Enhancements on sidelink in unlicensed bands

Abstract

Embodiments of the present disclosure relate to enhanced methods, devices, apparatuses, and computer readable media on sidelink in unlicensed bands. The method includes transmitting, at a first device, a target transmission to a second device via a sidelink channel occupied by applying a contention window of a first contention window size (CWS), receiving, from the second device, non-acknowledgement feedback for the target transmission, and determining a second CWS to be used for the contention window based on acknowledgement and non-acknowledgement feedback associated with a plurality of transmissions preceding the target transmission. In this way, both intra-SL and inter-system collisions are considered when a sidelink UE adjusts the CWS. In this way, a sidelink UE can determine the CWS based not only on detection of sidelink transmission failures but also on evaluation of ACK / NACK feedback for various sidelink transmissions.

Description

Technical Field

[0001] Embodiments of this disclosure generally relate to the telecommunications field, and more particularly to devices, methods, apparatuses, and computer-readable storage media for enhancement on sidechains in unlicensed frequency bands (SL-U). Background Technology

[0002] In unlicensed frequency bands below 7 GHz, the Listen-Before-Speak (LBT) channel access mechanism ensures the coexistence of new radios (NRs) with other systems (e.g., IEEE 802.11). To pass the LBT check, the UE considers the channel available for a certain number of Continuous Clear Channel Assessment (CCA) slots. For example, in unlicensed frequency bands below 7 GHz, the duration of these slots can be 9 μs. If the measured power (i.e., the energy collected during the CCA slots) is below a regulatory threshold (which can vary depending on the operating frequency band and geographic area), the UE can consider the channel available.

[0003] Before initiating communication (i.e., the UE acts as the initiating device), the UE must acquire the "right" to access the channel for a certain period of time (i.e., Channel Occupancy Time (COT)) by applying an "extended" LBT procedure. During this "extended" LBT procedure, the channel must be considered idle for the entire duration of the contention window (CW). This extended LBT procedure is commonly referred to as Channel Access Type 1. Typically, the size of the CW (also known as the CWS) is not fixed but can be increased when a non-acknowledgment (NACK) feedback is received. However, in cases where a sidelink system and a Wi-Fi system coexist in an unlicensed frequency band, sidelink transmission failures may be due to intra-system or inter-system conflicts. Therefore, it is necessary to consider the causes of sidelink transmission failures to improve the regulation of the CWS. Summary of the Invention

[0004] Overall, the example embodiments of this disclosure provide a solution for contention window size (CWS) adjustment for SL-U.

[0005] In a first aspect, a first device is provided. The first device includes: at least one processor; and at least one memory including computer program code. The at least one memory and the computer program code are configured, together with the at least one processor, to cause the first device to: transmit a target transmission to a second device via a sidechain channel occupied by a contention window applying a first contention window size (CWS); receive unacknowledged feedback from the second device for the target transmission; and determine a second CWS to be used for the contention window based on acknowledgment and unacknowledged feedback for a plurality of transmissions preceding the target transmission.

[0006] In a second aspect, a method is provided. The method includes: at a first device, transmitting a target transmission to a second device via a sidechain channel occupied by a contention window of a first contention window size (CWS); receiving unacknowledged feedback from the second device for the target transmission; and determining a second CWS to be used for the contention window based on acknowledgment and unacknowledged feedback for a plurality of transmissions preceding the target transmission.

[0007] In a third aspect, a first apparatus is provided. The first apparatus includes: means for transmitting a target transmission to a second apparatus via a sidechain channel occupied by a contention window with a first contention window size (CWS); means for receiving unacknowledged feedback from the second apparatus for the target transmission; and means for determining a second CWS to be used for the contention window based on acknowledgment and unacknowledged feedback for a plurality of transmissions prior to the target transmission.

[0008] In a fourth aspect, a non-transitory computer-readable medium is provided. This non-transitory computer-readable medium includes program instructions for causing a device to perform the method according to the second aspect.

[0009] It should be understood that the summary portion is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0010] Some exemplary embodiments will now be described with reference to the accompanying drawings, in which:

[0011] Figure 1 An example network environment in which example embodiments of this disclosure may be implemented is shown;

[0012] Figure 2 A schematic diagram illustrating the acquisition of COT according to some example embodiments of the present disclosure is shown;

[0013] Figure 3 The diagram illustrates a signaling process for CWS adjustment according to some example embodiments of the present disclosure;

[0014] Figure 4 A flowchart is shown illustrating an example method implemented at a terminal device according to some example embodiments of the present disclosure;

[0015] Figure 5 A simplified block diagram of a device suitable for implementing example embodiments of the present disclosure is shown; and

[0016] Figure 6 A block diagram of an example computer-readable medium according to an example embodiment of the present disclosure is shown.

[0017] Throughout the accompanying drawings, the same or similar reference numerals denote the same or similar elements. Detailed Implementation

[0018] The principles of this disclosure will now be described with reference to some exemplary embodiments. It should be understood that these embodiments are described merely for illustration and to help those skilled in the art understand and implement this disclosure, and do not imply any limitation on the scope of this disclosure. The disclosure described herein can be implemented in various other ways besides those described below.

[0019] In the following description and claims, unless otherwise defined, 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.

[0020] In this disclosure, references to "an embodiment," "embodiment," and "example embodiment," etc., indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment must include that particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a particular feature, structure, or characteristic is described in connection with an embodiment, those skilled in the art will understand that, whether explicitly described or not, combining it with other embodiments to affect such a feature, structure, or characteristic is within the knowledge of those skilled in the art.

[0021] It should be understood that although the terms “first” and “second”, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of the exemplary embodiments, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments. The singular forms “a,” “an,” and “the” used herein also include the plural forms unless the context clearly indicates otherwise. Further understanding is that the terms “comprises,” “comprising,” “has,” “having,” “includes,” and / or “including”, when used herein, specify the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0023] As used in this application, the term "circuit system" may refer to one or more or all of the following:

[0024] (a) Pure hardware circuit implementation (such as implementation using only analog and / or digital circuit systems), and

[0025] (b) A combination of hardware circuitry and software, such as (if applicable):

[0026] (i) A combination of (multiple) analog and / or digital hardware circuits and software / firmware, and

[0027] (ii) Any part of a hardware processor(s) having software (including (multiple) digital signal processors), software, and (multiple) memories, which work together to cause a device (such as a mobile phone or server) to perform various functions, and

[0028] (c) (Multiple) hardware circuits and / or (multiple) processors, such as (multiple) microprocessors or a portion thereof, which require software (e.g., firmware) to operate, but may be absent when operation is not required.

