[0117] Referring to FIG. 9, a UE camped in an NR cell at frequency F1 is in an RRC_IDLE / INACTIVE state and is interested in an NR V2X sidelink transmission at frequency F2. In operation 910, the UE receives V2X SIB(s) from the NR cell at frequency F1. The V2X SIB may include at least one of an NR V2X SL intercarrier frequency list, an LTE V2X SL intercarrier frequency list, an NR V2X SL configuration for a serving frequency, or an LTE V2X SL configuration for a serving frequency. Additionally, the V2X SIB may optionally include NR and / or LTE TX resource pool(s) for the listed frequencies or serving frequencies. Based on the received V2X SIB, the UE determines whether F2 is a serving frequency, whether F2 is included in the NR V2X SL frequency list, and whether an NR V2X SL TX resource pool for F2 has been received. In the case of FIG. 9, it is assumed that the V2X SIB contains an NR V2X SL intercarrier frequency list, and that the NR V2X SL intercarrier frequency list contains F2 but does not contain an NR V2X SL TX resource pool for F2. In the case of FIG. 9 where F2 is not a serving frequency, F2 is included in the NR V2X SL frequency list received from the V2X SIB, and an NR V2X SL TX resource pool for F2 is not received, in operation 920, the UE initiates an NR RRC connection setup procedure. When the RRC connection is set up in operation 920, in operation 930, the UE indicates that the UE is interested in transmitting NR V2X sidelink communication or requests resources for NR V2X SL communication transmission by transmitting a sidelink UE information message to the NR cell (i.e., gNB) at frequency F1. In operation 940, the gNB sets up NR V2X sidelink communication transmission resources and transmits an RRC reset containing information about the NR sidelink communication transmission resources to the UE.In one embodiment, different sidelink UE information messages (e.g., LTE sidelink UE information message and NR sidelink UE information message) may be used for LTE V2X SL communication and NR V2X SL communication. Based on the received messages (LTE sidelink UE information message and NR sidelink UE information message), the gNB identifies whether the UE is interested in transmitting LTE V2X sidelink communication or NR V2X sidelink communication, and accordingly may provide resources for LTE V2X sidelink communication transmission or NR V2X sidelink communication transmission. Alternatively, the same sidelink UE information message may be used for LTE V2X SL communication and NR V2X SL communication, wherein this message includes separate fields / IEs for LTE V2X SL communication and NR V2X SL communication, and accordingly, the UE includes them.

[0118] LTE connection initiation triggers for V2X sidelink communication

[0119] There are two types of RATs for V2X sidelink communication. LTE V2X sidelink communication supports broadcast communication and satisfies limited V2X use cases. NR V2X sidelink communication supports unicast / broadcast / groupcast communication for advanced V2X use cases. V2X services are mapped to NR and / or LTE sidelinks. An eNB (or LTE cell) can configure V2X sidelink communication settings for the NR sidelink, or the eNB (or LTE cell) can configure V2X sidelink communication settings for the LTE sidelink, or the eNB (or LTE cell) can configure V2X sidelink communication settings for both the LTE sidelink and the NR sidelink. To support the above settings, the LTE V2X SI includes the following:

[0120] 1. NR V2X SL Intercarrier Frequency List

[0121] - Optionally includes TX resource pool(s) for the listed frequencies

[0122] 2. LTE V2X SL Intercarrier Frequency List

[0123] - Optionally includes TX resource pool(s) for the listed frequencies

[0124] 3. NR V2X SL Settings for Serving Frequency

[0125] - TX resource pool(s) are optionally included

[0126] 4. LTE V2X SL Settings for Serving Frequency

[0127] - TX resource pool(s) are optionally included

[0128] Scenario 1: A UE is camped in a cell of the second RAT (i.e., LTE) but is interested in sidelink communication based on the first RAT (i.e., NR) on the camped frequency.

[0129] FIG. 10 illustrates a method for LTE connection initiation triggers for V2X sidelink communication according to one embodiment of the present disclosure.

[0130] In one method of the present disclosure as illustrated in FIG. 10, a UE camped in an LTE cell is proposed to initiate an RRC connection in the LTE cell if the frequency configured for the UE to transmit NR V2X sidelink communication is associated with the camped frequency; and if system information (i.e., V2X SIB) broadcast by the camped cell includes an NR V2X sidelink communication setup for the camped frequency (i.e., the frequency of the LTE cell) but does not include a transmission resource pool for NR V2X sidelink communication at the camped frequency.

[0131] Referring to FIG. 10, a UE camped in an LTE cell at frequency F1 is in an RRC_IDLE / INACTIVE state and is interested in NR V2X sidelink transmission at frequency F1. In operation 1010, the UE receives V2X SIB(s) from the LTE cell at frequency F1. The V2X SIB(s) may include at least one of an NR V2X SL intercarrier frequency list, an LTE V2X SL intercarrier frequency list, an NR V2X SL configuration for a serving frequency, or an LTE V2X SL configuration for a serving frequency. Additionally, the V2X SIB(s) may optionally include NR and / or LTE TX resource pool(s) for the listed frequencies or serving frequencies. Based on the received V2X SIB, the UE determines whether F1 is a camped frequency, whether an NR V2X SL configuration was received in the V2X SIB, and whether an NR V2X SL TX resource pool for F1 was received. In the case of FIG. 10, it is assumed that the V2X SIB includes an NR V2X SL configuration for F1 but does not include an NR V2X SL TX resource pool for F1. In the case of FIG. 10 where F1 is a camped frequency, an NR V2X SL configuration is received from the V2X SI, and an NR V2X SL TX resource pool for F1 is not received, in operation 1020, the UE initiates an LTE RRC connection setup / resumption procedure. When the RRC connection is set up in operation 1020, in operation 1030, the UE indicates that the UE is interested in transmitting NR V2X sidelink communication or requests NR V2X SL communication by transmitting a sidelink UE information message to the LTE cell (i.e., eNB) on frequency F1. In operation 1040, the eNB sets up NR sidelink communication transmission resources and transmits an RRC reset containing information about the NR sidelink communication resources to the UE.It should be noted that different sidelink UE information messages (e.g., LTE sidelink UE information message and NR sidelink UE information message) may be used for LTE V2X SL communication and NR V2X SL communication. Alternatively, the same sidelink UE information message may be used for LTE V2X SL communication and NR V2X SL communication, wherein this message includes separate fields / IEs for LTE V2X SL communication and NR V2X SL communication, and accordingly, the UE includes them.

[0132] Scenario 2: A UE is camped in a cell of the second RAT (i.e., LTE) but is interested in sidelink communication based on the first RAT (i.e., NR) at a frequency other than the camped frequency.

[0133] FIG. 11 illustrates another method for LTE connection initiation triggers for V2X sidelink communication according to one embodiment of the present disclosure.

[0134] In one method of the present disclosure as illustrated in FIG. 11, a UE camped in an LTE cell is included in a list of V2X inter-frequency information for NR sidelink communication broadcast in system information (i.e., V2X SIB) transmitted by the LTE cell, whereby the frequency configured for the UE to transmit NR V2X sidelink communication is included; and furthermore, if the system information (i.e., V2X SIB) broadcast by the camped cell does not include a pool of transmission resources for NR V2X sidelink communication at the associated frequency, it is proposed to initiate an RRC connection in the LTE cell.

