Apparatus, method, and computer readable medium for sidelink communication

Abstract

The embodiment of the invention relates to a method and equipment for sidelink communication, and a computer readable medium. A first device obtains a configuration of a first PSFCH resource in a secondary band. The first PSFCH resource is used to respond to HARQ feedback information of sidelink data transmission from the second device in an unlicensed band in operation. The secondary frequency band includes a non-congested unlicensed frequency band, or a frequency band in which a channel access procedure is not required. The first device determines whether HARQ feedback information is to be transmitted on a first PSFCH resource in a secondary band. And the first equipment sends the HARQ feedback information to the second equipment on the first PSFCH resource according to the determined HARQ feedback information to be sent on the first PSFCH resource in the auxiliary frequency band.

Description

Technical Field

[0001] Implementations of the present disclosure relate generally to the field of telecommunications, and more particularly to devices, methods, and computer-readable media for sidelink communications. Background Art

[0002] New Radio (NR) supports sidelinks to provide reliable, low-latency, and high-speed device-to-device (D2D) communications for various applications, especially in vehicle-to-everything (V2X) scenarios. In the NR sidelink, a user equipment (UE) can transmit to one or more UEs via unicast, multicast, or broadcast with or without network control. A hybrid automatic repeat request (HARQ) mechanism is also introduced in the NR sidelink to ensure the reliability of the sidelink transmission. Summary of the invention

[0003] The independent claims define the scope of protection of various embodiments of the present invention. [Embodiments / Examples] and features (if any) described in this specification that do not belong to the scope of the independent claims are to be interpreted as examples that help understand the various embodiments of the present invention.

[0004] Note that the term "embodiment" or "example" should be adapted accordingly to the terms used in this application, i.e., if the term "example" is used, the statement should accordingly talk about "example"; or if the term "embodiment" is used, the statement should accordingly talk about "embodiment".

[0005] In general, example implementations of the present disclosure provide devices, methods, and computer-readable media for sidelink communications.

[0006] In a first aspect, a first device is provided. The first device includes at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, together with the at least one processor, enable the first device to: obtain the configuration of a first physical sidelink feedback channel (PSFCH) resource in an auxiliary frequency band, the first PSFCH resource being used to respond to a hybrid automatic repeat request (HARQ) feedback information of a sidelink data transmission from a second device in an unlicensed frequency band in operation, the auxiliary frequency band including: a non-congested unlicensed frequency band, or a frequency band in which a channel access process is not required; and send HARQ feedback information to the second device on the first PSFCH resource based on determining that the HARQ feedback information is to be sent on the first PSFCH resource in the auxiliary frequency band.

[0007] In a second aspect, a second device is provided. The second device includes at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, together with the at least one processor, enable the second device to: obtain the configuration of a first PSFCH resource in an auxiliary frequency band, the first PSFCH resource being used to respond to HARQ feedback information of a sidelink data transmission from a second device in an unlicensed frequency band in operation, the auxiliary frequency band including: a non-congested unlicensed frequency band, or a frequency band in which a channel access process is not required; determine whether to receive HARQ feedback information on the first PSFCH resource in the auxiliary frequency band; and receive HARQ feedback information from the first device on the first PSFCH resource based on determining that the HARQ feedback information is to be received on the first PSFCH resource in the auxiliary frequency band.

[0008] In a third aspect, a method implemented at a first device is provided. The method includes: obtaining a configuration of a first PSFCH resource in a secondary frequency band, the first PSFCH resource being used to respond to HARQ feedback information of a sidelink data transmission from a second device in an operating unlicensed frequency band, the secondary frequency band comprising: a non-congested unlicensed frequency band, or a frequency band in which a channel access process is not required; and sending HARQ feedback information to the second device on the first PSFCH resource based on determining that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band.

[0009] In a fourth aspect, a method implemented at a second device is provided. The method includes: obtaining a configuration of a first PSFCH resource in an auxiliary frequency band, the first PSFCH resource being used to respond to HARQ feedback information of a sidelink data transmission from a second device in an operating unlicensed frequency band, the auxiliary frequency band comprising: a non-congested unlicensed frequency band, or a frequency band in which a channel access process is not required; determining whether to receive HARQ feedback information on the first PSFCH resource in the auxiliary frequency band; and receiving HARQ feedback information from the first device on the first PSFCH resource based on determining that the HARQ feedback information is to be received on the first PSFCH resource in the auxiliary frequency band.

[0010] In a fifth aspect, an apparatus is provided. The apparatus includes: a component for acquiring a configuration of a first PSFCH resource in a secondary frequency band, the first PSFCH resource being used to respond to HARQ feedback information of a sidelink data transmission from a second device in an operating unlicensed frequency band, the secondary frequency band comprising: a non-congested unlicensed frequency band, or a frequency band in which a channel access process is not required; and a component for sending HARQ feedback information to the second device on the first PSFCH resource in accordance with determining that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band.

[0011] In a sixth aspect, an apparatus is provided. The apparatus includes: a component for acquiring, at a second device, a configuration of a first PSFCH resource in a secondary frequency band, the first PSFCH resource being used to respond to HARQ feedback information of a sidelink data transmission from the second device in an operating unlicensed frequency band, the secondary frequency band comprising: a non-congested unlicensed frequency band, or a frequency band in which a channel access process is not required; a component for determining whether to receive the HARQ feedback information on the first PSFCH resource in the secondary frequency band; and a component for receiving the HARQ feedback information from the first device on the first PSFCH resource based on determining that the HARQ feedback information is to be received on the first PSFCH resource in the secondary frequency band.

[0012] In a seventh aspect, a non-transitory computer-readable medium is provided, wherein the non-transitory computer-readable medium comprises program instructions for causing an apparatus to execute the method according to the third aspect.

[0013] In an eighth aspect, a non-transitory computer-readable medium is provided, wherein the non-transitory computer-readable medium comprises program instructions for causing an apparatus to execute the method according to the fourth aspect.

[0014] It should be understood that the invention summary is not intended to determine the key or essential features of the implementation of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features, and advantages of the present disclosure will become more apparent through a more detailed description of some implementations of the present disclosure in the accompanying drawings, in which:

[0016] Figure 1 illustrates an example communication network in which implementations of the present disclosure may be implemented;

[0017] Figure 2 illustrates an example of acquisition of channel occupancy time (COT) according to some implementations of the present disclosure;

[0018] Figure 3 illustrates an example of a contention window countdown process according to some implementations of the present disclosure;

[0019] Figure 4 and Figure 5 illustrates examples of allowed gaps to which a Type 2 Listen Before Talk (LBT) process according to some implementations of the present disclosure is applicable;

[0020] Figure 6 An example is illustrated in which an initiating device communicates with a plurality of responding devices via a sidelink (SL) using different types of LBT procedures under respectively acquired COTs according to an implementation;

[0021] Figure 7 illustrates an example of NR SL resource allocation in Mode 2 according to some implementations of the present disclosure;

[0022] Figure 8 illustrates an example of an SL slot structure according to some implementations of the present disclosure;

[0023] Fig. 9 illustrates an example of mapping between PSSCH resources and PSFCH resources according to some implementations of the present disclosure;

[0024] Fig.10 illustrates a signaling diagram illustrating a process for transmission of HARQ feedback information according to some implementations of the present disclosure;

[0025] Fig.11 illustrates an example of allocation of PSFCH resources in a secondary frequency band according to some implementations of the present disclosure;

[0026] Fig.12 illustrates an example of allocation of PSFCH resources in a secondary frequency band according to other implementations of the present disclosure;

[0027] Fig.13 A flowchart illustrating an example method according to some implementations of the present disclosure;

[0028] Fig.14 illustrates a flow chart of another example method according to some implementations of the present disclosure;

[0029] Fig.15 illustrates a simplified block diagram of an apparatus suitable for implementing embodiments of the present disclosure; and

[0030] Fig.16 A block diagram of an example computer-readable medium is illustrated in accordance with some implementations of the present disclosure.

[0031] Throughout the drawings, the same or similar reference numerals refer to the same or similar elements. DETAILED DESCRIPTION

[0032] The principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described only for illustrative purposes and help those skilled in the art to understand and implement the present disclosure, and do not represent any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in various other ways except for the way described below.

[0033] 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.

[0034] In this disclosure, references to "one embodiment," "an embodiment," and "an example embodiment," etc., 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, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, those skilled in the art recognize that it is within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0035] It should be understood that although the terms "first" and "second" etc. can be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the exemplary embodiment, the first element can be referred to as the second element, and similarly, the second element can be referred to as the first element. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0036] The term used herein is only used to describe specific embodiments, but is not intended to limit exemplary embodiments. The singular form "one", "one" and "the" used herein also include plural forms, unless the context clearly states otherwise. It is further understood that the term "includes", "comprising", "has", "has", "contains" and / or "contains" specifies the existence of the features, elements and / or components when used in this article, but does not exclude the existence or addition of one or more other features, elements, components and / or their combinations. As used in this article, "at least one of the following items: <list of two or more elements>" and "at least one of the lists of <two or more elements>" and similar wording (wherein the list of two or more elements is connected by "and" or "or") refer to at least any one element in these elements, or at least any two or more elements in these elements, or at least all elements in these elements.

[0037] As used in this application, the term "circuitry" may refer to one, more, or all of the following:

[0038] (a) a pure hardware circuit implementation (such as an implementation using only analog and / or digital circuitry), and

[0039] (b) a combination of hardware circuitry and software such as (where applicable):

[0040] (i) a combination of analog and / or digital hardware circuits and software / firmware, and

[0041] (ii) any portion of hardware processor(s) (including digital signal processor(s)) with software, software and memory(s) that work together to enable a device (such as a mobile phone or server) to perform various functions), and

[0042] (c) Hardware circuits and / or processor(s), such as microprocessor(s) or portions of microprocessor(s), that require software (e.g., firmware) to operate, but in which case the software may not be present when not required for operation.

