WO2025000530A1

WO2025000530A1 - Carrier aggregation in sidelink communication

Info

Publication number: WO2025000530A1
Application number: PCT/CN2023/105310
Authority: WO
Inventors: Zhaobang MIAO; Gang Wang
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2023-06-30
Filing date: 2023-06-30
Publication date: 2025-01-02
Anticipated expiration: 2025-12-30

Abstract

Embodiments of the present disclosure provide a solution for carrier aggregation (CA) in (SL) communication. In the solution, a first terminal device establishes a connection with a second terminal device capable of carrier aggregation. The first terminal device transmits, to a network device, a request to switch from a first mode to a second mode, wherein the first and second modes are different in sidelink resource allocation.

Description

CARRIER AGGREGATION IN SIDELINK COMMUNICATION

FIELDS

Example embodiments of the present disclosure generally relate to the field of communication techniques and in particular, to devices, methods and computer readable storage medium for carrier aggregation (CA) in sidelink (SL) communication.

BACKGROUND

With the development of communication techniques, a variety of communication networks have been developed or studied. In some wireless communication networks, in addition to communicating with base stations via access links, user equipment (UE) can communicate with other devices using a sidelink (e.g., a communication link between a UE and another UE) as well. Such communication may relate to, for example, vehicle-based communication devices that can communicate from vehicle-to-vehicle (V2V) , vehicle-to-infrastructure (V2I) (e.g., from the vehicle-based communication device to road infrastructure nodes) , vehicle-to-network (V2N) (e.g., from the vehicle-based communication device to one or more network nodes, such as a base station) , a combination thereof and/or with other devices, which can be collectively referred to as vehicle-to-anything (V2X) communications. Further improvements related to CA in the sidelink communication are desired.

SUMMARY

In a first aspect, there is provided a first terminal device comprising: a processor configured to cause the first terminal device to: establish a connection with a second terminal device capable of CA; and transmit, to a network device, a request to switch from a first mode to a second mode, wherein the first and second modes are different in sidelink resource allocation.

In a second aspect, there is provided a network device comprising: a processor configured to cause the network device to: receive, from a first terminal device, a request to switch from a first mode to a second mode, wherein a connection is established between the first terminal device and a second terminal device capable of CA, and the first and second modes are different in sidelink resource allocation.

In a third aspect, there is provided a second terminal device comprising: a processor configured to cause the second terminal device capable of CA to: establish a connection with a first terminal device; and transmit, to the first terminal device, information about CA communication between the first and second terminal devices.

In a fourth aspect, there is provided a first terminal device comprising: a processor configured to cause the first terminal device to: determine an activation status of Packet Data Convergence Protocol (PDCP) duplication for an original packet to be transmitted to at least one second terminal device capable of CA; and based on the activation status, transmit, to the at least one second terminal device, at least one of: PDCP duplication information at least indicating the activation status for the packet, or feedback scheme information indicating a Hybrid Automatic Repeat reQuest (HARQ) feedback scheme.

In a fifth aspect, there is provided a second terminal device comprising: a processor configured to cause the second terminal device to: receive, from a first terminal device performing CA communication with the second terminal device, at least one of: PDCP duplication information at least indicating an activation status of PDCP duplication for an original packet from the first terminal device, or feedback scheme information indicating a HARQ feedback scheme, wherein the HARQ feedback scheme is determined based on the activation status.

In a sixth aspect, there is provided a first terminal device comprising: a processor configured to cause the first terminal device to: obtain compatibility information about carriers for at least one destination identity; in response to an activation of PDCP duplication for an original packet, determine a first carrier configured to a second terminal device based on the compatibility information and a destination identity of the second terminal device, wherein the destination identity of the second terminal device corresponds to at least one of the second terminal device or a service type associated with the second terminal device, and the second terminal device is incapable of CA; and transmit the original packet over the first carrier and a duplicated packet corresponding to the original packet over a second carrier configured for CA communication.

In a seventh aspect, there is provided a network device comprising: a processor configured to cause the network device to: transmit, to a first terminal device capable of CA, compatibility information about carriers for at least one destination identity, wherein the compatibility information indicates at least one of: whether a compatibility is required for each destination identity of at least one destination identity, a carrier for a terminal device incapable of CA, for each destination identity of at least one destination identity, a carrier to be used for original packet transmission, or for each destination identity of at least one destination identity, a carrier to be used for duplicated packet transmission.

In an eighth aspect, there is provided a communication method performed by a first terminal device. The method comprises: establishing a connection with a second terminal device capable of CA; and transmitting, to a network device, a request to switch from a first mode to a second mode, wherein the first and second modes are different in sidelink resource allocation.

In a ninth aspect, there is provided a communication method performed by a network device. The method comprises: receiving, from a first terminal device, a request to switch from a first mode to a second mode, wherein a connection is established between the first terminal device and a second terminal device capable of CA, and the first and second modes are different in sidelink resource allocation.

In a tenth aspect, there is provided a communication method performed by a second terminal device. The method comprises: establishing a connection with a first terminal device; and transmitting, to the first terminal device, information about CA communication between the first and second terminal devices.

In an eleventh aspect, there is provided a communication method performed by a first terminal device. The method comprises: determining an activation status of PDCP duplication for an original packet to be transmitted to at least one second terminal device capable of CA; and based on the activation status, transmitting, to the at least one second terminal device, at least one of: PDCP duplication information at least indicating the activation status for the packet, or feedback scheme information indicating a HARQ feedback scheme.

In a twelfth aspect, there is provided a communication method performed by a second terminal device. The method comprises: receiving, from a first terminal device performing CA communication with the second terminal device, at least one of: Packeting Data Convergence Protocol (PDCP) duplication information at least indicating an activation status of PDCP duplication for an original packet from the first terminal device, or feedback scheme information indicating a HARQ feedback scheme, wherein the HARQ feedback scheme is determined based on the activation status.

In a thirteenth aspect, there is provided a communication method performed by a first terminal device. The method comprises: obtaining compatibility information about carriers for at least one destination identity; in response to an activation of PDCP duplication for an original packet, determining a first carrier configured to a second terminal device based on the compatibility information and a destination identity of the second terminal device, wherein the destination identity of the second terminal device corresponds to at least one of the second terminal device or a service type associated with the second terminal device, and the second terminal device is incapable of CA; and transmitting the original packet over the first carrier and a duplicated packet corresponding to the original packet over a second carrier configured for CA communication.

In a fourteenth aspect, there is provided a communication method performed by a network device. The method comprises: transmitting, to a first terminal device capable of CA, compatibility information about carriers for at least one destination identity, wherein the compatibility information indicates at least one of: whether a compatibility is required for each destination identity of at least one destination identity, a carrier for a terminal device incapable of CA, for each destination identity of at least one destination identity, a carrier to be used for original packet transmission, or for each destination identity of at least one destination identity, a carrier to be used for duplicated packet transmission.

In a fifteenth aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the eighth, ninth, tenth, eleventh, twelfth, thirteenth, or fourteenth aspect.

