User device and method

Abstract

[0003] Embodiments of the present disclosure relate to a method of communication, a terminal device, and a computer-readable medium. The method includes, at a first terminal device, determining a value of a contention window based on at least one factor related to a sidelink. The method also includes performing a channel access procedure for a sidelink transmission based on the value of the contention window.

Description

[Technical Field]

[0001] FIELD Embodiments of the present disclosure relate generally to the field of telecommunications, and more particularly to a method, a terminal device, and a computer-readable medium for sidelink communication. [Background technology]

[0002] Sidelink in unlicensed spectrum or band (SL-U) is a major topic of the 3rd Generation Partnership Project (3GPP) Release 18.

[0003] For a sidelink terminal device operating in an unlicensed band, a channel access procedure should be used to access the channel. Before the sidelink terminal device performs the channel access procedure, a contention window (CW) should be determined.

[0004] For New Radio (NR) in unlicensed bands (NR-U), the CW is determined and adjusted primarily based on Hybrid Automatic Repeat Request (HARQ) feedback. However, HARQ feedback is optional for sidelink communications. In other words, there may be no HARQ feedback available for CW determination. Therefore, schemes for determining the CW in NR-U cannot work in SL-U. Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, the exemplary embodiments of the present disclosure provide a method of communication, a terminal device, and a computer-readable medium. [Means for solving the problem]

[0006] In a first aspect, a method of communication is provided, the method including, at a first terminal device, determining a value of a contention window based on at least one factor related to a sidelink, and performing a channel access procedure for a sidelink transmission based on the value of the contention window.

[0007] In a second aspect, there is provided a terminal device, the terminal device comprising a processor and a memory storing instructions, the memory and the instructions configured to cause the terminal device, using the processor, to perform a method according to the first aspect.

[0008] In a third aspect, there is provided a computer readable medium having stored thereon instructions which, when executed on at least one processor of a device, cause the device to perform a method according to the first aspect.

[0009] It should be understood that this Summary of the Invention is not intended to identify key or essential features of the embodiments of the present disclosure, nor to limit the scope of the present disclosure. Other features of the present disclosure will be readily apparent from the following description. [Brief explanation of the drawings]

[0010] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description of several embodiments of the present disclosure in the accompanying drawings. [Figure 1] FIG. 1 illustrates an exemplary communication network in which embodiments of the present disclosure may be implemented. [Figure 2] 1 is a flowchart of an exemplary method for determining a CW, according to some embodiments of the present disclosure. [Figure 3] 10 is a flowchart of an exemplary method for determining a CW, in accordance with some other embodiments of the present disclosure. [Figure 4] 10 is a flowchart of an exemplary method for determining a CW in accordance with yet another embodiment of the present disclosure. [Figure 5A] FIG. 1 illustrates an example of sidelink HARQ feedback in accordance with some embodiments of the present disclosure. [Figure 5B] FIG. 1 illustrates an example of sidelink HARQ feedback in accordance with some embodiments of the present disclosure. [Figure 5C] FIG. 1 illustrates an example of sidelink HARQ feedback in accordance with some embodiments of the present disclosure. [Figure 5D] 10 is a flowchart of an exemplary method for determining a CW in accordance with yet another embodiment of the present disclosure. [Figure 6A] FIG. 10 illustrates an example of determining a CW based on reserved resources, according to some embodiments of the present disclosure. [Figure 6B] FIG. 10 illustrates an example of determining a CW based on reserved resources, according to some embodiments of the present disclosure. [Figure 7A] FIG. 10 illustrates an example of determining a CW based on a sidelink CBR according to some embodiments of the present disclosure. [Figure 7B] FIG. 10 illustrates an example of determining a CW based on a sidelink CR according to some embodiments of the present disclosure. [Figure 7C] 10 is a flowchart of an example method for determining a CW based on a SL CBR and a SL CR, according to some embodiments of the present disclosure. [Figure 8A] 1 is a flowchart of an example method for determining a CW based on HARQ feedback and SL CBR, in accordance with some embodiments of the present disclosure. [Figure 8B] 1 is a flowchart of an example method for determining a CW based on HARQ feedback and SCI, in accordance with some embodiments of the present disclosure. [Figure 9]1 is a schematic block diagram of an apparatus suitable for implementing embodiments of the present disclosure, in which identical or similar reference numbers represent identical or similar elements. DETAILED DESCRIPTION OF THE INVENTION

[0011] The principles of the present disclosure will now be described with reference to some exemplary embodiments. It should be understood that these embodiments are provided for illustrative purposes only to aid those skilled in the art in understanding and practicing the present disclosure, and do not imply any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in various ways different from those described below.

[0012] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0013] As used herein, the term "terminal device" means any device capable of wireless or wired communication. Examples of terminal devices include, but are not limited to, user equipment (UE), personal computers, desktop computers, mobile phones, cellular phones, smartphones, personal digital assistants (PDAs), portable computers, tablets, wearable devices, Internet of Things (IoT) devices, any Internet of Things (IoE) device, machine-type communication (MTC) devices, and in-vehicle devices for V2X communications, where the "X" in V2X can represent a pedestrian, vehicle, or infrastructure / network, or an image capture device such as a digital camera, a gaming device, a music storage and playback device, or an internet appliance that enables wireless or wired Internet access and browsing.

[0014] As used herein, the term "network equipment" or "base station" (BS) refers to equipment that can provide or host a cell or coverage area over which terminal devices can communicate. Examples of network equipment include, but are not limited to, a Node B (NodeB or NB), an evolved Node B (eNodeB or eNB), a next generation Node B (gNB), a transmit / receive point (TRP), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a femto node, a pico node, or other low-power node.

[0015] As used herein, the singular forms "a," "an," and "said" include the plural forms unless the context clearly indicates otherwise. The term "comprises" and variations thereof should be understood as open-ended terms meaning "including, but not limited to." The term "based on" should be understood as "based at least in part 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 object. The following may include other explicit and implicit definitions.

[0016] In some instances, values, procedures, or devices are referred to as "best," "lowest," "highest," "minimum," "maximum," etc. It should be understood that such descriptions are intended to illustrate that choices may be made from among many functional alternatives used, and that such choices are not necessarily better, smaller, higher, or otherwise more preferred than other choices.

[0017] As mentioned above, for NR-U, the CW is determined and adjusted mainly based on HARQ feedback. However, HARQ feedback is optional for sidelink communications. In other words, there may be no HARQ feedback available for CW determination. Therefore, a scheme for determining the CW in NR-U may not work in SL-U.

[0018] To address the above-mentioned problems and one or more other potential problems, embodiments of the present disclosure provide a solution for sidelink transmissions. According to the solution, a first terminal device determines a value for a CW based on at least one factor related to the sidelink. The first terminal device then performs a channel access procedure for the sidelink transmission based on the value of the contention window. This solution can enable the channel access procedure for sidelink transmissions in unlicensed bands.

[0019] FIG. 1 is a schematic diagram of an exemplary communication network 100 in which embodiments of the present disclosure may be implemented. As shown in FIG. 1, communication network 100 may include a first terminal device 110 and a second terminal device 120. It should be understood that communication network 100 may further include a network device (not shown). The network device is capable of communicating with first terminal device 110 and second terminal device 120 via respective wireless communication channels. It should be understood that the number of devices in FIG. 1 is given for illustrative purposes and does not imply any limitations on the present disclosure. Communication network 100 may include any suitable number of network devices and / or terminal devices suitable for implementing embodiments of the present disclosure.

