WO2024164147A1

WO2024164147A1 - Method, device and computer readable medium for sidelink communications

Info

Publication number: WO2024164147A1
Application number: PCT/CN2023/074817
Authority: WO
Inventors: Zhaobang MIAO; Jin Yang; Gang Wang
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2023-02-07
Filing date: 2023-02-07
Publication date: 2024-08-15
Anticipated expiration: 2025-08-07

Abstract

Embodiments of the present disclosure relate to method, device and computer readable media for sidelink communications. A first terminal device determines a first PSFCH occasion on a carrier in a set of carriers for sidelink communications based on at least one of the following: determination whether PSFCH occasions on the carriers are staggered or aligned with respect to one PSSCH occasion on one of the carriers, SCI received from a second terminal device, or a configuration or pre-configuration by higher layer. In turn, the first terminal device transmits or receives sidelink HARQ feedback information in the first PSFCH occasion. The sidelink HARQ feedback information is associated with at least one PSSCH transmission on at least one of the carriers. In this way, transmission or reception of HARQ feedback information on multiple carriers may be achieved.

Description

METHOD, DEVICE AND COMPUTER READABLE MEDIUM FOR SIDELINK COMMUNICATIONS

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication, and in particular, to a method, device and computer readable media for sidelink communications.

BACKGROUND

Work Item (WID) of sidelink carrier aggregation (CA) specifies mechanism to support New Radio (NR) sidelink CA operation based on Long Term Evolution (LTE) sidelink CA operation. NR sidelink CA operation is backwards compatible. For example, a Release 16 or Release 17 user equipment (UE) can receive Release 18 sidelink broadcast or groupcast transmissions with CA for a carrier on which it receives Physical Sidelink Control Channel (PSCCH) or Physical Sidelink Shared Channel (PSSCH) and transmits corresponding sidelink Hybrid Automatic Repeat Request (HARQ) feedback information (when SL-HARQ is enabled in sidelink control information) . How to transmit the HARQ feedback information on multiple carriers for CA operation is an open issue.

SUMMARY

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

In a first aspect, there is provided a first terminal device. The first terminal device comprises a processor. The processor is configured to cause the first terminal device to: determine a first Physical Sidelink Feedback Channel (PSFCH) occasion on a carrier in a set of carriers for sidelink communications based on at least one of the following: determination whether PSFCH occasions on the carriers are staggered or aligned with respect to one Physical Sidelink Shared Channel (PSSCH) occasion on one of the carriers, sidelink control information (SCI) received from a second terminal device, or a configuration or pre-configuration by higher layer, and transmit or receive sidelink Hybrid Automatic Repeat Request (HARQ) feedback information in the first PSFCH occasion, wherein the sidelink HARQ feedback information is associated with at least one PSSCH transmission on at least one of the carriers.

In a second aspect, there is provided a method for sidelink communications. The method comprises: determining, at a first terminal device, a first Physical Sidelink Feedback Channel (PSFCH) occasion on a carrier in a set of carriers for sidelink communications based on at least one of the following: determination whether PSFCH occasions on the carriers are staggered or aligned with respect to one Physical Sidelink Shared Channel (PSSCH) occasion on one of the carriers, sidelink control information (SCI) received from a second terminal device, or a configuration or pre-configuration by higher layer, and transmitting or receiving sidelink Hybrid Automatic Repeat Request (HARQ) feedback information in the first PSFCH occasion, wherein the sidelink HARQ feedback information is associated with at least one PSSCH transmission on at least one of the carriers.

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

It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. 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 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 communication network in which embodiments of the present disclosure can be implemented;

Fig. 2 illustrates an example of a timing resource allocation in a sidelink resource pool in accordance with some embodiments of the present disclosure;

Fig. 3 illustrates an example of Physical Sidelink Feedback Channel (PSFCH) resources in time domain in accordance with some embodiments of the present disclosure;

Fig. 4 illustrates an example of timing line between sidelink data transmissions on PSSCH and a PSFCH resource in accordance with some embodiments of the present disclosure;

Fig. 5 illustrates another example of mapping between a sidelink data transmission on PSSCH and a PSFCH resource in accordance with some embodiments of the present disclosure;

Fig. 6 illustrates a flowchart of an example method in accordance with some embodiments of the present disclosure;

Figs. 7A and 7B illustrate an example of PSFCH configurations for sidelink resource pools on carriers in accordance with some embodiments of the present disclosure, respectively;

Figs. 8A, 8B, 9, 10A, 10B and 11 illustrate an example of transmission of HARQ feedback information in a PSFCH occasion on one carrier in accordance with some embodiments of the present disclosure, respectively;

[Rectified under Rule 91, 10.04.2023]
Figs. 12A and 12B illustrate an example of selection of candidate carriers for sidelink communications in accordance with some embodiments of the present disclosure, respectively;

Fig. 13A and 13B illustrate an example of mapping between PSSCH transmissions and a PSFCH resource in accordance with some embodiments of the present disclosure, respectively;

Figs. 14A, 14B, 15A and 15B illustrate an example of transmission of HARQ feedback information in PSFCH occasions on carriers in accordance with some embodiments of the present disclosure, respectively;

Fig. 16 is a simplified block diagram of a device that is suitable for implementing some 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, 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, Ultra-reliable and Low Latency Communications (URLLC) 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) , Small Data Transmission (SDT) , mobility, Multicast and Broadcast Services (MBS) , positioning, dynamic/flexible duplex in commercial networks, reduced capability (RedCap) , Space borne vehicles or Air borne vehicles in Non-terrestrial networks (NTN) including Satellites and High Altitude Platforms (HAPs) encompassing Unmanned Aircraft Systems (UAS) , eXtended Reality (XR) devices including different types of realities such as Augmented Reality (AR) , Mixed Reality (MR) and Virtual Reality (VR) , the unmanned aerial vehicle (UAV) commonly known as a drone which is an aircraft without any human pilot, devices on high speed train (HST) , or image capture devices such as digital cameras, sensors, gaming devices, music storage and playback appliances, or Internet appliances enabling wireless or wired Internet access and browsing and the like. The ‘terminal device’ can further has ‘multicast/broadcast’ feature, to support public safety and mission critical, V2X applications, transparent IPv4/IPv6 multicast delivery, IPTV, smart TV, radio services, software delivery over wireless, group communications and IoT applications. It may also incorporate one or multiple Subscriber Identity Module (SIM) as known as Multi-SIM. The term “terminal device” can be used interchangeably with a UE, a mobile station, a subscriber station, a mobile terminal, a user terminal or a wireless device.

The term “network device” refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate. 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 NodeB (gNB) , a transmission reception point (TRP) , a remote radio unit (RRU) , a radio head (RH) , a remote radio head (RRH) , an IAB node, a low power node such as a femto node, a pico node, a reconfigurable intelligent surface (RIS) , Network-controlled Repeaters, and the like.

The terminal device or the network device may have Artificial intelligence (AI) or Machine learning capability. It generally includes a model which has been trained from numerous collected data for a specific function, and can be used to predict some information.

The terminal or the network device may work on several frequency ranges, e.g. FR1 (410 MHz –7125 MHz) , FR2 (24.25GHz to 71GHz) , frequency band larger than 100GHz as well as Tera Hertz (THz) . It can further work on licensed/unlicensed/shared spectrum. The terminal device may have more than one connection with the network devices under Multi-Radio Dual Connectivity (MR-DC) application scenario. The terminal device or the network device can work on full duplex, flexible duplex and cross division duplex modes.

The network device may have the function of network energy saving, Self-Organizing Networks (SON) /Minimization of Drive Tests (MDT) . The terminal may have the function of power saving.

The embodiments of the present disclosure may be performed in test equipment, e.g. signal generator, signal analyzer, spectrum analyzer, network analyzer, test terminal device, test network device, channel emulator

The embodiments of the present disclosure may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) communication protocols, 5.5G, 5G-Advanced networks, or the sixth generation (6G) networks.

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 ‘some embodiments’ and ‘an embodiment’ are to be read as ‘at least some embodiments. ’ 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. Other definitions, explicit and implicit, may be included below.

In some examples, values, procedures, or apparatus are referred to as ‘best, ’ ‘lowest, ’ ‘highest, ’ ‘minimum, ’ ‘maximum, ’ or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, higher, or otherwise preferable to other selections.

