Method and apparatus for sidelink unlicensed resource allocation

Abstract

The invention relates to a transmission method implemented by user equipment (UE), in particular to a transmission method implemented by the UE. The method includes receiving channel occupancy sharing information from a second UE initiating channel occupancy. The channel occupancy sharing information comprises the remaining channel occupancy duration and one or more identifiers of one or more UEs. The method further includes determining, according to the channel occupancy sharing information, that the UE shares the channel occupancy, and transmitting, in response to the determination, a sidelink synchronization signal block (S-SSB) at a first channel occupancy time.

Description

[0001] Cross - reference to related applications

[0002] This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 422,714, filed on November 4, 2022, with the title "LTE AND NR PSFCH COEXISTENCE", and U.S. Provisional Patent Application No. 63 / 494,704, filed on April 6, 2023, with the title "METHOD AND APPARATUS FOR SIDELINK UNLICENSED RESOURCE ALLOCATION", the entire contents of which are incorporated herein by reference. Background Art

[0003] The Third Generation Partnership Project (3GPP) has been developing and standardizing several important features of the Fifth Generation (5G) New Radio (NR) access technology. In Release 16, the work item on NR Vehicle - to - Everything (V2X) wireless communication was completed, aiming to provide a 5G - compatible high - speed and reliable connection for vehicle communications. This work item provides the basis for NR sidelink communication for applications such as safety systems and autonomous driving. High data rate, low latency, and high reliability are some of the key areas of research and standardization. In Release 17, the work item "Sidelink Enhancement" was completed to further enhance the capabilities and performance of sidelink communication. A user equipment (UE) - to - UE coordination mechanism is needed, where one UE shares preferred or non - preferred resources with another UE for resource selection of the former; or when there is a conflict on the reserved resources of the UE, it sends a conflict indication to another UE. Summary of the Invention

[0004] The first aspect relates to a transmission method implemented by a user equipment (UE). The method includes: (i) receiving channel occupancy sharing information from a second UE that initiates channel occupancy, where the channel occupancy sharing information includes the remaining channel occupancy duration and one or more identifiers of one or more UEs; (ii) determining, based on the channel occupancy sharing information, that the UE shares the channel occupancy; and (iii) in response to the determination, transmitting a sidelink synchronization signal block (S-SSB) during a first channel occupancy time.

[0005] Optionally, in the above aspect, another implementation of this aspect includes: transmitting the S-SSB during the first channel occupancy time includes: transmitting the S-SSB during the remaining channel occupancy duration.

[0006] Optionally, in any of the above aspects, another implementation of this aspect includes: determining that the UE shares the channel occupancy based on the one or more identifiers of the one or more UEs.

[0007] Optionally, in any of the above aspects, another implementation of this aspect includes: determining whether the first channel occupancy time is still ongoing before determining that the UE shares the channel occupancy.

[0008] Optionally, in any of the above aspects, another implementation of this aspect includes: receiving the channel occupancy sharing information through at least one of a physical sidelink control channel (PSCCH) or a physical sidelink shared channel (PSSCH).

[0009] Optionally, in any of the above aspects, another implementation of this aspect includes: the occupancy sharing information further includes information indicating whether S-SSB transmission is allowed.

[0010] The second aspect relates to a device, including one or more processors operably coupled to a transceiver and a non-transitory memory storing programming instructions that, when executed by the one or more processors, cause the device to perform the method described in any of the above aspects.

[0011] A third aspect relates to a non-transitory computer-readable medium including a computer program product for use by a user equipment (UE). The computer program product includes computer-executable instructions stored in the non-transitory computer-readable medium. When executed by one or more processors, the computer-executable instructions cause the UE to perform the method described in any of the above aspects.

[0012] A fourth aspect relates to a method implemented by a user equipment (UE). The method includes: (i) performing Listen Before Talk (LBT) channel sensing at a first physical sidelink feedback channel (PSFCH) occasion; (ii) determining whether the LBT channel sensing fails; (iii) in response to determining that the LBT channel sensing does not fail, transmitting the PSFCH resource block; (iv) in response to determining that the LBT channel sensing fails, performing LBT channel sensing at a second PSFCH occasion; and (v) after successfully performing LBT at the second PSFCH occasion, transmitting the PSFCH resource block.

[0013] A fifth aspect relates to a user equipment (UE) including: (i) a transceiver for communicating with an access node of a wireless network and transmitting a physical sidelink feedback channel (PSFCH) resource block to another UE in the coverage area of the wireless network; (ii) one or more processors operatively coupled to the transceiver; and (iii) a non-transitory memory storing programming instructions. When executed by the one or more processors, the programming instructions cause the UE to perform the following operations: performing Listen Before Talk (LBT) channel sensing at a first PSFCH occasion; determining whether the LBT channel sensing fails; in response to determining that the LBT channel sensing does not fail, transmitting the PSFCH resource block; in response to determining that the LBT channel sensing fails, performing LBT channel sensing at a second PSFCH occasion; and after successfully performing LBT at the second PSFCH occasion, transmitting the PSFCH resource block.

[0014] The sixth aspect relates to a method implemented by a user equipment (UE). The method includes: (i) determining whether a set of first-configured physical sidelink feedback channel (PSFCH) occasions is configured to coexist with long term evolution (LTE) transmissions; (ii) in response to determining that the set of first-configured PSFCH occasions is configured to coexist with the LTE transmissions, not transmitting the PSFCH resource blocks; (iii) in response to determining that the set of first-configured PSFCH occasions is not configured to coexist with the LTE transmissions, transmitting the PSFCH resource blocks.

[0015] The seventh aspect relates to a user equipment (UE), including: (i) a transceiver configured to communicate with an access node of a wireless network and to transmit physical sidelink feedback channel (PSFCH) resource blocks to one or more UEs in a coverage area of the wireless network; (ii) one or more processors operatively coupled to the transceiver; (iii) a non-transitory memory storing programming instructions. The programming instructions, when executed by the one or more processors, cause the UE to perform the following operations: (iv) determining whether a set of first-configured PSFCH occasions is configured to coexist with long term evolution (LTE) transmissions; (v) in response to determining that the set of first-configured PSFCH occasions is configured to coexist with the LTE transmissions, not transmitting the PSFCH resource blocks; (vi) in response to determining that the set of first-configured PSFCH occasions is not configured to coexist with the LTE transmissions, transmitting the PSFCH resource blocks.

[0016] The eighth aspect relates to a method implemented by a user equipment (UE). The method includes: (i) determining whether a first channel occupancy time is still ongoing; (ii) in response to determining that the first channel occupancy time is not ongoing, using a set of first-configured physical sidelink feedback channel (PSFCH) occasions to transmit PSFCH resource blocks; (iii) in response to determining that the first channel occupancy time is still ongoing, determining whether the UE is sharing the first channel occupancy time with a second UE; (iv) in response to determining that the UE is sharing the first channel occupancy time with the second UE, using a set of second-configured PSFCH occasions to transmit the PSFCH resource blocks.

[0017] A ninth aspect relates to a user equipment (UE), comprising: (i) a transceiver for communicating with an access node of a wireless network and transmitting physical sidelink feedback channel (PSFCH) resource blocks to one or more UEs in a coverage area of the wireless network; (ii) one or more processors operatively coupled to the transceiver; (iii) a non-transitory memory storing programming instructions. The programming instructions, when executed by the one or more processors, cause the UE to perform the following operations: (iv) determining whether a first channel occupancy time is still ongoing; (v) in response to determining that the first channel occupancy time is not ongoing, transmitting the PSFCH resource blocks using a first configured set of PSFCH opportunities; (vi) in response to determining that the first channel occupancy time is still ongoing, determining whether the UE is sharing the first channel occupancy time with a second UE among the one or more UEs; (vii) in response to determining that the UE is sharing the first channel occupancy time with the second UE, transmitting the PSFCH resource blocks using a second configured set of PSFCH opportunities.

[0018] A tenth aspect relates to a user equipment (UE), comprising: (i) a transceiver for communicating with an access node of a wireless network and transmitting physical sidelink feedback channel (PSFCH) resource blocks to one or more UEs in a coverage area of the wireless network; (ii) one or more processors operatively coupled to the transceiver; (iii) a non-transitory memory storing programming instructions. The programming instructions, when executed by the one or more processors, cause the UE to perform the following operations: (iv) determining whether a first channel occupancy time is still ongoing; (v) in response to determining that the first channel occupancy time is not ongoing, transmitting the PSFCH resource blocks using a second configured set of PSFCH opportunities; (vi) in response to determining that the first channel occupancy time is still ongoing, determining whether the UE is sharing the first channel occupancy time with a second UE among the one or more UEs; (vii) in response to determining that the UE is sharing the first channel occupancy time with the second UE, transmitting the PSFCH resource blocks using a first configured set of PSFCH opportunities.

[0019] Optionally, in the above aspect, another implementation of this aspect includes: when the programming instructions are executed by the processor, the UE is further caused to perform the following operations: perform Listen Before Talk (LBT) channel sensing at at least one default PSFCH occasion.

[0020] Optionally, in any of the above aspects, another implementation of this aspect includes: when the programming instructions are executed by the processor, the UE is further caused to perform the following operations: determine whether the Listen Before Talk (LBT) channel sensing fails; in response to determining that the LBT channel sensing does not fail, transmit the PSFCH resource block.

[0021] Optionally, in any of the above aspects, another implementation of this aspect includes: when the programming instructions are executed by the processor, the UE is further caused to perform the following operations: (i) in response to determining that the LBT channel sensing fails, perform LBT channel sensing at another PSFCH occasion; (ii) after successfully performing LBT at an additional PSFCH occasion, transmit the PSFCH resource block.

[0022] These and other features will be more clearly understood from the following detailed description in conjunction with the accompanying drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] To more fully understand the present disclosure, reference is made to the following brief description taken in conjunction with the accompanying drawings and detailed description, in which like reference numerals represent like components.

[0024] Figure 1A is a schematic diagram of the network topology of a communication system according to an embodiment of the present disclosure.

[0025] Figure 1B is a schematic diagram showing an in-coverage (IC) scenario according to an embodiment of the present disclosure.

[0026] Figure 1C is a schematic diagram showing an out-of-coverage (OOC) scenario according to an embodiment of the present disclosure.

[0027] Figure 1D shows an exemplary user equipment (UE) according to an embodiment of the present disclosure.

[0028] Figure 1E shows an exemplary access node (or base station) according to an embodiment of the present disclosure.

[0029] Figure 2Schematic diagram of an exemplary resource pool in a time-frequency resource grid according to an embodiment.

[0030] Figure 3A Shows the frame structure of sidelink LTE mode 3 and mode 4 vehicle-to-vehicle (V2X) operations according to an embodiment.

[0031] Figure 3B Schematic diagram of resources for PSCCH, PSSCH, and PSFCH according to an embodiment of the present disclosure.

[0032] Figure 4 Schematic diagram showing an exemplary timing of sensing and resource selection for Rel-16 NR sidelink transmission according to an embodiment.

[0033] Figure 5 Shows the structure of a sidelink synchronization signal block (S-SSB) according to an embodiment of the present disclosure.

[0034] Figure 6 Shows a typical time slot structure including a physical sidelink feedback channel (PSFCH) timing according to an embodiment of the present disclosure.

[0035] Figure 7 Flowchart showing S-SSB transmission according to an embodiment of the present disclosure.

[0036] Figure 8 Flowchart showing an example of a PSFCH transmission process according to an embodiment of the present disclosure.

[0037] Figure 9 Shows an example of multi-channel channel occupancy time (COT) and COT sharing according to an embodiment of the present disclosure.

[0038] Figure 10 Shows an example of the frame structure of sidelink New Radio (SL NR) mode 2 according to an embodiment of the present disclosure.

[0039] Figure 11 Shows an example of the frame structure of sidelink New Radio (SL NR) mode 2 configured with PSFCH according to an embodiment of the present disclosure.

[0040] Figure 12 Shows the period of PSFCH according to an embodiment of the present disclosure.

[0041] Figure 13 Illustrates the coexistence of PSFCH according to an embodiment of the present disclosure.

[0042] Figure 14 Is a flowchart describing an example of the coexistence of NR SL UEs in which data is transmitted according to an embodiment of the present disclosure.

[0043] Figure 15 Is a flowchart describing an example of the coexistence of NR SL UEs in which data is received according to an embodiment of the present disclosure.

[0044] Figure 16 Is a flowchart showing an example of the PFSCH period according to an embodiment of the present disclosure.

[0045] Figure 17 Is a flowchart showing an example of the transmission process of a sidelink synchronization signal block (S-SSB) according to an embodiment of the present disclosure. Detailed implementation

[0046] The present disclosure describes new technologies and signaling for implementing sidelink positioning. Sidelink communication can be in-coverage communication or out-of-coverage communication. When operating in-coverage (IC), there is a central node (eNB, gNB) that can be used to manage sidelinks in mode 1 of scheme 1. In mode 2 of scheme 2, the system operates in a fully distributed manner, and each user equipment (UE) selects resources on its own. In the present disclosure, it is also possible to help or assist some UEs in selecting system resources. It should be noted that in mode 2, the UE can be in-coverage (IC) or out-of-coverage (OOC).

[0047] Figure 1AIt is a schematic diagram of the network topology of the communication system 100 according to an embodiment of the present disclosure. In the coverage area 101, the communication system 100 includes an access node 110 that serves user equipment (UE) such as UE 120. The access node 110 is coupled to a fronthaul network 115 that provides a connection to services and the Internet. In the first operating mode (IC operation), communication to and from the UE passes through the access node 110. In the second operating mode (OOC operation), communication to and from the UE does not pass through the access node 110. However, when specific conditions are met, the access node 110 typically allocates resources for the UE to use for communication. In the second operating mode, communication between UEs is performed through a sidelink 125 that includes a one-way communication link. Communication in the second operating mode can be referred to as "sidelink communication". Communication between the UE and the access node pair is performed through a one-way communication link, where the communication link from the UE 120 to the access node 110 is referred to as the "uplink 130", and the communication link from the access node 110 to the UE 120 is referred to as the "downlink 135".