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 a schematic diagram of an example communication environment in which example embodiments of the present disclosure can be implemented;

FIG. 2 illustrates a signaling flow of mode switch for the first terminal device in accordance with some embodiments of the present disclosure;

FIG. 3 illustrates a signaling flow of indicating PDCP duplication activation from the first terminal device to the second terminal device in accordance with some embodiments of the present disclosure;

FIG. 4 illustrates a signaling flow of PDCP duplication with backward compatibility in accordance with some embodiments of the present disclosure;

FIG. 5 illustrates a flowchart of a method implemented at a first terminal device according to some example embodiments of the present disclosure;

FIG. 6 illustrates a flowchart of a method implemented at a network device according to some example embodiments of the present disclosure;

FIG. 7 illustrates a flowchart of a method implemented at a second terminal device according to some example embodiments of the present disclosure;

FIG. 8 illustrates a flowchart of a method implemented at a first terminal device according to some example embodiments of the present disclosure;

FIG. 9 illustrates a flowchart of a method implemented at a second terminal device according to some example embodiments of the present disclosure;

FIG. 10 illustrates a flowchart of a method implemented at a first terminal device according to some example embodiments of the present disclosure;

FIG. 11 illustrates a flowchart of a method implemented at a network device according to some example embodiments of the present disclosure;

FIG. 12 illustrates a simplified block diagram of an apparatus that is suitable for implementing example 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 limitation as to the scope of the disclosure. Embodiments 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, devices on vehicle for V2X communication where X means pedestrian, vehicle, or infrastructure/network, devices for Integrated Access and Backhaul (IAB) , 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) , 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 (e.g., 450 MHz to 6000 MHz) , FR2 (e.g., 24.25GHz to 52.6GHz) , frequency band larger than 100 GHz 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 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. In some embodiments, the terminal device may be connected with a first network device and a second network device. One of the first network device and the second network device may be a master node and the other one may be a secondary node. The first network device and the second network device may use different radio access technologies (RATs) . In some embodiments, the first network device may be a first RAT device and the second network device may be a second RAT device. In some embodiments, the first RAT device is eNB and the second RAT device is gNB. Information related with different RATs may be transmitted to the terminal device from at least one of the first network device or the second network device. In some embodiments, first information may be transmitted to the terminal device from the first network device and second information may be transmitted to the terminal device from the second network device directly or via the first network device. In some embodiments, information related with configuration for the terminal device configured by the second network device may be transmitted from the second network device via the first network device. Information related with reconfiguration for the terminal device configured by the second network device may be transmitted to the terminal device from the second network device directly or via the first network device.

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. 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.

As used herein, the term “resource, ” “transmission resource, ” “uplink resource, ” or “downlink resource” may refer to any resource for performing a communication, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.

As used herein, the term “Release (Rel) -18 UE” or the like refers to a UE capable of CA, which is also referred to as a CA capable UE. The term “Rel-17 UE” or “Rel-16 UE”refers to a UE incapable of CA, which is also referred to as a CA incapable UE.

As used herein, the term “packet” may refer to a protocol data unit (PDU) , one or more PDUs, a service data unit (SDU) , one or more SDUs, a PDU set, etc. In the following, some embodiments may be described with respect to the PDU or PDU set. However, this is example without limitation.

FIG. 1 illustrates a schematic diagram of an example communication environment 100 in which example embodiments of the present disclosure can be implemented. In the communication environment 100, a plurality of communication devices, including a first terminal device 110, one or more second terminal devices 120-1, …, 120-N (where N is an integer) and a network device 130, can communicate with each other. In the following, the one or more second terminal devices 120-1, …, 120-N may be referred to as the second terminal device 120 individually or second terminal devices 120 collectively. The first terminal device 110 and the second terminal device 120 may be collectively referred to as terminal devices.

In the example of FIG. 1, the first terminal device 110 may be a UE, and the one or more second terminal devices 120 may be UEs. The network device 130 may be a base station serving the UEs, for example, a gNB.

It is to be understood that the number of devices and their connections shown in FIG. 1 are only for the purpose of illustration without suggesting any limitation. The communication environment 100 may include any suitable number of devices configured to implementing example embodiments of the present disclosure.

In the following, for the purpose of illustration, some example embodiments are described with the terminal devices operating as UEs and the network device 130 operating as a base station. However, in some example embodiments, operations described in connection with a terminal device may be implemented at a network device or other device, and operations described in connection with a network device may be implemented at a terminal device or other device.

The communications in the communication environment 100 may conform to any suitable standards including, but not limited to, Global System for Mobile Communications (GSM) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , New Radio (NR) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , GSM EDGE Radio Access Network (GERAN) , Machine Type Communication (MTC) and the like. 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.

In some example embodiments, the network device 130 may communicate with the terminal devices. A link from the network device 130 to a terminal device is referred to as a downlink (DL) , while a link from the terminal device to the network device 120 is referred to as an uplink (UL) . In DL, the network device 130 is a transmitting (TX) device (or a transmitter) and the terminal device is a receiving (RX) device (or a receiver) . In UL, the terminal device is a TX device (or a transmitter) and the network device 120 is a RX device (or a receiver) .

The first network device 110 and the second terminal device 120 can communicate with each other over a sidelink. The communication between terminal devices over the sidelink may be referred to as sidelink communication. There may be different modes for allocating the resource for the sidelink communication, which are referred to as resource allocation (RA) modes.

The RA modes may include a first mode and a second mode which are different from each other in SL resource allocation. In some example embodiments, the first mode may be the mode 1, which is also referred to as a network scheduled resource allocation scheme. In mode 1, the resource for the sidelink communication is scheduled by the network device 130.

As an example but without any limitation, in mode 1, the network device 130 may schedule the terminal device to perform SL transmission, and there may be a dedicated resource pool for resource scheme in mode 1. The network device 130 may perform resource allocation for physical sidelink control channel (PSCCH) and/or physical sidelink shared channel (PSSCH) , and dynamic scheduling and configured grant (which is semi-persistent scheduling (SPS) and shorted as CG) may be supported. There are two types of CG which are type 1 CG and type 2 CG. Dynamic scheduling is based on downlink control information (DCI) . Type 1 CG is based on radio resource control (RRC) configuration. Type 2 CG is based on RRC configuration and activated by DCI. Scheduling more than one resources for a TB for initial transmission and retransmission (s) is supported. The network device 130 does not receive SL signals.

The terminal device in SL communication may transmit sidelink control information (SCI) /data on the scheduled PSCCH/PSSCH resources. The RRC connection (for example, a Uu connection) is made between the terminal device and the network device 130. Dedicated radio network temporary identification (RNTI) for SL scheduling DCI is different from Uu RNTI. SL Acknowledge (ACK) /Negative Acknowledge (NACK) may be forwarded to the network device 130 on physical uplink control channel (PUCCH) and/or physical uplink shared channel (PUSCH) according to configuration.

The second mode may be mode 2, which may be also referred to as an autonomously resource selection scheme. In mode 2, the resource for the sidelink communication is selected by the terminal device. For example, the terminal device may monitor resources in a resource pool configured by the network device 130 and select a resource from the resource pool based on the monitoring.

As an example but without any limitation, in mode 2, the terminal device may select SL resources to perform SL transmission. Mode 2 may include a full sensing scheme, a partial sensing scheme, and a random selection scheme. In the full sensing scheme, initial candidate resources are firstly set as a full set, and then unavailable resources are excluded from the candidate resource set. At last, the final candidate resource set is determined. In some embodiments, inter-UE coordination (IUC) may be used when IUC is (pre-) configured and triggered. If the IUC is triggered, the preferred resource set may be determined for other terminal device’s transmission or the non-preferred resource set from other terminal device (s) may be excluded.

Some mechanism regarding the mode 1 and mode 2 are described. It is to be understood that the mode 1 and mode 2 are given as examples without any limitation, and other RA modes are possible.

In the example environment 100, CA may be adopted for the sidelink communication. The first terminal device 110 may be capable of CA, for example, may be an Rel-18 UE. In some example embodiments, the second terminal devices 120 may be all capable of CA. In some example embodiments, at least one of the second terminal devices 120 may be incapable of CA, for example, may be a CA incapable UE.

CA and its architecture have been studied for SL enhancement. To better understand the solution of the present disclosure, some solutions regarding CA in SL communication (also referred to as SL CA for short) are now described.

It is supported that one independent HARQ entity per carrier used for SL communication in NR and one transport block is generated per carrier. It is supported that each transport block and its retransmissions are mapped to a same single carrier. For groupcast (GC) or broadcast (BC) , as in LTE SL CA, the carrier (s) that can be used for transmitting data are configured by V2X layer for the layer-2 (L2) destination. Backwards compatibility issues are for further study.