[0020] Communications in communication network 100 may conform to any suitable standard, including, but not limited to, Global System for Mobile Communications (GSM), Long Term Evolution (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. Furthermore, communications may be performed according to any currently known or future-developed generation of communication protocols. Examples of communication protocols include, but are not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, and fifth generation (5G) communication protocols.

[0021] In some embodiments, communications in the communications network 100 may include sidelink communications. Sidelink communications are direct wireless radio communications between two or more terminal devices. In this type of communication, two or more terminal devices in close geographic proximity can communicate directly without going through a network device (e.g., an eNB in an LTE system or a gNB in an NR system) or a core network. Thus, data transmission in sidelink communications differs from typical cellular network communications in which a terminal device transmits data to an eNB or gNB (i.e., uplink transmission) or receives data from an eNB or gNB (i.e., downlink transmission). In sidelink communications, data is transmitted directly from a source terminal device to a target terminal device over a unified air interface, e.g., a PC5 interface.

[0022] Sidelink communication can provide several advantages, including reducing data transmission load in the core network, system resource consumption, transmission power consumption and network operation costs, conserving radio spectrum resources and improving the spectral efficiency of cellular wireless communication systems.

[0023] In a sidelink communication system, sidelink resources are used to transmit information between terminal devices. Depending on application scenarios, service types, etc., sidelink communication methods include, but are not limited to, device-to-device (D2D) communication, vehicle-to-everything (V2X) communication, etc.

[0024] V2X communication enables vehicles to communicate with other vehicles (i.e., vehicle-to-vehicle (V2V) communication), infrastructure (i.e., vehicle-to-infrastructure (V2I) communication), wireless networks (i.e., vehicle-to-network (V2N) communication), pedestrians (i.e., vehicle-to-pedestrian (V2P) communication), and even with the owner's home (i.e., vehicle-to-home (V2H) communication). Examples of infrastructure include roadside devices such as traffic lights and toll booths. V2X communication can be used in a wide range of scenarios, including accident prevention, safety, convenience, traffic efficiency, and accident-free driving, ultimately leading to autonomous and self-driving vehicles.

[0025] 1, the first terminal device 110 and the second terminal device 120 are illustrated as vehicles that enable V2X communication. It should be understood that the embodiments of the present disclosure are also applicable to terminal devices other than vehicles, such as mobile phones, sensors, etc.

[0026] The first terminal device 110 determines the value of the CW based on at least one factor related to the sidelink, and then performs a channel access procedure for the sidelink transmission based on the value of the contention window.

[0027] 2 is a flowchart of an example method 200 according to some embodiments of the present disclosure. In some embodiments, method 200 may be implemented in a terminal device, such as first terminal device 110 or second terminal device 120 as shown in FIG. 1. For purposes of explanation, and without loss of generality, method 200 will be described as being performed by first terminal device 110 with reference to FIG. 1.

[0028] In block 210, the first terminal device 110 determines a value for CW based on at least one factor related to the sidelink.

[0029] In block 220, the first terminal device 110 performs a channel access procedure for sidelink transmission based on the value of CW.

[0030] In the following, a general procedure for determining the CW for an SL-U will be described with reference to FIGS.

[0031] 3 is a flowchart of an example method 300 for determining a CW according to some other embodiments of the present disclosure. In some embodiments, the method 300 may be implemented in a terminal device, such as the first terminal device 110 or the second terminal device 120 shown in FIG. 1. For illustrative purposes, and without loss of generality, the method 300 will be described with reference to FIG. 1 as being performed by the first terminal device 110.

[0032] In the exemplary method 300, the value of CW is determined based on one factor related to the sidelink. As shown in FIG. 3, in block 310, the first terminal device 110 determines the value of CW. p The CW min,pTo, i.e., CW p =CW min,p where CW p represents the value of CW for priority p, and CW min,p is the CW for priority p. p Represents the minimum value of .

[0033] In block 320, CW p According to the decision rule, the first terminal device 110 determines whether the factor satisfies a threshold. The threshold may be set or preset. If the factor satisfies the threshold, the method 300 proceeds to block 310. Otherwise, the method 300 proceeds to block 330.

[0034] In block 330, the first terminal device 110 transmits a CW p For example, the first terminal device 110 increases the CW p may be increased to the next highest allowed value for priority p.

[0035] In some embodiments, the CW for the sidelink terminal device p The allowable values may reuse the same allowable value set for a terminal device operating in NR-U.

[0036] Table 1 shows the CW for terminal equipment operating in NR-U. p Here is an example of a set of allowed values:

[0037] [Table 1]

[0038] In Table 1, CW min,p is the CW for priority p. p represents the minimum value of CW max,p is the CW for priority p. p represents the maximum value of T mcot,p denotes the maximum channel occupancy time for priority p.

[0039] For example, as shown in Table 1, for Priority 1, CW p Acceptable values for include 3 and 7. CW min,p The first acceptable value is 3, and the next highest acceptable value is 7. In block 310, the first terminal device 110 starts the CW p = 3. If the first terminal device 110 determines that the factor does not meet the threshold, the first terminal device 110 may set the CW p may be increased to 7.

[0040] For another example, as shown in Table 1, for priority 3, CW p Acceptable values for CW include 15, 31 and 63. min,p is 15, CW min,p The next highest tolerance for is 31, and CW p The next highest allowable value for =31 is 63. In block 310, the first terminal device 110 p = 15. If the first terminal device 110 determines that the factor does not meet the threshold, the first terminal device 110 may set the CW p may be increased to 31.

[0041] In some embodiments, the CW for the sidelink terminal device p The allowable values of CW may be defined, configured, or pre-configured independently for sidelink communications. p The allowable values of may differ from those shown in Table 1.

[0042] It should be noted that the factors may be evaluated or measured during a reference period, which is a timing window that may be set, preset, or defined accordingly.

[0043] In some embodiments, depending on the priority of the sidelink signal or information, a CW may be defined for each priority, so that the terminal device may implement an independent CW determination procedure for each priority.

[0044] In some embodiments, CW p =CW max,p If CW p The next highest tolerance for adjusting CW max,p CW p =CW max,p If is used K times in succession, CW p is the CW for priority p. min,p where K is set or preset for each priority p.

[0045] 4 is a flowchart of an example method 400 for determining a CW according to some embodiments of the present disclosure. In some embodiments, the method 400 may be implemented in a terminal device, such as the first terminal device 110 or the second terminal device 120 shown in FIG. 1. For illustrative purposes, and without loss of generality, the method 400 will be described with reference to FIG. 1 as being performed by the first terminal device 110.

[0046] In the example method 400, the value of CW is determined based on two factors related to the sidelink, which may include a first factor related to the sidelink and a second factor related to the sidelink.

[0047] As shown in FIG. 4, similar to block 310, in block 410, the first terminal device 110 p The CW min,p To, i.e., CW p =CW min,p Set it to be.

[0048] At block 420, CW p According to the decision rule, the first terminal device 110 determines whether the first factor satisfies the first threshold. If the first factor satisfies the first threshold, the method 400 proceeds to block 410. Otherwise, the method 400 proceeds to block 430.

