TW202333528A - Methods and apparatus for sidelink communications - Google Patents

Abstract

Apparatus and methods are provided for sidelink resource selection in unlicensed frequency bands. In one novel aspect, a combination of SL resource selection procedure and a listen-before-talk (LBT) procedure are used for resource selection in unlicensed frequency bands. In one embodiment, the LBT procedure is performed before the SL resource selection procedure. In one embodiment, a protection gap between the potential success of the LBT procedure and a starting position of candidate resources is dynamically configured. In another embodiment, a self-defer mechanism is performed in a protection gap between a success of the LBT procedure and the transceiving of the SL packets, including using a cyclic prefix (CP) extension and a timing advance (TA) to align the boundary of LBT success and transceiving, or performing a second LBT immediately before the transceiving of the SL packets. In yet another embodiment, one or more reserved candidate resources within the COT can be shared to other UE(s).

Description

Sidelink communication method and user equipment thereof

The present invention relates generally to wireless communications and, in particular, to sidelink communications in the unlicensed spectrum.

Unless otherwise indicated, the methods described in this section are not prior art to the claims later listed and are not deemed prior art by inclusion in this section.

As 5G development and availability rapidly expands around the world, demand for wireless data continues to increase, which in turn will require more available spectrum to increase the capacity of future wireless communication systems. Therefore, the utilization of license-free spectrum, including 2.4GHz, 5GHz and 60GHz, has attracted widespread attention from academia and industry, which further promotes LTE Licensed Assisted Access (LAA) communications and 5G NR license-free (NR) in 3GPP. -U) Successful development of communications. These license-free radio access technologies (RATs) can be seen as complementary to licensed communications, further alleviating growing data demands.

Sidelinks were initially introduced in 3GPP Release 12 as device-to-device (D2D) communication to enable direct transmission between two devices without the need for data to pass through the network. Subsequently, sidelink technology was further expanded into the scope of LTE-based vehicle-to-everything (V2X) and/or cellular V2X (C-V2X), and/or NR-based V2X. The critical role and application of sidelink technology in LTE and NR make it a necessary remedy to support numerous use cases in future wireless communication systems. Based on the above observations, for the development of beyond 5G (B5G) and future 6G communication technology, the research and design of sidelink communication on the license-free spectrum (SL-U) is considered to be the most promising for further improvement and evolution of sidelinks. one of the directions. For the design of SL-U, one of the most critical issues is the harmonious and fair coexistence between the sidelinks and other existing technologies operating on the same frequency band, such as Wi-Fi and NR-U.

Improvements in sidelink resource allocation in unlicensed bands are needed to ensure harmonious coexistence with other RATs.

The following summary is illustrative only and is not intended to be limiting in any way. That is, the following summary is provided to introduce the concepts, highlights, benefits and advantages of the novel and non-obvious technologies described herein. Select embodiments are further described below in the detailed description. Accordingly, the following summary is not intended to identify essential features of the claimed subject matter, nor is it intended to be used to determine the scope of the claimed subject matter.

The present invention provides an apparatus and method for sidelink resource selection in a license-exempt frequency band. In a novel aspect, a combination of the SL resource selection process and the listen-before-talk (LBT) process is used for resource selection in license-exempt bands. In one embodiment, the LBT process is performed before the SL resource selection process. In one embodiment, the resource gap between the potential success of the LBT process and the starting position of the candidate resource is (pre-)configured or dynamically indicated based on one or more factors, wherein the one or more factors include channel status, th. Tier priority, CAPC value, and oversubscribed resource size. In another embodiment, the self-delay mechanism is implemented in the guard gap between the success of the LBT process and the transmission and reception of the SL packet. When the LBT is successful and the SL packet is not ready, the self-delay mechanism is executed; when the SL packet is ready, the second short LBT is executed immediately before the SL packet is sent and received. When the LBT is successful, the SL packet is ready, and the protection gap is greater than the preconfigured threshold, the self-delay mechanism is executed; the second short LBT is executed immediately before the SL packet is sent and received. When the LBT is successful, the SL packet is ready, and the protection gap is less than or equal to the preconfigured threshold, use cyclic prefix (CP) extension (CPE) or CPE and timing advance (TA) to align the success of the LBT process with the SL packet. The protection gap between sending and receiving. In yet another embodiment, a channel occupancy time (COT) is initiated after the LBT process is successful, and wherein one or more reserved candidate resources within the COT are shared to another UE.

The above summary of the invention does not limit the invention, and the protection scope of the invention is limited by the patent application scope.

The following description is the best embodiment for implementing the present invention. It is for the purpose of describing the principle of the present invention and is not intended to limit the present invention. The protection scope of the present invention should be limited by the patent application scope of the present invention.

Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

Figure 1A is a schematic system diagram of an example wireless network for sidelink data communication with other coexisting RATs in a license-exempt frequency band in accordance with an embodiment of the present invention. The wireless network 100 includes a plurality of communication devices or mobile stations, such as user equipments (UEs) 111, 112, 113, 114, and 115, which are configured with sidelinks in unlicensed frequency bands. Exemplary mobile devices in wireless network 100 have sidelink capabilities. Sidelink communication involves direct communication between end nodes or UEs without data passing through the network. For example, UE 113 communicates directly with UE 114 without going through a link with a network element. The range of sidelink transmission also supports relay from the UE to the network to expand the service range of the eNB, in which the inter-coverage UE acts as a relay node between the eNB and the out-of-coverage UE. For example, the UE 112 is connected to the base station 101 through an access link. The UE 112 provides network access to the UE 111 outside the coverage area through the sidelink relay. A base station, such as base station 101, may also be referred to as an access point, access terminal, base station, Node B, enhanced Node B (eNB), gNB, or other terms used in the art. The network can be a homogeneous network or a heterogeneous network, and can be deployed at the same frequency or at different frequencies. Base station 101 is an exemplary base station. As the demand for greater capacity and sidelink communications evolve, it becomes important for sidelink devices to use unlicensed bands and coexist harmoniously with other RAT devices operating in the same unlicensed bands. For example, neighboring UEs 116 and 117 communicate with base station 102 through other RATs (eg, WiFi), which share the same unlicensed frequency band. Neighboring UEs 118 and 119 communicate with the base station 103 through other RATs, such as NR, which also share the same unlicensed frequency band.

For sidelink transmissions on unlicensed spectrum (SL-U), efficient resource allocation is the most critical issue to ensure reasonable coexistence with other RATs operating in unlicensed spectrum (e.g., NR-U and Wi-Fi) one. Two modes of resource allocation schemes are determined for the NR sidelink. The first one is named Mode-1, while the second one is named Mode-2. For Mode 1, the gNB uses the Uu interface to schedule resource configuration. This mode is only applicable to sidelink UEs within network coverage. For Mode 2, the sidelink UE can automatically select resources from a (pre)configured resource pool based on the channel sensing mechanism on the PC5 interface. In this case, sidelink UEs can operate both within and outside coverage. When a transmitting sidelink UE attempts to select/reserve resources using Mode 2, it should perform a resource selection/reservation process consisting of two phases (resource sensing and resource selection/reservation). Typically, in the resource sensing phase, in order to avoid causing interference to existing sidelink transmissions operated by other sidelink UEs, potential candidate resources that can be used for sidelink transmission and reception are identified. Next, in the resource selection phase, the sidelink UE can select candidate resources for transmission block (TB) transmission with the assistance of sensing results. In a novel aspect, listen before talk or LBT (listen before talk, LBT) is used in the selection phase of license-free band resources. LBT is a spectrum sharing technology through which network initialization equipment must perform a clear channel assessment (CCA) check before starting transmission. Under the LBT mechanism, multiple UEs can share a channel and ensure fair coexistence between different RATs. In a novel aspect, a combined design of sidelink sensing and LBT is provided for the resource allocation scheme to ensure harmonious coexistence between the sidelink and other wireless systems.

Figure 1A further depicts a simplified block diagram of a mobile device/UE operating in a license-exempt frequency band. Take UE 111 as an example. UE 111 has an antenna 125 for transmitting and receiving radio signals. RF transceiver circuitry 123 coupled to the antenna receives RF signals from antenna 125, converts them into baseband signals, and sends them to processor 122. In one embodiment, the RF transceiver may include two RF modules (not shown). RF transceiver 123 also converts baseband signals received from processor 122 into RF signals and sends them to antenna 125 . The processor 122 processes the received baseband signal and calls different functional modules to perform functions in the UE 111 . Memory 121 stores program instructions and data 126 to control the operation of UE 111. Antenna 125 sends uplink transmissions to base stations and receives downlink transmissions from base stations.

UE 111 also includes a set of control modules that perform functional tasks. These control modules can be implemented through circuits, software, firmware or a combination thereof. The LBT module 191 executes the LBT process to prepare for UE sidelink (SL) transceiver in the unlicensed band, where the LBT process determines channel selection with other coexisting wireless systems in the unlicensed band. The selection module 192 executes a sidelink (SL) resource selection process, where the SL resource selection process selects candidate resources in the license-exempt frequency band for SL transceiver of the UE. When both the SL resource selection process and the LBT process are successful, the transceiver controller 193 sends and receives SL packets on the selected candidate resources. The dynamic configuration module 194 dynamically configures the parameters of the LBT process and the SL selection process.

Figure 1B depicts an exemplary flow diagram for sidelink communications over unlicensed spectrum using LBT sensing and selection, in accordance with an embodiment of the present invention. In a novel aspect, SL resource selection in license-exempt bands uses a combination of SL resource selection process and channel access (eg, LBT process). Each sidelink device performs independent asynchronous sidelink sensing to collect sensing information of the license-free spectrum for use in the secondary channel access (LBT) process after triggering the channel access (LBT). And can also be used to assist in the following sidelink selection/reservation process after the channel access (LBT) is successful and the packet arrives.