Fig. 1 illustrates a schematic diagram of an example communication network 100 in which embodiments of the present disclosure can be implemented. As shown in Fig. 1, the communication network 100 may include a first terminal device 110, a second terminal device 120, a third terminal device 120, network devices 140 and 150. The network devices 140 and 150 may communicate with the first terminal device 110, the second terminal device 120 and the third terminal device 120 via respective wireless communication channels.

In some embodiments, the network device 140 may be a gNB in NR. Thus, the network device 140 may be also referred to as an NR network device 140.

In some embodiments, the network device 150 may be an eNB in Long Term Evolution (LTE) system. Thus, the network device 150 may be also referred to as an LTE network device 150.

It is to be understood that the number of devices in Fig. 1 is given for the purpose of illustration without suggesting any limitations to the present disclosure. The communication network 100 may include any suitable number of network devices and/or terminal devices adapted for implementing embodiments of the present disclosure.

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

In some embodiments, the communications in the communication network 100 may comprise sidelink communication. Sidelink communication is a wireless radio communication directly between two or more terminal devices, such as two or more terminal devices among the first terminal device 110, the second terminal device 120 and the third terminal device 120. In this type of communication, the two or more terminal devices that are geographically proximate to each other can directly communicate without going through the network device 140 or 150 or through a core network. Data transmission in sidelink communication is thus different from typical cellular network communications, in which a terminal device transmits data to the network device 140 or 150 (i.e., uplink transmissions) or receives data from the network device 140 or 150 (i.e., downlink transmissions) . In sidelink communication, data is transmitted directly from a source terminal device (such as the first terminal device 110) to a target terminal device (such as the second terminal device 120) through the Unified Air Interface, e.g., PC5 interface, (i.e., sidelink transmissions) , as shown in Fig. 1.

Sidelink communication can provide several advantages, including reducing data transmission load on a core network, system resource consumption, transmission power consumption, and network operation costs, saving wireless spectrum resources, and increasing spectrum efficiency of a cellular wireless communication system.

In a sidelink communication system, the sidelink resource is used to transmit information between terminal devices. According to application scenarios, service types, etc., a sidelink communication manner includes but is not limited to device to device (D2D) communication, Vehicle-to-Everything (V2X) communication, etc.

V2X communication enables vehicles to communicate with other vehicles (i.e. Vehicle-to-Vehicle (V2V) communication) , with infrastructure (i.e. Vehicle-to-Infrastructure (V2I) , with wireless networks (i.e. Vehicle-to-Network (V2N) communication) , with pedestrians (i.e. Vehicle-to-Pedestrian (V2P) communication) , and even with the owner's home (i.e. Vehicle-to-Home (V2H) ) . Examples of infrastructure include roadside units such as traffic lights, toll gates and the like. V2X communication can be used in a wide range of scenarios, including in accident prevention and safety, convenience, traffic efficiency and clean driving, and ultimately in relation to autonomous or self-driving vehicles.

For sidelink communications, a terminal device uses resources in sidelink resource pools to transmit or receive signals. The sidelink resource pools include resources in time domain and frequency domain, which are dedicated resources of the sidelink communication, or shared by the sidelink communication and a cellular link. For sidelink communications, two modes of resource assignment may be used for sidelink, including network device schedules sidelink resources for terminal devices to perform sidelink signal transmission, named as mode 1 resource scheme in NR sidelink or mode 3 resource scheme in LTE sidelink, and terminal device selects sidelink resources by itself to perform sidelink signal transmission, named as mode 2 resource scheme in NR sidelink or mode 4 resource scheme in LTE sidelink.

Fig. 2 illustrates an example of a time resource allocation in a sidelink resource pool in accordance with some embodiments of the present disclosure. In some embodiments, the sidelink resource pool may comprise an NR sidelink resource pool. In such embodiments, the sidelink resource pool may be defined within a sidelink bandwidth part (BWP) . The first terminal device 110, the second terminal device 120 and the third terminal device 120 may use uplink (UL) resources for sidelink communications. More than one sidelink resource pools may be configured for one of the first terminal device 110, the second terminal device 120 and the third terminal device 120. A dedicated resource pool may be used for mode 1 resource scheme or mode 2 resource scheme, short for mode 1 resource pool or mode 2 resource pool. For LTE sidelink, a dedicated resource pool may be used for mode 3 resource scheme or mode 4 resource scheme, short for mode 3 resource pool or mode 4 resource pool. Resources within the sidelink resource pool may comprise Physical Sidelink Control Channel (PSCCH) resources, Physical Sidelink Shared Channel (PSSCH) resources and physical sidelink feedback channel (PSFCH) resources. A bitmap may be used to indicate which UL slots are configured as sidelink slots. A length of the bitmap may be in a range of 10 to 160.

The first terminal device 110, the second terminal device 120 and the third terminal device 120 may use sidelink channels to transmit sidelink signaling or information. The sidelink channels include at least one of the following: a PSCCH resource which is used for carrying sidelink control information (SCI) , a PSSCH resource which is used for carrying sidelink data service information, a PSFCH resource which is used for carrying sidelink Hybrid Automatic Repeat Request (HARQ) feedback information, a physical sidelink broadcast channel (PSBCH) resource which is used for carrying sidelink broadcast information, and a physical sidelink discovery channel (PSDCH) resource which is used for carrying a sidelink discovery signal.

Within a resource pool, whether a PSFCH resource is available should be configured or pre-configured. In time domain, according to the configuration or pre-configuration of a resource pool, one of every N slots in the resource pool contains PSFCH resources, N= [0, 1, 2, 4] . In a sidelink resource pool, PSCCH or PSSCH resources are presented in every slot and used for transmitting sidelink data packet. Within a slot containing a PSFCH resource, the last three SL symbols (AGC+PSFCH+GP) are used for PSFCH related, as shown in Fig. 3.

A PSFCH resource may comprises one RB in frequency domain and one symbol in time domain (AGC symbol is repeated) . In addition, the PSFCH resource may carry 1 bit ACK/NACK information. Furthermore, the PSFCH resource may be related to one sub-channel in one slot.

While PSFCH is used for carrying sidelink HARQ feedback information associated with a sidelink data transmission on the assigned slots. Based on that, the time intervals between HARQ feedback information on PSFCH and the associated sidelink data transmission on PSSCH are various. As an example shown in Fig. 4, where N=4, i.e., one out of every four slots in the resource pool contains a PSFCH resource.

There is an N-to-one mapping relationship in time domain between PSSCH and PSFCH. For the data transmission on PSSCH in slot #n, the associated HARQ feedback information should be reported in slot #n+k, k >=K. K represents a minimum time gap between a PSFCH occasion and a PSSCH occasion. Hereinafter, K is also referred to as “Gap” . K may be configured or pre-configured through high layer. For example, K may be configured as K= [2, 3] by sl-MinTimeGapPSFCH. As shown in Fig. 4, K=2 slots. Accordingly, the HARQ feedback information associated with the PSSCH in slots #n and #n+1 should be reported on PSFCH in slot #n+3, and the HARQ feedback information associated with the PSSCH in slots #n+2, #n+3, n+4 and n+5 should be reported on PSFCH in slot #n+7.

In frequency domain, the RBs used as PSFCH resources should be configured by bitmap. Based on that, the assigned RBs for PSFCH resources should be allocated to carry the sidelink HARQ feedback information associated with data transmissions on PSSCH. This will be described with reference to Fig. 5.

Fig. 5 illustrates an example of mapping between a sidelink data transmission on PSSCH and a PSFCH resource in prior art. In the example of Fig. 5, a period of PSFCH resources is equal to 2 and K is equal to 2. Hereinafter, the period of PSFCH resources is also referred to as PSFCH period for brevity. represents the number of RBs in a resource pool configured for feedback channel resources. represents the number of RBs for carrying HARQ feedback information associated with a data transmission within a sub-channel in a slot, wheremay be determined based on the following:

where N_subch represents the number of sub-channels in the resource pool, andrepresents a period of PSFCH resources. In the example of Fig. 5,

HARQ feedback information associated with a data transmission on PSSCH with a sub-channel 510 in slot #n should be reported on an RB 511 in slot #n+3. HARQ feedback information associated with a data transmission on PSSCH with a sub-channel 530 in slot #n should be reported on an RB 512 in slot #n+3. HARQ feedback information associated with a data transmission on PSSCH with the sub-channel 520 in slot #n+1 should be reported on an RB 521 in slot #n+3. HARQ feedback information associated with a data transmission on PSSCH with the sub-channel 540 in slot #n+1 should be reported on an RB 522 in slot #n+3.