[0049] At block 430, CW pAccording to the decision rule, the first terminal device 110 determines whether the second factor satisfies a second threshold. The second factor is different from the first factor. The second threshold may be the same as or different from the first threshold. The first threshold and the second threshold may be independently set, preset, or defined. If the second factor satisfies the second threshold, the method 400 proceeds to block 450. Otherwise, the method 400 proceeds to block 440.

[0050] In block 440, the first terminal device 110 transmits a CW p For example, the first terminal device 110 increases the CW p may be increased to the next highest acceptable value for priority p. For example, p The tolerances may include those shown in Table 1 below.

[0051] In block 450, the first terminal device 110 selects a CW for priority p. p Keep it as it is.

[0052] A factor meeting a threshold should be understood to mean either: The assessment or measurement of the factor has exceeded the relevant threshold (e.g., the assessment or measurement of the factor may be at or above the relevant threshold, or the assessment or measurement of the factor may be higher than the relevant threshold); or The assessment or measurement of the factor is below the relevant threshold (e.g., the assessment or measurement of the factor may be below the relevant threshold, or the assessment or measurement of the factor may be less than the relevant threshold).

[0053] In some embodiments, the factor is sidelink hybrid automatic repeat request (HARQ) feedback detected by the first terminal device 110; Priority of sidelink signals or information; Sidelink control information (SCI) received by the first terminal device 110; Sidelink Channel Busy Ratio (CBR), or Sidelink channel occupancy ratio (CR), may include at least one of:

[0054] Therefore, the first terminal device 110 may determine the value of CW based on one or more of the items described above.

[0055] In the following, several embodiments for determining the CW based on sidelink HARQ feedback are described.

[0056] Sidelink HARQ feedback can be supported in unlicensed bands, and the terminal device may transmit an acknowledgement (ACK, also referred to as A) or a negative acknowledgement (NACK, also referred to as N) on the physical sidelink control channel (PSCCH) or the physical sidelink feedback channel (PSFCH). According to configuration or pre-configuration, the terminal device may feedback ACK / NACK related to sidelink unicast, groupcast or broadcast.

[0057] The first terminal device 110 may attempt to detect all HARQ feedback on the sidelink. In some embodiments, the HARQ feedback may include one or more HARQ feedbacks associated with sidelink transmissions of the first terminal device 110. This type of HARQ feedback may hereinafter be referred to as a first type of HARQ feedback or a first type of ACK / NACK.

[0058] In some embodiments, the HARQ feedback may include at least one HARQ feedback on at least one potential feedback resource. This type of HARQ feedback may hereinafter be referred to as second-type HARQ feedback or second-type ACK / NACK. For example, the second-type HARQ feedback may include only one or more HARQ feedbacks associated with sidelink transmissions of other sidelink terminal devices other than the first terminal device 110. For another example, the second-type HARQ feedback may include one or more HARQ feedbacks associated with sidelink transmissions of both the other sidelink terminal devices and the first terminal device 110. For another example, the second-type HARQ feedback may include only one or more HARQ feedbacks associated with sidelink transmissions of the first terminal device 110.

[0059] Different schemes for ACK or NACK feedback exist on the sidelink. For example, a terminal device receiving a sidelink transmission may report an ACK or NACK depending on the reception result of a PSSCH (Physical Sidelink Shared Channel). Hereinafter, the terminal device receiving the sidelink transmission may be referred to as an Rx terminal device. Alternatively or additionally, the Rx terminal device may report a NACK only if the PSSCH is not correctly received, and may not report an ACK in other cases. Furthermore, whether an ACK or NACK needs to be reported for a unicast, groupcast, or broadcast may be independently configured.

[0060] By using sidelink HARQ feedback as a factor, the channel conditions are directly reflected, allowing the first terminal device 110 to determine and adjust the CW flexibly and timely.

[0061] Depending on the sidelink feedback scheme, the first terminal device 110 may use different rules to evaluate the factors and further determine the CW. By using the sidelink HARQ feedback as a factor, the first terminal device 110 can: the number of acknowledgments (ACKs) detected by the first terminal device 110; the number of negative acknowledgements (NACKs) detected by the first terminal device 110; the power of the ACK detected by the first terminal device 110, the power of the NACK detected by the first terminal device 110; the energy of the ACK detected by the first terminal device 110, or the energy of the NACK detected by the first terminal device 110; The factor may be determined based on at least one of:

[0062] In some embodiments, the at least one sidelink HARQ feedback comprises: A first type of HARQ feedback; A second type of HARQ feedback, HARQ feedback with potential sidelink control information resources, HARQ feedback associated with sidelink unicast transmissions; HARQ feedback associated with a sidelink groupcast transmission, or HARQ feedback associated with sidelink broadcast transmissions; may include at least one of:

[0063] In some embodiments, the number of ACKs includes the number of ACKs for at least one transmission block (TB) or at least one code block group (CBG), and the number of NACKs includes the number of NACKs for the at least one TB or the at least one CBG.

[0064] In some embodiments, the first terminal device 110 the number of subchannels or interlaces in the reference period; the number of physical sidelink shared channel (PSSCH) resources within the reference period; the number of physical sidelink control channel (PSCCH) resources within the reference period; the number of sidelink control information signals detected within the reference period; the number of physical sidelink feedback channel (PSFCH) resources within the reference period; The number of terminal devices in the group, the number of sidelink channel occupancies (COs) within the reference period; the number of sidelink COs containing PSSCH transmissions within the reference period; the number of sidelink COs that include PSCCH transmissions within the reference period; the number of sidelink COs that include a PSFCH transmission within the reference period; the number of TBs transmitted by the sidelink terminal device within the reference period; the number of TBs transmitted by the first terminal device within the reference period; the number of TBs detected by the first terminal device within the reference period; or the number of CBGs of the TB transmitted or detected by the first terminal device 110; Alternatively, the method may determine a first ratio of the number of ACKs to one of the above, or a second ratio of the number of NACKs to one of the above.

[0065] As mentioned above, using sidelink HARQ feedback may involve multiple practical schemes, and any combination of the above items may be used for sidelink CW determination, provided there is no contradiction.

[0066] In the following, some examples of determining CW for SL-U based on sidelink HARQ feedback are described with reference to Figures 5A to 5D. For illustrative purposes, the examples are described with reference to the general procedure of Figure 3.

[0067] 5A, 5B, and 5C are diagrams illustrating examples of sidelink HARQ feedback according to some embodiments of the present disclosure. In the examples of FIGS. 5A and 5B, the first terminal device 110 determines whether to provide a CW HARQ feedback according to the number of ACKs or NACKs detected within a reference period. p The first type of HARQ feedback is used as a factor. In the case of unicast, the first type of HARQ feedback is from one or more terminal devices receiving sidelink transmissions from the first terminal device 110. In the case of groupcast, the first type of HARQ feedback may be reported by one or more terminal devices receiving sidelink transmissions from the first terminal device 110, i.e., member terminal devices in the group.

[0068] In the case of unicast or groupcast communication, the terminal device (e.g., the first terminal device 110) transmitting the sidelink transmission may identify one or more Rx terminal devices, making it easier to obtain ACK or NACK reports. The number of ACKs may indicate the channel conditions and the probability of a successful sidelink transmission, further contributing to the CW adjustment procedure. In the following, the terminal device transmitting the sidelink transmission may also be referred to as the Tx terminal device.

