Auxiliary feedback configuration decision

Abstract

Example embodiments of the present disclosure relate to assisting feedback configuration decisions. In an example method, for a sidelink transmission to be sent from a first terminal device to a second terminal device, the first terminal device performs a first listen before talk (LBT) procedure based on a first detection threshold; performing a second LBT process based on a second detection threshold lower than the first detection threshold; and determining a feedback configuration for the sidelink transmission based on a result of the second LBT process. In this way, the first terminal device can attempt to avoid the failure to receive feedback from the second terminal device.

Description

Technical Field

[0001] Example embodiments of the present disclosure generally relate to the field of communications, and more particularly to a first terminal device, a second terminal device, an apparatus, and a computer-readable storage medium for assisting in feedback configuration decision making. Background Art

[0002] In communication technology, there is a continuous evolution of technology to provide efficient and reliable solutions for using wireless communication networks. Each new generation has its own technical challenges and needs to deal with different situations and processes for connecting and serving devices connected to wireless networks. Since the deployment of the fourth generation (4G) communication system, efforts have been made to develop improved fifth generation (5G) or pre-5G communication systems to meet the demand for increasing wireless data services. The new communication system can support various types of service applications for terminal devices.

[0003] In the 3GPP Rel-18 work item, it was agreed to enhance the sidelink transmission, of which the sidelink in unlicensed spectrum (SL-U) is an important part. For data sent in the unlicensed spectrum channel in SL, the terminal device may need to perform a listen-before-talk (LBT) channel access procedure. On the other hand, providing feedback (e.g. HARQ feedback) for transmission is a technique to achieve efficient and reliable transmission. However, in SL-U, due to the possibility of LBT failure, it may not be guaranteed that the terminal device can perform the transmission of data or feedback (e.g. HARQ feedback). Summary of the invention

[0004] Generally, example embodiments of the present disclosure provide solutions for assisting feedback configuration decisions.

[0005] In a first aspect, a first terminal device is provided. The first terminal device includes at least one processor and at least one memory storing instructions, which, when executed by the at least one processor, cause the first terminal device to at least: perform a first listen-before-talk (LBT) process based on a first detection threshold for a side link transmission to be sent from the first terminal device to a second terminal device; perform a second LBT process based on a second detection threshold lower than the first detection threshold; and determine a feedback configuration of the side link transmission based on a result of the second LBT process.

[0006] In a second aspect, a second terminal device is provided. The second terminal device includes at least one processor and at least one memory storing instructions, which, when executed by the at least one processor, cause the second terminal device to at least: determine whether a request is received from a first terminal device, the request being for feedback about a sidelink transmission from the first terminal device to the second terminal device; based on determining that the request is received, perform an LBT process; based on success of the LBT process, send feedback to the first terminal device, and based on determining that the request is not received, avoid sending feedback to the first terminal device.

[0007] In a third aspect, a method is provided. The method includes: at a first terminal device, for a side link transmission to be sent from the first terminal device to a second terminal device, performing a first listen-before-talk (LBT) process based on a first detection threshold; performing a second LBT process based on a second detection threshold lower than the first detection threshold; and determining a feedback configuration for the side link transmission based on a result of the second LBT process.

[0008] In a fourth aspect, a method is provided. The method includes: determining, at a second terminal device, whether a request is received from a first terminal device, the request being for feedback about a sidelink transmission from the first terminal device to the second terminal device; based on determining that the request is received, performing an LBT procedure; based on success of the LBT procedure, sending feedback to the first terminal device, and based on determining that the request is not received, refraining from sending feedback to the first terminal device.

[0009] In a fifth aspect, an apparatus is provided. The apparatus includes: a component for performing, at a first terminal device, a first listen-before-talk (LBT) process based on a first detection threshold for a sidelink transmission to be sent from the first terminal device to a second terminal device; a component for performing a second LBT process based on a second detection threshold lower than the first detection threshold; and a component for determining a feedback configuration for the sidelink transmission based on a result of the second LBT process.

[0010] In a sixth aspect, an apparatus is provided. The apparatus includes: a component for determining at a second terminal device whether a request is received from a first terminal device, the request being for feedback about a sidelink transmission from the first terminal device to the second terminal device; a component for performing an LBT procedure based on determining that the request is received; a component for sending feedback to the first terminal device based on success of the LBT procedure, and a component for refraining from sending feedback to the first terminal device based on determining that the request is not received.

[0011] In a seventh aspect, a non-transitory computer-readable medium is provided, comprising program instructions for causing an apparatus to at least execute the methods in the third and fourth aspects.

[0012] In an eighth aspect, there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus to at least: perform a first listen-before-talk (LBT) process based on a first detection threshold for a side link transmission to be sent from a first terminal device to a second terminal device; perform a second LBT process based on a second detection threshold that is lower than the first detection threshold; and determine a feedback configuration for the side link transmission based on a result of the second LBT process.

[0013] In a ninth aspect, a computer program is provided, comprising instructions which, when executed by an apparatus, cause the apparatus to at least: determine whether a request is received from a first terminal device, the request being for feedback regarding a side link transmission from the first terminal device to a second terminal device; based on determining that the request is received, perform an LBT process; based on success of the LBT process, send feedback to the first terminal device, and based on determining that the request is not received, avoid sending feedback to the first terminal device.

[0014] In a tenth aspect, a device is provided, comprising: an execution circuit configured to: perform a first listen-before-talk (LBT) process based on a first detection threshold for a side link transmission to be sent from a first terminal device to a second terminal device; an execution circuit configured to: perform a second LBT process based on a second detection threshold lower than the first detection threshold; and a determination circuit configured to: determine a feedback configuration of the side link transmission based on a result of the second LBT process.

[0015] In an eleventh aspect, a device is provided, comprising: a determination circuit configured to determine whether a request is received from a first terminal device, the request being for feedback regarding a side link transmission from the first terminal device to a second terminal device; an execution circuit configured to perform an LBT process based on determining that the request is received; a sending circuit configured to send feedback to the first terminal device based on the success of the LBT process; and avoid sending feedback to the first terminal device based on determining that the request is not received.

[0016] It should be understood that the abstract is not intended to identify the key or essential features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0018] Figure 1A An example of sidelink resource allocation mode 1 is described in which some example embodiments of the present disclosure may be implemented;

[0019] Figure 1BAn example of sidelink resource allocation mode 2 is described in which some example embodiments of the present disclosure may be implemented;

[0020] Figure 2A An example of a first terminal device obtaining a COT via LBT Type 1 in which some example embodiments of the present disclosure may be implemented is described;

[0021] Figure 2B An example of an allowable gap for LBT Type 2A is described in which some example embodiments of the present disclosure may be implemented;

[0022] Figure 2C Another example of an allowable gap for LBT Type 2A is illustrated in which some example embodiments of the present disclosure may be implemented;

[0023] Figure 2D An example of an allowable gap for LBT Type 2B is described in which some example embodiments of the present disclosure may be implemented;

[0024] Figure 2E Another example of an allowable gap for LBT Type 2B is described in which some example embodiments of the present disclosure may be implemented;

[0025] Figure 2F An example of an allowable gap for LBT Type 2C is described in which some example embodiments of the present disclosure may be implemented;

[0026] Figure 2G Another example of an allowable gap for LBT type 2C is illustrated in which some example embodiments of the present disclosure may be implemented;

[0027] Figure 2H An example of COT acquisition of a first terminal device and a second terminal device using some example embodiments of the present disclosure is described;

[0028] Fig.2I illustrating examples of SL time slots in which some example embodiments of the present disclosure may be implemented;

[0029] Figure 2J Another example of an SL slot is described in which some example embodiments of the present disclosure may be implemented;

[0030] Figure 2K illustrates examples of channel mapping in which some example embodiments of the present disclosure may be implemented;

[0031] Figure 3 An example flow of an LBT process with more than one energy detection threshold (EDT) is described according to some example embodiments of the present disclosure;

[0032] Figure 4An example of an LBT process with more than one EDT is described according to some example embodiments of the present disclosure;

[0033] Figure 5A An example of a method implemented at a first terminal device according to some example embodiments of the present disclosure is described;

[0034] Figure 5B Another example of a method implemented at a first terminal device using some example embodiments of the present disclosure is described;

[0035] Figure 6 An example of describing a method implemented at a second terminal device using some example embodiments of the present disclosure;

[0036] Figure 7 a simplified block diagram illustrating a device suitable for implementing some example embodiments of the present disclosure; and

[0037] Figure 8 Block diagram illustrating examples of computer readable media according to some example embodiments of the present disclosure.