As described above, if a terminal device receives PSSCH transmission, it should transmit HARQ feedback information associated with the PSSCH transmission on PSFCH. How to transmit the HARQ feedback information on multiple carriers for CA operation is an open issue.

Embodiments of the present disclosure provide a solution for sidelink communications. According to the solution, a first terminal device determines a first PSFCH occasion on a carrier in a set of carriers for sidelink communications based on at least one of the following: determination whether PSFCH occasions on the carriers are staggered or aligned with respect to one PSSCH occasion on one of the carriers, SCI received from a second terminal device, or a configuration or pre-configuration by higher layer. In turn, the first terminal device transmits or receives sidelink HARQ feedback information in the first PSFCH occasion. The sidelink HARQ feedback information is associated with at least one PSSCH transmission on at least one of the carriers. In this way, transmission or reception of HARQ feedback information on multiple carriers may be achieved. Hereinafter, principle of the present disclosure will be described with reference to Figs. 6 to 15.

Fig. 6 illustrates a flowchart of an example method in accordance with some embodiments of the present disclosure. In some embodiments, the method 800 can be implemented at a terminal device, such as one of the first terminal device 110, the second terminal device 120 and the third terminal device 120 as shown in Fig. 1. For the purpose of discussion, the method 800 will be described with reference to Fig. 1 as performed by the first terminal device 110 without loss of generality.

At block 610, the first terminal device 110 determines a first PSFCH occasion on a carrier in a set of carriers for sidelink communications based on at least one of the following:

· determination whether PSFCH occasions on the carriers are staggered or aligned with respect to one PSSCH occasion on one of the carriers,

· SCI received from the second terminal device 120, or

· a configuration or pre-configuration by higher layer.

At block 620, the first terminal device 110 transmits or receives sidelink HARQ feedback information in the first PSFCH occasion. The sidelink HARQ feedback information is associated with at least one PSSCH transmission on at least one of the carriers.

In some embodiments, the first terminal device 110 may act as a transmission terminal device which is also referred to as a TX UE. The transmission terminal device performs a PSSCH transmission in a PSSCH occasion and receives, in a PSFCH occasion, sidelink HARQ feedback information associated with the PSSCH transmission. In this regard, the PSFCH occasion may be a PSFCH reception occasion, and the PSSCH occasion may be a PSSCH transmission occasion.

In other embodiments, the first terminal device 110 may act as a receiving terminal device which is also referred to as a RX UE. The receiving terminal device receives a PSSCH transmission in a PSSCH occasion and transmits, in a PSFCH occasion, sidelink HARQ feedback information associated with the PSSCH transmission. In this regard, the PSFCH occasion may be a PSFCH transmission occasion, and the PSSCH occasion may be a PSSCH reception occasion.

In embodiments where the set of carriers comprises multiple carriers for sidelink communications (such as sidelink CA) , each of the carriers is also referred to as a component carrier (CC) .

In some embodiments, the one PSSCH occasion on one of the carriers may be a given PSSCH occasion on one of the carriers. For example, the given PSSCH occasion may comprise a starting PSSCH occasion on one of the carriers.

In some embodiments, the HARQ feedback information to be transmitted or received in the first PSFCH occasion is associated with multiple PSSCH transmissions on the carriers in the set of carriers. In other words, HARQ feedback information associated with multiple PSSCH transmissions on the carriers is to be transmitted or received only in one PSFCH occasion on one carrier in the set of carriers.

In some embodiments, the first terminal device 110 may determine whether the PSFCH occasions are staggered or aligned with respect to the one PSSCH occasion based on PSFCH configurations for sidelink resource pools on the carriers.

In some embodiments, the set of carriers at least comprises a first carrier and a second carrier. If a first PSFCH configuration for a first sidelink resource pool on the first carrier is different from a second PSFCH configuration for a second sidelink resource pool on the second carrier, the first terminal device 110 may determine that the PSFCH occasions are staggered with respect to the one PSSCH occasion.

In some embodiments, the first PSFCH configuration indicates a first period of PSFCH occasions on the first carrier and a first minimum time gap between a PSFCH occasion on the first carrier and a PSSCH occasion on the first carrier. The second PSFCH configuration indicates a second period of PSFCH occasions on the second carrier and a second minimum time gap between a PSFCH occasion on the second carrier and a PSSCH occasion on the second carrier.

In some embodiments, if the first period of PSFCH occasions on the first carrier is different from the second period of PSFCH occasions on the second carrier, the first PSFCH configuration is different from the second PSFCH configuration. Alternatively, if the first minimum time gap is different from the second minimum time gap, the first PSFCH configuration is different from the second PSFCH configuration. This will be described with reference to Figs. 7A and 7B.

Figs. 7A and 7B illustrate an example of PSFCH configurations for sidelink resource pools on carriers in accordance with some embodiments of the present disclosure, respectively.

In examples of Figs. 7A and 7B, a first PSFCH configuration for a first sidelink resource pool on CC#1 is different from a second PSFCH configuration for a second sidelink resource pool on CC#2. A first Subcarrier Spacing (SCS) for CC#1 is the same as a second SCS for CC#2.

Specifically, in the example of Fig. 7A, a first period of PSFCH occasions on CC#1 is equal to 2 and a second period of PSFCH occasions on CC#2 is equal to 4. A first minimum time gap between a PSFCH occasion on CC#1 and a PSSCH occasion on CC#1 is equal to 2 and a second minimum time gap between a PSFCH occasion on CC#2 and a PSSCH occasion on CC#2 is equal to 2.

In the example of Fig. 7B, a first period of PSFCH occasions on CC#1 is equal to 2 and a second period of PSFCH occasions on CC#2 is equal to 2. A first minimum time gap between a PSFCH occasion on CC#1 and a PSSCH occasion on CC#1 is equal to 2 and a second minimum time gap between a PSFCH occasion on CC#2 and a PSSCH occasion on CC#2 is equal to 3.

In the examples of Figs. 7A and 7B, for single CC#1 operation, HARQ feedback information associated with PSSCH transmission in slot #1 on CC#1 should be transmitted on PSFCH occasion in slot #3 on CC#1. For single CC#2 operation, HARQ feedback information associated with PSSCH transmission in slot #1 on CC#2 should be transmitted on PSFCH occasion in slot #5 on CC#2. Thus, PSFCH occasion in slot #3 on CC#1 and PSFCH occasion in slot #5 on CC#2 are staggered with respect to a starting PSSCH occasion in slot #1 on one of CC#1 and CC#2.

In some embodiments, if the PSFCH occasions on the first and second carriers are staggered with respect to the one PSSCH occasion on one of the carriers, the first terminal device 110 may determine an ending PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion. This will be described with reference to Figs. 8A and 8B.

Figs. 8A and 8B illustrate an example of transmission of HARQ feedback information in a PSFCH occasion on one carrier in accordance with some embodiments of the present disclosure, respectively.

In examples of Figs. 8A and 8B, the first PSFCH configuration for the first sidelink resource pool on CC#1 and the second PSFCH configuration for the second sidelink resource pool on CC#2 are the same as those in the examples of Figs. 7A and 7B, respectively.

As described with reference to Figs. 7A and 7B, PSFCH occasion in slot #3 on CC#1 and PSFCH occasion in slot #5 on CC#2 are staggered with respect to one PSSCH occasion in slot #1 on one of CC#1 and CC#2.

In examples of Figs. 8A and 8B, the first terminal device 110 may determine an ending PSFCH occasion among CC#1 and CC#2. For example, the first terminal device 110 may determine a PSFCH occasion in slot #5 on CC#2 as the ending PSFCH occasion among CC#1 and CC#2. In turn, the first terminal device 110 may transmit or receive, in the ending PSFCH occasion, HARQ feedback information associated with multiple PSSCH transmissions on CC#1 and CC#2. In this way, half-duplex issue between PSFCH transmission (or reception) and PSSCH reception (or transmission) in slot #3 may be avoided.

In embodiments where the first period of PSFCH occasions on the first carrier is different form the second period of PSFCH occasions on the second carrier, the first terminal device 110 may determine an ending PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion, as shown in Fig. 8A. In turn, the first terminal device 110 may transmit or receive, in the first PSFCH occasion (i.e., the ending PSFCH occasion) , HARQ feedback information associated with multiple PSSCH transmissions on the first and second carriers.