In step 151, the UE is in idle state. When the sidelink UE is not transmitting, it continues to sense the unlicensed channel resources in order to identify available candidate resources. In step 152, the UE determines whether to trigger LBT. In one embodiment, the LBT trigger time to start executing the LBT process is dynamically configured. In one embodiment, LBT is triggered when a new packet arrives or is ready for transmission. In another embodiment, the SL packets are periodic data and the LBT process is performed before the SL packets arrive or are ready for transmission. (Pre-)configure the trigger time or dynamically indicate the trigger time based on one or more trigger factors, where the trigger factors include the failure probability of the LBT process, channel load status information, channel access priority class (CAPC) Availability and channel congestion control information.

In step 161, the UE collects sensing information. During the sensing process, the sidelink UE decodes the first stage SCI from other sidelink UEs on the unlicensed channel. By decoding the first stage SCI, the sidelink UE can learn the resources that other sidelink UEs have reserved for their TB initial transmission and retransmission. During the sensing process, the sidelink UE also measures the sidelink reference signal received power (RSRP) transmitted from other sidelink UEs. The information element (IE) sl-RS-ForSensing from higher layers indicates whether the RSRP of the physical sidelink control channel (PSCCH) or the RSRP of the PSSCH is measured. The RSRP can be measured from the demodulation reference signal (DMRS) of the physical sidelink control channel (PSCCH), and/or the RSRP can be measured from the DMRS of the physical sidelink shared channel (PSSCH). The above sensing information, including the first stage SCI and RSRP, is stored by the sidelink UE and will be used in the subsequent resource selection process. At the system level, each sidelink device can implement an independent asynchronous sensing mechanism to collect sensing information in the unlicensed spectrum.

When the sidelink device wants to access the unlicensed spectrum, in step 162, the device determines whether to perform the LBT process. Random backoff counter generation time and channel access (LBT) trigger time can be dynamically indicated/configured separately. In one aspect of the present invention, in order to avoid potential LBT failures, the random backoff counter generation time and LBT trigger time in LBT can be individually and dynamically indicated/configured. For example, (pre)configure or indicate the random backoff counter generation time and LBT firing time when the packet is ready or after the packet is ready until the Packet Delay Budget (PDB) arrives. In another embodiment, if the packet is periodic, the random backoff counter generation time and LBT trigger time are indicated/configured before the packet is ready, and may depend on one or more trigger factors, including channel access (LBT ) failure probability (e.g., based on the ratio of the number of failures to the total number of LBT sensing times in the past X ms/slot, or the number of consecutive LBT failures exported/determined), channel load Status information, CAPC availability and channel congestion control information. For example, if the channel is more congested (e.g., the SL channel busy rate (CBR) is high or the LBT failure rate is high), the LBT can be performed earlier. Otherwise, it can be executed later. That is, the (earliest) time to perform an LBT for a potential data transfer can be a function of one or more trigger factors including channel status, data/channel prioritization and QoS.

If step 162 determines no, the sidelink device/UE moves to step 163 and waits for the next time slot. If step 162 determines yes, the UE performs LBT or channel access accordingly. In one embodiment, at step 164, the UE first determines the type of LBT process to be performed. In one embodiment, the LBT process initiates Channel Occupied Time (COT). If the LBT is used to initiate a COT or the LBT is outside the COT, configure a Type 1 LBT. If LBT is used in an originating/shared COT, the LBT type is (pre)configured as Type 2A LBT, Type 2B LBT or Type 2C LBT. At step 165, the LBT process is performed. In step 166, the UE determines whether the LBT was successful.

In step 166, the UE determines whether the LBT was successful. If step 166 determines that the LBT was unsuccessful, the UE moves to step 167 and determines whether the PDB is ready. If step 167 determines yes, the process ends. If step 167 determines NO, the UE moves to step 165 and performs another LBT.

If step 166 determines that the LBT is successful, the UE performs the SL resource selection process. Only when the channel access (LBT) is successful, i.e., indicating that the sensed license-exempt spectrum is idle, the device can occupy the corresponding channel for a period of time, i.e., COT. Within the COT, the SL-U device performs the sidelink resource selection/reservation process based on the sensing information to select/reserve resources for the current or next data (re)transmission. Furthermore, COT can only be used by the initiating device/cluster head and can also be shared with the echoing device or other devices in the group.

In step 171, the UE determines whether the packet is ready to be sent. If step 171 determines yes, the UE moves to step 172 and selects SL resources through the SL resource selection process. In one embodiment, LBT is performed before transmitting the SL packet. At step 174, the UE determines the LBT type. In step 176, the UE performs LBT immediately before the selected resource for SL transceiver.