[0038] Throughout the drawings, the same or similar reference numbers represent the same or similar elements. DETAILED DESCRIPTION

[0039] The principle of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described only to illustrate and help those skilled in the art to understand and implement 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 the ways described below.

[0040] 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 belongs.

[0041] References to "one embodiment," "an embodiment," "an example embodiment," and the like in this disclosure indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment must include the particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, whether or not explicitly described, it is claimed that it is within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in conjunction with other embodiments.

[0042] 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 simply used to distinguish one element from another element. For example, without departing from the scope of the exemplary embodiments, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element. The term "and / or" as used herein includes any and all combinations of one or more of the listed terms.

[0043] The terms used herein are only used to describe specific embodiments and are not intended to limit the exemplary embodiments. The singular forms "a", "an" and "the" used herein are also intended to include the plural forms, unless the context clearly indicates otherwise. It should be further understood that when used in this article, the terms "comprise", "contain", "have", "have", "include" and / or "include" refer to the presence of the features, elements and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0044] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0045] (a) implemented only in hardware circuits (e.g. implemented only in analog and / or digital circuits) and

[0046] (b) a combination of hardware circuitry and software, such as (where applicable):

[0047] (i) a combination of analog and / or digital hardware circuitry and software / firmware, and

[0048] (ii) hardware processors and software (including digital signal processors), any portion of software and memory that work together to enable a device such as a mobile phone or server to perform various functions), and (c) hardware circuits and / or processors, such as a microprocessor or a portion of a microprocessor, that require software (such as firmware) to operate, but the software may not be present when the software is not required to operate.

[0049] This definition of circuitry applies to all uses of this term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation consisting solely of a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. For example, the term circuitry also covers a baseband integrated circuit or processor integrated circuit of a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device, if applicable to the particular claim element.

[0050] As used herein, the term "communication network" refers to a network that complies with any suitable communication standard, such as Long Term Evolution (LTE), Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), High Speed ​​Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), etc. In addition, the communication between the terminal device and the network device in the communication network can be performed according to any suitable generation of communication protocols, including but not limited to the fourth generation (4G), 4.5G, future fifth generation (5G) communication protocols and / or any other protocols currently known or developed in the future. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communications, there will certainly be future types of communication technologies and systems that can be embodied using the present disclosure. It should not be considered that the scope of the present disclosure is limited to the above-mentioned systems.

[0051] As used herein, the term "network device" refers to a node in a communication network, via which a terminal device accesses the network and receives services from it. A network device may refer to a base station (BS) or an access point (AP), such as a NodeB (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also known as a gNB), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a repeater, an integrated and access backhaul (IAB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-terrestrial network equipment, such as a satellite network equipment, a low earth orbit (LEO) satellite and a geosynchronous orbit (GEO) satellite, an aircraft network equipment, etc., depending on the terminology and technology of the application.

[0052] 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), user station (SS), portable user station, mobile station (MS) or access terminal (AT). Terminal devices may include, but are not limited to, mobile phones, cellular phones, smart phones, voice over IP (VoIP), wireless local loop phones, tablet computers, wearable terminal devices, personal digital assistants (PDAs), portable computers, desktop computers, image capture terminal devices (e.g., digital cameras), game terminal devices, music storage and playback devices, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop mounted devices (LMEs), USB dongles, smart devices, wireless customer premises equipment (CPEs), 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 industrial and / or automated processing chain environments), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. In the following description, the terms "terminal device", "communication device" and "terminal" may be used interchangeably.

[0053] As described above, in SL-U, due to the possibility of LBT failure, it may not be guaranteed that the UE can perform the transmission of data or feedback (such as HARQ feedback). More specifically, for positive feedback and negative feedback, such as ACK / NACK of HARQ, if the second terminal device intends to provide positive feedback to the first terminal device and the LBT process fails, the feedback will not be sent. This will result in unnecessary retransmissions from the first terminal device because it will think that the second terminal device has not received the message. For negative feedback only, if the second terminal device intends to send negative feedback to the first terminal device and is blocked due to LBT failure, the first terminal device will not send any required retransmissions because the first terminal device will think that the second terminal device has successfully received and decoded the message. It is advantageous for the first terminal device to be able to flexibly decide when to enable or request feedback. Decisions can be made using available information, such as the environment, channel, previous feedback success rate, etc.

[0054] In an example embodiment of the present disclosure, the present application provides a mechanism to solve the problems discussed above. The inventors have proposed a set of new methods for assisting feedback configuration decisions to solve the feedback reliability problem. For a side link transmission to be sent from a first terminal device to a second terminal device, the first terminal device performs a first listen-before-talk (LBT) process based on a first detection threshold. The first terminal device performs a second LBT process based on a second detection threshold that is lower than the first detection threshold, and determines the feedback configuration of the side link transmission based on the result of the second LBT process. In this way, the first terminal device can try to avoid being unable to receive feedback from the second terminal device and maintain reliable and efficient SL transmission.

[0055] In an exemplary embodiment of the present disclosure, using the feedback configuration, the first terminal device can determine whether to enable the second terminal device to send feedback (eg, HARQ feedback) or to perform SL transmission using link adaptation. Additionally or alternatively, SL transmission can be performed using at least one blind retransmission.

[0056] Figure 1A An example of side link resource allocation mode 1 in which some exemplary embodiments of the present disclosure can be implemented is described. In a network environment 100, there are a network device 105, a first terminal device 101, and a second terminal device 103. The first terminal device 101 and the second terminal device 103 can be vehicles, mobile phones or other terminal devices.

[0057] In some example embodiments, the SL may be designed to facilitate the first terminal device 101 to communicate with at least one other terminal device in the vicinity via direct / SL communication, such as with the second terminal device 103. Two resource allocation modes may be specified, one of which the first terminal device is configured to perform its NR SL transmissions. These modes are denoted as NR SL Mode 1 and NR SL Mode 2. In Mode 1, the sidelink transmission resources are allocated or scheduled to the second terminal device 103 by the network device 105, while the first terminal device 101 in NR SL Mode 2 autonomously selects its SL transmission resources.

[0058] In mode 1, when the network device 105 is responsible for SL resource allocation, the configuration and operation are similar to those on the Uu interface. The first terminal device 101 sends a SL service request 110 to the network device 105 and receives a resource allocation 120 from the network device 105. The first terminal device 101 performs SL transmission 130 to the second terminal device 103 and receives SL feedback 140 from the second terminal device 103.

[0059] In mode 2, if Figure 1BAs shown, the first terminal device 101 autonomously performs resource selection with the help of a sensing process in a sensing window. More specifically, the first terminal device 101 in NR SL mode 2 first performs a sensing process on at least one configured SL transmission resource pool to obtain knowledge of at least one other nearby SL TX terminal device about at least one reserved resource. Based on the knowledge obtained from the sensing, the first terminal device 101 can select at least one resource from the available SL resources in the selection window accordingly. In order for the first terminal device 101 to perform sensing and obtain the information required to receive the SL transmission, it is necessary to decode the side link control information (SCI). The SCI associated with data transmission may include level 1 SCI and level 2 SCI.

[0060] In some example embodiments, the SCI follows a 2-level SCI structure, the main motivation of which is to support the size difference between SCIs for various NR-V2XSL service types (e.g., broadcast, multicast, and unicast). Level 1 SCI, or SCI format 1-A, is carried by PSCCH and contains: information for implementing sensing operations, determining PSSCH resource allocation, and information required for decoding level 2 SCI. Level 2 SCI, or SCI formats 2-A and 2-B, is carried by PSSCH multiplexed with SL-SCH and contains: source and destination identification, information for identifying and decoding associated SL-SCH transport blocks (TBs), control of HARQ feedback in unicast / multicast, and triggers for CSI feedback in unicast.