[0029] The definition of "circuit system" applies to all uses of the term in this application, including in any claim. As another example, as used in this application, the term "circuit system" also covers implementations of only hardware circuitry or processors (or processors in general) or portions thereof and their accompanying software and / or firmware. For instance, if applicable to a particular claim element, the term "circuit system" also covers baseband integrated circuits or processor integrated circuits for mobile devices, or similar integrated circuits in servers, cellular network devices, or other computing or network devices.

[0030] As used herein, the term "communication network" refers to a network that conforms to any suitable communication standard, such as NR, LTE, LTE-A (LTE-A-A), Wideband Code Division Multiple Access (WCDMA), High-Speed ​​Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), etc. Furthermore, communication between terminal devices and network devices in a communication network can be performed according to any suitable generation of communication protocol, including but not limited to first-generation (1G), second-generation (2G), 2.5G, 2.75G, third-generation (3G), fourth-generation (4G), 4.5G, fifth-generation (5G), future sixth-generation (6G) communication protocols, and / or any other currently known or future protocols. Embodiments of this disclosure can be applied to various communication systems. Given the rapid development of communication, future types of communication technologies and systems may also embody this disclosure. The scope of this disclosure should not be limited to the systems described above.

[0031] As used herein, the term "network device" refers to a node in a communication network through which terminal devices access the network and receive services. A network device can refer to a base station (BS) or access point (AP), such as a Node B (NodeB or NB), an evolved Node B (eNodeB or eNB), an NR next-generation Node B (gNB), a remote radio unit (RRU), a radio header (RH), a remote radio header end (RRH), an integrated access and backhaul (IAB) node, a relay, a low-power node (such as a femtosecond, picosecond), etc., depending on the terminology and technology applied. It is permissible to define a network device as part of a gNB, for example, in a centralized unit / distributed unit (CU / DU) split, in which case the network device is defined as gNB-CU or gNB-DU.

[0032] The term "terminal device" refers to any terminal device capable of wireless communication. By way of example and not limitation, a terminal device may also be referred to as a communication device, user equipment (UE), subscriber station (SS), portable subscriber station, mobile station (MS), or access terminal (AT). Terminal devices can include, but are not limited to, mobile phones, cellular phones, smartphones, Voice over IP (VoIP) phones, wireless local loop phones, tablets, wearable terminal devices, personal digital assistants (PDAs), portable computers, desktop computers, image capture terminal devices (such as digital cameras), gaming terminal devices, music storage and playback devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEE), laptop in-vehicle devices (LME), USB dongles, smart devices, wireless customer premises equipment (CPE), Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in the context of industrial and / or automated processing chains), consumer electronics devices, devices operating on commercial and / or industrial wireless networks, etc. In the following description, the terms "terminal equipment", "communication equipment", "terminal", "user equipment" and "UE" are used interchangeably.

[0033] In Wi-Fi, a CW (Concurrent Wear) adjustment mechanism is introduced to derive the backoff time to be applied before a Wi-Fi node can perform its transmission. This mechanism helps avoid potential collisions between Wi-Fi nodes. In a Wi-Fi system, the CW is initially set to a minimum value, CWmin, and it doubles whenever a collision occurs or is detected. After a successful transmission without any collisions, or when the maximum CW value, CWmax, is reached, the CW is reset to CWmin. In other words, the CW size (CWS) is adjusted based on collisions.

[0034] In NR-U, a similar principle of CW size (CWS) adjustment is implemented, with the aim of minimizing inter-system conflicts in unlicensed frequency bands (i.e., conflicts between NR-U systems and Wi-Fi systems). The CWS adjustment design principles adopted in NR-U are as follows:

[0035] • Based on feedback such as HARQ-ACK / NACK, when a collision is detected, increase

[0036] Add CWS;

[0037] • Furthermore, based on HARQ-ACK / NACK feedback, the value is reset to the minimum CWS whenever a transmission is successful.

[0038] In NR-U, SL communication between UEs via PC5 is based on the principle of a one-to-many broadcast transmitter (also known as a transport UE or Tx UE). NR SL supports all propagation types, including unicast, multicast, or broadcast.

[0039] SL transmission has two resource allocation (RA) modes, referred to as Mode 1 and Mode 2. In Mode 1, the resources or grants for transmission are scheduled by the serving base station (BS), therefore, the SL Tx UE operates in the RRC_CONNECTED state. This means that there are almost no intra-SL system conflicts. In Mode 2, the SL Tx UE autonomously selects resources from a resource pool pre-configured by the network. Resource selection in Mode 2 can be based on simple random selection or sensing-based selection, including full sensing or partial sensing for power saving purposes. Mode 2 can be used for Tx UEs in the RRC_CONNECTED, RRC_IDLE, or RRC_INACTIVE states, whether in coverage (IC) or out of coverage (OoC), without coordinating resource allocation from the BS. However, resource selection conflicts from neighboring SL Tx UEs can occur in Mode 2, especially in high-density scenarios.

[0040] In NR SL unicast and multicast, HARQ-based SL retransmission is designed so that the SL Tx UE can know the reception status at the SL Rx UE. The SL Tx UE can then determine whether the SL needs to be retransmitted. Furthermore, NR SL also supports blind retransmission without HARQ feedback. The SL Tx UE can indicate that HARQ feedback is required in the second phase of the SL control information (SCI). For SL multicast, two HARQ feedback options are supported:

[0041] • In SL multicast HARQ option 1, SL Rx UEs within the range of SL Tx UEs will send HARQ-NACK feedback if they successfully decode the SCI but fail to decode the data payload. Otherwise, the SL Rx UE will not transmit any feedback. In this option, the SL Rx UE sending HARQ-NACK feedback will use the common / shared physical sidechain shared channel (PSFCH) resource.

[0042] • In SL multicast HARQ option 2, the SL Rx UE sends HARQ-ACK feedback (e.g., if it successfully decodes the PSCCH and PSSCH) or HARQ-NACK feedback (e.g., if it successfully decodes the SCI but fails to decode the data payload), or does not transmit feedback at all (e.g., if it does not detect / decode the SCI). In this option, each SL Rx UE sends its feedback via a dedicated PSFCH resource.