[0043] This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its accompanying software and / or firmware. For example, if applicable to a particular claim element, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0044] 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 multiplexing (WCDMA), high speed packet access (HSPA), narrowband Internet of Things (NB-IoT), etc. In addition, the communication between the terminal equipment and the network equipment in the communication network can be performed according to any suitable generation of communication protocol, including but not limited to the first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, future fifth generation (5G) communication protocol, and / or any other protocol currently known or to be developed in the future. The embodiments of the present disclosure can be applied to various communication systems. Considering the rapid development of communication, there will certainly be communication technologies and systems that can be used to embody future types of the present disclosure. It should not be regarded as limiting the scope of the present disclosure to the above-mentioned system.

[0045] 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 the network. 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 relay, a low-power node (such as a femto, a pico), etc.), depending on the terminology and technology applied. .

[0046] The term "terminal device" refers to any terminal device capable of wireless communication. As an example and not limitation, the terminal device may also be referred to as a communication device, a user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS) or an access terminal (AT). The terminal device may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a voice over IP (VoIP) phone, a wireless local loop phone, a tablet computer, a wearable terminal device, a personal digital assistant (PDA), a portable computer, a desktop computer, an image capture terminal device (such as a digital camera), a game terminal device, a music storage and playback device, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop embedded device (LEE), a laptop mounted device (LME), a USB dongle, a smart device, a wireless customer premises equipment (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head mounted display (HMD), a vehicle, a drone, medical equipment and applications (e.g., remote surgery), industrial equipment and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain environments), consumer electronic devices, equipment operating on commercial and / or industrial wireless networks, etc. In the following description, the terms "terminal device", "communication device", "terminal", "user equipment", and "UE" may be used interchangeably.

[0047] Figure 1 1 illustrates a schematic diagram of an example communication network 100 in which implementations of the present disclosure may be implemented. Figure 1 As shown, the communication network 100 may include: a first device 110, a second device 120, and a third device 130. The third device 130 may communicate with the first device 110 and the second device 120 via corresponding wireless communication channels.

[0048] In this example, for ease of discussion only, the first device 110 and the second device 120 are illustrated as vehicles that enable V2X communication, and the third device 130 is illustrated as a network device serving the vehicles 110 and 120. It should be understood that the vehicle and the network device are merely example implementations of the first device 110, the second device 120, and the third device 130, respectively, and do not represent any limitation on the scope of the present application. Any other suitable implementation is also possible.

[0049] It should be understood that Figure 1 The number of devices 110, 120, and 130 given in FIG. 1 is for illustration only and does not represent any limitation to the present disclosure. Communication network 100 may include any suitable number of devices suitable for implementing the present disclosure.

[0050] The communication in the communication network 100 may conform to any suitable standard, including but not limited to Global System for Mobile Communications (GSM), LTE, LTE Evolution, Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), GSMEDGE Radio Access Network (GERAN), Machine Type Communication (MTC), etc. In addition, the communication may be performed according to any generation of communication protocols currently known or to be developed in the future. Examples of communication protocols include but are not limited to first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G) communication protocols.

[0051] In one example, communications in the communication network 100 may be performed in a new radio (NR) operation in an unlicensed band. In some implementations, communications in the communication network 100 may include SL communications 112 and 122. For example, via the SL communication 122, the second device 120 performs a sidelink data transmission to the first device 110. Via the SL communication 112, the first device 110 sends HARQ feedback information associated with the sidelink data transmission to the second device 120.

[0052] Unauthorized Operation Background

[0053] In unlicensed bands below 7 GHz, new radio (NR) coexistence with other systems (e.g., IEEE 802.11) can be ensured via an LBT channel access mechanism. According to the channel access mechanism, a user equipment (UE) (such as the first device 110 or the second device 120) that intends to perform SL communication (such as SL communication 112 or 122) may need to first successfully complete an LBT check before initiating the same SL communication. Hereinafter, the LBT process may also be referred to as a clear channel assessment (CCA) or a channel access process.

[0054] In order for a UE to pass the LBT check, it must observe whether the channel is available for a number of consecutive CCA slots. Below 7GHz, these slots are 9μs in duration. If the measured power (i.e., the energy collected during a CCA slot) is below a regulatory threshold (which may depend on the operating band and geographic region), the UE considers the channel to be available in the CCA slot.

[0055] In one example, when a UE (e.g., first device 110) plays the role of an initiating device for initiating communication with a responding device (e.g., second device 120), the initiating UE may need to obtain "rights" to access a channel for a specific period of time by applying an "extended" LBT procedure, such as COT in the regulations, in which the channel must be considered idle for the entire duration of the contention window (CW). This "extended" LBT procedure is generally referred to as a Type 1 LBT procedure or LBT Type 1 procedure as specified in TS 37.213. The procedure is as follows Figure 2 as shown in .

[0056] Figure 2 Both the CW duration and the COT duration in may depend on the channel access priority (CAPC) associated with the traffic of the UE (e.g., p=1 to p=4), as shown in Table 1. Control plane traffic (such as the physical sidelink control channel (PSCCH)) may be transmitted with a priority of p=1, while the priority of user plane traffic is p>1. Table 1 details Type 1 LBT in the Uu uplink (UL) case. It may be noted that in the downlink (DL) case, in principle, Type 1 LBT parameters may also be adopted in the SL.

[0057] Table 1

[0058]

[0059] Table 1 shows the CAPC for UL. The contention window length in the CCA slot associated with each CAPC has a minimum value (CW min,p ) and maximum value (CW max,p ). The duration of COT is determined by T ulm,cot,p Given.

[0060] An example of behavior during the contention window countdown is Figure 3 It should be noted that if the LBT check fails in any CCA slot during the countdown process, the countdown process will stop and will only resume when the channel is considered idle during the hold-off time (ie, the LBT check is successful).

[0061] exist Figure 3 In, T d Indicates the delay time, T sl represents the duration of the CCA slot, and N represents the number of CCA slots that need to be considered idle before the contention window countdown is completed. Specifically, Figure 3 The example of the Type 1 LBT contention window countdown process and how to interrupt it is shown. In example (a), when the delay time T dWhen both the timer and the countdown are not interrupted (i.e., the channel is not detected as busy during the sensing time slot). In example (b), the delay time T d is interrupted (ie, the channel is detected as busy during the deferral time sensing slot). In example (c), the contention window countdown is interrupted (ie, the channel is detected as busy during the countdown sensing slot).

[0062] After successfully completing the execution of the Type 1 LBT procedure and performing a transmission (e.g., to the first device 110), the UE that initiated the transmission (also referred to as the initiating device, e.g., the second device 120) may obtain a COT having a duration associated with the priority p in the corresponding CAPC. The obtained COT may be valid even in the case where the initiating device may suspend its transmission, although if the initiating device wants to perform a new transmission (within the COT), it may still need to perform a "simplified" LBT procedure. This "simplified" LBT procedure is generally referred to as a Type 2 LBT procedure or LBT Type 2 procedure, with the following variations:

[0063] ● Type 2A (25μs LBT) – used for SL transmission within the COT acquired by the initiating device (if the gap between two SL transmissions is ≥ 25μs, and the SL transmission is after another SL transmission), such as Figure 4 Example (c) and Figure 5 As shown in example (f) in ;

[0064] Type 2B (16μs LBT) - used for SL transmission within the COT acquired by the initiating device (can only be used for SL transmission after another SL with a gap exactly equal to 16μs), such as Figure 4 Example (b) and Figure 5 As shown in example (e) in;

[0065] ● Type 2C (without LBT) - can only be used for SL transmission after another SL, the gap is <16μs, and the allowed duration of SL transmission is ≤584μs, such as Figure 4 Example (a) and Figure 5 As shown in example (d) in .

[0066] In addition, examples (a), (b), and (c) illustrate the case where the gap is located between two transmissions from the same initiating UE (i.e., device 110), while examples (d), (e), and (f) respectively illustrate the case where the gap is located between two different transmissions from the initiating UE (e.g., second device 120) and the responding UE (e.g., first device 110).

[0067] An initiating device (e.g., the second device 120) may share its acquired COT with its intended receiver, also referred to as a responding device (e.g., the first device 110). To do this, the initiating device shall inform the responding device (e.g., via control signaling) of the duration of the COT. The responding device then uses this information to decide which type of LBT procedure should be applied when performing a transmission where the intended receiver is the initiating device. If the responding device transmission falls outside the COT, the responding device will have to use Type 1 LBT with the appropriate class p in the CAPC to acquire a new COT. This will refer to Figure 6 Give a description.

[0068] Figure 6 An example is shown in which an initiating device communicates with multiple responding devices through a side link using different types of LBT processes under respectively acquired COTs according to one implementation. Figure 6 , the initiating device (i.e., UE A) may first use a Type 1 LBT process 610 to acquire a new COT 605. The initiating device (UE A) may then transmit to the first responding device (UE B) via a sidelink transmission 615 on the PSCCH and / or a physical sidelink shared channel (PSSCH). In addition, UE A may share its acquired COT 605 with UE B. UE B may then use the acquired COT 605 information to decide which type of LBT process should be applied when performing a transmission to UE A as the intended receiver. In practice, UE A may notify UE B (e.g., via control signaling) of the duration of the COT 605 within the SL transmission 615. In response, UE B may be configured to perform a Type 2 LBT process 620 and send SL feedback information 625 to UE A on the PSFCH.

[0069] Alternatively, UE B may communicate with another responding device (e.g., UE C). In the case where the transmission from UE B to UE C falls outside the duration of COT 605, UE B may need to use a Type 1 LBT process 635 to acquire a new COT 630 according to the appropriate class p in the CAPC. UE B may then send a SL transmission 640 to UE C on the PSCCH and / or PSSCH and share its acquired COT 630 with UE C. UE C may use the COT 630 information to decide which type of LBT process UE C should apply when performing a transmission to UE B as an intended receiver. In practice, UE B may inform UE C (e.g., via control signaling) of the duration of COT 630 within the SL transmission 640. In response, UE C may be configured to perform a Type 2 LBT process 645 and send SL feedback information 650 to UE B on the PSFCH.