[0061] ETSI EN 301 893 V2.1.1 (2017-05) or the RLAN harmonized standard covers the necessary requirements of Article 3.2 of Directive 2014 / 53 / EU and is considered the main reference. In the unlicensed bands below 7GHz, the coexistence of New Radio (NR) with other systems (such as IEEE802.11) is ensured via a listen-before-talk (LBT) channel access mechanism. Among them, the terminal equipment intending to perform side line (SL) transmission needs to first successfully complete the LBT check before starting the transmission.

[0062] For a terminal device to pass the LBT check, it must observe the channel as available during a number of consecutive Clear Channel Assessment (CCA) slots. In sub-7GHz frequencies, these slots are 9μs in duration. If the measured power or the energy collected during the CCA period is below a regulatory threshold, the UE considers the channel available during the CCA slot, which may depend on the operating band and geographic region.

[0063] In some example embodiments, when the first terminal device 101 initiates the sidelink communication, or the first TD 101 plays the role of the initiating device, the first TD 101 must obtain the "right" to access the channel for a certain period of time, which is expressed in the regulations as the channel occupation time (COT), by applying an "extended" LBT process (wherein the channel must be considered idle for the entire duration of the contention window (CW)). This "extended" LBT process is named LBT Type 1. The first terminal device obtains the COT via LBT Type 1 in Figure 2A In the description.

[0064] As shown, the duration of both COT and CW depends on the channel access priority class (CAPC) associated with the traffic of the first TD 101. In some example embodiments, as shown in Table 1, control plane traffic (e.g., physical channel control channel (PSCCH)) is transmitted with a channel access priority class p=1, while user plane traffic has p>1, as shown in Table 1.

[0065] In some example embodiments, LBT Type 1 details for the Uu uplink (UL) case are described. In some example embodiments, Table 1 may be used in the SL, but it should be noted that LBT Type 1 parameters or a different set of channel access parameters for the downlink (DL) case may also be used in the SL in principle.

[0066] Table 1 Channel Access Priority Class (CAPC) for UL

[0067]

[0068] In some example embodiments, Table 1 may be from 3GPP specification TS 37.213, Table 4.2.1-1: Channel Access Priority Classes (CAPCs) for UL. The contention window length in the CCA slot associated with each CAPC has a minimum value CW min,p and maximum CW max,p The duration of COT is determined by T ulm cot,p Given.

[0069] In some example embodiments, for p=3, 4, if the high-level parameter absenceOfAnyOtherTechnology-r14 or absenceOfAnyOtherTechnology-r16 is provided, then T ulm cot,p =10ms, otherwise T ulmcot,p =6ms. In some example embodiments, when T ulm cot,p= 6ms, it may be increased to 8ms by inserting one or more gaps. The minimum duration of a gap shall be 100us. The maximum duration including any such gap shall be 6ms.

[0070] In some example embodiments, the first terminal device 101 that initiates the transmission (the initiating terminal device) obtains a COT1 having a duration associated with the corresponding CAPC after successfully completing LBT Type 1 110 and performing a SL transmission to the second terminal device 103 in the physical sidelink control channel (PSCCH) and the physical sidelink shared channel (PSSCH) 120. The obtained COT1 is valid even if the first terminal device 101 suspends its transmission, although the first terminal device 101 wishes to perform a new transmission (within the COT). A "simplified" LBT procedure still needs to be performed. As described in 3GPP specification TS 37.213, this "simplified" LBT procedure can be named LBT Type 2, with the following variants:

[0071] Type 2A (25μs LBT) is used for SL transmission within the COT acquired by the initiating terminal device and for SL transmission after another SL transmission when the gap between two SL transmissions is ≥ 25μs, e.g. Figure 2B and Figure 2C As shown. Figure 2B and Figure 2C , the transmission of LBT type 1 and the gray background is performed by the first terminal device 101, and the transmission of the white background is performed by the second terminal device 103.

[0072] Type 2B (16μs LBT) is used for SL transmission within the COT acquired by the initiating terminal device, and can only be used for SL transmission with a gap of exactly 16μs after another SL. Figure 2D and Figure 2E As shown. Figure 2D and Figure 2E , the transmission of LBT type 1 and the gray background is performed by the first terminal device 101, while the transmission of the white background is performed by the second terminal device 103.

[0073] Type 2C (no LBT) can only be used for SL transmission after another SL, where the gap is <16μs and the duration of the allowed SL transmission is ≤584μs, e.g. Figure 2F and Figure 2G As shown. Figure 2F and Figure 2G In the example, the transmission of LBT type 1 and the gray background is performed by the first terminal device 101, while the transmission of the white background is performed by the second terminal device 103. A person skilled in the art will appreciate that the gap may also be other values.

[0074] Figure 2H An example of COT acquisition by a first terminal device and a second terminal device using some example embodiments of the present disclosure is described. Figure 2H The first terminal device 101 and the second terminal device 103 in the Figure 1A are the same as those in . In some example embodiments, when the first terminal device 101 initiates the sidelink communication, or the first TD 101 plays the role of the initiating device. After LBT Type 1 210, the first TD 101 must obtain the "right" to access the channel for a certain period of time, which is expressed in the regulations as channel occupancy time 1 (COT1). The first terminal device 101 can perform sidelink transmission to the second terminal device 103 in PSCCH / PSSCH 220. The second terminal device 103 can perform LBT Type 2 230 and then send feedback to the first terminal device 101 in the physical sidelink feedback channel (PSFCH) 240.

[0075] In some example embodiments, the first terminal device 101 may share its acquired COT1 with the second terminal device 103. To this end, the first terminal device 101 may inform the second terminal device 103 of the duration of COT1, for example via control signaling. The second terminal device 103 may use this information to decide which type of LBT should be applied when performing a transmission for which the second terminal device 103 is the initiating device. If the transmission of the second terminal device 103 is not within the range of COT1, the second terminal device 103 will have to acquire a new COT2 using LBT type 1 250 with an appropriate CAPC. Thereafter, the second terminal device 103 may make a sidelink transmission to the third terminal device 201 in PSCCH / PSSCH 260. After LBT type 2 270, the third terminal device 201 may send feedback in PSFCH 280.

[0076] In some example embodiments, the resource configuration in the sidelink resource pool defines the minimum information required for an RX terminal device to be able to decode a transmission, including the number of subchannels, the number of physical resource blocks (PRBs) per subchannel, the number of symbols in the PSCCH (wherein a time slot has a PSFCH), and other configuration aspects not relevant to the present invention.

[0077] In some example embodiments, details of the actual sidelink transmission or payload are provided in the PSCCH (Level 1 SCI) for each individual transmission, including: time and frequency resources, demodulation reference signal (DMRS) configuration for PSSCH, MCS, PSFCH, etc. In an example embodiment, the SL slot includes PSCCH and PSSCH, such as Fig.2I In another exemplary embodiment, the SL time slot includes PSCCH, PSSCH, and PSFCH, as shown in FIG. Figure 2J shown.

[0078] In an example embodiment, the configuration of the PSCCH (e.g., DMRS, MCS, number of symbols used) is part of the resource pool configuration. In addition, the indication of which time slots have PSFCH symbols is also part of the resource pool configuration. However, the configuration of the PSSCH (e.g., number of symbols used, DMRS mode, and MCS) is provided by the level 1 SCI, which is the payload sent in the PSCCH.

[0079] PSFCH was introduced during Rel-16 to enable HARQ feedback on the sidelink from a second terminal device 103, or the second terminal device 103, which is the intended recipient of the PSSCH transmission, to the terminal device (e.g., the first terminal device 101) performing the transmission. In PSFCH, the Zadoff-Chu sequence in one PRB is repeated over two OFDM symbols, where the first symbol can be used for AGC, near the end of the SL resources in the time slot. The Zadoff-Chu sequence as a basic sequence can be pre-configured according to the sidelink resource pool.