[0135] Referring to FIG. 11, a UE camped in an LTE cell at frequency F1 is in an RRC_IDLE / INACTIVE state and is interested in an NR V2X sidelink transmission at frequency F2. In operation 1110, the UE receives V2X SIB(s) from the LTE cell at frequency F1. The V2X SIB may include at least one of an NR V2X SL intercarrier frequency list, an LTE V2X SL intercarrier frequency list, an NR V2X SL configuration for a serving frequency, or an LTE V2X SL configuration for a serving frequency. Additionally, the V2X SIB may optionally include NR and / or LTE TX resource pool(s) for the listed frequencies or serving frequencies. Based on the received V2X SIB, the UE determines whether F2 is a serving frequency, whether F2 is included in the NR V2X SL frequency list, and whether an NR V2X SL TX resource pool for F2 has been received. In the case of FIG. 11, it is assumed that the V2X SIB includes an NR V2X SL intercarrier frequency list, and that the NR V2X SL intercarrier frequency list includes F2 but does not include an NR V2X SL TX resource pool for F2. In the case of FIG. 11 where F2 is not a serving frequency, F2 is included in the NR V2X SL frequency list received from the V2X SIB, and an NR V2X SL TX resource pool for F2 is not received, in operation 1120, the UE initiates an LTE RRC connection setup / resumption procedure. When the RRC connection is set up in operation 1120, in operation 1130, the UE indicates that the UE is interested in transmitting NR V2X sidelink communication or requests NR V2X SL communication by transmitting a sidelink UE information message to the LTE cell (i.e., eNB) on frequency F1. In operation 1140, the eNB sets up NR sidelink communication transmission resources and transmits an RRC setting containing information about the NR sidelink communication transmission resources to the UE.Note that different sidelink UE information messages (e.g., LTE sidelink UE information message and NR sidelink UE information message) may be used for LTE V2X SL communication and NR V2X SL communication. Alternatively, the same sidelink UE information message may be used for LTE V2X SL communication and NR V2X SL communication, wherein this message includes separate fields / IEs for LTE V2X SL communication and NR V2X SL communication, and accordingly, the UE includes them.

[0136] Scenario 3: A UE is camped in a cell of a second RAT (i.e., LTE) and is interested in sidelink communication based on the second RAT (i.e., LTE) at the camped frequency.

[0137] In one method of the present disclosure, a UE camped in an LTE cell is proposed to initiate an RRC connection in the LTE cell if the frequency configured for the UE to transmit LTE V2X sidelink communication is associated with the camped frequency; and if system information (i.e., V2X SIB) broadcast by the camped cell includes an LTE V2X sidelink setup for the camped frequency but does not include a transmission resource pool for LTE V2X sidelink communication on the camped frequency.

[0138] Scenario 4: A UE is camped in a cell of a second RAT (i.e., LTE) and is interested in sidelink communication based on the second RAT (i.e., LTE) at a frequency other than the camped frequency.

[0139] In one method of the present disclosure, a UE camped in an LTE cell is included in a list of V2X inter-frequency information for LTE sidelink communication that is broadcast in system information (i.e., V2X SIB) transmitted by the LTE cell, wherein the frequency configured for the UE to transmit LTE V2X sidelink communication is included in the list of V2X inter-frequency information for LTE sidelink communication; and further, if the system information (i.e., V2X SIB) broadcast by the camped cell does not include a pool of transmission resources for LTE V2X sidelink communication at the associated frequency, it is proposed to initiate an RRC connection in the LTE cell.

[0140] In NR, a Bandwidth Part (BWP) is defined for the SL, and the same SL BWP is used for sidelink transmission and reception. In licensed carriers, the SL BWP is defined separately from the Uu BWP. One SL BWP is (pre)configured for NR V2X UEs outside the carrier's RRC_IDLE and coverage areas. For UEs in RRC_CONNECTED mode, one SL BWP is active on the carrier. No signal is exchanged through the SL to enable or disable the SL BWP. Only one SL BWP is configured on the carrier.

[0141] FIG. 12 illustrates SL BWP and UL BWP according to a setting according to one embodiment of the present disclosure.

[0142] Referring to FIG. 12, depending on the setting, SL BWP and UL BWP may be a) non-overlapping, b) fully overlapping, or c) partially overlapping.

[0143] In LTE sidelink operation, if UL transmission overlaps with V2X sidelink transmission in the time domain on the same frequency (carrier), the UE prioritizes V2X sidelink transmission over UL transmission if the PPPP (proximity services (ProSe) per packet priority) of the sidelink MAC (media access control) PDU (protocol data unit) is less than a (pre)set PPPP threshold; otherwise, the UE prioritizes UL transmission over V2X sidelink transmission.

[0144] In NR, for non-overlapping active SL BWP and active UL BWP, even if UL transmission overlaps with V2X sidelink transmission in the time domain, depending on the UE's capabilities, the UE may or may not be able to transmit simultaneously on the carrier's SL BWP and UL BWP. If the UE can transmit simultaneously on the SL BWP and UL BWP and the sidelink MAC PDU satisfies specific criteria (e.g., priority is lower than a threshold, where a lower value implies higher priority), the UL transmission power can be reduced. If the UE cannot transmit simultaneously on the SL BWP and UL BWP and the sidelink MAC PDU satisfies specific criteria (e.g., priority value is lower than a threshold, where a lower value implies higher priority), V2X sidelink transmission is prioritized over UL transmission.

[0145] If active SL and UL BWPs overlap on the carrier, the UE cannot transmit SL and UL simultaneously. Therefore, the UE must assign a priority between SL and UL transmissions. The UE prioritizes V2X sidelink transmissions over UL transmissions if the sidelink MAC PDU meets specific criteria (e.g., the priority is lower than a threshold, where a lower value indicates a higher priority).

[0146] In one embodiment, when both Mode 1 and Mode 2 transmit resources are configured on the UE, the network may indicate which traffic UE uses which transmit resource. The network may indicate the communication type associated with each transmit resource type (Mode 1 / Mode 2). For example, the network may indicate that Mode 1 transmit resources are used for unicast communication, while Mode 2 transmit resources are used for broadcast / group cast. Accordingly, the UE uses the Mode 1 and Mode 2 resources configured accordingly.

[0147] Alternatively, the network may indicate a QoS profile / QoS flow ID associated with each type (Mode 1 / Mode 2) of the transmit resources. For example, the network may indicate that Mode 1 transmit resources are used for QoS flows X / Y, while Mode 2 transmit resources are used for something else. Accordingly, the UE uses the Mode 1 and Mode 2 resources configured accordingly.

[0148] Alternatively, the network may represent a Logical Channel (LCH) or Logical Channel Group (LCG) associated with each type of transmit resource (Mode 1 / Mode 2). For example, the network may indicate that Mode 1 transmit resources are used for LCH or LCG X / Y, while Mode 2 transmit resources are used for something else. Accordingly, the UE uses the Mode 1 and Mode 2 resources configured accordingly.

[0149] Alternatively, the network can indicate priorities associated with transmit resources of each type (Mode 1 / Mode 2). For example, the network can indicate that Mode 1 transmit resources are used for priorities X / Y, while Mode 2 transmit resources are used for something else. Accordingly, the UE uses the Mode 1 and Mode 2 resources configured accordingly.

[0150] Alternatively, the network may indicate a priority threshold. For example, the network may indicate that Mode 1 transmit resources are used for logical channels with a priority lower than the priority threshold, while Mode 2 transmit resources are used for others. Accordingly, the UE uses the Mode 1 and Mode 2 resources configured accordingly.

