Terminal device, and method executed by a first terminal device

Abstract

Embodiments of the present disclosure relate to a method, an apparatus, and a computer-readable medium for sidelink communication. A method implemented for sidelink communication in a first terminal device includes selecting the first candidate resource for the sidelink communication according to a determination that a first candidate resource immediately preceding a second resource is available within a candidate resource set. The second resource is reserved by a second terminal device. The method further includes obtaining a COT period before executing the sidelink communication on the first candidate resource. The method further includes transmitting first information regarding the COT period to the second terminal device.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to the field of telecommunications, and more particularly, to methods, apparatuses, and computer-readable media for sidelink communication.

Background Art

[0002] Sidelink in unlicensed spectrum or band (SL-U) is being studied in the Release 18 sidelink evolution work item of the 3rd Generation Partnership Project (3GPP). The SL-U approach should be based on New Radio (NR) sidelink and NR-U.

[0003] In sidelink communication, there are two resource allocation modes. In the first mode (hereinafter also referred to as NR sidelink mode 1 or mode 1), one terminal device can perform sidelink communication with another terminal device using resources allocated by a network device. In the second mode (hereinafter also referred to as NR sidelink mode 2 or mode 2), one terminal device can perform sidelink communication with another terminal device using resources autonomously selected within a resource pool by the one terminal device.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, exemplary embodiments of the present disclosure provide methods, apparatuses, and computer-readable media for sidelink communication.

Means for Solving the Problems

[0005] In a first aspect, a method implemented for sidelink communication in a first terminal device is provided. The method includes selecting the first candidate resource for the sidelink communication according to a determination that a first candidate resource immediately preceding a second resource is available within a candidate resource set. The second resource is reserved by a second terminal device. The method further includes obtaining a Channel Occupancy Time (COT) period before performing sidelink communication on the first candidate resource. The method further includes transmitting first information regarding the COT period to the second terminal device.

[0006] In a second aspect, a method for sidelink communication is provided. The method includes, at a first terminal device, performing a transmission on a first resource, and performing a retransmission associated with the transmission for the second terminal device on a second resource within the COT period according to a determination that an affirmative response to the transmission has been received from the second terminal device or a negative response to the transmission has not been received.

[0007] In a third aspect, a terminal device is provided. The terminal device includes a processor and a memory storing instructions. The memory and the instructions are configured to cause the processor to execute the method according to the first aspect in the terminal device.

[0008] In a fourth aspect, a terminal device is provided. The terminal device includes a processor and a memory storing instructions. The memory and the instructions are configured to cause the processor to execute the method according to the second aspect in the terminal device.

[0009] In a fifth aspect, a computer-readable medium storing instructions is provided. When the instructions are executed on at least one processor of a device, the device is caused to execute the method according to the first aspect.

[0010] In a sixth aspect, a computer-readable medium storing instructions is provided. When the instructions are executed on at least one processor of a device, the device is caused to execute the method according to the second aspect.

[0011] It should be understood that the summary section of the invention is not intended to identify important or essential features of embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure should be readily understood from the following description.

Brief Description of the Drawings

[0012] By further describing some embodiments of the present disclosure in the accompanying drawings in more detail, the above and other objects, features, and advantages of the present disclosure will become more apparent.

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[0022] In the figure, the same or similar reference numerals represent the same or similar elements.

DETAILED DESCRIPTION OF THE INVENTION

[0023] Here, the principles of the present disclosure will be explained with reference to some exemplary embodiments. It should be understood that these embodiments are described for illustrative purposes only and are intended to assist those skilled in the art in understanding and implementing the present disclosure, without suggesting any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in various ways different from the methods described below.

[0024] In the following description and claims, unless otherwise defined, all technical and scientific terms used herein shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0025] As used herein, the term "terminal device" refers to any device having wireless or wired communication capabilities. Examples of terminal devices include user equipment (UE), personal computers, desktops, mobile phones, cellular phones, smartphones, personal digital assistants (PDAs), portable computers, tablets, wearable devices, Internet of Things (IoT) devices, Ultra-reliable and Low Latency Communications (URLLC) devices, Internet of Everything (IoE) devices, machine type communication (MTC) devices, vehicle-mounted devices for vehicle-to-everything (V2X) communication (where X means pedestrian, vehicle, or infrastructure / network), Integrated Access and Backhaul (IAB), Small Data Transmission (SDT), mobility, Multicast and Broadcast Services (MBS), positioning, dynamic / flexible duplexing in commercial networks, devices for reduced capability (RedCap), devices of spacecraft or aircraft in non-terrestrial networks (NTN) including High Altitude Platforms (HAP) and satellites that include Unmanned Aircraft Systems (UAS), Extended Reality (XR) devices including different types of reality such as Augmented Reality (AR), Mixed Reality (MR), Virtual Reality (VR), unmanned aerial vehicles (UAVs), which are aircraft generally known as drones and do not require a human pilot, high speed trains (HST: high speedDevices on a train , imaging devices such as digital cameras, sensors, gaming devices, music storage / playback devices, or Internet devices that enable wireless / wired Internet access and browsing, etc. may be mentioned, but are not limited thereto. The "terminal device" can further have a multicast / broadcast function and support public safety, mission critical, V2X applications, transparent IPv4 / IPv6 multicast delivery, IPTV, smart TV, wireless services, wireless software delivery, group communication, and IoT applications. Also, one or more subscriber identity modules (SIMs), known as multi-SIM, may be incorporated. The term "terminal device" may be used interchangeably with UE, mobile station, subscriber equipment, mobile terminal, user terminal, or wireless device.

[0026] The term "network device" refers to a device that can provide or host a cell or coverage with which a terminal device can communicate. Examples of network devices include, but are not limited to, Node B (NodeB or NB), Evolved NodeB (eNodeB or eNB), Next Generation NodeB (gNB), transmission reception point (TRP), remote radio unit (RRU), radio head (RH), remote radio head (RRH), IAB node, femto node, low-power nodes such as pico nodes, reconfigurable intelligent surface (RIS), network control repeater, etc.