[0080] The time resources of PSFCH are preconfigured to appear once every 0, 1, 2, or 4 time slots according to 3GPP TS 38.331. The HARQ feedback resources in PSFCH are derived from the resource positions of PSCCH / PSSCH. For PSSCH to HARQ timing, there is a configuration parameter K in units of time slots. The timing of PSFCH is determined from K. For PSSCH transmission with the last symbol located in time slot n, HARQ feedback is located in time slot n+a, where a is the smallest integer greater than or equal to K, provided that time slot n+a contains PSFCH resources. A time gap of at least K time slots allows consideration of the processing delay of the second terminal device 103 when decoding PSCCH and generating HARQ feedback. K can be equal to 2 or 3, and a single K value can be preconfigured for each resource pool. This enables multiple RX terminal devices using the same resource pool to use the same PSFCH resource mapping for HARQ feedback. Using parameter K, N PSSCH time slots associated with the PSFCH time slot can be determined.

[0081] Figure 2KAn example of channel mapping in which some example embodiments of the present disclosure may be implemented is described. The period of the PSFCH resource is configured as N=4, where there are 4 PSSCH time slots associated with the PSFCH, and K or sl-MinTimeGapPSFCH is configured as 2. In the case where there are L subchannels in the resource pool and N PSSCH time slots are associated with the time slot containing the PSFCH, there are N*L subchannels associated with the PSFCH symbol. In the case where M PRBs are available for PSFCH in the PSFCH symbol, there are M PRBs available for HARQ feedback for transmission on the N*L subchannels.

[0082] In the case where M is configured as a multiple of N*L, then for each subchannel in the PSFCH period, HARQ feedback may be associated with a different set of Mset=M / (N*L)PRBs. A first set of Mset PRBs available for PSFCH is associated with HARQ feedback for transmissions in the first subchannel in the first time slot. A second set of Mset PRBs is associated with HARQ feedback for transmissions in the first subchannel in the second time slot, and so on.

[0083] In some example embodiments, as illustrated in FIG2b, where N=4, L=3, all PRBs in a PSFCH symbol are available for PSFCH. In this example, HARQ feedback for a transmission at PSSCH x is sent on the xth group Mset PRBs in the corresponding PSFCH symbol, where x=1, ..., 12.

[0084] In some example embodiments, in the case where ACK / NACK feedback is for multicast communication, or in the case where different PSSCH transmissions are located on the same subchannel, a set of Mset PRBs associated with a subchannel may be shared among multiple RX terminal devices. For each PRB available for PSFCH, there are Q available cyclic shift pairs to support ACK or NACK feedback for Q RX terminal devices within the PRB. For a resource pool, the number of cyclic shift pairs Q is preconfigured and can be equal to 1, 2, 3, or 6.

[0085] In some example embodiments, the number of PSFCH resources F available to support HARQ feedback for a given transmission may be calculated. In 3GPP TS 38.213, F is denoted as In the case where each PSFCH resource is used by one RX terminal device, the F available PSFCH resources may be used for ACK / NACK feedback of a maximum of F RX terminal devices.

[0086] In some example embodiments, the F PSFCH resources available for HARQ feedback multiplexing the PSSCH may be determined based on two options:

[0087] Option 1: F is based on the L PSSCH subchannels used by PSSCH, where F can be calculated as: F = L PSSCH * Mset * Q PSFCH, which is associated with the L PSSCH subchannels of PSSCH. There are L PSSCH subchannels of PSSCH, there are Mset PRBs associated with each subchannel for PSFCH, and there are Q cyclic shifts available in each PRB.

[0088] Scheme 2: F is based only on the starting subchannel used by PSSCH, or only on one subchannel for the case where L PSSCH > 1. F = Mset*Q PSFCH, which is associated with the starting subchannel of PSSCH. There are Mset PRBs associated with each subchannel for PSFCH; and there are Q cyclic shift pairs available in each PRB.

[0089] In some example embodiments, the available F PSFCH resources are indexed based on the PRB index in the frequency domain and the cyclic shift pair index in the code domain. The mapping of the PSFCH index i (i=1, 2, ... F) to the PRB and Q cyclic shift pairs is such that the PSFCH index i first increases with the PRB index until the number of available PRBs for the PSFCH is reached. Then, it increases with the cyclic shift pair index, then with the PRB index, and so on.

[0090] Of the F PSFCHs available for HARQ feedback for a given transmission, the RX terminal device selects the PSFCH with index i for its HARQ feedback, where i is given by:

[0091] i=(T ID +R ID )mod F,

[0092] Where T ID It is the layer 1 identification of the RX terminal device and is indicated in the level 2 SCI. ID =0 for unicast ACK / NACK feedback and multicast NACK-only feedback. Multicast NACK-only feedback is multicast option 1.

[0093] For multicast ACK / NACK feedback or multicast option 2, R ID = is equal to the RX terminal device identifier within the group, which is indicated by the upper layer. For a number (X) of RX terminal devices within the group, the RX terminal device identifier is an integer between 0 and X-1. The RX terminal device determines which PRB and cyclic shift pair should be used to send its HARQ feedback based on the PSFCH index i. The RX terminal device uses the first or second cyclic shift in the cyclic shift pair associated with the selected PSFCH index i to send a NACK or ACK, respectively.

[0094] By selecting the PSFCH with index i by the RX terminal device, the TX terminal device can distinguish the HARQ feedback of different RX terminal devices via the RX terminal device identifier, e.g. for multicast option 2, and distinguish the HARQ feedback intended for the TX terminal device via the layer 1 ID of the TX terminal device, e.g. for unicast. ID = 0, the RX terminal device only uses the first terminal device 101 identifier T based on the first layer ID ID , select the same PSFCH index i for its NACK-only feedback.

[0095] For PSFCH transmission or reception with HARQ-ACK information, the priority value of PSFCH is equal to the priority value indicated by SCI format 1-A associated with PSFCH. For PSFCH transmission with conflicting information, the priority value of PSFCH is equal to the minimum priority value determined by the corresponding SCI format 1-A of the conflicting resources. For PSFCH reception with conflicting information, the priority value of PSFCH is equal to the priority value determined by the corresponding SCI format 1-A of the conflicting resources.

[0096] In some example embodiments, for HARQ with ACK / NACK feedback, if the second terminal device 103 intends to send a positive HARQ ACK to the first terminal device 101, and the LBT process fails, the feedback will not be sent in the expected PSFCH symbol. This will result in unnecessary retransmissions from the first terminal device 101, as it will think that the second terminal device 103 did not receive the message.

[0097] On the other hand, in some example embodiments, for HARQ with NACK-only feedback, in the case where NACK-only HARQ feedback is configured, if the second terminal device 103's intention to send a NACK to the first terminal device 101 is blocked due to an LBT failure, the first terminal device 101 will not send any (required) retransmission because it will assume that the second terminal device 103 has successfully received and decoded the message.

[0098] In some example embodiments, in SL-U, it is advantageous for the first terminal device 101 to have the flexibility to decide when to enable or request HARQ feedback from the second terminal device 103, and to use already available information about the environment, channel, previous feedback success rates, etc., to make such decisions in the most intelligent manner possible.

[0099] Figure 3An example flow of an LBT process with more than one energy detection threshold (EDT) is described according to some example embodiments of the present disclosure. In process 300, for a side link transmission to be sent from a first terminal device 101 to a second terminal device 103, the first terminal device 101 performs (310) a first LBT process based on a first detection threshold. In addition, the first terminal device 101 performs (315) a second LBT process based on a second detection threshold, the second threshold being lower than the first threshold. Then, the first terminal device 101 determines (320) a feedback configuration for the side link transmission based on the result of the second LBT process. If the first terminal device 101 determines that the second LBT process is successful, the first terminal device 101 determines that feedback from the second terminal device 103 is enabled for the side link transmission.