[0043] As mentioned earlier, it is assumed that a collision is detected based on the received HARQ-ACK / NACK feedback, which can then trigger CWS conditioning. In Wi-Fi systems, CWS conditioning is performed based on the principle that reception failure is due to collisions with other Wi-Fi nodes. Therefore, CWS conditioning can be used as a distributed channel access load balancing mechanism because there is no central resource coordination in Wi-Fi. In NR-U systems, CWS conditioning is mainly used as an inter-system channel access load balancing mechanism, for example, between Wi-Fi and NR-U. This is because all NR-U transmissions are controlled by the network, thus eliminating the need for such a distributed channel access mechanism. In other words, the role of the CWS conditioning mechanism in NR-U is primarily for coexistence with Wi-Fi channels.

[0044] When operating in SL resource allocation mode 2, conflicts are expected when the SL UE autonomously selects resources from the (pre)configured resource pool. Therefore, when a HARQ-NACK is received from the SL Rx UE, it is preferable to determine whether this failure in unlicensed band SL (SL-U) transmission is due to a conflict within the SL-U system or a conflict with other unlicensed band users outside the SL-U system (e.g., Wi-Fi). Intra-system SL conflicts can be handled using existing SL mechanisms, while inter-system conflicts can be handled via CWS conditioning mechanisms. Therefore, in SL-U, it is necessary to distinguish between intra-system and inter-system conflicts.

[0045] Figure 1An example network environment 100 in which exemplary embodiments of the present disclosure may be implemented is shown. Network environment 100 may include a first device 110, second devices 120 and 122, a third device 130, a fourth device 140, and a network node 102. (As...) Figure 1 As shown, the first device 110, the second devices 120 and 122, the third device 130, and the fourth device 140 can be implemented as terminal devices, such as UEs, which may also be referred to hereinafter as UEs 110 to 140 or terminal devices 110 to 140. The network node 102 can be implemented as a Wi-Fi node, or any other node using different wireless communication technologies in an unlicensed frequency band, which may also be referred to hereinafter as Wi-Fi node 102.

[0046] By autonomously selecting resources from the pre-configured resource pool 104, the first device 110, the second devices 120 and 122, and the third device 130 can communicate with each other via a sidechain channel. In other words, the first device 120, the second devices 120 and 122, and the third device 130 are in an NR SL-U system. The first device 110 can transmit services to the second devices 120 and 122 in multicast mode. Alternatively, the first device 110 can also transmit services to each of the second devices 120 and 122 in unicast mode.

[0047] The fourth device 140 and the network device 102 can communicate based on, for example, the 802.11 protocol. For example, the network device 102 is a Wi-Fi node, and the fourth device 140 and the network device 102 are in a Wi-Fi system.

[0048] As mentioned earlier, before initiating any transmission, the initiating device needs to acquire the "right" to access the channel of the COT. For this purpose, a channel access procedure can be performed. Typically, there are two types of channel access procedures: Channel Access Type 1 with random backoff and Channel Access Type 2 with a single Clear Channel Assessment (CCA).

[0049] The initiating device can apply the extended LBT procedure corresponding to channel access type 1. Figure 2 A schematic diagram illustrating COT acquisition according to some example embodiments of this disclosure is shown. For example... Figure 2 As shown, the first device 110 can observe the channel during CW 201, and if the channel is considered idle for the entire duration of CW 201, the first device 110 is allowed to access the channel during COT 202.

[0050] For example, the duration of both COT and CW can depend on the Channel Access Priority Class (CAPC) associated with the service of the first device 110, as shown in Table 1. Control plane services (such as transmissions on the PSCCH) are transmitted with p=1, while user plane services are transmitted with p>1. Table 1 shows the details of Channel Access Type 1 in the Uu uplink (UL) case. It should be understood that the Channel Access Type 1 parameters in the Uu downlink (DL) case can also be used in NR SL-U in principle.

[0051] Table 1. Parameters for Channel Access Type 1 in UL Case

[0052]

[0053]

[0054] In conventional CWS adjustment mechanisms, such as in NR-U, the CWS value can be increased to the next allowed CWS or reset to the minimum CWS value, depending on the detection of a HARQ-NACK indicating transmission failure or a HARQ-ACK indicating successful transmission. However, transmission failures in SL-U can be due to various reasons and / or different types of collisions.

[0055] Refer again Figure 1 When the first device 110 transmits services to the second devices 120-122, there may be conflicts from the third device 130 (i.e., intra-system conflicts due to autonomous resource selection) and conflicts from the fourth device 140 (e.g., inter-system conflicts). Both types of conflicts can lead to transmission failure on the Rx UE side. However, these two types of conflicts can be handled differently. For example, intra-system conflicts can be handled using existing SL mechanisms, while inter-system conflicts can be handled via CWS adjustment mechanisms. According to an example embodiment, the initiating UE can analyze sidechain communication characteristics to distinguish between the two types of conflicts and determine whether and how to adjust the CWS accordingly.

[0056] In some example embodiments, sidechain communication characteristics can be reflected by the HARQ-ACK / NACK feedback received by the first device 110. For example, the first device 110 can transmit an SCI on the PSCCH to indicate SL resources not only for the current SL transmission but also for SL retransmissions and / or future periodic SL transmissions. Indicating reserved resources for SL retransmissions and future periodic SL transmissions can reduce the rate of intra-system collisions due to full or partial sensing based on the SL mode 2RA scheme. Therefore, the intra-system collisions experienced by the initial SL transmission can differ for SL retransmissions or any upcoming periodic SL transmission within the NR SL-U system. On the other hand, the SCI cannot provide such an indication to the UE (such as the fourth device 140) in a Wi-Fi system. Therefore, the inter-system collisions experienced by the initial SL transmission can be similar to the inter-system collisions experienced by the SL retransmission. Therefore, the first device 110 can adjust the CWS based on the main cause / origin of the transmission failure, for example, by increasing or decreasing the CWS or keeping the CWS unchanged, which will be discussed in detail below.

[0057] It should be understood that Figure 1 The number of devices shown and Figure 2 The durations of CW and COT shown are for illustrative purposes only and do not imply any limitations. For example, network environment 100 may include any suitable number of terminal devices and network devices suitable for implementing embodiments of this disclosure. This disclosure is not limited thereto.

[0058] Communication in network environment 100 can conform to any suitable standard, including but not limited to NR, LTE, LTE evolution, LTE-A Advanced, Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), and Global System for Mobile Communications (GSM). Furthermore, communication can be performed according to any generation of communication protocols currently known or to be developed in the future. 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, fifth generation (5G), future sixth generation (6G), and / or any other communication protocol.