[0069] In the case of sidelink unicast communication in an unlicensed band, the Rx terminal device may report ACK or NACK feedback to the Tx terminal device. The Tx terminal device may then detect the ACK or NACK reported by the Rx terminal device and further determine a CW for the channel access procedure for sidelink transmission depending on the number of received ACKs. Accordingly, a threshold value for the number of ACKs for unicast may be defined to determine the CW.

[0070] In the case of sidelink groupcast communication in an unlicensed band, the Rx terminal may report ACK or NACK feedback to the Tx terminal. The Tx terminal may then detect the ACKs or NACKs reported by two or more Rx terminals and further determine a CW for the channel access procedure according to the number of received ACKs. Accordingly, a threshold for the number of ACKs or NACKs for groupcast may be defined to determine the CW.

[0071] In the examples of Figures 5A and 5B, the ACK reflects the sidelink transmission of the Tx terminal device, i.e., the Tx terminal device uses the first type of ACK as a factor. A threshold for the number of ACKs may be preset or defined as M. The Tx terminal device performs a sidelink unicast with the Rx terminal device and indicates the Rx terminal device to report an ACK or NACK. The first type of ACK is used as a factor. Therefore, the Tx terminal device determines the CW depending on the ACK that reflects the reception result of its own transmission. Within the ACK or NACK reference period, the Tx terminal device detects and receives feedback from the Rx terminal device and counts the number of received ACKs.

[0072] As shown in FIG. 5A, within reference period #1, the Tx terminal receives an ACK or NACK report from the Rx terminal, and three ACKs are detected by the Tx terminal. As shown by block 320 of FIG. 3, the Tx terminal determines that a factor (equal to 3) exceeds a threshold M=1. Next, method 300 proceeds to block 310, where the Tx terminal determines that the CW p =CW min,p It is determined as follows.

[0073] Within reference period #2, the Tx terminal receives an ACK or NACK report from the Rx terminal, and no ACK is detected. As shown by block 320 of FIG. 3, the Tx terminal determines that the factor is below the threshold M=1. Next, method 300 proceeds to block 330, where the Tx terminal determines that the CW pIncrease to the next highest acceptable value.

[0074] In the example of Fig. 5B, the threshold for the number of ACKs is preset, i.e., M = 3. The Tx terminal performs a sidelink groupcast with the member terminals in the group and indicates the member terminals to report ACK / NACK. The first type of ACK is used as a factor. Within the ACK / NACK reference period, the Tx terminal detects and receives feedback from the Rx terminal and counts the number of received ACKs.

[0075] As shown in FIG. 5B, within reference period #1, the Tx terminal receives an ACK / NACK report from the Rx terminal, and the number of ACKs is 7. As shown by block 320 of FIG. 3, the Tx terminal determines that the factor (equal to 7) exceeds the threshold M=3. Next, method 300 proceeds to block 310, where the Tx terminal determines whether the CW p =CW min,p It is determined as follows.

[0076] Within reference period #2, the Tx terminal receives an ACK or NACK report from the Rx terminal, and the number of detected ACKs is 2. As shown by block 320 of FIG. 3, the Tx terminal determines that the factor (equal to 2) is below the threshold M=3. Next, method 300 proceeds to block 330, where the Tx terminal determines that the CW p Increase to the next highest acceptable value.

[0077] In the example of FIG. 5C, the first terminal device 110 transmits the CW signal according to the first ratio or the second ratio. p The second type of ACK is used as a factor. The first ratio may be evaluated based on the amount of PSSCH / PSFCH resources or the number of SCIs detected.

[0078] Considering that multiple terminal devices may transmit on the sidelink in the unlicensed band, utilizing detection of all potential ACK / NACKs can represent an evaluation of the transmission results of more terminal devices. Furthermore, it may be more efficient for the terminal device to determine the CW according to the first ratio evaluated by all candidate resources.

[0079] For sidelink communication, potential resources to be used, e.g., candidate start positions in the time domain for sidelink transmission, available resources for sidelink channels, or channel structure, may be preconfigured for the terminal device. Based on this, the maximum possible number of resources or sidelink channels can be determined. Furthermore, the first ratio may be evaluated accordingly.

[0080] In this example, the first terminal device 110 attempts to detect all ACK / NACK signals in the unlicensed band that reflect sidelink transmissions of different Tx terminal devices, i.e., terminal devices that use the second type of ACK as a factor.

[0081] In this example, the threshold for the first ratio is a fixed value, i.e., Z=5%. The first terminal device 110 should blindly detect and count the number of ACKs within the reference period and divide it by the number of associated resources or channels. In this example, the second type of ACK is used as a factor, i.e., the first terminal device 110 attempts to detect all potential ACKs on the sidelink, and then evaluates the first ratio and may further determine the CW accordingly.

[0082] Specifically, the maximum number of PSFCH resources in the reference period may be determined according to the sidelink channel structure and configuration in the unlicensed band, and based on this, the first ratio may be evaluated as the number of ACKs detected by the first terminal device 110 divided by the number of PSFCH resources in the reference period.

[0083] As shown in FIG. 5C, within the reference period, the first terminal device 110 detects ACK / NCK on the PSFCH resource and counts up the number of detected ACKs. Then, the first terminal device 110 evaluates a factor, i.e., a first ratio, by dividing the number of ACKs by the number of PSFCH resources. As shown by block 320 in FIG. 3, if the first ratio is equal to or greater than a threshold Z=5%, the first terminal device 110 performs CW p =CW min,p Otherwise, the first terminal device 110 determines that the CW p Increase to the next highest acceptable value.

[0084] For another example (not shown), the first ratio may be determined based on a number of PSSCH resources reflecting a potential amount of sidelink data transmission. The number of PSSCH resources in the reference period may be determined according to a sidelink channel structure and configuration in the unlicensed band. Based on this, the first ratio may be evaluated as the number of ACKs detected by the first terminal device 110 divided by the number of PSSCH resources in the reference period.

[0085] Within the reference period, the first terminal device 110 detects A / Ns and counts the number of detected ACKs. Then, the first terminal device 110 evaluates a factor, i.e., a first ratio, by dividing the number of ACKs by the number of PSSCH resources. As shown by block 320 in FIG. 3, if the first ratio is equal to or greater than a threshold Z=5%, the first terminal device 110 starts the CW p =CW min,p Otherwise, the first terminal device 110 determines that the CW p Increase to the next highest acceptable value.

[0086] As in the example above, the first ratio is: The number of ACKs divided by the number of subchannels in the reference period, The number of ACKs divided by the number of interlaces in the reference period, or The number of ACKs divided by the number of SCIs detected within the reference period, It may be evaluated as:

[0087] In some embodiments, the first terminal device 110 may determine the value of CW based on NACKs detected within the reference period (in the case of only NACKs). In such embodiments, the first terminal device 110 may use a second ratio or the power of the NACK as a factor. The power of the NACK may be defined as the reference signal received power (RSRP) of the associated resource.

[0088] In a scenario where ACK is unavailable, using NACK-related information as a factor can provide a reasonable reference for determining CW. Specifically, an evaluation scheme based on the power or energy of NACK is more feasible for the terminal device.

[0089] Specifically, for sidelink groupcast communication, a NACK-only feedback scheme may be configured in which the Rx terminal device reports a NACK on the sidelink only if it fails to decode data on the PSSCH resource, and does not report an ACK. For this scenario, the NACK detected by the terminal device should be used as a factor, and the CW may be determined according to an evaluation of the NACK compared with a relative threshold.