Packet duplication for NR SL is performed at the PDCP layer. The duplicated PDCP packet data units (PDUs) of the same PDCP entity are submitted to two different radio link control (RLC) entities and associated to two different SL logical channels respectively. It is agreed that logical channel (LCH) mapping restriction shall be defined such that the duplicated PDCP PDUs of the same PDCP entity are only allowed to be transmitted on different NR SL carriers.

For PDCP duplication in NR SL communication, the hard-coded way for paired SL logical channel ID (LCID) is re-used to identify duplicated SL LCHs (for example, for a unified design for all GC/BC) . For TX carrier (re) selection triggers in NR SL CA, if the resource (re) selection is triggered with the SL process or if there is no SL grant associated with the SL process on any carrier allowed for the STCH as indicated by upper layers (for example, RRC layer and V2X layer) , the triggers for TX carrier (re) selection per SL process in LTE SL CA may be re-used at least for GC/BC.

For link control protocol (LCP) , the LCHs having a priority whose associated channel busy ratio (CBR) threshold for reselection is only allowed to be no lower than the CBR of the carrier when the carrier is selected or reselected. The way to determine the per-carrier CBR at least for GC/BC is for further study.

TX carrier (re) selection in NR SL CA follows LTE CA solution, for example per-carrier-per-priority CBR threshold for carrier (re) selection and per-carrier-per-priority CBR threshold for carrier keeping are defined. Final carrier selection is made based on the lowest CBR value across carriers and the priority is the LCH priority.

Based on an observation that V2X layer can be provisioned with service to frequency mapping for unicast, it is assumed that it is applicable to PC5 unicast SL CA after link has been established. V2X layer is only provisioned with a mapping between a service identifier and an initial L2 address used for unicast, however the service identifier is invisible to Access Stratum (AS) -layer, and the initial L2 identity (ID) will only be used in Direct Communicate Request (DCR) message and be replaced by a chosen L2 ID in PC5-signalling (PC5-S) link establishment procedure. Then, after L2 ID changes, whether/how AS-layer of UE can obtain the mapping between L2 ID and frequencies is to be determined. PC5 unicast allows UEs to add/modify/remove V2X services/PC5 quality of service (QoS) flows to the same L2 ID pair. Then, given service information is invisible to AS layer, how can the UE ensure the modified V2X services to be transmitted only on the corresponding frequencies in the V2X layer needs to be specified.

Some cases on backward compatibility issue in SL CA for GC/BC are considered, for example a case that a V2X service needs to be mapped into multiple carriers while there is at least one legacy UE to receive this V2X service. The solution of per carrier CBR is same as LTE V2X CA is applied. Regarding TX carrier (re) selection triggers, LCP impact, and CBR- based carrier reselection/keeping for uplink control (UC) , solutions for GC/BC may be also applicable for UC. TX carrier reselection is done among the carriers that peer UE also supports. Regarding LCID to identify duplicated SL LCHs, solutions for GC/BC may be also applicable for UC. Regarding the criterion for packet duplication, SLRB configures whether PDCP duplication is used or not. Regarding discontinuous transmission (DTX) based SL radio link failure (RLF) in SL CA, the counting is calculated per carrier and legacy SL RLF is not declared when the counting is reached to sl-MaxnumConsecutiveDTX for carrier (s) and the UE has other available SL carrier (s) for SL CA. Regarding PDCP duplication/SL CA for SL SRB, it is assumed that SL CA/PDCP duplication is applied to PC5-RRC after SL link is established.

Some example solutions on SL CA are described above. However, some issues remain pending. For example, only mode 2 RA may be supported for SL CA. In this case, there would be an issue that the UE is currently communicating with a CA incapable UE A in mode 1 and establishes another unicast link with a UE-B, which is a CA capable UE. Then, the UE may need switch to mode 2 RA to continue the unicast communication with the UE-B.

To this end, some embodiments of the present disclosure provide a solution for RA mode switch for CA in SL communication. According to these embodiments, a first terminal device (for example, a CA capable UE, which was previously configured with mode 1 RA) obtains a connection request from a second terminal device which is CA capable. Thereafter, in order to perform CA, the first terminal device may need to turn into mode 2 RA. Thus, the first terminal device may need to request a configuration of a resource pool from the network device.

Reference is now made to FIG. 2, which illustrates a signaling flow 200 of mode switch in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 200 herein will be discussed with reference to FIG. 1, for example, by using the first terminal device 110, the second terminal device 120 and the network device 130. The signaling flow 200 involves the first terminal device 110 and the second terminal device 120 which are going to perform an SL communication (also referred to as “SL transmission” in embodiments of the present disclosure) . In such embodiments, the first terminal device 110 and the second terminal device 120 may be capable of CA, for example, may be Rel-18 UEs.

As shown in FIG. 2, a connection between the first terminal device 110 and the second terminal device 120 may be established (210) . To establish the connection, any suitable information may be exchanged therebetween. For example, the first terminal device 110 and the second terminal device 120 may exchange a “UECapabilityInformationSidelink” message which indicates capabilities of a terminal device in sidelink communication. The connection may be a PC5-Sconnection.

In some example embodiments, after the connection is established or during the connection establishment, the first terminal device 110 and the second terminal device 120 may exchange their configurations related to CA. As shown, the second terminal device 120 may transmit (220) information about CA communication between the first terminal device 110 and the second terminal device 120 to the first terminal device 110. Accordingly, the first terminal device 110 may receive (230) information about CA communication between the first terminal device 110 and the second terminal device 120 from the first terminal device 110.

Before the connection is established (210) , the first terminal device 110 may be previously configured with a first mode for sidelink RA, which does not support CA. For example, the first terminal device 110 may be previously configured with the mode 1. To perform CA in communication with the second terminal device 120, the first terminal device 110 may transmit (240) , to a network device 130, a request to switch from the first mode to a second mode. The second mode is different from the first mode in SL RA and can support CA. The request is also referred to as a switch request hereafter.

The switch request may be transmitted in response to any suitable condition. In some example embodiments, the first terminal device 110 may transmit the switch request to the network device 130 in response to that the first terminal device 110 is configured with the first mode. For example, the first terminal device 110 may transmit the switch request towards the network device 130, if the first terminal device 110 is configured with the network scheduled resource allocation scheme or, in other word, mode 1.

Alternatively, or in addition, in some example embodiments, the first terminal device 110 may transmit the switch request to the network device 130 in response to that the first terminal device 110 is configured with the second mode without a CA configuration. For example, the first terminal device 110 may transmit the switch request towards the network device 130, if the first terminal device 110 is configured with autonomously resource selection scheme but configured with non-CA configuration, and the first terminal device 110 is in an RRC_CONNECTED state.

Alternatively, or in addition, in some example embodiments, the first terminal device 110 may transmit the switch request to the network device 130 in response to that the connection with the second terminal device 120 is established and capability information from the second terminal device 120 indicates a CA capability of the second terminal device 120. For example, the first terminal device 110 may transmit the switch request towards the network device 130, if the first terminal device 110 has established the PC5-Sconnection with the second terminal device 120 (which may be a peer UE for example) and the second terminal device 120 is capable of CA as indicated in the capability information transmitted in the UEcapabilityInformationSidelink message.

Alternatively, or in addition, in some example embodiments, the first terminal device 110 may transmit the switch request to the network device 130 in response to that the connection is established, capability information from the second terminal device 120 indicates a CA capability of the second terminal device 120, and a decision of the first terminal device 110 to perform CA communication with the second terminal device 120. For example, the first terminal device 110 may transmit the switch request towards the network device 130, if the first terminal device 110 has established the PC5-Sconnection with the second terminal device 120 (which may be a peer UE for example) and the second terminal device 120 is capable of CA as indicated in the capability information transmitted in the UEcapabilityInformationSidelink message, and the first terminal device 110 decides to perform CA communication with the second terminal device 120.

