WO2023206308A1

WO2023206308A1 - A method, device, apparautus and computer-readable medium for communications

Info

Publication number: WO2023206308A1
Application number: PCT/CN2022/090101
Authority: WO
Inventors: Naizheng ZHENG; Timo Erkki Lunttila; Jianguo Liu; Yong Liu; Ling Yu; Nuno Manuel KIILERICH PRATAS; Vinh Van Phan; Laura Luque SANCHEZ; Torsten WILDSCHEK
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2022-04-28
Filing date: 2022-04-28
Publication date: 2023-11-02

Abstract

Embodiments of the present disclosure relate to devices, methods, apparatuses and computer-readable storage medium for communication. In some example embodiments, a first device detects, during a first time period, whether a Negative Acknowledgement (NACK) for a time unit is received from a second device on at least one sidelink feedback channel associated with the time unit. The time unit is used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel is indicated in a sidelink feedback channel configuration. In response to detecting that no NACK is received during the first time period, the first device transmits, from a first protocol layer to a second protocol layer, a first indication indicating that the sidelink data transmission in the time unit is successful, the second protocol layer being a higher protocol layer than the first protocol layer.

Description

A METHOD, DEVICE, APPARAUTUS AND COMPUTER-READABLE MEDIUM FOR COMMUNICATIONS

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication, and in particular, to devices, methods, apparatuses and computer-readable storage media for communications.

BACKGROUND

With the development of communication technology, a sidelink communication technology in which terminal devices can communicate with each other directly has been introduced. In the sidelink communication, the transmitting device transmits data information to a reception device in a Physical Sidelink Shared Channel (PSSCH) and transmits control information to the reception device in a Physical Sidelink Control Channel (PSCCH) . In turn, the reception device may transmit a Negative acknowledge (NACK) or Positive acknowledge (ACK) for the data transmitted in the PSSCH to the transmitting device in a Physical Sidelink Feedback Channel (PSFCH) resource, in order to inform the transmitting device whether the data is received successfully. In some situations, the transmitting device and reception device perform the sidelink data transmission on unlicensed sidelink channel, and this may cause the transmission failure of the NACK or ACK feedback. In this case, the redundancy of the feedback transmissions should be further optimized. Further, the trade-off between the redundancy and different communication requirements is also a key aspect.

SUMMARY

In general, example embodiments of the present disclosure provide devices, methods, apparatuses and computer-readable storage media for communications.

In a first aspect, there is provided a first device. The terminal device comprises at least one processor and at least one memory including computer program code. The at least one memory and the computer program code configured to, with the at least one processor, cause the first device to detect, during a first time period, whether a Negative Acknowledgement (NACK) for a time unit is received from a second device on at least one sidelink feedback channel associated with the time unit. The time unit is used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel is indicated in a sidelink feedback channel configuration. In response to detecting that no NACK is received during the first time period, the first device is further caused to transmit, from a first protocol layer to a second protocol layer, a first indication indicating that the sidelink data transmission in the time unit is successful, the second protocol layer being a higher protocol layer than the first protocol layer.

In a second aspect, there is provided a second device. The second device comprises at least one processor and at least one memory including computer program code. The at least one memory and the computer program code configured to, with the at least one processor, cause the second device to perform, during a first time period, a channel occupancy procedure on at least one sidelink feedback channel for transmitting at least one of a Negative Acknowledgement (NACK) for a time unit and a Positive Acknowledgement for the time unit. The time unit is used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel is indicated in a sidelink feedback channel configuration. In response to the channel occupancy procedure being successful, the second device is further caused to transmit, to a first device, the at least one of the NACK and the ACK on the at least one sidelink feedback channel. Alternatively, in response to the channel occupancy procedure being failed during the first time period, the second device is further caused to release a remaining sidelink feedback channel of the at least one sidelink feedback channel. The remaining sidelink feedback channel is a sidelink feedback channel of the at least one sidelink feedback channel other than the sidelink feedback channel on which the channel occupancy procedure is performed.

In a third aspect, there is provided a method implemented in a first device. In the method, the first device detects, during a first time period, whether a Negative Acknowledgement (NACK) for a time unit is received from a second device on at least one sidelink feedback channel associated with the time unit. The time unit is used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel is indicated in a sidelink feedback channel configuration. In response to detecting that no NACK is received during the first time period, the first device transmits, from a first protocol layer to a second protocol layer, a first indication indicating that the sidelink data transmission in the time unit is successful, the second protocol layer being a higher protocol layer than the first protocol layer.

In a fourth aspect, there is provided a method implemented in a second device. In the method, the second device performs, during a first time period, a channel occupancy procedure on at least one sidelink feedback channel for transmitting at least one of a Negative Acknowledgement (NACK) for a time unit and a Positive Acknowledgement for the time unit. The time unit is used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel is indicated in a sidelink feedback channel configuration. In response to the channel occupancy procedure being successful, the second device transmits, to a first device, the at least one of the NACK and the ACK on the at least one sidelink feedback channel. Alternatively, in response to the channel occupancy procedure being failed during the first time period, the second device releases a remaining sidelink feedback channel of the at least one sidelink feedback channel. The remaining sidelink feedback channel is a sidelink feedback channel of the at least one sidelink feedback channel other than the sidelink feedback channel on which the channel occupancy procedure is performed.

In a fifth aspect, there is provided an apparatus implemented in a first device comprising means for performing the method according to the third aspect.

In a sixth aspect, there is provided an apparatus implemented in a second device comprising means for performing the method according to the fourth aspect.

In an seventh aspect, there is provided computer-readable storage medium having instructions stored thereon. The instructions, when executed on at least one processor, cause the least one processor to perform the method to any of the third to fourth aspects.

Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some example embodiments of the present disclosure in the accompanying drawings, the above and other objects, features and advantages of the present disclosure will become more apparent, wherein:

FIG. 1 illustrates an example environment in which example embodiments of the present disclosure can be implemented;

FIG. 2 illustrates a signaling process for sidelink feedback channel configuration according to some example embodiments of the present disclosure;

FIG. 3 illustrates an example sidelink feedback channel configuration according to some example embodiments of the present disclosure;

FIG. 4A and 4B illustrate an example sidelink feedback channel configuration according to some example embodiments of the present disclosure;

FIG. 5 illustrates a flowchart according to some example embodiments of the present disclosure;

FIG. 6 illustrates a flowchart for transmitting device according to some example embodiments of the present disclosure;

FIG. 7 illustrates a flowchart for transmitting device and reception device according to some example embodiments of the present disclosure;

FIG. 8 illustrates a flowchart for transmitting device and reception device according to some example embodiments of the present disclosure;

Fig. 9 illustrates an example method implemented in a first device in accordance with some example embodiments of the present disclosure;

Fig. 10 illustrates an example method implemented in a second device in accordance with some example embodiments of the present disclosure; and

Fig. 11 is a simplified block diagram of a device that is suitable for implementing embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitations as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

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 skills in the art to which this disclosure belongs.