[0048] The access node 110 can generally also be referred to as Node B, evolved Node B (eNB), next generation (NG) Node B (gNB), master eNB (MeNB), secondary eNB (SeNB), master gNB (MgNB), secondary gNB (SgNB), network controller, control node, base station, access point, transmission point (TP), transmission-reception point (TRP), cell, carrier, macro cell, femto cell, pico cell, etc. The UE can generally also be referred to as mobile station, mobile device, terminal, user, subscriber, station, etc. The access node can provide wireless access according to one or more wireless communication protocols, for example, the Third Generation Partnership Project (3GPP) long term evolution (LTE), LTE advanced (LTE-A), 5G, 5G LTE, 5G NR, sixth generation (6G), High Speed Packet Access (HSPA), IEEE 802.11 series standards such as 802.11a / b / g / n / ac / ad / ax / ay / be, etc. For simplicity, only one access node 110 and two UEs 120 are shown, but it can be understood that the communication system can employ multiple access nodes capable of communicating with multiple UEs.

[0049] The sidelink communication can be in-coverage communication or out-of-coverage communication. For in-coverage (IC) operation, there can be a central node (e.g., access node, eNB, gNB, etc.) for managing the sidelink. For OOC operation, the system operation is fully distributed and the UEs select resources by themselves.

[0050] Figure 1B FIG. 7 is a schematic diagram showing an IC scenario 100 according to an embodiment of the present disclosure. In the IC scenario 100, the access node 110 is used to manage the sidelink communication 145 between UEs 120A and 120B in the coverage area 101 of the access node 110. The UEs 120A and 120B can be regarded as "mode 1" UEs. In the first operating mode (IC operation), the communication 140 to and from the UEs passes through the access node 110.

[0051] Figure 1C It is a schematic diagram showing the OOC scenario 199 according to an embodiment of the present disclosure. In the OOC scenario 199, the UEs 120A and 120B can perform sidelink communication 145 with each other without the management of a central node and can select resources for the sidelink communication 145 by themselves. The UEs 120A and 120B can be regarded as "mode 2" UEs. The UEs 120A and 120B can operate in mode 2 when they are within the coverage area. In the embodiments of the present disclosure, it can help or assist some UEs in selecting resources for sidelink communication.

[0052] Figure 1D and Figure 1E shows an exemplary device that can implement the methods and guidelines according to the present disclosure. Specifically, Figure 1D shows an exemplary UE 120 according to an embodiment of the present disclosure. Figure 1E shows an exemplary access node (or base station) 110 according to an embodiment of the present disclosure. These components can be used in the communication system 100 or any other suitable system.

[0053] As Figure 1D shown, the UE 120 includes at least one processing unit 150. The processing unit 150 implements various processing operations of the UE 120. For example, the processing unit 150 can perform signal encoding, data processing, power control, input / output processing, or any other function that enables the UE 120 to operate in the communication system 100. The processing unit 150 also supports the methods and guidelines described in more detail herein. Each processing unit 150 includes any suitable processing or computing device for performing one or more operations. For example, each processing unit 150 can include a microprocessor, a microcontroller, a digital signal processor, a field programmable gate array, or an application specific integrated circuit.

[0054] UE 120 also includes at least one transceiver 152. The transceiver 152 is used to modulate data or other content for transmission via at least one antenna 154. The transceiver 152 is also used to demodulate data or other content received by at least one antenna 154. Each transceiver 152 includes any suitable structure for generating signals for wireless or wired transmission, or for processing signals received wirelessly or wiredly. Each antenna 154 includes any suitable structure for transmitting or receiving wireless or wired signals. One or more transceivers 152 may be used for UE 120, and one or more antennas 154 may be used for UE 120. Although the transceiver 152 is shown as a single functional unit, it may also be implemented using at least one transmitter and at least one separate receiver. In some embodiments, the transceiver 152 in UE 120 may include a dual transceiver architecture, where a first LTE transceiver module communicates with other devices (e.g., access nodes, UEs, etc.) via the LTE protocol, and a second new radio (NR) transceiver module communicates with other devices via the fifth generation (5G) NR protocol, etc.

[0055] UE 120 also includes one or more input / output (I / O) devices 156 or interfaces (such as a wired interface connected to the Internet). The I / O devices 156 facilitate interaction with users or other devices in the network (network communication). Each I / O device 156 includes any suitable structure for providing information to the user or receiving information from the user, such as a speaker, microphone, keypad, keyboard, display, or touch screen, including network interface communication.

[0056] In addition, the UE 120 includes at least one memory 158. The memory 158 stores instructions and data used, generated, or collected by the UE 120. The memory 158 includes a non-transitory computer-readable storage medium that can store a computer program product for use by the user equipment. The computer program product stores programming instructions that, when executed by the processor 150, cause the UE to perform any of the operations or methods described in this disclosure. For example, the memory 158 can store software or firmware instructions executed by one or more processing units 150, as well as data for reducing or eliminating interference in incoming signals. Each memory 158 includes any suitable one or more volatile or non-volatile storage and retrieval devices. Any suitable memory can be used, for example, random access memory (RAM), read only memory (ROM), hard disk, optical disk, subscriber identity module (SIM) card, memory stick, secure digital (SD) memory card, etc.

[0057] As Figure 1E shown, the access node 110 includes at least one processing unit 160, at least one transceiver 162 (including the functions of a transmitter and a receiver), one or more antennas 164, at least one memory 166, and one or more input / output (I / O) devices (or interfaces) 168. A scheduler understood by those skilled in the art is coupled to the processing unit 160. The scheduler can be included within the access node 110 or operate separately from the access node 110. The processing unit 160 implements various processing operations of the access node 110, such as signal encoding, data processing, power control, input / output processing, or any other function. The processing unit 160 can also support the methods and guidance described in more detail herein. Each processing unit 160 includes any suitable processing or computing device for performing one or more operations. For example, each processing unit 160 can include a microprocessor, a microcontroller, a digital signal processor, a field programmable gate array, or an application specific integrated circuit.

[0058] Each transceiver 162 includes any suitable structure for generating signals for wireless or wired transmission to one or more UEs or other devices. Each transceiver 162 also includes any suitable structure for processing signals received from one or more UEs or other devices wirelessly or wiredly. Although the transmitter and receiver are shown in combination as transceiver 162, the two can be separate components. Each antenna 164 includes any suitable structure for transmitting or receiving wireless or wired signals. Although the common antenna 164 shown here is coupled to transceiver 162, if configured as a separate component, one or more antennas 164 can be coupled to one or more transceivers 162 such that the separate antennas 164 are coupled to the transmitter and receiver. In some embodiments, the transceiver 162 in access node 110 may include a dual transceiver architecture, where a first LTE transceiver module communicates with other devices (e.g., UEs) via the LTE protocol, and a second new radio (NR) transceiver module communicates with other devices via the fifth generation (5G) NR protocol, etc.

[0059] Each memory 166 includes any suitable one or more volatile or non-volatile storage and retrieval devices. Each input / output device 168 facilitates interaction (network communication) with users or other devices in the network. The memory 166 includes a non-transitory computer-readable storage medium that can store a computer program product for use by a user device. The computer program product stores programming instructions that, when executed by the processor 160, cause the access node 110 to perform any of the operations or methods described in this disclosure. Each input / output device 168 includes any suitable structure for providing information to or receiving information from a user, including network interface communication.

[0060] To enable sidelink communication, resource pools are provided for the LTE sidelink, and these resource pools can be reused for the NR sidelink. A resource pool is a set of resources that can be used for sidelink communication. Resources in the resource pool can be configured for different channels and signals, such as control channels, shared channels, feedback channels, broadcast channels (e.g., master information blocks), synchronization signals, reference signals, etc. 3GPP TS 38.331, "NR; Radio Resource Control (RRC); Protocol specification" (V16.4.1, March 30, 2021), which is incorporated herein by reference, defines the rules for sharing resources in the resource pool and using the resources for a specific configuration of the resource pool. A UE performing sidelink transmission can select resources from the resource pool for sidelink communication and transmit signals in those resources on the sidelink.

[0061] Figure 2 It is a schematic diagram of resource pool 200 in the time-frequency resource grid according to an embodiment. The resource pool 200 for sidelink communication can be configured in units of time slots 210 in the time domain (horizontal axis) and physical resource blocks (PRBs) 220 or sub-channels (SUB-Cs) 220 in the frequency domain (vertical axis). A sub-channel 220 can include one or more PRBs 220. Figure 2 It shows a resource pool 200 including a plurality of resources 231, 232, 241, 242 (shaded rectangles) in different time slots 210 and PRBs / sub-channels 220.

[0062] According to 3GPP TS 38.211, "NR; Physical channels and modulation" (V16.5.0, March 30, 2031), the entire content of which is incorporated herein by reference, for NR mobile broadband (MBB), each physical resource block (PRB) in the grid is defined as a time slot that includes 14 consecutive orthogonal frequency division multiplexing (OFDM) symbols in the time domain and 12 consecutive subcarriers in the frequency domain (i.e., each resource block includes 12×14 resource elements (REs)). When used as a frequency domain unit, a PRB can be 12 consecutive subcarriers. When using a normal cyclic prefix, there are 14 symbols in a time slot, and when using an extended cyclic prefix, there are 12 symbols in a time slot. The duration of a symbol is inversely proportional to the subcarrier spacing (SCS). For {15, 30, 60, 120} kHz SCS, the durations of the time slots are {1, 0.5, 0.25, 0.125} milliseconds, respectively.

[0063] PRBs can be allocated for transmitting channels and / or signals (e.g., control channels, shared channels, feedback channels, reference signals, or combinations thereof). In addition, some REs of the PRBs can be reserved. A similar time-frequency resource structure can also be used on the sidelink. Communication resources (e.g., for sidelink communication) can be PRBs, sets of PRBs, codes (if code division multiple access (CDMA) is used, similar to the codes for the physical uplink control channel (PUCCH)), physical sequences, sets of REs, or combinations thereof.

[0064] As used herein, when a UE participating in sidelink communication is used to send a signal on the sidelink to another UE, the UE may be referred to as a "source UE", "transmitting UE", or "Tx UE". When a UE participating in sidelink communication is used to receive a signal on the sidelink from another UE, the UE may be referred to as a "destination UE", "receiving UE", "Rx UE", or "receiving party UE". Two UEs communicating with each other on the sidelink may also be referred to as a "UE pair" in sidelink communication.

[0065] The physical sidelink shared channel (PSSCH) carries sidelink data between UEs. Sidelink transmission may include a one-to-many scenario, which means the data will be received by multiple UEs belonging to a group. The PSSCH is a dedicated wireless communication channel for direct device-to-device (D2D) communication in cellular networks such as 4G LTE and 5G. The PSSCH facilitates proximity services by allowing nearby devices (e.g., UEs) to communicate without routing through an access node or base station. The PSSCH has dedicated resource allocation, control signaling, and security measures to support low-latency and efficient D2D communication, which makes it crucial in applications such as public safety, vehicle-to-vehicle (V2V) communication, and cooperative awareness. The time and frequency resources of the PSSCH may be referred to as "resource allocation" or "allocation", and may be indicated in a time resource allocation field and / or a frequency resource allocation field (i.e., resource location).

[0066] The physical sidelink control channel (PSCCH) carries sidelink control information (SCI). SCI format 1 consists of PSSCH transmission information and is transmitted in two consecutive resource blocks (RBs). The source UE uses the SCI to schedule data transmission on the PSSCH or reserve resources for data transmission on the PSSCH. The SCI may convey the time and frequency resources of the PSSCH and / or parameters of the hybrid automatic repeat request (HARQ) process, e.g., redundancy version, process id (or ID), new data indicator, and resources of the physical sidelink feedback channel (PSFCH).

[0067] The physical sidelink feedback channel (PSFCH) carries hybrid ARQ feedback for sidelink transmissions received on the PSSCH. The basic structure of the PSFCH is the same as that of PUCCH format 0. The PSFCH can carry an indication (e.g., HARQ acknowledgement (HARQ-ACK) or negative acknowledgement (HARQ-NACK)) indicating whether the destination UE has correctly decoded the payload carried on the PSSCH. The SCI can also carry a bit field indicating or identifying the source UE. In addition, the SCI can carry a bit field indicating or identifying the destination UE. The SCI can also include other fields to carry information, such as the modulation and coding scheme for encoding the payload and modulating the encoded payload bits, the demodulation reference signal (DMRS) pattern, the antenna port, the priority of the payload (transmission), etc. The sensing UE performs sensing on the sidelink (i.e., receives the PSCCH sent by another UE), decodes the SCI carried in the PSCCH to obtain information about the resources reserved by another UE, and determines the resources for the sidelink transmission of the sensing UE.

[0068] When operating in mode 1, the time-frequency resources used for the UE-to-UE link are allocated by the access node (or base station). When operating in mode 2, the common time-frequency resources are autonomously shared among the UEs without the intervention of the access node. The 3rd Generation Partnership Project (3GPP) has specified the vehicle-to-everything (V2X) communication standard based on the LTE radio interface. This defines the PC5 interface for V2X sidelink or direct communication and introduces two different modes (i.e., mode 3 and mode 4) for managing the radio resources of the PC5 interface.

[0069] Mode 3 is a centralized mode in which the cellular network selects the radio resources for the vehicle to use for direct or sidelink V2V communication (i.e., without using the Uu interface). Mode 3 can improve the quality of service (QoS) and scalability because the cellular network has a full understanding of the network state and the resource requirements from different vehicles. Therefore, mode 3 can improve resource selection and reduce interference between vehicles. Different from mode 4, 3GPP has not specified a specific scheduling scheme for mode 3.

[0070] Mode 4 is a distributed mode in which a UE (e.g., a vehicle) can autonomously select its radio resources using a sensing-based semi-persistent scheduling (SPS) scheme. Mode 4 can operate without cellular coverage, but its communication performance may be affected by non-optimal radio resource selection based on local sensing only.