[0070] If UE A wants to perform a transmission to UE C, UE A may need to use a Type 1 LBT process 660 with an appropriate CAPC to obtain another new COT 655. For example, UE A may need to use a Type 1 LBT process 660 with an appropriate class p in the CAPC to obtain a new COT 655. UE A can send a SL transmission 665 to UE C on the PSCCH and / or PSSCH. In addition, UE A can also share the duration in the acquired COT 655 with UE C (e.g., via control signaling). UE C can then use this duration information of COT 655 to decide which type of LBT process UE C should apply when performing a transmission to UE A as an intended receiver. After receiving the SL transmission 665 with the duration information of COT 655, UE C can successfully perform a Type 2 LBT process 670 and send SL feedback information 675 to UE A on the PSFCH.

[0071] NR-SL Overview

[0072] NR SL is designed to facilitate UEs to communicate with nearby (multiple) other UEs via direct / SL communications. Two resource allocation modes have been specified, and a SL transmitter (TX) UE (such as the first device 110 or the second device 120) is configured with one of the two resource allocation modes to perform its NR SL transmissions. These modes are represented as NR SL Mode 1 and NR SL Mode 2. In Mode 1, sidelink transmission resources are allocated or scheduled to the SL TX UE by a network device (such as the third device 130), while the SL TX UE in Mode 2 autonomously selects its SL transmission resources.

[0073] In mode 1, the network device (such as the third device 130) is responsible for SL resource allocation, and the configuration and operation are similar to the configuration and operation on the Uu interface, such as Figure 1 In Mode 1, a single resource pool may be configured that spans the entire spectrum including (multiple) unavailable portions, but the network device only schedules subchannels containing available PRBs. When the UE has data to send, it may request resources from the network device to send an SR via the SL-BSR MAC CE or via the PUCCH resources configured for the SL logical channel, as shown in Figure 1 The dynamic sidelink grant DCI (DCI format 3_0) can grant sidelink resources for up to three transmissions of a transport block. The network device can also provide one or more configuration grants to allocate periodic sidelink resources. 38.321 Section 5.8.3 gives the MAC level details of this process.

[0074] Figure 7An example of NR SL resource allocation in Mode 2 is illustrated. In Mode 2, the SL UE autonomously performs resource selection with the help of a sensing process. More specifically, the SL TX UE in NR SL Mode 2 first performs a sensing process on the configured one or more SL transmission resource pools in order to obtain knowledge of one or more reserved resources by at least one other nearby SL TX UE. Based on the knowledge acquired from the sensing, the SL TX UE can select at least one resource from the available SL resources accordingly. In order for the SL UE to perform sensing and acquire the information required to receive SL transmissions, it needs to decode the sidelink control information (SCI). In Release 16, the SCI associated with data transmission includes a first-level SCI and a second-level SCI.

[0075] Sidelink Control Information (SCI)

[0076] The SCI follows a two-level SCI structure, the main motivation of which is to support the size difference between SCIs for various NR-V2X SL service types (e.g., broadcast, multicast, and unicast).

[0077] The first level SCI may include SCI format 1-A carried by PSCCH. The first level SCI contains at least one of the following items: information for enabling sensing operation, or information required to determine resource allocation of PSSCH and decode second level SCI. Table 2 shows an example of the content of the first level SCI.

[0078] Table 2

[0079]

[0080]

[0081]

[0082] The second level SCI may include SCI formats 2-A and 2-B, which are carried by PSSCH (multiplexed with SL-SCH) and contain at least one of the following:

[0083] ●Source and destination identities

[0084] ● Information used to identify and decode the associated SL-SCH TB

[0085] ●HARQ feedback control in unicast / multicast

[0086] ● Trigger CSI feedback in unicast

[0087] Table 3 shows an example of the content of the second-level SCI.

[0088] Table 3

[0089]

[0090]

[0091] SL physical layer structure

[0092] The configuration of resources in the sidelink resource pool defines the minimum information required for the RX UE to be able to decode the transmission, including the number of subchannels, the number of PRBs per subchannel, the number of symbols in the PSCCH, which time slots have PSFCH, and other configuration aspects not relevant to the present invention.

[0093] However, the details of the actual sidelink transmission (ie, payload) are provided for each individual transmission in the PSCCH (first level SCI), including: time and frequency resources, DMRS configuration for PSSCH, MCS, PSFCH, etc.

[0094] An example of SL time slot structure is as follows Figure 8 As shown in , where example (a) shows a time slot with PSCCH / PSSCH, while example (b) shows a time slot with PSCCH / PSSCH, where the last symbol is used for PSFCH.

[0095] Table 4 shows the PSSCH DMRS configuration based on the number of symbols used and the duration of the PSCCH.

[0096] Table 4

[0097]

[0098]

[0099] The configuration of the PSCCH (e.g., DMRS, MCS, number of symbols used) is part of the resource pool configuration. In addition, an 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 pattern, and MCS) is provided by the first level SCI, which is the payload sent within the PSSCH and follows the configuration shown in Table 4.

[0100] SL HARQ Operation

[0101] PSFCH was introduced during Release 16 to enable HARQ feedback on the sidelink from the UE that is the intended recipient of a PSSCH transmission (i.e., RXUE) to the UE that performs the transmission (i.e., TX UE). Within the PSFCH, the Zadoff-Chu sequence in one PRB is repeated over two OFDM symbols, the first of which can be used for AGC, near the end of the sidelink resources in the slot. Figure 8 Example (b) of FIG. 4 provides example time slot formats of PSCCH, PSSCH, and PSFCH. A Zadoff-Chu sequence is configured or pre-configured per sidelink resource pool as a basic sequence.

[0102] According to TS 38.331, the time resource of PSFCH is configured or preconfigured to occur once every 0, 1, 2, or 4 time slots. The HARQ feedback resource (PSFCH resource) is derived from the resource location of PSCCH / PSSCH.

[0103] For PSSCH to HARQ timing, there is a configuration parameter K in units of time slots. The timing of the PSFCH is determined by K. For PSSCH transmission with the last symbol in time slot n, the HARQ feedback is 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 gap of at least K time slots allows the processing delay of the RX UE to be taken into account when decoding the PSCCH and generating HARQ feedback. K can be equal to 2 or 3, and a single K value can be configured or pre-configured for each resource pool. This allows several RX UEs using the same resource pool to use the same mapping of (multiple) PSFCH resources for HARQ feedback. By parameter K, the N PSSCH time slots associated with the time slot with PSFCH can be determined.

[0104] Fig. 9 An example of mapping between PSSCH resources and PSFCH resources according to some implementations of the present disclosure is illustrated. Fig. 9 In the example of , the period of the PSFCH resource is configured as N=4 (i.e., there will be 4 PSSCH time slots associated with PSFCH), and K(sl-MinTimeGapPSFCH) is configured as 2. There are L subchannels in the resource pool, and N PSSCH time slots are associated with the time slot containing PSFCH, then there are N*L subchannels associated with the PSFCH symbol. In the PSFCH symbol, there are M physical resource blocks (PRBs) available for PSFCH, so there are M PRBs available for HARQ feedback transmitted on N*L subchannels.

[0105] If M is configured as a multiple of N*L, then different sets of M can be set= M / (N*L) PRBs are associated with the HARQ feedback for each subchannel in the PSFCH period. The first group M of the M PRBs available for PSFCH set The second group M PRBs are associated with the HARQ feedback transmitted in the first subchannel in the first time slot. set The first PRB is associated with the HARQ feedback transmitted in the first subchannel in the second time slot, and so on.

[0106] like Fig. 9 As shown, N=4, L=3, and all PRBs in a PSFCH symbol can be used for PSFCH. In this example, the HARQ feedback transmitted at PSSCH x is M in the corresponding PSFCH symbol. set The PRBs are transmitted on a set x of PRBs, where x=1, ..., 12.

[0107] In case of ACK / NACK feedback for multicast communication (option 2) or in case of different PSSCH transmissions in the same subchannel, a set of M associated with a subchannel set The PRBs are shared among multiple RX UEs.

[0108] For each PRB available for PSFCH, there are Q cyclic shift pairs available to support ACK or NACK feedback for Q RX UEs within the PRB. The number of cyclic shift pairs Q is (pre-)configured for a resource pool and can be equal to 1, 2, 3, or 6.

[0109] We can calculate the number of PSFCH resources F available to support HARQ feedback for a given transmission (in TS38.213, F is denoted as ). For each PSFCH resource used by one RX UE, F available PSFCH resources may be used for ACK / NACK feedback of up to F RX UEs.

[0110] The F PSSCH resources that can be used for HARQ feedback multiplexing of PSSCH can be determined according to two options:

[0111] a) Based on the L PSSCH subchannels used by PSSCH, where F can be calculated

[0112] Calculated as:

[0113] ○F = L PSSCH*Mset*Q PSFCH (associated with the L PSSCH subchannel of PSSCH)

[0114] ○Among them,

[0115] ■L represents the number of PSSCH subchannels;

[0116] ■M set represents the number of PRBs of the PSFCH associated with each subchannel; and

[0117] ■Q represents the available cyclic shift pairs in each PRB.

[0118] b) Or, based only on the starting subchannel used by the PSSCH (ie, based only on one subchannel in the case of L PSSCHs>1).

[0119] ○F = Mset*Q PSFCH (associated with the starting subchannel of PSSCH)

[0120] ○Among them,

[0121] ■M set represents the PRB number of the PSFCH associated with each subchannel; and

[0122] ■Q represents the available cyclic shift pairs in each PRB.

[0123] Similar to PUCCH in Release 15 NR Uu, the available F PSFCH resources are indexed based on PRB index (frequency domain) and cyclic shift pair index (code domain).

[0124] The mapping of PSFCH index i (i=1, 2, ..., F) to PRBs and to Q cyclic shift pairs makes PSFCH index i first increase with the increase of PRB index until the number of available PRBs for PSFCH is reached. Then, it increases with the increase of cyclic shift pair index, and also increases with the increase of PRB index, and so on.