[0100] Then, the first terminal device 101 sends (325) a request 330 for feedback to the second terminal device 103. If the first terminal device 101 determines that the second LBT process is unsuccessful, the first terminal device 101 determines to disable feedback from the second terminal device 103. In this way, the first terminal device 101 can avoid failing to receive feedback from the second terminal device 103 as much as possible, and maintain reliable and efficient SL transmission. In some example embodiments, the feedback may be HARQ feedback. The feedback may also be other feedback for sidelink transmission, such as channel coding without error correction, and CRC check instead.

[0101] In some example embodiments, the first detection threshold may be a first energy detection threshold (EDT1), and the second detection threshold may be a second energy detection threshold (EDT2). The first detection threshold and the second detection threshold may be energy power, voltage, or electricity, etc.

[0102] In some example embodiments, the first LBT process and the second LBT process may be performed simultaneously using the same channel access type. When applying LBT type 1, the first terminal device 101 applies both EDT1 and EDT2 when applying LBT in all CCA time slots. If the first LBT with EDT1 is successful, the contention window counter may decrease until it reaches zero, and the first terminal device 101 may attempt channel access.

[0103] If, during the countdown of the contention window, the amount of CCA time slots in which the second LBT with EDT2 is unsuccessful, or the received signal power is higher than the second detection threshold, it indicates that a transmission is in progress near the second terminal device 103, and therefore the first terminal device 101 should not send a HARQ feedback request to the second terminal device 103. Otherwise, the first terminal device 101 may request HARQ feedback. When LBT type 2 is applied, when LBT is applied in the CCA time slot, the first terminal device 101 applies both EDT1 and EDT2. If the first LBT with EDT1 is successful, the first terminal device 101 may continue the sidelink transmission, but only request HARQ feedback if the second LBT with EDT2 is also successful. In this way, the total LBT process time can be shortened.

[0104] In some example embodiments, the second LBT with EDT2 may be performed at the end of the first LBT with EDT1, for example in the case of LBT type 1, using single energy detection. Alternatively, the second LBT with EDT2 may be performed after the first LBT with EDT1, for example when the second terminal device 103 is expected to perform its own LBT before the HARQ feedback with PSFCH transmission. In this way, more flexibility is introduced to the first LBT with EDT1, and the second LBT with EDT2.

[0105] In some example embodiments, based on determining that the second LBT process is unsuccessful, the first terminal device 101 implements link adaptation. In link adaptation, the first terminal device 101 can reduce the constellation in the modulation. Additionally or alternatively, the first terminal device 101 can reduce the channel coding rate in the side link transmission. Additionally or alternatively, the first terminal device 101 can implement at least one blind retransmission. Additionally or alternatively, the first terminal device 101 can increase the transmit power. Additionally or alternatively, the first terminal device 101 can increase the transmit diversity, such as frequency diversity, time diversity, or special diversity. Additionally or alternatively, the first terminal device 101 can increase the beamforming gain. It can be understood by ordinary persons in the art that other schemes can be adopted in link adaptation. In this way, the first terminal device 101 can more reliably send a side link to the second terminal device 103 without HARQ feedback.

[0106] In some example embodiments, the second detection threshold may be determined based on a portion of the first detection threshold. Additionally or alternatively, the second detection threshold may be determined based on the size of a group of terminal devices of the multicast sidelink transmission, the second terminal device being one of the terminal devices in the group. Additionally or alternatively, the second detection threshold may be determined based on a channel busy rate (CBR) associated with the sidelink transmission. Additionally or alternatively, the second detection threshold may be determined based on a physical sidelink feedback channel (PSFCH) load associated with the sidelink transmission. Additionally or alternatively, the second detection threshold may be determined based on a service priority of the sidelink transmission. Additionally or alternatively, the second detection threshold may be determined based on a service type of the sidelink transmission. In this way, the second detection threshold may be determined more accurately.

[0107] In some example embodiments, the first terminal device 101 may determine a feedback configuration for the side link transmission based on the number of terminal devices to which the side link transmission is multicast. Additionally or alternatively, the first terminal device 101 may determine a feedback configuration for the side link transmission based on a PSFCH load associated with the side link transmission. Additionally or alternatively, the first terminal device 101 may determine a feedback configuration for the side link transmission based on a determination that the second terminal device has a coverage problem. In this way, more factors may be considered when determining the feedback configuration for the side link transmission, and the determination may be made more accurately.

[0108] In some example embodiments, first terminal device 101 may receive the first detection threshold from network device 105. Additionally or alternatively, first terminal device 101 may receive the second detection threshold from network device 105. Network device 105 may have more information about the network than the terminal device and may therefore calculate the first detection threshold and the second detection threshold more accurately.

[0109] In some example embodiments, the first terminal device 101 may receive (360) an indication 355 of the LBT process. The indication 355 of the LBT process may be an indication for the second terminal device 103 to send feedback to the first terminal device 101 that the LBT process performed was successful. The first terminal device 101 may adjust the second detection threshold based on the indication 355. In this way, the feedback transmission from the second terminal device 103 may be more reliable.

[0110] In some example embodiments, the first terminal device 101 may determine that no feedback is received from the second terminal device. In this case, the second terminal device 103 may be far away from the first terminal device 101. The first terminal device may adjust the second detection threshold to a lower value to obtain feedback from the second terminal device at a farther distance.

[0111] In some example embodiments, the first terminal device 101 may determine that feedback is received from the second terminal device. In this case, the second terminal device 103 may be close to the first terminal device 101. The first terminal device may adjust the second detection threshold to a higher value to avoid interference from other terminal devices.

[0112] In some example embodiments, in the case where LBT2 is successful, the first terminal device 101 may determine that no feedback is received from the second terminal device 103. Based on the success of the second LBT process, the first terminal device 101 may determine that the second terminal device 103 did not receive the sidelink transmission from the first terminal device 101. The first terminal device may know that this is due to poor channel quality, for example, the second terminal device 103 is out of range of the first terminal device 101.

[0113] In some example embodiments, in the case of a failure in the LBT2 process, the first terminal device 101 may determine that an LBT failure has occurred at the second terminal device 103 for sending feedback. In this way, the first terminal device 101 may determine the cause of the failure of the feedback from the second terminal device 103 more accurately.

[0114] Continue to refer Figure 3 , on the other side, the second terminal device 103 receives (340) a request for feedback from the first terminal device 101. The second terminal device 103 determines (335) whether a request for feedback from the first terminal device 101 is received. After determining that the request from the first terminal device 101 is received, the second terminal device 103 may send feedback, such as HARQ feedback, to the first terminal device 101. The second terminal device 103 performs (345) an LBT process for sending feedback to the first terminal device. Based on the success of the LBT process, the second terminal device 103 sends feedback to the first terminal device 101. The second terminal device 103 sends (350) an indication of the success of the LBT process to the first terminal device 101. Based on determining that the request for feedback is not received, the second terminal device 103 avoids sending feedback to the first terminal device 101. In this way, feedback (such as HARQ feedback) can be sent from the second terminal device 103 to the first terminal device 101 more reliably.

[0115] Figure 4 An example of an LBT process with more than one EDT according to some example embodiments of the present disclosure is described. In some example embodiments, the first terminal device 101 may perform LBT using two different EDTs, where a first EDT or EDT1 may be given as specified and a second EDT or EDT2 is lower than the first EDT, thereby being able to detect transmissions from terminal devices located at a greater distance.

[0116] In some example embodiments, EDT2 may be a general value, or given according to EDT1. Additionally or alternatively, EDT2 may be given according to other parameters, such as group size, CBR, PSFCH load, service priority, or service type. If the LBT with EDT1 410 is successful, the first terminal device 101 may continue with its transmission. The LBT with EDT2 420 is used to decide whether the first terminal device 101 should use blind retransmission, or should request HARQ feedback instead. If the LBT with EDT2 420 is successful, the first terminal device 101 assumes that there is no interference near the second terminal device 103, and therefore requests HARQ feedback without link adaptation.

[0117] If the LBT with EDT2 420 is unsuccessful, the first terminal device 101 believes that there may be an interference problem near the second terminal device 103, which causes the LBT with EDT2 420 to fail. Therefore, the first terminal device 101 can determine to perform link adaptation or blind retransmission. In link adaptation, the first terminal device 101 can reduce the constellation in the modulation. In addition or alternatively, the first terminal device 101 can reduce the channel coding rate. In addition or alternatively, the first terminal device 101 can use at least one blind retransmission. This can be illustrated in Table 3. The second terminal device 103 can also use LBT with ETD2 430 before sending HARQ feedback to avoid interference from other terminal devices.