[0071] LTE : Figure 3A illustrates a frame structure for sidelink LTE mode 3 and mode 4 vehicle-to-vehicle (V2V) operation according to an embodiment. Two subchannels are shown: subchannel 0 and subchannel 1. Each subchannel contains 6 RBs. Some examples of subchannel sizes are as follows: 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 25, 30, 48, 50, 72, 75, 96, and 100 RBs. In Figure 3A a 14-symbol subframe has symbols for automatic gain control (AGC), PSSCH, DMRS PSSCH, PSCCH, DMRS PSCCH, and protection, as Figure 3A identified by letters A through F in the legend of

[0072] Data (PSSCH) and control (PSCCH) information are multiplexed in the frequency domain. In LTE, the starting resource location of the PSCCH is related to the subchannel index. Through configuration, the Tx pool for V2V is divided into "m" subchannels. The transmitting vehicle selects one of the m subchannels, or is instructed by the eNB to use a specific subchannel in a DCI message. The PSSCH is placed after the PSCCH such that the PSCCH occupies a lower frequency position than the PSSCH. The PSCCH for V2V occupies 2 PRBs.

[0073] LTE devices support RSSI on measurement symbols. Generally, protection symbols and AGC symbols are not measured. The receiving LTE UE can check the received SCI to determine the period and priority of the received transmission. The period, priority, and measurement can be used when the LTE device selects resources for its transmission.

[0074] Figure 3B is a schematic diagram 300 of resources for PSCCH, PSSCH, and PSFCH according to an embodiment of the present disclosure. Figure 3B illustrates the resources in slot n and slot n + 1. Slot n includes a resource region 310 for PSCCH, a resource for PSSCH (or PSSCH m) resource region 312, reservation region 314, and resource region 316 for PSFCH. Time slot n+1 includes resource region 320 for PSCCH, resource region 322 for PSSCH (or PSSCH k ) and resource region 322, reservation region 324, and resource region 326 for PSFCH.

[0075] In New Radio (NR), SCI has two phases: the first phase and the second phase. The first-phase SCI can indicate the resources for the second-phase SCI. The first-phase SCI can be transmitted in the PSCCH. The second-phase SCI can be transmitted in the PSSCH. SCI can have the following formats: SCI format 1-A, SCI format 2-A, and SCI format 2-B.

[0076] In Rel-16 NR V2X sidelink communication, mode 2 UEs can send and receive information without network management. The UE allocates resources for itself from the resource pool for sidelink transmission. The resource allocation depends on Figure 4 the sensing and reservation process shown.

[0077] Figure 4 FIG. 400 is a schematic diagram showing an exemplary timing of sensing and resource selection for Rel-16 NR sidelink transmission according to an embodiment. The timing of sensing and resource selection is generally referred to as "full sensing". Schematic diagram 400 includes a sensing window 410 and a resource selection window 420. During the sensing window 410, the UE can monitor the availability of sidelink resources; during the resource selection window 420, the UE can select available sidelink resources.

[0078] During the sensing process, the UE that wants to perform sidelink transmission (also referred to as the monitoring UE or sensing UE, or transmitting UE because the UE wants to send SL traffic) detects the SCI transmitted in each time slot in the sensing window 410 and measures the received signal receive power (RSRP) of the resources indicated in the SCI. The monitoring UE can also receive data transmission during the sensing window 410. Therefore, the monitoring UE is also a receiving UE. For resource reservation for sidelink transmission of periodic traffic, if the UE occupies resources on time slot s m (e.g., UE k occupies resources on time slot s m ), the UE will also occupy one or more resources on time slot s m + q*RRI k where q is an integer and RRI kTo sense the resource reservation interval of UE k detected by the sensing UE. The monitoring UE can detect the SCI of UE k and the resources occupied by UE k. For example, the monitoring UE detecting the SCI may include steps of receiving and decoding the PSCCH and processing the SCI within the PSCCH.

[0079] For non-periodic or dynamic transmissions, the transmitting UE (e.g., UE k) in sidelink communication may reserve multiple resources and indicate the next resource in its SCI. Thus, based on the sensing result of the monitoring UE (e.g., based on the detection of the SCI of UE k), the monitoring UE can determine which resources may be occupied in the future and can avoid selecting those resources for its own sidelink transmissions. The monitoring UE can determine whether a resource is occupied based on the RSRP measured on the resource during the sensing period (sensing window 410). For example, if the RSRP measured on the occupied resource during the sensing period is higher than the RSRP threshold, the monitoring UE can avoid the occupied resource, such as the resource exclusion process described in TS 38.214.

[0080] When resource selection is triggered on slot "n" 430, based on the sensing result in the sensing window 410 (i.e., at slots [n - T 0 , n - T proc,0 ), the monitoring UE or the transmitting UE can select sidelink resources in the resource pool during the resource selection window 420 in the resource pool (i.e., at slots [n + T 1 , n + T 2 ). The variables are defined as follows: (i) T 0 is the number of slots, and its value is determined by the resource pool configuration; (ii) T proc,0 is the time required for the UE to complete the sensing process; (iii) T 1 is the processing time required for candidate resource identification and resource selection, T 1 ≤ T proc,1 ; (iv) T 2 is the last slot in the resource pool for resource selection, left for the UE to execute, but within the range of [T 2min, PDB], where T 2min is the minimum value of T 2 , and PDB represents the remaining time for the UE to transmit the data packet, i.e., the "packet delay budget"; (v) T proc,1 is the maximum time required for the UE to identify candidate resources and select new sidelink resources.

[0081] To select resources, a transmitting UE (which senses resources for sidelink transmission) can identify candidate resources (or available resources) by excluding occupied resources on which RSRP has been measured at a configured RSRP threshold. The transmitting UE can compare the ratio of available resources among all resources in the selection window 420 (also referred to as the "available resource ratio"). If the available resource ratio is greater than a threshold X%, the transmitting UE randomly selects a resource among the candidate resources. If the available resource ratio is not greater than X%, the transmitting UE can increase the RSRP threshold by 3 dB and check the available resource ratio until the available resource ratio is equal to or greater than X%. The value of "X" can be selected from the list sl-TxPercentageList, whose value is determined by data priority. According to the provisions in TS 38.214, for a given prio TX the internal parameter X is defined as sl-TxPercentageList(prio TX ) converted from percentage to ratio.

[0082] As described above, NR sidelink control information (SCI) can be transmitted in two phases, namely the first-phase SCI format 1-A and the second-phase SCI formats 2-A, B, or C. The first phase indicates the resources for the second-phase SCI. According to TS 38.212, SCI format 1-A is used for the second-phase SCI on the PSSCH and the scheduling of the PSSCH.

[0083] SCI Format 1-A :

[0084] The following information is transmitted through SCI format 1-A:

[0085] (i) Priority: three (3) bits, as defined in clause 5.4.3.3 of TS23.287;

[0086] (ii) Frequency resource allocation:

[0087] (a) bits, when the value of the higher-layer parameter sl-MaxNumPerReserve is configured to 2;

[0088] Otherwise,

[0089] (b) bits, when the value of the higher-layer parameter sl-MaxNumPerReserve is configured to 3, as defined in clause 8.1.2.2 of TS 38.214;

[0090] (iii) Time resource allocation:

[0091] (a) Five (5) bits, when the value of the higher layer parameter sl-MaxNumPerReserve is configured to 2; otherwise,

[0092] (b) Nine (9) bits, when the value of the higher layer parameter sl-MaxNumPerReserve is configured to 3, as defined in clause 8.1.2.1 of TS 38.214.

[0093] (iv) Resource reservation period:

[0094] (a) Bits, as defined in clause 8.1.4 of TS 38.214, where, if the higher layer parameter sl-MultiReserveResource is configured, N rsv_period is the number of entries in the higher layer parameter sl-ResourceReservePeriodList;

[0095] (b) Otherwise zero (0) bits.

[0096] (v) DMRS mode:

[0097] (a) Bits, as defined in clause 8.4.1.1.2 of TS 38.211, where, N pattern is the number of DMRS modes configured by the higher layer parameter sl-PSSCH-DMRS-TimePatternList;

[0098] (b) Zero (0) bits, if sl-PSSCH-DMRS-TimePatternList is not configured.

[0099] (vi) Phase 2 SCI format: Two (2) bits, as defined in Table 8.3.1.1-1 of 3GPP Technical Specification TS 37.213 "Physical Specification Procedures for Shared Spectrum Channel Access" (Release 18), which is incorporated herein by reference as if fully set forth herein.

[0100] (vii) Beta_offset indicator: Two (2) bits, provided by the higher layer parameter sl BetaOffsets2ndSCI and Table 8.3.1.1-2 of TS37.213.

[0101] (viii) Number of DMRS ports: One (1) bit, as defined in Table 8.3.1.1-3 of TS 37.213.

[0102] (ix) Modulation and Coding Scheme: Five (5) bits, as defined in clause 8.1.3 of TS 38.214.

[0103] (x) Additional MCS Table Indicator: As defined in clause 8.1.3.1 of TS 38.214.

[0104] (a) One (1) bit if one MCS table is configured by the higher layer parameter sl-Additional-MCS-Table;

[0105] (b) Two (2) bits if two MCS tables are configured by the higher layer parameter sl-Additional-MCS-Table;

[0106] (c) Otherwise, zero (0) bits.

[0107] (xi) PSFCH Overhead Indicator: 1 bit if the higher layer parameter sl-PSFCH-Period = 2 or 4, as defined in clause 8.1.3.2 of TS 38.214; otherwise 0 bits.

[0108] (xii) Reserved: A number of bits determined by the higher layer parameter sl-NumReservedBits, which is set to zero (0).

[0109] SCI Format 2-A :

[0110] SCI format 2-A in TS 38.212 is used to decode the PSSCH using HARQ operations when the HARQ-ACK information includes ACK or NACK, or when no HARQ-ACK information is fed back. The following information is transmitted through SCI format 2-A:

[0111] (i) HARQ process number: Bits, as defined in clause 16.4 of TS 38.213.

[0112] (ii) New Data Indicator: One (1) bit, as defined in clause 16.4 of TS 38.213;

[0113] (iii) Redundancy Version: Two (2) bits, as defined in clause 16.4 of TS 38.214;

[0114] (iv) Source ID: Eight (8) bits, as defined in clause 8.1 of TS 38.214;

[0115] (v) Destination ID: Sixteen (16) bits, as defined in clause 8.1 of TS 38.214;

[0116] (vi) HARQ feedback enable / disable indicator: one (1) bit, as defined in clause 16.3 of TS 38.213;

[0117] (vii) Broadcast type indicator: two (2) bits, as defined in table 8.4.1.1-1 of TS 37.213, as follows;

[0118] (viii) CSI request: one (1) bit, as defined in clause 8.2.1 of TS 38.214.

[0119] Table 8.4.1.1-1: Broadcast type indicator

[0120] Values of Broadcast Type Indicator Broadcast Type 00 Broadcast 01 Multicast 10 Unicast 11 Reserved

[0121] According to TS 38.212, SCI format 2-B is used to decode the PSSCH using HARQ operations when the HARQ-ACK information only includes NACK, or when no HARQ-ACK information is fed back. The following information is transmitted through SCI format 2-B:

[0122] (i) HARQ process number: Bits, as defined in clause 16.4 of TS 38.213.

[0123] (ii) New data indicator: one (1) bit, as defined in clause 16.4 of TS 38.213;

[0124] (iii) Redundancy version: two (2) bits, as defined in clause 16.4 of TS 38.214;

[0125] (iv) Source ID: eight (8) bits, as defined in clause 8.1 of TS 38.214;

[0126] (v) Destination ID: sixteen (16) bits, as defined in clause 8.1 of TS 38.214;

[0127] (vi) HARQ feedback enable / disable indicator: one (1) bit, as defined in clause 16.3 of TS 38.213;

[0128] (vii) Area ID: twelve (12) bits, as defined in clause 5.8.1.1 of TS 38.331;

[0129] (viii) Communication range requirement: four (4) bits, as defined in TS 38.331;

[0130] Higher layer message (from TS 38.331):

[0131] SL-PSCCH-Config-r16 ::= Sequence {

[0132] sl-TimeResourcePSCCH-r16 Enumeration {n2, n3}

[0133] Optional, -- Requires M

[0134] sl-FreqResourcePSCCH-r16 Enumeration {n10, n12, n15, n20, n25}

[0135] Optional, -- Requires M

[0136] sl-DMRS-ScrambleID-r16 Integer (0..65535)

[0137] Optional, -- Requires M

[0138] sl-NumReservedBits-r16 Integer (2..4)

[0139] Optional, -- Requires M ...

[0141] }}

[0142] Table 1 in TS 37.213 defines the SL-OSCCH field description:

[0143] Table 1

[0144]

[0145] According to TS 38.212, SCI format 2-C is used to decode the PSSCH and provide or request UE-to-UE coordination information. The following information is transmitted through SCI format 2-C:

[0146] (i) HARQ process number: Four (4) bits;

[0147] (ii) New data indicator: One (1) bit;

[0148] (iii) Redundancy version: Two (2) bits, as defined in Table 7.3.1.1.1-2 of TS 37.213;

[0149] (iv) Source ID: Eight (8) bits, as defined in Clause 8.1 of TS 38.214;

[0150] (v) Destination ID: 16 bits, as defined in Clause 8.1 of TS 38.214;

[0151] (vi) HARQ feedback enable / disable indicator: one (1) bit, as defined in clause 16.3 of TS 38.213;

[0152] (vii) CSI request: one (1) bit, as defined in clause 8.2.1 of TS 38.214 and clause 8.1 of TS 38.214;

[0153] (viii) Provide / request indicator: (1) bit, where a value of "0" indicates that SCI format 2-C is used to provide inter-UE coordination information, and a value of 1 indicates that SCI format 2-C is used to request inter-UE coordination information;

[0154] If the "provide / request indicator" field is set to zero (0), then all remaining fields are set as follows:

[0155] (i) Resource combination:

[0156] (a) Bits, as defined in clause 8.1.5A of TS 38.214, where

[0157] (1) If the higher layer parameter sl-MultiReserveResource is configured, then Y = ||log 2 N rsv_period | and N rsv_period

[0158] are the number of entries in the higher layer parameter sl-ResourceReservePeriodList;

[0159] (2) Otherwise Y = 0;

[0160] (3) is the number of sub-channels in the resource pool provided by the higher layer parameter sl-NumSubchannel;

[0161] (ii) First resource location: eight (8) bits, as defined in clause 8.1.5A of TS 38.214;

[0162] (iii) Reference time slot location: ) bits, as defined in clause 8.1.5A of TS 38.214, where μ is defined in Table 4.2-1 of clause 4.2 of TS 38.211;

[0163] (iv) Resource set type: one (1) bit, where a value of "0" indicates a preferred resource set and a value of "1" indicates a non-preferred resource set;

[0164] (v) Lowest sub-channel index: bits, as defined in clause 8.1.5A of TS 38.214;

[0165] If the "Provide / Request Indicator" field is set to "1", then all the remaining fields are set as follows:

[0166] (i) Priority: three (3) bits, as specified in clause 5.4.3.3 of TS23.287 and clause 5.22.1.3.1 of TS 38.321. The value "000" of the priority field corresponds to the priority value "1", the value "001" of the priority field corresponds to the priority value "2", and so on.