[0151] Source Layer 2 ID transmission mechanism

[0152] FIG. 13 illustrates an LTE sidelink MAC PDU format according to one embodiment of the present disclosure.

[0153] Referring to FIG. 13, in the LTE sidelink MAC PDU format, the source Layer-2 ID is always included in the SL-Shared Channel (SCH) sub-header of every MAC PDU transmitted by the V2X TX UE over the sidelink. The source Layer-2 ID is 24 bits, and the UE's access layer receives the source Layer-2 ID from the upper layer. The destination Layer-2 ID is also included in the SL-SCH sub-header of every MAC PDU transmitted by the V2X TX UE over the sidelink. The destination Layer-2 ID is 24 bits, and the UE's access layer receives the destination Layer-2 ID from the upper layer.

[0154] The Physical Sidelink Common Control Channel (PSCCH) and the Physical Sidelink Shared Channel (PSSCH) are used for data TX / RX (reception). Sidelink Control Information (SCI) is transmitted via the PSCCH. Transmission blocks (including MAC PDU) are transmitted via the PSSCH.

[0155] LTE sidelink supports only broadcast communication for V2X sidelink communication. HARQ (Hybrid Automatic Repeat Request) feedback is not supported, and the UE autonomously performs a fixed number of retransmissions. NR V2X sidelink communication supports unicast, group cast, and broadcast communication. NR V2X supports HARQ feedback for unicast and group cast. HARQ feedback can be enabled or disabled. Considering the characteristics of the aforementioned NR V2X communication, it is not efficient to always include the Source Layer 2 ID in the SL SCH MAC header. A method is required to determine whether to include the Source Layer 2 ID in the SL SCH MAC header.

[0156] Method 1:

[0157] FIG. 14 illustrates a source layer 2 transmission mechanism according to one embodiment of the present disclosure.

[0158] In one method of the present disclosure illustrated in FIG. 14, it is proposed that the TX UE include a source layer 2 ID in the MAC PDU and / or PSCCH based on the communication type associated with the transmission (broadcast, group cast, or unicast) and whether HARQ feedback for said communication type is enabled.

[0159] Referring to FIG. 14, the TX UE determines the communication type associated with the MAC PDU in operation 1410. If the MAC PDU corresponds to broadcast communication, the TX UE includes the full source layer-2 ID in the SL MAC header in operation 1420. The MAC PDU corresponds to broadcast communication if it contains MAC service data unit(s) (SDU(s)) of SL resource block(s) (RB(s)) / LCHs associated with broadcast communication.

[0160] Otherwise, if the MAC PDU corresponds to unicast communication, the TX UE determines in operation 1430 whether HARQ feedback is enabled. If HARQ feedback for unicast communication is enabled, the TX UE partitions the Source Layer-2 ID into two parts. In operation 1440, the TX UE includes the first part of the Source Layer-2 ID in the SL MAC header. In operation 1450, the TX UE includes the second part of the Source Layer-2 ID in the PSCCH. The second part of the Source Layer-2 ID may be used to mask the Cyclic Redundancy Check (CRC) of the PSCCH. The second part of the Source Layer-2 ID is included in the SCI of the PSCCH, or the second part of the Source Layer-2 ID is further divided into two parts. One part is used to mask the CRC of the PSCCH, and the other part is included in the SCI of the PSCCH. In one embodiment, the first part may be the 'X' LSBs of the source layer-2 ID, and the second part includes the remaining bits of the source layer-2 ID. Otherwise, i.e., when HARQ feedback for unicast communication is disabled, the TX UE includes the full source layer-2 ID in the SL MAC header in operation 1460. The MAC PDU corresponds to unicast communication if it includes the MAC SDU(s) of the SL RB(s) / LCHs associated with broadcast unicast communication.

[0161] Otherwise, if the MAC PDU corresponds to a group cast communication, the TX UE determines whether to enable HARQ feedback in operation 1430. If HARQ feedback for group cast communication is enabled, the TX UE partitions the source Layer-2 ID into two parts. In operation 1440, the TX UE includes the first part of the source Layer-2 ID in the SL MAC header. In operation 1450, the TX UE includes the second part of the source Layer-2 ID in the PSCCH. The second part of the source Layer-2 ID may be used to mask the CRC of the PSCCH, or the second part of the source Layer-2 ID may be included in the SCI of the PSCCH, or the second part of the source Layer-2 ID may be further divided into two parts. One part is used to mask the CRC of the PSCCH, and the other part is included in the SCI of the PSCCH. In one embodiment, the first part may be the 'X' LSB of the source layer-2 ID, and the second part contains the remaining bits of the source layer-2 ID. Otherwise, i.e., when HARQ feedback for group cast communication is disabled, the TX UE includes the full source layer-2 ID in the SL MAC header in operation 1460. The MAC PDU corresponds to group cast communication if it contains the MAC SDU(s) of the SL RB(s) / LCHs associated with group cast communication.

[0162] Whether HARQ feedback is enabled for unicast communication can be configured by the gNB via system information or via dedicated RRC signaling. Alternatively, this may be pre-configured.

[0163] Whether HARQ feedback is enabled for group cast communication can be configured by the gNB via system information or via dedicated RRC signaling. Alternatively, this may be pre-configured.

[0164] In this method, depending on the communication type associated with the transmission (broadcast, group cast, or unicast) and whether HARQ feedback is enabled for that communication type, the entire source layer-2 ID is included in the MAC PDU or a part of the source layer-2 ID is included, as summarized in Table 1 below.

[0165] Communication type Source Layer-2 ID in SL SCH MAC header Broadcast (no HARQ feedback) Full source layer-2 ID Unicast with feedback The first part of the Source Layer-2 ID in the MAC header and the second part of the Source Layer-2 ID in the PSCCH Unicast without feedback Full source layer-2 ID Groupcast with feedback The first part of the Source Layer-2 ID in the MAC header and the second part of the Source Layer-2 ID in the PSCCH Groupcast without feedback Full source layer-2 ID

[0166] To enable the receiver to determine whether the MAC header contains a full Source Layer 2 ID or a partial Source Layer 2 ID, the following approach is proposed:

[0167] 1) One bit (or version number) of the MAC header may indicate whether the header contains all or part of the source layer-2 ID.

[0168] 2) One bit of SCI(PSCCH) can indicate whether the SCI contains part of the Source Layer-2 ID. Bit = 1 indicates that the SCI contains part of the Source Layer-2 ID; the MAC header contains other parts. Bit = 0 indicates that the SCI does not contain part of the Source Layer-2 ID; the MAC header contains the entire Source Layer-2 ID. Instead of including this bit in the SCI, it may be included in the CRC mask.

[0169] 3) A 1-bit HARQ feedback type can be included in the SCI(PSCCH). Bit = 0 means no HARQ feedback, indicating that the MAC header contains the full Source Layer-2 ID; and that the SCI does not contain any part of the Source Layer-2 ID. Bit = 1 means HARQ feedback, indicating that the SCI contains a part of the Source Layer-2 ID; and that the MAC header contains a different part. Instead of including it in the SCI, this bit can be included in the CRC mask.

[0170] 4) SCI format X may be for the case of HARQ feedback or for the case where the SCI contains part of the source layer-2 ID. SCI format Y may be used in other cases (i.e., HARQ feedback or the MAC header does not contain the full source layer-2 ID; and the SCI does not contain part of the source layer-2 ID).

[0171] 5) Communication types (unicast, broadcast, groupcast) and HARQ feedback types (feedback or no feedback) may be included in PSCCH (in SCI and / or CRC).