[0125] Among the F PSFCHs available for HARQ feedback for a given transmission, the RX UE selects the PSCCH with index i for its HARQ feedback, given by:

[0126] i=(T ID +R ID )mod F

[0127] Where T ID is the layer 1 ID of the TX UE (indicated in the level 2 SCI). For unicast ACK / NACK feedback and multicast NACK-only feedback, R ID =0 (option 1).

[0128] For multicast ACK / NACK feedback (option 2), R ID= is equal to the RX UE identifier within the group, which is indicated by the higher layer. For a certain number X of RX UEs within the group, the RX UE identifier is an integer between 0 and X-1. The RX UE determines which PRB and cyclic shift pair should be used to send its HARQ feedback based on the PSFCH index i. The RX UE uses the first cyclic shift or the second cyclic shift in the cyclic shift pair associated with the selected PSFCH index i to send a NACK or ACK, respectively.

[0129] By selecting the PSFCH with index i by the RX UE, the TX UE can distinguish the HARQ feedback of (multiple) different RX UEs (via the RX UE identifier, e.g. for multicast option 2) and the HARQ feedback for the TX UE (via the Layer 1 ID of the TX UE, e.g. for unicast). ID = 0, RX UE is based only on layer 1 ID TX UE identifier T ID The same PSFCH index is selected for its NACK-only feedback.

[0130] Occupied Channel Bandwidth (OCB) Requirements

[0131] The scope of NR in unlicensed spectrum is limited to the sub-7 GHz band. For this frequency range, the following spectrum regulatory requirements for UL physical channel design come from EU regulations.

[0132] ETSI specifies that the OCB should be between 80% and 100% of the declared nominal channel bandwidth.

[0133] According to the latest ETSI regulations, during the COT period, a device can temporarily operate while occupying less than 80% of its nominal channel bandwidth (minimum 2MHz).

[0134] The regulations on maximum power spectral density are usually expressed in 1MHz resolution bandwidth. The ETSI specification requires a maximum power spectral density (PSD) of 10dBm / MHz for 5150-5350MHz. It requires a resolution of 10KHz to test the 1MHz PSD constraint, and therefore, the maximum PSD constraint should be met in any occupied 1MHz bandwidth.

[0135] In addition, regulations also specify the total maximum transmit power EIRP for specific frequency bands, for example, ETSI has an EIRP limit of 23dBm for 5150-5350MHz.

[0136] Regulatory constraints on OCB and PSD guide the design choices for the uplink channels of NR unlicensed systems.

[0137] In NR-SL, a SL Tx device can request HARQ feedback for its PSSCH transmission, and there are two types of HARQ feedback available in NR-SL:

[0138] (i) ACK / NACK based, which is applicable to unicast and multicast HARQ option 2;

[0139] (ii) NACK-only feedback for multicast HARQ option 1.

[0140] For (i), it is well known that in HARQ operation, for some reason, the Tx device may not receive the expected HARQ feedback from the Rx device, which results in the detection of HARQ feedback DTX at the Tx device. The HARQ feedback DTX can be regarded as NACK received, and therefore, the Tx UE device can decide to perform HARQ retransmission of the TB when detecting the HARQ feedback DTX from the Rx device. For (ii), if there is HARQ feedback DTX, the Tx UE assumes that the TB is successfully received, and therefore will not perform HARQ retransmission.

[0141] Let us consider the SL HARQ operation between a Tx UE and an Rx UE for unicast SL in unlicensed spectrum, referred to as SL-U. Due to a possible LBT failure at the Rx UE, the Rx UE may not be able to send HARQ feedback to the Tx UE on the PSFCH at time slot n+a as expected for the HARQ transmission (retransmission) of time slot n, and hence HARQ feedback DTX may be detected at the Tx UE. This is referred to as the SL-U HARQ feedback DTX problem. Note that the same problem may occur, for example, in LTE-NR SL coexistence in shared resources, where the Rx UE of the NR SL may not be able to send HARQ feedback to its Tx UE because the LTE UE is transmitting in the expected PSFCH time slot.

[0142] In summary, PSFCH transmissions in unlicensed bands from RX UEs are prone to LBT failures, which may result in unnecessary retransmissions, as case (i) will further exacerbate the occurrence of LBT failures, while case (ii) will prevent necessary retransmissions. Providing multiple PSFCH opportunities can reduce this problem, but it comes at the cost of requiring more PSFCH resources and increasing HARQ latency. In addition, PSFCH in unlicensed bands needs to meet strict OCB and PSD requirements, which incurs additional overhead and complexity in order to comply with regulations.

[0143] The implementation of the present disclosure provides a solution for transmitting HARQ feedback information to solve the above problems and one or more other potential problems. According to the solution, conditional resource mapping is introduced to map HARQ feedback information corresponding to PSSCH transmission to PSSCH feedback transmission on auxiliary frequency band. The auxiliary frequency band includes: a non-congested unlicensed frequency band, or a frequency band in which a channel access process is not required. Therefore, the HARQ DTX problem caused by LBT failure is alleviated.

[0144] In the following, reference will be made to Figures 10 to 16 The principles of the present disclosure are described.

[0145] Fig.10 FIG. 1 is a signaling diagram illustrating a transmission process 1000 of HARQ feedback information according to some example embodiments of the present disclosure. For the purpose of discussion, reference will be made to FIG. Figure 1 Process 1000 is described. Process 1000 may involve Figure 1 The first device 110, the second device 120 and the third device 130 are shown. Figure 1 The process 1000 is described in the communication network 100 of FIG. 1 , but the process can also be applied to other communication scenarios.

[0146] As shown, the first device 110 obtains the configuration of the first PSFCH resource in the auxiliary frequency band. The first PSFCH resource is used to respond to the HARQ feedback information of the sidelink data transmission from the second device 120 in the unlicensed frequency band in operation. The auxiliary frequency band is different from the unlicensed frequency band in operation. The auxiliary frequency band includes: a non-congested unlicensed frequency band, or a frequency band in which a channel access process is not required.

[0147] In some embodiments, the first device 110 may receive 1010 a configuration of a first PSFCH resource in a secondary frequency band from the third device 130. For example, for operation in Mode 1, the third device 130 may allocate PSFCH resources and indicate to the first device 110 in a sidelink grant downlink control information (DCI) or as part of an RRC configuration (e.g., for semi-persistent scheduling (SPS) or configuration grant (CG)).

[0148] Alternatively, the configuration of the first PSFCH resource may be pre-configured in the configuration of the sidelink resource pool.For example, for operation in Mode 2, the mapping of the PSFCH to the secondary frequency band may be configured as part of the configuration of the sidelink resource pool.

[0149] In some embodiments, determining whether a channel in an unlicensed frequency band is congested may be based on a channel busy rate (CBR) or a channel occupancy rate (CR) measurement level. If the CBR or CR is above a certain threshold, the channel is determined to be congested; otherwise, the channel is determined to be uncongested. If at least one channel of the unlicensed frequency band is determined to be uncongested, the unlicensed frequency band may be determined to be uncongested.

[0150] In some embodiments, measurement and reporting of CBR for sidelink communications may be configured through radio resource control (RRC) signaling.

[0151] In other embodiments, determining whether the unlicensed band is congested can be based on consistent LBT failures in the unlicensed band. In other words, if the LBT failure counter exceeds a certain threshold for a period of time, the unlicensed band can be determined to be congested; otherwise, the unlicensed band can be determined to be uncongested.

[0152] In some embodiments, examples of frequency bands where a channel access procedure is not required may include, but are not limited to, an Intelligent Transportation System (ITS) band and a FR2 band.

[0153] Continue to refer Fig.10 , the first device 110 determines 1040 whether the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band.

[0154] If the HARQ feedback information is to be sent on the first PSFCH resource in the secondary band, the first device 110 sends 1050 the HARQ feedback information on the first PSFCH resource to the second device 120. Otherwise, in some embodiments, the HARQ feedback information may be sent on the second PSFCH resource in the operating unlicensed band.

[0155] In some embodiments, the first device 110 may perform a channel access procedure to transmit HARQ feedback information in a second PSFCH resource in an operating unlicensed band. If the channel access procedure in the second PSFCH resource fails, the first device 110 may determine that the HARQ feedback information is to be sent on a first PSFCH resource in a secondary band.

[0156] In some embodiments, if the first device 110 determines that the resources used for transmission of HARQ feedback information include only the first PSFCH resources in the auxiliary frequency band, the first device 110 may determine that the HARQ feedback information is to be sent on the first PSFCH resource without performing a channel access process to transmit the HARQ feedback information in the unlicensed frequency band in the operation.

[0157] In some embodiments, the first device 110 may receive 1030 an indication from the second device 120 that HARQ feedback information is to be sent on a first PSFCH resource in the secondary frequency band. Alternatively, the first device 110 may receive the indication from a third device 130 serving the first device 110. For example, in 1010, the first device 110 may receive an indication that HARQ feedback information is to be sent on a first PSFCH resource together with a configuration of a first PSFCH resource in the secondary frequency band.

[0158] Furthermore, the first device 110 may determine, based on the indication, that the HARQ feedback information is to be sent on the first PSFCH resource.

[0159] In some embodiments, the first device 110 may determine that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band by determining at least one of the following:

[0160] ● the CBR in the operating unlicensed band is above a first threshold,

[0161] ● the priority of the sidelink data transmission is higher than the second threshold,

[0162] ●The reliability requirement of HARQ feedback information is higher than the third threshold,

[0163] ●The delay requirement of HARQ feedback information is higher than the fourth threshold,

[0164] The service quality level of the HARQ feedback information is higher than the fifth threshold,

[0165] ● the number of failures of a channel access procedure for transmission of HARQ feedback information in the unlicensed band in operation within the first observation window is higher than a sixth threshold,

[0166] ● The type of propagation for sidelink data transmission is multicast,

[0167] ● Lack of effective shared COT associated with the unlicensed band in operation, or

[0168] ● Lack of time to acquire a new COT to transmit HARQ feedback information in the operating unlicensed band,

[0169] ● the CBR in the secondary band is below the eighth threshold, or

[0170] ● The number of failures in the channel access process for transmission of HARQ feedback information in the auxiliary frequency band within the second observation window is higher than a ninth threshold.