[0167] (ii) Number of sub-channels: bits, as defined in clause 8.1.4A of TS 38.214;

[0168] (iii) Resource reservation period: bits, as defined in clause 8.1.4A of TS 38.214, where, if the higher layer parameter sl-MultiReserveResource is configured, then N rsv_period is the number of entries in the higher layer parameter sl-ResourceReservePeriodList; otherwise zero (0) bits;

[0169] (iv) Resource selection window position: bits, as defined in clause 8.1.4A of TS 38.214, where μ is defined in Table 4.2-1 of clause 4.2 of TS 38.211;

[0170] (v) Resource set type: one (1) bit, if the higher layer parameter determineResourceSetTypeScheme1 is configured as "Request of UE-B", where the value "0" indicates a request to provide inter-UE coordination information for a preferred resource set, and the value "1" indicates a request to provide inter-UE coordination information for a non-preferred resource set; otherwise zero (0) bit.

[0171] (vi) Padding bits.

[0172] Sidelink Inter-UE Coordination (IUC) : In Rel-17, inter-UE coordination (IUC) for sidelink is specified to improve the reliability of mode 2 by overcoming certain problems that affect sidelink performance, such as hidden nodes, exposed nodes, and half-duplex. Two IUC schemes are defined: Scheme 1 and Scheme 2 as follows:

[0173] (A) Scheme 1: Signaling of inter-UE coordination information from UE-A to UE-B:

[0174] (1) Preferred resource set for the transmission of UE-B;

[0175] (2) Non-preferred resource set for the transmission of UE-B;

[0176] (B) Solution 2: Inter-UE coordination information signaling from UE-A to UE-B:

[0177] (1) There is an expected / potential resource conflict on the resources indicated by the SCI of UE-B;

[0178] In IUC solution 1, two IUC trigger scenarios are considered and specified. The first trigger scenario includes coordination triggered by an explicit request, where UE-B sends an explicit request to UE-A, and UE-A generates and sends coordination information (preferred resource set or non-preferred resource set) to UE-B according to the request. The second trigger scenario includes coordination triggered by conditions other than an explicit request, where a UE (e.g., UE-A) that meets certain conditions generates and sends coordination information to UE-B.

[0179] The conditions for the two IUC trigger scenarios are also specified. For inter-UE coordination (IUC) triggered by an explicit request, one of two conditions is configured at the resource pool level: Alternative 1: Implemented by UE-B; Alternative 2: The request is triggered only when UE-B has data to transmit to UE-A. Similarly, for IUC triggered by conditions, two conditions are also agreed upon, and one of the conditions is enabled by (pre-)configuration at the resource pool level: Alternative 1: Implemented by UE-A; Alternative 2: The coordination is triggered only when UE-A has data to transmit to UE-B together with the coordination information.

[0180] The generation criteria for coordination information, that is, the preferred resource set and the non-preferred resource set, are defined as follows.

[0181] (A) Preferred resource set:

[0182] (1) Condition 1-A-1: One or more resources other than one or more overlapping reserved resources of another UE with RSRP greater than the threshold;

[0183] (2) Condition 1-A-2: One or more resources other than time slots when UE-A (as the Rx of UE-B) does not expect to perform SL reception from UE-B.

[0184] (B) Non-preferred resource set:

[0185] (1) Condition 1-B-1: One or more reserved resources and RSRP measurements of the identified other UE.

[0186] a. Option 1: One or more reserved resources of one or more other UEs identified by UE-A, and the RSRP measurement of UE-A is greater than the (pre)-configured RSRP threshold;

[0187] b. Option 2: One or more reserved resources of other UEs identified by UE-A when UE-A is the destination of the transport block (TB) of one or more UEs, and the RSRP measurement of UE-A is less than the (pre)-configured RSRP

[0188] threshold.

[0189] (2) Condition 1-B-2: One or more resources (e.g., one or more time slots), where when UE-A is the expected recipient of UE-B, it is not expected to perform SL reception from UE-B.

[0190] To send explicit requests and coordination information, MAC-CE is used as the container. If configured, the second-phase SCI (SCI-2C) is also used for explicit requests or coordination information. For explicit-request-triggered coordination, the transmission of both explicit requests and coordination information only supports unicast. For condition-triggered coordination, the transmission of both types of coordination information supports unicast. The non-preferred resource set only supports broadcast and multicast. Coordination information and explicit requests can only be multiplexed and transmitted with data when the source / destination ID pair is the same.

[0191] Figure 5 The structure of a sidelink synchronization signal block (S-SSB) 500 according to an embodiment of the present disclosure is shown. The S-SSB is a synchronization time slot in the sidelink and is used for one UE to synchronize with another UE. As Figure 5 shown, the first orthogonal frequency-division multiplexing (OFDM) symbol 511 is used for the physical sidelink broadcast channel (PSBCH). However, like a conventional sidelink time slot, the first symbol is used for the establishment of automatic gain control (AGC). Next, there are two symbols 512 and 513 for the sidelink primary synchronization signal (S-PSS), and two symbols 514 and 515 for the sidelink secondary synchronization signal (S-SSS).

[0192] The next eight (8) symbols 516 to 523 out of the remaining nine (9) symbols are used for PSBCH transmission. The last symbol 524 is the guard period (GP), which is the same as that in a regular sidelink time slot. In the frequency domain, S-SSB 500 occupies eleven (11) physical resource blocks (PRBs), with a total of 132 subcarriers. When the synchronization signal size is 127, PSBCH 511 occupies all eleven (11) PRBs. Therefore, S-PSS 512, 513 and S-SSS 514, 515 occupy 127 subcarriers. The period of S-SSB 500 is 160 milliseconds. The frequency position of S-SSB 500 is pre-configured. For frequency range 1 (FR1), the S-SSB transmission count is set to "1", and for frequency range 2 (FR2), the S-SSB transmission count is configurable.

[0193] Sidelink Resource Allocation This can be achieved as follows.

[0194] Mode 1 Resource Allocation :

[0195] In the sidelink mode 1 of the New Radio Vehicle to Everything (NR V2X) in Rel-16, the gNB performs sidelink scheduling. That is, the next generation nodeB (gNB) allocates SL resources for sidelink (SL) communication and sends resource allocation to the UE via the NR-UE interface. Therefore, the sidelink mode 1 is applicable to UEs within the coverage of the gNB. The resources allocated through mode 1 can be on the same carrier as the cellular NR or on a dedicated sidelink carrier.

[0196] There are three types of Mode 1 resource allocation, namely (i) dynamic allocation; (ii) Type 1 configured grant (CG); and (iii) Type 2 configured grant. In dynamic allocation, the UE first sends a scheduling request (SR) for each transport block (TB) to the gNB via the physical uplink control channel (PUCCH). Then, the gNB sends SL resource allocation to the UE via the downlink control information (DCI) format 3_0 of the physical downlink control channel (PDCCH). In CG-based resource allocation, the UE first sends a message with expected SL traffic (e.g., period, TB maximum size, and QoS information) to the gNB. The gNB provides resource allocation (i.e., the gNB provides CG to the UE via radio resource control (RRC) signaling). In Type 1 CG, the UE can use the resource allocation immediately. In Type 2 CG, the UE can use the allocated resources only after the gNB activates the allocated resources via DCI.

[0197] Mode 2 Resource Allocation

[0198] In Rel-16 sidelink Mode 2, the UE can send and receive information without network management. The UE itself allocates resources from the resource pool for sidelink transmission. The resource allocation depends on Figure 7 the sensing and reservation process shown. In the sensing process, the monitoring UE detects the SCI transmitted in each time slot in the sensing window and measures the reference signal received power (RSRP) of the resources indicated in the SCI. The monitoring UE (which is also the receiving UE) can also receive the transmission of data. For periodic traffic, resource reservation for sidelink transmission, if the UE occupies the resources on time slot s k then the UE will also occupy the resources on time slot s k + q * RRI k where q is an integer and RRI k is the resource reservation interval of UE m detected by the sensing UE. Detecting the SCI includes the steps of receiving and decoding the PSCCH and processing the SCI within the PSCCH.

[0199] For non-periodic or dynamic transmissions, the transmitting UE reserves multiple resources and indicates the next resource in the SCI. Thus, based on the sensing results, the monitoring UE can determine which resources may be occupied in the future and, if the RSRP measured on the occupied resources during the sensing period is greater than the RSRP threshold during the resource exclusion process, can avoid these resources for the monitoring UE's transmissions, as described in TS 38.214.

[0200] NR-U Unauthorized Channel Access :

[0201] Unlicensed spectrum, also known as "unauthorized spectrum" or "shared spectrum", has attracted the interest of cellular operators in recent years. LTE-Licensed Assisted Access (LAA) was specified in 3GPP LTE Release 13 and Release 14. Recently, in New Radio Unlicensed (NR-U), operations in unlicensed spectrum (shared spectrum) were specified in Release 16 of TS 38.213. 3GPP and IEEE technologies operating in unlicensed spectrum use Listen-Before-Talk (LBT) channel access. In some regions, such as the EU and Japan, LBT rules are enforced by spectrum regulators to reduce the interference risk and provide a fair coexistence mechanism. The LBT mechanism requires the transmitter to check if the channel has other occupants before transmitting and, if the channel is occupied, to postpone the transmission.

[0202] Specifically, the Listen-Before-Talk (LBT) rules for the EU specified in ETSI EN 301.893 for the 5 GHz band use Clear Channel Assessment (CCA) to determine if the channel is available for transmission. CCA checks if the received energy is higher than a threshold. If the detected energy exceeds the CCA threshold, the channel is considered to be in use (busy). Otherwise, the channel is considered idle.

[0203] "Channel occupancy" is the key information for the efficient operation of a wireless system. Channel occupancy can be defined as the time occupancy rate of a wireless network. In other words, "channel occupancy" refers to one or more transmissions on one or more channels by an eNB, gNB, and one or more UEs after performing the corresponding channel access procedures. "Channel occupancy time" (COT) refers to the total time of one or more transmissions on a channel by an eNB, gNB, UE, and any eNB / gNB / one or more UEs sharing the channel occupancy after the eNB / gNB / UE performs the corresponding channel access procedures. When determining the channel occupancy time, if the transmission gap is less than or equal to 25 microseconds, the gap duration is included in the channel occupancy time. The transmissions between an eNB / gNB and the corresponding one or more UEs can share the channel occupancy time. If the channel is idle, the transmitter can transmit on at least (for example) 80% of the total channel bandwidth within the COT duration.

[0204] ETSI EN 301.893 also specifies the maximum COT duration for a transmission burst. The maximum COT (MCOT) duration adopted in 3GPP NR-U Rel 16 of TS 37.213 is a function of the channel access priority class (CAPC). As specified in TS 37.213, when determining the COT, if the transmission gap is less than or equal to 25 microseconds, the gap duration is included in the channel occupancy time. A transmission burst is defined as a set of transmissions with a gap not exceeding 16 microseconds. If the gap is greater than 16 microseconds, the transmissions are considered to be independent.

[0205] In TS 37.213, the 3rd Generation Partnership Project (3 rd Generation Partnership Project, 3GPP) defines several types of channel access for the downlink (DL) and uplink (UL), including:

[0206] I. Type 1 UL channel access procedure

[0207] II. Type 2 UL channel access procedure

[0208] III. Type 2A UL channel access procedure

[0209] IV. Type 2B UL channel access procedure

[0210] V. Type 2C UL channel access procedure

[0211] These channel access procedures will be introduced below.

[0212] 1. Type 1 UL Channel Access Procedure Describes the channel access process of the UE, where the duration of the sensing time slots that are sensed to be idle before UL transmission is random. This entry applies to the following transmissions: (i) one or more PUSCH / SRS transmissions scheduled or configured by an access node (i.e., eNB / gNB); (ii) one or more PUCCH transmissions scheduled or configured by the gNB; or (iii) one or more transmissions related to the random access process.

[0213] After the channel is first sensed to be idle within the time slot duration of delay duration T d and the counter N in step 4 is zero, the UE can send a transmission through a type 1 channel access process. The counter N is adjusted by sensing one or more additional time slot durations of the channel according to the steps described below.

[0214] Step 1: Set N = N init , where N init is a random number uniformly distributed between 0 and CW p , go to step 4;

[0215] Step 2: If N > 0 and the UE chooses to decrement the counter, set N = N - 1;

[0216] Step 3: Sense the channel within the additional time slot duration. If the additional time slot duration is idle, go to step 4. Otherwise, go to step 5;

[0217] Step 4: If N = 0, stop. Otherwise, go to step 2;

[0218] Step 5: Sense the channel until a busy time slot is detected within the additional delay duration T d or all time slots within the additional delay duration T d are sensed to be idle;

[0219] Step 6: If the channel is sensed to be idle within all time slot durations of the additional delay duration T d , go to step 4. Otherwise, go to step 5.