[0090] If the Rx terminal devices in the group transmit NACKs using independent feedback resources, the Tx terminal device may identify each NACK and evaluate the second ratio by dividing the number of received NACKs by the number of terminal devices in the group. A threshold for the second ratio may be preset.

[0091] If two or more terminal devices report NACK on the same resource, i.e., multiple NACK signals may overlap, the Tx terminal device may measure the signal power on the feedback resource. Therefore, the RSRP or RSRQ of the signal on the PSFCH resource may be used as a threshold.

[0092] In one example, the threshold for the second ratio is defined as a fixed value represented by Z, for example, Z=60%. The Tx terminal performs sidelink groupcast transmission with member terminals in the group and indicates to the member terminals to feedback using a NACK-only scheme. That is, if data reception on the PSSCH fails, the member terminal sends a NACK to the Tx terminal. According to the feedback scheme setting, each member terminal in the group has a dedicated feedback resource, and the Tx terminal can distinguish NACKs from different member terminals. Within the reference period, the Tx terminal detects and receives feedback from the member terminals and counts the total number of detected NACKs.

[0093] Within the reference period, the Tx terminal detects NACKs on the feedback resource and counts up the number of detected NACKs. Then, the Tx terminal evaluates a factor, i.e., a second ratio, by dividing the number of NACKs by the number of member terminals. As shown by block 320 in FIG. 3, if the second ratio is below a threshold Z=60%, the Tx terminal decides to use CW p =CW min,p Otherwise, the Tx terminal device determines p Increase to the next highest acceptable value.

[0094] In another example, a power threshold associated with a signal detected within a PSFCH resource is defined within the system and denoted by P. The Tx terminal device performs sidelink groupcast transmissions with member terminal devices in the group and indicates to the member terminal devices that, if data reception fails, they should report a NACK on the same resource. According to the feedback scheme configuration, member terminal devices that fail to decode the transmission will transmit a NACK signal on the indicated resource. The Tx terminal device may then determine the CW by measuring the RSRP of the feedback resource and comparing the received RSRP of the NACK to a threshold.

[0095] Within the reference period, the Tx terminal measures the signal power of the feedback resource. As shown by block 320 in FIG. 3, if the RSRP of the feedback resource used for NACK is below the threshold P, the Tx terminal will p =CW min,p Otherwise, the Tx terminal device determines p Increase to the next highest acceptable value.

[0096] In some embodiments, the first terminal device 110 may determine the value of CW according to both the ACK and NACK detected within the reference period.

[0097] When different HARQ feedback schemes are used simultaneously, the terminal device may determine the CW based on the cleverness of the A / N detection, in this case for a scheme that can be used for a hybrid scenario of sidelink feedback schemes.

[0098] Specifically, for sidelink communication, both the A / N feedback scheme and the NACK-only feedback scheme may be configured in the same resource pool, i.e., the Tx terminal device may receive ACK or NACK on the sidelink feedback resource and may perform a CW decision procedure based on both ACK and NACK situations.

[0099] In one embodiment, the CW may be determined according to both the ACK and the NACK. Specifically, the first ratio and the received energy of the NACK may be used as factors. The threshold may be set by a Road Side Unit (RSU). For example, the threshold for the first ratio may be represented by Z, and the threshold for the energy of the NACK may be represented by T. res where Z=5%. Therefore, the terminal device may determine the CW based on the threshold and the A / N reception status, as will be described with reference to FIG. 5D.

[0100] 5D is a flowchart of an example method 500 for determining a CW according to some embodiments of the present disclosure. In some embodiments, method 500 may be implemented in a terminal device, such as first terminal device 110 or second terminal device 120 as shown in FIG. 1. For purposes of explanation, and without loss of generality, method 500 will be described as being performed by first terminal device 110 with reference to FIG. 1.

[0101] In the exemplary method 500, both ACK and NACK related information are used as factors.

[0102] As shown, in block 510, the first terminal device 110 receives a CW p =CW min,p where CW min,p is the CW for priority p p Represents the minimum value of .

[0103] At block 520, the first terminal device 110 determines whether a sidelink ACK is detected. In other words, the first terminal device 110 determines whether a sidelink ACK is available. If a sidelink ACK is available, the method 500 proceeds to block 530; otherwise, the method 500 proceeds to block 550.

[0104] In block 530, the first terminal device 110 determines whether the first ratio is not less than Z. If the first ratio is not less than Z, the method 500 proceeds to block 510, where the first terminal device 110 determines whether the first ratio is less than Z. p =CW min,p Otherwise, the method 500 proceeds to block 540.

[0105] In block 540, the first terminal device 110 transmits a CW p to the next highest tolerance for priority p.

[0106] In block 550, the first terminal device 110 determines whether the signal energy of the resource used for NACK is T res Determine whether the signal energy of the resource used for NACK is below T res If so, the method 500 proceeds to block 560. Otherwise, the method 500 proceeds to block 540.

[0107] In block 560, the first terminal device 110 selects a CW for priority p. p Keep it as it is.

[0108] In some embodiments, the sidelink terminal device may obtain information by detecting and decoding the SCI and further determine the CW based on the information obtained from the SCI. In the following, some embodiments for determining the CW based on the SCI received by the first terminal device 110 are described.

[0109] In some embodiments, information received from the SCI may determine the CW independently as one or more factors or in combination with other factors.

[0110] The indications in the SCI of other sidelink terminal devices may provide additional information for the CW decision. Using the indications from the SCI makes the CW decision more efficient and contributes to the sidelink resource selection.

[0111] In some embodiments, the first terminal device 110 may blindly detect and decode the SCI in the side link resources, and within the SCI: ACK or NACK indication, The priority of the data packet on the associated PSSCH, Related PSSCH cast types, one or more resources used for the associated PSSCH; one or more resources reserved for data packets, or Number of retransmissions, At least one of the following may be identified:

[0112] The one or more resources used for the associated PSSCH or reserved for the associated data packet may include an indication of the location or number of subchannels or interlaces used for the PSSCH and the slot index or spacing between the current slot and the reserved resource.

[0113] In some embodiments, any one or more of the above listed instructions within the SCI may be used as a factor in the CW determination.

[0114] For a sidelink terminal device, a resource reservation indication may be obtained from the SCI indicating that the resources will be used in the next slot, meaning that the reserved resources should not be used by other sidelink terminal devices.

[0115] Therefore, the third ratio associated with the reserved resources can reflect the channel conditions to some extent, and determining the CW based on the third ratio can optimize resource selection for the sidelink terminal device.

[0116] In the following, several embodiments are described that determine the CW based on one or more reserved resources indicated by the SCI.

[0117] An SCI indicating at least one resource reserved for at least one retransmission or next transmission of a Tx terminal device is transmitted by one or more sidelink terminal devices. By decoding the SCI(s) of the other terminal devices, the sidelink terminal devices can obtain this information and avoid using the reserved resources of the other terminal devices.

[0118] Within the SCI, reserved resources are the number of subchannels or interlaces of the reserved resources; the subchannel or interlace location of the reserved resource; Reserved resource slots, the slot spacing of the reserved resource, including the slot spacing between the SCI slot and the reserved resource, or the slot spacing between adjacent reserved resources; or Transmission period, may be indicated through at least one of

[0119] Based on the indication of the at least one reserved resource, the first terminal device 110: the number of subchannels or interlaces indicated by the SCI within the reference period; the number of retransmissions indicated by the SCI within the reference period, or the number of periodic transmissions according to the period indicated by the SCI within the reference period; The number of reserved resources may be evaluated according to at least one of:

[0120] Additionally, a third ratio related to the reserved resources may be determined as the number of reserved resources divided by the number of available resources in the reference period.