[0027] The terminal device or network device may have the ability of artificial intelligence (AI) or machine learning. Generally, it contains a trained model from a large number of data collected for a specific function and can be used to predict some information.

[0028] The terminal device or the network device may operate, for example, on several frequency ranges such as FR1 (410 MHz to 7125 MHz), FR2 (24.25 GHz to 71 GHz), frequency bands greater than 100 GHz, and terahertz (THz). Furthermore, it can operate on licensed / unlicensed / shared spectrum. The terminal device may have two or more connections with the network device under a multi-radio dual connectivity (MR-DC) application scenario. The terminal device or the network device can operate in full-duplex, flexible-duplex, cross-split duplex modes.

[0029] The network device may have functions of network energy saving, self-organizing networks (SON) / minimization of drive test (MDT). The terminal may have a power-saving function.

[0030] Embodiments of the present disclosure may be implemented in test equipment such as, for example, a signal generator, a signal analyzer, a spectrum analyzer, a network analyzer, a test terminal device, a test network device, a channel emulator.

[0031] Embodiments of the present disclosure may be executed in accordance with any generation of communication protocols known currently or developed in the future. Examples of communication protocols include, but are not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the fifth generation (5G) communication protocol, 5.5G, 5G-Advanced network, or the sixth generation (6G) network.

[0032] As used herein, the singular forms "a / an" and "the" include the plural forms as well, unless the context clearly dictates otherwise. The terms "comprising" and variations thereof should be understood as open-ended terms meaning "including, but not limited to". The term "based on" should be understood as "at least partially based on". The terms "some embodiments" and "embodiments" should be understood as "at least some embodiments". The term "another embodiment" should be understood as "at least one other embodiment". Terms such as "first", "second", etc. may refer to different or the same objects. Other explicit and implicit definitions may be included below.

[0033] In some examples, a value, procedure, or device is referred to as "optimal", "lowest", "highest", "minimum", "maximum", etc. Such descriptions are intended to indicate that a selection is possible from among multiple functional alternatives being used, and it will be understood that such a selection need not be better, smaller, higher, or more preferable than other selections.

[0034] FIG. 1 is a schematic diagram of an exemplary communication network 100 capable of implementing embodiments of the present disclosure. As shown in FIG. 1, the communication network 100 may include a first terminal device 110, a second terminal device 120, a third terminal device 130, and network devices 140 and 150. The network devices 140 and 150 may communicate with the first terminal device 110, the second terminal device 120, and the third terminal device 130 via respective wireless communication channels.

[0035] In some embodiments, the network device 140 may be a gNB in NR, and the network device 150 may be an eNB in a Long Term Evolution (LTE) system.

[0036] It should be understood that the number of devices in FIG. 1 is provided for illustrative purposes and does not imply any limitation to the present disclosure. The communication network 100 may include any suitable number of network devices and / or terminal devices suitable for implementing embodiments of the present disclosure.

[0037] Communications in the communication network 100 may comply with any suitable standard including, but not limited to, Global System for Mobile Communications (GSM), LTE, LTE-Evolution, LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), GSM EDGE Radio Access Network (GERAN), Machine Type Communication (MTC), etc. Further, the communications may be performed according to any generation of communication protocol known currently or developed in the future. Examples of communication protocols include, but are not limited to, the first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G) communication protocols.

[0038] In some embodiments, the communication in communication network 100 may include sidelink communication. Sidelink communication is direct wireless radio communication between two or more terminal devices, for example, between two or more of the first terminal device 110, the second terminal device 120, and the third terminal device 130. In this type of communication, two or more terminal devices that are geographically close to each other can communicate directly without going through network devices 140 or 150, or the core network. Therefore, data transmission in sidelink communication is different from typical cellular network communication where a terminal device transmits data to (i.e., uplink transmission) or receives data from (i.e., downlink transmission) network devices 140 or 150. As shown in FIG. 1, in sidelink communication, data is directly transmitted from a source terminal device (e.g., the first terminal device 110) to a target terminal device (e.g., the second terminal device 120) via an integrated air interface, for example, a PC5 interface (i.e., sidelink transmission).

[0039] Sidelink communication can provide several advantages, including reducing the data transmission load on the core network, system resource consumption, transmission power consumption, and network operation cost, saving wireless spectrum resources, and improving the spectrum efficiency of the cellular wireless communication system.

[0040] In a sidelink communication system, sidelink resources are used to transmit information between terminal devices. Depending on the application scenario, type of service, etc., sidelink communication methods include, but are not limited to, device - to - device (D2D) communication, vehicle - to - everything (V2X) communication, etc.

[0041] With V2X communication, a vehicle can communicate with other vehicles (i.e., vehicle-to-vehicle (V2V) communication), with infrastructure (i.e., vehicle-to-infrastructure (V2I) communication), with a wireless network (i.e., vehicle-to-network (V2N) communication), with pedestrians (i.e., vehicle-to-pedestrian (V2P) communication), and even with the owner's home (i.e., vehicle-to-home (V2H)). Examples of infrastructure include roadside units such as traffic lights and toll booths. V2X communication can be used in a wide range of scenarios such as accident prevention, safety, convenience, traffic efficiency, and accident-free driving, and ultimately leads to autonomous and self-driving vehicles.

[0042] In the case of sidelink communication, the terminal device transmits or receives signals using resources within the sidelink resource pool. The sidelink resource pool includes resources in the time domain and frequency domain, and these resources are either dedicated resources for sidelink communication or shared by sidelink communication and the cellular link.