[0220] If the UE has not sent a UL transmission on the channel where one or more UL transmissions are being performed after step 4 in the above process, the UE can send a transmission on this channel provided that when the UE is ready to send this transmission, the channel is sensed to be idle for at least the sensing time slot duration T sl and the delay duration T dThe channel has been sensed to be idle during all time slot durations. If when the UE senses the channel for the first time after being ready for transmission, the channel has not been sensed to be idle within the sensing time slot duration T sl or if the channel has not been sensed to be idle within any sensing time slot duration of the delay duration T d immediately preceding the expected transmission, then the UE proceeds to step 1 after sensing that the channel is idle within the time slot duration of the delay duration T d .

[0221] The delay duration T d includes the duration T p of the following m f consecutive time slot durations, where each time slot duration is T sl = 9 microseconds, and T f includes the idle time slot duration T f starting at T sl . The contention window is given by CW min,p ≤ CW p ≤ CW max,p . The contention window adjustment is described in clause 4.2.2 of TS 37.213. The values CW min,p and CW max,p are selected before step 1 of the above process. The values m p , CW min,p and CW max,p are based on the channel access priority level p indicated to the UE, as shown in table 4.2.1-1 of TS 37.213.

[0222] II. Type 2 UL Channel Access Procedure Describes the UE's channel access procedure, where the duration spanned by the sensing time slots sensed to be idle before UL transmission is deterministic. If the eNB instructs the UE to perform a type 2 UL channel access procedure, the UE follows the procedure described in the following item ("type 2A UL channel access procedure").

[0223] III. Type 2A UL Channel Access Procedure : If the UE is instructed to perform a type 2A UL channel access procedure, the UE performs UL transmission through the type 2A UL channel access procedure. The UE can send this transmission immediately after sensing that the channel is idle for at least one sensing interval T short_ul = 25 microseconds. This interval T short_ul includes the duration T f = 16 microseconds, followed by a sensing time slot, and T f includes the sensing time slot starting at T f . If T short_ulBoth of the two sensing time slots should be in the idle state, then the channel is in the idle state within T short_ul inside.

[0224] IV. Type 2B UL Channel Access Procedure : If the UE is instructed to perform a Type 2B UL channel access procedure, the UE performs UL transmission through the Type 2B UL channel access procedure. The UE can send this transmission immediately after sensing that the channel is to be in the idle state within a duration T f = 16 microseconds. The duration T f includes the sensing time slots that occur within the last 9 microseconds of T f . If it is sensed that the channel is to be in the idle state for a total of at least 5 us, where at least 4 us of the sensing occurs within the sensing time slots, the channel is considered to be in the idle state within the duration T f inside.

[0225] V. Type 2C UL Channel Access Procedure : If the UE is instructed to perform a Type 2C UL channel access procedure for UL transmission, the UE does not sense the channel before transmission. The duration of the corresponding UL transmission is at most 584 microseconds.

[0226] After first sensing that the channel is to be in the idle state within the sensing time slot duration of the delay duration Td and after the counter N reaches zero, the UE sends a channel access procedure through Type 1. The counter N is initialized with a random value greater than the minimum contention window (CW min ) and less than the maximum contention window value (CW max ), and decrements when it is sensed that the channel is in the idle state within one or more additional sensing time slot durations Ts. The values of CW min and CW max are based on the channel access priority class (CAPC) indicated to the UE. After a successful Listen-Before-Talk (LBT) procedure, the device can perform continuous transmission within the maximum COT without performing another LBT procedure, which is also based on the CAPC defined in TS 37.213.

[0227] The total COT of one or more autonomous uplink transmissions obtained through the channel access procedure defined in TS 37.213 (if the UE sets the "COT sharing indication" in the autonomous uplink UCI (autonomous uplink UCI, AUL-UCI) to "1" in the subframes within one or more autonomous uplink transmissions, the total COT includes the following DL transmissions as described in Article 4.1.3 of TS 37.213) can not exceed T ulmcot,p , where T ulmcot,pIt is given in Table 4.2.1-1 UL's Channel Access Priority Classes (CAPC) of TS 37.213.

[0228] Table 4.2.1-1 UL's Channel Access Priority Classes (CAPC) (TS 37.213)

[0229]

[0230] When using a higher CAPC, on average, the device accesses the channel faster (due to the CW max limitation) and for a shorter duration (due to the maximum COT duration T ulm cot,p ). The smaller the CAPC value, the higher the priority, and the larger the CAPC value, the lower the priority.

[0231] The channel access priority classes (CAPC) of radio bearers and media access control (MAC) control elements (CEs) are fixed or configurable according to TS 38.300. These elements: (i) are fixed at the lowest priority for padding buffer status reporting (BSR) and the proposed bit rate MAC CE; (ii) are fixed at the highest priority for signalling radio bearer (SRB) 0, SRB1, SRB3, and other MAC CEs; (iii) are configured by the gNB for SRB2 and data radio bearer (DRB). TS 38.300 also defines additional rules for using CAPC priorities for UL channel access.

[0232] When performing type 1 Listen Before Talk (LBT) for the transmission of an uplink transport block (TB) (see clause 4.2.1.1 of TS 37.213) and when the CAPC is not indicated in the DCI, the UE may select the CAPC in the following ways: (i) if the transport block (TB) includes only one or more MAC CE, use the highest priority CAPC of the one or more MAC CE; (ii) if the TB includes one or more service data units (SDUs) of the common control channel (CCCH), use the highest priority CAPC; (iii) if the TB includes one or more SDUs of the dedicated control channel (DCCH), use the highest priority CAPC of the one or more DCCH; or (iv) otherwise, use the lowest priority CAPC of the one or more logical channels, where the MAC SDU is multiplexed in the TB.

[0233] When the UE performs physical uplink shared channel (PUSCH) transmission through a type 1 channel access procedure on the configured resources, the UE determines the corresponding UL channel access priority p, see Table 4.2.1-1 of TS 38.300. When the UE performs PUSCH transmission through a type 1 channel access procedure (where the user plane data is indicated by a UL grant or is related to a random access procedure and the corresponding UL channel access priority p is not indicated), the UE determines p in Table 4.2.1-1 according to the same procedure as when performing PUSCH transmission through a type 1 channel access procedure on the configured resources.

[0234] The CAPC value is provided to the UE through the ChannelAccess-CPext field in DCI format 0_0, DCI format 0_1, format 0_2, format 1_0, format 1_1, and format 1_2 defined in TS 38.212. DCI format 0_1 is used to schedule one or more PUSCHs in a cell or to indicate the CG downlink feedback information (CG-DFI) to the UE. DCI format 0_2 and DCI format 0_0 are used to schedule PUSCHs in a cell. DCI format 1_0 is used to schedule PDSCHs in a DL cell. DCI format 1_1 is used to schedule one or more PDSCHs in a cell. DCI format 1_2 is used to schedule PDSCHs in a cell.

[0235] TS 38.212 specifies the allowed entries for channel access values in dynamic and semi-static modes. In the current system, there is no sidelink specification in the shared spectrum. (SL-U). It is expected that SL-U can follow the NR-U channel access specified in TS 37.213. In addition, it is expected that SL-U can reuse the sidelink resource allocation method as much as possible. CAPC is not defined for all potential values of sidelink priority for resource reservation, and vice versa. Therefore, when using CAPC for unlicensed channel access and sidelink resource priority separately based on existing specifications, one problem that may occur is that some combinations of CAPC and sidelink priority may be inconsistent. For example, it may happen that a high-priority CAPC level (e.g., "1") is used to access a reservation made using low-priority sidelink resource reservation (e.g., "8"), and vice versa. This may lead to unfair channel access and resource allocation, which may damage the QoS of different flows.

[0236] For mode 1 resource allocation, one problem is that DCI format 3_0 does not provide the necessary parameters for sidelink unlicensed access, such as CAPC. DCI format 3_0 is defined in TS 38.212 for scheduling NR PSCCH and NR PSSCH in a cell. DCI format 3_1 is defined in the same document for scheduling LTE PSCCH and LTE PSSCH in a cell. For mode 2 resource allocation, one problem is that CAPC and sidelink priority levels do not cover the same types of traffic. Different types of priorities (for channel access and resource selection) need to be adapted.

[0237] CAPC is used for the Listen-Before-Talk (LBT) sensing COT maximum duration. For the 5 GHz band, the timing of LBT (based on the CAPC value) is very short, about dozens to no more than a few hundred microseconds, which may be equivalent to one or several OFDM symbol durations. For example, when CAPC = 1, the LBT duration (when successful) corresponds to the sensing slot duration (9 microseconds) plus the backoff period duration (between 3×9 and 7×9 microseconds), i.e., less than 73 microseconds. The subcarrier spacing values of {15, 30, 60, 120} kHz correspond to OFDM symbol durations of {66.7, 33.3, 16.7, 8.33} microseconds respectively.

[0238] The purpose of SL resource reservation is to reserve some resources for future transmissions. These reservations are made only in SL resources (when the sidelink and uplink are on the same carrier, SL resources are a subset of UL resources), and only SL UE devices that can decode sidelink control information (SCI) can decode and respect these reservations. The reservation method is specified by the 3GPP protocol and is followed only by 3GPP devices that implement this feature. However, channel access (based on CAPC) is mandatory for any type of device (and thus non-3GPP) operating in the EU 5GHz unlicensed band and is specified by ETSI.

[0239] The duration of the SL resource reservation window is much longer than the channel access LBT. The SL sensing window is at most 100 milliseconds, while the resource selection window duration is T2 - T1 (see Figure 2 ), where T1 can be as low as zero and T2 min includes {1, 5, 10, 20} * 2 μ time slots, where the μ values {0, 1, 2, 3} correspond to the SCS values of {15, 30, 60, 120} kHz. This makes the T2 min value equivalent to {1, 5, 10, 20} milliseconds.

[0240] For each transmission in the unlicensed sidelink (SL-U), the UE uses CAPC to obtain channel access, and for each resource selection corresponding to that transmission, the SL-U UE uses the corresponding SL priority level. For example, when the resource pool index indicates a shared spectrum transmission, the DCI format 3_0 can be extended to cover the SL-U allocation in mode 1, and a bit field dedicated to CAPC can be used. In another embodiment, the DCI can have a bit field indicating the resource pool index for shared spectrum access.

[0241] COT is dedicated to shared spectrum (unlicensed) channel access. The UE may or may not need to perform LBT before transmitting on its reserved resources or without any reservation. The following are examples where the transmission may not require the LBT process (i.e., channel sensing): (i) if there is a short control transmission (with a short duration specified by the 3GPP NR-U and ETSI BRAN specifications) (type 2C); (ii) if there is a transmission in a shared COT that follows another transmission in the same COT. The following are examples where the transmission may require the LBT process (i.e., channel sensing): (i) when the transmission needs to initiate a COT (type 1); (ii) when transmitting in a shared COT and there is a gap with a previous transmission (e.g., type 1, type 2A, type 2B).

[0242] In one embodiment, the SL UE that initiates a COT (e.g., the initiating UE) is an SL UE that transmits after successfully performing type 1 Listen-Before-Talk (LBT), and this transmission is not completed in a shared COT. The UE that initiates a COT may or may not share its COT with other UEs. Those UEs that share the COT with the initiating UE may be referred to as "responding UEs".

[0243] Mode 2 also supports COT sharing. In this mode, important information for COT sharing is provided in the SCI. The present disclosure provides a COT sharing scheme for the SL for different resource reservations and LBT results.

[0244] Figure 6 A typical transmission time slot 600 including a PSFCH 623 opportunity according to an embodiment of the present disclosure is shown. The transmission time slot 600 includes a PSFCH 623 for receive-to-transmit (Rx-Tx) switching and guard symbols 621 and 624. The time slot 600 also includes an automatic gain control region 611, DMRS regions 612A, 612B, and 612C, PSSCH regions 613 to 618, and an AGC-PSFCH region 622.

[0245] In unlicensed channel access, if the transmission is part of COT sharing, the gap between consecutive transmissions determines the channel access sensing before transmission: (i) for a gap less than 16 microseconds, no channel sensing is required; (ii) for a gap equal to 16 microseconds, the channel can be sensed for 16 microseconds; (iii) for a gap equal to 25 microseconds, the channel can be sensed for 25 microseconds; (iv) for a gap greater than 25 microseconds, a full Listen-Before-Talk (LBT) operation can be performed through random backoff.

[0246] In an unlicensed sidelink (SL-U), there are two potential start symbols in a time slot, where if the LBT operation before the first start symbol fails, the second start symbol is used. If the LBT operation before the first start symbol fails, there may be a problem with PSFCH processing. To solve this problem, more PSFCH opportunities (or occurrences) can be implemented to mitigate the LBT failure before the PSFCH occurs. However, it is beneficial to indicate when and how the additional PSFCH opportunities occur. The higher subcarrier spacing (SCS) (60 kHz) does not have enough time to perform LBT. Therefore, the PSSCH transmission before the PSFCH may cause the LBT operation to fail, and additional techniques are needed to handle the PSFCH when the subcarrier spacing (SCS) value is higher.

[0247] In TS 37.213, multi-channel channel access is defined for multi-channel transmission. However, multi-channel COT is not defined. Therefore, it is necessary to define multi-channel COT and its sharing. RAN1 supports unlicensed sidelink (SL-U) multi-consecutive slots transmission (MCSt). The present disclosure provides an MCSt scheme for slots with two potential start symbols, especially an MCSt scheme when the first start symbol LBT fails.

[0248] In the NR-U system, continuous LBT failures are reported to the network. However, LBT is only performed before transmission and does not provide a complete picture of unlicensed channel occupancy. For the unlicensed sidelink system, it is beneficial to have a more comprehensive understanding of the usage of the unlicensed band in order to better schedule access. It is beneficial to provide SL-SSB transmission inside and outside COT sharing.