[0171] In some embodiments, the lack of a valid COT can be determined based on determining that the first device 110, the second device 120, or any other device has not yet initiated a COT that ends after the second PSFCH resource transmission time, or any device has previously provided a COT sharing indication with sufficient COT duration to be transmitted on the second PSVCH resource.

[0172] In some embodiments, for example, for the case of HARQ option 1 in multicast (e.g., requesting additional retransmissions, where as the number of retransmissions increases, it is less likely that another terminal device will require retransmissions), if the number of retransmissions of a transport block (TB) associated with the HARQ feedback information is higher than a seventh threshold, the first device 110 may determine that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band.

[0173] In some embodiments, if the first device 110 determines to trigger HARQ retransmission for sidelink data transmission before a discontinuous reception (DRX) off period begins, the first device 110 may determine that the HARQ feedback information is to be sent on a first PSFCH resource in the secondary frequency band. For example, if the first device 110 may expect to enter a long DRX off period within x time slots and therefore wishes to trigger HARQ retransmission before the DRX off period begins, the first device 110 may determine that the HARQ feedback information is to be sent on a first PSFCH resource in the secondary frequency band.

[0174] In some embodiments, the first device 110 may determine that there will be no time to acquire the COT based on an estimate of the duration of the channel access procedure. For example, if the time interval associated with the contention window of the channel access procedure is longer than the time interval until the first PSFCH resource, there will be no time to complete the channel access procedure in the unlicensed band in operation.

[0175] In some embodiments, the first device 110 may send 1020 to the second device 120 an indication that the first device 110 will switch to the auxiliary frequency band for transmitting HARQ feedback information. For example, the first device 110 may send the indication through high-layer signaling, MAC CE, or RRC signaling based on at least one of the standards described above. For example, based on determining that the CBR in the unlicensed frequency band in operation is higher than the first threshold, or the number of failures of the channel access process for transmission of HARQ feedback information in the unlicensed frequency band in operation within the observation window is higher than the sixth threshold, the first device 110 may send the indication.

[0176] In some embodiments, if the first device 110 has sent an indication to the second device 120 that the first device 110 will switch to the secondary frequency band, the first device 110 will also determine to use the first PSFCH resource.

[0177] In some embodiments, the configuration of the first PSFCH resource in the secondary frequency band indicates at least one of the following:

[0178] ● the time resources included in the first PSFCH resource,

[0179] ● the frequency resources included in the first PSFCH resource,

[0180] ● sequence resources included in the first PSFCH resource,

[0181] an association between a sidelink data transmission in a subchannel of a sidelink resource pool in an operating unlicensed band and a first PSFCH resource in a secondary band,

[0182] ● a frequency offset between the first PSFCH resource and the second PSFCH resource in the unlicensed band of operation, or

[0183] • A time offset between a first PSFCH resource and a second PSFCH resource in an operating unlicensed band.

[0184] In some embodiments, if the HARQ feedback information is successfully transmitted to the second device 120 on the second PSFCH resource in the operating unlicensed band, the first device 110 may release the first PSFCH resource.

[0185] Continue to refer Fig.10 , on the second device 120 side, the second device 120 obtains the configuration of the first PSFCH resource in the secondary frequency band.

[0186] In some embodiments, the second device 120 may receive 1015 a configuration of a first PSFCH resource in the secondary frequency band from the third device 130. Alternatively, the configuration of the first PSFCH resource may be pre-configured in the configuration of the sidelink resource pool.

[0187] Furthermore, the second device 120 determines 1060 whether to receive HARQ feedback information on the first PSFCH resource in the secondary frequency band.

[0188] If the HARQ feedback information is to be received on the first PSFCH resource in the secondary frequency band, the second device 120 receives the HARQ feedback information from the first device 110 on the first PSFCH resource.

[0189] In some embodiments, the second device 120 may detect HARQ feedback information in the second PSFCH resource in the operating unlicensed band. If there is no HARQ feedback information in the operating unlicensed band, the second device 120 may determine that the HARQ feedback information is to be received on the first PSFCH resource in the secondary band.

[0190] In some embodiments, the second device 120 may send 1030 an indication to the first device 110 that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary band. Further, the second device 120 may determine based on the indication that the HARQ feedback information is to be received on the first PSFCH resource.

[0191] In some embodiments, the second device 120 may receive 1020 an indication from the first device 110 that the first device 110 will switch to the secondary frequency band for transmitting HARQ feedback information. Further, the second device 120 may determine that the HARQ feedback information is to be received on the first PSFCH resource based on the indication.

[0192] In some embodiments, if the HARQ feedback information is successfully received from the first device 110 on the second PSFCH resource in the operating unlicensed band, the second device 120 may release the first PSFCH resource.

[0193] Through process 1000, the transmission of HARQ feedback information in the auxiliary frequency band not affected by the LBT failure is more reliable. In other words, there is no risk that the HARQ feedback information is not sent. Therefore, process 1000 can avoid the HARQ DTX problem and unnecessary retransmission caused by the loss of HARQ feedback information due to the LBT failure.

[0194] Furthermore, through process 1000, lower PSFCH resource overhead and lower HARQ delay may be achieved.

[0195] Furthermore, the OCB and PSD requirements apply only to unlicensed bands. To meet these requirements, the PSFCH may need to be repeated in frequency (in interlaced RBs) along the operating band. If the HARQ feedback information is sent in the first PSFCH resource in a secondary band that is a licensed band or an ITS band, then these requirements do not apply. Therefore, the complexity and overhead are lower since interlacing does not need to be used.

[0196] Fig.11 An example of allocation of a first PSFCH resource in a secondary frequency band according to some implementations of the present disclosure is illustrated. Fig.11 In the example of , the resources on the time slot of the secondary frequency band where the first PSFCH resource is mapped may not be dedicated to sidelink transmission. In other words, these resources can be used for downlink (DL) or uplink (UL) transmission, and the physical resource blocks (PRBs) of DL / UL are rate matched (i.e., mapped) around the first PSFCH resource, such as Fig.11As shown in . The first PSFCH resource in the secondary frequency band may also include an AGC symbol and a guard interval before and after the PSFCH symbol.

[0197] In this example, the mapping of HARQ feedback information to the first PSFCH resource in the secondary band follows a mapping similar to the conventional mapping, except that the first PSFCH resource has a frequency offset when comparing the operating band of the sidelink resource pool to the secondary band. PRBs, the PSFCH allocation for time slot i and subchannel j is

[0198] [(i+j·N)×M,(i+1+j·N)×M-1]+δ, where S represents the number of subchannels in the sidelink resource pool, N represents the number of PSSCH time slots associated with one PSFCH time slot, N can be equal to 1, 2, or 4, M represents the number of PRBs for PSFCH per subchannel and time slot, and δ represents the frequency offset between the first PSFCH resource in the secondary band and the second PSFCH resource in the unlicensed band in operation. If δ is not configured or δ is configured to 0, the use of the first PSFCH resource in the secondary band is deactivated. If δ is not configured to 0, the use of the first PSFCH resource in the secondary band is activated.

[0199] Fig.12 FIG. 4 illustrates an example of allocation of PSFCH resources in a secondary frequency band according to other implementations of the present disclosure. Fig.12 In the example of , the first device 110 may be configured with a PSFCH resource in an operating unlicensed band and a first PSFCH resource in an auxiliary band. In addition, the first device 110 may use the first PSFCH resource in the auxiliary band only if there is no available COT for transmission of HARQ feedback information by the first device 110 in an operating unlicensed band. In this case, if the second device 120 has provided a COT sharing indication to the first device 110, such as via an SCI, or if the second device 120 has previously received a COT sharing indicator from the first device 110, the second device 120 may determine that the COT is available.

[0200] Alternatively, the first PSFCH resource in the secondary band is used only when the first device 110 experiences an LBT failure, in which case, if it is determined that the first device 110 has not yet initiated the transmission of HARQ feedback information in the time slot of the PSFCH in the operating unlicensed band, the second device 120 will be forced to monitor whether the PSFCH resource first appears in the operating unlicensed band and then appears in the secondary band. In addition, in this case, the transmission of HARQ feedback information in the operating unlicensed band and the secondary band may not be in the same time slot. For example, if the second device 120 does not find a PSFCH resource in the operating unlicensed band in time slot n, the second device 120 will further detect the first PSFCH resource in the secondary band in time slot (n+a), where according to the same HARQ feedback information, there is a time offset "a" between the first PSFCH resource in the secondary band and the PSFCH resource in the operating unlicensed band. On the other hand, if the HARQ feedback information is successfully transmitted or received in the operating unlicensed band, the first PSFCH resource in the secondary band may be released.

[0201] In some embodiments, the time offset may be 0 or higher than 0, depending on, for example, the capabilities of the first device 110 and the processing time for deciding whether the first PSFCH resource in the secondary frequency band should be used.

[0202] Given that the first PSFCH in the secondary band may not be used if the unlicensed band in operation is not congested, in some implementations, the same PSFCH resource may be reused as a secondary resource for multiple RPs in the unlicensed band. Therefore, the resource utilization of the PSFCH allocated in the secondary band can be improved. In the case of reusing the same PSFCH resource in the secondary band, conflicts may occasionally occur, so different codes or sequences may be used during mapping to identify the first PSFCH resources in the secondary band of different devices.

[0203] Fig.13 1300 according to some implementations of the present disclosure. In some implementations, the method 1300 can be implemented at a device such as Figure 1 For the purpose of discussion, without loss of generality, reference will be made to the device 110 or the device 120. Figure 1 A method 1300 performed by the first device 110 is described.

[0204] At block 1310, the first device 110 obtains a configuration of a first PSFCH resource in a secondary frequency band, the first PSFCH resource being used to respond to HARQ feedback information of a sidelink data transmission from a second device in an operating unlicensed frequency band. The secondary frequency band includes: a non-congested unlicensed frequency band, or a frequency band in which a channel access procedure is not required.