[0043] A sidelink resource pool may include a plurality of slots and resource blocks (RBs), and all or part of the symbols within a slot can be used for sidelink transmission. Within the resource pool, among all the symbols configured for sidelink within each slot, the first symbol (i.e., the starting symbol) is used as an automatic gain control (AGC) symbol, and the last symbol is used as a guard period (GP) symbol. The AGC symbol and the GP symbol may be considered as fixed overhead within the sidelink resource. In the description of the following embodiments, as shown in FIG. 2, the AGC symbol and the GP symbol are included in the sidelink symbols indicated by the sidelink channel resource configuration. The AGC symbol conveys redundant sidelink information, and the GP symbol is not used for conveying sidelink information.

[0044] The first terminal device 110, the second terminal device 120, and the third terminal device 130 may transmit sidelink signaling or information using a sidelink channel. The sidelink channel includes at least one of a physical sidelink control channel (PSCCH) resource used to carry sidelink control information (SCI), a physical sidelink shared channel (PSSCH) resource used to carry sidelink data service information, a physical sidelink feedback channel (PSFCH) resource used to carry sidelink hybrid automatic repeat request (HARQ) feedback information, a physical sidelink broadcast channel (PSBCH) resource used to carry sidelink broadcast information, and a physical sidelink discovery channel (PSDCH) resource used to carry a sidelink discovery signal. Hereinafter, the PSFCH resource is also referred to as a feedback channel resource or a HARQ feedback opportunity.

[0045] Within the resource pool, the PSSCH resource includes all symbols in a slot configured as a sidelink available symbol and one or more subchannels in the frequency domain, where each subchannel includes an integer number of consecutive RBs. The number m of RBs included in one subchannel is also referred to as the subchannel size. Each slot included in the resource pool includes a plurality of available sidelink symbols, and the PSSCH resource is located within the time domain from the first available sidelink symbol to all available symbols in this slot. In the frequency domain, the resource pool includes a plurality of RBs. According to the subchannel size m, starting from the first RB in the resource pool, every m RBs are divided into one subchannel, and each PSSCH channel resource is located on one or more subchannels. When one of the first terminal device 110, the second terminal device 120, and the third terminal device 130 uses the PSSCH resource to transmit sidelink information, it may use one or more subchannels to carry the corresponding data information. The PSCCH resource includes t symbols in the time domain and l RBs in the frequency domain. As shown in FIG. 3, each PSCCH channel resource is located at t consecutive symbols starting from the first symbol among the available symbols in the time domain, and is located at the position of l consecutive RBs starting from the first RB among the corresponding subchannels in the frequency domain.

[0046] The terminal device may select a resource from its transmission resource pool for sidelink signal transmission by executing sensing and resource selection procedures. Fig. 4 shows an example of a sensing window and a selection window in the sensing and resource selection procedures. As shown in the figure, within slot #n, the sensing and resource selection procedures may be triggered. During this procedure, the first terminal device 110 attempts to sense resources within the sensing window in the resource pool and decode the SCI 410 received from the second terminal device 120 and the SCI 420 received from the third terminal device 130. The SCI 410 may include control information indicating candidate resource 412 reserved by the second terminal device 120. The SCI 420 may include control information indicating candidate resource 422 reserved by the third terminal device 130.

[0047] Then, based on the measurement results and the control information obtained from the SCI 410 and 420, the first terminal device may exclude candidate resources 412 and 422 from the initial candidate resource set within the resource selection window. Therefore, the first terminal device 110 may determine the remaining candidate resources within the resource selection window as the candidate resource set and report this set to the upper layer of the first terminal device 110. Hereinafter, a candidate resource set from which at least one reserved resource has been excluded is also referred to as a sensing result.

[0048] Upon receiving the candidate resource set, the upper layer of the first terminal device 110 may select at least one candidate resource from the candidate resource set for sidelink communication.

[0049] When the upper layer of the first terminal device 110 randomly selects a candidate resource from the candidate resource set, a pattern of consecutive resources for the first terminal device 110, the second terminal device 120, and / or the third terminal device 130 cannot be realized.

[0050] Embodiments of the present disclosure provide a solution for sidelink communication to solve the above problems and one or more other potential problems. According to this solution, when a first terminal device determines that a first candidate resource immediately preceding a second resource is available within a candidate resource set, the first terminal device selects the first candidate resource for sidelink communication. The second resource is reserved by a second terminal device. Then, before performing sidelink communication on the first candidate resource, the first terminal device acquires a Channel Occupancy Time (COT) period. Next, the first terminal device transmits first information regarding the COT period to the second terminal device. This solution can make the resources for sidelink terminal devices continuous within the COT period.

[0051] Hereinafter, with reference to FIGS. 5 to 8, the principle of the present disclosure will be described. FIG. 5 is a flowchart of an exemplary method 500 according to some embodiments of the present disclosure. In some embodiments, the method 500 can be implemented in one of the terminal devices, for example, the first terminal device 110, the second terminal device 120, and the third terminal device 130 as shown in FIG. 1. For the sake of explanation, with reference to FIG. 1, without loss of generality, the method 500 executed by the first terminal device 110 will be described.

[0052] In block 510, the first terminal device 110 determines whether a first candidate resource immediately preceding a second resource is available within a candidate resource set. The second resource is reserved by the second terminal device 120.

[0053] If the first candidate resource immediately preceding the second resource is available within the candidate resource set, the first terminal device 110 selects the first candidate resource for sidelink communication in block 520.

[0054] In block 530, the first terminal device 110 acquires a COT period before performing sidelink communication on the first candidate resource.

[0055] In some embodiments, the first terminal device 110 may acquire the COT period by performing a channel access procedure. The channel access procedure is also referred to as a Listen Before Talk (LBT) procedure. The LBT procedure may be a type 1 LBT procedure, a type 2A LBT procedure, a type 2B LBT procedure, or a type 2C LBT procedure.

[0056] In block 540, the first terminal device 110 transmits first information regarding the COT period to the second terminal device 120.