[0172] Method 2:

[0173] FIG. 15 illustrates another source layer 2 transmission mechanism according to one embodiment of the present disclosure.

[0174] In one method of the present disclosure as illustrated in FIG. 15, it is proposed that the TX UE include a source layer-2 ID in the MAC PDU and / or PSCCH based on the communication type associated with the transmission (broadcast, group cast, or unicast) and whether HARQ feedback for said communication type is enabled.

[0175] Referring to FIG. 15, the TX UE determines the communication type associated with the MAC PDU in operation 1510. If the MAC PDU corresponds to broadcast communication, in operation 1520 the TX UE includes the full source layer-2 ID in the SL MAC header. The MAC PDU corresponds to broadcast communication if it includes the MAC SDU(s) of the SL RB(s) / LCHs associated with broadcast communication.

[0176] Otherwise, if the MAC PDU corresponds to unicast communication, the TX UE determines in operation 1530 whether HARQ feedback is enabled. If HARQ feedback for unicast communication is enabled, the TX UE does not include the source layer-2 ID in the SL MAC header in operation 1540, but includes the full source layer-2 ID in the PSCCH. Otherwise, i.e., if HARQ feedback for unicast communication is disabled, the TX UE includes the full source layer-2 ID in the SL MAC header in operation 1550. The MAC PDU corresponds to unicast communication if it contains the MAC SDU(s) of the SL RB(s) / LCHs associated with unicast communication.

[0177] Otherwise, if the MAC PDU corresponds to group cast communication, the TX UE determines in operation 1530 whether HARQ feedback is enabled. If HARQ feedback for group cast communication is enabled, the TX UE does not include the source layer-2 ID in the SL MAC header in operation 1540, but includes the full source layer-2 ID in the PSCCH. Otherwise, i.e., if HARQ feedback for group cast communication is disabled, the TX UE includes the full source layer-2 ID in the SL MAC header in operation 1550. The MAC PDU corresponds to unicast communication if it contains the MAC SDU(s) of the SL RB(s) / LCHs associated with group cast communication.

[0178] In this method, depending on the communication type associated with the transmission (broadcast, group cast, or unicast) and whether HARQ feedback is enabled for that communication type, the full source layer-2 ID is included in the MAC PDU or PSCCH as summarized in Table 2 below.

[0179] Communication type Source Layer-2 ID in SL SCH MAC header Broadcast) Full source layer-2 ID in MAC header Broadcast (no HARQ feedback) Full source layer-2 ID in PSCCH not present in MAC header Unicast without feedback Full source layer-2 ID in MAC header Groupcast with feedback Full source layer-2 ID in PSCCH not present in MAC header Groupcast without feedback Full source layer-2 ID in MAC header

[0180] To enable the receiver to determine whether to include the full source Layer 2 ID in the MAC header, the following approach is proposed:

[0181] 1) One bit of the MAC header may indicate whether the MAC header contains the full source layer-2 ID.

[0182] 2) A 1 bit of SCI (PSCCH) can indicate whether the SCI contains the full Source Layer-2 ID. Bit = 1 indicates that the SCI contains the full Source Layer-2 ID; the MAC header contains other parts. Bit = 0 indicates that the SCI does not contain the Source Layer-2 ID; the MAC header contains the full Source Layer-2 ID. This bit may also be included in the CRC mask of the PSCCH instead of the SCI.

[0183] 3) A 1-bit HARQ feedback type can be included in the SCI (PSCCH). Bit = 0 means no HARQ feedback, indicating that the MAC header contains the full Source Layer-2 ID; and that the SCI does not contain the Source Layer-2 ID. Bit = 1 means HARQ feedback, indicating that the SCI contains the full Source Layer-2 ID; and that the MAC header does not contain the Source Layer-2 ID. This bit may also be included in the CRC mask of the PSCCH instead of the SCI.

[0184] 4) SCI format X may be for the case of HARQ feedback or for the case where the SCI includes a source layer-2 ID. SCI format Y may be used in other cases (i.e., HARQ feedback or the MAC header does not include the full source layer-2 ID; or the SCI does not include the source layer-2 ID).

[0185] 5) Communication types (unicast, broadcast, groupcast) and HARQ feedback types (feedback or no feedback) may be included in PSCCH (in SCI and / or CRC).

[0186] Whether HARQ feedback is enabled for unicast communication can be configured by the gNB via system information or via dedicated RRC signaling. Alternatively, this can be pre-configured.

[0187] Whether HARQ feedback is enabled for groupcast communication can be configured by the gNB via system information or via dedicated RRC signaling. Alternatively, this may be pre-configured.

[0188] Method 3:

[0189] FIG. 16 illustrates another source layer 2 transmission mechanism according to one embodiment of the present disclosure.

[0190] In one method of the present disclosure as illustrated in FIG. 16, it is proposed that the TX UE include a source layer-2 ID in the MAC PDU and / or PSCCH based on the communication type (broadcast or group cast or unicast) associated with the transmission.

[0191] Referring to FIG. 16, the TX UE determines the communication type associated with the MAC PDU in operation 1610. If the MAC PDU corresponds to broadcast communication, the TX UE includes the full source layer-2 ID in the SL MAC header in operation 1620. The MAC PDU corresponds to broadcast communication if it contains the MAC SDU(s) of the SL RB(s) / LCHs associated with broadcast communication.

[0192] Otherwise, if the MAC PDU corresponds to unicast or groupcast communication, the TX UE partitions the source Layer-2 ID into two parts. In operation 1630, the TX UE includes the first part of the source Layer-2 ID in the SL MAC header. In operation 1640, the TX UE includes the second part of the source Layer-2 ID in the PSCCH. The second part of the source Layer-2 ID may be used to mask the CRC of the PSCCH, or the second part of the source Layer-2 ID may be included in the SCI of the PSCCH, or the second part of the source Layer-2 ID may be further divided into two parts. One part is used to mask the CRC of the PSCCH, and the other part is included in the SCI of the PSCCH. In one embodiment, the first part may be the 'X' LSB of the source Layer-2 ID, and the second part includes the remaining bits of the source Layer-2 ID. A MAC PDU corresponds to a unicast or groupcast communication if it includes MAC SDU(s) of SL RB(s) / LCHs associated with each unicast or groupcast communication.

[0193] In this method, depending on the communication type associated with the transmission (broadcast, group cast, or unicast), the whole or part of the source Layer-2 ID is included in the MAC PDU as summarized in Table 3 below.

[0194] Communication type Source Layer-2 ID in SL SCH MAC header Broadcast Full source layer-2 ID in MAC header Unicast The first part of the Source Layer-2 ID in the MAC header and the second part of the Source Layer-2 ID in the PSCCH groupcast The first part of the Source Layer-2 ID in the MAC header and the second part of the Source Layer-2 ID in the PSCCH

[0195] To enable the receiver to determine whether the MAC header contains a full Source Layer 2 ID or a partial Source Layer 2 ID, the following approach is proposed:

[0196] 1) One bit of the MAC header may indicate whether the header contains all or part of the source layer-2 ID.

[0197] 2) A 1 bit of SCI (PSCCH) can indicate whether the SCI contains part of the Source Layer-2 ID. Bit = 1 indicates that the SCI contains part of the Source Layer-2 ID; the MAC header contains other parts. Bit = 0 indicates that the SCI does not contain part of the Source Layer-2 ID; the MAC header contains the entire Source Layer-2 ID. This bit may also be included in the CRC mask of the PSCCH instead of the SCI.