In some embodiments, the first period is the same as the second period while the first minimum time gap between a PSFCH occasion on the first carrier and a PSSCH occasion on the first carrier is different from the second minimum time gap between a PSFCH occasion on the second carrier and a PSSCH occasion on the second carrier. In such embodiments, the first terminal device 110 may determine a starting PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion. In turn, the first terminal device 110 may transmit or receive, in the first PSFCH occasion (i.e., the starting PSFCH occasion) , HARQ feedback information associated with multiple PSSCH transmissions on the first and second carriers. This will be described with reference to Fig. 9.

Fig. 9 illustrates an example of transmission of HARQ feedback information in a PSFCH occasion on one carrier in accordance with some embodiments of the present disclosure.

In the example of Fig. 9, the first PSFCH configuration for the first sidelink resource pool on CC#1 and the second PSFCH configuration for the second sidelink resource pool on CC#2 are the same as those in the example of Fig. 7B.

Specifically, the first period of PSFCH occasions on CC#1 is equal to 2 and the second period of PSFCH occasions on CC#2 is equal to 2. That is, the first period is the same as the second period. The first minimum time gap between a PSFCH occasion on CC#1 and a PSSCH occasion on CC#1 is equal to 2 and the second minimum time gap between a PSFCH occasion on CC#2 and a PSSCH occasion on CC#2 is equal to 3. That is, the first minimum time gap is different from the second minimum time gap. Thus, the first terminal device 110 may determine a starting PSFCH occasion among CC#1 and CC#2 as the first PSFCH occasion. That is, the first terminal device 110 may determine a PSFCH occasion in slot #3 on CC#1 as the first PSFCH occasion. In turn, the first terminal device 110 may transmit or receive, in the first PSFCH occasion, HARQ feedback information associated with multiple PSSCH transmissions on CC#1 and CC#2.

In some embodiments, if PSFCH occasions on the carriers are staggered with respect to one PSSCH occasion on one of the carriers, the first terminal device 110 may determine a starting PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion. In turn, the first terminal device 110 may transmit or receive, in the first PSFCH occasion (i.e., the starting PSFCH occasion) , HARQ feedback information associated with multiple PSSCH transmissions on the first and second carriers. This will be described with reference to Figs. 10 A and 10B.

Figs. 10A and 10B illustrate an example of transmission of HARQ feedback information in a PSFCH occasion on one carrier in accordance with some embodiments of the present disclosure, respectively.

In examples of Figs. 10A and 10B, the first PSFCH configuration for the first sidelink resource pool on CC#1 and the second PSFCH configuration for the second sidelink resource pool on CC#2 are the same as those in the examples of Figs. 7A and 7B, respectively.

As described with reference to Figs. 7A and 7B, PSFCH occasion in slot #3 on CC#1 and PSFCH occasion in slot #5 on CC#2 are staggered with respect to the starting PSSCH occasion in slot #1 on CC#1 or CC#2.

In the examples of Figs. 10A and 10B, the first terminal device 110 may determine a starting PSFCH occasion among CC#1 and CC#2. For example, the first terminal device 110 may determine a PSFCH occasion in slot #3 on CC#1 as the starting PSFCH occasion among CC#1 and CC#2. In turn, the first terminal device 110 may transmit or receive, in the starting PSFCH occasion, HARQ feedback information associated with multiple PSSCH transmissions on CC#1 and CC#2. In this way, earlier transmission of HARQ feedback information may be achieved.

In the examples of Figs. 10A and 10B, the first terminal device 110 may need to handle the half-duplex issue in slot #3. In other words, the first terminal device 110 may need to handle simultaneous (overlapped in time) PSFCH transmission and PSSCH reception in slot #3 or simultaneous (overlapped in time) PSFCH reception and PSSCH transmission in slot #3.

In some embodiments, in order to handle the half-duplex issue, the first terminal device 110 may perform PSFCH transmission or PSSCH reception based on priorities of the PSFCH transmission (or reception) and PSSCH reception (or transmission) . For example, if a first priority of the sidelink HARQ feedback information is higher than a second priority of the PSSCH reception or transmission, the first terminal device 110 may transmit or receive the sidelink HARQ feedback information in slot #3 and drop the PSSCH reception or transmission in slot #3.

In some embodiments, the first priority of the sidelink HARQ feedback information is also referred to as a priority of PSFCH transmission or reception with HARQ feedback information. The priority of PSFCH transmission or reception with HARQ feedback information may be equal to a priority value indicated by an SCI format 1-A associated with the PSFCH transmission or reception. For example, the second terminal device 120 may perform a PSSCH transmission to the first terminal device 110 in slot#1 on CC#1 and transmit an SCI format 1-A associated with the PSSCH transmission. The SCI format 1-A may indicate a priority value. The first terminal device 110 may determine the priority value indicated in the SCI format 1-A as the priority of PSFCH transmission or reception with HARQ feedback information for the PSSCH transmission.

In such embodiments, the first terminal device 110 may determine the priorities of the PSFCH transmission (or reception) and PSSCH reception (or transmission) before a time duration prior to a start of the earlier one of the PSFCH and PSSCH. For example, as shown in Fig. 10A, a start of PSSCH reception in slot #3 is earlier than a start of PSFCH transmission in slot #3. Before a time duration (represented by delta_t) prior to the start of the PSSCH reception in slot #3, the first terminal device 110 may determine the priorities.

Alternatively, in some embodiments, in order to handle the half-duplex issue, the first terminal device 110 may always prioritize the PSFCH transmission or reception. That is, the first terminal device 110 may always perform the PSFCH transmission/reception in slot #3 and drop the PSSCH reception/transmission in slot #3.

In some embodiments, the first terminal device 110 may determine whether the PSFCH occasions are staggered or aligned with respect to the one PSSCH occasion based on time resource allocations for the sidelink resource pools on the carriers.

In some embodiments, if a first time resource allocation for a first sidelink resource pool on the first carrier is different from a second time resource allocation for a second sidelink resource pool on the second carrier, the first terminal device 110 may determine that the PSFCH occasions are staggered with respect to the one PSSCH occasion. This will be described with reference to Fig. 11.

Fig. 11 illustrates an example of transmission of HARQ feedback information in a PSFCH occasion on one carrier in accordance with some embodiments of the present disclosure.

In the example of Fig. 11, a first time resource allocation for a first sidelink resource pool on CC#1 is different from a second time resource allocation for a second sidelink resource pool on CC#2. Thus, the first terminal device 110 may determine that PSFCH occasions on CC#1 and CC#2 are staggered with respect to a starting PSSCH occasion in slot #1 on one of CC#1 and CC#2.

In the example of Fig. 11, the carrier comprising the first PSFCH occasion for transmission of the HARQ feedback information may be indicated by the SCI. The SCI may be received from the second terminal device 120 which performs one or more PSSCH transmission to the first terminal device 110. Alternatively, the carrier comprising the first PSFCH occasion for transmission of the HARQ feedback information may be determined based on the configuration or pre-configuration by higher layer.

Similar to the examples of Figs. 10A and 10B, in the example of Fig. 11, the first terminal device 110 may also need to handle the half-duplex issue. For example, as described with reference to Figs. 10A and 10B, in order to handle the half-duplex issue, the first terminal device 110 may perform PSFCH transmission or PSSCH reception based on priorities of the PSFCH transmission (or reception) and PSSCH reception (or transmission) . Alternatively, the first terminal device 110 may always prioritize the PSFCH transmission or reception.

In some embodiments, if the PSFCH occasions on the carriers are aligned with respect to one PSSCH occasion on one of the carriers, the first terminal device 110 may determine a PSFCH occasion on any of the carriers as the first PSFCH occasion. In turn, the first terminal device 110 may transmit or receive, in the first PSFCH occasion, HARQ feedback information associated with multiple PSSCH transmissions on the carriers.

In some embodiments, the carrier comprising the first PSFCH occasion for transmission of the HARQ feedback information may be selected by the second terminal device 120 which performs one or more PSSCH transmission to the first terminal device 110. In addition, the second terminal device 120 may transmit the SCI indicating the carrier comprising the first PSFCH occasion. Alternatively, the carrier comprising the first PSFCH occasion for transmission of the HARQ feedback information may be determined based on the configuration or pre-configuration by higher layer.