As used herein, the term “terminal device” refers to any device having wireless or wired communication capabilities. Examples of the terminal device include, but not limited to, terminal device, user equipment (UE) , personal computers, desktops, mobile phones, cellular phones, smart phones, personal digital assistants (PDAs) , portable computers, tablets, wearable devices, internet of things (IoT) devices, Internet of Everything (IoE) devices, machine type communication (MTC) devices, device on vehicle for V2X communication where X means pedestrian, vehicle, or infrastructure/network, devices for Integrated Access and Backhaul (IAB) , or image capture devices such as digital cameras, gaming devices, music storage and playback appliances, or Internet appliances enabling wireless or wired Internet access and browsing and the like. Herein, the term “terminal device” can be used interchangeably with a UE.

As used herein, the term “network device” refers to a device which is capable of providing or hosting a cell or coverage where a terminal device, can communicate with. Examples of a network device include, but not limited to, a Node B (NodeB or NB) , an Evolved NodeB (eNodeB or eNB) , a next generation eNB (ng-eNB) , a ng-eNB-Central Unit (ng-eNB-CU) , a ng-eNB-Distributed Unit (ng-eNB-DU) , a next generation NodeB (gNB) , a gNB-Central Unit (gNB-CU) , a gNB-Distributed Unit (gNB-DU) , a Remote Radio Unit (RRU) , a radio head (RH) , a remote radio head (RRH) , an Integrated Access and Backhaul (IAB) node, a low power node such as a femto node, a pico node, and the like. In some communication systems, the network device may be consist of multiple separate entities, for example, in NTN system, the network device may be consist of radio frequency part located in satellites or drones, and inter-frequency/base band part located in ground stations.

The term “circuitry” used herein may refer to hardware circuits and/or combinations of hardware circuits and software. For example, the circuitry may be a combination of analog and/or digital hardware circuits with software/firmware. As a further example, the circuitry may be any portions of hardware processors with software including digital signal processor (s) , software, and memory (ies) that work together to cause an apparatus, such as a terminal device or a network device, to perform various functions. In a still further example, the circuitry may be hardware circuits and or processors, such as a microprocessor or a portion of a microprocessor, that requires software/firmware for operation, but the software may not be present when it is not needed for operation. As used herein, the term circuitry also covers an implementation of merely a hardware circuit or processor (s) or a portion of a hardware circuit or processor (s) and its (or their) accompanying software and/or firmware.

As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term ‘includes’ and its variants are to be read as open terms that mean “includes, but is not limited to” . The term ‘based on’ is to be read as ‘at least in part based on. ’ The term ‘one embodiment’ and ‘an embodiment’ are to be read as ‘at least one embodiment. ’ The term ‘another embodiment’ is to be read as ‘at least one other embodiment. ’ The terms ‘first, ’ ‘second, ’ and the like may refer to different or same objects. The terms “first” , “second” and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below.

As mentioned above, if the transmitting device and reception device perform the sidelink data transmission on unlicensed sidelink channel, the reliability of the transmission of NACK or ACK for data transmitted in PSSCH may be affected. Specifically, in some situations, the reception device only transmits to the transmitting device the NACK for data transmitted in PSSCH, or the reception device only report the data reception failure to the transmitting device rather than reporting the data reception successful. In this case, if the transmitting device receives no NACK, the transmitting device may consider the previous transmitted data as being received successfully. However, if the transmitting device and reception device perform the sidelink data transmission on unlicensed sidelink channel, the reception device should perform a channel occupancy procedure on a unlicensed channel before transmitting the NACK, and the NACK can be transmitted to the transmitting device only if the channel occupancy procedure is successful. In this case, even if the reception device detects reception failure of data transmitted in PSSCH, whether a NACK for the data can be received by the transmitting device further depends on the result of contention by the reception device for the unlicensed channel. At the transmitting device, if the NACK for the data is not received, the previous transmission is considered by the transmitting device as being successful. However, the data transmission may fail, and NACK cannot be transmitted successfully as the channel occupancy procedure is also failed.

One solution is that configuring a plurality of PSFCH resources for transmitting the feedback for the data transmitted in PSSCH. In addition, after the plurality of PSFCH resources has been configured, the adaption of the plurality of PSFCH resources and different communication requirements can be further optimized.

Example embodiments of the present disclosure provide a scheme for sidelink feedback channel configuration. In this scheme, a first device detects, during a first time period, whether a Negative Acknowledgement (NACK) for a time unit is received from a second device on at least one sidelink feedback channel associated with the time unit. The time unit is used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel is indicated in a sidelink feedback channel configuration. In response to detecting that no NACK is received during the first time period, the first device transmits, from a first protocol layer to a second protocol layer, a first indication indicating that the sidelink data transmission in the time unit is successful. The second protocol layer is a higher protocol layer than the first protocol layer.

In this way, the first device is able to receive the NACK for previous transmitted data on at least one sidelink feedback channel. Therefore, the reception device has more opportunities for transmitting feedback for the data such that the reliability of feedback transmission is increased. Further, with restriction of the first time period, the configured at least one sidelink feedback channel can be adapted to different communication requirements.

FIG. 1 illustrates an example environment 100 in which example embodiments of the present disclosure can be implemented.

The environment 100, which may be a part of a data communication network, comprises a first device 110, a second device 120 and a third device 130. In the environment 100, the first device 110 and the second device may communicate with each other directly based on a sidelink transmission channel. In addition, the first device 110 and the second device 120 may also communication with each other via the third device 130. Moreover, the first device 110 may communicate with the third device 130 and the second device 120 may communicate with the third device 130. Without any limitation, the first device 110 and the second device 120 may comprise a terminal device, and the third device 130 may comprise a network device.

It is to be understood that the number of the first device 110, the second device 120 and the third device 130 is shown in the environment 100 only for the purpose of illustration, without suggesting any limitation to the scope of the present disclosure. In some example embodiments, the environment 100 may comprise a further first device, a further second device and/or a further third device.

The first device 110 can communicate with the second device 120 or with a further device (not shown) directly or via the third device 130. The first device 110 can communicate with the second device 120 or the third device 130 by wired (for example, optical fiber communication) or wireless communication technologies. The communications in the environment 100 may follow any suitable communication standards or protocols, which are already in existence or to be developed in the future, such as Universal Mobile Telecommunications System (UMTS) , long term evolution (LTE) , LTE-Advanced (LTE-A) , the fifth generation (5G) New Radio (NR) , Wireless Fidelity (Wi-Fi) and Worldwide Interoperability for Microwave Access (WiMAX) standards, and employs any suitable communication technologies, including, for example, Multiple-Input Multiple-Output (MIMO) , Orthogonal Frequency Division Multiplexing (OFDM) , time division multiplexing (TDM) , frequency division multiplexing (FDM) , code division multiplexing (CDM) , Bluetooth, ZigBee, and machine type communication (MTC) , enhanced mobile broadband (eMBB) , massive machine type communication (mMTC) , ultra-reliable low latency communication (URLLC) , Carrier Aggregation (CA) , Dual Connection (DC) , and New Radio Unlicensed (NR-U) technologies.