[0057] Method 500 can make the resources for the sidelink terminal device be continuous within the COT period.

[0058] In some embodiments, if the first candidate resource immediately before the second resource is unavailable within the candidate resource set, the first terminal device 110 may randomly select a candidate resource within the candidate resource set for sidelink communication. In other words, if the first terminal device 110 has a sensing result, the first terminal device 110 may select the first candidate resource immediately before the second resource with the highest priority and select the other candidate resources within the candidate resource set with the second highest priority.

[0059] Hereinafter, with reference to FIGS. 6A and 6B, some examples of resource selection will be described. FIG. 6A shows an example of resource selection according to some embodiments of the present disclosure. In this example, candidate resource 610 immediately before reserved resource 620 is available within candidate resource set 600, and candidate resource 612 immediately before reserved resource 622 is available within candidate resource set 600. Therefore, the first terminal device 110 may select at least one of candidate resources 610 and 612 for sidelink communication.

[0060] When the first terminal device 110 selects candidate resource 610, the first terminal device 110 may obtain a COT period before performing sidelink communication on candidate resource 610. Next, the first terminal device 110 may transmit information regarding the COT period to the second terminal device 120. Thus, consecutive resources 612 and 620 within the COT period may be used by the first terminal device 110 and the second terminal device 120.

[0061] FIG. 6B shows another example of resource selection according to some embodiments of the present disclosure. The example of FIG. 6B is similar to the example in FIG. 4. The example of FIG. 6B is different from the example in FIG. 4 in that the first terminal device 110 does not randomly select a candidate resource from a candidate resource set excluding candidate resources 412 and 422. Instead, the first terminal device 110 selects at least one of candidate resources 630 and 632 for sidelink communication. For example, the first terminal device 110 may select candidate resource 630 for transmission and select candidate resource 632 for retransmission associated with the transmission. The transmission on candidate resource 630 may be an initial transmission or a retransmission. If the transmission on candidate resource 630 is a retransmission, the retransmission on candidate resource 632 is the next retransmission associated with the retransmission on candidate resource 630.

[0062] Before executing transmission on the candidate resource 630, the first terminal device 110 may acquire the COT period 640. Next, the first terminal device 110 may transmit information regarding the COT period 640 to at least one of the second terminal device 120 and the third terminal device 130. Within the shared COT period 640, the second terminal device 120 and the third terminal device 130 may execute their respective sidelink transmissions by executing a short Listen Before Talk (LBT) procedure (e.g., a type 2 LBT procedure). Thus, the consecutive resources 630, 412, 632, and 422 within the COT period 640 may be used by the first terminal device 110, the second terminal device 120, and the third terminal device 130.

[0063] In some embodiments, additionally, the first terminal device 110 may receive second information regarding a preferred resource set for sidelink communication from the third terminal device 130. In such an embodiment, the first terminal device 110 may further determine whether the first candidate resource belongs to the preferred resource set. If the first candidate resource belongs to the preferred resource set, the first terminal device 110 selects the first candidate resource.

[0064] In other words, when the first terminal device 110 has a sensing result and receives a preferred resource set, the first terminal device 110 may select, with the highest priority, a candidate resource that is immediately before the reserved resource and belongs to the preferred resource set. This will be described with reference to FIG. 7.

[0065] FIG. 7 shows an example of resource selection according to some embodiments of the present disclosure. In this example, a candidate resource 710 that is immediately before the reserved resource 720 and belongs to the preferred resource set is available within the candidate resource set 700. Thus, the first terminal device 110 may select the candidate resource 710 with the highest priority for sidelink communication.

[0066] In an embodiment where the first terminal device 110 has sensing results and receives a preferred resource set, if a first candidate resource that is in front of the second resource and belongs to the preferred resource set is unavailable, the first terminal device 110 may select a third resource or a fourth resource within the candidate resource set for sidelink communication. The third candidate resource belongs to the preferred resource set, and the fourth resource is in front of the second resource.

[0067] In an embodiment where a first candidate resource that is in front of the second resource and belongs to the preferred resource set is unavailable, the first terminal device 110 may determine whether a third candidate resource that belongs to the preferred resource set is available. If the third candidate resource is available, the first terminal device 110 may select the third resource. On the other hand, if the third candidate resource is unavailable, the first terminal device 110 may select the fourth resource that is in front of the second resource. In such an embodiment, the first terminal device 110 may select the third resource that belongs to the preferred resource set with the second highest priority, and select the fourth resource that is in front of the second resource with the third highest priority. This will also be described with reference to FIG. 7.

[0068] As shown in FIG. 7, the candidate resource 712 is in front of the reserved resource 722 but does not belong to the preferred resource set. The candidate resource 714 belongs to the preferred resource set but is not in front of the reserved resource 722. In some embodiments, the first terminal device 110 may select the candidate resource 714 with the second highest priority and select the candidate resource 712 with the third highest priority. Since the candidate resource 714 belongs to the preferred resource set, selecting the candidate resource 714 with the second highest priority can increase the success probability of sidelink transmission.

[0069] As an alternative, in an embodiment where a first candidate resource belonging to a preferred resource set immediately before a second resource is unavailable, the first terminal device 110 may determine whether a fourth candidate resource immediately before the second resource is available. If the fourth candidate resource is available, the first terminal device 110 may select the fourth resource. On the other hand, if the fourth candidate resource is unavailable, the first terminal device 110 may select a third resource belonging to the preferred resource set. In such an embodiment, the first terminal device 110 may select the third resource belonging to the preferred resource set with the second highest priority and select the fourth resource immediately before the second resource with the third highest priority. If none of the first candidate resource, the third candidate resource, and the fourth candidate resource are available, the first terminal device 110 may randomly select at least one other candidate resource within the candidate resource set. This will also be described with reference to FIG. 7.