Alternatively, or in addition, in some example embodiments, the first terminal device 110 may transmit the switch request to the network device 130 in response to that the connection with the second terminal device 120 is established. For example, the first terminal device 110 may transmit the switch request towards the network device 130 once the PC5-Sconnection is established with the second terminal device 120 (which may be a peer UE for example) . The first terminal device 110 may recognize that the service corresponding to the communication with the second terminal device 120 is a CA service via ID information including not limited to service ID, Destination Layer 2 ID, etc.

Alternatively, or in addition, in some example embodiments, the first terminal device 110 may transmit the switch request to the network device 130 in response to that the connection with the second terminal device 120 is established, capability information from the second terminal device 120 indicates a CA capability of the second terminal device 120, and a CA configuration for the second terminal device 120 is received from the second terminal device 120. For example, the first terminal device 110 may transmit the switch request towards the network device 130, if the first terminal device 110 has established the PC5-Sconnection with the second terminal device 120 (which is a peer UE for example) and the second terminal device 120 is capable of CA as indicated in the capability information transmitted in the UEcapabilityInformationSidelink message, and the second terminal device 120 has decided to perform CA communication with the first terminal device 110 and send the CA related configuration via PC5-RRC message towards the first terminal device 110. The UECapabilityInformationSidelink message may be used to transfer UE radio access capabilities.

Some example trigger conditions for transmitting the switch request are described. In an example without any limitation, the UE shall:

2> if configured by upper layers to perform NR sidelink reception on the frequency included in sl-FreqInfoList in SIB12 of the Primary Cell (PCell) and if sl-DRX-ConfigCommonGC-BC is included in SIB12-IEs:

3> if the UE received a sidelink DRX configuration in the RRCReconfigurationSidelink message for NR sidelink unicast reception from the associated peer UE and the UE accepted the sidelink DRX configuration:

4> if the UE did not transmit a SidelinkUEInformationNR message since last entering RRC_CONNECTED state; or

4> if since the last time the UE transmitted a SidelinkUEInformationNR message the UE connected to a PCell not providing SIB12 including sl-DRX-ConfigCommonGC-BC; or

4> if the last transmission of the SidelinkUEInformationNR message did not include sl-RxDRX-ReportList; or if the information carried by sl-RxDRX-ReportList has changed since the last transmission of the SidelinkUEInformationNR message:

5> initiate transmission of the SidelinkUEInformationNR message to report the sidelink DRX configuration;

3> else:

4> if the last transmission of the SidelinkUEInformationNR message included sl-RxDRX-ReportList:

5> initiate transmission of the SidelinkUEInformationNR message to indicate the sidelink DRX configuration is no longer used;

3> if the UE is performing NR sidelink groupcast or broadcast reception and is interested in a service that sidelink DRX is applied:

4> if the last transmission of the SidelinkUEInformationNR message did not include sl-RxInterestedGC-BC-DestList; or if the information carried by sl-RxInterestedGC-BC-DestList has changed since the last transmission of the SidelinkUEInformationNR message:

5> initiate transmission of the SidelinkUEInformationNR message to report the Destination Layer-2 ID and QoS profile (s) associated with the service (s) ;

3> else:

4> if the UE is configured with network scheduled resource allocation scheme; or

4> The UE is configured with autonomously resource selection scheme but configured with non-CA configuration:

5> if the UE has established the PC5-S/PC5-RRC connection with a peer UE and the peer UE is a CA capable UE as indicated in the capability information transmitted UEcapabilityInformationSidelink message; or

5> if the UE has established the PC5-Sconnection with a peer UE and the peer UE is a CA capable UE as indicated in the capability information transmitted in the UEcapabilityInformationSidelink message, and the UE decide the perform CA communication with the peer UE

5> if The UE has established the PC5-Sconnection with a peer UE and the peer UE is a CA capable UE as indicated in the capability information transmitted in the UEcapabilityInformationSidelink message, and the peer UE has decided to perform CA communication with the UE and send the CA related configuration via PC5-RRC message towards the UE

6>initiate transmission of the SidelinkUEInformationNR message to report the Mode Switch Request Indication associated to the specific Destination Layer-2 ID.

where the sl-FreqInfoList field may indicate the NR sidelink communication/discovery configuration on some carrier frequency (ies) ; the sl-DRX-ConfigCommonGC-BC field may indicate the sidelink DRX configuration for groupcast and broadcast communication and this field, if present, also may indicate the gNB is capable of sidelink DRX; the RRCReconfigurationSidelink message may be the command to AS configuration of the PC5 RRC connection; the SidelinkUEinformationNR message is used for the indication of NR sidelink UE information to the network; the sl-RxDRX-ReportList field may indicate the accepted DRX configuration that is received from the peer UE and reported to the network for NR sidelink unicast communication; the sl-RxInterestedGC-BC-DestList field may indicate the reported Quality of service (QoS) profile and associated destination for which UE is interested in reception to the network for NR sidelink groupcast and broadcast communication, or for NR sidelink discovery or proximity services (ProSe) Direct Link Establishment Request, or for Direct Link Establishment Request.

The switch request may include any suitable information to request a CA related configuration. In some example embodiments, the switch request may include an indication to switch from the first mode to the second mode. In other words, a mode switch request indication may be carried within the switch request. For example, the switch request indication may be indicated in an SL-modeSwitchRequest field within the switch request.

Alternatively, or in addition, in some example embodiments, the switch request may include information about one or more frequencies preferred by the first terminal device 110. In other words, an interested frequency list of the first terminal device 110 may be carried within the switch request. For example, the interested frequency list of the first terminal device 110 may be indicated in an SL-InterestedFreqList field within the switch request.

Alternatively, or in addition, in some example embodiments, the switch request may include information about one or more frequencies preferred by the second terminal device 120. In other words, an interested frequency list of the second terminal device 120 may be carried within the switch request. For example, the interested frequency list of the second terminal device 120 may be indicated in an SL-PeerUEInterestedFreqList field within the switch request.

Alternatively, or in addition, in some example embodiments, the switch request may include information about one or more frequencies supported by the second terminal device 120. In other words, frequency information supported by a peer UE may be carried within the switch request.

Alternatively, or in addition, in some example embodiments, the switch request may include a destination identity, which corresponds to the second terminal device 120 and/or a service type associated with the second terminal device 120. For example, the destination identity may be a Destination Layer 2 ID for the communication between the first terminal device 110 and the second terminal device 120. For example, the destination identity may be indicated in an SL-DestinationIdentity field within the switch request.

In some example embodiments, the switch request may be included in an existing message, for example, the SidelinkUEInforamtionNR message. To this end, the SidelinkUEInforamtionNR message may include the following fields as shown in the Table 1.

Table 1 Fields and descriptions thereof

Alternatively, in some example embodiments, the switch request may be a newly defined message. The newly defined message may include one or more of the fields as shown in Table 1.

In some embodiments, the first terminal device 110 may fail in obtaining a configuration associated with CA communication with the second terminal device 120, which is also referred to as a CA configuration. In an example, the failure of the first terminal device 110 in obtaining the CA configuration may be a failure in switching from the first mode to the second mode. For example, the first terminal device 110 may fail to get the mode switch reconfiguration from the network device 130. Alternatively, or in addition, the failure of the first terminal device 110 in obtaining the CA configuration may be a failure in obtaining the CA configuration from the network device 130. In other words, the first terminal device 110 may fail to get the related CA configuration from the network device 130.