If the determination in step 171 is negative, there is a protection gap between the successful LBT and the starting position of the selected SL resource. In one embodiment, in step 173, a self-defer mechanism is executed in the guard gap between the success of the LBT process and the transmission and reception of the SL packet. Before resource selection/reservation, the UE performs a relatively simple/short channel access (LBT) mechanism to initiate COT. If the gap does not exceed a certain time (for example, one symbol for all SCS cases or 1/2/4 symbols for 15/30/60 kHz SCS respectively), the device can use cyclic prefix (CP) extension and timing Advance (TA) to align the boundary between channel access (LBT) success time and resource selection/reservation time. Through this scheme, the SL-U device can be configured with more time and/or opportunities to attempt LBT, which further results in an increased probability of LBT success. In step 175, after the self-delay mechanism, the UE determines whether the packet is ready. If step 175 determines no, the UE moves to step 173 and performs further self-delay. If step 175 determines yes, in one embodiment, the UE moves to step 177 and performs a short LBT. At step 178, the UE determines whether the short LBT was successful. If step 178 determines yes, the UE moves to step 176 to perform LBT immediately before the selected SL resource. If step 178 determines no, the UE returns to step 173 and performs self-delay. In step 181, the UE determines whether the LBT before reserving SL resources is successful. If step 181 determines yes, the UE moves to step 182 and performs SL packet transmission and reception. In step 183, the UE determines whether this is the last reserved SL resource. If step 183 determines yes, the process ends. If step 183 determines NO, the UE moves to the next reserved resource in step 184, and then moves to step 164 to determine the LBT type to perform transceiver on the next reserved resource. If step 181 determines no, no SL packet is sent and the UE moves to step 183 to see if there are more reserved resources.

In a novel aspect, to avoid potential channel access (LBT) failures, the random backoff counter generation time and channel access (LBT) trigger time can be dynamically configured. For aperiodic and periodic data, the random backoff counter generation time and channel access (LBT) trigger time can be configured after the packet is ready and/or once ready until the PDB arrives. For periodic data, LBT can be configured before the packet is ready. Figures 2 and 3 depict exemplary processes for periodic and non-periodic data.

Figure 2 depicts a schematic diagram of aperiodic data transmission in a license-exempt frequency band with dynamic configuration parameters according to an embodiment of the present invention. In step 201, aperiodic data arrives and/or is prepared. After the packet preparation is completed, in step 210, a random backoff counter N may be generated first according to the CAPC and/or QoS of the packet type. Subsequently, at step 220, resource selection based on the LBT counter of Type 1 LBT is triggered. Period 231 is the LBT time with backoff counter N. A guard gap 232 between the tunnel access (LBT) success location and the resource selection/reservation location can be configured to avoid potential LBT failure. If the channel access (LBT) is successful, then in step 240, the device may start the resource selection/reservation process in the initiated COT. During this process, resources can be oversubscribed to account for potential LBT failures. During step 240, the UE selects one or a plurality of candidate resources, such as resource 221. In some scenarios, other UEs select candidate resources, such as resources 251, 252, and 253. The UE selects resources 241 for the SL packet.

Figure 3 depicts a schematic diagram of periodic data transmission in a license-exempt frequency band with dynamic configuration parameters according to an embodiment of the present invention. If the data is periodic, dynamically indicate/configure the random backoff counter generation time and channel access (LBT) trigger time before the packet is ready. In step 300, before the periodic packet is ready, a random backoff counter N and a channel access (LBT) trigger time may first be generated based on one or a plurality of trigger factors. Trigger factors include channel access (LBT) failure probability, channel load status information, and channel congestion control information. In one embodiment, the LBT failure probability is derived/determined based on one or more factors, wherein the one or more factors include the number of failures in the past X milliseconds/slot and the total number of channel access (LBT) sensed The ratio of times, and the number of consecutive channel access (LBT) failures. For example, if the channel is more congested (e.g., the SL channel busy rate (CBR) is high or the LBT failure rate is high), the LBT can be performed earlier. Otherwise, it can be executed later. In one embodiment, the earliest time to perform LBT for a potential data transfer may be a function of one or more trigger factors, including channel status, data/channel prioritization, and QoS.

In one embodiment, in step 300, before the periodic packet is ready for transmission, a random backoff counter N may be generated based on the known CAPC and/or QoS of the packet type. Channel access (LBT) can be triggered using a random backoff counter before periodic packets arrive. In step 320, periodic packets are prepared for transmission. At step 330, resource selection is performed based on the selected factors. For example, if the potential failure time of the base sensing slot (e.g., 9 microseconds) is assumed to be n, this can be related to the actual resource oversubscription number, and/or the channel access (LBT) failure probability, and/or the channel load status Information, etc. If the selected/reserved resource location is assumed to be T 341, and the time required for raw channel access (LBT) is assumed to be ΔT ₁ 311, this is related to the random backoff counter N. Then, the original channel access (LBT) trigger time is T-ΔT ₁ . But using the proposed scheme, the channel access (LBT) trigger time can be configured to be ΔT ₂ 312 earlier than the original channel access (LBT) trigger time, that is, T-ΔT ₁ -ΔT ₂ , where, ΔT ₂ =n×T _d , T _d is the delay time in the legacy channel access (LBT) process. After successful channel access (LBT), the device may begin the resource selection/reservation process in the initiated COT at step 340. In one embodiment, a resource oversubscription scheme is configured during this process.