FIG. 2 illustrates a signaling process 200 for sidelink feedback channel configuration according to some example embodiments of the present disclosure. For purpose of discussion, the signaling process 200 will be described with reference to FIG. 1.

In the signaling process 200, at step 210, the first device 110 detects, during a first time period, whether a Negative Acknowledgement (NACK) for a time unit is received from the second device 120 on at least one sidelink feedback channel associated with the time unit. This time unit is a previous transmitted time unit which is configured for a sidelink data transmission from the first device to the second device. In some embodiments, the time unit may comprise a slot. In addition or alternatively, the time unit may also comprise at least one of a symbol, a subframe and a frame. In some other embodiments, the time unit may be any other length in time domain. In some embodiments, the first time period may be the maximum delay for transmitting the NACK or ACK for the previous data transmission from the physical layer to a higher layer, for example, Medium Access Control (MAC) layer.

The at least one sidelink feedback channel associated with the time unit is indicated in a sidelink feedback channel configuration. In some embodiments, the sidelink feedback channel configuration may indicate a plurality of sidelink feedback channels associated with the time unit. The plurality of sidelink feedback channels may comprise one primary sidelink feedback channel and at least one secondary sidelink feedback channel. With the one primary sidelink feedback channel and the at least one secondary sidelink feedback channel, the second device 120 may transmit the NACK or ACK for the time unit which is configured for the sidelink data transmission from the first device to the second device. In some embodiments, the indicated plurality of sidelink feedback channel may comprise unlicensed sidelink channel. In this case, if a channel occupancy procedure performed on the one primary sidelink feedback channel by the second device 120 is failed, the second device 120 may perform a further channel occupancy procedure on a secondary sidelink feedback channel of the secondary sidelink feedback channel in order to transmit the NACK or the ACK, until a successful channel occupancy procedure or the first time period is expired. As such, the reliability of the transmission of NACK or ACK is increased accordingly.

In this disclosure, the channel occupancy procedure may comprise any channel sensing procedure for estimating whether a channel is occupied. For example, the channel occupancy procedure may comprise a Listen Before Talk (LBT) procedure, a Clear Channel Assessment (CCA) procedure, a channel access procedure. In another example, the channel occupancy procedure may comprise any other similar procedure in the future.

In some embodiments, the sidelink feedback channel configuration may indicate the association between the plurality of sidelink feedback channels and more than one time units for the sidelink data transmission from the first device 110 to the second device 120. In this case, the NACK and ACK for each of the more than one time units can be transmitted in the plurality of sidelink feedback channels as discussed above.

With respect to the sidelink feedback channel configuration, it may be predefined in some embodiments. In addition or alternatively, the sidelink feedback channel configuration may be determined by the transmitting device (for example, the first device 110) and is transmitted (211) to the reception device (for example, the second device 120) . In addition or alternatively, the sidelink feedback channel configuration may be determined by the reception device (for example, the second device 120) and is transmitted (213) to the transmitting device (for example, the first device 110) . In addition or alternatively, the sidelink feedback channel configuration may be determined by another device (for example, the third device 130) and is transmitted (215) to the transmitting device (for example, the first device 110) and the reception device (for example, the second device 120) , respectively.

For discussing clarity, the sidelink feedback channel configuration is further discussed with reference to FIG. 3.

FIG. 3 illustrates an example sidelink feedback channel configuration according to some example embodiments of the present disclosure.

In some embodiments, the sidelink feedback channel configuration may indicate one primary sidelink feedback channel 310 and a number of the at least one secondary sidelink feedback channel. As shown in FIG. 3, the number of the at least one secondary sidelink feedback channel is two. As shown, these two secondary sidelink feedback channels comprise the secondary

sidelink feedback channels

320 and 330. In some embodiments, the sidelink feedback channel configuration further indicates a first offset between the one primary sidelink feedback 310 and the secondary sidelink feedback channel 320, and a second offset between the secondary sidelink feedback channel 320 and the sidelink feedback channel 330. It is to be understood that the first offset may be equal to the second offset or the first offset may be different from the second offset. In addition or alternatively, there may be more than two secondary sidelink feedback channels. In this case, offset between neighboring secondary sidelink feedback channels may be equal to the second offset or may be indicated individually.

With the above offsets and the number of sidelink feed channels, the sidelink feedback channel configuration may indicate association between the time unit and the primary sidelink feedback channel 310 and

sidelink feedback channels

320 and 330 with two parameters, K and N. In an example, the time occasion for the primary sidelink feedback channel is determined based on K. For a time unit 380 for sidelink data transmission (which may be also referred as a PSSCH transmission) with its last symbol in slot n, the time occasion for the primary sidelink feedback channel 310 is in slot n+a, where a is the smallest integer larger than or equal to K with the condition that slot n+a contains PSFCH resources. The time gap of at least K slots allows considering the reception device (for example, the second device 120) processing delay in decoding the PSCCH and generating the HARQ or ACK feedback. In the example in FIG. 3, K is equal to 3, and a single value of K can be (pre-) configured per resource pool. This allows several reception devices to use the same resource pool to utilize the same mapping of sidelink feedback channel resource (s) for the HARQ feedback. With the parameter K and N, associated PSSCH time units can be determined. As the example illustrated in FIG. 3, with K is configured as 3, and the period of primary PSFCH resources is configured as N=4, then there will be 4

PSSCH slots

350, 360, 370 and 380 that are associated with the primary sidelink feedback channel 310. In this way, with the number of secondary sidelink feedback channels and the first and second offsets, the association between the

time units

350, 360, 370, 380 and the plurality of sidelink feedback channel (or the association between the location of the time unit and the location of the sidelink feedback channel) is established.

In some embodiments, the first time period is preconfigured as the time length from the primary sidelink feedback channel 310 to the last one 330 of the secondary sidelink feedback channel. In this case, the first device 110 may detect the NACK or ACK for the

time units

350, 360, 370 and 380 on all the

sidelink feedback channels

310, 320 and 330. If detecting no NACK after the sidelink feedback channels 330, the first device 110 may transmit an indication indicating the PSSCH within the

time units

350, 360, 370 and 380 is successful. In turn, if the second device 120 detects a reception failure of any of the

time units

350, 360, 370 and 380, the second device 120 may perform a channel occupancy procedure on the

sidelink feedback channels

310, 320 and 330 sequentially in order to transmit the NACK for the corresponding time unit. In addition or alternatively, the first time period may be also preconfigured as any other time length on demand.