[0118] Table 3. HARQ feedback decisions based on LBT results using two different EDTs

[0119]

[0120] In some example embodiments, the first terminal device 101 may use information from EDT2 to distinguish between interference-related failures (LBT failures) and channel quality-related failures, thereby adaptively determining how to handle HARQ retransmissions triggered by missing HARQ feedback and SL wireless link failure detection.

[0121] In some example embodiments, if NACK-only HARQ is configured and no feedback is received, the first terminal device 101 may determine whether the cause is poor channel quality in the case of successful LBT, for example, due to the second terminal device 103 being out of range of the first terminal device 101. Alternatively, if LBT of the second terminal device 103 with EDT2 is unsuccessful, the cause may be a failure of LBT of the second terminal device 103. In the former case, the first terminal device 101 may not be triggered to perform HARQ retransmission. In the latter case and the target reliability requirement of SL multicast is high, the lack of HARQ NACK feedback due to the failure of LBT of the second terminal device 103 may trigger HARQ retransmission of the first terminal device 101.

[0122] In some example embodiments, if HARQ with ACK / NACK is configured for SL multicast or SL unicast, the first terminal device 101 may also use the LBT result with EDT2 to determine whether the loss of HARQ ACK / NACK feedback is due to poor channel quality or due to LBT failure of the second terminal device 103. If it is determined that the loss of HARQ ACK / NACK feedback is caused by LBT failure of the second terminal device 103, the first terminal device 101 may not consider the loss of HARQ ACK / NACK when determining SL RLF. Additionally or alternatively, the first terminal device 101 may determine whether to perform HARQ retransmission based on the reliability requirements of SL multicast or unicast transmission, the latest SL channel state information (CSI) report from the second terminal device 103, or the following other information.

[0123] In some example embodiments, an LBT process with EDT1 and an LBT process with EDT2 may be performed simultaneously using the same channel access type. For example, when LBT type 1 is applied, when LBT is applied in all CCA time slots, the first terminal device 101 applies both EDT1 and EDT2. If LBT with EDT1 is successful, the contention window counter may be reduced until it reaches zero, and the first terminal device 101 may attempt channel access. If the amount of CCA time slots in which LBT with EDT2 is unsuccessful during the contention window countdown is higher than the second detection threshold, it indicates that there is a transmission in progress near the first terminal device 101 target receiver, and therefore the first terminal device 101 should not request HARQ feedback. Otherwise, the first terminal device 101 may request HARQ feedback. When LBT type 2 is applied, when LBT is applied in the CCA time slot, the first terminal device 101 applies both EDT1 and EDT2. If LBT with EDT1 is successful, the first terminal device 101 may continue with its transmission, but will only request HARQ feedback if LBT with EDT2 is also successful.

[0124] In some example embodiments, EDT2 may be performed at the end of EDT1, for example using single energy detection in the case of LBT type 1. Alternatively, the LBT process with EDT2 is performed after the LBT process with EDT1, for example when the second terminal device 101 is expected to perform its own LBT before PSFCH transmission.

[0125] In some example embodiments, the knowledge provided by the LBT having two or more different detection thresholds (eg, EDT1 and EDT2) may be combined with other types of information or knowledge to trigger a HARQ feedback request when initiating a transmission. Some examples of other useful information may be given as follows.

[0126] Useful information could be the number of end devices being served. In the case of multicast, if the number of end devices is very large, there is a high probability that at least one Rx end device will not be able to successfully receive and decode the information. This will in most cases result in the Tx end device retransmitting the lost data anyway. Therefore, the Tx end device can take a proactive approach and use link adaptation or even blind retransmissions to avoid the overhead and interference caused by a large number of users accessing the channel to provide feedback.

[0127] Additionally or alternatively, useful information could be the PSFCH load, or the number of PSFCH resource blocks typically used, combined with the number of terminal devices being served. High utilization of PSFCH resource blocks may lead to PSFCH capacity issues, which will prevent some Rx terminal devices from providing HARQ feedback. This is more relevant in unlicensed spectrum, especially if the resource pool is limited to 20MHz, and furthermore if staggered PSFCH is employed to meet OCB and PSD requirements.

[0128] Additionally or alternatively, useful information may be that there is a coverage problem. If the Tx terminal device knows in advance that the Rx terminal device has a coverage problem due to being at the edge of range, or due to any other path loss, obstacle or attenuation, it may be operable to apply link adaptation to maximize the probability of success of these terminal devices receiving data. Otherwise, if there is no coverage problem and the expected probability of successfully performing transmission and reception is high, HARQ feedback may be enabled.

[0129] In some example embodiments, the second terminal device 103 may provide feedback to the first terminal device 101, thereby allowing adaptation of EDT2. Successful LBT of the second terminal device 103 may cause EDT2 to trend towards EDT1 if the first terminal device 101 fails to detect LBT using the original EDT2. Alternatively, no PSFCH feedback may be used to make EDT2 more stringent.

[0130] Figure 5A An example of a method 500 implemented at a first terminal device 101 using some example embodiments of the present disclosure is described. At block 510, for a side link transmission to be sent from the first terminal device to the second terminal device, the first terminal device performs a first listen-before-talk (LBT) process based on a first detection threshold. At block 520, the first terminal device 101 performs a second LBT process based on a second detection threshold lower than the first detection threshold. At block 530, the first terminal device 101 determines a feedback configuration for the side link transmission based on a result of the second LBT process.

[0131] In some embodiments, when determining the feedback configuration for the sidelink transmission, the first terminal device 101 may determine that the second LBT process is successful. Then, based on determining that the second LBT process is successful, the first terminal device 101 may determine to enable feedback from the second terminal device for the sidelink transmission.

[0132] In some embodiments, the first terminal device 101 further sends a request for feedback to the second terminal device. In some embodiments, the first terminal device 101 further receives feedback from the second terminal device for adjusting the second detection threshold, and then adjusts the second detection threshold based on the indication. The feedback for adjusting the second detection threshold includes: an indication of whether the LBT process performed by the second terminal device for sending feedback to the first terminal device is successful or unsuccessful. Then, the first terminal device 101 adjusts the second detection threshold based on the feedback for adjusting the second detection threshold.

[0133] In some embodiments, the first terminal device 101 further determines that no feedback is received from the second terminal device. Then, based on the determination that no feedback is received, the first terminal device 101 can adjust the second detection threshold to a lower value. In some embodiments, the first terminal device 101 further determines that feedback is received from the second terminal device. Then, based on the determination that feedback is received, the first terminal device 101 can adjust the second detection threshold to a higher value.

[0134] Figure 5B Another example of a method implemented at a first terminal device using some example embodiments of the present disclosure is described.

[0135] At block 560, the first terminal device 101 determines that feedback was not received from the second terminal device. At block 570, the first terminal device determines whether the second LBT process was successful. Then, based on the success of the second LBT process, at block 580, the first terminal device 101 determines that the second terminal device 102 did not receive the sidelink transmission from the first terminal device. Alternatively, based on the failure of the second LBT process, at block 590, the first terminal device 101 determines that the LBT at the second terminal device for sending feedback failed.

[0136] In some embodiments, when determining the feedback configuration of the side link transmission, the first terminal device 101 determines that the second LBT process is unsuccessful. Then, based on determining that the second LBT process is unsuccessful, the first terminal device 101 determines: disable feedback of the side link transmission from the second terminal device. In some embodiments, the first terminal device 101 further uses link adaptation or at least one blind retransmission to send the side link transmission to the second terminal device. In some embodiments, the first LBT process and the second LBT process are performed simultaneously, or the second LBT process is performed at the end of the first LBT process, or the second LBT process is performed after the first LBT process.