[0249] S-SSB : Under the duty cycle constraint, sidelink synchronization signal block (S-SSB) transmission can use Type 2A access procedure outside COT sharing. If the duty cycle constraint cannot be met, Type 1 channel access can be used. When using Type 1 channel access, the channel access priority class (CAPC) value is set to 1. Type 1 channel access can be used to initiate COT. However, in order to initiate COT, the COT initiator should provide other information, such as the remaining COT duration, the identity of the UEs that can share the COT, and the energy threshold (ED) that should be used for channel access purposes in this COT. In one embodiment, the UE transmitting the S-SSB can initiate COT provided that the UE transmits the S-SSB together with the necessary information for COT initiation and COT sharing or an indication of S-SSB initiating COT. However, considering the specific format of the S-SSB, this information may be difficult to transmit. In one embodiment, the disclosed UE can use the unused bits of the PSBCH.

[0250] In another embodiment, the S-SSB always initiates the COT, and the necessary information for sharing the COT (e.g., remaining time, energy detection threshold, ID of the UE that can share the COT) is transmitted via PSCCH / PSSCH (SCI-2) immediately following in the next time slot. However, if the UE only sends the S-SSB, it may not be beneficial to maintain channel control for longer than necessary. Therefore, in some embodiments, the S-SSB transmission does not initiate the COT. Thus, in some embodiments, if the transmission of the S-SSB does not carry the necessary information for COT sharing or the PSCCH / PSSCH carrying this information does not immediately follow in consecutive time slots, the COT is not initiated.

[0251] In principle, the COT can be initiated without sharing, as long as the COT only contains transmissions from the UE that initiated the COT. This does not violate the above conditions. In other words, the UE can initiate the COT via the S-SSB without sharing, provided that the next time slot provides information on the remaining COT duration. The present disclosure provides a technique for the UE to attempt to transmit the S-SSB for an ongoing COT.

[0252] The UE that can share the ongoing COT is called a "responding" UE and can meet some conditions to be able to share the COT. The UE is a responding UE for COT sharing if one of the following two conditions applies: (i) when the UE is a receiving UE (PSCCH / PSSCH); or (ii) when the UE is identified in the COT sharing information (by its ID). RAN1#111 may enable the responding UE to transmit the S-SSB in the shared COT. More precisely, for UE-to-UE COT sharing, when performing one or more S-SSB transmissions, when the responding UE intends to transmit the S-SSB within one or more RB sets corresponding to the shared COT, the responding UE can use the COT shared by the COT initiating UE (via type 1 channel access).

[0253] To enable S-SSB transmission in the shared COT, the COT initiator should track potential S-SSB transmitters in its vicinity and know their schedules, or use them as destinations. This may increase the complexity of the UE. The UE ID derived from the S-SSB transmission is not a one-to-one mapping with the true UE ID. More precisely, the ID used in the PSS / SSS sequence is related to the synchronization source, rather than the UE ID. Therefore, other means are needed to derive the true UE ID of the transmitting S-SSB. Limiting the transmission of the S-SSB to only the responding UE may affect the synchronization and discovery processes, as other potential S-SSB transmitters are not allowed to transmit during the shared COT.

[0254] When the S-SSB transmitter can decode the COT sharing information, a technique for S-SSB transmission in the shared COT can implement S-SSB transmission in the shared COT. For this technique, the channel access for S-SSB transmission shall follow the COT shared channel access rules. In this case, the CAPC for S-SSB transmission can be set to 1. This indicates that S-SSB transmission can be performed in any COT, regardless of the CAPC value used by the COT initiator.

[0255] Alternative techniques can enable the COT initiator to explicitly allow or prohibit S-SSB transmission in its COT. For example, the COT initiator can have a bit indication in the COT sharing information, indicating that during this COT, S-SSB transmission from outside the COT initiator may or may not be allowed. Another technique enables the COT initiator to add a bit to the UE identities allowed to share the COT, indicating whether these UEs are also allowed to transmit S-SSB. Another technique is the (pre)-configuration of each resource pool, indicating whether S-SSB transmission is allowed in the shared COT. For example, this configuration can be provided to the UE via SIB or RRC signaling at gNB initial access.

[0256] Figure 7 FIG. 700 is a flowchart showing S-SSB transmission according to an embodiment of the present disclosure. Step 705: Configure the UE supporting sidelink for S-SSB transmission. Step 710: The UE determines whether it is time to transmit. If the determination in step 710 is "no", the UE repeats step 710. If the determination in step 710 is "yes", then step 715 is executed: The UE determines whether a COT is in progress. If the determination in step 715 is "no", then step 720 is executed: The UE transmits S-SSB without using COT shared channel access and performs LBT operation through type 1 uplink channel access procedure.

[0257] If the determination in step 715 is "yes", then step 725 is executed: The UE determines whether it is sharing the COT with another device (e.g., another UE). If the determination in step 725 is "no", then step 730 is executed: The UE transmits S-SSB without using COT shared channel access and performs LBT operation through type 1 uplink channel access procedure. If the determination in step 725 is "yes", then step 735 is executed: The UE determines whether the UE is allowed to send S-SSB transmission in the current COT. If the determination in step 735 is "no", then step 740 is executed: The UE does not perform S-SSB transmission. If the determination in step 735 is "yes", then step 745 is executed: The UE uses COT shared channel access to transmit S-SSB.

[0258] PSFCH: When using Type 1 channel access, the CAPC for PSFCH transmission is set to 1. PSFCH only supports a single cyclic prefix extension (CPE) starting position. The provision of the CPE starting position (i.e., configuration, predefined, or indication, etc.) has not been disclosed in RAN1. For example, the CPE position can be such that the transmission gap before the PSFCH AGC symbol is 16 microseconds or less to avoid the need for an idle channel assessment, or 25 microseconds for a short deterministic idle channel assessment. The method of using the configuration or indication of the CPE position is more flexible compared to a predefined CPE starting position. Considering that PSFCH is a high-priority control message, this flexibility may be unnecessary. Therefore, the CPE can be predefined to ensure that there is a gap of at most 16 microseconds between the previous transmission and the AGC PSFCH symbol.

[0259] Whether PSFCH transmission can support Type 2A channel access and whether duty cycle constraints are applied are not supported. In RAN1#111, when performing one or more PSFCH transmissions, at least when at least one of the symbols / slots within one or more RB sets corresponding to the shared COT for the PSFCH transmission of a responding UE is for the COT-originating UE, the responding UE can use the COT shared by the COT-originating UE. In one embodiment, if the responding UE sends a PSFCH to the COT originator, the responding UE simultaneously sends a PSFCH transmission to SL UEs other than the COT originator (which may not be the responding UE).

[0260] When there is a combined transmission of S-SSB and PSFCH using the Type 2A channel access procedure, it may affect the S-SSB transmission, or when the exemption rules are not met, additional rules may be needed for transmission decisions. If the common duty cycle of S-SSB and PSFCH is very low, there will be no problem, and both S-SSB and PSFCH can use Type 2A for channel access. On the other hand, if additional PSFCH and / or S-SSB opportunities are added to compensate for potential LBT failures, the duty cycle limit may be exceeded.

[0261] In an embodiment where Type 2A is used for the PSFCH, when the exemption rule is not met, Type 2A channel access is not applicable to the PSFCH to enable the gNB to configure whether Type 2A channel access can be used for the PSFCH. Some UEs use Type 2A channel access while some do not, which may cause fairness issues for the PSFCH. If both the S-SSB and PSFCH transmissions use Type 2A channel access, their duty cycles are concentrated together. This method requires that if the duty cycle limit is reached, Type 2A channel access can no longer be used. If the S-SSB transmission uses Type 1 channel access, this may affect the S-SSB transmission. To avoid this, if the duty cycle limit is approaching, Type 1 channel access can be used to transmit the PSFCH while continuing to use Type 2A, 2B, or 2C channel access to transmit the S-SSB.

[0262] It should be noted that the UE needs to predict when the duty cycle limit will be reached and stop using Type 2A channel access for the PSFCH before reaching this limit. To avoid affecting the S-SSB transmission, this method makes a conservative decision to stop using Type 2A channel access for the PSFCH. In any case, there may be situations where the PSFCH cannot use Type 2A channel access. Therefore, a practical technique for PSFCH transmission is to use Type 1 channel access (CAPC value of 1) instead of using Type 2A channel access to transmit the PSFCH. In an embodiment, Type 2A channel access is used to transmit the S-SSB, while Type 1 or non-Type 2A channel access is used to transmit the PSFCH.

[0263] The sidelink supports subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, and 120 kHz. Type 2A channel access includes sensing that the channel is idle for at least 25 microseconds. For higher SCSs (60 kHz and 120 kHz), 25 microseconds is longer than the duration of a single OFDM symbol (i.e., the duration of the guard symbol). Therefore, even when using Type 2A channel access, the transmission of the PSFCH may be blocked by the transmission of the PSCCH / PSSCH.

[0264] In Type 1 channel access, the delay duration T immediately before transmission dDuring all the sensing time slot durations, it can be sensed that the channel is in an idle state. When CAPC = 1, the delay duration is 25 microseconds. Therefore, high SCS (such as in type 2A channel access) may cause blocking. The transmission time of PSFCH is relatively short because it only occupies two symbols, which means it takes 18 microseconds (SCS 120 kHz) to 143 microseconds (SCS 15 kHz). For short control signal transmission, if the transmission time is less than 584 microseconds, type 2C channel access can be used. To avoid the blocking of PSFCH caused by PSSCH transmission, type 2C channel access can be used. In this way, the blocking problem of PSSCH transmission expected during the shared COT is solved. For other types of transmissions existing in the channel, such as WIFI expected for transmissions not sharing COT, the blocking is avoided through type 1 channel access.

[0265] Therefore, in one embodiment, type 2A channel access is used to transmit S-SSB during COT sharing, type 2C channel access (without channel sensing) is used to transmit PSFCH, and type 1 channel access is used to transmit PSFCH when not sharing COT. This method can be (pre)-configured for each resource pool. For mode 1 (scheme 1), it can be provided through SIB, or for both modes (mode 1 and mode 2), it can be provided through RRC configuration. In an alternative embodiment, the channel access types for S-SSB transmission and for PSFCH transmission are provided by the COT initiator as part of the COT sharing information.

[0266] For sidelink unlicensed transmission, two potential starting point symbols are supported. If the LBT fails before the first starting symbol, a second LBT can be performed before the second starting symbol. If the second LBT is successful, the sidelink transmission can start. This transmission may overlap with the PSFCH transmission timing, which is not desirable.

[0267] In one embodiment of the PSFCH time slot, if the LBT period before the first starting symbol fails, the UE cancels its PSCCH and PSSCH transmissions to avoid overlapping with the PSFCH. In different embodiments, if the second starting symbol is quite close to the first starting symbol, so that there are sufficient resources to transmit the PSCCH and short (optional) PSSCH without overlapping with the PSFCH, the PSCCH and PSSCH transmissions are maintained. In different embodiments, if the transmission in the first starting symbol fails due to LBT failure, the transmission in the second starting symbol continues, and there is signaling to cancel the PSFCH transmission (such as in SCI-2). This signaling occurs before the PSFCH timing.

[0268] To handle potential failures during PSFCH transmission, e.g., LBT failures, additional PSFCH opportunities can be added and dynamically indicated. Thus, if the transmission of PSFCH fails at some default opportunities, the additional opportunities can be used. In COT, since type 1 channel access is performed before COT starts and the gap between transmissions is short, the protection for transmission is stronger. Thus, additional PSFCH opportunities may be unnecessary. The configuration or pre-configuration of each resource pool can indicate the additional PSFCH opportunities and can indicate to disable these opportunities during COT sharing. This can be solved by (pre-)configuring two sets of periods inside and outside COT.

[0269] Alternatively, the COT initiator can decide and indicate to the UEs sharing the COT the available PSFCH opportunities (i.e., disable additional PSFCH opportunities during COT). For example, the COT initiator can dynamically indicate during transmission (e.g., SCI format-2) the (additional) PSFCH opportunities allowed for HARQ of that transmission. When additional PSFCH opportunities are not used, dynamic signaling can be used to cancel the additional PSFCH not used by the COT initiator for the rest of COT or for each transmission. The present disclosure provides a new SCI format: SCI-1 bitfield or SCI-2 bitfield, to cancel additional PSFCH opportunities.

[0270] As in other opportunities of the present disclosure, the configuration can be provided by common SIB, RRC, MAC CE, etc. If the timer times out, these configurations may or may not be associated with a validity timer and another default (pre-)configuration.

[0271] Figure 8 FIG. 800 is a flowchart showing an example of a PSFCH transmission procedure according to an embodiment of the present disclosure. Step 805: The UE can receive data and optional additional PSFCH opportunities (or instances). Step 815: The UE determines whether COT is in progress. If the determination in step 815 is "no", then step 820 is executed: The UE can use the PSFCH opportunities (pre-)configured or indicated by a data transmitter outside COT, and then proceed to step 835. If the determination in step 815 is "yes", then step 825 is executed: The UE determines whether the UE shares COT with other UEs. If the determination in step 825 is "no", then step 820 is executed: The UE can use the PSFCH opportunities (pre-)configured or indicated by a data transmitter outside COT. If the determination in step 825 is "yes", then step 830 is executed: The UE can use the PSFCH opportunities (pre-)configured or indicated by a data transmitter inside COT, and then proceed to step 835.

[0272] Step 835: The UE performs LBT channel sensing at the default timing. Step 840: The UE determines whether there has been a failed LBT. If the determination in step 840 is "yes", then step 845 is executed: The UE performs LBT channel sensing at the additional timing or the alternative timing. Next, step 855: After successfully performing LBT at the additional timing, the UE transmits the PSFCH. If the determination in step 840 is "no", then the UE transmits the PSFCH.

[0273] Multi-Channel COT Definition and Access : Regarding multi-channel transmission, according to RAN1#110b, for the dynamic channel access mode in the case of multi-channel in SL-U, the NR-U UL channel access procedure is regarded as the baseline for transmission on multiple channels. The necessary condition for multi-channel transmission required by the NR-U UL multi-channel access procedure is that the UE can access all channels within the carrier bandwidth for which UL resources are scheduled or configured for the UE. The multi-channel COT is not defined in TS 37.213, but the conditions for multi-channel access are defined, and the multi-channel COT and multi-channel COT sharing are not explicitly defined. More precisely, multi-channel transmission is a single transmission.