[0205] At block 1320, the first device 110 determines whether HARQ feedback information is to be sent on a first PSFCH resource in the secondary frequency band.

[0206] At block 1330 , if it is determined that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band, the first device 110 sends the HARQ feedback information to the second device on the first PSFCH resource.

[0207] In some embodiments, determining that HARQ feedback information is to be sent on a first PSFCH resource in a secondary frequency band includes: performing a channel access process to transmit HARQ feedback information in a second PSFCH resource in an unlicensed frequency band in a transmission operation; and based on a failure of the channel access process, determining that the HARQ feedback information is to be sent on a first PSFCH resource in the secondary frequency band.

[0208] In some embodiments, determining that HARQ feedback information is to be sent on the first PSFCH resource in the auxiliary frequency band includes: based on determining that the resources used for transmission of HARQ feedback information only include the first PSFCH resource in the auxiliary frequency band, determining that the HARQ feedback information is to be sent on the first PSFCH resource without performing a channel access process to transmit the HARQ feedback information in an unlicensed band in the operation.

[0209] In some embodiments, determining that HARQ feedback information is to be sent on a first PSFCH resource in a secondary frequency band includes: receiving an indication from a second device, or a third device serving the first device, that HARQ feedback information is to be sent on a first PSFCH resource in a secondary frequency band; and based on the indication, determining that the HARQ feedback information is to be sent on the first PSFCH resource.

[0210] In some embodiments, determining that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band is determined by determining at least one of the following:

[0211] The congestion busy rate (CBR) in the operating unlicensed band is higher than a first threshold,

[0212] ● the priority of the sidelink data transmission is higher than the second threshold,

[0213] ●The reliability requirement of HARQ feedback information is higher than the third threshold,

[0214] ●The delay requirement of HARQ feedback information is higher than the fourth threshold,

[0215] The service quality level of the HARQ feedback information is higher than the fifth threshold,

[0216] ● the number of failures of the channel access procedure for transmission of HARQ feedback information in the unlicensed band in operation within the first observation window is higher than a sixth threshold,

[0217] ● The type of propagation for sidelink data transmission is multicast,

[0218] ● Lack of effective shared channel occupation time (COT) associated with operating unlicensed bands,

[0219] ● Lack of time to acquire a new COT to transmit HARQ feedback information in the operating unlicensed band,

[0220] ● the number of retransmissions of the transport block associated with the HARQ feedback information is higher than a seventh threshold,

[0221] ● triggering HARQ retransmissions for sidelink data transmission before the DRX Off period starts, or

[0222] ● the CBR in the secondary band is below the eighth threshold, or

[0223] ● The number of failures in the channel access process for transmission of HARQ feedback information in the auxiliary frequency band within the second observation window is higher than a ninth threshold.

[0224] In some embodiments, the method 1300 further includes: sending an indication to the second device that the first device will switch to the auxiliary frequency band for transmitting the HARQ feedback information.

[0225] In some embodiments, the configuration of the first PSFCH resource in the secondary frequency band indicates at least one of the following:

[0226] ● the time resources included in the first PSFCH resource,

[0227] ● the frequency resources included in the first PSFCH resource,

[0228] ● sequence resources included in the first PSFCH resource,

[0229] an association between a sidelink data transmission in a subchannel of a sidelink resource pool in an operating unlicensed band and a first PSFCH resource in a secondary band,

[0230] ● a frequency offset between the first PSFCH resource and the second PSFCH resource in the unlicensed band of operation, or

[0231] • A time offset between a first PSFCH resource and a second PSFCH resource in an operating unlicensed band.

[0232] In some embodiments, the configuration of the first PSFCH resource is received from a third device serving the first device.

[0233] In some embodiments, the configuration of the first PSFCH resource is pre-configured in the configuration of the sidelink resource pool.

[0234] In some embodiments, the method 1300 further comprises: performing rate matching of physical resource blocks of a downlink or uplink transmission channel around the first PSFCH resource in the secondary frequency band.

[0235] Fig.14 1400 according to some implementations of the present disclosure. In some implementations, the method 1400 can be implemented at a device such as Figure 1 For the purpose of discussion, without loss of generality, reference will be made to the device 110 or the device 120. Figure 1 A method 1400 performed by the second device 120 is described.

[0236] At block 1410, the second device 120 obtains a configuration of a first PSFCH resource in a secondary frequency band. The first PSFCH resource is used for HARQ feedback information in response to a sidelink data transmission from the second device 120 in an operating unlicensed frequency band. The secondary frequency band includes: a non-congested unlicensed frequency band, or a frequency band in which a channel access procedure is not required.

[0237] At block 1420, the second device 120 determines whether to receive HARQ feedback information on a first PSFCH resource in the secondary frequency band.

[0238] At block 1430 , if it is determined that the HARQ feedback information is to be received on the first PSFCH resource in the secondary frequency band, the second device 120 receives the HARQ feedback information from the first device on the first PSFCH resource.

[0239] In some embodiments, determining that HARQ feedback information is to be received on a first PSFCH resource in an auxiliary frequency band includes: detecting HARQ feedback information in a second PSFCH resource in an operating unlicensed frequency band; and determining that the HARQ feedback information is to be received on a first PSFCH resource in the auxiliary frequency band based on determining that no HARQ feedback information is present in the operating unlicensed frequency band.

[0240] In some embodiments, determining that HARQ feedback information is to be received on a first PSFCH resource in the auxiliary frequency band includes: sending an indication to a first device that HARQ feedback information is to be sent on a first PSFCH resource in the auxiliary frequency band; and based on the indication, determining that the HARQ feedback information is to be received on the first PSFCH resource.

[0241] In some embodiments, determining that the HARQ feedback information is to be received on a first PSFCH resource in the secondary frequency band comprises: determining that the HARQ feedback information is to be received on a first PSFCH resource in the secondary frequency band by determining at least one of the following:

[0242] The congestion busy rate (CBR) in the operating unlicensed band is higher than a first threshold,

[0243] ● the priority of the sidelink data transmission is higher than the second threshold,

[0244] ●The reliability requirement of HARQ feedback information is higher than the third threshold,

[0245] ●The delay requirement of HARQ feedback information is higher than the fourth threshold,

[0246] The service quality level of the HARQ feedback information is higher than the fifth threshold,

[0247] ● the number of failures of the channel access procedure for transmission of HARQ feedback information in the unlicensed band in operation within the first observation window is higher than a sixth threshold,

[0248] ● The type of propagation for sidelink data transmission is multicast,

[0249] ● Lack of effective shared channel occupation time (COT) associated with operating unlicensed bands,

[0250] ● Lack of time to acquire a new COT to transmit HARQ feedback information in the operating unlicensed band,

[0251] ● the number of retransmissions of the transport block associated with the HARQ feedback information is higher than a seventh threshold,

[0252] ● triggering HARQ retransmissions for sidelink data transmission before the DRX Off period starts,

[0253] ● the CBR in the secondary band is below the eighth threshold, or

[0254] ● The number of failures in the channel access process for transmission of HARQ feedback information in the auxiliary frequency band within the second observation window is higher than a ninth threshold.

[0255] In some embodiments, determining that HARQ feedback information is to be received on a first PSFCH resource in an auxiliary frequency band includes: determining that HARQ feedback information is to be received on a first PSFCH resource in an auxiliary frequency band by: receiving an indication from a first device that the first device will switch to an auxiliary frequency band for transmitting HARQ feedback information; and based on the indication, determining that the HARQ feedback information is to be received on the first PSFCH resource.

[0256] In some embodiments, the configuration of the first PSFCH resource indicates at least one of the following:

[0257] ● the time resources included in the first PSFCH resource,

[0258] ● the frequency resources included in the first PSFCH resource,

[0259] ● sequence resources included in the first PSFCH resource,

[0260] an association between a sidelink data transmission in a subchannel of a sidelink resource pool in an operating unlicensed band and a first PSFCH resource in a secondary band,

[0261] ● a frequency offset between the first PSFCH resource and the second PSFCH resource in the unlicensed band of operation, or

[0262] • A time offset between a first PSFCH resource and a second PSFCH resource in an operating unlicensed band.

[0263] In some embodiments, the configuration of the first PSFCH resource is received from a third device serving the first device.

[0264] In some embodiments, the configuration of the first PSFCH resource is pre-configured in the configuration of the sidelink resource pool.

[0265] In some embodiments, the method 1400 further comprises: releasing the first PSFCH resource based on determining that the HARQ feedback information is successfully received from the first device on the second PSFCH resource in the operating unlicensed band.

[0266] In some example implementations, an apparatus (e.g., first device 110) capable of performing any of the methods 1300 may include a component for performing the corresponding steps of the method 1300. The component may be implemented in any suitable form. For example, the component may be implemented in a circuit system or a software module.

[0267] In some example implementations, the apparatus includes: a component for acquiring a configuration of a first PSFCH resource in an auxiliary frequency band, the first PSFCH resource being used to respond to HARQ feedback information for sidelink data transmission from a second device in an operating unlicensed frequency band, the auxiliary frequency band comprising: a non-congested unlicensed frequency band, or a frequency band in which a channel access process is not required; a component for determining whether the HARQ feedback information is to be sent on the first PSFCH resource in the auxiliary frequency band; and a component for sending the HARQ feedback information to the second device on the first PSFCH resource based on determining that the HARQ feedback information is to be sent on the first PSFCH resource in the auxiliary frequency band.

[0268] In some embodiments, the component for determining that HARQ feedback information is to be sent on a first PSFCH resource in an auxiliary frequency band includes: a component for performing a channel access process to transmit HARQ feedback information in a second PSFCH resource in an unlicensed frequency band in operation; and a component for determining that HARQ feedback information is to be sent on a first PSFCH resource in an auxiliary frequency band based on a failure of the channel access process.