[0198] 3) SCI format X may be for cases where part of the Source Layer-2 ID is included in the SCI. SCI format Y may be used for other cases (i.e., the MAC header includes the full Source Layer-2 ID; and the SCI does not include the Source Layer-2 ID).

[0199] 4) Communication types (unicast, broadcast, group cast) may be included in PSCCH (SCI and / or CRC).

[0200] Method 4:

[0201] In one method of the present disclosure, it is proposed that the TX UE include a source layer-2 ID in the MAC PDU and / or PSCCH based on the communication type (broadcast or group cast or unicast) associated with the transmission.

[0202] If the MAC PDU corresponds to a broadcast communication, the TX UE includes the full source layer-2 ID in the SL MAC header.

[0203] Otherwise, if the MAC PDU corresponds to unicast or group cast communication, the TX UE does not include the source Layer 2 ID in the SL MAC header. The TX UE includes the full source Layer 2 ID in the PSCCH.

[0204] In this method, depending on the communication type (broadcast, group cast, or unicast), the source layer-2 ID may or may not be included in the MAC PDU as summarized in Table 4 below.

[0205] Communication type Source Layer-2 ID in SL SCH MAC header Broadcast Full source layer-2 ID in MAC header Unicast Full source layer-2 ID in PSCCH not present in MAC header groupcast Full source layer-2 ID in PSCCH not present in MAC header

[0206] To enable the receiver to determine whether the MAC header contains a full Source Layer 2 ID or a partial Source Layer 2 ID, the following approach is proposed:

[0207] 1) One bit of the MAC header may indicate whether the header contains the full source layer-2 ID.

[0208] 2) A 1 bit of SCI (PSCCH) can indicate whether the SCI contains the full Source Layer 2 ID. Bit = 1 indicates that the SCI contains the Source Layer 2 ID; and the MAC header does not contain the Source Layer 2 ID. Bit = 0 indicates that the SCI does not contain the Source Layer 2 ID; and the MAC header contains the full Source Layer 2 ID. This bit may also be included in the CRC mask of the PSCCH instead of the SCI.

[0209] 3) SCI format X may be for cases where the SCI includes a Source Layer-2 ID. SCI format Y may be used for other cases (i.e., the MAC header includes the full Source Layer-2 ID; and the SCI does not include the Source Layer-2 ID).

[0210] 4) Communication types (unicast, broadcast, group cast) may be included in PSCCH (SCI and / or CRC).

[0211] In one method, regardless of whether the MAC PDU corresponds to unicast, group cast, or broadcast communication, the TX UE does not include the source Layer 2 ID in the SL MAC header. The TX UE includes the full source Layer 2 ID in the PSCCH.

[0212] Resources for HARQ retransmission

[0213] In NR V2X sidelink communication, HARQ feedback is supported for unicast and groupcast communication.

[0214] Scenario: The transmitter, i.e., the TX UE, is in coverage, and the gNB configures a Mode 1 resource for transmission.

[0215] Basic operation: The UE transmits an SL buffer status report (BSR) to the gNB. The TX UE receives a Physical Downlink Control Channel (PDCCH) from the gNB addressed by the SL V2X radio network temporary identifier (SL-V-RNTI), where the Downlink Control Information (DCI) indicates the resource for SL transmission. The UE generates a MAC PDU. The UE transmits a PSCCH. The UE transmits an SL transmission block (TB) (including the MAC PDU) on the PSSCH. The RX UE transmits SL HARQ feedback (HARQ-ACK (acknowledge) or HARQ-NACK (negative ACK)) through the Physical SL Feedback Channel (PSFCH).

[0216] Problem: When the TX UE receives a sidelink HARQ-NACK from the RX UE, the question arises as to how to perform HARQ retransmission, for example, how the TX UE will acquire the resources for HARQ retransmission.

[0217] Method 1: In one method of the present disclosure, it is proposed that a gNB configures scheduling request (SR) resource(s) for requesting an SL grant for HARQ retransmission. If multiple SR configurations for an SL are signaled, the gNB may indicate which of these SR configuration(s) is used to request an SL grant for HARQ retransmission. When a sidelink HARQ-NACK is received from an RX UE, the UE transmits an SR from the SR resource configured to request an SL grant for HARQ retransmission. Upon receiving the SR, the gNB transmits a PDCCH indicating an SL grant for HARQ retransmission.

[0218] FIG. 17 illustrates a timeline of an operation requesting an SL grant for retransmission, and FIG. 18 illustrates a corresponding signaling flow between a transmitter UE, a receiver UE, and a gNB according to one embodiment of the present disclosure.

[0219] Referring to FIG. 18, the gNB transmits an RRC reset message to the TX UE in operation 1810. The RRC reset message contains information regarding SR settings for requesting a HARQ retransmission resource, for example, SR resources for retransmission. The gNB transmits an SL grant via the PDCCH in operation 1820. In operation 1830, the TX UE transmits control information via the PSCCH and an SL TB via the PSSCH to the RX UE based on the SL grant. If the RX UE does not receive the SL TB from the TX UE, the RX UE transmits an SL HARQ-NACK to the TX UE in operation 1840. When the TX UE receives the HARQ-NACK from the RX UE, the TX UE transmits an SR for the HARQ retransmission resource to the gNB based on the SR settings in operation 1850. The gNB transmits an SL grant via the PDCCH in operation 1860. In operation 1870, the TX UE transmits control information from the PSCCH and the SL TB from the PSSCH to the RX UE based on the SL grant. When the RX UE receives the SL TB from the TX UE, the RX UE transmits the SL HARQ-ACK to the TX UE in operation 1880.

[0220] When a gNB allocates multiple SL grants in sequence, upon receiving an SR, the gNB may not be able to identify which SL grant UE is requesting retransmission.

[0221] FIG. 19 illustrates a timeline of operations for requesting an SL grant for retransmission according to one embodiment of the present disclosure.

[0222] Referring to FIG. 19, the gNB allocates two SL grants, and the TX UE transmits two transmission blocks to the Receiver UE based on these SL grants. The TX UE receives a HARQ-ACK for transmission based on SL grant 1 and a HARQ-NACK for transmission based on SL grant 2. When the UE receives a sidelink HARQ-NACK from the RX UE, the UE transmits an SR from an SR resource configured to request an SL grant for HARQ retransmission. However, upon receiving the SR, the gNB cannot identify whether the SR is for a request for a HARQ retransmission resource for SL grant 1 or for a request for a HARQ retransmission resource for SL grant 2.

[0223] To overcome the above-mentioned problem, the present disclosure proposes including a grant index in a DCI-assigned SL grant as illustrated in the timeline of FIG. 20. In particular, referring to FIG. 20, SR configuration(s) to be used for an SL grant request for HARQ retransmission are linked to the grant index. gNB indicates which SR configuration(s) correspond to which grant index(s). Upon receiving a sidelink HARQ-NACK for HARQ transmission corresponding to an SL grant having grant index x, the UE transmits an SR from the SR resource of the SR configuration corresponding to grant index x.

[0224] A HARQ-NACK for transmission corresponding to Grant Index 2 is received, and thus the UE transmits the SR using the SR resources of the SR configuration linked to Grant Index 2. The first available SR resource in the SR configuration linked to Grant Index 2 is used for the SR transmission.