[0121] In some embodiments, the number of available resources in the reference period is the number of slots in the reference period, The number of subchannels or interlaces in the slot, or the number of slots in the sidelink resource pool during the reference period, may be determined according to at least one of:

[0122] An example of determining a CW based on reserved resources will now be described with reference to Figure 6A. For illustrative purposes, the example will be described with reference to the general procedure of Figure 3.

[0123] In the example of FIG. 6A, a threshold for the third ratio may be preset and represented by R. For example, R=60%. The first terminal device 110 may blindly detect SCI on the PSCCH and evaluate the number of reserved resources within the reference period. The first terminal device 110 may then determine the third ratio by dividing the number of reserved resources by the number of available resources within the reference period.

[0124] In this example, the number of reserved resources is the number of subchannels of a slot in the reference period, and the number of available resources is determined as the number of subchannels and slots in the resource pool in the reference period.

[0125] Specifically, the number of subchannels and the number of slots in the resource pool may be determined according to the sidelink channel structure and configuration in the unlicensed band. As shown in FIG. 6A, the number of reserved resources is 6, and the number of available resources is 24. Therefore, the ratio of the number of reserved resources to the number of available resources is 25%, which is below the threshold (60%). Therefore, as shown by block 320 in FIG. 3, the first terminal device 110 may use the CW p =CW min,p It is determined as follows.

[0126] In some embodiments, data packets transmitted on the sidelink may have different priorities, and the Tx terminal device may determine the CW based on a third ratio of the associated priorities and the priority of its own transmission. A threshold for the third ratio may be specified for each priority. In other words, a threshold for the third ratio may be set for each data priority.

[0127] By considering the priority of sidelink data packets, terminal devices with higher priority requirements may have more opportunities to occupy channel resources, thus contributing to the performance of the sidelink system.

[0128] In some embodiments, the first terminal device 110 may obtain a threshold value for the third ratio from a network device. For example, for priority level #1, the threshold value for the third ratio is R1, for priority level #2, the threshold value for the third ratio is R2, and so on. The first terminal device 110 may blindly detect SCI on the PSCCH, evaluate the number of reserved resources per priority within the reference period, and divide it by the number of available resources within the reference period.

[0129] Specifically, for the first terminal device 110 to determine the CW for its own transmission, the transmitted data packet has priority level #3. Next, the first terminal device 110 may detect the SCI within the reference period and determine a third ratio for a higher priority than its own transmission.

[0130] An example of determining a CW based on reserved resources and the priority of the reserved resources will be described below with reference to Figure 6B. For illustrative purposes, the example will be described with reference to the general procedure of Figure 3.

[0131] 6B, the first terminal device 110 determines a third ratio for priority levels #1 and #2, and the resources reserved for priority levels #3 and #4 are not included in the determination of the third ratio. Based on this, the first terminal device 110 may further determine the CW by comparing the third ratio with a ratio threshold for priority level #3.

[0132] Within the reference period, the first terminal device 110 detects one or more SCIs on the PSCCH resources and counts up the number of reserved resources for priority levels #1 and #2 because its transmitted data packet has priority level #3. The first terminal device 110 then evaluates the factor, i.e., the third ratio of priority levels higher than its own transmission, by dividing the number of reserved resources having priority levels #1 and #2 by the number of available resources. As shown by block 320 in FIG. 3, if the third ratio is below threshold R3, the first terminal device 110 performs CW p =CW min,p Otherwise, the first terminal device 110 determines that the CW p Increase to the next highest acceptable value.

[0133] In some embodiments, the first terminal device 110 may determine the CW according to one or more retransmission numbers indicated in at least one SCI.

[0134] The number of retransmissions reflects the channel condition to some extent, i.e., the more retransmissions, the lower the transmission success rate and the worse the channel condition. Therefore, by using the number of retransmissions as a factor, a more efficient CW determination can be achieved.

[0135] By decoding one or more SCIs on the sidelink control channel within the reference period, the first terminal device 110 may obtain the retransmission counts of other Tx terminal devices. The maximum number of retransmissions within the reference period, and Average number of retransmissions during the reference period may be evaluated.

[0136] It should be understood that in some embodiments, the first terminal device 110 may obtain the number of retransmissions of one of the other Tx terminal devices within the reference period. In such embodiments, the maximum number of retransmissions and the average number of retransmissions are each equal to the number of retransmissions.

[0137] The RSU may set a threshold for the number of retransmissions to the sidelink terminal device served by the RSU. Specifically, the specified threshold may be a threshold for the maximum number of retransmissions or a threshold for the average number of retransmissions.

[0138] In one example, the first terminal device 110 detects one or more SCIs on the PSCCH resource and records the maximum number of retransmissions within the reference period. The first terminal device 110 then compares the factor, i.e., the maximum number of retransmissions, with an associated threshold. As shown by block 320 in FIG. 3, if the maximum number of retransmissions is less than or equal to the threshold, the first terminal device 110 performs CW p =CW min,p Otherwise, the first terminal device 110 determines that the CW p Increase to the next highest acceptable value.

[0139] In some embodiments, in case of sidelink communication in unlicensed bands, sidelink-related measurements, such as the sidelink CBR in unlicensed bands, may also be evaluated by the first terminal device 110 and used for CW determination. In the following, the sidelink CBR may be referred to as SL CBR.

[0140] The SL CBR is a dedicated parameter that describes the sidelink channel conditions and is used for sidelink resource selection. In unlicensed bands, using similar measurements in unlicensed bands can provide additional advantages over CW measurements, especially in scenarios where other factors are unavailable.

[0141] In some embodiments, the SL CBR is a portion of subchannels or interlaces in the sidelink resource pool whose power or energy measured by the first terminal device 110 exceeds a threshold within a reference period; or the portion of subchannels or interlaces whose power or energy measured by the first terminal device 110 exceeds the threshold within the reference period; It may be determined as one of:

[0142] In some embodiments, the power or energy measured by the first terminal device 110 may be represented by one of a received signal strength indicator (RSSI), a reference signal received power (RSRP), or a reference signal received quality (RSRQ).

[0143] For sidelink terminal devices operating in unlicensed bands, the threshold for the SL CBR may be pre-configured per priority, i.e., a dedicated threshold for the SL CBR may be pre-configured for each priority of data. According to the threshold, the first terminal device 110 may determine the CW according to a threshold related to the priority of its own transmission and the SL CBR measured within the reference period. Since the CW is determined based on the priority and the SL CBR, different possibilities are provided for the terminal devices, which can improve the performance of the sidelink system.

[0144] An example of determining the CW based on the SL CBR will be described below with reference to FIG. 7A.

[0145] In this example, the first terminal device 110 obtains a threshold for SL CBR for each priority according to system pre-configuration. For example, for priority level #1, the threshold is R1, for priority level #2, the ratio threshold is R2, and so on. The first terminal device 110 may measure the signal strength for each subchannel, count up the number of subchannels with RSSI higher than the RSSI threshold, and divide it by the total number of subchannels configured in the transmission pool within the reference period. It should be understood that the threshold for RSSI is different from the thresholds R1 and R2 for SL CBR.