[0059] The following will be referenced Figure 3 The principles and implementation of this disclosure are described in detail. Figure 3 Signaling diagrams of a CWS conditioning process 300 according to some example embodiments of the present disclosure are shown. Reference will be made to these diagrams for discussion purposes. Figure 1 Describe process 300. Process 300 may involve a first device 110, a second device 120-122, a third device 130, and a fourth device 140.

[0060] In process 300, the first device 110 can communicate with the second devices 120 and 122 (not shown for simplicity) in unicast or multicast mode. Furthermore, sidechain retransmission based on HARQ feedback is implemented.

[0061] The first device 110 can evaluate the reception status of multiple transmissions previously transmitted to the second devices 120 and 122. The multiple transmissions can be various sidechain transmissions, including but not limited to the initial transmission of a transport block (TB), retransmission of a TB, the initial transmission of a periodic service, the initial transmission of an aperiodic service, etc.

[0062] In order to obtain sufficient reception status for evaluation, the first device 110 may collect HARQ-ACK / NACK feedback for sidechain transmissions over a certain period of time, or accumulate HARQ-ACK / NACK feedback for a certain number of sidechain transmissions.

[0063] For example, the first device 110 may evaluate HARQ-ACK / NACK feedback for sidechain transmissions within a specific time window (e.g., the SL mode 2 sensing window or the backoff time corresponding to the current CWS value). Alternatively, the first device 110 may evaluate HARQ-ACK / NACK feedback for a certain number of previous SL transmissions, and this number may be (pre)configured at the first device 110.

[0064] The first device 110 can access the 310 sidechain channel by performing an LBT procedure based on the current CWS (i.e., the first CWS).

[0065] The first device 110 transmits the target transmission 315 to the second device 120 via a sidechain channel (such as PSCCH and PSSCH).

[0066] However, decoding of the target transmission fails at the second device 120 320. Therefore, the second device 120 transmits 325 a HARQ-NACK feedback for the target transmission to the first device 110.

[0067] Upon receiving HARQ-NACK feedback for the target transmission, the first device 110, based on its evaluation of the HARQ ACK / NACK feedback for the previous sidechain transmission at 305, determines that 330 is to be used as the second CWS for CW. It should be understood that, although in Figure 3 In this example, the evaluation is shown to be performed at the beginning of process 300, but it can also be performed in a flexible manner. For example, in some other example embodiments, the first device 110 may evaluate the reception status of previous sidechain transmissions between steps 310 and 315, between steps 315 and 320, between steps 320 and 325, or between steps 325 and 330.

[0068] As described above, the SL Tx UE can indicate reserved resources for SL retransmission in the first-stage SCI of the SL initial transmission. The indicated resources for SL retransmission can be sensed by other nearby SL UEs. Therefore, other SL UEs will avoid selecting the same resources in SL RA Mode 2, resulting in a lower intra-system collision rate for SL retransmissions compared to the SL initial transmission. In contrast, since non-SL devices (e.g., the fourth device 140) cannot decode the SCI, the inter-system collision rate between the SL initial transmission and SL retransmissions is not expected to differ significantly. In this case, the evaluation of HARQ-ACK and HARQ-NACK for the SL initial transmission and retransmissions can be used to detect whether the SL transmission failure is due to collisions within the SL-U system or collisions from other unlicensed band users.

[0069] In some example embodiments, the first device 110 can evaluate HARQ-ACK / NACK feedback for at least one initial transmission and HARQ-NACK feedback for at least one retransmission via a sidechain channel. For example, the first device 110 can determine a first ratio associated with the HARQ-ACK and HARQ-NACK feedback for at least one initial transmission. Similarly, the first device 110 can determine a second ratio associated with the HARQ-ACK and HARQ-NACK feedback for at least one retransmission. The first device 110 can then determine a variation from the first ratio to the second ratio. In this case, ACK or NACK feedback from different SL multicast Rx UEs (i.e., the second devices 120 and 122) is used to evaluate the reception status of the SL initial transmission and retransmission.

[0070] For example, if the SL transmission failure is primarily caused by collisions from other unlicensed band users (i.e., inter-system collisions) rather than from other SL-U users (i.e., intra-system collisions), the HARQ-ACK / NACK feedback ratios for the initial SL transmission and retransmissions can be the same or similar. In this case, the size of the CWS can increase in response to a HARQ-NACK received at 325. That is, the value of the second CWS can be determined as the next higher CWS value compared to the value of the first CWS. Note that in the case where the transmission failure is due to inter-system collisions, it is also expected that non-SL devices (i.e., the fourth device 140) will also apply CWS conditioning.

[0071] However, if the ratio of HARQ-ACK / NACK feedback for initial transmission and retransmission of SL changes relatively significantly, for example, greater than the change threshold (pre-)configured at the first device 110, the size of CW can remain unchanged or decrease even when HARQ-NACK feedback is received. In this case, the value of the second CWS is less than or equal to the value of the first CWS.

[0072] In some example embodiments of soft combining used for SL retransmission, transmission failures are mitigated even when inter-system collisions are the primary cause. Therefore, when evaluating the ratio of HARQ-ACK / NACK feedback for initial SL transmissions and retransmissions, more than one variation threshold can be considered, depending on whether soft combining is configured. Without soft combining, a lower variation threshold can be used to determine the second CWS, as described above. When soft combining is configured, a higher variation threshold can be used to determine the second CWS because soft combining itself affects the ratios associated with HARQ-ACK and HARQ-NACK feedback for initial transmissions and retransmissions.

[0073] In some example embodiments, the first ratio and the second ratio may be the corresponding ratio of HARQ-ACK feedback to HARQ-NACK feedback. In some other example embodiments, the first ratio and the second ratio may be the corresponding ratio of HARQ-NACK feedback to HARQ-ACK feedback.

[0074] Alternatively, the SL Tx UE can indicate reserved resources for upcoming periodic SL transmissions in the first-phase SCI of an early SL transmission. The indicated resources for upcoming periodic SL transmissions can be sensed by other nearby SL UEs. Therefore, other SL UEs will avoid selecting the same resources in SL RA Mode 2, resulting in a lower intra-system collision rate for upcoming periodic SL transmissions. However, for non-periodic services, no resource reservation indication for upcoming new SL transmissions is provided in the SCI. In this case, the evaluation of HARQ-ACK and HARQ-NACK for the initial SL transmissions of both periodic and non-periodic services can be used to detect whether the SL transmission failure is due to collisions within the SL-U system or due to collisions from other unlicensed band users.