[0225] To overcome the above problem, in another embodiment, it is proposed that each SL HARQ feedback be associated with an SR resource that is initially available (i.e., not associated with other HARQ feedbacks and exists after the location (time) of the HARQ feedback) for an SR configuration requesting HARQ retransmission.

[0226] FIG. 21 illustrates a timeline of operations for requesting a retransmission SL grant according to one embodiment of the present disclosure.

[0227] Referring to FIG. 21, HARQ feedback for transmission based on SL Grant 1 is associated with SR resource R3. HARQ feedback for transmission based on SL Grant 2 is associated with SR resource R4. Note that SR resource R3 occurs at a time after the HARQ feedback for transmission based on SL Grant 2, but it cannot be used because it is associated with the HARQ feedback for transmission based on SL Grant 1. Therefore, upon receiving the HARQ-NACK for transmission based on SL Grant 2, the UE transmits an SR from SR resource R4.

[0228] In another embodiment, to overcome the above problem, it is proposed that the interval between SL grants be greater than or equal to the period of at least the SR resource in the SR configuration requesting HARQ retransmission. Upon reception of the SL HARQ-NACK, the UE transmits an SR to the earliest available SR resource in the SR configuration to request HARQ retransmission.

[0229] Method 2: In another method of the present disclosure, upon receiving a sidelink HARQ-NACK, it is proposed that the UE transmit a MAC control element (CE) to the gNB to request an SL grant for HARQ retransmission.

[0230] FIG. 22 illustrates a timeline of operations for requesting a retransmission SL grant according to one embodiment of the present disclosure.

[0231] MAC CE includes an SL grant index (the grant index is included in the DCI scheduling SL grant), or MAC CE includes the system frame number (SFN) / slot / symbol of the SL grant corresponding to the transmission request made by the UE. MAC CE may include retransmission requests for multiple SL grants.

[0232] Referring to FIG. 22, a HARQ-NACK for transmission corresponding to Grant Index 2 is received, and thus the UE transmits a MAC CE containing Grant Index 2.

[0233] Method 3: In another method of the present disclosure, it is proposed that the gNB configure both Mode 1 (i.e., dedicated resources) and Mode 2 resources (common TX resources, resource selection based on sensing) for the UE. When the UE receives a sidelink HARQ-NACK for transmission based on a Mode 1 grant, the UE selects a resource from the Mode 2 resource pool for HARQ retransmission. In another embodiment, upon receiving a sidelink HARQ-NACK for transmission based on a Mode 1 grant, if the UE does not receive a Mode 1 SL grant within a (pre-)configured time, the UE selects a resource from the Mode 2 resource pool.

[0234] Method 4: In another method of the present disclosure, it is proposed that a gNB autonomously provide an SL grant for HARQ retransmission. The gNB configures SR resource(s) for suspending the SL grant for HARQ retransmission. The SR configuration(s) used to suspend the SL grant for HARQ retransmission are linked to a grant index. The gNB indicates which SR configuration(s) correspond to which grant index(s). When a sidelink HARQ-ACK for HARQ transmission corresponding to an SL grant having grant index x is received, the UE transmits an SR from the SR resource of the SR configuration corresponding to grant index x.

[0235] FIG. 23 illustrates a timeline of operations for requesting a retransmission SL grant according to one embodiment of the present disclosure.

[0236] Referring to FIG. 23, a HARQ-ACK for transmission corresponding to Grant Index 1 is received, and thus the UE transmits an SR from an SR resource of the SR configuration corresponding to Grant Index 1.

[0237] In an alternative embodiment, upon receiving a sidelink HARQ-ACK, the UE transmits a MAC CE to the gNB to stop the SL grant for HARQ retransmission. The MAC CE includes an SL grant index, or the MAC CE includes an SFN / slot / symbol of the SL grant corresponding to the UE's request to stop providing the grant for retransmission.

[0238] FIG. 24 illustrates a timeline of operations for requesting a retransmission SL grant according to one embodiment of the present disclosure.

[0239] Referring to FIG. 24, a HARQ-ACK for transmission corresponding to Grant Index 1 is received, and thus the UE transmits a MAC CE containing Grant Index 1.

[0240] It should be noted that the above methods can also be used for Mode 1 configuration grants for sidelinks. Instead of a grant index, a configured grant configuration index is used. Each configured grant configuration is associated with an index. This is the index of an item that is explicitly signaled or is in the configuration list.

[0241] SL RBs / LCHs and SL RB configuration for NR sidelink

[0242] In the case of SL unicast, groupcast, and broadcast, the QoS parameters of V2X packets are directed to the access layer (AS) by the upper layer.

[0243] Unicast communication: At the transmitter, the upper layers map packet(s) to PC5 QoS flow(s) via PC5 QoS rules and forward the packets to the AS using the associated QoS flow identifier(s) (i.e., PC5 QoS flow identifier (QFI)). The AS obtains SL radio bearer (SLRB) configurations via gNB / ng-eNB or pre-configuration. These SLRB configurations include PC5 QoS flows for SLRB mapping, SDAP (service data adaptation protocol) / PDCP (packet data convergence protocol) / RLC (radio link control) / LCH configurations, etc. The UE of the AS establishes the SLRB(s) associated with the PC5 QFI(s) of the packet(s) and maps the available packet(s) to the established SLRB(s).

[0244] Group Cast / Broadcast Communication: At the transmitter, the PC5 QoS profile of each incoming V2X packet is configured by the upper layers and submitted to the AS. The AS obtains SLRB configurations via gNB / ng-eNB or pre-configuration. These SLRB configurations may include PC5 QoS profiles for SLRB mapping, PDCP / RLC / LCH configurations, etc. The UE of the AS establishes the SLRB(s) associated with the QoS profile of the packet(s) and maps the packet(s) to the established SLRB(s).

[0245] In the case of SL unicast, the mapping between PC5 QoS flows and SLRB configurations is configured or pre-configured by the gNB at least via dedicated signaling. Similarly, in the case of SL groupcast / broadcast, the mapping between PC5 QoS profiles and SLRB configurations is configured or pre-configured by the gNB at least via dedicated signaling.

[0246] In one embodiment, for a UE in an RRC IDLE / INACTIVE state, an SI broadcast by a camped cell provides transmission resources for a frequency configured for the UE to transmit V2X sidelink unicast communication, and if a mapping between PC5 QoS flows and SLRB configurations is not broadcast in the system information, the UE uses a pre-configured mapping between PC5 QoS flows and SLRB configurations. If a mapping between PC5 QoS flows and SLRB configurations is broadcast in the system information, the UE uses this mapping obtained from the SI.

[0247] In another embodiment, for a UE in an RRC IDLE / INACTIVE state, if the SI broadcast by the camped cell provides transmit resources for the frequency configured for the UE to transmit V2X sidelink unicast communication, and the mapping between PC5 QoS flows and SLRB configurations is not broadcast in the system information, the UE initiates an RRC connection. After initiating the connection, the UE obtains the mapping between PC5 QoS flows and SLRB configurations from the gNB in ​​dedicated signaling. If the mapping between PC5 QoS flows and SLRB configurations is broadcast in the system information, the UE uses this mapping obtained from the SI.

[0248] For unicast / groupcast communication, SL RB configurations can be pre-configured, use dedicated RRC signaling, or be configured by the gNB via system information. It is assumed that the transmitter can provide SL RB configuration(s) to the receiver(s) during connection setup.

[0249] Scenario: The UE is in the RRC_CONNECTED state.