[0137] In some embodiments, the second detection threshold is determined based on a portion of the first detection threshold. Additionally or alternatively, the second detection threshold is determined based on the size of a group of terminal devices to which the sidelink transmission is multicast, and the second terminal device is one of the terminal devices in the group. Additionally or alternatively, the second detection threshold is determined based on a channel busy rate (CBR) associated with the sidelink transmission. Additionally or alternatively, the second detection threshold is determined based on a physical sidelink feedback channel (PSFCH) load associated with the sidelink transmission. Additionally or alternatively, the second detection threshold is determined based on the service priority of the sidelink transmission. Additionally or alternatively, the second detection threshold is determined based on the service type of the sidelink transmission.

[0138] In some embodiments, when determining the feedback configuration for the sidelink transmission, the first terminal device 101 further determines based on at least one of the following items: the number of terminal devices to which the sidelink transmission is multicast, the PSFCH load associated with the sidelink transmission, or determining that the second terminal device has a coverage problem. In some embodiments, the first terminal device further receives at least one of the first detection threshold or the second detection threshold from the network device. In some embodiments, the first terminal device is configured to determine whether to request HARQ feedback for each transport block (TB).

[0139] Figure 6An example of method 600 implemented at a second terminal device 103 using some example embodiments of the present disclosure is described. In block 610, the second terminal device 103 determines whether a request is received from the first terminal device, the request being feedback about a side link transmission from the first terminal device to the second terminal device. In block 620, based on determining that the request is received, the second terminal device 103 performs an LBT process. In block 630, based on the success of the LBT process, the second terminal device 103 sends feedback to the first terminal device. In addition, the second terminal device 103 sends an indication of the success of the LBT process to the first terminal device. In block 640, based on determining that the request is not received, the second terminal device 103 avoids sending feedback to the first terminal device.

[0140] In some embodiments, an apparatus capable of executing method 500 (eg, first terminal device 101) may include components for executing the various steps of method 500. These components may be implemented in any suitable form. For example, the components may be implemented in a circuit or a software module.

[0141] In some embodiments, the apparatus includes: a component for performing a first listen-before-talk (LBT) process based on a first detection threshold for a side link transmission to be sent from a first terminal device to a second terminal device; a component for performing a second LBT process based on a second detection threshold that is lower than the first detection threshold; and a component for determining a feedback configuration for the side link transmission based on a result of the second LBT process.

[0142] In some embodiments, the component for determining the feedback configuration of the sidelink transmission includes: a component for determining that the second LBT process is successful; and a component for determining to enable feedback for the sidelink transmission from the second terminal device based on determining that the second LBT process is successful. In some embodiments, the apparatus further includes: a component for sending a request for feedback to the second terminal device.

[0143] In some embodiments, the apparatus further comprises: a component for receiving feedback from the second terminal device for adjusting the second detection threshold, the feedback for adjusting the second detection threshold comprising: an indication of whether the LBT process performed by the second terminal device for sending feedback to the first terminal device is successful or unsuccessful; and a component for adjusting the second detection threshold based on the feedback for adjusting the second detection threshold. In some embodiments, the apparatus further comprises: a component for determining that no feedback is received from the second terminal device; and a component for adjusting the second detection threshold to a lower value based on determining that no feedback is received.

[0144] In some embodiments, the apparatus further comprises: a component for determining that feedback from the second terminal device is received; and a component for adjusting the second detection threshold to a higher value based on determining that feedback is received. In some embodiments, the apparatus further comprises: a component for determining that feedback from the second terminal device is not received; and a component for determining that the second terminal device has not received a sidelink transmission from the first terminal device based on the success of the second LBT process, or a component for determining that LBT for sending feedback at the second terminal device has failed based on the failure of the second LBT process.

[0145] In some embodiments, the means for determining a feedback configuration for the sidelink transmission includes: means for determining that the second LBT process is unsuccessful; and means for determining to disable feedback for the sidelink transmission from the second terminal device based on determining that the second LBT process is unsuccessful. In some embodiments, the apparatus further includes: means for sending the sidelink transmission to the second terminal device using at least one of link adaptation or at least one blind retransmission.

[0146] In some embodiments, the first LBT process and the second LBT process are performed simultaneously, the second LBT process is performed at the end of the first LBT process, or the second LBT process is performed after the first LBT process. In some embodiments, the second detection threshold is determined based on at least one of the following items: a portion of the first detection threshold, a size of a group of terminal devices to which the sidelink transmission is multicast, the second terminal device is one of the terminal devices in the group, a channel busy rate (CBR) associated with the sidelink transmission, a physical sidelink feedback channel (PSFCH) load associated with the sidelink transmission, a service priority of the sidelink transmission, or a service type of the sidelink transmission.

[0147] In some embodiments, the means for determining a feedback configuration for the sidelink transmission is further based on at least one of: a number of terminal devices to which the sidelink transmission is multicast, a PSFCH load associated with the sidelink transmission, or a determination that a second terminal device has a coverage issue. In some embodiments, the apparatus further comprises: means for receiving at least one of the first detection threshold or the second detection threshold from a network device.

[0148] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of method 500. In some embodiments, the means comprises at least one processor; and at least one memory comprising computer program code, the at least one memory and the computer program code being configured to implement execution of the apparatus together with the at least one processor.

[0149] In some embodiments, an apparatus capable of executing method 600 (eg, second terminal device 103) may include components for executing the various steps of method 600. The components may be implemented in any suitable form. For example, the components may be implemented in a circuit or a software module.

[0150] In some embodiments, the apparatus includes: a component for determining at a second terminal device whether a request is received from a first terminal device, the request being feedback regarding a side link transmission from the first terminal device to the second terminal device; a component for performing an LBT process based on determining that the request is received; a component for sending feedback to the first terminal device based on a success of the LBT process; and a component for avoiding sending feedback to the first terminal device based on determining that the request is not received.

[0151] In some embodiments, the apparatus further comprises: a component for sending feedback to the first terminal device for adjusting the threshold of the LBT process in the first terminal device, the feedback for adjusting the threshold of the LBT process in the first terminal device comprising: an indication of success of the LBT process in the second terminal device.

[0152] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of method 600. In some embodiments, the means comprises at least one processor; and at least one memory comprising computer program code, the at least one memory and the computer program code being configured to implement execution of the apparatus together with the at least one processor.

[0153] Figure 7 A simplified block diagram of a device 700 suitable for implementing some example embodiments of the present disclosure is illustrated. The device 700 may be provided for implementing a communication device, such as the first terminal device 101, the second terminal device 103, or the network device 105 shown in FIG. 1 or FIG. 2. As shown, the device 700 includes one or more processors 710, one or more memories 720 coupled to the processor 710, and one or more communication modules 740 coupled to the processor 710.

[0154] The communication module 740 is used for two-way communication. The communication module 740 has at least one antenna to facilitate communication. The communication interface may represent any interface required for communication with other network elements.

[0155] Processor 710 may be of any type suitable for the local technology network, and may include one or more of the following: 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 (as non-limiting examples). Device 800 may have multiple processors, such as application specific integrated circuit chips that are time slaved to a clock synchronized with a main processor.

[0156] The memory 720 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) 724, electrically programmable read-only memory (EPROM), flash memory, hard disk, compact disk (CD), digital video disk (DVD), and other magnetic and / or optical memories. Examples of volatile memories include, but are not limited to, random access memory (RAM) 722 and other volatile memories that do not persist during the duration of a power outage.

[0157] The computer program 830 includes computer executable instructions that are executed by the associated processor 710. The program 830 may be stored in the ROM 724. The processor 710 may perform any suitable operations and processes by loading the program 730 into the RAM 722.

[0158] The embodiments of the present disclosure may be implemented by a program 730, so that the device 700 may execute the program 730 as shown in FIG. Figure 6 Any process of the present disclosure discussed. The embodiments of the present disclosure may also be implemented by hardware or a combination of software and hardware.

[0159] In some example embodiments, the program 730 may be tangibly embodied in a computer-readable medium, which may be contained in the device 700 (e.g., in the memory 720) or in other storage devices accessible to the device 700. The device 700 may load the program 730 from the computer-readable medium into the RAM 722 for execution. The computer-readable medium may include any type of tangible non-volatile storage, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc.