[0274] Taking the NR-U UL multi-channel access as the baseline means that if an SL UE cannot access any channel for which SL resources are scheduled or configured for the UE, then this SL UE cannot perform transmission on any channel (RB set) for which SL resources are scheduled or configured for the UE (c i ∈C). For multi-channel access, before the start of transmission, the LBT type 1 procedure should be successfully performed on a randomly selected channel, and the LBT type 2 procedure should be successfully performed on each of the other BPW channels. In other words, in order to perform transmission on the channel c j (where c j ∈C is randomly selected uniformly), the SL UE uses type 1 channel access. In order to perform transmission on the channel c i ≠c j ,c i ∈C, the SL UE can sense this channel c mc within at least one sensing interval T i = 25 microseconds. In order to perform multi-channel transmission, the sensing in each channel (RB set) should indicate that the channel is available.

[0275] The sidelink multi-channel transmission can determine / define how long the multi-channel transmission can be performed. In one embodiment, the maximum duration of multi-channel transmission on any channel c i ≠c j ,c i ∈C can not exceed T mcot,p , where the value of T mcot,p is obtained through the channel c jDetermined by the type 1 channel access parameter. The present disclosure separately describes the concepts of multi-channel COT and multi-channel COT sharing. Similar to the single-channel COT, the present disclosure defines a multi-channel COT, which consists of consecutive transmissions in the same multi-channel, where these transmissions are separated by gaps not greater than 25 microseconds. To initiate a multi-channel COT, type 1 channel access should be performed in each channel before the initial transmission. Then COT sharing can be considered in each of these channels (RB sets), as Figure 9 shown.

[0276] Figure 9 Shows an example of multi-channel COT and COT sharing according to an embodiment of the present disclosure. Figure 9 Shows multi-channel transmissions of five UEs (UE 1 to UE 5) separated by gaps less than or equal to 25 microseconds. In one embodiment, if the gaps in each channel are less than or equal to 25 microseconds, the gaps between channel transmissions may not be time-aligned. In an alternative embodiment, the gaps can be aligned. Therefore, the UE can use cyclic prefix extension (CPE) to ensure gap alignment.

[0277] The first channel transmission (top row) includes an LBT type 1 period, a sidelink (SL) UE 1 channel transmission period, a sidelink (SL) UE 2 channel transmission period, and a sidelink (SL) UE 3 channel transmission period. The second channel transmission includes an LBT type 1 period, a sidelink (SL) UE 1 channel transmission period, a sidelink (SL) UE 2 channel transmission period, and a sidelink (SL) UE 5 channel transmission period. The third channel transmission includes an LBT type 1 period, a sidelink (SL) UE 1 channel transmission period, a sidelink (SL) UE 2 channel transmission period, and a sidelink (SL) UE 4 channel transmission period. The fourth channel transmission (top row) includes an LBT type 1 period, a sidelink (SL) UE 1 channel transmission period, a sidelink (SL) UE 2 channel transmission period, and a sidelink (SL) UE 4 channel transmission period.

[0278] To initiate and share COT, the COT initiator sends a multi-channel transmission after using type 1 channel access in each channel, which includes the necessary information for COT sharing. During multi-channel COT, as long as it meets the definition, multi-channel transmissions initiated by UEs sharing the COT can occur in any subset of the channels. The maximum duration is defined by the CAPC used for the first multi-channel transmission. COT sharing can be COT sharing in each individual channel while following the gap condition. COT sharing can be dedicated only to multi-channel transmissions, where transmissions from UEs sharing the multi-channel COT may be only within the same set of channels where the COT was initiated. Each channel provides COT sharing information. Each channel carrying the HARQ corresponding to that channel provides the PSFCH.

[0279] Multi-channel occupancy can be shared only with UEs scheduled to transmit over the entire set of channels for multi-channel occupancy or intended for sidelink multi-channel transmissions.

[0280] Multi-channel occupancy can be shared with only one UE at a time (no FDM).

[0281] The channel occupancy sharing information transmitted in time slot n can indicate the remaining channel occupancy duration in the number of time slots K.

[0282] If a UE shares a multi-channel occupancy initiated by another UE through a channel access procedure on a multi-channel to send one or more SL transmissions (e.g., the channel access procedure described in clause 4.5.6.3 of TS 37.213), then the UE can, after the transmission gap, send an SL multi-channel transmission after the SL multi-channel transmission performed by the UE that initiated the multi-channel occupancy in the following ways:

[0283] (i) If the transmission gap is at least 25 microseconds, the UE can send an SL multi-channel transmission after performing the type 2A channel access procedure described in clause 4.5.2.1 of TS37.213 on each channel of the multi-channel shared COT;

[0284] (ii) If the transmission gap is 16 microseconds, the UE can send an SL multi-channel transmission after performing the type 2B channel access procedure described in clause 4.5.2.2 on each channel of the multi-channel shared COT;

[0285] (iii) If the transmission gap is at most 16 microseconds, the UE can perform the type 2C channel access described in clause 4.5.2.3 of TS 37.213 on each channel of the multi-channel shared COT and send an SL multi-channel transmission on that channel.

[0286] The transmission gap in multi-channel occupancy sharing is defined as the maximum transmission gap in all shared multi-channels.

[0287] Figure 10 An example of the frame structure 1000 of sidelink New Radio (SL NR) mode 2 according to an embodiment of the present disclosure is shown. In a time slot with 14 symbols, the size of sub-channel 0 is 10 resource blocks (RBs). There are many potential sub-channel sizes. After the AGC region, there is a PSCCH region, which includes a first-phase SCI (not shown) and a second-phase SCI carried in the resources of the PSSCH region. Resource blocks 1010, 1011, 1020, and 1021 are part of the PSSCH. Some PSSCH resource units (Res) carry DMRS and potential CSI, but are not shown. The last region is the protection region.

[0288] Figure 11 An example of the frame structure 1100 of sidelink New Radio (SL NR) mode 2 configured with PSFCH according to an embodiment of the present disclosure is shown. The frame structure 1100 is similar to Figure 10 the time slot structure 1000 therein, except that the last two symbols of the PSSCH region are used for protection and PSFCH. In this example, according to Figure 11 the legend of, the PSFCH is (pre)-configured to support HARQ-ACK and IUC (UE-to-UE coordination) signals. The resources for HARQ-ACK and IUC are configured separately, and each resource can span more than one sub-channel.

[0289] Figure 12 An example of the period 1200 of the PSFCH according to an embodiment of the present disclosure is shown. In Figure 12 it, the PSFCH resources are shaded. Figure 12 Shows (i) PSFCH (no PSFCH) when disabled; (ii) PSFCH in each time slot; (iii) PSFCH in every other time slot; (iv) PSFCH in every fourth time slot.

[0290] For co-channel coexistence in Rel-18, dynamic resource pool sharing has the following constraints. For NR PSFCH (if configured), at least the following alternatives are supported: (i) Alternative 1: Avoid PSFCH transmission in time slots overlapping with sub-frames used for LTE SL transmission. Further study (FFS): It can be avoided by the UE transmitting PSFCH and / or the UE transmitting PSSCH; (ii) Alternative 2: The NR SL UE uses a periodically repeated set of PSFCH time slots. Further study (FFS): The period of the set.

[0291] In alternative 1, the NR SL UE can avoid transmitting PSFCH in time slots that overlap with the subframes used for LTE SL transmission. In the case where the TX UE performs this action, when selecting resources for transmission with HARQ enabled, the TX UE needs to ensure that the time slots for PSCCH / PSSCH transmission and the time slots for feedback from the RX UE are available and not used by the LTE SL UE. In the case where the RX UE performs this action, based on LTE sensing information, if a time slot overlaps with LTE SL transmission, the RX UE will not transmit on the PSFCH of that time slot.

[0292] In alternative 2, the NR SL UE can transmit PSFCH only in time slots that belong to a subset of the full set of periodically PSFCH-enabled time slots. This subset is called the basic resource set, and it repeats over time. The advantage of using such a subset of PSFCH time slots is that when the LTE SL UE performs SL RSSI measurements, high RSSI can be detected on these subframes, thus avoiding such a situation in its own transmissions.

[0293] In the present disclosure, the following terms can be used:

[0294] (i) Traditional NR device, which does not support coexistence capabilities.

[0295] (ii) LTE traditional device, which can use RSSI to avoid occupying resources. Therefore, the stronger the RSSI, the greater the likelihood that LTE will not use these resources.

[0296] (iii) Traditional device with a single PSFCH occasion period configured as 1, 2, or 4, used for transmitting HARQ feedback.

[0297] In alternative 1, the NR TX UE cannot avoid LTE resource reservation that occurs after PSCCH / PSSCH but before PSFCH, or cannot avoid LTE's hidden resource reservation for it, while the RX UE that transmits PSFCH can avoid it. When NR users do not use the (pre)-configured PSFCH resources, the impact on the NR system is too large, and there may often be at least one LTE user in the PSFCH time slots. Discarding (ACK / ) / NACK has an impact on multicast operations, or delaying (ACK / ) / NACK has an impact on specifications / backward compatibility.

[0298] In alternative 2, LTE RSSI measurements cannot reliably enable all legacy LTE devices to avoid the NR PSFCH, especially in time slots that have only the NR PSFCH and no PSCCH / PSSCH. Using overlapping resources has an impact on LTE performance. As the number of NR users increases, the performance of NR UEs becomes ambiguous.

[0299] It is noted that alternative 2 prevents NR users from using potential PSFCH time slots, which affects NR performance, especially when the number of NR users increases. Even in the absence of LTE, the NR PSFCH cannot use time slots that are not in the periodic set. Additionally, alternative 2 does not help LTE when there are also legacy NR UEs in the same pool (which is a requirement of the WID).

[0300] By introducing additional periods, e.g., 5 and / or 10 (also divided into 20), a PSFCH resource utilization similar to that of the periodic set in Alt 2 can be obtained. Given the significant impact on the specification and backward compatibility issues, it is unlikely to implement new deferral behavior or new periodic basic set operations. This disclosure provides a new solution for LTE and NR sidelink coexistence that is different from alternative 1 and alternative 2.

[0301] This disclosure provides a method for coexistence. In the proposed method, an additional (second) PSFCH period is used to identify the PSFCH time slots to which dynamic coexistence is applied. In these PSFCH time slots corresponding to the second period, when a conflict with LTE transmission is detected, the transmission of the PSFCH can be discarded or deferred. When an SL UE with new features has to send PSCCH / PSSCH (corresponding to the second PSFCH period), the SL UE can defer the transmission if there is a PSFCH conflict with LTE.

[0302] In the proposed method, the first PSFCH period corresponds to the legacy PSFCH resources used by legacy devices. On these resources, the PSFCH transmission is carried out even if an SL LTE and SL NR conflict is identified. For example, an sl-PSFCH-Period of 2 time slots is configured, and a new sl-PSFCH-Period-Coex of 4 time slots is configured. Although there may be a conflict with LTE scheduling, the PSFCH transmission on the sl-PSFCH-Period is not discarded or deferred. Due to the periodic transmission (higher RSSI), the LTE scheduler may avoid scheduling LTE SL transmissions in this period. For coexistence purposes, the transmissions on the sl-PSFCH-Period-Coex period may be discarded and deferred. LTE transmissions during this time may increase, so this time is not considered a strong RSSI period.

[0303] For a specific example, every other PSFCH resource is reserved and cannot be discarded due to coexistence, and every other PSFCH resource may be discarded for coexistence purposes. Additional periods (e.g., 8) can be defined for Rel-18, thus enabling, for example, a sl-PSFCH-Period of four (4) time slots and a sl-PSFCH-Period-Coex of eight (8) time slots. Making sl-PSFCH-Period equal to sl-PSFCH-Period-Coex would cause alternative 1 to always perform the avoidance behavior, which is the alternative that makes sl-PSFCH-Period-Coex optional. If the additional period is defined as a protected time slot that does not perform the avoidance behavior in Alt 1, then sl-PSFCH-Period being equal to sl-PSFCH-Period-Coex needs to be prohibited.

[0304] Figure 13 PSFCH coexistence 1300 according to an embodiment of the present disclosure is shown. PSFCH 1305 includes a PSFCH period that occurs simultaneously with a second PSFCH period, and the second PSFCH period allows PSFCH 1305 when there is no overlap with LTE. PSFCH 1310 includes a PSFCH period that occurs simultaneously with a first PSFCH period, and the first PSFCH period is always available for PSFCH. PSFCH 1315 includes a PSFCH period that occurs simultaneously with a second PSFCH period, and the second PSFCH period is discarded when there is an overlap with LTE. PSFCH 1320 includes a PSFCH period that occurs simultaneously with a first PSFCH period, and the first PSFCH period is always available for PSFCH. Finally, PSFCH 1325 includes a PSFCH period, where the second PSFCH period allows PSFCH 1325 when there is no overlap with LTE.

[0305] The second PSFCH period can be (pre)-configured and is a multiple of the first PSFCH period. In this embodiment, as a set, the time slots that can coexist are a subset of the total PSFCH time slot set. If a PSFCH time slot is in this subset, coexistence can occur. Otherwise, the PSFCH time slot can always be used. In an alternative embodiment, the periods can also be the same, in which case, unless there is a period offset, it will always coexist with LTE. In an embodiment with the same period and offset, as a set, these sets do not overlap. All PSFCH opportunities either belong to the protection set or the coexistence set. If it is known that the periods are the same, only the offset (or delay) needs to be (pre)-configured or dynamically indicated.

[0306] In an alternative embodiment, for Rel-18 UEs that support coexistence features, these operations are described in terms of sets or protected (no coexistence). If the sets are overlapping, the order of checking is important for the overlapping time slots. For example, Figure 14 and Figure 15 The flowcharts shown first check whether coexistence is to be performed, but it is also possible to check whether the PSFCH is protected. As long as the order of checking is determined, there is no particular limitation on the value of the period or the size of the set. The enabling and disabling of the second PSFCH period can be indicated by DCI, MAC-CE, or RRC commands (from the gNB or from another UE). Each PSFCH time slot can correspond to one or more PSCCH / PSSCH transmissions.