[0250] Packets of a communication type (e.g., unicast) arrive at destination 1. At the transmitter, the upper layers map the packet(s) to a PC5 QoS flow X and forward the packet(s) to the AS using the associated QoS flow identifier(s) (i.e., PC5 QFI X).

[0251] AS sends the SLRB configuration request to gNB.

[0252] The gNB provides SLRB configuration 1. SLRB configuration 1 maps to PC5 QFI X and includes SDAP / PDCP / RLC / LCH configurations, etc.

[0253] The UE of the AS establishes SLRB 1 associated with PC5 QFI X for Destination 1 based on SLRB configuration 1. Packets from PC5 QFI X for Destination 1 are mapped to this SLRB.

[0254] After some time, packets for unicast communication arrive at destination 2. At the transmitter, the upper layers map the packet(s) to PC5 QoS flow X according to QoS rules and forward the packet(s) to AS using the associated QoS flow identifier(s) (i.e., PC5 QFI X).

[0255] In this scenario, there are two options.

[0256] Option 1: The UE sends an SLRB configuration request to the gNB containing the destination ID and PC5 QFI. The gNB provides SLRB configuration 2. SLRB configuration 2 maps to PC5 QFI X and includes SDAP / PDCP / RLC / LCH configurations, etc. The UE in the AS establishes an SLRB associated with PC5 QFI X for destination 2 based on SLRB configuration 2.

[0257] Option 2: The UE does not send an SLRB configuration request to the gNB. The UE of the AS establishes SLRB 2 associated with PC5 QFI X for Destination 2 based on SLRB configuration 1. Packets of PC5 QFI X for Destination 2 are mapped to this SLRB. For a given communication type (e.g., unicast, groupcast), upon receiving the first packet of a PC5 QoS flow / QoS profile from the upper layer for the destination, if the UE has an SLRB configuration corresponding to that PC5 QoS flow / QoS profile and communication type, the UE establishes a new SLRB using the SLRB configuration corresponding to that PC5 QoS flow / QoS profile and communication type. Otherwise, the UE sends an SLRB configuration request to the gNB.

[0258] FIGS. 25 and 26 are signaling flows between a UE and a gNB for acquiring V2X SIB(s) according to various embodiments of the present disclosure.

[0259] In NR, the SI framework depends on the network implementation as to whether SI messages are broadcast or provided on demand. Whether SI messages are broadcast or provided on demand is indicated in SIB1. If SI messages containing V2X SIB(s) are not broadcast (i.e., provided on demand), the RRC_CONNECTED UE acquires the V2X SIB(s).

[0260] Referring to FIG. 25, the UE is in RRC_CONNECTED and must acquire a non-broadcast V2X SIB(s). In operation 2510, the UE sends an RRCSystemInfoRequest message to the gNB. The RRCSystemInfoRequest message is transmitted over a dedicated control channel (DCCH). The RRCSystemInfoRequest includes a request for SI message(s) associated with the V2X SIB, or a request for the V2X SIB(s). The mapping between the V2X SIBs and SI messages is indicated in SIB1. In operation 2520, the gNB sends an RRC reconfiguration message to the UE. The RRC reconfiguration message contains the requested V2X SIB(s) or SI message(s). The gNB may also broadcast SI message(s) containing the requested V2X SIB(s) in the SI window. Therefore, after sending an RRCSystemInfoRequest in the RRC_connected state, the UE also monitors SI windows that respond to the requested SI messages or the SI messages of the requested V2X SIB(s).

[0261] In the case of the embodiment based on FIG. 25, after initiating the transmission of RRCSystemInfoRequest, the UE waits for acknowledgment for the SI request only when it is in the RRC IDLE / INACTIVE state. When the UE is in the RRC_CONNECTED state, the UE does not wait for acknowledgment for the SI request. In RRC_IDLE / INACTIVE, RRCSystemInfoRequest is transmitted over the Common Control Channel (CCCH) and includes a request for SI message(s) associated with V2X SIBs. When RRCSystemInfoRequest is transmitted over the CCCH, the UE receives the requested SI message in the corresponding SI windows.

[0262] Referring to FIG. 26, the UE is in RRC_CONNECTED and must acquire the non-broadcast V2X SIB(s). In operation 2610, the UE sends an RRCSystemInfoRequest message to the gNB. In operation 2620, the gNB sends an RRCSystemInfoRequest ACK to the UE. In operation 2630, the UE monitors the SI window(s) of the SI message requested during the current modification period.

[0263] In the case of the embodiment based on FIG. 26, after initiating the transmission of RRCSystemInfoRequest, if the UE is in the RRC_IDLE / INACTIVE state, the UE waits for acknowledgment of the SI request from lower layers (where the race resolution MAC CE acts as the SI request ACK). RRCSystemInfoRequest is transmitted by the IDLE / INACTIVE UE using CCCH. After receiving RRCSystemInfoRequest in message 3 (Msg3) of the CCCH SDU, the gNB transmits a race resolution MAC CE acknowledging the reception of the SI request. If the UE is in the RRC_CONNECTED state, the UE waits for the RRCSystemInfoRequest ACK message. RRCSystemInfoRequest is transmitted by the RRC_CONNECTED UE using DCCH. After receiving RRCSystemInfoRequest from the DCCH, the gNB transmits an RRCSystemInfoRequestAck acknowledging the reception of the SI request.

[0264] In the embodiment of FIG. 25, the UE may start a timer when it initiates the transmission of the RRCSystemInfoRequest. The timer is stopped when it receives an RRCReconfiguration message containing the requested SI. When the timer expires, the UE initiates the transmission of the RRCSystemInfoRequest again. If the desired SI is not received after transmitting the RRCSystemInfoRequest 'N' times, the UE may declare a Radio Link Failure (RLF). N may be configured with an SI or dedicated signaling, or may be predefined.

[0265] FIG. 27 is a block diagram of a terminal according to one embodiment of the present disclosure.

[0266] Referring to FIG. 27, the terminal includes a transceiver (2710), a controller (2720), and a memory (2730). The controller (2720) may refer to a circuit, an ASIC, an FPGA, or at least one processor. The transceiver (2710), the controller (2720), and the memory (2730) are configured to perform the operations of the UE as illustrated in the drawings (e.g., FIG. 1 through 26) or as described above. Although the transceiver (2710), the controller (2720), and the memory (2730) are illustrated as separate entities, they may be integrated on a single chip. The transceiver (2710), the controller (2720), and the memory (2730) may also be electrically connected or coupled to each other.

[0267] The transceiver (2710) can transmit and receive signals with other network entities, such as base stations, for example.

[0268] The controller (2720) can control the UE to perform functions according to the embodiments described above. For example, the controller (2720) is configured to control the transceiver (2710) to receive system information including sidelink communication information of the second RAT. In one scenario, the UE is camped in a cell of the first RAT (i.e., NR) but is interested in sidelink communication based on the second RAT (i.e., LTE) at the camped frequency. The controller (2720) is configured to initiate an RRC connection from the camped cell of the first RAT for sidelink communication according to the second RAT when the frequency at which the UE is configured to transmit sidelink communication according to the second RAT is associated with the camped frequency; and when the system information broadcast by the camped cell of the first RAT does not include transmission resources for sidelink communication according to the second RAT. In another scenario, the UE is camped in a cell of the first RAT (i.e., NR) but is interested in sidelink communication based on the second RAT (i.e., LTE) at a frequency other than the camped frequency. The controller (2720) is configured to initiate an RRC connection from the camped cell of the first RAT for sidelink communication according to the second RAT if the frequency at which the UE is configured to transmit sidelink communication according to the second RAT is included in the system information broadcast by the camped cell of the first RAT and does not include a pool of transmission resources for sidelink communication according to the second RAT for that frequency. The controller (2720) is configured to control the transceiver (2710) to transmit a sidelink UE information message for sidelink communication according to the second RAT to the camped cell of the first RAT. The controller (2720) is configured to control the transceiver (2710) to receive information about resources for sidelink communication according to the second RAT in dedicated signaling.In another scenario, the first RAT may refer to LTE, and the second RAT may refer to NR.