Figure 4 depicts a schematic diagram of different UEs sharing resources in a COT according to an embodiment of the present invention. As an example, LBT 421 is performed at time slot N 410. Start COT 420, in which resources N+1 411, N+2 412, N+3 413, N+4 414, N+5 415 and N+6 416 are all in the COT. Resource N+7 417 outside COT 420. In some cases, there is a protection gap between the success of LBT 421 and the initial position of the selected resource (i.e. N+1 411). In one embodiment, a self-delay mechanism is implemented when a guard gap exists. In one embodiment, the self-delay mechanism is to use cyclic prefix (CP) extension to align the guard gaps when the gap is less than or equal to a predetermined value, eg, one symbol. In another embodiment, the self-delay mechanism is to use CP extension and timing advance (TA) 422 to align the guard gaps. In yet another embodiment, when the gap is greater than a predetermined value, the self-delay mechanism will perform the second LBT immediately before the SL packet is sent and received. The UE selects N+1 411 for the SL packet. In one embodiment, one or more reserved candidate resources within the COT are shared with one or more other UEs. Resources 414, 415 and 416 are shared by one or more other UEs. In one embodiment, if the Physical Sidelink Feedback Channel (PSFCH) is configured or pre-configured, the initiating device or cluster head may share the remaining free and/or used resources within the COT to the responding device for use in the COT ACK or NACK transmission. In another embodiment, the initiating device or cluster head can also share idle or unused resources in the COT to the responding device and/or other devices in the group for their data transmission. In yet another embodiment, the configuration, preconfiguration or initiating device/cluster head may provide COT specific PSFCH resource configuration.

In a novel aspect, the initiating COT is shared to the responding device and/or other devices in the group. Initiating UE 401 and other example UEs 402 and 403 operate in a license-exempt frequency band. The initiating UE 401 may also be a cluster head in a group with UE 402 and UE 403. For example, UE 402 reserves resources 413. In one embodiment, the initiating device/cluster head can share the resources reserved by other sidelink devices to the corresponding sidelink device for current and/or next packet (re)transmission. In one embodiment, during the resource selection/reservation process, the initiating device or cluster head may exclude or skip resources reserved by other sidelink devices based on one or more reserved resource sharing factors, wherein the above The reserved resource sharing factors include priority, CAPC value, destination ID, channel/transmission type on the reserved resource (eg, resource 413). These excluded resources may be shared with corresponding sidelink devices for their current and/or next TB transmission or retransmission. When LBT 421 succeeds, COT 420 is started. UE 401 performs SL resource selection. In one embodiment, the SL resource selection process within COT 420 skips reserved resources, such as resource 413. UE 401 selects resource 411. In one embodiment, UE 401 may share resources within COT 420 with one or more other UEs. UE 401 may share resources 413 and 414 with UE 402, and resources 415 and 416 with UE 403.

Figure 5 depicts an example diagram of performing LBT to initiate COT and between transmissions in accordance with an embodiment of the present invention. In one embodiment, the SL-U device can occupy the unlicensed spectrum during the subsequent COT only if the channel access (LBT) is successful. After COT is initiated, COT information indicators, including COT location, COT duration, etc., need to be sent to other devices in the group. At time 501 of time slot n, SL transceiver is triggered. Perform LBT 511. After processing time T ₁ , at time 502 , COT 520 is initiated. After LBT 511 is successful, start COT 520. In one embodiment, as shown in Figure 4, there may be a guard gap between the LBT 511 and the transmission resource, and a self-delay mechanism is used. The initiated COT can only be used by the initiating device or cluster head. Within COT 520, the COT initiating device or cluster head shall perform the sidelink resource selection/reservation process in the selection window (SW) defined by the range [n+T ₁ , n+T ₂ ], where T ₁ Depends on processing time and gap configuration between end of channel access (LBT) and start of SW. The device configures the value of T ₂ , but it should satisfy the range T _{( 2, min )} ≤ _{T 2} ≤ PDB, where T _{( 2, min )} depends on the data priority and the subcarrier spacing (SCS). In one embodiment, the COT length of the COT 520 following a successful Type 1 tunnel access (LBT) 511 may be determined by the tunnel access priority level (CAPC) of the packet being transmitted. In another embodiment, the length of the initiated COT 520 may also be configured based on the maximum remaining interval between the Type 1 channel access (LBT) success time and the PDB time.

In one embodiment, in the selection window, the sidelink device performs two steps to select resources. The first step is to exclude some candidate resources from the selection window. For example, excluded resources include resources related to half-duplex operation, resources reserved by other sidelink devices, etc. The subsequent excluded resources can be determined based on the reservation information in the first stage SCI and the relevant RSRP obtained from the sensing stage. After the first step, the second step in the selection/reservation process is to randomly select M resources from the list of available resources after the first step. For example, resources 521 and 522 are selected. In another embodiment, multiple consecutive slots (MCSt) resources are selected.