In some example embodiments, if the first terminal device 110 fails in obtaining the CA configuration, the first terminal device 110 may transmit, to the second terminal device 120, a first message for requesting a non-CA communication with the second terminal device 120. Accordingly, the second terminal device 120 may receive the first message from the first terminal device 110. The first message may indicate the failure of the first terminal device 110 in obtaining the CA configuration. For example, if the first terminal device 110 fails to get the mode switch reconfiguration from the network device 130, or if the first terminal device 110 fails to get related CA configuration from the network device 130, the first terminal device 110 may try to fallback to a non-CA configuration with the second terminal device 120, which may be its peer UE. To this end, the first terminal device 110 may send a fallback request message towards the second terminal device 120. The fallback request message may carry a cause value which may represent a mode switch failure or a CA configuration failure.

Alternatively, or in addition, in some example embodiments, if the first terminal device 110 fails in obtaining the CA configuration, the first terminal device 110 may transmit, to the second terminal device 120, a second message to release a link between the first terminal device 110 and the second terminal device 120. Accordingly, the second terminal device 120 may receive the second message from the first terminal device 110. The second message may indicate the failure in obtaining the CA configuration. For example, if the first terminal device 110 fails to get the mode switch reconfiguration from the network device 130, or if the first terminal device 110 fails to get related CA configuration from the network device 130, the first terminal device 110 may send PC5-RRC link release request message towards the second terminal device 120, which may be its peer UE. The link release request message may carry a cause value which may represent a mode switch failure or a CA configuration failure.

In some embodiments, if the first terminal device 110 succeeds in obtaining a configuration associated with CA communication with the second terminal device 120, the first terminal device 110 may clear an SL grant in presence of the SL grant assigned by the network device 130. For example, if the first terminal device 110 successfully gets the mode switch reconfiguration and the related CA configuration from the network device 130, and if the first terminal device 110 has an unused SL grant assigned by the network device 130 for a transmission to other destination ID, the first terminal device 110 may clear the SL grant.

In some embodiments, in presence of the SL grant, the first terminal device 110 may transmit an indication to release the SL grant to the network device 130. Accordingly, the network device 130 may receive the indication from the first terminal device 110. For example, the first terminal device 110 may send buffer status report (BSR) cancelled UL medium access control (MAC) control element (CE) towards the network device 130 to cancel an unused or un-scheduled SL grant, and the network may receive the BSR cancelled UL MAC CE from the first terminal device 110.

Alternatively, or in addition, in some embodiments, if the first terminal device 110 succeed in obtaining a configuration associated with CA communication with the second terminal device 120, and if a sensing result on a resource pool configured by the network device 130 is absent, the first terminal device 110 may randomly select a resource for communicating with the second terminal device 120 from a further resource pool different from the configured resource pool. For example, if the first terminal device 110 successfully gets the mode switch reconfiguration and the related CA configuration from the network device 130, and if the first terminal device 110 does not have sensing result on the configured resource pool, the first terminal device 110 may use a randomly selected resource in an exceptional resource pool.

Example embodiments regarding the mode switch are described above. Trigger conditions for requesting the mode switch are specified and/or the content of the mode switch are specified. In this way, the mode switch is enabled and thus robust of the sidelink communication can be improved.

Another issue remains to be solved for the CA in sidelink communication. For SL CA, PDCP duplication can be activated via SLRB configuration, however it is also necessary for the Rx UE to know when the Tx UE activates the PDCP duplication for the purpose of HARQ feedback. Therefore, whether the PDCP duplication is activated or not need to be indicated by the Tx UE to the Rx UE. Some embodiments of the present disclosure propose a solution for indicating PDCP activation. According to these embodiments, the TX terminal device may determine an activation status of PDCP duplication for an original packet to be transmitted to at least one RX terminal device. Based on the activation status, the TX terminal device may transmit PDCP duplication information and/or feedback scheme information to the at least one RX terminal device.

Reference is then made to FIG. 3, which illustrates a signaling flow 300 of indicating PDCP duplication activation in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 300 herein will be discussed with reference to FIG. 1, for example, by using the first terminal device 110, and the second terminal device 120. The second terminal device 120 may perform CA communication with the first terminal device 110. Although one second terminal device is shown in FIG. 3, the signaling flow 300 may be applicable for more than one second terminal device. In the case of one second terminal device, the transmission from the first terminal device 110 to the one second terminal device may be unicast. In the case of more than one second terminal device, the transmission from the first terminal device 110 to the more than one second terminal device may be groupcast.

As shown in FIG. 3, the first terminal device 110 may determine (310) an activation status of PDCP duplication for an original packet to be transmitted to at least one second terminal device 120. For example, the original packet may be an original PDU.

In some example embodiments, based on the activation status, the first terminal device 110 may transmit (320) PDCP duplication information at least indicating the activation status for the original packet to the second terminal device 120. Accordingly, the second terminal device 120 may receive (330) the PDCP duplication information from the first terminal device 110.

In some example embodiments, the PDCP duplication information may be transmitted or indicated for each original packet. For example, if the first terminal device 110 is configured as PDCP duplication activated for certain DRBs, it should perform PDCP duplication for such DRB transmission. In order to allow the second terminal device 120 to be aware of whether certain reception is PDCP duplication or not, the first terminal device 110 may include PDCP duplication status information (for example, at least a PDCP duplication status field and/or an indication of PDCP duplication status) for each PDU.

In an example, the PDCP duplication information may be included in a PDCP header of the original packet. For example, the PDCP duplication information for an original PDU may be included in a PDCP header of the original PDU. Alternatively, or in addition, the PDCP duplication information may be included in a radio link control (RLC) header of the original packet. For example, the PDCP duplication information for an original PDU may be included in an RLC header of the original PDU. Alternatively, or in addition, the PDCP duplication information may be included in a MAC header of the original packet. For example, the PDCP duplication information for an original PDU may be included in a MAC header of the original PDU.

In an example, the MAC subheader may include the following fields:

- V: The MAC PDU format version number field indicates which version of the SL-SCH subheader is used. In this version of the specification, the V field is set to 0. The size of the V field is 4 bits;

- SRC: The SRC field carries the 16 most significant bits of the Source Layer-2 ID set to the identifier provided by upper layers. The length of the field is 16 bits;

- DST: The DST field carries the 8 most significant bits of the Destination Layer-2 ID set to the identifier provided by upper layers. The length of the field is 8 bits;

- LCID: The Logical Channel ID field identifies the logical channel instance of the corresponding MAC SDU or the type of the corresponding MAC CE within the scope of one Source Layer-2 ID and Destination Layer-2 ID pair or padding for SL-SCH. There is one LCID field per MAC subheader except for SL-SCH subheader. The size of the LCID field is 6 bits;

- L: The Length field indicates the length of the corresponding MAC SDU or variable-sized MAC CE in bytes. There is one L field per MAC subheader except for SL-SCH subheader and subheaders corresponding to the fixed-sized MAC CE or padding. The size of the L field is indicated by the F field;

- F: The Format field indicates the size of the Length field. There is one F field per MAC subheader except for SL-SCH subheader and subheaders corresponding to the fixed-sized MAC CE or padding. The size of the F field is 1 bit. The value 0 indicates 8 bits of the Length field. The value 1 indicates 16 bits of the Length field;

- DUPLICATE: The Duplication status field indicate whether this MAC PDU has been duplicated in PDCP layer. The value 0 indicate PDCP duplication is not activated and value 1 indicate PDCP duplication is activated;

- CARRIER: The Carrier information field indicate which carrier is used to carry the duplicated MAC PDU. When DUPLICATED value is indicated as 1, the value of this field indicate the carrier index refers to the configured order as in sl-TxResourceReqList.

- R: Reserved bit, set to 0.