In order to ensure that the PSFCH occasions on the carriers are aligned with respect to one PSSCH occasion on one of the carriers, the first terminal device 110 may select a first candidate carrier and a second candidate carrier as carriers in the set of carriers based on determining at least one of the following:

· a first SCS for the first candidate carrier is the same as a second SCS for the second candidate carrier, or

· a first PSFCH configuration for a first sidelink resource pool on the first candidate carrier is the same as a second PSFCH configuration for a second sidelink resource pool on the second candidate carrier.

Figs. 12A and 11B illustrate an example of selection of candidate carriers for sidelink communications in accordance with some embodiments of the present disclosure, respectively.

In the example of Fig. 12A, it is assumed that each of CCs #1, #2, #3 and #4 contains only one sidelink resource pool. Subcarrier Spacings (SCSs) for CCs #1, #2, #3 and #4 are the same as each other.

A first PSFCH configuration for a first sidelink resource pool on CC#1 is the same as a second PSFCH configuration for a second sidelink resource pool on CC#2. Specifically, a first period of PSFCH occasions on CC#1 is equal to 2 and a second period of PSFCH occasions on CC#2 is equal to 2. A first minimum time gap between a PSFCH occasion on CC#1 and a PSSCH occasion on CC#1 is equal to 2 and a second minimum time gap between a PSFCH occasion on CC#2 and a PSSCH occasion on CC#2 is equal to 2.

A third PSFCH configuration for a third sidelink resource pool on CC#3 is different from any of the following: the first PSFCH configuration for a first sidelink resource pool on CC#1, the second PSFCH configuration for a second sidelink resource pool on CC#2, and a fourth PSFCH configuration for a third sidelink resource pool on CC#4. Specifically, a third period of PSFCH occasions on CC#3 is equal to 4. A third minimum time gap between a PSFCH occasion on CC#3 and a PSSCH occasion on CC#3 is equal to 2.

A fourth PSFCH configuration for a fourth sidelink resource pool on CC#4 is different from any of the following: the first PSFCH configuration for a first sidelink resource pool on CC#1, the second PSFCH configuration for a second sidelink resource pool on CC#2, and the third PSFCH configuration for a fourth sidelink resource pool on CC#3. Specifically, a fourth period of PSFCH occasions on CC#4 is equal to 2. A fourth minimum time gap between a PSFCH occasion on CC#4 and a PSSCH occasion on CC#4 is equal to 3.

Therefore, in the example of Fig. 12A, the first terminal device 110 may select CCs #1 and #2 as carriers in the set of carriers for sidelink communications, such as sidelink CA.

In the example of Fig. 12B, it is assumed that each of CCs #1 and #2 contains two sidelink resource pools. Subcarrier Spacings (SCSs) for CCs #1 and #2 are the same as each other.

A first PSFCH configuration for a first sidelink resource pool on CC#1 is the same as a fourth PSFCH configuration for a fourth sidelink resource pool on CC#2. Specifically, a first period of PSFCH occasions on CC#1 is equal to 2 and a fourth period of PSFCH occasions on CC#2 is equal to 2. A first minimum time gap between a PSFCH occasion on CC#1 and a PSSCH occasion on CC#1 is equal to 2 and a fourth minimum time gap between a PSFCH occasion on CC#2 and a PSSCH occasion on CC#4 is equal to 2.

Therefore, in the example of Fig. 12B, the first terminal device 110 may select CCs #1 and #2 as carriers in the set of carriers for sidelink communications, such as sidelink CA.

In some embodiments, to overcome backward compatible issue, PSFCH transmission in CA operation should not impact the legacy PSFCH to PSSCH mapping on each of the carriers in the set of carriers.

In such embodiments, in order to transmit or receive the HARQ feedback information associated with multiple PSSCH transmissions on the carriers, the first terminal device 110 may determine at least one set of PSFCH resources in the first PSFCH occasion. The at least one set of PSFCH resources is associated with a PSSCH transmission on the carrier. In turn, the first terminal device 110 may transmit or receive, on at least one PSFCH resource in the at least one set of PSFCH resources, the HARQ feedback information associated with multiple PSSCH transmissions on the carriers.

In some embodiments, the HARQ feedback information associated with multiple PSSCH transmissions on the carriers comprises a joint decoding result of the multiple PSSCH transmissions on the carriers. This will be described with reference to Fig. 13A.

Fig. 13A illustrates an example of mapping between PSSCH transmissions and a PSFCH resource in accordance with some embodiments of the present disclosure.

In the example of Fig. 13A, the first terminal device 110 (also referred to as UE A) receives a first PSSCH transmission on sub-channels #2 and 6 on CC#1 from the second terminal device 120 (also referred to as UE B) . The first terminal device 110 receives a second PSSCH transmission on sub-channels #2 and 6 on CC#2 from the second terminal device 120 or the third terminal device 130.

In the example of Fig. 13A, HARQ feedback information associated with the first and second PSSCH transmissions on CC#1 and CC#2 comprises a joint decoding result of the first and second PSSCH transmissions on CC#1 and CC#2. The joint decoding result is also referred to as a joint HARQ-ACK.

For example, the joint decoding result may be a negative acknowledge (NACK) if at least one of the first and second PSSCH transmissions is NACK in NACK-only feedback and ACK-and-NACK feedback options. The joint decoding result may be a positive acknowledge (ACK) if all of the first and second PSSCH transmissions is ACK in ACK-and-NACK feedback option.

In some embodiments, the first terminal device 110 may determine a first set of PSFCH resources 1310 with an index of 2. The first set of PSFCH resources 1310 is associated with the first PSSCH transmission on sub-channels #2 and 6 on CC#1. In turn, the first terminal device 110 may transmit the joint decoding result on a PSFCH resource in the first set of PSFCH resources 1310.

In some embodiments, the first terminal device 110 may determine the PSFCH resource in the first set of PSFCH resources 1310 based on at least one of the following:

· a physical layer source identity of the second terminal device 120 performing the first PSSCH transmission on CC#1,

· a member identity of the first terminal device 110,

· the number of physical resource blocks in the first set of PSFCH resources 1310, or

· the number of configured or pre-configured cyclic shift (CS) pairs.

For example, the first terminal device 110 may determine the PSFCH resource in the first set of PSFCH resources 1310 based on the following:(S_ID+M_ID) MOD (M1*CS)

where S_ID represents the physical layer source identity of the second terminal device 120 performing the first PSSCH transmission on CC#1, M_ID represents the member identity of the first terminal device 110, M1 represents the number of physical resource blocks in the first set of PSFCH resources 1310, and CS represents the number of the configured or pre-configured cyclic shift pairs.

Alternatively, in some embodiments, the first terminal device 110 may determine additionally a second set of PSFCH resources 1320 with an index of 2 and 6. The second set of PSFCH resources 1320 is associated with the first PSSCH transmission on sub-channels #2 and 6 on CC#1. In turn, the first terminal device 110 may transmit the joint decoding result on a PSFCH resource in the first set of PSFCH resources 1310 and the second set of PSFCH resources 1320.

In some embodiments, the first terminal device 110 may determine the PSFCH resource in the first set of PSFCH resources 1310 and the second set of PSFCH resources 1320 based on at least one of the following:

· a physical layer source identity of the second terminal device 120 performing the first PSSCH transmission on CC#1 and the second PSSCH transmission on CC#2,

· a member identity of the first terminal device 110,

· the number of physical resource blocks in the first set of PSFCH resources 1310 and the second set of PSFCH resources 1320, or

· the number of configured or pre-configured cyclic shift (CS) pairs.

For example, the first terminal device 110 may determine the PSFCH resource in the first set of PSFCH resources 1310 and the second set of PSFCH resources 1320 based on the following:(S_ID+M_ID) MOD (M*CS)

where S_ID represents the physical layer source identity of the second terminal device 120 performing the first PSSCH transmission on CC#1 and the second PSSCH transmission on CC#2, M_ID represents the member identity of the first terminal device 110, M represents the number of physical resource blocks in the first set of PSFCH resources 1310 and the second set of PSFCH resources 1320, and CS represents the number of configured or pre-configured cyclic shift (CS) pairs.

In some embodiments, the HARQ feedback information associated with multiple PSSCH transmissions on the carriers comprises multiple sets of HARQ feedback information for the multiple PSSCH transmissions on the carriers. This will be described with reference to Fig. 13B.

Fig. 13B illustrates an example of mapping between PSSCH transmissions and a PSFCH resource in accordance with some embodiments of the present disclosure.