In an example, the first device 110 detects the NACK or ACK for the

time units

350, 360, 370 and 380 only on valid sidelink feedback channels. The sidelink feedback channels within the first time period is determined as the valid sidelink feedback channels. In the example of FIG. 3, all the

sidelink feedback channels

310, 320 and 330 are determined as the valid sidelink feedback channels.

In turn, the second device 110 performs a channel occupancy procedure on the valid sidelink feedback channels, and the sidelink feedback channels within the first time period is determined as the vaild sidelink feedback channels.

In some embodiments, the first time period is not equal to the time length from the primary sidelink feedback channel 310 to the last one 330 of the secondary sidelink feedback channel. For example, the first time period may be adjusted according different communication conditions. In this case, not each of the sidelink feedback channels is valid. This is discussed in detail in the following. In addition or alternatively, the first time period is predefined between the first and

second devices

110 and 120.

Returning back to FIG. 2, in some embodiments, certain types of communication may require low latency or have higher priority, the first time period for the first device 110 detecting NACK or ACK (or the first time period for the second device 120 to perform the channel occupancy procedure in order to send NACK or ACK) can be adjusted dynamically. In addition or alternatively, the first device 110 and second device 120 may adjust the first time period based on channel conditions. In addition or alternatively, the first device 110 and second device 120 may adjust the first time period based on statistic result of the historical delay between the time unit and the time occasion of receiving/transmuting the NACK or ACK.

For example, in some embodiments, the first terminal device 110 may adjust the first time period based on the activity level of the sidelink transmission channel. In an example, the first device 110 may measure power or energy information associated with the channel which can be used for transmitting NACK or ACK. In some embodiments, the measured parameter may comprise Received Signal Strength Indicator (RSSI) and Reference Signal Receiving Power (RSRP) associated with the above channels. In addition or alternatively, the measured parameter may comprise any other parameters reflecting the busy ratio of the above channels.

If the measured power or energy is below a busy ratio threshold predefined for the sidelink transmission channel, the first device may realize that the channel occupancy procedure on this channel for the sidelink transmission should have a high success rate. Therefore, if the first device 110 detects no NACK on this channel, the first device 110 may determine that the second device 120 performed no channel occupancy procedure. Further, the first device 110 may determine that the transmitted sidelink data on previous time units have been received by the second device 120 successfully. Then, the first device 110 may transmit ACK for the previous data transmission from the physical layer to a higher layer, for example, MAC CE layer.

In this case, the first device 110 is not required to detect other sidelink feedback channels, for example, the

secondary feedback channels

320 and 330 as shown in FIG. 3. For example, the first device 110 may adjust (220) the first time period such that the first time period is terminated immediately after the primary sidelink feedback channel. As discussed above, the

secondary feedback channels

320 and 330 become invalid in this case. In addition, the first device 110 may reuse the communication resources for the

secondary feedback channels

320 and 330 to perform other transmissions.

For discussing clarity, the adjustment on the first time period is further discussed with reference to FIG. 4A and 4B.

FIG. 4A and 4B illustrate an example sidelink feedback channel configuration according to some example embodiments of the present disclosure.

In addition or alternatively to adjusting by the first device 110 the first time period based on the activity level of a channel, the first time period may be also adjusted (

steps

220 and 230 as shown in FIG. 2) by the first and second devices base on other conditions.

In sidelink communication, a device may initiate a Channel Occupancy Time (COT) for a channel. Further, after the COT has been initiated, the device may share the COT to another device. In this case, the other device may occupy this channel associated with COT quickly within the COT. For example, the other device may occupy this channel without performing complete LBT or CCA procedure. In an example, the other device may only perform Type 2A, Type 2B or Type 2C channel occupancy procedure, which is quite shorter than the above complete channel occupancy procedure, to obtain the occupancy of the channel.

For the sidelink transmission feedback, the first device 110 may share the COT to the second device 120 after performing the sidelink data transmission, such that the second device 120 is ensured to occupy this channel for transmitting the NACK and ACK.

In this way, from the first device 110 perspective, since the second device 120 is ensured to occupy a channel for transmitting the NACK, if the indicated primary sidelink feedback channel 410 as shown in FIG. 4A is within the COT that was initiated and shared to the second device 120 by the first device 110 and no NACK has been detected by the first device 110, the first device 110 may perform immediate ACK reporting from physical layer to higher-layer after the primary feedback channel 410. Specifically, the first time period is adjusted such that it is terminated immediately after the primary sidelink feedback channel 410. In turn, the other sidelink feedback channels become invalid accordingly.

In addition, the first device 110 may reuse communication resources associated with other indicated sidelink feedback channels to perform other transmissions. In addition or alternatively, if the indicated sidelink feedback channel are outside of the COT, the first device 110 may not adjust/shorten the first time period and detect the ACK and NACK on all the valid

sidelink feedback channels

410, 420 and 430.

From the second device 120 perspective, if the second device 120 is shared with a COT for a channel and the primary sidelink feedback channel 410 is located in the COT, the second device 120 may transmit the ACK or NACK for the previous time units associated PSSCH on the primary sidelink feedback channel 410 directly. The first time period is adjusted such that it is terminated immediately after the primary sidelink channel feedback 410 respectively. Accordingly, the remaining indicated sidelink feedback channels, for example, the secondary

sidelink feedback channels

420 and 430 become valid and are released at the second device 120 side. The second device 120 may reuse the communication resources associated with the remaining indicated sidelink feedback channels to receive further sidelink data transmission.

However, in some embodiments, even if the second device 120 is shared with the COT, the type 2A, type 2B or type 2C may be also failed. In this case, the first time period is also adjusted such that it is terminated immediately after the primary sidelink channel feedback 410, since the first device 110 has reported the ACK to the higher layer. In addition, the second device 120 still releases the secondary

sidelink feedback channels

420 and 430.

In addition or alternatively, any sidelink feedback channels (for example, the secondary sidelink feedback channel) within the COT may be determined as valid sidelink feedback channel. In this case, the first time period is adjusted to be terminated when the COT is expired. In addition or alternatively, the COT is shared from another device to the second device 120. In this case, the first device 110 and second device 120 may adjust the first time period in the same way as the COT is initiated by the first device 110, except that the first device 110 may need to obtain the time information for the COT.

In addition to activity level or the COT or alternatively, the first time period may be also adjusted based on communication requirements.

In some embodiments, certain PSSCHs may be configured with a Packet Delay Budget (PDB) . In this case, the first time period is adjusted to fulfill the PDB for the previous transmitted PSSCH. For example, the first time period is adjusted based on the maximum latency allowed for the PDB. For example, if the PDB is smaller than a first duration threshold, the first time period may be decreased to fulfill the PDB requirement. As shown in FIG. 4B, if a time occasion of maximum latency allowed for the PDB is between the secondary sidelink feedback channel 450 and the secondary sidelink feedback channel 460. The first time period is adjusted such that it is terminated immediately after the secondary sidelink feedback channel 450.