For sidelink communications, the device can reserve resources for retransmission of the current packet and/or (re)transmission of the next packet. This principle also applies to SL-U devices. For SL-U devices, one example is that resources for retransmission of the current packet and/or initial transmission of the next packet and/or retransmission of the next packet can be selected/reserved within the current COT. For this case, the device should perform a channel access (LBT) process, e.g., LBT 512, before accessing the selected/reserved resources. The channel access (LBT) type of the LBT 512 can be indicated from Type 1 channel access (LBT), Type 2A channel access (LBT), Type 2B channel access (LBT) and Type 2C channel access (LBT)/ configuration. The channel access type (LBT) can refer to the NR-U specification in 3GPP.

In one embodiment, if the channel access (LBT) is used to initiate the COT or the channel access (LBT) is performed outside the COT, e.g., LBT 511, then the type 1 channel access (LBT) is indicated/configured ). If the LBT is performed within an originating/shared COT, for example, LBT 512, the LBT type can be configured as Type 1 LBT, Type 2A LBT, Type Type 2B channel access (LBT) and Type 2C channel access (LBT). The channel access (LBT) type can be indicated/configured by the COT initiating device/cluster head, or can be determined by the COT sharing device based on the gap 530 between two consecutive transmissions.

Figure 6 depicts a schematic diagram of uplink resource selection on a license-exempt frequency band with dynamic configuration for LBT process and SL selection process according to an embodiment of the present invention. In a novel aspect, channel access, such as LBT, is triggered for SL transceiver in license-exempt bands. At step 601, LBT is triggered. Non-periodic data 611 triggers LBT. Indicates/configures the random backoff counter generation time and LBT triggering time after and/or when the packet is ready until the Packet Delay Budget (PDB) is reached. The periodic data 612 may trigger LBT, wherein the LBT process is executed before the SL packet is ready to be sent, and wherein the trigger time is (pre)configured or dynamically indicated based on one or more trigger factors, wherein the one or more trigger factors include LBT process failure probability, channel load status information, CAPC availability and channel congestion control information.

When the sidelink device is no longer transmitting, it will continue to sense the unlicensed spectrum resources to collect sensing information and further identify available candidate resources. In step 602, the UE collects sensing information. Sensing information for the unlicensed spectrum includes first-level sidelink channel information (SCI) 621 and reference signal received power (RSRP) 622 from other sidelink devices. Specifically, during the sidelink sensing process, sidelink devices decode first-level SCIs from other sidelink devices on unlicensed spectrum. In this way, sidelink devices can obtain resource configuration and resource reservation information of other devices. Sidelink devices also measure the sidelink RSRP of transmissions from other devices, which can be further used to assist with channel access (LBT) and sidelink selection/reservation processes. The Information Element (IE) sl-RS-ForSensing from higher layers indicates whether to measure the RSRP of the Physical Sidelink Control Channel (PSCCH) or the RSRP of the Physical Sidelink Shared Channel (PSSCH). Then, if resource (re)selection/reservation is triggered at time slot n, the sidelink device should first collect sensing information within a certain period [nT ₀ , nT _{( proc, 0 )} ], where T ₀ is an integer defined in the number of slots and is equal to x milliseconds (e.g. 1100 milliseconds or 100 milliseconds), which is determined by the upper layer IE sl-SensingWindow . Furthermore, T _{( proc,0 )} is the time required to complete the sensing process. In one embodiment, sensing information including 621 and 622 may be used to assist the tunnel access (LBT) process 603 . Specifically, in the sensing phase, after decoding the first phase SCI, time/frequency resource configuration and resource reservation information for other sidelink transmissions can be obtained. Then, the linear average of the reference signal power P _t1 over a specific bandwidth can be calculated, that is, the RSRP of the reference signal can be obtained in the sidelink sensing stage. Next, the total power P _t2 over the entire allocated bandwidth, that is, RSSI, can be approximately calculated as P _t2 =P _t1 ×N _RE +P _n +P _i , where P _n and _Pi represent noise and interference respectively. The power of N _RE is the number of resource elements indicated in the first stage SCI. Next, if P _t1 is greater than the threshold Th ₁ , then P _t2 will be greater than the corresponding threshold Th ₂ . Assuming that the channel access (LBT) energy detection/sensing threshold is Th, if Th ₂ ≥ Th, then there is no need to perform channel access (LBT) at least in the current time slot, and the device should wait for the next time slot, and then use the next The sensing information of a time slot is channel accessed (LBT) again. In some cases, sidelink devices can derive LBT results, which can be used to avoid performing LBT, further reducing the power consumption of the device.

In a novel aspect, configuration parameters of LBT 603, such as LBT trigger time, backoff counter N, and resource gap 631, are dynamically configured. In one embodiment, the LBT trigger time at which execution of the LBT process begins is dynamically configured. In another embodiment, the resource gap between the potential success of the LBT process and the starting location of the candidate resources is dynamically configured based on one or more factors, including channel status, Tier 1 priority, and oversubscribed resource size. In one embodiment, the type of LBT 632 is determined dynamically. In one embodiment, LBT 632a is executed outside of the COT or when the COT is initialized. In another embodiment, LBT 632b is executed within a COT or while sharing a COT. In one embodiment 633, the self-delay mechanism is implemented in the protection gap between the success of the LBT process and the transmission and reception of the SL packet.