The example of Fig. 13B is similar to the example of Fig. 13A. The example of Fig. 13B is different from the example of Fig. 13A in that HARQ feedback information associated with the first and second PSSCH transmissions on CC#1 and CC#2 comprises a first set of HARQ feedback information for the first PSSCH transmission (represented by HARQ-ACK 1) and a second set of HARQ feedback information for the second PSSCH transmission (represented by HARQ-ACK 2) .

The first terminal device 110 may determine a first PSFCH resource in the first set of PSFCH resources 1310 and the second set of PSFCH resources 1320. In turn, the first terminal device 110 transmits the HARQ-ACK 1 on the first PSFCH resource.

In some embodiments, the first terminal device 110 may determine the first PSFCH resource in the first set of PSFCH resources 1310 based on at least one of the following:

· a member identity of the first terminal device 110,

· the number of physical resource blocks in the first set of PSFCH resources 1310,

· the number of configured or pre-configured cyclic shift (CS) pairs, or

· an index of CC#1.

For example, the first terminal device 110 may determine the first PSFCH resource in the first set of PSFCH resources 1310 based on the following:(S_ID+M_ID+CC_ID) MOD (M1*CS)

where S_ID represents the physical layer source identity of the second terminal device 120 performing the first PSSCH transmission on CC#1, M_ID represents the member identity of the first terminal device 110, M1 represents the number of physical resource blocks in the first set of PSFCH resources 1310, CS represents the number of configured or pre-configured cyclic shift (CS) pairs, and CC_ID represents the index of CC#1. The CC_ID may be in a range of 1 to the number of carriers in the set of carriers. The CC_ID may be equal to zero for single CC operation.

Alternatively, in some embodiments, the first terminal device 110 may determine the first PSFCH resource in the first set of PSFCH resources 1310 and the second set of PSFCH resources 1320 based on at least one of the following:

· a member identity of the first terminal device 110,

· the number of physical resource blocks in the first set of PSFCH resources 1310 and the second set of PSFCH resources 1320,

· the number of configured or pre-configured cyclic shift (CS) pairs, or

· an index of CC#1.

For example, the first terminal device 110 may determine the first PSFCH resource in the first set of PSFCH resources 1310 and the second set of PSFCH resources 1320 based on the following:(S_ID+M_ID+CC_ID) MOD (M*CS)

where S_ID represents the physical layer source identity of the second terminal device 120 performing the first PSSCH transmission on CC#1 and the second PSSCH transmission on CC#2, M_ID represents the member identity of the first terminal device 110, M represents the number of physical resource blocks in the first set of PSFCH resources 1310 and the second set of PSFCH resources 1320, CS represents the number of configured or pre-configured cyclic shift (CS) pairs and CC_ID represents the index of CC#1.

Similarly, the first terminal device 110 may determine a second PSFCH resource in the first set of PSFCH resources 1310 or in the first set of PSFCH resources 1310 and the second set of PSFCH resources 1320. In turn, the first terminal device 110 transmits the HARQ-ACK 2 on the second PSFCH resource.

In some embodiments, the HARQ feedback information to be transmitted or received in the first PSFCH occasion on a carrier is only associated with at least one PSSCH transmission on the carrier. This will be described with reference to Figs. 14A and 14B.

Figs. 14A and 14B illustrate an example of transmission of HARQ feedback information in PSFCH occasions on carriers in accordance with some embodiments of the present disclosure, respectively.

In the example of Fig. 14A, a first PSFCH configuration for a first sidelink resource pool on CC#1 is different from a second PSFCH configuration for a second sidelink resource pool on CC#2. Thus, PSFCH occasion in slot #3 on CC#1 and PSFCH occasion in slot #5 on CC#2 are staggered with respect to one PSSCH occasion in slot #0 on one of CC#1 and CC#2.

In the example of Fig. 14A, the first terminal device 110 may transmit or receive, in the PSFCH occasion in slot #3 on CC#1, HARQ feedback information associated with a PSSCH transmission in slot #0 on CC#1. The first terminal device 110 may transmit or receive, in the PSFCH occasion in slot #5 on CC#2, HARQ feedback information associated with a PSSCH transmission in slot #0 on CC#2.

Similar to the examples of Figs. 10A and 10B, in the example of Fig. 14A, the first terminal device 110 may need to handle the half-duplex issue in slot #3.

As described with reference to Figs. 10A and 10B, in some embodiments, in order to handle the half-duplex issue, the first terminal device 110 may perform PSFCH transmission or PSSCH reception based on priorities of the PSFCH transmission (or reception) and PSSCH reception (or transmission) . Alternatively, the first terminal device 110 may always prioritize the PSFCH transmission or reception. That is, the first terminal device 110 may always perform the PSFCH transmission/reception in slot #3 and drop the PSSCH reception/transmission in slot #3.

In the example of Fig. 14B, a first PSFCH configuration for a first sidelink resource pool on CC#1 is the same as a second PSFCH configuration for a second sidelink resource pool on CC#2. Thus, PSFCH occasions on CC#1 and PSFCH occasions on CC#2 are aligned with respect to one PSSCH occasion in slot #0 on one of CC#1 and CC#2.

In the example of Fig. 14B, the first terminal device 110 may transmit or receive, in the PSFCH occasion in slot #3 on CC#1, first HARQ feedback information associated with a first PSSCH transmission in slot #0 on CC#1. The first terminal device 110 may transmit or receive, in the PSFCH occasion in slot #3 on CC#2, second HARQ feedback information associated with a second PSSCH transmission in slot #0 on CC#2.

In the example of Fig. 14B, there may be issues of UE transmission capability limitation and/or the maximum power limitation across multiple CCs. In order to handle the issues, the first terminal device 110 may drop or adjust a transmission power of one or more PSFCH transmissions with lowest PSFCH priority. For example, a total transmission power on CC#1 and CC#2 exceeds a power threshold and a third priority of the first sidelink HARQ feedback information associated with a PSSCH transmission in slot #0 on CC#1 is higher than a fourth priority of the second sidelink HARQ feedback information associated with a PSSCH transmission in slot #0 on CC#2, the first terminal device 110 may drop or reduce a transmission power of the second sidelink HARQ feedback information.

In some embodiments, the third priority of the sidelink HARQ feedback information may be equal to a priority value indicated by an SCI format 1-A associated with the PSFCH transmission or reception. For example, the second terminal device 120 may perform the first PSSCH transmission to the first terminal device 110 in slot#0 on CC#1 and transmit an SCI format 1-A associated with the first PSSCH transmission. The SCI format 1-A may indicate a priority value. The first terminal device 110 may determine the priority value indicated in the SCI format 1-A as the third priority of the sidelink HARQ feedback information.

In some embodiments, HARQ feedback information associated with at least one PSSCH transmission on a carrier may be transmitted or received in PSFCH occasions on each of carriers. This will be described with reference to Figs. 15A and 15B.

Figs. 15A and 15B illustrate an example of transmission of HARQ feedback information in PSFCH occasions on carriers in accordance with some embodiments of the present disclosure, respectively.

In examples of Figs. 15A and 15B, the first PSFCH configuration for the first sidelink resource pool on CC#1 and the second PSFCH configuration for the second sidelink resource pool on CC#2 are the same as those in the examples of Figs. 14A and 14B, respectively.

The example of Fig. 15A is different from the example of Fig. 14A in that in the example of Fig. 15A, the first terminal device 110 may transmit or receive, in the PSFCH occasion in slot #3 on CC#1, HARQ feedback information associated with a PSSCH transmission in slot #0 on CC#1 and with a PSSCH transmission in slot #0 on CC#2. The first terminal device 110 may transmit or receive, in the PSFCH occasion in slot #5 on CC#2, HARQ feedback information associated with a PSSCH transmission in slot #0 on CC#2 and with a PSSCH transmission in slot #0 on CC#1.

In some embodiments, similar to the example of Fig. 13A, HARQ feedback information to be transmitted in the PSFCH occasion in slot #3 on CC#1 or in the PSFCH occasion in slot #5 on CC#2 may be a joint decoding result of the PSSCH transmission in slot #0 on CC#1 and the PSSCH transmission in slot #0 on CC#2.

Alternatively, in some embodiments, similar to the example of Fig. 13B, HARQ feedback information to be transmitted in the PSFCH occasion in slot #3 on CC#1 or in the PSFCH occasion in slot #5 on CC#2 may comprise a first set of HARQ feedback information associated with the PSSCH transmission in slot #0 on CC#1 and a second set of HARQ feedback information associated with the PSSCH transmission in slot #0 on CC#2.