In this case, from the first device 110 perspective, the first device 110 only determines the primary sidelink feedback channel 440 and the secondary sidelink feedback channel 450 as the valid feedback channels, and detects the NACK or ACK or these valid feedback channels. If detecting no NACK, the first device 110 may report the successful transmission from the physical layer to a higher layer. Similarly, the secondary feedback channel 460 may be reused. Further, the first device 110 may inform the second device 120 the PDB information.

From the second device 120 perspective, the first time period is also adjusted based on the PDB accordingly. The second device 120 only performs the channel occupancy procedure on the primary sidelink feedback channel 440 and the secondary sidelink feedback channel 450 for transmitting the NACK or ACK. The communication resources associated with the secondary sidelink feedback channel 460 will be released for reusing, regardless the result of the above channel occupancy procedures.

In addition or alternatively, the first time period may be adjusted based on the traffic priority of the previous transmitted PSSCH. If the previous transmitted PSSCH has a quite high priority, the first time period may be decreased or increased. In an example, there may be a predefined threshold priority level. If the traffic priority of the PSSCH is higher than the predefined threshold priority level, the first time period may be decreased or increased. Further, the first network device 110 may inform the second device 120 with the traffic priority information. Then, the first time period may be adjusted at the first network device 110 and the second device 120 based on predetermined criterion. After adjusting the first time period, the first device 110 and second device 120 may detect NACK, perform the channel occupancy procedure or reuse the communication resources in the same way as above.

In addition or alternatively, the first time period may be adjusted based on a statistic result of a historical delay between the time unit and a time occasion of receiving the NACK. For example, if the statistic result of a historical delay is smaller than the first time period, the first time period may be adjusted to equal to the statistic result. In addition, if the statistic result of a historical delay is larger than the first time period, the first time period may be adjusted to equal to the statistic result. After adjusting the first time period, the first device 110 and second device 120 may detect NACK, perform the channel occupancy procedure or reuse the communication resources in the same way as above.

In some embodiments, the first device 110 may adjust the first time period in the above methods as discussed with reference to FIGs. 2-4B and transmit the first time period to the second device 120. For example, the first device 110 may transmit the adjusted first time period in a Sidelink Control Information (SCI) . With the adjusted first time period, the first device 110 and second device 120 may detect NACK, perform the channel occupancy procedure or reuse the communication resources in the same way as above. In some embodiments, the SCI may comprise a second indication indicating that a portion of the at least one secondary sidelink feedback channel is disabled. In this case, the first and

second network devices

110 and 120 may reuse the portion of the at least one secondary sidelink feedback channel for transmitting the sidelink data transmission.

FIGs. 5-8 illustrate example flowcharts employed by devices in sidelink communication.

FIG. 5 illustrates a flowchart according to some example embodiments of the present disclosure.

At block 510, the

first device

110 and 120 are configured with sidelink feedback configuration for unlicensed sidelink channel.

At block 520, the

first device

110 and 120 determine whether to perform the sidelink data transmission on the unlicensed sidelink channels.

If the sidelink data transmission is performed on the unlicensed sidelink channels, the first device 110 may detect NACK or ACK on one or more indicated sidelink feedback channels during the first time period at block 530.

At block 540, if there is no NACK received, the first device 110 reports the data has been transmitted successfully to a higher layer.

FIG. 6 illustrates a flowchart according to some example embodiments of the present disclosure.

At block 610, the first device 110 and second device 120 are configured with sidelink feedback configuration for unlicensed sidelink channel.

At block 620, the first device 110 determines whether the channel busy ratio (activity level of the channel) is smaller than a busy ratio threshold.

If the channel busy ratio is smaller than a busy ratio threshold, at the block 620, the first device 110 adjusts the first time period. Moreover, at block 640, the first device 110 detects the NACK or ACK within the adjusted first time period.

If the channel busy is higher than a busy ratio threshold, at block 650, the first device 110 still detects the NACK or ACK during the first time period.

FIG. 7 illustrates a flowchart for transmitting device and reception device according to some example embodiments of the present disclosure.

At block 710, the first device 110 and second device 120 are configured with sidelink feedback configuration for unlicensed sidelink channel.

At block 720, the first device 110 determines whether a primary sidelink feedback channel is located in a COT shared to the second device 120, and/or whether the PDB for the PSSCH is smaller than a first duration threshold, and/or whether the traffic priority of the PSSCH is higher than a threshold priority level. The second device 110 also determines the above items.

If the any of above items are determined as positive, at block 730, the first and

second devices

110 and 120 may adjust the first time period in the same way as discussed with reference FIGs. 4A and 4B. Then, at block 740, the first device 110 detects the NACK or ACK within the adjusted first time period. The second device 120 performs the channel occupancy procedure within the adjusted first time period for transmitting the NACK. Moreover, the first and

second devices

110 and 120 may reuse the communication resources associated with the indicated sidelink feedback channel outside the adjusted first time period.

If the above items are all determined as negative, at block 740, the first and

second device

110 and 120 perform respective operations within the first time period.

FIG. 8 illustrates a flowchart for transmitting device and reception device according to some example embodiments of the present disclosure.

At block 810, the first device 110 may transmit an indication indicating a sidelink feedback configuration to the second device. This configuration may further indicate the first time period.

At block 820, the second device 820 may determines the sidelink feedback channels based on the received indication.

FIG. 9 illustrates an example method 900 implemented in a device in accordance with some example embodiments of the present disclosure.

The method of 900 can be implemented at the first device 110 shown in FIG. 1. For the purpose of discussion, the method 900 will be described with reference to FIG. 1. It is to be understood that the method 900 may include additional acts not shown and/or may omit some shown acts, and the scope of the present disclosure is not limited in this regard.

At 910, the first device detects, during a first time period, whether a Negative Acknowledgement (NACK) for a time unit is received from a second device on at least one sidelink feedback channel associated with the time unit. The time unit is used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel is indicated in a sidelink feedback channel configuration.

At block 920, in response to detecting that no NACK is received during the first time period, the first device transmits, from a first protocol layer to a second protocol layer, a first indication indicating that the sidelink data transmission in the time unit is successful, the second protocol layer being a higher protocol layer than the first protocol layer.

In some embodiments, the at least one sidelink feedback channel comprises: a primary sidelink feedback channel; or a primary sidelink feedback channel and at least one secondary sidelink feedback channel.

In some embodiments, detecting whether the NACK for the time unit is received by: detecting whether a Negative Acknowledgement (NACK) for the time unit is received from a second device on each valid sidelink feedback channel in the at least one sidelink feedback channel, wherein a sidelink feedback channel of the at least one sidelink feedback channel within the first time period is determined as the valid sidelink feedback channel.