In some example embodiments, if the PDCP duplication is activated for the original packet, the PDCP duplication information may indicate a carrier for transmitting the original packet, which is also referred to as an original carrier. In other words, the PDCP duplication information may include information about the original carrier. For example, the information about the original carrier may be carried within the header of a PDU, such as a MAC header of the PDU.

Alternatively, or in addition, the PDCP duplication information may indicate a carrier for transmitting a duplicated packet corresponding to the original packet, which is also referred to as a duplicated carrier. In other words, the PDCP duplication information may include information about the duplicated carrier. For example, the information about the duplicated carrier may be carried within the header of a PDU, such as a MAC header of the PDU.

Alternatively, in some example embodiments, the PDCP duplication information may be transmitted before the original packet is transmitted. This may mean that the PDCP duplication information is a prior indication. In such embodiments, the second terminal device 120 may apply the PDCP duplication information to subsequently received packets. For example, the TX terminal device can indicate whether to activate or deactivate PDCP duplication by prior indication. Specifically, the TX terminal device can send the indication towards the RX terminal device with an explicitly indication on PDCP duplication activation/deactivation for the following transmissions.

In such embodiments, the PDCP duplication information may be included in any suitable signaling. In an example, the PDCP duplication information may be included in SCI transmitted to the second terminal device 120 before the original packet. For example, the SCI may be of any suitable format, such as SCI 1A format, SCI 2A format, SCI 2B format and/or SCI 2C format. Alternatively, or in addition, the PDCP duplication information may be included in a MAC CE transmitted to the second terminal device 120 before the original packet. For example, the PDCP duplication information may be carried in the SL MAC CE. Alternatively, or in addition, the PDCP duplication information may be included in an RRC message transmitted to the second terminal device 120 before the original packet. For example, the PDCP duplication information may be carried in a PC5-RRC message.

In some example embodiments, if the PDCP duplication is activated for the original packet, the information about the original carrier and/or the information about the duplicated carrier may be carried in the above mentioned signaling, for example, the SCI, the MAC CE or the RRC message.

Continuing with the signaling flow 300, alternatively, or in addition, in some embodiments, the first terminal device 110 may transmit (340) feedback scheme information indicating an HARQ feedback scheme to the second terminal device 120. Accordingly, the second terminal device 120 may receive (350) the feedback scheme information from the first terminal device 110. The HARQ feedback scheme is determined based on the activation status. For example, according to the HARQ feedback scheme, ACK/NACK feedback option or NACK only feedback option may be used. For example, if the TX terminal device is configured as PDCP duplication activated for certain DRBs, it should perform PDCP duplication for such DRB transmission. In order to correct understand the RX terminal device’s HARQ feedback, the TX terminal device should indicate the HARQ feedback option, for example that only ACK/NACK feedback option or NACK only feedback option can be used.

In some embodiments, if the PDCP duplication is activated for the original packet, the PDCP duplication information may indicate the NACK only feedback scheme to be used for the original packet. In such embodiments, only if the second terminal device 120 fails in receiving the packet, the second terminal device 120 may transmit a NACK indication to the first terminal device 110.

In such embodiments, the feedback scheme information may be included in any suitable signaling. In an example, the feedback scheme information may be included in SCI transmitted to the second terminal device 120 before the original packet. For example, the SCI may be of any suitable format, such as SCI 1A format, SCI 2A format, SCI 2B format and/or SCI 2C format. Alternatively, or in addition, the feedback scheme information may be included in a MAC CE transmitted to the second terminal device 120 before the original packet. For example, the feedback scheme information may be carried in the SL MAC CE. Alternatively, or in addition, the feedback scheme information may be included in an RRC message transmitted to the second terminal device 120 before the original packet. For example, the feedback scheme information may be carried in a PC5-RRC message.

In an example, in order to correctly understand the HARQ feedback of the second terminal device 120, the first terminal device 110 may indicate the HARQ feedback option towards the second terminal device 120 via at least one of the SCI, the SL MAC CE or the PC5-RRC message.

Example embodiments regarding the indication of the PDCP duplication are described above. In this way, the TX terminal device can correctly understand the HARQ feedback from the one or more RX terminal device. The correct understanding of the HARQ feedback can improve reliability of the sidelink communication between the terminal devices.

A further issue remains to be solved for the CA in sidelink communication. For sidelink CA, there would be a possible scenario that a CA capable UE needs to both ensure the backward compatible communication with a CA incapable UE and ensure reliability requirement with other CA capable UEs.

For example, if a TX UE needs to perform PDCP duplication for certain service to ensure transmission reliability, it needs to ensure RX UE’s (for example, a Rel-17 UE’s) correct reception for such service. Therefore, the TX UE needs to perform original service transmission on the configured carrier for CA incapable UEs while duplicated transmission on the configured CA carriers.

Some embodiments of the present disclosure propose a backward compatibility scheme for PDCP duplication. According to such embodiments, the TX terminal device may know the configured carrier for CA incapable RX terminal devices based on compatibility information from a network device or generated by an upper layer.

Reference is then made to FIG. 4, which illustrates a signaling flow 400 of PDCP duplication with backward compatibility in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 400 herein will be discussed with reference to FIG. 1. The signaling flow 400 involves the first terminal device 110, and the second terminal devices 120-1, ……, 120-N.

Transmission from the first terminal device 110 to the second terminal devices 120 may be groupcast. In such embodiments, the first terminal device 110 may be capable of CA, for example, may be a Rel-18 UE. At least one of the second terminal devices 120 may be capable of CA while at least another one of the second terminal devices 120 may be incapable of CA. In other words, the first terminal device 110 needs to perform sidelink communication with both CA capable terminal devices and CA incapable terminal devices. In the following, some embodiments may be described by taking the second terminal device 120-1 as a CA capable terminal device and the second terminal device 120-N as a CA incapable terminal device as an example. However, it is to be understood that this is merely an example without any limitation.

The first terminal device 110 may obtain compatibility information about carriers for at least one destination identity, for example, at least one Destination Layer-2 ID. The compatibility information may be used to indicate the carriers for CA capable terminal devices and CA incapable terminal devices.

In some example embodiments, the first terminal device 110 may obtain the compatibility information from the network device 130. As shown in FIG. 4, the network device 130 may transmit (410) the compatibility information to the first terminal device 110. Accordingly, the first terminal device 110 may receive (420) the compatibility information from the network device 130.

The network device 130 may configure any suitable compatibility information to the first terminal device 110. In some example embodiments, the compatibility information may indicate whether a compatibility is required for each destination ID of at least one destination ID. For example, the network device 130 may configure backward compatibility necessity for each destination ID and transmit the configuration to the first terminal device 110. The backward compatibility necessity may be a Boolean type to indicate, for each destination ID (for example, destination ID corresponding to a service) , whether the first terminal device 110 has necessity to allow reception by the second terminal device 120-N (for example, a Rel-17 UE) , which is incapable of CA.

Alternatively, or in addition, in some example embodiments, the compatibility information may indicate a carrier for a terminal device incapable of CA. For example, the network device 130 may configure carrier information to indicate which carrier can be used for CA incapable terminal device, for example for Rel-17 UE.

Alternatively, or in addition, in some example embodiments, the compatibility information may indicate a carrier (which is referred to as an original transmitted carrier) to be used for original packet transmission for each destination ID of the at least one destination ID. For example, the network device 130 may configure an original transmitted carrier for each destination ID to indicate if PDCP duplication for the destination ID is to be activated, then which carrier may be used for original packet transmission, that is, which carrier may be used to transmit the original packet.

Alternatively, or in addition, in some example embodiments, the compatibility information may indicate a carrier (which is referred to as duplicated transmitted carrier) to be used for duplicated packet transmission for each destination ID of at least one destination ID. For example, the network device 130 may configure a duplicated transmitted carrier for each destination ID to indicate if PDCP duplication for the destination ID is to be activated, then which carrier may be used for the duplicated packet transmission, that is, which carrier may be used to transmit the duplicated packet.