[0075] For example, if the SL transmission failure is primarily caused by intra-system collisions, the third ratio associated with the HARQ-ACK and HARQ-NACK feedback of the initial SL transmission for periodic services and the fourth ratio associated with the HARQ-ACK and HARQ-NAK feedback of the initial SL transmission for non-periodic services can be different. In this case, the size of CWS can remain unchanged or decrease even when HARQ-NACK feedback is received. Therefore, the value of the second CWS is less than or equal to the value of the first CWS.

[0076] On the other hand, if the SL transmission failure is primarily caused by inter-system collisions, the third ratio associated with the HARQ-ACK and HARQ-NACK feedback of the initial SL transmission for periodic services and the fourth ratio associated with the HARQ-ACK and HARQ-NAK feedback of the initial SL transmission for non-periodic services can be the same or similar. Therefore, when the SL Tx UE receives a HARQ-NACK, the size of the CWS can increase in response to the HARQ-NACK received at 325. For example, the value of the second CWS can be determined as the next higher CWS value compared to the value of the first CWS.

[0077] In some example embodiments, the third and fourth ratios may be corresponding ratios of HARQ-ACK feedback to HARQ-NACK feedback. In some other example embodiments, the third and fourth ratios may be corresponding ratios of HARQ-NACK feedback to HARQ-ACK feedback.

[0078] In some embodiments of discontinuous transmission (DTX) feedback (i.e., neither HARQ-ACK nor HARQ-NACK is fed back from the SLRx UE), it can be considered as HARQ-NACK feedback. Alternatively, DTX feedback can be configured with a weighting factor for being counted as HARQ-ACK feedback. In the latter case, the weighting factor for DTX feedback can be selected from 0.5 and 1.5, meaning that a DTX with a weighting factor of 0.5 can be considered half of a HARQ-NACK, or a DTX with a weighting factor of 1.5 can be considered one half of a HARQ-ACK.

[0079] The first device 110 may select a weighting factor to use from a set of candidate weighting factors. In some example embodiments, the set of candidate weighting factors (e.g., 0.5 and 1.5) and / or the corresponding conditions for using each weighting factor may be (pre)configured at the first device 110 or specified in relevant standards. In some example embodiments, the weighting factor may be selected based on a (pre)configured rule associated with a reference signal received via a sidechain channel. For example, the rule may be associated with a measurement parameter of the reference signal (such as SL RSRP). The first device 110 may monitor the SL RSRP, and if the SL RSRP exceeds a parameter threshold, the first device 110 may select a first weighting factor (e.g., 0.5) from the set of candidate weighting factors. Otherwise, if the SL RSRP does not exceed the parameter threshold, the first device 110 may select a second weighting factor (e.g., 1.5) from the set of candidate weighting factors. In this case, any one of the measurement parameter, the rule associated with the reference signal, and the parameter threshold may be (pre)configured at the first device 110 or specified in relevant standards. This application is not limited thereto.

[0080] In some embodiments, the CWS conditioning mechanism may not apply to all HARQ NACKs for each SL transmission or retransmission. For example, only a HARQ-NACK corresponding to the first SL transmission within the COT may trigger CWS conditioning. HARQ feedback for subsequent SL transmissions (initial transmissions or retransmissions) within the COT may not trigger CWS conditioning. Alternatively, only a HARQ-NACK corresponding to the last SL retransmission of the TB (e.g., TB transmission failure) may trigger CWS conditioning, rather than a HARQ-ACK corresponding to any SL initial transmission or SL retransmission prior to the last SL retransmission.

[0081] According to an example embodiment, an enhancement mechanism for CWS adjustment is provided. Based on the enhancement mechanism, the sidechain UE considers both intra-system and inter-system conflicts when determining CWS. Therefore, CWS is adjusted not only based on the detection of transmission failures via the sidechain but also based on the evaluation of ACK / NACK feedback from various sidechain transmissions.

[0082] Figure 4 A flowchart of an example method 400 implemented at a terminal device is shown. Method 400 can be implemented by a terminal device that acts as an initiating device or a transmitting UE, for example, Figure 1 The first device 110 is shown. For discussion purposes, reference will be made to... Figure 1 Method 400 is described. It should be understood that method 400 may also include additional blocks not shown and / or omit some blocks shown, and the scope of this disclosure is not limited thereto.

[0083] At 410, the first device 110 transmits the target transmission to the second device 120 via the sidechain channel occupied by the CW using the first CWS.

[0084] At 420, the first device 110 receives unacknowledged feedback for the target transmission from the second device 120. The unacknowledged feedback may be, for example, a HARQ-NACK feedback.

[0085] At 430, the first device 110 determines the second CWS to be used for the CW based on acknowledgment and non-acknowledgment feedback for multiple transmissions preceding the target transmission. These multiple transmissions may include, but are not limited to, initial transmissions / retransmissions, initial transmissions for periodic services, and initial transmissions for non-periodic services.

[0086] The second CWS can be determined based on ratio parameters associated with HARQ feedback for initial transmissions and retransmissions. In some example embodiments, the first device 110 can determine a first ratio associated with acknowledgment and non-acknowledgment feedback for at least one initial transmission via a sidechain channel. The first device 110 can determine a second ratio associated with acknowledgment and non-acknowledgment feedback for at least one retransmission via a sidechain channel. The first device 110 can then determine the second CWS based on the change from the first ratio to the second ratio.

[0087] Multiple transmissions preceding the target transmission can be transmitted in multicast mode via a sidechain channel, in which case acknowledgment and unacknowledgment feedback can be received from a group of devices associated with the multicast mode. For example, this group of devices could be a second group of devices 120 and 122.

[0088] In some example embodiments, the first device 110 may determine a third ratio associated with acknowledgment and non-acknowledgment feedback for at least one initial transmission of a periodic service of the first device 110. The first device 110 may determine a fourth ratio associated with acknowledgment and non-acknowledgment feedback for at least one initial transmission of an aperiodic service of the first device 110. Similarly, the first device 110 may then determine a second CWS based on the change from the third ratio to the fourth ratio.

[0089] In some example embodiments, if the change exceeds a change threshold, the first device 110 may determine that the unacknowledged feedback of the target transmission is caused by a collision with at least one third device (e.g., third device 130) operating on a sidechain channel in an unlicensed frequency band. That is, the sidechain transmission failure is primarily due to intra-system collisions. Otherwise, if the change does not exceed the change threshold, the first device 110 may determine that the unacknowledged feedback of the target transmission is caused by a collision with at least one fourth device (e.g., fourth device 140) operating on a channel other than the sidechain channel in an unlicensed frequency band. In this case, the sidechain transmission failure is primarily due to inter-system collisions.