In some embodiments, further comprise transmitting, to the second device, a second indication indicating that a portion of the at least one secondary sidelink feedback channel is disabled; and reusing the portion of the at least one secondary sidelink feedback channel for transmitting the sidelink data transmission.

In some embodiments, the sidelink feedback channel configuration indicates at least one of: a number of the at least one secondary sidelink feedback channel; a first offset between the primary sidelink feedback channel and a secondary sidelink feedback channel of the at least one secondary sidelink feedback channel; a second offset between secondary sidelink feedback channels of the at least one secondary sidelink feedback channel; and at least one time unit associated with the at least one sidelink feedback channel.

In some embodiments, further comprising adjusting the first time period based on at least one of: a channel activity level of an unlicensed sidelink channel associated with the sidelink data transmission; a Channel Occupancy Time (COT) for the unlicensed sidelink channel being shared to the second terminal device; a Packet Delay Budget (PDB) for the sidelink data transmission; a traffic priority for the sidelink data transmission; and a statistic result of a historical delay between the time unit and a time occasion of receiving the NACK.

In some embodiments, adjusting the first time period comprises: determining whether the primary sidelink feedback channel is located within the COT; and in accordance with a determination that the primary sidelink feedback channel is located within the COT, adjusting the first time period such that the first time period is terminated after the primary sidelink feedback channel and before a secondary sidelink feedback channel of the at least one secondary sidelink feedback channel.

In some embodiments, adjusting the first time period comprises: determining whether the PDB for the sidelink data transmission is smaller than a first duration threshold; and in accordance with a determination that the PDB is smaller than the first duration threshold, adjusting the first time period such that the first time period is terminated after the primary sidelink feedback channel and before a secondary sidelink feedback channel of the at least one secondary sidelink feedback channel.

In some embodiments, adjusting the first time period comprises: determining whether the traffic priority for the sidelink data transmission is higher than a threshold priority level; and in accordance with a determination that the traffic priority is higher than the threshold priority level, adjusting the first time period such that the first time period is terminated after the primary sidelink feedback channel and before a secondary sidelink feedback channel of the at least one secondary sidelink feedback channel.

In some embodiments, the adjusted first time period is transmitted to the second terminal device.

In some embodiments, the method further comprises: transmitting, to the second device, at least one of the PDB, the traffic priority and the statistic result.

In some embodiments, the method further comprises: transmit the sidelink feedback channel configuration to the second device, wherein the sidelink feedback channel configuration is determined by the first device or is received from a third device.

In some embodiments, the method further comprises: receive the sidelink feedback channel configuration from the second device; or receive the sidelink feedback channel configuration from a third device.

In some embodiments, the first device comprises a terminal device, wherein the second device comprises a terminal device and wherein the third device comprises a network device.

In some embodiments, the first time period is preconfigured.

In some embodiments, the time unit comprises at least one of a slot, a symbol, a subframe and a frame.

In some embodiments, the first protocol layer comprises a physical layer and wherein the second protocol layer comprises a Medium Access Control (MAC) layer.

In some embodiments, the sidelink feedback channel configuration is configured for an unlicensed sidelink data transmission.

FIG. 10 illustrates an example method 1000 implemented in a device in accordance with some example embodiments of the present disclosure.

The method 1000 can be implemented at the second device 120 shown in FIG. 1. For the purpose of discussion, the method 1000 will be described with reference to FIG. 1. It is to be understood that the method 1000 may include additional acts not shown and/or may omit some shown acts, and the scope of the present disclosure is not limited in this regard.

At 1010, the second device performs, during a first time period, a channel occupancy procedure on at least one sidelink feedback channel for transmitting at least one of a Negative Acknowledgement (NACK) for a time unit and a Positive Acknowledgement for the time unit. The time unit is used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel is indicated in a sidelink feedback channel configuration.

At block 1020, in response to the channel occupancy procedure being successful, the second device transmits, to a first device, the at least one of the NACK and the ACK on the at least one sidelink feedback channel.

At block 1030, in response to the channel occupancy procedure being failed during the first time period, the second device releases a remaining sidelink feedback channel of the at least one sidelink feedback channel. The remaining sidelink feedback channel is a sidelink feedback channel of the at least one sidelink feedback channel other than the sidelink feedback channel on which the channel occupancy procedure is performed.

In some embodiments, performing the channel occupancy procedure comprises: performing a channel occupancy procedure on a valid sidelink feedback channel in the at least one sidelink feedback channel, wherein a sidelink feedback channel of the at least one sidelink feedback channel within the first time period is determined as the valid sidelink feedback channel.

In some embodiments, the method further comprises: receiving, from the first device, a second indication indicating that a portion of the at least one secondary sidelink feedback channel is disabled and reusing the portion of the at least one secondary sidelink feedback channel for receiving the sidelink data transmission.

In some embodiments, the method further comprises: receiving, from the first device, at least one of a Packet Delay Budget (PDB) for the sidelink data transmission and a traffic priority for the sidelink data transmission.

In some embodiments, further comprising adjusting the first time period based on at least one of: a Channel Occupancy Time (COT) for the unlicensed sidelink channel being shared to the second terminal device; a Packet Delay Budget (PDB) for the sidelink data transmission; a traffic priority for the sidelink data transmission; and a statistic result of a historical delay between the time unit and a time occasion of receiving the NACK.

In some embodiments, the method further comprises: transmitting the sidelink feedback channel configuration to the first device, wherein the sidelink feedback channel configuration is determined by the second device or is received from a third device.

In some embodiments, the method further comprises: receiving the sidelink feedback channel configuration from the first device; or receiving the sidelink feedback channel configuration from a third device.

In some embodiments, the first time period is received from the first terminal device.

In some embodiments, the first time period is preconfigured.

FIG. 11 is a simplified block diagram of a device 1100 that is suitable for implementing example embodiments of the present disclosure. The device 1100 can be implemented at the terminal device 1110, the network device 1120 as shown in FIG. 1.

As shown, the device 1100 includes a processor 1110, a memory 1120 coupled to the processor 1110, a communication module 1130 coupled to the processor 1110, and a communication interface (not shown) coupled to the communication module 1130. The memory 1120 stores at least a program 1140. The communication module 1130 is for bidirectional communications, for example, via multiple antennas or via a cable. The communication interface may represent any interface that is necessary for communication.

The program 1140 is assumed to include program instructions that, when executed by the associated processor 1110, enable the device 1100 to operate in accordance with the example embodiments of the present disclosure, as discussed herein with reference to FIGS. 2 to 3. The example embodiments herein may be implemented by computer software executable by the processor 1110 of the device 1100, or by hardware, or by a combination of software and hardware. The processor 1110 may be configured to implement various example embodiments of the present disclosure.