In one embodiment 633a, a self-delay mechanism is implemented and a short second LBT is performed immediately before packet transmission and reception. In another embodiment 633b, guard gaps are aligned using cyclic prefix (CP) extension (CPE) or CPE and timing advance (TA). Specifically, when the first LBT is successful, the UE determines whether the packet is ready in step 633g. If the packet is not ready, then embodiment 633a is used when performing self-delay; and when the packet is ready, the second short LBT immediately precedes the SL packet transmission and reception. If step 633g determines yes, which means the packet is ready when the first LBT succeeds, the UE determines the length of the guard gap, which is the gap between the LBT success and the transmission and reception of the SL packet. If at step 633h, the UE determines that the protection gap is less than or equal to the predefined threshold, the UE performs embodiment 633b, which is CPE or CPE&TA to align the protection gaps. If step 633h determines to be negative, which means that the protection gap is greater than the predefined threshold, the UE performs embodiment 633a and performs self-delay in the short second LBT immediately before the SL packet is transmitted and received.

In one embodiment, SL resource selection 604 has dynamically configured parameters. In one embodiment 641, the candidate resource selected by the SL resource selection process has an oversubscribed resource size that is greater than the resource size required for SL data transmission and reception. The oversubscription resource size is dynamically configured based on one or more oversubscription factors, which include channel status, layer 1 priority, CAPC value, channel/transmission type, LBT failure probability, channel load status information, and channel congestion control information. and the gap between the potential success of the LBT process and the starting position of the candidate resource.

In one embodiment 605, after the LBT process is successful, a COT is initiated and one or more reserved candidate resources in the COT are shared with one or more other UEs. In one embodiment 651, the SL selection process within the COT first excludes one or more resources. In one embodiment, other UEs reserve the excluded resources. The originating UE may share these excluded resources with other UEs. In one embodiment 652, a UE shares free or used resources with other UEs.

Figure 7 depicts an exemplary flow chart of sidelink resource selection in a license-exempt frequency band according to an embodiment of the present invention. In step 701, the UE performs a listen-before-talk (LBT, also known as pre-transmit search) process to prepare for UE sidelink (SL) transceiver in the license-exempt frequency band of the wireless network, where the LBT process determines and Channel selection for other coexisting wireless systems in license-exempt bands. In step 702, the UE performs a SL resource selection process to select candidate resources in the license-exempt frequency band for SL transceiver of the UE. In step 703, when both the SL resource selection process and the LBT process are successful, the UE sends and receives SL packets on the selected candidate resources.

Although the invention has been described in terms of preferred embodiments in an exemplary manner, it will be understood that the invention is not limited thereto. Those skilled in the art can still make various changes and modifications without departing from the scope and spirit of the invention. Accordingly, the scope of the invention should be defined and protected by the appended claims and their equivalents.

100: Wireless network; 101, 102, 103: Base station; 111, 112, 113, 114, 115, 116, 117, 118, 119, 401, 402, 403: UE; 121: Memory; 122: Processor ; 123: RF transceiver; 125: Antenna; 126: Program instructions and data; 191: LBT module; 192: Select module; 193: Transceiver controller; 194: Dynamic configuration module; 151, 152, 161, 162 ,163,164,165,166,167,171,172,173,174,175,176,177,178,181,182,183,184,201,210,220,240,300,320,330,340 , 601, 602, 633h, 633g, 701, 702, 703: steps; 231: cycle; 232: protection gap; 241, 251, 252, 253, 411, 412, 413, 414, 415, 416, 417, 521, 522: Resources; 311: ΔT ₁ ; 312: ΔT ₂ ; 341: T; 421, 511, 512, 603, 632a, 632b: LBT; 422: CP extension and TA; 420, 520: COT; 501, 502: time ; 530: Gap; 604: SL resource selection; 611: Aperiodic data; 612: Periodic data; 621: SCI; 622: RSRP; 631: LBT trigger time, backoff counter N and resource gap; 632: LBT type; 633, 641, 605, 651, 652, 633a, 633b: Examples.

The present invention can be more fully understood by reading the following detailed description with reference to the accompanying drawings. It should be understood that the drawings are not drawn to scale in accordance with standard practice in the industry. Indeed, the dimensions of elements in the drawings are allowed to be exaggerated or reduced for clarity of illustration. This means that many specific details, relationships and methods are disclosed in order to provide a complete understanding of the invention. Figure 1A is a schematic system diagram of an example wireless network for sidelink data communication with other coexisting RATs in a license-exempt frequency band in accordance with an embodiment of the present invention. Figure 1B depicts an exemplary flow diagram for sidelink communications over unlicensed spectrum using LBT sensing and selection, in accordance with an embodiment of the present invention. Figure 2 depicts a schematic diagram of aperiodic data transmission in a license-exempt frequency band with dynamic configuration parameters according to an embodiment of the present invention. Figure 3 depicts a schematic diagram of periodic data transmission in a license-exempt frequency band with dynamic configuration parameters according to an embodiment of the present invention. Figure 4 depicts a schematic diagram of different UEs sharing resources in a COT according to an embodiment of the present invention. Figure 5 depicts an example diagram of performing LBT to initiate COT and between transmissions in accordance with an embodiment of the present invention. Figure 6 depicts a schematic diagram of uplink resource selection on a license-exempt frequency band with dynamic configuration for LBT process and SL selection process according to an embodiment of the present invention. Figure 7 depicts an exemplary flow chart of sidelink resource selection in a license-exempt frequency band according to an embodiment of the present invention.