[0090] In the above embodiments, the first device 110 can compare the change with a change threshold that can be (pre-)configured at the first device 110. If the change exceeds the change threshold, the first device 110 can determine that the second CWS is not greater than the first CWS. For example, the second CWS can be less than the first CWS. For another example, the second CWS can be equal to the first CWS, that is, the duration of CW remains unchanged. Otherwise, if the change does not exceed the change threshold, the first device 110 can determine that the second CWS is greater than the first CWS. For example, the second CWS can be set as the next higher allowed value of CW.

[0091] The change threshold can be selected from a set of candidate thresholds. In some example embodiments, if multiple transmissions prior to the target transmission are received based on soft combining, the first device 110 can select a first change threshold from the set of candidate thresholds to evaluate the change. Otherwise, if multiple transmissions prior to the target transmission are not received based on soft combining, the first device 110 can select a second change threshold from the set of candidate thresholds, and the second change threshold is different from the first change threshold.

[0092] In some example embodiments, the first ratio and the second ratio may include corresponding ratios of acknowledgment feedback and non-acknowledgment feedback. For example, the first ratio may be the ratio of ACK / NACK feedback for the initial transmission, while the second ratio may be the ratio of ACK / NACK feedback for retransmissions.

[0093] In some example embodiments, the first ratio and the second ratio may include the corresponding ratio of non-acknowledgment feedback to acknowledgment feedback. For example, the first ratio may be the ratio of NACK / ACK feedback for the initial transmission, while the second ratio may be the ratio of NACK / ACK feedback for retransmissions.

[0094] In some example embodiments, the third and fourth ratios may include corresponding ratios of acknowledgment feedback to non-acknowledgment feedback. For example, the third ratio may be the ratio of ACK / NACK feedback for the initial transmission of a periodic service, while the fourth ratio may be the ratio of ACK / NACK feedback for the initial transmission of an aperiodic service.

[0095] In some example embodiments, the third and fourth ratios may include corresponding ratios of non-acknowledgment feedback to acknowledgment feedback. For example, the third ratio may be the ratio of NACK / ACK feedback for the initial transmission of a periodic service, while the fourth ratio may be the ratio of NACK / ACK feedback for the initial transmission of an aperiodic service.

[0096] In some example embodiments, multiple transmissions preceding the target transmission may be performed within a target time period, which is associated with one of the following: a sensing window configured for the first device 110, and a backoff time corresponding to the first CWS. Alternatively or additionally, the multiple transmissions preceding the target transmission may include a predetermined number of prior transmissions. This number of prior transmissions may be pre-configured at the first device 110 or specified in relevant standards. This application is not limited thereto.

[0097] Unacknowledged feedback for multiple transmissions may include at least one discontinuous transmission DTX feedback, and the number of at least one DTX feedback may be determined based on a weighting factor. In some example embodiments, a set of candidate weighting factors is (pre)configured at the first device 110, and the first device 110 may select weighting factors from the set of candidate weighting factors based on (pre)configuration rules associated with a reference signal received via the sidechain channel.

[0098] In some example embodiments, to select a weighting factor, the first device may determine the measurement parameters of the reference signal. If the measurement parameters of the reference signal exceed a parameter threshold, the first device 110 may select a first weighting factor from the set of candidate weighting factors. If the measurement parameters of the reference signal do not exceed the parameter threshold, the first device 110 may select a second weighting factor from the set of candidate weighting factors, and the second weighting factor is different from the first weighting factor.

[0099] For example, the measurement parameter of the reference signal could be the RSRP monitored on the sidechain channel. If the RSRP is not higher than a (pre)configured threshold, the first device 110 can select a first weighting factor. If the RSRP is higher than the (pre)configured threshold, the first device 110 can select a second weighting factor. It should be understood that the RSRP is given for illustrative purposes and not as a limitation, and any other measurement parameter is also possible.

[0100] In some example embodiments of unicast transmission, the target transmission may include at least one transmission performed within a COT obtained by applying a contention window of a first CWS.

[0101] In some example embodiments, the first device 110 may be a first terminal device, and the second device 120 may be a second terminal device.

[0102] In some example embodiments, a first means (e.g., first device 110) capable of performing any of the methods 400 may include components for performing the corresponding steps of method 400. These components may be implemented in any suitable form. For example, the components may be implemented as a circuit system or a software module.

[0103] In some example embodiments, the first device includes: components for transmitting a target transmission to a second device via a sidechain channel occupied by a contention window with a first contention window size (CWS); components for receiving unacknowledged feedback from the second device for the target transmission; and components for determining a second CWS to be used for the contention window based on acknowledgment and unacknowledged feedback for a plurality of transmissions prior to the target transmission.

[0104] In some example embodiments, the components for determining the second CWS include: components for determining a first ratio associated with acknowledgment feedback and non-acknowledgment feedback of at least one initial transmission of the transport block via the sidechain channel; components for determining a second ratio associated with acknowledgment feedback and non-acknowledgment feedback of at least one retransmission of the transport block via the sidechain channel; and components for determining the second CWS based on the change from the first ratio to the second ratio.

[0105] In some example embodiments, the plurality of transmissions preceding the target transmission are transmitted in multicast mode via the sidechain channel, and the acknowledgment feedback and the unacknowledgment feedback are received from a group of devices associated with the multicast mode.

[0106] In some example embodiments, the components for determining the second CWS include: components for determining a third ratio associated with acknowledgment feedback and non-acknowledgment feedback of at least one initial transmission of periodic service of the first device; components for determining a fourth ratio associated with acknowledgment feedback and non-acknowledgment feedback of at least one initial transmission of aperiodic service of the first device; and components for determining the second CWS based on the change from the third ratio to the fourth ratio.

[0107] In some example embodiments, the components for determining the second CWS include: components for determining that the second CWS is not greater than the first CWS based on determining that the change exceeds a change threshold; and components for determining that the second CWS is greater than the first CWS based on determining that the change does not exceed the change threshold.

[0108] In some example embodiments, the first apparatus further includes: a component for selecting a first change threshold for evaluating the change from a set of candidate thresholds based on determining that the plurality of transmissions prior to the target transmission were received based on a soft combination; and a component for selecting a second change threshold different from the first change threshold from the set of candidate thresholds based on determining that the plurality of transmissions prior to the target transmission were not received based on a soft combination.