In some example embodiments, as shown in FIG. 4, the compatibility information may be generated (430) by an upper layer, for example, the V2X layer. For example, the compatibility information may be a profile generated by the upper layer of the first terminal device 110 for the destination ID of the second terminal device 120-N, which is incapable of CA. The destination ID of the second terminal device 120-N, for example a Destination Layer-2 ID, corresponds to the second terminal device 120-N and/or a service type associated with the second terminal device 120-N. In some cases, for each destination ID, the upper layer may provide a configuration with a TX profile, and the compatibility information may be included in the TX profile.

In some example embodiments, the compatibility information generated by the upper layer may indicate whether a compatibility is required for the destination ID of the second terminal device 120-N. For example, the TX profile for the destination ID may indicate backward compatibility necessity. The backward compatibility necessity may indicate, for the destination ID, whether the first terminal device 110 has necessity to allow reception by the second terminal device 120-N.

Alternatively, or in addition, in some example embodiments, the compatibility information generated by the upper layer may indicate a mapping between a carrier for using by a terminal device incapable of CA and the destination ID of the second terminal device 120. For example, the TX profile for the destination ID may include a mapping between a carrier for using by a CA incapable terminal device (for example, a Rel-17 UE) and the destination ID.

Alternatively, or in addition, in some example embodiments, the compatibility information generated by the upper layer may indicate a mapping between one or more carriers for using by a terminal device capable of CA and the destination ID of the second terminal device 120. For example, the TX profile for the destination ID may include a mapping between a carrier list for the CA capable terminal device (for example, a Rel-18 UE) and the destination ID.

Alternatively, or in addition, in some example embodiments, the compatibility information generated by the upper layer may indicate a mapping between a carrier for original packet transmission and the destination ID of the second terminal device 120. For example, the TX profile for the destination ID may include a mapping between one re more original transmitted carriers and the destination ID.

Alternatively, or in addition, in some example embodiments, the compatibility information generated by the upper layer may indicate a mapping between a carrier for duplicated packet transmission and the destination ID of the second terminal device 120. For example, the TX profile for the destination ID may include a mapping between one or more duplicated transmitted carriers and the destination ID.

If the PDCP duplication is activated for an original packet, the first terminal device 110 may determine (440) a first carrier configured to the second terminal device 120-N based on the compatibility information and a destination ID of the second terminal device 120-N. The first terminal device 110 may transmit (450) the original packet over the first carrier and a duplicated packet corresponding to the original packet over a second carrier configured for CA communication.

According to these embodiments, if a TX terminal device performs CA communication with a RX terminal device incapable of CA and a RX terminal device capable of CA, the TX terminal device would know over which carrier to transmit the original packet and over which carrier to transmit the duplicated packet. In this way, backward compatibility for terminal devices incapable of CA can be achieved and thus reliability of sidelink communication with the terminal devices incapable of CA can be ensured.

Example methods

FIG. 5 illustrates a flowchart of a communication method 500 implemented at a first terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 500 will be described from the perspective of the first terminal device 110 in FIG. 1.

At block 510, the first terminal device 110 establishes a connection with a second terminal device 120 capable of CA.

At block 520, the first terminal device 110 transmits, to a network device 130, a request to switch from a first mode to a second mode. The first and second modes are different in sidelink resource allocation.

In some example embodiments, the first terminal device 110 may transmit the request to the network device 130 in response to at least one of: that the first terminal device 110 is configured with the first mode, that the first terminal device 110 is configured with the second mode without a CA configuration, that the connection is established and capability information from the second terminal device 120 indicates a CA capability of the second terminal device 120, that the connection is established, capability information from the second terminal device 120 indicates a CA capability of the second terminal device 120, and a decision of the first terminal device 110 to perform CA communication with the second terminal device 120, that the connection is established, or that the connection is established, capability information from the second terminal device 120 indicates a CA capability of the second terminal device 120, and a CA configuration for the second terminal device 120 is received from the second terminal device 120.

In some example embodiments, the request may comprise at least one of: an indication to switch from the first mode to the second mode, information about one or more frequencies preferred by the first terminal device 110, information about one or more frequencies preferred by the second terminal device 120, information about one or more frequencies supported by the second terminal device 120, or a destination identity corresponding to at least one of the second terminal device 120 or a service type associated with the second terminal device 120.

In some example embodiments, in response to a failure in obtaining a configuration associated with CA communication with the second terminal device 120, the first terminal device 110 may transmit, to the second terminal device 120, a first message for requesting a non-CA communication with the second terminal device 120, the first message indicating the failure, or transmit, to the second terminal device 120, a second message to release a link between the first and second terminal devices, the second message indicating the failure.

In some example embodiments, the failure in obtaining the configuration associated with the CA communication with the second terminal device 120 may comprise at least one of: a failure in switching to the second mode, or a failure in obtaining a CA configuration from the network device 130.

In some example embodiments, in response to a success in obtaining a configuration associated with CA communication with the second terminal device 120, the first terminal device 110 may perform at least one of: in presence of a sidelink grant assigned by the network device 130, clearing the sidelink grant, or in absence of a sensing result on a resource pool configured by the network device 130, randomly selecting, from a further resource pool, a resource for communicating with the second terminal device 120.

In some example embodiments, in presence of the sidelink grant, the first terminal device 110 may transmit, to the network device 130, an indication to release the sidelink grant.

In some example embodiments, the first terminal device 110 may receive, from the second terminal device 120, information about CA communication between the first and second terminal devices.

FIG. 6 illustrates a flowchart of a communication method 600 implemented at a network device 130 in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 600 will be described from the perspective of the network device 130 in FIG. 1.

At block 610, the network device 130 receives, from the first terminal device 110, a request to switch from a first mode to a second mode. A connection is established between the first terminal device 110 and a second terminal device 120 capable of CA, and the first and second modes are different in sidelink resource allocation.

In some example embodiments, the request comprises at least one of: an indication to switch from the first mode to the second mode, information about one or more frequencies preferred by the first terminal device 110, information about one or more frequencies preferred by the second terminal device 120, information about one or more frequencies supported by the second terminal device 120, or a destination identity corresponding to at least one of the second terminal device 120 or a service type associated with the second terminal device 120.

In some example embodiments, the network device 130 may receive, from the first terminal device 110, an indication to release a sidelink grant assigned by the network device 130 to the first terminal device 110.

FIG. 7 illustrates a flowchart of a communication method 700 implemented at a second terminal device 120 in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 700 will be described from the perspective of the second terminal device 120 in FIG. 1.

At block 710, the second terminal device 120 establishes a connection with a first terminal device 110.

At block 720, the second terminal device 120 transmits, to the first terminal device 110, information about CA communication between the first and second terminal devices.

In some example embodiments, the second terminal device 120 may receive, from the first terminal device 110, a first message for requesting a non-CA communication with the second terminal device 120, the first message indicating a failure of the first terminal device 110 in obtaining a configuration associated with CA communication with the second terminal device 120, or receive, from the first terminal device 110, a second message to release a link between the first and second terminal devices, the second message indicating the failure.

In some example embodiments, the failure in obtaining the configuration associated with the CA communication with the second terminal device 120 may comprise at least one of: a failure of the first terminal device 110 in switching to the second mode, or a failure of the first terminal in obtaining a CA configuration from a network device 130.

FIG. 8 illustrates a flowchart of a communication method 800 implemented at a first terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 800 will be described from the perspective of the first terminal device 110 in FIG. 1.

At block 810, the first terminal device 110 determines an activation status of PDCP duplication for an original packet to be transmitted to at least one second terminal device 120 capable of CA.

At block 820, based on the activation status, the first terminal device 110, transmit, to the at least one second terminal device 120, at least one of: PDCP duplication information at least indicating the activation status for the packet, or feedback scheme information indicating a HARQ feedback scheme.