[0269] In one embodiment, the operations of the terminal may be implemented using a memory (2730) that stores corresponding program codes. Specifically, the terminal may be equipped with a memory (2730) for storing program codes that implement desired operations. To perform the desired operations, the controller (2720) may read and execute the program codes stored in the memory (2730) using a processor or a CPU (Central Processing Unit).

[0270] FIG. 28 is a block diagram of a base station according to one embodiment of the present disclosure.

[0271] Referring to FIG. 28, the base station includes a transceiver (2810), a controller (2820), and a memory (2830). The controller (2820) may refer to a circuit, an ASIC, an FPGA, or at least one processor. The transceiver (2810), the controller (2820), and the memory (2830) are configured to perform the operations of the gNB as illustrated in the drawings (e.g., FIG. 1 through 26) or as described above. Although the transceiver (2810), the controller (2820), and the memory (2830) are depicted as separate entities, they may be integrated into a single chip. The transceiver (2810), the controller (2820), and the memory (2830) may also be electrically connected or coupled to each other.

[0272] The transceiver (2810) can transmit and receive signals with other network entities, for example, terminals.

[0273] The controller (2820) can control the gNB to perform functions according to the embodiments described above. For example, the controller (2820) is configured to control the transceiver (2810) to broadcast system information including sidelink communication information of the second RAT. The controller (2820) is configured to control the transceiver (2810) to receive a sidelink UE information message for sidelink communication according to the second RAT to the camped cell of the first RAT. The controller (2820) is configured to control the transceiver (2810) to provide resources for sidelink communication according to the second RAT in dedicated signaling.

[0274] In one embodiment, the operations of the base station may be implemented using a memory (2830) that stores corresponding program codes. Specifically, the base station may be equipped with a memory (2830) to store program codes that implement desired operations. A controller (2820) may read and execute program codes stored in the memory (2830) using a processor or CPU to perform desired operations.

[0275] Although the present disclosure has been illustrated and described with reference to various embodiments, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Claims

Claim 1 A method performed by a UE (user equipment) of a wireless communication system, comprising: receiving a system information block containing configuration information for sidelink communication according to a second RAT from a base station associated with a first RAT (radio access technology); identifying whether the configuration information includes transmission resources for a sidelink signal according to the second RAT when the frequency configured for the UE to transmit a sidelink signal according to the second RAT corresponds to a camped frequency of the first RAT; initiating a radio resource control (RRC) connection for sidelink communication according to the second RAT when the configuration information does not include transmission resources for a sidelink signal according to the second RAT; transmitting a sidelink UE information message for sidelink communication according to the second RAT to the base station; and receiving an RRC reconfiguration message from the base station containing transmission resources for a sidelink signal according to the second RAT. Claim 2 A method according to claim 1, further comprising the step of transmitting a sidelink signal according to the second RAT to another UE based on the transmission resource. Claim 3 A method according to claim 1, characterized in that the first RAT corresponds to an LTE (long term evolution) communication system and the second RAT corresponds to an NR (new radio) communication system. Claim 4 A method according to claim 1, characterized in that the first RAT corresponds to an NR (new radio) communication system and the second RAT corresponds to an LTE (long term evolution) communication system. Claim 5 In the UE (user equipment) of a wireless communication system, a transmitting and receiving unit; A UE configured to include at least one processor coupled to the above-mentioned transceiver, wherein the at least one processor receives, through the transceiver, a system information block containing configuration information for sidelink communication according to a second RAT from a base station associated with a first RAT (radio access technology), and if the frequency configured for the UE to transmit a sidelink signal according to the second RAT corresponds to a camped frequency of the first RAT, identifies whether the configuration information includes transmission resources for a sidelink signal according to the second RAT, and if the configuration information does not include transmission resources for a sidelink signal according to the second RAT, initiates an RRC (radio resource control) connection for sidelink communication according to the second RAT, transmits a sidelink UE information message for sidelink communication according to the second RAT to the base station through the transceiver, and receives an RRC reconfiguration message containing transmission resources for a sidelink signal according to the second RAT from the base station through the transceiver. Claim 6 A UE according to claim 5, wherein the at least one processor is further configured to transmit a sidelink signal according to the second RAT to another UE through the transceiver based on the transmission resource. Claim 7 A UE according to claim 5, characterized in that the first RAT corresponds to an LTE (long term evolution) communication system and the second RAT corresponds to an NR (new radio) communication system. Claim 8 A UE according to claim 5, characterized in that the first RAT corresponds to an NR (new radio) communication system and the second RAT corresponds to an LTE (long term evolution) communication system. Claim 9 A method performed by a base station associated with a first RAT (radio access technology) of a wireless communication system, comprising: transmitting a system information block containing configuration information for sidelink communication according to a second RAT; establishing a radio resource control (RRC) connection with the UE for sidelink communication according to the second RAT when the frequency set by the UE to transmit a sidelink signal according to the second RAT corresponds to a camped frequency of the first RAT and the configuration information does not include transmission resources for the sidelink signal according to the second RAT; receiving a sidelink UE information message for sidelink communication according to the second RAT from the UE; and transmitting an RRC reset message containing transmission resources for the sidelink signal according to the second RAT to the UE. Claim 10 A method according to claim 9, characterized in that the transmission resources are used by the UE to transmit a sidelink signal according to the second RAT to another UE. Claim 11 A method according to claim 9, characterized in that the first RAT corresponds to an LTE (long term evolution) communication system and the second RAT corresponds to an NR (new radio) communication system. Claim 12 A method according to claim 9, characterized in that the first RAT corresponds to an NR (new radio) communication system and the second RAT corresponds to an LTE (long term evolution) communication system. Claim 13 A base station associated with a first RAT (radio access technology) of a wireless communication system, comprising: a transceiver; and at least one processor coupled to the transceiver, wherein the at least one processor transmits a system information block containing configuration information for sidelink communication according to a second RAT through the transceiver, and if the frequency set for a UE receiving the system information to transmit a sidelink signal according to the second RAT corresponds to a camped frequency of the first RAT and the configuration information does not include transmission resources for a sidelink signal according to the second RAT, the base station establishes an RRC (radio resource control) connection with the UE for sidelink communication according to the second RAT, receives a sidelink UE information message for sidelink communication according to the second RAT from the UE through the transceiver, and transmits an RRC reset message containing transmission resources for a sidelink signal according to the second RAT to the UE through the transceiver. Claim 14 A base station characterized in that, in paragraph 13, the transmission resources are used by the UE to transmit a sidelink signal according to the second RAT to another UE. Claim 15 A base station according to claim 13, characterized in that the first RAT corresponds to an LTE (long term evolution) communication system and the second RAT corresponds to an NR (new radio) communication system. Claim 16 A base station according to claim 13, characterized in that the first RAT corresponds to an NR (new radio) communication system and the second RAT corresponds to an LTE (long term evolution) communication system.

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