[0109] In some example embodiments, the first device further includes components for: determining, based on determining that the change exceeds the change threshold, that the unacknowledged feedback of the target transmission is caused by a conflict with at least one third device operating on the sidechain channel in an unlicensed frequency band; and determining, based on determining that the change does not exceed the change threshold, that the unacknowledged feedback of the target transmission is caused by a conflict with at least one fourth device operating on a channel other than the sidechain channel in an unlicensed frequency band.

[0110] In some example embodiments, the first ratio and the second ratio include the corresponding ratio of the confirmed feedback to the non-confirmed feedback.

[0111] In some example embodiments, the first ratio and the second ratio include the corresponding ratio of the non-acknowledgment feedback to the acknowledgement feedback.

[0112] In some example embodiments, the third ratio and the fourth ratio include the corresponding ratio of the confirmed feedback to the non-confirmed feedback.

[0113] In some example embodiments, the third ratio and the fourth ratio include the corresponding ratio of the non-acknowledgment feedback to the acknowledgement feedback.

[0114] In some example embodiments, the plurality of transmissions prior to the target transmission are performed within a target time period, which is associated with one of the following: a sensing window configured for the first device, and a fallback time corresponding to the first CWS.

[0115] In some example embodiments, the plurality of transmissions preceding the target transmission include a predetermined number of prior transmissions.

[0116] In some example embodiments, the unacknowledged feedback for multiple transmissions includes at least one discontinuous transmission DTX feedback, and the number of the at least one DTX feedback is determined based on a weighting factor.

[0117] In some example embodiments, the first apparatus further includes a component for selecting the weighting factor from a set of candidate weighting factors based on a pre-configured rule associated with a reference signal received via the sidechain channel.

[0118] In some example embodiments, the components for selecting weighting factors include: components for selecting a first weighting factor from a set of candidate weighting factors based on determining that a measurement parameter of the reference signal exceeds a parameter threshold; and components for selecting a second weighting factor from the set of candidate weighting factors based on determining that the measurement parameter of the reference signal does not exceed the parameter threshold, wherein the second weighting factor is different from the first weighting factor.

[0119] In some example embodiments, the target transmission includes at least one transmission performed within the channel occupancy time (COT) obtained by applying the contention window of the first CWS.

[0120] In some example embodiments, the first device includes a first terminal device, and the second device includes a second terminal device.

[0121] Figure 5 This is a simplified block diagram of a device 500 suitable for implementing embodiments of the present disclosure. Device 500 can be provided to implement a communication device, for example, Figure 1 The first device 110, the second devices 120 and 122, and the third device 130 are shown. As shown, device 500 includes one or more processors 510, one or more memories 520 coupled to processor 510, and one or more transmitters and / or receivers (TX / RX) 540 coupled to processor 510.

[0122] The TX / RX 540 can be configured for bidirectional communication. The TX / RX 540 has at least one antenna to facilitate communication. The communication interface can represent any interface required for communication with other network components.

[0123] Processor 510 can be any type suitable for a local technology network, and by way of non-limiting example, can include one or more of the following: general-purpose computer, special-purpose computer, microprocessor, digital signal processor (DSP), and processor based on a multi-core processor architecture. Device 500 can have multiple processors, such as application-specific integrated circuit chips that are time-dependent on a clock synchronized with the main processor.

[0124] Memory 520 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 524, electrically programmable read-only memory (EPROM), flash memory, hard disk, compact disc (CD), digital video disk (DVD), and other magnetic and / or optical storage media. Examples of volatile memories include, but are not limited to, random access memory (RAM) 522 and other volatile memories that do not persist during power outages.

[0125] Computer program 530 includes computer-executable instructions that can be executed by the associated processor 510. Program 530 can be stored in ROM 524. Processor 510 can perform any suitable actions and processes by loading program 530 into RAM 522.

[0126] The embodiments of this disclosure can be implemented via program 530, enabling device 500 to execute reference... Figure 3 Any process discussed in this disclosure. Embodiments of this disclosure may also be implemented by hardware or a combination of software and hardware.

[0127] In some embodiments, program 530 may be tangibly contained in a computer-readable medium, which may be included in device 500 (such as memory 520) or other storage device accessible to device 500. Device 500 may load program 530 from the computer-readable medium into RAM 522 for execution. The computer-readable medium may include any type of tangible non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Figure 6 An example of a computer-readable medium 600 in the form of a CD or DVD is shown. A program 530 is stored on the computer-readable medium.

[0128] Various embodiments of this disclosure may be implemented using hardware or dedicated circuitry, software, logic, or any combination thereof. Some aspects may be implemented using hardware, while others may be implemented using firmware or software that can be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of this disclosure are illustrated and described as block diagrams, flowcharts, or using some other graphical representation, it should be understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented using hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0129] This 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 a program module, which execute in a device on a target real or virtual processor to perform the above-referenced... Figure 4 Method 400 is described. Typically, a program module may include routines, programs, libraries, objects, classes, components, data structures, etc., that perform a specific task or implement a specific abstract data type. In various embodiments, the functionality of a program module can be combined or split among program modules as needed. The machine-executable instructions of a program module can execute on a local or distributed device. In a distributed device, the program module can reside on both local and remote storage media.

[0130] Program code used to perform the methods of this disclosure may be written in any combination of one or more programming languages. This program code may be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may be executed entirely on a machine, partially on a machine, as a stand-alone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0131] In the context of this disclosure, computer program code or related data may be carried by any suitable carrier to enable a device, apparatus, or processor to perform the various processes and operations described above. Examples of carriers include signals, computer-readable media, etc.

[0132] Computer-readable media can be computer-readable signal media or computer-readable storage media. Computer-readable media can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any suitable combination of the foregoing. More specific examples of computer-readable storage media will include electrical connections having one or more wires, portable computer floppy disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0133] Furthermore, although operations are described in a specific order, this should not be construed as requiring the operations to be performed in the specific order shown or sequentially, or to perform all of the shown operations to obtain the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, while several specific implementation details are included in the foregoing discussion, these should not be construed as limiting the scope of this disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features described in the context of separate 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 individually or in any suitable sub-combination in multiple embodiments.

[0134] Although this disclosure has been described in language specific to structural features and / or methodological actions, it should be understood that this disclosure as defined in the appended claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are disclosed as exemplary forms of implementing the claims.