[0269] In some embodiments, the component for determining that HARQ feedback information is to be sent on the first PSFCH resource in the auxiliary frequency band includes: a component for determining that the HARQ feedback information is to be sent on the first PSFCH resource based on determining that the resources used for transmission of the HARQ feedback information only include the first PSFCH resource in the auxiliary frequency band without performing a channel access process for transmitting the HARQ feedback information in an unlicensed frequency band in operation.

[0270] In some embodiments, the component for determining that HARQ feedback information is to be sent on the first PSFCH resource in the auxiliary frequency band includes: a component for receiving an indication from a second device, or a third device serving the first device, that HARQ feedback information is to be sent on the first PSFCH resource in the auxiliary frequency band; and a component for determining, based on the indication, that the HARQ feedback information is to be sent on the first PSFCH resource.

[0271] In some embodiments, the means for determining that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band comprises: means for determining that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band by determining at least one of the following:

[0272] The congestion busy rate (CBR) in the operating unlicensed band is higher than a first threshold,

[0273] ● the priority of the sidelink data transmission is higher than the second threshold,

[0274] ●The reliability requirement of HARQ feedback information is higher than the third threshold,

[0275] ●The delay requirement of HARQ feedback information is higher than the fourth threshold,

[0276] The service quality level of the HARQ feedback information is higher than the fifth threshold,

[0277] ● the number of failures of the channel access procedure for transmission of HARQ feedback information in the unlicensed band in operation within the first observation window is higher than a sixth threshold,

[0278] ● The type of propagation for sidelink data transmission is multicast,

[0279] ● Lack of effective shared channel occupation time (COT) associated with operating unlicensed bands,

[0280] ● Lack of time to acquire a new COT to transmit HARQ feedback information in the operating unlicensed band,

[0281] ● the number of retransmissions of the transport block associated with the HARQ feedback information is higher than a seventh threshold,

[0282] ● triggering HARQ retransmissions for sidelink data transmission before the DRX Off period starts, or

[0283] ● the CBR in the secondary band is below the eighth threshold, or

[0284] ● The number of failures in the channel access process for transmission of HARQ feedback information in the auxiliary frequency band within the second observation window is higher than a ninth threshold.

[0285] In some embodiments, the apparatus further comprises means for sending an indication to the second device that the first device will switch to the secondary frequency band for transmitting the HARQ feedback information.

[0286] In some embodiments, the configuration of the first PSFCH resource in the secondary frequency band indicates at least one of the following:

[0287] ● the time resources included in the first PSFCH resource,

[0288] ● the frequency resources included in the first PSFCH resource,

[0289] ● sequence resources included in the first PSFCH resource,

[0290] an association between a sidelink data transmission in a subchannel of a sidelink resource pool in an operating unlicensed band and a first PSFCH resource in a secondary band,

[0291] ● a frequency offset between the first PSFCH resource and the second PSFCH resource in the unlicensed band of operation, or

[0292] • A time offset between a first PSFCH resource and a second PSFCH resource in an operating unlicensed band.

[0293] In some embodiments, the configuration of the first PSFCH resource is received from a third device serving the first device.

[0294] In some embodiments, the configuration of the first PSFCH resource is pre-configured in the configuration of the sidelink resource pool.

[0295] In some embodiments, the apparatus further comprises means for performing rate matching of physical resource blocks of a downlink or uplink transmission channel around the first PSFCH resource in the secondary frequency band.

[0296] In some example implementations, an apparatus (e.g., second device 120) capable of performing any of the methods 1400 may include a component for performing the corresponding steps of the method 1400. The component may be implemented in any suitable form. For example, the component may be implemented in a circuit system or a software module.

[0297] In some example implementations, the apparatus includes: a component for obtaining, at a second device, a configuration of a first physical sidelink feedback channel (PSFCH) resource in an auxiliary frequency band, the first PSFCH resource being used to respond to hybrid automatic repeat request (HARQ) feedback information for sidelink data transmission from the second device in an operating unlicensed frequency band, the auxiliary frequency band comprising: a non-congested unlicensed frequency band, or a frequency band in which a channel access process is not required; a component for determining whether to receive HARQ feedback information on the first PSFCH resource in the auxiliary frequency band; and a component for receiving HARQ feedback information from the first device on the first PSFCH resource based on determining that the HARQ feedback information is to be received on the first PSFCH resource in the auxiliary frequency band.

[0298] In some embodiments, the component for determining that HARQ feedback information is to be received on a first PSFCH resource in an auxiliary frequency band includes: a component for detecting HARQ feedback information in a second PSFCH resource in an operating unlicensed frequency band; and a component for determining that HARQ feedback information is to be received on a first PSFCH resource in an auxiliary frequency band based on determining that no HARQ feedback information is present in the operating unlicensed frequency band.

[0299] In some embodiments, the component for determining that HARQ feedback information is to be received on the first PSFCH resource in the auxiliary frequency band includes: a component for sending an indication to the first device that HARQ feedback information is to be sent on the first PSFCH resource in the auxiliary frequency band; and a component for determining that the HARQ feedback information is to be received on the first PSFCH resource based on the indication.

[0300] In some embodiments, the means for determining that the HARQ feedback information is to be received on the first PSFCH resource in the secondary frequency band comprises: means for determining that the HARQ feedback information is to be received on the first PSFCH resource in the secondary frequency band by determining at least one of the following:

[0301] The congestion busy rate (CBR) in the operating unlicensed band is higher than a first threshold,

[0302] ● the priority of the sidelink data transmission is higher than the second threshold,

[0303] ●The reliability requirement of HARQ feedback information is higher than the third threshold,

[0304] ●The delay requirement of HARQ feedback information is higher than the fourth threshold,

[0305] The service quality level of the HARQ feedback information is higher than the fifth threshold,

[0306] ● the number of failures of the channel access procedure for transmission of HARQ feedback information in the unlicensed band in operation within the first observation window is higher than a sixth threshold,

[0307] ● The type of propagation for sidelink data transmission is multicast,

[0308] ● Lack of effective shared channel occupation time (COT) associated with operating unlicensed bands,

[0309] ● Lack of time to acquire a new COT to transmit HARQ feedback information in the operating unlicensed band,

[0310] ● the number of retransmissions of the transport block associated with the HARQ feedback information is higher than a seventh threshold,

[0311] ● triggering HARQ retransmissions for sidelink data transmission before the DRX Off period starts,

[0312] ● the CBR in the secondary band is below the eighth threshold, or

[0313] ● The number of failures in the channel access process for transmission of HARQ feedback information in the auxiliary frequency band within the second observation window is higher than a ninth threshold.

[0314] In some embodiments, a component for determining that HARQ feedback information is to be received on a first PSFCH resource in an auxiliary frequency band includes: a component for determining that HARQ feedback information is to be received on a first PSFCH resource in an auxiliary frequency band by: receiving an indication from a first device that the first device will switch to the auxiliary frequency band for transmitting HARQ feedback information; and based on the indication, determining that the HARQ feedback information is to be received on the first PSFCH resource.

[0315] In some embodiments, the configuration of the first PSFCH resource indicates at least one of the following:

[0316] ● the time resources included in the first PSFCH resource,

[0317] ● the frequency resources included in the first PSFCH resource,

[0318] ● sequence resources included in the first PSFCH resource,

[0319] an association between a sidelink data transmission in a subchannel of a sidelink resource pool in an operating unlicensed band and a first PSFCH resource in a secondary band,

[0320] ● a frequency offset between the first PSFCH resource and the second PSFCH resource in the unlicensed band of operation, or

[0321] • A time offset between a first PSFCH resource and a second PSFCH resource in an operating unlicensed band.

[0322] In some embodiments, the configuration of the first PSFCH resource is received from a third device serving the first device.

[0323] In some embodiments, the configuration of the first PSFCH resource is pre-configured in the configuration of the sidelink resource pool.

[0324] In some embodiments, the apparatus further comprises: releasing the first PSFCH resource based on determining that the HARQ feedback information is successfully received from the first device on the second PSFCH resource in the operating unlicensed frequency band.

[0325] Fig.15 1 is a simplified block diagram of a device 1500 suitable for implementing embodiments of the present disclosure. The device 1500 may be provided to implement a communication device, such as Figure 1 The first device 110 (eg, Rx UE) or the second device 120 (eg, Tx UE) is shown. As shown in the figure, the device 1500 includes: one or more processors 1510, one or more memories 1520 coupled to the processor 1510, and one or more communication modules 1540 coupled to the processor 1510.

[0326] The communication module 1540 is used for two-way communication. The communication module 1540 has at least one antenna to facilitate communication. The communication interface may represent any interface required for communication with other network elements.

[0327] Processor 1510 may be of any type suitable for the local technology network, and may include, as non-limiting examples, one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 1500 may have multiple processors, such as application specific integrated circuit chips that are time slaved to a clock synchronized with a main processor.

[0328] Memory 1520 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) 1524, electrically programmable read-only memory (EPROM), flash memory, hard disk, compact disk (CD), digital video disk (DVD), and other magnetic storage devices and / or optical storage. Examples of volatile memories include, but are not limited to, random access memory (RAM) 1522 and other volatile memories that do not persist during power outages.

[0329] Computer program 1530 includes computer executable instructions executed by associated processor 1510. Program 1530 may be stored in ROM 1524. Processor 1510 may perform any suitable actions and processes by loading program 1530 into RAM 1522.

[0330] The embodiments of the present disclosure may be implemented by the program 1530 so that the device 1500 may execute the reference Figures 1 to 14 Any process of the present disclosure discussed. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0331] In some example embodiments, the program 1530 may be tangibly embodied in a computer-readable medium that may be included in the device 1500 (such as in the memory 1520) or in other storage devices accessible to the device 1500. The device 1500 may load the program 1530 from the computer-readable medium to the RAM 1522 for execution. The computer-readable medium may include any type of tangible non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Fig.16 An example of computer readable medium 1600 is shown in the form of a CD or DVD. The computer readable medium has program 1530 stored thereon.

[0332] Generally, various embodiments of the present disclosure may be implemented using hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented using hardware, while other aspects may be implemented using firmware or software that 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 as 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 using hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0333] 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 reference Fig.13 and Fig.14 Methods 1300 and 1400 are described. Typically, 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 both local and remote storage media.