[0070] As shown in FIG. 7, in some embodiments, the first terminal device 110 may select the candidate resource 712 with the second highest priority and select the candidate resource 714 with the third highest priority. Since the candidate resource 712 is immediately before the reserved resource 722, the consecutive resources 712 and 722 within the COT period may be used by the first terminal device 110 and the second terminal device 120.

[0071] In some embodiments, additionally, the first terminal device 110 may receive, from a fourth terminal device, third information regarding a non-preferred resource set for sidelink communication. In such an embodiment, the first terminal device 110 may further determine whether the first candidate resource belongs to the non-preferred resource set. If the first candidate resource does not belong to the non-preferred resource set, the first terminal device 110 selects the first candidate resource.

[0072] In other words, when the first terminal device 110 has sensing results and receives an unfavorable resource set, the first terminal device 110 may select, with the highest priority, candidate resources that are immediately before the reserved resources and do not belong to the unfavorable resource set. When a first candidate resource that is immediately before the reserved resources and does not belong to the unfavorable resource set is available, the first terminal device 110 may randomly select at least one other candidate resource within the candidate resource set by excluding the unfavorable resource set with the second highest priority. This will be described with reference to FIG. 8.

[0073] FIG. 8 shows an example of resource selection according to some embodiments of the present disclosure. In this example, a candidate resource 810 that is immediately before the reserved resource 820 and does not belong to the unfavorable resource set is available within the candidate resource set 800. Therefore, the first terminal device 110 may select the candidate resource 810 for sidelink communication with the highest priority.

[0074] Similar to the examples of FIGS. 6A and 6B, in the examples of FIGS. 7 and 8, it will be understood that when selecting a candidate resource, the first terminal device 110 may acquire a COT period before performing sidelink communication on the candidate resource. Next, the first terminal device 110 may transmit information regarding the COT period to the second terminal device 120.

[0075] In an embodiment where a first candidate resource that is immediately before a second resource is available, the first terminal device 110 may determine whether a fifth candidate resource that is immediately before a sixth resource is available within the candidate resource set. The sixth resource is reserved by a fourth terminal device. When the fifth candidate resource is available, the first terminal device 110 may select one of the first candidate resource and the fifth candidate resource for sidelink communication.

[0076] In an embodiment where the first candidate resource is before the fifth candidate resource, the first terminal device 110 may select the first candidate resource. This will be described with reference to FIG. 6A.

[0077] As shown in FIG. 6A, candidate resource 610 is immediately before reserved resource 620, and candidate resource 612 is immediately before reserved resource 622. If only one candidate resource is required for sidelink communication, the first terminal device 110 may randomly select one of candidate resources 610 and 612 for sidelink communication. Alternatively, since candidate resource 610 is before candidate resource 612, the first terminal device 110 may select candidate resource 610 for sidelink communication. In this way, it is possible to reduce the delay for sidelink communication.

[0078] In some embodiments, the first terminal device 110 may not have sensing results. In such an embodiment, the first terminal device 110 may randomly select at least one candidate resource within the candidate resource set for sidelink communication.

[0079] As described with reference to FIG. 6B, the first terminal device 110 may select candidate resource 630 for transmission and select candidate resource 632 for retransmission associated with the transmission. If the retransmission is not performed on candidate resource 632, the first terminal device 110 will lose the COT period 640. Similarly, the second terminal device 120 may reserve resource 412 for its retransmission, and the third terminal device 130 may reserve resource 422 for its retransmission. If the retransmission is not performed on candidate resources 412 and 422, the second terminal device 120 and the third terminal device 130 will also lose the COT period 640 shared by the first terminal device 110.

[0080] Embodiments of the present disclosure provide another solution for sidelink communication to solve the above problems and one or more other potential problems. According to this solution, when the first terminal device receives an affirmative response to the transmission or does not receive a negative response to the transmission from the second terminal device, the first terminal device performs a retransmission associated with the transmission on the second resource for the second terminal device. The second resource is within a Channel Occupancy Time (COT) period.

[0081] Hereinafter, with reference to FIGS. 9 to 11, the principle of the present disclosure will be described. FIG. 9 is a flowchart of an exemplary method 900 according to some embodiments of the present disclosure. In some embodiments, the method 900 can be implemented in one of the terminal devices, for example, the first terminal device 110, the second terminal device 120, and the third terminal device 130 as shown in FIG. 1. For the sake of explanation, with reference to FIG. 1, without loss of generality, the method 900 executed by the first terminal device 110 will be described.

[0082] In block 910, the first terminal device 110 performs a transmission on the first resource.

[0083] In block 920, the first terminal device 110 determines whether it has received an affirmative response to the transmission or has not received a negative response to the transmission from the second terminal device 120.

[0084] If an affirmative response to the transmission is received or a negative response to the transmission is not received, in block 930, the first terminal device 110 performs a retransmission for the second terminal device 120 on the second resource. The retransmission is associated with the transmission on the first resource. The second resource is within the COT period.

[0085] The transmission on the first resource may be an initial transmission or a retransmission. In embodiments where the transmission on the first resource is a retransmission, the retransmission on the second resource is the next retransmission associated with the retransmission on the first resource.

[0086] According to method 900, if the first terminal device 110 receives an affirmative response to the transmission or does not receive a negative response to the transmission, it still executes retransmission. In this way, the first terminal device 110 does not lose the COT period. In other words, the first terminal device 110 can maintain the COT period.

[0087] In some embodiments, the first resource is within the COT period, and the COT period is obtained by the first terminal device 110. Consider the example of FIG. 6B. In this example, the first terminal device 110 may execute transmission on resource 630. If an affirmative response to the transmission is received or a negative response to the transmission is not received, the first terminal device 110 may execute retransmission associated with the transmission on resource 632. Both resource 630 and resource 632 are within the COT period 640 obtained by the first terminal device 110.