[0146] In particular, for the first terminal device 110 to determine the CW for its own transmission, the transmitted data packet has priority level #3. The first terminal device 110 may measure the RSSI of the sidelink resources within the reference period and evaluate the SL CBR using an RSSI threshold preset by the system. Based on this, the first terminal device 110 may further determine the CW by comparing the measured SL CBR with the threshold for priority level #3.

[0147] Within the reference period, the first terminal device 110 detects signals on the PSSCH resources, measures the RSSI of the sidelink subchannels, and counts up the number of subchannels with RSSI higher than the associated threshold. As shown in Figure 7A, the number of subchannels with RSSI higher than the associated threshold is 8.

[0148] Next, the first terminal device 110 evaluates a factor, i.e., the SL CBR, by dividing the number of subchannels with RSSI higher than the threshold by the number of subchannels in the reference period. The number of subchannels in the reference period may be determined based on the number of subchannels in the resource pool and the number of slots in the reference period, where the number of subchannels in the resource pool may be determined based on the sidelink channel structure and configuration in the unlicensed band. The SL CBR may be determined based on this. As shown in FIG. 7A, the number of subchannels in the reference period is 25. Therefore, the SL CBR is equal to 8 / 25=32%.

[0149] As shown by block 320 in FIG. 3, if the SL CBR is less than or equal to the threshold R3, the first terminal device 110 p =CW min,p Otherwise, the first terminal device 110 determines that the CW p Increase to the next highest acceptable value.

[0150] In some embodiments, for sidelink communication in unlicensed bands, the sidelink CR represents the sidelink channel condition and is also a dedicated parameter used for sidelink resource selection. The sidelink CR in unlicensed bands may also be evaluated by the first terminal device 110 and used for CW determination. In the following, the sidelink CR may be referred to as SL CR.

[0151] In some embodiments, the SL CR is the total number of sub-channels used for transmission of the first terminal device 110 divided by the total number of sub-channels in the sidelink resource pool within the reference period; the total number of subchannels used for transmission of the first terminal device 110 divided by the total number of subchannels in the reference period; the total number of interlaces used for transmission of the first terminal device 110 divided by the total number of interlaces in the sidelink resource pool within the reference period, or the total number of interlaces used for transmission of the first terminal device 110 divided by the total number of interlaces in the reference period; It may be determined as one of:

[0152] For a sidelink terminal device operating in an unlicensed band, a threshold for the SL CR may be pre-configured per priority, i.e., a dedicated threshold for the SL CR may be pre-configured for each priority of data. According to the threshold, the terminal device may determine a CW according to a threshold related to the priority of its own transmission and the SL CR measured within the reference period. Since the CW is determined based on the priority and the SL CR, different possibilities are provided for the terminal device, which can improve the performance of the sidelink system.

[0153] An example of determining the CW based on the SL CR will be described below with reference to FIG. 7B.

[0154] In this example, the first terminal device 110 obtains a threshold value for the SL CR for each priority level according to the system pre-configuration. For example, for priority level #1, the threshold value is R1, for priority level #2, the ratio threshold is R2, and so on. The first terminal device 110 may evaluate the number of interlaces already used and / or to be used for its sidelink transmission within the reference period and divide it by the total number of configured interlaces within the reference period.

[0155] In particular, in order for the first terminal device 110 to determine the CW for its own transmission, the transmitted data packet has priority level #3. Based on this, the first terminal device 110 may determine the CW by comparing its SL CR with a threshold for priority level #3.

[0156] In the example of Figure 7B, the reference period is represented by a sidelink channel occupation (CO) time. Using the reference period, the first terminal device 110 counts up the number of interlaces used in the last sidelink CO. As shown in Figure 7B, the number of interlaces used in the last sidelink CO is 2.

[0157] The first terminal device 110 then evaluates the factor, i.e., the SL CR, by dividing the number of interlaces used for its sidelink transmission by the number of interlaces in the CO. Specifically, the number of interlaces in the reference period may be determined according to the number of interlaces for sidelink communication, which may be determined according to the sidelink resource configuration in the unlicensed band. As shown in Figure 7B, the number of interlaces in the CO is 5.

[0158] As shown by block 320 in FIG. 3, if the SL CR is less than or equal to the threshold R3, the first terminal device 110 starts the CW p =CW min,p Otherwise, the first terminal device 110 determines that the CW p Increase to the next highest acceptable value.

[0159] In some embodiments, the first terminal device 110 may determine the CW based on the SL CBR and the SL CR. The SL CBR represents the channel conditions of the transmissions of other terminal devices, while the SL CR represents the resources used by the terminal device itself to determine the CW for its own transmission. Combining these two factors can determine a more appropriate CW and further reduce the possibility of resource collision.

[0160] An exemplary method 700 for determining a CW based on a SL CBR and a SL CR will now be described with reference to FIG. 7C.

[0161] In the method 700, both the SL CR and the CBR are p The definitions of the SL CR and the SL CBR are the same as in the above-described embodiment, and are evaluated based on the SL CR, the SL CBR, and the subchannel.

[0162] The SL CBR is used as the first factor related to the side link, and the SL CR is used as the CW p The first and second thresholds R1 and R2 for SL CBR and the third threshold for CR are set by the network device and are used as the second factor related to the sidelink for the decision.

[0163] As shown in FIG. 7C, in block 710, the first terminal device 110 transmits a CW p =CW min,p where CW min,p is the CW for priority p. p represents the minimum allowable value of

[0164] In block 720, first terminal device 110 determines whether the SL CBR is below a first threshold R1. If the SL CBR is below the first threshold R1, method 700 proceeds to block 710, where first terminal device 110 determines whether the SL CBR is below a first threshold R1.p =CW min,p If the SL CBR is not below the first threshold R1, the method 700 proceeds to block 730, where the first terminal device 110 determines whether the SL CBR has exceeded a second threshold R2.

[0165] If the SL CBR does not exceed the second threshold R2, method 700 proceeds to block 740, where first terminal device 110 determines whether the SL CBR is below a third threshold T. If the SL CBR exceeds the second threshold R2, method 700 proceeds to block 760, where first terminal device 110 determines whether the SL CBR is below a third threshold T. p to the next highest tolerance for priority p.

[0166] If the SL CR is below the third threshold T, the first terminal device 110 may initiate a CW p If the SL CR is not below the third threshold T, the method 700 proceeds to block 760, where the first terminal device 110 maintains the value of CW p to the next highest tolerance for priority p.

[0167] In some embodiments, first terminal device 110 may determine the CW based on HARQ feedback and SL CBR, as described with reference to FIG. 8A.

[0168] 8A is a flowchart of an example method 800 for determining a CW according to some embodiments of the present disclosure. In some embodiments, method 800 may be implemented in a terminal device, such as first terminal device 110 or second terminal device 120 as shown in FIG. 1. For purposes of explanation, and without loss of generality, method 800 will be described as being performed by first terminal device 110 with reference to FIG. 1.

[0169] The exemplary method 800 is similar to the exemplary method 500. The exemplary method 800 begins with a step 850 in which the first terminal device 110 determines whether the SL CBR is greater than or equal to a threshold T CRB SL differs from exemplary method 500 in that it determines whether the CBR is less than T CRB If so, the method 800 proceeds to block 560. Otherwise, the method 800 proceeds to block 540.