[0307] Figure 14 FIG. 1400 is a flowchart that describes an example of NR SL UE coexistence in which data (PSCCH / PSSCH) is transmitted (i.e., PSFCH is received) according to an embodiment of the present disclosure. Step 1405: An LTE / NR SL UE having two transceiver modules is used to operate in LTE and NR protocols. Step 1410: The UE determines whether a PSCCH or PSSCH is scheduled. If the determination in step 1410 is "no", the UE returns to step 1405 and continues to check whether a PSCCH or PSSCH is scheduled. If the determination in step 1410 is "yes", then step 1415 is performed: The UE determines whether the PSFCH for transmission will be in the second PSFCH period.

[0308] If the determination in step 1415 is "no", then step 1420 is performed: The UE transmits the PSCCH / PSSCH corresponding to the first PSFCH period. If the determination in step 1415 is "yes", then step 1425 is performed: The UE determines whether the PSFCH in the second PSFCH will overlap with the sidelink LTE transmission. If the determination in step 1425 is "no", then step 1430 is performed: The UE transmits the PSCCH / PSSCH corresponding to the first PSFCH period. If the determination in step 1425 is "yes", then step 1435 is performed: The UE re-schedules (or discards or postpones) the PSCCH or PSSCH.

[0309] Figure 15Flowchart 1500 is an example describing NR SL UE coexistence in which data (PSCCH / PSSCH) is received (i.e., PSFCH is transmitted) according to an embodiment of the present disclosure. Step 1505: An LTE / NR SL UE with two transceiver modules is used to operate in LTE and NR protocols. Step 1510: The UE determines whether PSCCH or PSSCH has been received. If the determination in step 1510 is "No", the UE returns to step 1505 and continues to check whether PSCCH or PSSCH has been received. If the determination in step 1510 is "Yes", then step 1515 is executed: The UE determines whether the PSFCH will be transmitted in the second PSFCH period.

[0310] If the determination in step 1515 is "No", then step 1520 is executed: The UE transmits the PSFCH in the first PSFCH period. If the determination in step 1515 is "Yes", then step 1525 is executed: The UE determines whether the PSFCH in the second PSFCH period will overlap with the sidelink LTE transmission. If the determination in step 1525 is "No", then step 1530 is executed: The UE transmits the PSFCH in the second PSFCH period. If the determination in step 1525 is "Yes", then step 1535 is executed: The UE discards the PSFCH.

[0311] Handling Single-Module NR SL UE : In different embodiments, an SL UE including two (dual) modules LTE and NR can exchange capability information with other UEs that only support the NR module. In such an embodiment, the dual-module UE supports indicating the competition between the PSFCH opportunity and the LTE transmission to the single-module UE (e.g., IUC class), and indicating an additional opportunity for PSFCH transmission to the second UE (single-module).

[0312] The present disclosure provides a method that can be used to handle the LBT failure of SL-U PSFCH. In this embodiment, two sets or two periods of PSFCH opportunities are configured for SL-U. A first set of fixed PSFCH configuration transmission opportunities is provided, and each PSCCH / PSSCH transmission therein includes at least one opportunity. A second set of PSFCH configuration transmission opportunities is also provided, which can be enabled or disabled, and can be periodic or single-shot for PSCCH / PSSCH transmission. The second set can be enabled or disabled through a dynamic indication in the SCI, or through a MAC CE or PC5_RRC. The enabling can be for the entire second set or a subset of the second set, and the second set can be indicated by a bitmap.

[0313] In this embodiment, the second set can be enabled after receiving a PSFCH failure in the first set, or after receiving a PSFCH failure multiple times in the first set (period). Both the first PSFCH set (period) and the second PSFCH set (period) can be configured, and the second set is enabled respectively during the corresponding PSCCH / PSFCH transmission.

[0314] Similar embodiments can be used for multicast transmission, i.e., only NACK or only ACK or ACK / NACK feedback. For multicast, the feedback (only ACK, only NACK or ACK - NACK) is dynamically indicated or indicated by configuration. Similarly, the first set of PSFCH timing (or the first period) and the second set of PSFCH timing (the second period) for feedback PSFCH opportunities can be indicated by dynamic SCI, MAC - CE or RRC. In different embodiments, the indication of PSFCH opportunities is not explicitly provided, but is based on rules that can be pre - configured (prior). For example, for the case of only ACK, only the first set can be used; for the case of only NACK, both the first set and the second set of PSFCH opportunities can be used.

[0315] For the dynamic mode, when LTE co - existence is detected, the NR module starts a timer (e.g., the number of time slots). When the NR device is to perform a transmission, it disables HARQ - ACK feedback, and the device can adopt a fixed number of transmission times for each data packet. The timer can be updated. If there is no LTE co - existence, a timer check is performed. If the timer times out, the NR device can enable HARQ - ACK feedback. Otherwise, the NR device continues to disable HARQ feedback.

[0316] Figure 16 FIG. 1600 is a flowchart showing an example of a PFSCH period according to an embodiment of the present disclosure. Step 1610: The UE determines whether LTE co - existence has been detected. If the determination in step 1610 is "yes", then step 1620 is executed: The UE starts a timer and proceeds to step 1640. If the determination in step 1610 is "no", then step 1630 is executed: The UE determines whether the timer has timed out. If the determination in step 1630 is "no", the UE proceeds to step 1640. If the determination in step 1630 is "yes", the UE transmits PSCCH or PSSCH with HARQ enabled, and then returns to step 1620. Step 1640: The UE transmits PSCCH or PSSCH with HARQ disabled. Step 1650: The UE updates the timer, and then returns to step 1620.

[0317] Figure 17It is a flowchart showing an example of the transmission process of a sidelink synchronization signal block (S-SSB) according to an embodiment of the present disclosure. 1705: The UE receives channel occupancy sharing information from a second UE that initiates channel occupancy. The channel occupancy sharing information includes the remaining channel occupancy duration and one or more identifiers of one or more UEs. 1710: The UE determines that the UE is sharing channel occupancy based on the channel occupancy sharing information. 1715: In response to this determination, the UE transmits a sidelink synchronization signal block (S-SSB) during a first channel occupancy time.

[0318] Although the present disclosure provides several embodiments, it should be understood that the disclosed systems and methods may also be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The examples of the present disclosure should be considered illustrative rather than restrictive and are not limited to the details given herein. For example, various elements or components may be combined or incorporated in another system, or certain features may be omitted or not implemented.

[0319] In addition, without departing from the scope of the present disclosure, the techniques, systems, subsystems, and methods described and illustrated as discrete or separate in various embodiments may be combined or integrated with other systems, modules, techniques, or methods. Other items shown or described as being coupled, directly coupled, or communicating with each other may be indirectly coupled or communicating electrically, mechanically, or otherwise through some interface, device, or intermediate component. Other variations, substitutions, and changes of examples can be determined by those skilled in the art and can be made without departing from the spirit and scope disclosed herein.

Claims

1. A method implemented by a user equipment (UE), characterized in that, comprising: receiving channel occupancy sharing information from a second UE that initiates channel occupancy, wherein the channel occupancy sharing information includes remaining channel occupancy duration and one or more identifiers of one or more UEs; determining, according to the channel occupancy sharing information, that the UE shares the channel occupancy; in response to the determination, transmitting a sidelink synchronization signal block (S-SSB) at a first channel occupancy time.

2. The method according to claim 1, characterized in that, transmitting the S-SSB at the first channel occupancy time includes: transmitting the S-SSB during the remaining channel occupancy duration.

3. The method according to claim 1 or 2, characterized in that, determining that the UE shares the channel occupancy according to the one or more identifiers of the one or more UEs.

4. The method according to any one of claims 1 to 3, characterized in that, further comprising: before determining that the UE shares the channel occupancy, determining whether the first channel occupancy time is still ongoing.

5. The method according to any one of claims 1 to 4, characterized in that, receiving the channel occupancy sharing information through at least one of a physical sidelink control channel (PSCCH) or a physical sidelink shared channel (PSSCH).

6. The method according to any one of claims 1 to 5, characterized in that, the occupancy sharing information further includes information indicating whether S-SSB transmission is allowed.

7. An apparatus, characterized in that, comprising: one or more processors operably coupled to the transceiver; a non-transitory memory storing programming instructions that, when executed by the one or more processors, cause the apparatus to perform the method according to any one of claims 1 to 6.

8. A non-transitory computer-readable medium, characterized in that, comprising a computer program product for use by a user equipment (UE), the computer program product including computer-executable instructions stored in the non-transitory computer-readable medium, the computer-executable instructions, when executed by one or more processors, cause the UE to perform the method according to any one of claims 1 to 6.

9. A method implemented by a user equipment (UE), characterized in that, comprising: performing listen-before-talk (LBT) channel sensing at a first physical sidelink feedback channel (PSFCH) opportunity; Determine whether the LBT channel sensing fails; In response to determining that the LBT channel sensing does not fail, transmit the PSFCH resource block; In response to determining that the LBT channel sensing fails, perform LBT channel sensing at a second PSFCH opportunity; After successfully performing LBT at the second PSFCH opportunity, transmit the PSFCH resource block.

10. A user equipment (UE), characterized in that, comprising: a transceiver for communicating with an access node of a wireless network and transmitting a physical sidelink feedback channel (PSFCH) resource block to another UE in the coverage area of the wireless network; one or more processors operatively coupled to the transceiver; a non-transitory memory storing programming instructions which, when executed by the one or more processors, cause the UE to perform the following operations: perform Listen Before Talk (LBT) channel sensing at a first PSFCH opportunity; determine whether the LBT channel sensing fails; in response to determining that the LBT channel sensing does not fail, transmit the PSFCH resource block; in response to determining that the LBT channel sensing fails, perform LBT channel sensing at a second PSFCH opportunity; after successfully performing LBT at the second PSFCH opportunity, transmit the PSFCH resource block.

11. A method implemented by a user equipment (UE), characterized in that, comprising: determine whether a set of first-configured physical sidelink feedback channel (PSFCH) opportunities is configured to coexist with long term evolution (LTE) transmission; in response to determining that the set of first-configured PSFCH opportunities is configured to coexist with the LTE transmission, do not transmit the PSFCH resource block; in response to determining that the set of first-configured PSFCH opportunities is not configured to coexist with the LTE transmission, transmit the PSFCH resource block.

12. A user equipment (UE), characterized in that, comprising: a transceiver for communicating with an access node of a wireless network and transmitting a physical sidelink feedback channel (PSFCH) resource block to one or more UEs in the coverage area of the wireless network; one or more processors operatively coupled to the transceiver; a non-transitory memory storing programming instructions which, when executed by the one or more processors, cause the UE to perform the following operations: Determine whether the set of PSFCH timing for the first configuration is configured to coexist with Long Term Evolution (LTE) transmission; In response to determining that the set of PSFCH timing for the first configuration is configured to coexist with the LTE transmission, do not transmit the PSFCH resource block; In response to determining that the set of PSFCH timing for the first configuration is not configured to coexist with the LTE transmission, transmit the PSFCH resource block.

13. A method implemented by a user equipment (UE), characterized in that, comprising: Determine whether the first channel occupancy time is still ongoing; In response to determining that the first channel occupancy time is not ongoing, use the set of physical sidelink feedback channel (PSFCH) timing for the first configuration to transmit the PSFCH resource block; In response to determining that the first channel occupancy time is still ongoing, determine whether the UE is sharing the first channel occupancy time with a second UE; In response to determining that the UE is sharing the first channel occupancy time with the second UE, use the set of PSFCH timing for the second configuration to transmit the PSFCH resource block.

14. A user equipment (UE), characterized in that, comprising: A transceiver for communicating with an access node of a wireless network and transmitting a physical sidelink feedback channel (PSFCH) resource block to one or more UEs in the coverage area of the wireless network; One or more processors operably coupled to the transceiver; A non-transitory memory storing programming instructions that, when executed by the one or more processors, cause the UE to perform the following operations: Determine whether the first channel occupancy time is still ongoing; In response to determining that the first channel occupancy time is not ongoing, use the set of PSFCH timing for the first configuration to transmit the PSFCH resource block; In response to determining that the first channel occupancy time is still ongoing, determine whether the UE is sharing the first channel occupancy time with a second UE among the one or more UEs; In response to determining that the UE is sharing the first channel occupancy time with the second UE, use the set of PSFCH timing for the second configuration to transmit the PSFCH resource block.

15. A user equipment (UE), characterized in that, comprising: A transceiver for communicating with an access node of a wireless network and transmitting a physical sidelink feedback channel (PSFCH) resource block to one or more UEs in the coverage area of the wireless network; One or more processors operably coupled to the transceiver; A non-transitory memory storing programming instructions that, when executed by the one or more processors, cause the UE to perform the following operations: Determine whether a first channel occupancy time is still ongoing; In response to determining that the first channel occupancy time is not ongoing, transmit the PSFCH resource block using a second configured set of PSFCH opportunities; In response to determining that the first channel occupancy time is still ongoing, determine whether the UE is sharing the first channel occupancy time with a second UE among the one or more UEs; In response to determining that the UE is sharing the first channel occupancy time with the second UE, transmit the PSFCH resource block using a first configured set of PSFCH opportunities.

16. The UE according to claim 15, wherein, the programming instructions, when executed by the processor, further cause the UE to perform the following operations: Perform listen-before-talk (LBT) channel sensing at at least one default PSFCH opportunity.

17. The UE according to claim 15 or 16, wherein, the programming instructions, when executed by the processor, further cause the UE to perform the following operations: Determine whether the listen-before-talk (LBT) channel sensing fails; In response to determining that the LBT channel sensing does not fail, transmit the PSFCH resource block.

18. The UE according to any one of claims 15 to 17, wherein, the programming instructions, when executed by the processor, further cause the UE to perform the following operations: In response to determining that the LBT channel sensing fails, perform LBT channel sensing at another PSFCH opportunity; After successfully performing LBT at an additional PSFCH opportunity, transmit the PSFCH resource block.

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