The example of Fig. 15B is different from the example of Fig. 14B in that in the example of Fig. 15B, the first terminal device 110 may transmit or receive, in the PSFCH occasion in slot #3 on CC#1, HARQ feedback information associated with a PSSCH transmission in slot #0 on CC#1 and with a PSSCH transmission in slot #0 on CC#2. The first terminal device 110 may transmit or receive, in the PSFCH occasion in slot #3 on CC#2, HARQ feedback information associated with a PSSCH transmission in slot #0 on CC#2 and with a PSSCH transmission in slot #0 on CC#1.

In the example of Fig. 15B, the first terminal device 110 may handle the issues of UE transmission capability limitation and/or the maximum power limitation across multiple CCs in a similar way as described with reference to Fig. 14B.

In some embodiments, the present disclosure may be applied to a scenario where a TX UE uses CA operation to transmit sidelink data to an RX UE, and the RX UE transmits to the TX UE HARQ feedback information associated with the sidelink data.

In some embodiments, the present disclosure may be applied to a scenario where different TX UEs use CA operation to transmit sidelink data to an RX UE and the RX UE transmits to the TX UEs HARQ feedback information associated with the sidelink data.

In some embodiments, the present disclosure may be applied to a scenario where a TX UE uses CA operation to transmit sidelink data to different RX UEs.

In some embodiments, the present disclosure may be applied to a scenario where the issues of UE transmission capability limitation and/or the maximum power limitation are caused by different positions of transmission blocks (TBs) and the same feedback occasion for the TBs.

In summary, embodiments of the present disclosure may provide the following solutions.

In a first aspect, a first terminal device comprises a processor configured to cause the first terminal device to: determination whether PSFCH occasions on the carriers are staggered or aligned with respect to one Physical Sidelink Shared Channel (PSSCH) occasion on one of the carriers, sidelink control information (SCI) received from a second terminal device, or a configuration or pre-configuration by higher layer; and transmit or receive sidelink Hybrid Automatic Repeat Request (HARQ) feedback information in the first PSFCH occasion, In some embodiments, the sidelink HARQ feedback information is associated with at least one Physical Sidelink Shared Channel (PSSCH) transmission on at least one of the carriers.

In some embodiments, the first terminal device is further caused to determine whether the PSFCH occasions are staggered or aligned with respect to the one PSSCH occasion based on at least one of the following: PSFCH configurations for sidelink resource pools on the carriers, or time resource allocations for the sidelink resource pools on the carriers.

In some embodiments, the HARQ feedback information is associated with multiple PSSCH transmissions on the carriers.

In some embodiments, the set of carriers at least comprises a first carrier and a second carrier; and the first terminal device is caused to determine that the PSFCH occasions are staggered with respect to the one PSSCH occasion based on determining the following: a first PSFCH configuration for a first sidelink resource pool on the first carrier is different from a second PSFCH configuration for a second sidelink resource pool on the second carrier.

In some embodiments, the first terminal device is caused to determine an ending PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion based on determining the following: the PSFCH occasions are staggered with respect to the one PSSCH occasion.

In some embodiments, the first PSFCH configuration indicates a first period of PSFCH occasions on the first carrier and a first minimum time gap between a PSFCH occasion on the first carrier and a PSSCH occasion on the first carrier; and the second PSFCH configuration indicates a second period of PSFCH occasions on the second carrier and a second minimum time gap between a PSFCH occasion on the second carrier and a PSSCH occasion on the second carrier.

In some embodiments, the first terminal device is caused to determine an ending PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion based on determining the following: the first period is different from the second period.

In some embodiments, the first terminal device is caused to determine a starting PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion based on determining the following: the first period is the same as the second period, and the first minimum time gap is different from the second minimum time gap.

In some embodiments, the first terminal device is caused to determine a starting PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion based on determining the following: the PSFCH occasions are staggered with respect to the one PSSCH occasion.

In some embodiments, the first terminal device is caused to transmit or receive the sidelink HARQ feedback information by: transmitting or receiving the sidelink HARQ feedback information in the first PSFCH occasion in a first slot; and dropping PSSCH reception or transmission in the first slot on the second carrier.

In some embodiments, the first terminal device is caused to drop the PSSCH reception or transmission in the first slot on the second carrier by: based on determining that a first priority of the sidelink HARQ feedback information is higher than a second priority of the PSSCH reception or transmission, dropping the PSSCH reception or transmission.

In some embodiments, the set of carriers at least comprises a first carrier and a second carrier; and the first terminal device is caused to determine that the PSFCH occasions are staggered with respect to the one PSSCH occasion based on determining the following: a first time resource allocation for a first sidelink resource pool on the first carrier is different from a second time resource allocation for a second sidelink resource pool on the second carrier.

In some embodiments, the carrier comprising the first PSFCH occasion is indicated by one of the following: the SCI, or the configuration or pre-configuration by higher layer.

In some embodiments, the first terminal device is further caused to: selecting a first candidate carrier and a second candidate carrier as a first carrier and second carrier in the set of carriers respectively based on determining at least one of the following: a first subcarrier spacing (SCS) for the first candidate carrier is the same as a second SCS for the second candidate carrier, or a first PSFCH configuration for a first sidelink resource pool on the first candidate carrier is the same as a second PSFCH configuration for a second sidelink resource pool on the second candidate carrier.

In some embodiments, the first terminal device is caused to transmit or receive the HARQ feedback information associated with the multiple PSSCH transmissions on the carriers by: determining at least one set of PSFCH resources in the first PSFCH occasion, In some embodiments, the at least one set of PSFCH resources is associated with a PSSCH transmission on the carrier; and transmitting or receiving the HARQ feedback information on at least one PSFCH resource in the at least one set of PSFCH resources.

In some embodiments, the HARQ feedback information comprises a joint decoding result of the multiple PSSCH transmissions on the carriers.

In some embodiments, the HARQ feedback information comprises multiple sets of HARQ feedback information for the multiple PSSCH transmissions on the carriers.

In some embodiments, the first terminal device is further caused to determine a first PSFCH resource in the at least one set of PSFCH resources based on at least one of the following: a physical layer source identity of the second terminal device performing a first PSSCH transmission on the first carrier, a member identity of the first terminal device, an index of the first carrier, the number of physical resource blocks in the set of PSFCH resources, or the number of configured or pre-configured cyclic shift (CS) pairs; and the first terminal device is caused to transmit or receive, on the first PSFCH resource, HARQ feedback information associated with the first PSSCH transmission.

In some embodiments, the first terminal device is caused to transmit the sidelink HARQ feedback information by: transmitting, in the first PSFCH occasion in a first slot on the carrier, first sidelink HARQ feedback information associated with at least one PSSCH transmission on the carrier; and transmitting, in the first PSFCH occasion in the first slot on a second carrier, second sidelink HARQ feedback information associated with at least one PSSCH transmission on the second carrier, In some embodiments, the second carrier is comprised in the set of carriers.

In some embodiments, the first terminal device is caused to transmit the first sidelink HARQ feedback information associated with the at least one PSSCH transmission on the carrier by: based on determining that a total transmission power exceeds a power threshold and a third priority of the first sidelink HARQ feedback information is higher than a fourth priority of the second sidelink HARQ feedback information, dropping or reducing a transmission power of the second sidelink HARQ feedback information.

In a second aspect, a method for sidelink communications comprises: determining, at a first terminal device, a first Physical Sidelink Feedback Channel (PSFCH) occasion on a carrier in a set of carriers for sidelink communications based on at least one of the following: determination whether PSFCH occasions on the carriers are staggered or aligned with respect to one Physical Sidelink Shared Channel (PSSCH) occasion on one of the carriers, sidelink control information (SCI) received from a second terminal device, or a configuration or pre-configuration by higher layer; and transmitting or receiving sidelink Hybrid Automatic Repeat Request (HARQ) feedback information in the first PSFCH occasion, In some embodiments, the sidelink HARQ feedback information is associated with at least one Physical Sidelink Shared Channel (PSSCH) transmission on at least one of the carriers.

In a third aspect, a computer readable medium has instructions stored thereon. The instructions, when executed on at least one processor of a device, cause the device to carry out the method according to the second aspect.