[0170] In some embodiments, the first terminal device 110 may determine the CW based on the HARQ feedback and the reserved resources indicated in the SCI described with reference to FIG. 8B.

[0171] 8B is a flowchart of an example method 805 for determining a CW according to some embodiments of the present disclosure. In some embodiments, the method 805 may be implemented in a terminal device, such as the first terminal device 110 or the second terminal device 120 shown in FIG. 1. For purposes of explanation, and without loss of generality, the method 805 will be described as being performed by the first terminal device 110 with reference to FIG. 1.

[0172] The example method 805 is similar to the example method 500. The example method 805 includes, at block 855, determining whether the first terminal device 110 detects that the third ratio within the reference period is greater than or equal to a threshold T res The third ratio is different from the exemplary method 500 in that it determines whether the third ratio is below a threshold T res If so, the method 805 proceeds to block 560. Otherwise, the method 805 proceeds to block 540.

[0173] 9 is a schematic block diagram of an apparatus 900 suitable for implementing some embodiments of the present disclosure. The apparatus 900 may be considered as another exemplary embodiment of the first terminal device 110 or the second terminal device 120 shown in FIG. 1. Accordingly, the apparatus 900 may be implemented in or as at least a part of the first terminal device 110 or the second terminal device 120.

[0174] As shown, the apparatus 900 comprises a processor 910, a memory 920 coupled to the processor 910, a suitable transmitter (TX) and receiver (RX) 940 coupled to the processor 910, and a communication interface coupled to the TX / RX 940. The memory 920 stores at least a portion of a program 930. The TX / RX 940 is used for bidirectional communication. The TX / RX 940 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 required 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 an eNB, an 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.

[0175] The program 930 is assumed to include program instructions that, when executed by the associated processor 910, enable the device 900 to operate according to embodiments of the present disclosure, as described herein with reference to Figures 2-8. The embodiments herein may be implemented by computer software executable by the processor 910 of the device 900, by hardware, or by a combination of software and hardware. The processor 910 may be configured to implement various embodiments of the present disclosure. Furthermore, the combination of the processor 910 and the memory 920 may form a processing means 950 suitable for implementing various embodiments of the present disclosure.

[0176] Memory 920 may be of any type suitable for a local technology network and may be implemented using any suitable data storage technology, including, by way of non-limiting example, non-transitory computer-readable storage media, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. While only one memory 920 is shown in device 900, several physically distinct memory modules may be present within device 900. Processor 910 may be of any type suitable for a local technology network and may include, by way of non-limiting example, one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 900 may have multiple processors, for example, application-specific integrated circuit chips time-slaved to a clock that synchronizes the main processor.

[0177] Components included in the devices and / or apparatus of the present disclosure may be implemented in various ways, 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, machine-executable instructions, some or all of the units in the devices and / or apparatus may be implemented, at least in part, 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 general purpose products (ASSPs), systems on chips (SOCs), complex programmable logic devices (CPLDs), etc.

[0178] Overall, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, 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. While various aspects of embodiments of the present disclosure have been 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, special purpose circuits or logic, general purpose hardware or controller or other computing device, or any combination thereof.

[0179] 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 execute within a device on a target real or virtual processor to perform a process or method described above with reference to any one of FIGS. 2 through 8. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or split between program modules as desired. The machine-executable instructions of the program modules may be executed within local or distributed devices. In a distributed device, program modules may be located in both local and remote storage media.

[0180] Program code for carrying out the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, and when executed by the processor or controller, cause the program code to implement the functions / acts specified in the flowcharts and / or block diagrams. The program code may run entirely on the machine, partially on the machine, as a separate software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0181] The above-described program code may be embodied on a machine-readable medium, which may be any tangible medium that can contain or store a program used by or associated with an instruction execution system, apparatus, or device. 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 aforementioned media. More specific examples of a 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 disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0182] Although operations have been described in a particular order, it should not be understood that performing these operations in the particular order shown, or in any sequential order, or performing all of the operations described, is required to achieve desirable results. In some cases, multitasking or parallel processing may be advantageous. Similarly, although details of several specific embodiments are included in the above discussion, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features that may be unique to particular embodiments. Some features described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination.

[0183] Although the present disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the present disclosure, as 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 example forms of implementing the claims.

Claims

1. A user equipment (UE), means for transmitting a Sidelink (SL) transmission including a Physical Sidelink Shared Channel (PSSCH); means for supporting a contention window adjustment procedure for said SL transmission; Equipped with The contention window adjustment procedure is performed by adjusting the priority class (CW ｐ ) and the value of the contention window for the CW ｐ is used for the channel access procedure for the SL transmission, If the SL transmission is associated with a sidelink Hybrid Automatic Repeat Request (HARQ) feedback, the contention window adjustment procedure is based on the sidelink HARQ feedback, the contention window adjustment procedure is configured to determine whether a first condition is met when the sidelink transmission is associated with the sidelink HARQ feedback and the sidelink transmission is a groupcast sidelink transmission; and the first condition relates to a ratio between a number of ACKs in the sidelink HARQ feedback and a number of one or more UEs in a groupcast. User equipment.

2. the contention window adjustment procedure is configured to determine whether a second condition is met if the sidelink transmission is associated with the sidelink HARQ feedback and the sidelink transmission is a unicast sidelink transmission. The user device of claim 1 .

3. the second condition relates to a number of ACKs in the sidelink HARQ feedback and a number of NACKs in the sidelink HARQ feedback.

3. The user device of claim 2.

4. The contention window adjustment procedure adjusts the CW based on the priority class when the SL transmission is not associated with sidelink Hybrid Automatic Repeat Request (HARQ) feedback. ｐ It is set to adjust the value of 3. A user device according to claim 1 or 2.

5. the user equipment is configured to perform the channel access procedure; 3. A user device according to claim 1 or 2.

6. 1. A method for a user equipment (UE), comprising: transmitting a Sidelink (SL) transmission including a Physical Sidelink Shared Channel (PSSCH); and supporting a contention window adjustment procedure for the SL transmission; Including, The contention window adjustment procedure is performed by adjusting the priority class (CW ｐ ) and the value of the contention window for the CW ｐ is used for the channel access procedure for the SL transmission, If the SL transmission is associated with a sidelink Hybrid Automatic Repeat Request (HARQ) feedback, the contention window adjustment procedure is based on the sidelink HARQ feedback, the contention window adjustment procedure is configured to determine whether a first condition is met when the sidelink transmission is associated with the sidelink HARQ feedback and the sidelink transmission is a groupcast sidelink transmission; and the first condition relates to a ratio between a number of ACKs in the sidelink HARQ feedback and a number of one or more UEs in a groupcast. method.

7. the contention window adjustment procedure is configured to determine whether a second condition is met if the sidelink transmission is associated with the sidelink HARQ feedback and the sidelink transmission is a unicast sidelink transmission. The method of claim 6.

8. the second condition relates to a number of ACKs in the sidelink HARQ feedback and a number of NACKs in the sidelink HARQ feedback. The method of claim 7.

9. The contention window adjustment procedure adjusts the CW based on the priority class when the SL transmission is not associated with sidelink Hybrid Automatic Repeat Request (HARQ) feedback. ｐ It is set to adjust the value of 8. The method according to claim 6 or 7.

10. the user equipment is configured to perform the channel access procedure; 8. The method according to claim 6 or 7.

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