[0088] In some embodiments, the COT period may be shared by other terminal devices. In such embodiments, the second resource may be within the COT period, and the first resource may be outside the COT period. Consider the example of FIG. 6B further. In this example, the second terminal device 120 may execute a transmission with SCI 410 on a resource before the COT period 640. If an affirmative response to the transmission is received or a negative response to the transmission is not received, the second terminal device 120 may execute retransmission associated with the transmission on resource 412 within the COT period 640 shared by the first terminal device 110.

[0089] In some embodiments, when an affirmative response is received or a negative response is not received, the first terminal device 110 may set the destination layer 1 identifier (ID: identifier) for the second terminal device 120 to an invalid ID or a predefined value. In such an embodiment, the first terminal device 110 may perform retransmission based on the destination layer 1 ID. For example, the predefined value may all be "0". By setting the destination layer 1 ID for the second terminal device 120 to an invalid ID or a predefined value, the retransmission will not reach the second terminal device 120. Therefore, in the second terminal device 120, it is possible to avoid repeated decoding. For this reason, the processing complexity of the second terminal device 120 is not increased.

[0090] In some embodiments, the first terminal device 110 may transmit a transport block (TB: transport block) associated with the transmission based on the destination layer 1 ID. This will be described with reference to FIG. 10A.

[0091] FIG. 10A is a flowchart of an exemplary method 1000A according to some embodiments of the present disclosure. The method 1000A may be regarded as an exemplary implementation of the method 900. In some embodiments, the method 1000A can be implemented in one of the terminal devices, such as the first terminal device 110, the second terminal device 120, and the third terminal device 130 shown in FIG. 1. For the sake of explanation, with reference to FIG. 1, without loss of generality, the method 1000A executed by the first terminal device 110 will be described.

[0092] It should be understood that the candidate resource may correspond to the sidelink permission. Hereinafter, the candidate resource and the sidelink permission may be used interchangeably.

[0093] In block 1010, the media access control (MAC) entity of the first terminal device 110 determines whether the sidelink grant is used for the first transmission or a retransmission associated with the first transmission.

[0094] If the sidelink grant is used for the first transmission, the MAC entity determines, in block 1015, whether the MAC packet data unit (PDU) to be transmitted has already been acquired.

[0095] If the MAC PDU to be transmitted has not been acquired, in block 1030, the MAC entity flushes the HARQ buffer.

[0096] On the other hand, if the MAC PDU to be transmitted has already been acquired, the MAC entity determines, in block 1020, the sidelink transmission information of the transport block (TB) associated with the MAC PDU. Then, in block 1025, the MAC entity stores the MAC PDU and the sidelink transmission information in an associated Hybrid Automatic Repeat Request (HARQ) buffer.

[0097] In block 1035, the MAC entity commands the associated sidelink process to trigger a new transmission. Then, in block 1040, the MAC entity commands the physical layer of the first terminal device 110 to transmit the SCI and the MAC PDU according to the stored sidelink grant and the associated sidelink transmission information.

[0098] In block 1045, the MAC entity monitors the PSFCH for transmission and commands the physical layer to perform PSFCH reception.

[0099] In block 1050, the MAC entity determines whether an acknowledgement of the transmission of the MAC PDU has been received or a negative acknowledgement of the transmission of the MAC PDU has not been received.

[0100] In the prior art, it will be understood that when an acknowledgement of the transmission of the MAC PDU is received or a negative acknowledgement of the transmission of the MAC PDU is not received, the MAC entity flushes the HARQ buffer of the associated sidelink process. However, in method 1000, when an acknowledgement of the transmission of the MAC PDU is received or a negative acknowledgement of the transmission of the MAC PDU is not received, the MAC entity modifies the sidelink transmission information of the TB stored in the HARQ buffer by setting the destination layer 1 ID to an invalid ID or a predefined value in block 1055. For example, the predefined value may all be "0".

[0101] In block 1010, if the MAC entity determines that the sidelink grant is used for retransmission, the MAC entity may further determine whether the HARQ buffer is empty in block 1060. In block 1055, since the MAC entity does not flush the HARQ buffer as in the prior art, the MAC entity may determine in block 1060 that the HARQ buffer is not empty. Therefore, the method proceeds to block 1040, and in block 1040, the first terminal device 110 may retransmit the TB associated with the transmission based on the destination layer 1 ID set in block 1055. For this reason, the retransmitted TB will not reach the second terminal device 120. Therefore, in the second terminal device 120, it is possible to avoid repeated decoding. In this way, the processing complexity of the second terminal device 120 is not increased.

[0102] On one hand, in block 1060, if the MAC entity determines that the HARQ buffer is empty, the method proceeds to block 1065, where the MAC entity ignores the sidelink grant.

[0103] Alternatively, in some embodiments, the first terminal device 110 may not transmit the TB associated with the transmission. Instead, the first terminal device 110 may transmit a dummy TB based on the destination layer 1 ID. Alternatively, in some embodiments, to perform retransmission, the first terminal device 110 may transmit a pre-defined signal and pre-defined sidelink transmission information. This will be described with reference to FIG. 10B.

[0104] FIG. 10B is a flowchart of an exemplary method 1000B according to some embodiments of the present disclosure. Method 1000B may be regarded as another exemplary implementation of method 900. In some embodiments, method 1000B can be implemented in one of the terminal devices, for example, the first terminal device 110, the second terminal device 120, and the third terminal device 130 as shown in FIG. 1. For the sake of explanation, with reference to FIG. 1 and without loss of generality, method 1000B executed by the first terminal device 110 will be described.

[0105] In method 1000B, the operations in blocks 1010, 1015, 1020, 1025, 1030, 1035, 1040, 1045, 1050 are the same as those in method 1000A. Therefore, for the sake of brevity, the details of these operations will not be described.