Fig. 16 is a simplified block diagram of a device 1600 that is suitable for implementing some embodiments of the present disclosure. The device 1600 can be considered as a further example embodiment of one of the terminal devices 110, 120 and 130 as shown in Fig. 1. Accordingly, the device 1600 can be implemented at or as at least a part of one of the terminal devices 110, 120 and 130.

As shown, the device 1600 includes a processor 1610, a memory 1620 coupled to the processor 1610, a suitable transmitter (TX) and receiver (RX) 1640 coupled to the processor 1610, and a communication interface coupled to the TX/RX 1640. The memory 1620 stores at least a part of a program 1630. The TX/RX 1640 is for bidirectional communications. The TX/RX 1640 has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements, such as X2 interface for bidirectional communications between gNBs or eNBs, S1 interface for communication between a Mobility Management Entity (MME) /Serving Gateway (S-GW) and the gNB or eNB, Un interface for communication between the gNB or eNB and a relay node (RN) , or Uu interface for communication between the gNB or eNB and a terminal device.

The program 1630 is assumed to include program instructions that, when executed by the associated processor 1610, enable the device 1600 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to Figs. 1 to 15. The embodiments herein may be implemented by computer software executable by the processor 1610 of the device 1600, or by hardware, or by a combination of software and hardware. The processor 1610 may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor 1610 and memory 1620 may form processing means 1650 adapted to implement various embodiments of the present disclosure.

The memory 1620 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 1620 is shown in the device 1600, there may be several physically distinct memory modules in the device 1600. The processor 1610 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 1600 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.

The components included in the apparatuses and/or devices of the present disclosure may be implemented in various manners, including software, hardware, firmware, or any combination thereof. In one embodiment, one or more units may be implemented using software and/or firmware, for example, machine-executable instructions stored on the storage medium. In addition to or instead of machine-executable instructions, parts or all of the units in the apparatuses and/or devices may be implemented, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs) , Application-specific Integrated Circuits (ASICs) , Application-specific Standard Products (ASSPs) , System-on-a-chip systems (SOCs) , Complex Programmable Logic Devices (CPLDs) , and the like.

Claims

A first terminal device, comprising:

a processor configured to cause the first terminal device to:

determine a first Physical Sidelink Feedback Channel (PSFCH) occasion on a carrier in a set of carriers for sidelink communications based on at least one of the following:

determination whether PSFCH occasions on the carriers are staggered or aligned with respect to one Physical Sidelink Shared Channel (PSSCH) occasion on one of the carriers,

sidelink control information (SCI) received from a second terminal device, or

a configuration or pre-configuration by higher layer; and

transmit or receive sidelink Hybrid Automatic Repeat Request (HARQ) feedback information in the first PSFCH occasion, wherein the sidelink HARQ feedback information is associated with at least one Physical Sidelink Shared Channel (PSSCH) transmission on at least one of the carriers.
The first terminal device of claim 1, wherein the first terminal device is further caused to:

determine whether the PSFCH occasions are staggered or aligned with respect to the one PSSCH occasion based on at least one of the following:

PSFCH configurations for sidelink resource pools on the carriers, or

time resource allocations for the sidelink resource pools on the carriers.
The first terminal device of claim 2, wherein the HARQ feedback information is associated with multiple PSSCH transmissions on the carriers.
The first terminal device of claim 3, wherein the set of carriers at least comprises a first carrier and a second carrier; and

the first terminal device is caused to determine that the PSFCH occasions are staggered with respect to the one PSSCH occasion based on determining the following:

a first PSFCH configuration for a first sidelink resource pool on the first carrier is different from a second PSFCH configuration for a second sidelink resource pool on the second carrier.
The first terminal device of claim 4, wherein the first terminal device is caused to determine an ending PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion based on determining the following:

the PSFCH occasions are staggered with respect to the one PSSCH occasion.
The first terminal device of claim 4, wherein:

the first PSFCH configuration indicates a first period of PSFCH occasions on the first carrier and a first minimum time gap between a PSFCH occasion on the first carrier and a PSSCH occasion on the first carrier; and

the second PSFCH configuration indicates a second period of PSFCH occasions on the second carrier and a second minimum time gap between a PSFCH occasion on the second carrier and a PSSCH occasion on the second carrier.
The first terminal device of claim 6, wherein the first terminal device is caused to determine an ending PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion based on determining the following:

the first period is different from the second period.
The first terminal device of claim 6, wherein the first terminal device is caused to determine a starting PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion based on determining the following:

the first period is the same as the second period, and

the first minimum time gap is different from the second minimum time gap.
The first terminal device of claim 4, wherein the first terminal device is caused to determine a starting PSFCH occasion among the first carrier and second carrier as the first PSFCH occasion based on determining the following:

the PSFCH occasions are staggered with respect to the one PSSCH occasion.
The first terminal device of claim 9, wherein the first terminal device is caused to transmit or receive the sidelink HARQ feedback information by:

transmitting or receiving the sidelink HARQ feedback information in the first PSFCH occasion in a first slot; and

dropping PSSCH reception or transmission in the first slot on the second carrier.
The first terminal device of claim 10, wherein the first terminal device is caused to drop the PSSCH reception or transmission in the first slot on the second carrier by:

based on determining that a first priority of the sidelink HARQ feedback information is higher than a second priority of the PSSCH reception or transmission, dropping the PSSCH reception or transmission.
The first terminal device of claim 3, wherein the set of carriers at least comprises a first carrier and a second carrier; and

the first terminal device is caused to determine that the PSFCH occasions are staggered with respect to the one PSSCH occasion based on determining the following:

a first time resource allocation for a first sidelink resource pool on the first carrier is different from a second time resource allocation for a second sidelink resource pool on the second carrier.
The first terminal device of claim 12, wherein the carrier comprising the first PSFCH occasion is indicated by one of the following:

the SCI, or

the configuration or pre-configuration by higher layer.
The first terminal device of claim 1, wherein the first terminal device is further caused to:

selecting a first candidate carrier and a second candidate carrier as a first carrier and second carrier in the set of carriers respectively based on determining at least one of the following:

a first subcarrier spacing (SCS) for the first candidate carrier is the same as a second SCS for the second candidate carrier, or

a first PSFCH configuration for a first sidelink resource pool on the first candidate carrier is the same as a second PSFCH configuration for a second sidelink resource pool on the second candidate carrier.
The first terminal device of claim 3, wherein the first terminal device is caused to transmit or receive the HARQ feedback information associated with the multiple PSSCH transmissions on the carriers by:

determining at least one set of PSFCH resources in the first PSFCH occasion, wherein the at least one set of PSFCH resources is associated with a PSSCH transmission on the carrier; and

transmitting or receiving the HARQ feedback information on at least one PSFCH resource in the at least one set of PSFCH resources.
The first terminal device of claim 15, wherein the HARQ feedback information comprises a joint decoding result of the multiple PSSCH transmissions on the carriers.
The first terminal device of claim 15, wherein the HARQ feedback information comprises multiple sets of HARQ feedback information for the multiple PSSCH transmissions on the carriers.
The first terminal device of claim 17, wherein:

the first terminal device is further caused to determine a first PSFCH resource in the at least one set of PSFCH resources based on at least one of the following:

a physical layer source identity of the second terminal device performing a first PSSCH transmission on the first carrier,

a member identity of the first terminal device,

an index of the first carrier,

the number of physical resource blocks in the set of PSFCH resources, or

the number of configured or pre-configured cyclic shift (CS) pairs; and

the first terminal device is caused to transmit or receive, on the first PSFCH resource, HARQ feedback information associated with the first PSSCH transmission.
The first terminal device of claim 1, wherein the first terminal device is caused to transmit the sidelink HARQ feedback information by:

transmitting, in the first PSFCH occasion in a first slot on the carrier, first sidelink HARQ feedback information associated with at least one PSSCH transmission on the carrier; and

transmitting, in the first PSFCH occasion in the first slot on a second carrier, second sidelink HARQ feedback information associated with at least one PSSCH transmission on the second carrier, wherein the second carrier is comprised in the set of carriers.
The first terminal device of claim 19, wherein the first terminal device is caused to transmit the first sidelink HARQ feedback information associated with the at least one PSSCH transmission on the carrier by:

based on determining that a total transmission power exceeds a power threshold and a third priority of the first sidelink HARQ feedback information is higher than a fourth priority of the second sidelink HARQ feedback information, dropping or reducing a transmission power of the second sidelink HARQ feedback information.