[0160] Figure 8 800 according to some example embodiments of the present disclosure. The computer readable medium 800 has a program 730 stored thereon. Figure 8 Although computer-readable medium 800 is represented in the form of a CD or a DVD, computer-readable medium 800 may be in any other form suitable for carrying or storing program 730.

[0161] In general, the various embodiments of the present disclosure may be implemented by hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software, which may be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are illustrated and described in block diagrams, flow charts, or using some other graphical representations, it should be understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented by hardware, software, firmware, dedicated circuits or logic, general hardware or controllers or other computing devices, or some combination thereof.

[0162] 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 a program module, which are executed in a device on a target real or virtual processor to perform the above-mentioned reference FIG. 5 or Figure 6 The method 500 or 600 described. In general, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functions of program modules can be combined or split between program modules as needed. The machine executable instructions of program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in local and remote storage media.

[0163] The program code for executing the disclosed method can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device, so that when the program code is executed by the processor or controller, the functions / operations specified in the flow chart and / or block diagram are realized. The program code can be executed completely on the machine, can be executed partially on the machine, as an independent software package, partially executed on the machine and partially executed on a remote machine, or executed completely on a remote machine or server.

[0164] In the context of the present disclosure, computer program codes or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform the above-mentioned processes and operations. Examples of carriers include signals, computer-readable media, etc.

[0165] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer readable medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared or semiconductor systems, devices or apparatuses, or any suitable combination of the above. More specific examples of computer readable storage media include an electrical connection with one or more wires, a portable computer floppy 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.

[0166] In addition, although the operations are described in a particular order, this should not be construed as requiring that the operations be performed in the particular order shown or in a sequential order, or that all of the described operations be performed, in order to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although some specific implementation details are included in the above discussion, these details should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be unique to a particular embodiment. 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 separately in multiple embodiments or in any suitable sub-combination.

[0167] Although the present disclosure is described in language specific to structural features and / or methodological acts, it should be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Instead, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. The first terminal device comprises: at least one processor; as well as at least one memory storing instructions, which, when executed by the at least one processor, cause the first terminal device to at least: performing a first listen-before-talk (LBT) procedure based on a first detection threshold for a sidelink transmission to be sent from the first terminal device to a second terminal device; performing a second LBT process based on a second detection threshold lower than the first detection threshold; as well as Based on the result of the second LBT process, a feedback configuration for the sidelink transmission is determined.

2. The first terminal device according to claim 1, wherein the first terminal device is caused to determine the feedback configuration of the sidelink transmission by: Determining that the second LBT process is successful; and Based on determining that the second LBT process is successful, determine to enable feedback from the second terminal device for the sidelink transmission.

3. The first terminal device according to claim 2, wherein the first terminal device is further configured to: Sending a request for the feedback to the second terminal device.

4. The first terminal device according to claim 3, wherein the first terminal device is further configured to: receiving information for adjusting the second detection threshold from the second terminal device, adjusting the second detection threshold based on the information for adjusting the second detection threshold, The information for adjusting the second detection threshold includes: An indication of whether an LBT procedure performed by the second terminal device to send the feedback to the first terminal device was successful or unsuccessful.

5. The first terminal device according to any one of claims 3 to 4, wherein the first terminal device is further configured to: determining that the feedback is not received from the second terminal device; and Based on determining that the feedback was not received, the second detection threshold is adjusted to a lower value.

6. The first terminal device according to any one of claims 3 to 5, wherein the first terminal device is further configured to: determining that the feedback is received from the second terminal device; and Based on determining that the feedback is received, the second detection threshold is adjusted to a higher value.

7. The first terminal device according to any one of claims 1 to 6, wherein the first terminal device is further configured to: determining that the feedback is not received from the second terminal device; and determining that the second terminal device did not receive the sidelink transmission from the first terminal device based on the success of the second LBT process, or Based on the failure of the second LBT process, it is determined that the LBT at the second terminal device used to send the feedback has failed.

8. The first terminal device of claim 1 , wherein the first terminal device is caused to determine the feedback configuration of the sidelink transmission by: determining that the second LBT process is unsuccessful; and Based on determining that the second LBT process is unsuccessful, determine to disable feedback from the second terminal device for the sidelink transmission.

9. The first terminal device according to claim 8, wherein the first terminal device is further configured to: The side link transmission is sent to the second terminal device using at least one of link adaptation and at least one blind retransmission.

10. The first terminal device according to any one of claims 1 to 9, wherein: The first LBT process and the second LBT process are performed simultaneously, The second LBT process is performed when the first LBT process ends, or When the second terminal device intends to perform its own LBT process, the second LBT process is performed after the first LBT process.

11. The first terminal device according to any one of claims 1 to 10, wherein the second detection threshold is determined based on at least one of the following items: a portion of the first detection threshold, the size of a group of terminal devices to which the sidelink transmission is multicast, the second terminal device being one of the group of terminal devices, a channel busy rate (CBR) associated with the sidelink transmission, a physical sidelink feedback channel (PSFCH) load associated with the sidelink transmission, The service priority of the side link transmission, or The service type transmitted by the side link.

12. The first terminal device according to any one of claims 1 to 11, wherein the first terminal device determines the feedback configuration of the sidelink transmission further based on at least one of the following items: the number of terminal devices to which the sidelink transmission is multicast, the PSFCH payload associated with the sidelink transmission, or The second terminal device has a determination of a coverage problem.

13. The first terminal device according to any one of claims 1 to 12, wherein the first terminal device is further configured to: At least one of the first detection threshold or the second detection threshold is received from a network device.

14. The first terminal device according to any one of claims 1-13, wherein the first terminal device is configured to determine whether to request HARQ feedback for each transport block (TB).

15. A second terminal device, comprising: at least one processor; as well as at least one memory storing instructions, which, when executed by the at least one processor, cause the second terminal device to at least: determining whether a request is received from a first terminal device, the request being for feedback regarding a sidelink transmission from the first terminal device to the second terminal device; Based on determining that the request is received, performing an LBT process; Based on the success of the LBT process, sending feedback to the first terminal device; as well as Based on determining that the request is not received, avoiding sending the feedback to the first terminal device.

16. The second terminal device according to claim 15, wherein the second terminal device is further configured to: sending information for adjusting a threshold value in the LBT process in the first terminal device to the first terminal device, The information for adjusting the threshold in the LBT process in the first terminal device includes: An indication of success of the LBT process in the second terminal device.

17. A method comprising: performing, at a first terminal device, a first listen-before-talk (LBT) procedure based on a first detection threshold for a sidelink transmission to be sent from the first terminal device to a second terminal device; performing a second LBT process based on a second detection threshold lower than the first detection threshold; as well as Based on the result of the second LBT process, a feedback configuration for the sidelink transmission is determined.

18. A method comprising: determining, at a second terminal device, whether a request is received from a first terminal device, the request being for feedback regarding a sidelink transmission from the first terminal device to the second terminal device; Based on determining that the request is received, performing an LBT process; Based on the success of the LBT process, sending feedback to the first terminal device; as well as Based on determining that the request is not received, avoiding sending the feedback to the first terminal device.

19. An apparatus comprising: means for performing, at a first terminal device, a first listen-before-talk (LBT) procedure based on a first detection threshold for a sidelink transmission to be sent from the first terminal device to a second terminal device; means for performing a second LBT procedure based on a second detection threshold lower than the first detection threshold; as well as Means for determining a feedback configuration for the sidelink transmission based on a result of the second LBT process.

20. An apparatus comprising: means for determining, at a second terminal device, whether a request is received from a first terminal device, the request being for feedback regarding a sidelink transmission from the first terminal device to the second terminal device; means for performing an LBT process based on determining that the request is received; means for sending feedback to the first terminal device based on the success of the LBT process; as well as The method further comprises: configuring the device to avoid sending the feedback to the first terminal device based on determining that the request has not been received.

21. A non-transitory computer-readable medium comprising program instructions, which, when executed by a device, cause the device to at least perform the method according to claim 17 or 18.

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