[0106] Method 1000B is different from method 1000A in blocks 1070 and 1075. In block 1060, when the MAC entity determines that the HARQ buffer is empty (which means that an acknowledgement for transmission has been received or a negative acknowledgement for transmission has not been received), the method proceeds to block 1070. In block 1070, the MAC entity may instruct the associated sidelink process to trigger a retransmission with a dummy TB, with the destination layer 1 ID set to an invalid value or a predefined value. Alternatively, in block 1070, the MAC entity may instruct the associated sidelink process to trigger a retransmission with a predefined MAC PDU and predefined sidelink transmission information. Thus, the dummy TB or the predefined MAC PDU can reach the second terminal device 120. Therefore, in the second terminal device 120, repeated decoding can be avoided. For this reason, the processing complexity of the second terminal device 120 is not increased.

[0107] Additionally, in block 1075, the MAC entity flushes the HARQ buffer of the associated sidelink process.

[0108] In some embodiments, to avoid repeated decoding in the second terminal device 120, the SCI field within the associated PSCCH or SCI may be adjusted. For example, the frequency resource allocation and time resource allocation within the associated PSCCH or SCI should be set to code points corresponding to the absence of reserved resources.

[0109] In some embodiments, the first terminal device 110, the second terminal device 120, or the third terminal device 130 may execute methods 900, 1000A, and 1000B on the retransmission resources within the COT period.

[0110] In some embodiments, if an affirmative response to the transmission is received or a negative response to the transmission is not received, the physical layer of the terminal device may perform retransmission. In such embodiments, the physical layer may transmit a dummy TB or a predefined signal and an SCI. The SCI indicates that the dummy transport block or the predefined signal cannot be decoded. For example, the "destination ID" field in the SCI may be set to an invalid / predefined value to implicitly indicate that the dummy transport block or the predefined signal cannot be decoded. Alternatively, 1 bit in the SCI may explicitly indicate that the dummy transport block or the predefined signal cannot be decoded.

[0111] In some embodiments, Table 1 shows the changes in TS38.321 associated with the exemplary method 900 or 1000A. JPEG2025521228000002.jpg94150

[0112] In some embodiments, Table 2 shows the changes in TS38.321 associated with the exemplary method 900 or 1000B. JPEG2025521228000003.jpg126150

[0113] FIG. 11 is a schematic block diagram of an apparatus 1100 suitable for implementing some embodiments of the present disclosure. The apparatus 1100 may be regarded as another exemplary embodiment of the terminal device 110 as shown in FIG. 1. Therefore, the apparatus 1100 can be realized in the terminal device 110 or at least a part thereof.

[0114] As shown, apparatus 1100 includes a processor 1110, a memory 1120 coupled to the processor 1110, a suitable transmitter (TX) and receiver (RX) 1140 coupled to the processor 1110, and a communication interface coupled to the TX / RX 1140. The memory 1120 stores at least a portion of program 1130. The TX / RX 1140 is used for bidirectional communication. The TX / RX 1140 has at least one antenna to facilitate communication, although the access nodes referred to herein may actually have multiple antennas. The communication interface may represent any interface necessary for communication with other network elements, such as an X2 interface for bidirectional communication between gNBs or eNBs, an S1 interface for communication between a Mobility Management Entity (MME) / Serving Gateway (S-GW) and a gNB or eNB, a Un interface for communication between a gNB or eNB and a Relay Node (RN), or a Uu interface for communication between a gNB or eNB and a terminal device.

[0115] It is assumed that program 1130 includes program instructions that, when executed by the associated processor 1110 as described herein with reference to FIGS. 1-12, enable apparatus 1100 to operate in accordance with embodiments of the present disclosure. Embodiments herein may be implemented by computer software executable by a processor 1110 of apparatus 1100, or by hardware, or by a combination of software and hardware. The processor 1110 may be configured to implement various embodiments of the present disclosure. Further, the combination of the processor 1110 and the memory 1120 may form processing means 1150 suitable for implementing various embodiments of the present disclosure.

[0116] Memory 1120 may be of any type suitable for a local technology network and may, by way of non-limiting example, be implemented using any suitable data storage technology such as a non-transitory computer-readable storage medium, a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, a fixed memory, and a removable memory. Although only one memory 1120 is shown within device 1100, there may be several physically different memory modules within device 1100. Processor 1110 may be of any type suitable for a local technology network and may, by way of non-limiting example, include one or more of a general-purpose computer, a dedicated computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 1100 may have a specific-purpose integrated circuit chip that is temporally dependent on a clock that synchronizes a plurality of processors, such as a main processor.

[0117] The components included in the devices and / or apparatuses of the present disclosure may be implemented in various forms including software, hardware, firmware, or any combination thereof. In one embodiment, one or more units may be implemented using software and / or firmware such as machine-executable instructions stored on a storage medium. In addition to or instead of the machine-executable instructions, some or all of the units within the devices and / or apparatuses may be implemented at least partially by one or more hardware logic components. By way of example and not limitation, exemplary types of hardware logic components that may be used include field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), system-on-a-chip systems (SOCs), complex programmable logic devices (CPLDs), and the like.

[0118] Overall, the various embodiments of the present disclosure may be implemented in hardware or dedicated circuitry, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software executable by a controller, microprocessor, or other computing device. Although the various aspects of the embodiments of the present disclosure are illustrated and described using block diagrams, flowcharts, or other pictorial representations, it should be understood that the blocks, devices, systems, techniques, or methods described herein may be implemented, by way of non-limiting example, in hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or a controller or other computing device, or any combination thereof.

[0119] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer-executable instructions, such as instructions included in program modules, that are executed within a device on a target physical processor or virtual processor to perform the process or method described above with reference to any one of FIGS. 1 to 11. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functions of the program modules may be combined or divided among the program modules as needed. The machine-executable instructions of the program modules may be executed within a local or distributed device. In a distributed device, the program modules may be located in both local and remote storage media.