Claims

1. A first terminal device for communication, comprising: At least one processor; as well as At least one memory, including computer program code; The at least one memory and the computer program code are configured, together with the at least one processor, to cause the first terminal device to at least: The target transmission is transmitted to the second terminal device via the sidechain channel occupied by the contention window of the first contention window size CWS. Receive non-acknowledgment feedback from the second terminal device for the target transmission; as well as Based on acknowledgment and non-acknowledgment feedback for multiple transmissions prior to the target transmission, a second CWS to be used for the contention window is determined; Determining the second CWS includes: Determine a first ratio associated with acknowledgment feedback and non-acknowledgment feedback for at least one initial transmission of a transport block via the sidechain channel; Determine a second ratio associated with acknowledgment and non-acknowledgment feedback for at least one retransmission of the transport block via the sidechain channel; and Determining the second CWS based on the change from the first ratio to the second ratio includes: Based on the determination that the change exceeds a change threshold, it is determined that the second CWS is not greater than the first CWS; and Based on the determination that the change does not exceed the change threshold, the second CWS is determined to be greater than the first CWS.

2. The first terminal device of claim 1, wherein the plurality of transmissions prior to the target transmission are transmitted in multicast mode via the sidechain channel, and the acknowledgment feedback and the unacknowledgment feedback are received from a group of devices associated with the multicast mode.

3. The first terminal device according to claim 1, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the first terminal device to: Determine a third ratio associated with acknowledgment and non-acknowledgment feedback for at least one initial transmission of periodic service with the first terminal device; and A fourth ratio is determined that is associated with acknowledgment feedback and non-acknowledgment feedback for at least one initial transmission of non-periodic services of the first terminal device. The second CWS is further determined based on the change from the third ratio to the fourth ratio.

4. The first terminal device according to claim 1, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, also cause the first terminal device to: Based on the determination that the multiple transmissions prior to the target transmission were received based on soft combination, a first change threshold is selected from a set of candidate thresholds to evaluate the change; and Based on the determination that the multiple transmissions prior to the target transmission were not received based on soft combination, a second change threshold different from the first change threshold is selected from the set of candidate thresholds.

5. The first terminal device according to claim 1, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, also cause the first terminal device to: Based on the determination that the change exceeds the change threshold, it is determined that the unacknowledged feedback for the target transmission is caused by a collision with at least one third device operating on the sidechain channel in an unlicensed frequency band; and Based on the determination that the change did not exceed the change threshold, it was determined that the non-acknowledgment feedback of the target transmission was caused by a conflict with at least one fourth device operating on a channel other than the sidechain channel in an unlicensed frequency band.

6. The first terminal device according to claim 1, wherein the first ratio and the second ratio include the corresponding ratio of the confirmation feedback to the non-confirmation feedback.

7. The first terminal device according to claim 1, wherein the first ratio and the second ratio include the corresponding ratio of the non-acknowledgment feedback to the acknowledgement feedback.

8. The first terminal device according to claim 3, wherein the third ratio and the fourth ratio include the corresponding ratios of the confirmation feedback and the non-confirmation feedback.

9. The first terminal device according to claim 3, wherein the third ratio and the fourth ratio include the corresponding ratios of the non-acknowledgment feedback and the acknowledgement feedback.

10. The first terminal device of claim 1, wherein the plurality of transmissions prior to the target transmission are performed within a target time period, the target time period being associated with one of: a sensing window configured for the first terminal device, and a fallback time corresponding to the first CWS.

11. The first terminal device according to claim 1, wherein the plurality of transmissions prior to the target transmission includes a predetermined number of previous transmissions.

12. The first terminal device of claim 1, wherein the unacknowledged feedback for the plurality of transmissions includes at least one discontinuous transmission DTX feedback, and the number of the at least one DTX feedback is determined based on a weighting factor.

13. The first terminal device of claim 12, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, also cause the first terminal device to: The weighting factor is selected from a set of candidate weighting factors based on pre-configured rules associated with the reference signal received via the sidechain channel.

14. The first terminal device of claim 13, wherein the at least one memory and the computer program code are configured, together with the at least one processor, to cause the first terminal device to select the weighting factor in such a way as: Based on the determination that the measured parameters of the reference signal exceed a parameter threshold, a first weighting factor is selected from the set of candidate weighting factors; and Based on the determination that the measured parameters of the reference signal do not exceed the parameter threshold, a second weighting factor is selected from the set of candidate weighting factors, the second weighting factor being different from the first weighting factor.

15. The first terminal device of claim 1, wherein the target transmission includes at least one transmission performed within the channel occupancy time (COT) obtained by applying the contention window of the first CWS.

16. The first terminal device according to claim 1, wherein the first terminal device includes a first terminal device, and the second terminal device includes a second terminal device.

17. A method for communication in a first terminal device, comprising: At the first terminal device, the target transmission is transmitted to the second terminal device via the sidechain channel occupied by the contention window of the first contention window size CWS. Receive non-acknowledgment feedback from the second terminal device for the target transmission; as well as Based on acknowledgment and non-acknowledgment feedback for multiple transmissions prior to the target transmission, a second CWS to be used for the contention window is determined; Determining the second CWS includes: Determine a first ratio associated with acknowledgment feedback and non-acknowledgment feedback for at least one initial transmission of a transport block via the sidechain channel; Determine a second ratio associated with acknowledgment and non-acknowledgment feedback for at least one retransmission of the transport block via the sidechain channel; and Determining the second CWS based on the change from the first ratio to the second ratio includes: Based on the determination that the change exceeds a change threshold, it is determined that the second CWS is not greater than the first CWS; and Based on the determination that the change does not exceed the change threshold, the second CWS is determined to be greater than the first CWS.

18. A computer-readable medium for communication, comprising program instructions that, when executed by a first terminal device, cause the first terminal device to perform at least the following operations: At the first terminal device, the target transmission is transmitted to the second terminal device via the sidechain channel occupied by the contention window of the first contention window size CWS. Receive non-acknowledgment feedback from the second terminal device for the target transmission; as well as The second CWS to be used for the contention window is determined based on the acknowledgment feedback and non-acknowledgment feedback for multiple transmissions prior to the target transmission; Determining the second CWS includes: Determine a first ratio associated with acknowledgment feedback and non-acknowledgment feedback for at least one initial transmission of a transport block via the sidechain channel; Determine a second ratio associated with acknowledgment and non-acknowledgment feedback for at least one retransmission of the transport block via the sidechain channel; and Determining the second CWS based on the change from the first ratio to the second ratio includes: Based on the determination that the change exceeds a change threshold, it is determined that the second CWS is not greater than the first CWS; and Based on the determination that the change does not exceed the change threshold, the second CWS is determined to be greater than the first CWS.

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