[0334] The program code for executing the method of the present disclosure 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 the program code is implemented when executed by the processor or controller in the flow chart and / or the block diagram. The program code can be executed completely on the machine, partially on the machine, as an independent software package, partially on the machine and partially on a remote machine, or completely on a remote machine or server.

[0335] 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 various processes and operations as described above. Examples of carriers include signals, computer readable media, etc.

[0336] The computer readable medium can be a computer readable signal medium or a computer readable storage medium. The computer readable medium can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared or semiconductor systems, devices or equipment, or any suitable combination of the foregoing. A more specific example of a computer readable storage medium will 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 foregoing.

[0337] In addition, although the operations are described in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown or in order or performing all the operations shown to obtain the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be interpreted as limitations on the scope of the present disclosure, but rather descriptions of features that may be specific to a particular embodiment. Certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination.

[0338] Although the disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A first device, comprising: at least one processor; as well as at least one memory including computer program code; wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the first device to: Obtaining a configuration of a first physical sidelink feedback channel (PSFCH) resource in a secondary frequency band, the first PSFCH resource being used to respond to hybrid automatic repeat request (HARQ) feedback information for a sidelink data transmission from a second device in an operating unlicensed frequency band, the secondary frequency band comprising: a non-congested unlicensed frequency band, or a frequency band in which a channel access procedure is not required; determining whether the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band; and According to determining that the HARQ feedback information is to be sent on the first PSFCH resource in the auxiliary frequency band, the HARQ feedback information is sent to the second device on the first PSFCH resource.

2. The first device of claim 1 , wherein the first device is further configured to determine that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band by: performing the channel access procedure for transmitting the HARQ feedback information in a second PSFCH resource in the operating unlicensed frequency band; and Based on the failure of the channel access procedure, it is determined that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band.

3. The first device of claim 1 , wherein the first device is further caused to determine that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band by: Based on determining that the resources used for transmitting the HARQ feedback information only include the first PSFCH resources in the auxiliary frequency band, it is determined that the HARQ feedback information is to be sent on the first PSFCH resources without performing the channel access process to transmit the HARQ feedback information in the unlicensed frequency band in the operation.

4. The first device of claim 1 , wherein the first device is further caused to determine that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band by: Receiving, from the second device or a third device serving the first device, an indication that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band; and Based on the indication, it is determined that the HARQ feedback information is to be sent on the first PSFCH resource.

5. The first device of claim 1 , wherein the first device is further caused to determine that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band by determining at least one of the following: A congestion busy rate (CBR) in the unlicensed band in operation is higher than a first threshold, The priority of the sidelink data transmission is higher than a second threshold, The reliability requirement of the HARQ feedback information is higher than a third threshold, The delay requirement of the HARQ feedback information is higher than a fourth threshold, The service quality level of the HARQ feedback information is higher than a fifth threshold, the number of failures of the channel access procedure for transmission of the HARQ feedback information in the operating unlicensed band within the first observation window is higher than a sixth threshold, The type of propagation of the sidelink data transmission is multicast, lack of valid shared channel occupation time (COT) associated with the unlicensed band in said operation, lack of time to acquire a new COT for said transmission of said HARQ feedback information in said operating unlicensed band, The number of retransmissions of the transport block associated with the HARQ feedback information is higher than a seventh threshold, triggering a HARQ retransmission for the sidelink data transmission before the start of a DRX Off period, or The CBR in the auxiliary frequency band is lower than an eighth threshold, or The number of failures of the channel access procedure for transmission of the HARQ feedback information in the secondary frequency band within the second observation window is higher than a ninth threshold.

6. The first device according to claim 1, wherein the first device is further configured to: An indication is sent to the second device that the first device will switch to the auxiliary frequency band for transmitting the HARQ feedback information.

7. The first device of claim 1, wherein the configuration of the first PSFCH resource in the secondary frequency band indicates at least one of the following: The time resource included in the first PSFCH resource, The frequency resources included in the first PSFCH resources, The sequence resources included in the first PSFCH resource, an association between a sidelink data transmission in a subchannel of a sidelink resource pool in said operating unlicensed band and said first PSFCH resource in said secondary band, a frequency offset between the first PSFCH resource and the second PSFCH resource in the operating unlicensed frequency band, or A time offset between the first PSFCH resource and the second PSFCH resource in the operating unlicensed frequency band.

8. The first device of claim 1, wherein the first device is caused to receive the configuration of the first PSFCH resource from a third device serving the first device; or The configuration of the first PSFCH resource is pre-configured in the configuration of the sidelink resource pool.

9. The first device according to claim 1, wherein the first device is further caused to: Rate matching of physical resource blocks of downlink or uplink transmission channels is performed around the first PSFCH resource in the secondary frequency band.

10. A second device, comprising: at least one processor; as well as at least one memory including computer program code; wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the second device to: Obtaining a configuration of a first physical sidelink feedback channel (PSFCH) resource in a secondary frequency band, the first PSFCH resource being used to respond to hybrid automatic repeat request (HARQ) feedback information for a sidelink data transmission from the second device in an operating unlicensed frequency band, the secondary frequency band comprising: a non-congested unlicensed frequency band, or a frequency band in which a channel access procedure is not required; determining whether to receive the HARQ feedback information on the first PSFCH resource in the secondary frequency band; and Based on determining that the HARQ feedback information is to be received on the first PSFCH resource in the secondary frequency band, the HARQ feedback information is received from the first device on the first PSFCH resource.

11. The second device of claim 10, wherein the second device is caused to determine that the HARQ feedback information is to be received on the first PSFCH resource in the secondary frequency band by: detecting the HARQ feedback information in a second PSFCH resource in the operating unlicensed band; and According to determining that the HARQ feedback information does not exist in the operating unlicensed frequency band, determining that the HARQ feedback information is to be received on the first PSFCH resource in the auxiliary frequency band.

12. The second device of claim 10, wherein the second device is caused to determine that the HARQ feedback information is to be received on the first PSFCH resource in the secondary frequency band by: sending, to the first device, an indication that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band; and Based on the indication, it is determined that the HARQ feedback information is to be received on the first PSFCH resource.

13. The second device of claim 10, wherein the second device is caused to determine that the HARQ feedback information is to be received on the first PSFCH resource in the secondary frequency band by determining at least one of the following: A congestion busy rate (CBR) in the unlicensed band in operation is higher than a first threshold, The priority of the sidelink data transmission is higher than a second threshold, The reliability requirement of the HARQ feedback information is higher than a third threshold, The delay requirement of the HARQ feedback information is higher than a fourth threshold, The service quality level of the HARQ feedback information is higher than a fifth threshold, the number of failures of the channel access procedure for transmission of the HARQ feedback information in the operating unlicensed band within the first observation window is higher than a sixth threshold, The type of propagation of the sidelink data transmission is multicast, lack of valid shared channel occupation time (COT) associated with the unlicensed band in said operation, lack of time to acquire a new COT for said transmission of said HARQ feedback information in said operating unlicensed band, The number of retransmissions of the transport block associated with the HARQ feedback information is higher than a seventh threshold, triggering a HARQ retransmission for the sidelink data transmission before the start of a discontinuous reception off period, The CBR in the auxiliary frequency band is lower than an eighth threshold, or The number of failures of the channel access procedure for transmission of the HARQ feedback information in the secondary frequency band within the second observation window is higher than a ninth threshold.

14. The second device of claim 10, wherein the second device is caused to determine that the HARQ feedback information is to be received on the first PSFCH resource in the secondary frequency band by: receiving, from the first device, an indication that the first device will switch to the auxiliary frequency band for transmitting the HARQ feedback information; and Based on the indication, it is determined that the HARQ feedback information is to be received on the first PSFCH resource.

15. The second device according to claim 10, wherein the configuration of the first PSFCH resource indicates at least one of the following items: The time resource included in the first PSFCH resource, The frequency resources included in the first PSFCH resources, The sequence resources included in the first PSFCH resource, an association between a sidelink data transmission in a subchannel of a sidelink resource pool in said operating unlicensed band and said first PSFCH resource in said secondary band, a frequency offset between the first PSFCH resource and the second PSFCH resource in the operating unlicensed frequency band, or A time offset between the first PSFCH resource and the second PSFCH resource in the operating unlicensed frequency band.

16. The second device according to claim 15, wherein the second device is caused to receive the configuration of the first PSFCH resource from a third device serving the first device; or The configuration of the first PSFCH resource is pre-configured in the configuration of the sidelink resource pool.

17. An apparatus comprising: means for acquiring, at the first device, a configuration of a first PSFCH resource in a secondary frequency band, the first PSFCH resource being used to respond to HARQ feedback information of a sidelink data transmission from a second device in an operating unlicensed frequency band, the secondary frequency band comprising: a non-congested unlicensed frequency band, or a frequency band in which a channel access procedure is not required; means for determining whether the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band; and means for sending the HARQ feedback information to the second device on the first PSFCH resource in response to determining that the HARQ feedback information is to be sent on the first PSFCH resource in the secondary frequency band.

18. An apparatus comprising: means for acquiring, at a second device, a configuration of a first physical sidelink feedback channel (PSFCH) resource in a secondary frequency band, the first PSFCH resource being used to respond to hybrid automatic repeat request (HARQ) feedback information for a sidelink data transmission from the second device in an operating unlicensed frequency band, the secondary frequency band comprising: a non-congested unlicensed frequency band, or a frequency band in which a channel access procedure is not required; means for determining whether to receive the HARQ feedback information on the first PSFCH resource in the secondary frequency band; and means for receiving the HARQ feedback information from a first device on the first PSFCH resource in response to determining that the HARQ feedback information is to be received on the first PSFCH resource in the secondary frequency band.

19. A computer-readable medium comprising program instructions for causing an apparatus to perform at least the method according to any one of claims 1 to 9.

20. A computer-readable medium comprising program instructions for causing an apparatus to perform at least the method according to any one of claims 10 to 16.

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