[0120] The program code for performing the method of the present disclosure may be described in any combination of one or more programming languages. These program codes are provided to a processor or controller of a general-purpose computer, a dedicated computer, or other programmable data processing equipment, and when executed by the processor or controller, the program codes implement the functions / operations specified in the flowchart and / or block diagram. The program code may be executed entirely on the machine, partially on the machine, as an independent software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0121] The above program code may be implemented on a machine-readable medium, which may be any tangible medium that can be utilized by or associated with an instruction execution system, apparatus, or device and that can contain or store a program for the same. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. The machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing media. More specific examples of the machine-readable storage medium may include an electrical connection having one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0122] Note that although the operations have been described in a particular order, it should be understood that such operations may be performed in the particular order shown or in an order sequence, or that all of the described operations may be required to obtain the desired results. In some cases, multitasking and parallel processing may be advantageous. Similarly, although details of some specific embodiments are included in the above discussion, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to a particular embodiment. Some features described in the context of individual embodiments may be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may be implemented separately in multiple embodiments or in any suitable sub-combination.

[0123] Although the present disclosure has been described in language specific to structural features and / or methodological acts, it is to be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as illustrative forms of implementing the claims.

Claims

1. A method implemented for sidelink communication in a first terminal device, comprising: selecting, for the sidelink communication, a first candidate resource according to a determination that the first candidate resource immediately preceding a second resource reserved by a second terminal device is available within a candidate resource set; acquiring a Channel Occupancy Time (COT) period before executing the sidelink communication on the first candidate resource; transmitting first information regarding the COT period to the second terminal device; and a method.

2. The method according to claim 1, further comprising receiving, from a third terminal device, second information regarding a preferred resource set for the sidelink communication, wherein the first candidate resource belongs to the preferred resource set. The method according to claim 1.

3. The method according to claim 1, further comprising: receiving, from a third terminal device, second information regarding a preferred resource set for the sidelink communication; and selecting, for the sidelink communication, a third resource or a fourth resource within the candidate resource set according to a determination that the first candidate resource immediately preceding the second resource and belonging to the preferred resource set is unavailable, wherein the third candidate resource belongs to the preferred resource set, and the fourth resource is immediately preceding the second resource. The method according to claim 1.

4. The selecting of the third resource or the fourth resource comprises: determining whether a third candidate resource belonging to the preferred resource set is available according to a determination that the first candidate resource immediately preceding the second resource and belonging to the preferred resource set is unavailable; selecting the third resource according to a determination that the third candidate resource belonging to the preferred resource set is available; and selecting the fourth resource according to a determination that the third candidate resource belonging to the preferred resource set is unavailable. The method according to claim 3.

5. The selecting of the third resource or the fourth resource comprises: Determining whether a fourth candidate resource immediately preceding the second resource is available according to a determination that the first candidate resource belonging to the preferred resource set and immediately preceding the second resource is unavailable; Selecting the fourth resource according to a determination that the fourth candidate resource immediately preceding the second resource is available; Selecting the third resource according to a determination that the fourth candidate resource immediately preceding the second resource is unavailable, including The method according to claim 3.

6. Further comprising receiving, from a fourth terminal device, third information regarding a resource set not preferred for the sidelink communication; The first candidate resource does not belong to the non-preferred resource set The method according to claim 1.

7. Determining whether a fifth candidate resource immediately preceding a sixth resource reserved by a fifth terminal device is available within the candidate resource set according to a determination that the first candidate resource immediately preceding the second resource is available; Selecting one of the first candidate resource and the fifth candidate resource for the sidelink communication according to a determination that the fifth candidate resource is available; The method according to claim 1, further comprising.

8. The first candidate resource is before the fifth candidate resource; Selecting one of the first candidate resource and the fifth candidate resource includes selecting the first candidate resource The method according to claim 7.

9. A method for sidelink communication, comprising: In a first terminal device, performing transmission on a first resource; Performing, for the second terminal device, a retransmission associated with the transmission on a second resource within a channel occupancy time (COT) period according to a determination that an affirmative response to the transmission has been received or a negative response to the transmission has not been received; A method including.

10. Further comprising setting a destination layer 1 identifier for the second terminal device to an invalid identifier or a predefined value according to a determination that the affirmative response has been received or the negative response has not been received; Performing the retransmission includes performing the retransmission based on the destination layer 1 identifier The method according to claim 9. **Claim 11** Performing the retransmission based on the destination layer 1 identifier includes transmitting a transport block associated with the transmission The method according to claim 10. **Claim 12** Performing the retransmission based on the destination layer 1 identifier includes transmitting a dummy transport block The method according to claim 10. **Claim 13** Performing the retransmission includes transmitting a pre-defined signal and pre-defined sidelink transmission information The method according to claim 9. **Claim 14** Performing the retransmission includes transmitting a dummy transport block, or a pre-defined signal and sidelink control information (SCI), where the SCI indicates that the dummy transport block or the pre-defined signal cannot be decoded The method according to claim 9. **Claim 15** The COT period is acquired by the first terminal device, and the first resource is within the COT period The method according to claim 9. **Claim 16** The COT period is shared by a third terminal device The method according to claim 9. **Claim 17** A terminal device comprising a processor and a memory coupled to the processor for storing instructions, wherein when the instructions are executed by the processor, the method according to any one of claims 1 to 8 is performed Terminal device. **Claim 18** A terminal device comprising a processor and a memory coupled to the processor for storing instructions, wherein when the instructions are executed by the processor, the method according to any one of claims 9 to 16 is performed Terminal device. **Claim 19** A computer-readable medium storing instructions that, when executed on at least one processor of a device, cause the device to perform the method according to any one of claims 1 to 8 Computer-readable medium. **Claim 20** A computer-readable medium storing instructions that, when executed on at least one processor of a device, cause the device to perform the method according to any one of claims 9 to 16 Computer-readable medium.

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