The memory 1120 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 1120 is shown in the device 1100, there may be several physically distinct memory modules in the device 1100. The processor 1110 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 1100 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

When the device 1100 acts as the first device 110, the processor 410 may implement the operations or acts of the first device 110 as described above with reference to FIG. 9. When the device 1100 acts as the second device 120, the processor 10 may implement the operations or acts of the second device 120 as described above with reference to FIG. 10. All operations and features as described above with reference to FIGS. 1 to 8 are likewise applicable to the device 1100 and have similar effects. For the purpose of simplification, the details will be omitted.

Generally, various example embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of example embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

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 those included in program modules, being executed in a device on a target real or virtual processor, to carry out the operations and acts as described above with reference to FIGS. 1 to 10. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various example embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable media.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , Digital Versatile Disc (DVD) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular example embodiments. Certain features that are described in the context of separate example embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple example embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present 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.

Various example embodiments of the techniques have been described. In addition to or as an alternative to the above, the following examples are described. The features described in any of the following examples may be utilized with any of the other examples described herein.

In some aspects, an apparatus implemented in a first device comprises: means for detecting during a first time period, whether a Negative Acknowledgement (NACK) for a time unit is received from a second device on at least one sidelink feedback channel associated with the time unit, the time unit being used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel being indicated in a sidelink feedback channel configuration; and means for in response to detecting that no NACK is received during the first time period, transmitting, from a first protocol layer to a second protocol layer, a first indication indicating that the sidelink data transmission in the time unit is successful, the second protocol layer being a higher protocol layer than the first protocol layer.

In some embodiments the apparatus further comprises means for any step of method 900.

In some aspects, an apparatus implemented in a second device comprises: means for performing, during a first time period, a channel occupancy procedure on at least one sidelink feedback channel for transmitting at least one of a Negative Acknowledgement (NACK) for a time unit and a positive Acknowledgement for the time unit, the time unit being used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel being indicated in a sidelink feedback channel configuration; and means for in response to the channel occupancy procedure being successful, transmitting, to a first device, the at least one of the NACK and the ACK on the at least one sidelink feedback channel; or means for in response to the channel occupancy procedure being failed during the first time unit, releasing a remaining sidelink feedback channel of the at least one sidelink feedback channel, the remaining sidelink feedback channel being a sidelink feedback channel of the at least one sidelink feedback channel other than the sidelink feedback channel on which the channel occupancy procedure is performed.

In some embodiments the apparatus further comprises means for any step of method 1000.

In some aspects, a computer-readable storage medium having instructions stored thereon, the instructions, when executed on at least one processor, cause the least one processor to perform the steps of the preceding aspects.

Claims

A first device, comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the first device at least to:

detect, during a first time period, whether a Negative Acknowledgement (NACK) for a time unit is received from a second device on at least one sidelink feedback channel associated with the time unit, the time unit being used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel being indicated in a sidelink feedback channel configuration; and

in response to detecting that no NACK is received during the first time period, transmit, from a first protocol layer to a second protocol layer, a first indication indicating that the sidelink data transmission in the time unit is successful, the second protocol layer being a higher protocol layer than the first protocol layer.
The first device of claim 1, wherein the at least one sidelink feedback channel comprises:

a primary sidelink feedback channel; or

a primary sidelink feedback channel and at least one secondary sidelink feedback channel.
The first device of claim 2, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to detect whether the NACK for the time unit is received by:

detecting whether a Negative Acknowledgement (NACK) for the time unit is received from a second device on each valid sidelink feedback channel in the at least one sidelink feedback channel, wherein a sidelink feedback channel of the at least one sidelink feedback channel within the first time period is determined as the valid sidelink feedback channel.
The first device of claim 2, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to:

transmit, to the second device, a second indication indicating that a portion of the at least one secondary sidelink feedback channel is disabled; and

reuse the portion of the at least one secondary sidelink feedback channel for transmitting the sidelink data transmission.
The first device of claim 2, wherein the sidelink feedback channel configuration indicates at least one of:

a number of the at least one secondary sidelink feedback channel;

a first offset between the primary sidelink feedback channel and a secondary sidelink feedback channel of the at least one secondary sidelink feedback channel;

a second offset between secondary sidelink feedback channels of the at least one secondary sidelink feedback channel; and

at least one time unit associated with the at least one sidelink feedback channel.
The first device of claim 2, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to adjust the first time period based on at least one of:

a channel activity level of an unlicensed sidelink channel associated with the sidelink data transmission;

a Channel Occupancy Time (COT) for the unlicensed sidelink channel being shared to the second terminal device;

a Packet Delay Budget (PDB) for the sidelink data transmission;

a traffic priority for the sidelink data transmission; and

a statistic result of a historical delay between the time unit and a time occasion of receiving the NACK.
The first device of claim 6, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to adjust the first time period by:

determining whether the primary sidelink feedback channel is located within the COT; and

in accordance with a determination that the primary sidelink feedback channel is located within the COT, adjusting the first time period such that the first time period is terminated after the primary sidelink feedback channel and before a secondary sidelink feedback channel of the at least one secondary sidelink feedback channel.
The first device of claim 6, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to adjust the first time period by:

determining whether the PDB for the sidelink data transmission is smaller than a first duration threshold; and

in accordance with a determination that the PDB is smaller than the first duration threshold, adjusting the first time period such that the first time period is terminated after the primary sidelink feedback channel and before a secondary sidelink feedback channel of the at least one secondary sidelink feedback channel.
The first device of claim 6, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to adjust the first time period by:

determining whether the traffic priority for the sidelink data transmission is higher than a threshold priority level; and

in accordance with a determination that the traffic priority is higher than the threshold priority level, adjusting the first time period such that the first time period is terminated after the primary sidelink feedback channel and before a secondary sidelink feedback channel of the at least one secondary sidelink feedback channel.
The first device of claim 6, wherein the adjusted first time period is transmitted to the second terminal device.
The first device of claim 6, where in the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to:

transmit, to the second device, at least one of the PDB, the traffic priority and the statistic result.
The first device of claim 1, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to:

transmit the sidelink feedback channel configuration to the second device, wherein the sidelink feedback channel configuration is determined by the first device or is received from a third device.
The first device of claim 1, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to:

receive the sidelink feedback channel configuration from the second device; or

receive the sidelink feedback channel configuration from a third device.
The first device of claim 12 or 13, wherein the first device comprises a terminal device, wherein the second device comprises a terminal device and wherein the third device comprises a network device.
The first device of claim 1, wherein the first time period is preconfigured.
The first device of claim 1, wherein the time unit comprises at least one of a slot, a symbol, a subframe and a frame.
The first device of claim 1, wherein the first protocol layer comprises a physical layer and wherein the second protocol layer comprises a Medium Access Control (MAC) layer.
The first device of claim 1, wherein the sidelink feedback channel configuration is configured for an unlicensed sidelink data transmission.
A second device, comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the terminal device at least to:

perform, during a first time period, a channel occupancy procedure on at least one sidelink feedback channel for transmitting at least one of a Negative Acknowledgement (NACK) for a time unit and a Positive Acknowledgement for the time unit, the time unit being used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel being indicated in a sidelink feedback channel configuration; and

in response to the channel occupancy procedure being successful, transmit, to a first device, the at least one of the NACK and the ACK on the at least one sidelink feedback channel; or

in response to the channel occupancy procedure being failed during the first time period, release a remaining sidelink feedback channel of the at least one sidelink feedback channel, the remaining sidelink feedback channel being a sidelink feedback channel of the at least one sidelink feedback channel other than the sidelink feedback channel on which the channel occupancy procedure is performed.
The second device of claim 19, wherein the at least one sidelink feedback channel comprises:

a primary sidelink feedback channel; or

a primary sidelink feedback channel and at least one secondary sidelink feedback channel.
The second device of claim 20, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to perform the channel occupancy procedure by:

performing a channel occupancy procedure on a valid sidelink feedback channel in the at least one sidelink feedback channel, wherein a sidelink feedback channel of the at least one sidelink feedback channel within the first time period is determined as the valid sidelink feedback channel.
The second device of claim 20, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to:

receive, from the first device, a second indication indicating that a portion of the at least one secondary sidelink feedback channel is disabled and

reuse the portion of the at least one secondary sidelink feedback channel for receiving the sidelink data transmission.
The second device of claim 20, wherein the sidelink feedback channel configuration indicates at least one of:

a position of the primary sidelink feedback channel;

a number of the at least one sidelink feedback channel;

an offset between neighboring sidelink feedback channels of the at least one sidelink feedback channel; and

at least one time unit associated with the at least one sidelink feedback channel.
The second device of claim 20, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to:

receive, from the first device, at least one of a Packet Delay Budget (PDB) for the sidelink data transmission and a traffic priority for the sidelink data transmission.
The second device of claim 24, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to adjust the first time period based on at least one of:

a Channel Occupancy Time (COT) for the unlicensed sidelink channel being shared to the second terminal device;

a Packet Delay Budget (PDB) for the sidelink data transmission;

a traffic priority for the sidelink data transmission; and

a statistic result of a historical delay between the time unit and a time occasion of receiving the NACK.
The second device of claim 24, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to:

determining whether the primary sidelink feedback channel is located within the COT; and

in accordance with a determination that the primary sidelink feedback channel is located within the COT, adjusting the first time period such that the first time period is terminated after the primary sidelink feedback channel and before a secondary sidelink feedback channel of the at least one secondary sidelink feedback channel.
The second device of claim 24, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to:

determining whether the PDB for the sidelink data transmission is smaller than a first duration threshold; and

in accordance with a determination that the PDB is smaller than the first duration threshold, adjusting the first time period such that the first time period is terminated after the primary sidelink feedback channel and before a secondary sidelink feedback channel of the at least one secondary sidelink feedback channel.
The second device of claim 24, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to:

determining whether the traffic priority for the sidelink data transmission is higher than a threshold priority level; and

in accordance with a determination that the traffic priority is higher than the threshold priority level, adjusting the first time period such that the first time period is terminated after the primary sidelink feedback channel and before a secondary sidelink feedback channel of the at least one secondary sidelink feedback channel.
The second device of claim 19, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to:

transmit the sidelink feedback channel configuration to the first device, wherein the sidelink feedback channel configuration is determined by the second device or is received from a third device.
The second device of claim 19, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to:

receive the sidelink feedback channel configuration from the first device; or

receive the sidelink feedback channel configuration from a third device.
The second device of claim 29 or 30, wherein the first device comprises a terminal device, wherein the second device comprises a terminal device and wherein the third device comprises a network device.
The second device of claim 19, wherein the first time period is received from the first terminal device.
The second device of claim 19, wherein the first time period is preconfigured.
The second device of claim 19, wherein the time unit comprises at least one of a slot, a symbol, a subframe and a frame.
The first device of claim 19, wherein the sidelink feedback channel configuration is configured for an unlicensed sidelink data transmission.
A method comprising:

detecting during a first time period, whether a Negative Acknowledgement (NACK) for a time unit is received from a second device on at least one sidelink feedback channel associated with the time unit, the time unit being used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel being indicated in a sidelink feedback channel configuration; and

in response to detecting that no NACK is received during the first time period, transmitting, from a first protocol layer to a second protocol layer, a first indication indicating that the sidelink data transmission in the time unit is successful, the second protocol layer being a higher protocol layer than the first protocol layer.
A method comprising:

performing, during a first time period, a channel occupancy procedure on at least one sidelink feedback channel for transmitting at least one of a Negative Acknowledgement (NACK) for a time unit and a positive Acknowledgement for the time unit, the time unit being used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel being indicated in a sidelink feedback channel configuration; and

in response to the channel occupancy procedure being successful, transmitting, to a first device, the at least one of the NACK and the ACK on the at least one sidelink feedback channel; or

in response to the channel occupancy procedure being failed, releasing a remaining sidelink feedback channel of the at least one sidelink feedback channel, the remaining sidelink feedback channel being a sidelink feedback channel of the at least one sidelink feedback channel other than the sidelink feedback channel on which the channel occupancy procedure is performed.
A first apparatus comprising:

means for detecting during a first time period, whether a Negative Acknowledgement (NACK) for a time unit is received from a second device on at least one sidelink feedback channel associated with the time unit, the time unit being used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel being indicated in a sidelink feedback channel configuration; and

means for in response to detecting that no NACK is received during the first time period, transmitting, from a first protocol layer to a second protocol layer, a first indication indicating that the sidelink data transmission in the time unit is successful, the second protocol layer being a higher protocol layer than the first protocol layer.
A second apparatus comprising:

means for performing, during a first time period, a channel occupancy procedure on at least one sidelink feedback channel for transmitting at least one of a Negative Acknowledgement (NACK) for a time unit and a positive Acknowledgement for the time unit, the time unit being used for a sidelink data transmission from the first device to the second device, the at least one sidelink feedback channel being indicated in a sidelink feedback channel configuration; and

means for in response to the channel occupancy procedure being successful, transmitting, to a first device, the at least one of the NACK and the ACK on the at least one sidelink feedback channel; or

means for in response to the channel occupancy procedure being failed during the first time unit, releasing a remaining sidelink feedback channel of the at least one sidelink feedback channel, the remaining sidelink feedback channel being a sidelink feedback channel of the at least one sidelink feedback channel other than the sidelink feedback channel on which the channel occupancy procedure is performed.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of Claim 36 or 37.