701, 702, 703: steps

Claims (15)

A sidelink communication method, including: Execute a listen-before-talk process through a user equipment to prepare for user equipment sidelink transmission and reception in a license-exempt frequency band of a wireless network, wherein the listen-before-talk process is determined to be consistent with the license-exempt frequency band. Channel selection for other coexisting wireless systems in the band; Execute a sidelink resource selection process to select candidate resources in the license-exempt frequency band for the sidelink transceiver of the user equipment; and When both the sidelink resource selection process and the listen-before-talk process are successful, sidelink packets are sent and received on the selected candidate resource. The sidelink communication method as claimed in claim 1, wherein the listen-before-talk process is executed before the sidelink resource selection process. The sidelink communication method as described in claim 1, wherein the listen-before-talk triggering time to start executing the listen-before-talk process is dynamically configured. The sidelink communication method as described in claim 3, wherein the listen-before-talk process is executed before the side-link packet is ready, and wherein the listen-before-talk trigger time is pre-configured or based on a Or multiple trigger factors dynamically indicate the listen-before-talk trigger time, wherein the trigger factors include the failure probability of the listen-before-talk process, channel load status information, channel access priority availability, and channel congestion control information. The sidelink communication method as described in claim 1, wherein resources between the potential success of the listen-before-talk process and the starting position of the candidate resource are pre-configured or dynamically indicated based on one or a plurality of resource slot factors. Slot, wherein the one or more resource slot factors include channel status, layer 1 priority, channel access priority value, channel/transport type, and oversubscribed resource size. The sidelink communication method as claimed in claim 1, wherein the candidate resource selected by the sidelink resource selection process has an oversubscribed resource size that is larger than the resource size required for the sidelink data transmission and reception. The sidelink communication method as described in claim 6, wherein the oversubscription resource size is pre-configured or dynamically indicated based on one or a plurality of oversubscription factors, wherein the one or a plurality of oversubscription factors include channel status, layer 1 Priority order, listen-before-talk failure probability, channel load status information, channel congestion control information, and the gap between the potential success of the listen-before-talk process and the starting position of the candidate resource. The sidelink communication method as claimed in claim 1, wherein a self-delay mechanism is executed during the protection gap between the success of the listen-before-talk process and the sending and receiving of the sidelink packet. The sidelink communication method as described in claim 8, wherein when the listen-before-talk process is successful, the protection gap is greater than the preconfigured threshold and the sidelink packet is ready, the self-delay mechanism is executed, and Wherein, when the sidelink packet is ready, a second listen-before-talk process is executed before the sending and receiving of the sidelink packet. The sidelink communication method as described in claim 8, wherein when the listen-before-talk process is successful, the protection gap is greater than the preconfigured threshold and the sidelink packet is ready, the self-delay mechanism is executed, and Wherein, when the sidelink packet is ready, a second listen-before-talk process is executed before the sending and receiving of the sidelink packet. The sidelink communication method as described in claim 1, wherein when the protection gap is less than or equal to the preconfigured threshold, the listen-before-talk process is successful and the sidelink packet is ready, cyclic prefix extension or Cyclic prefix extension and timing advance align the transmission and reception of the side link packet with the success boundary of the listen-before-talk process or occupy the success position of the transmission and reception of the side-link packet and the listen-before-talk process. protective gap between them. The sidelink communication method as described in claim 1, wherein after the listen-before-talk process is successful, the channel occupancy time is started. The sidelink communication method as described in claim 12, wherein one or more reserved candidate resources within the channel occupation time are shared with one or more other users based on one or more reserved resource sharing factors. or equipment, wherein the one or plurality of reserved resource sharing factors include priority order, channel access priority value, destination identifier, propagation type and channel/transmission type on the reserved resource. The sidelink communication method as described in claim 12, wherein, based on predetermined rules, the sidelink resource selection process excludes one or a plurality of candidate resources within the channel occupation time. A user equipment for sidelink communications, including: a transceiver for transmitting and receiving radio frequency signals in a wireless network; A listen-before-talk module is used to execute a listen-before-talk process to prepare for user equipment side link transceiver in the license-exempt frequency band of the wireless network, wherein the listen-before-talk process is determined to be consistent with the license-exempt frequency band. Channel selection for other coexisting wireless systems in the available frequency band; a selection module for executing a sidelink resource selection process, wherein the sidelink resource selection process selects candidate resources in the unlicensed frequency band for the sidelink transceiver of the user equipment; and A transceiver controller, configured to transmit and receive sidelink packets on the selected candidate resource when both the sidelink resource selection process and the listen-before-talk process are successful.