In some example embodiments, the activation status indicates that the PDCP duplication is activated for the original packet, and the PDCP duplication information further indicates at least one of: a carrier for transmitting the original packet, or a carrier for transmitting a duplicated packet corresponding to the original packet.

In some example embodiments, the PDCP duplication information is comprised in at least one of: a PDCP header of the original packet, a RLC header of the original packet, or a MAC header of the original packet.

In some example embodiments, the PDCP duplication information or the feedback scheme information is comprised in at least one of: sidelink control information (SCI) transmitted to the at least one second terminal device 120 before the original packet, a MAC CE transmitted to the at least one second terminal device 120 before the original packet, or a RRC message transmitted to the at least one second terminal device 120 before the original packet.

In some example embodiments, the activation status indicates that the PDCP duplication is activated for the original packet, and the feedback scheme information indicates a negative acknowledge only scheme to be used for the original packet.

FIG. 9 illustrates a flowchart of a communication method 900 implemented at a second terminal device 120 in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 900 will be described from the perspective of the second terminal device 120 in FIG. 1.

At block 910, the second terminal device 120 receives, from a first terminal device 110 performing CA communication with the second terminal device 120, at least one of: PDCP duplication information at least indicating an activation status of PDCP duplication for an original packet from the first terminal device 110, or feedback scheme information indicating a HARQ feedback scheme. The HARQ feedback scheme is determined based on the activation status.

In some example embodiments, the activation status may indicate that the PDCP duplication is activated for the original packet, and the PDCP duplication information further indicates at least one of: a carrier for transmitting the original packet, or a carrier for transmitting a duplicated packet corresponding to the original packet.

In some example embodiments, the PDCP duplication information or the feedback scheme information is comprised in at least one of: SCI received from the first terminal device 110 before the original packet, a MAC CE received from the first terminal device 110 before the original packet, or a RRC message received from the first terminal device 110 before the original packet.

FIG. 10 illustrates a flowchart of a communication method 1000 implemented at a first terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 1000 will be described from the perspective of the first terminal device 110 in FIG. 1.

At block 1010, the first terminal device 110 obtains compatibility information about carriers for at least one destination identity.

At block 1020, in response to an activation of PDCP duplication for an original packet, the first terminal device 110 determines a first carrier configured to a second terminal device 120 based on the compatibility information and a destination identity of the second terminal device 120, wherein the destination identity of the second terminal device 120 corresponds to at least one of the second terminal device 120 or a service type associated with the second terminal device 120, and the second terminal device 120 is incapable of CA.

At block 1030, the first terminal device 110 transmits the original packet over the first carrier and a duplicated packet corresponding to the original packet over a second carrier configured for CA communication.

In some example embodiments, the compatibility information is received from a network device 130.

In some example embodiments, the compatibility information indicates at least one of: whether a compatibility is required for each destination identity of at least one destination identity, a carrier for a terminal device incapable of CA, for each destination identity of at least one destination identity, a carrier to be used for original packet transmission, or for each destination identity of at least one destination identity, a carrier to be used for duplicated packet transmission.

In some example embodiments, the compatibility information is a profile generated by an upper layer of the first terminal device 110 for the destination identity of the second terminal device 120.

In some example embodiments, the compatibility information indicates at least one of: whether a compatibility is required for the destination identity of the second terminal device 120, a mapping between a carrier for using by a terminal device incapable of CA and the destination identity of the second terminal device 120, a mapping between one or more carriers for using by a terminal device capable of CA and the destination identity of the second terminal device 120, a mapping between a carrier for original packet transmission and the destination identity of the second terminal device 120, or a mapping between a carrier for duplicated packet transmission and the destination identity of the second terminal device 120.

FIG. 11 illustrates a flowchart of a communication method 1100 implemented at a network device 130 in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 1100 will be described from the perspective of the network device 130 in FIG. 1.

At block 1110, the network device 130 transmits, to a first terminal device 110 capable of CA, compatibility information about carriers for at least one destination identity. The compatibility information indicates at least one of: whether a compatibility is required for each destination identity of at least one destination identity, a carrier for a terminal device incapable of CA, for each destination identity of at least one destination identity, a carrier to be used for original packet transmission, or for each destination identity of at least one destination identity, a carrier to be used for duplicated packet transmission.

FIG. 12 is a simplified block diagram of a device 1200 that is suitable for implementing embodiments of the present disclosure. The device 1200 can be considered as a further example implementation of any of the devices as shown in FIG. 1. Accordingly, the device 1200 can be implemented at or as at least a part of the first terminal device 110, the second terminal device 120 or the network device 130.

As shown, the device 1200 includes a processor 1210, a memory 1220 coupled to the processor 1210, a suitable transceiver 1240 coupled to the processor 1210, and a communication interface coupled to the transceiver 1240. The memory 1220 stores at least a part of a program 1230. The transceiver 1240 may be for bidirectional communications or a unidirectional communication based on requirements. The transceiver 1240 may include at least one of a transmitter 1242 and a receiver 1244. The transmitter 1242 and the receiver 1244 may be functional modules or physical entities. The transceiver 1240 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/Xn interface for bidirectional communications between eNBs/gNBs, S1/NG interface for communication between a Mobility Management Entity (MME) /Access and Mobility Management Function (AMF) /SGW/UPF and the eNB/gNB, Un interface for communication between the eNB/gNB and a relay node (RN) , or Uu interface for communication between the eNB/gNB and a terminal device.

The program 1230 is assumed to include program instructions that, when executed by the associated processor 1210, enable the device 1200 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to FIGS. 1 to 11. The embodiments herein may be implemented by computer software executable by the processor 1210 of the device 1200, or by hardware, or by a combination of software and hardware. The processor 1210 may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor 1210 and memory 1220 may form processing means 1250 adapted to implement various embodiments of the present disclosure.

The memory 1220 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 1220 is shown in the device 1200, there may be several physically distinct memory modules in the device 1200. The processor 1210 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 1200 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.

According to embodiments of the present disclosure, a first terminal device comprising a circuitry is provided. The circuitry is configured to: establish a connection with a second terminal device capable of carrier aggregation (CA) ; and transmit, to a network device, a request to switch from a first mode to a second mode, wherein the first and second modes are different in sidelink resource allocation. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the first terminal device as discussed above.

According to embodiments of the present disclosure, a network device comprising a circuitry is provided. The circuitry is configured to: receive, from a first terminal device, a request to switch from a first mode to a second mode, wherein a connection is established between the first terminal device and a second terminal device capable of carrier aggregation (CA) , and the first and second modes are different in sidelink resource allocation. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the network device as discussed above.

According to embodiments of the present disclosure, a second terminal device comprising a circuitry is provided. The circuitry is configured to: establish a connection with a first terminal device; and transmit, to the first terminal device, information about CA communication between the first and second terminal devices. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the second terminal device as discussed above.

According to embodiments of the present disclosure, a first terminal device comprising a circuitry is provided. The circuitry is configured to: determine an activation status of Packet Data Convergence Protocol (PDCP) duplication for an original packet to be transmitted to at least one second terminal device capable of carrier aggregation (CA) ; and based on the activation status, transmit, to the at least one second terminal device, at least one of: PDCP duplication information at least indicating the activation status for the packet, or feedback scheme information indicating a Hybrid Automatic Repeat reQuest (HARQ) feedback scheme. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the first terminal device as discussed above.

According to embodiments of the present disclosure, a second terminal device comprising a circuitry is provided. The circuitry is configured to: receive, from a first terminal device performing carrier aggregation (CA) communication with the second terminal device, at least one of: Packet Data Convergence Protocol (PDCP) duplication information at least indicating an activation status of PDCP duplication for an original packet from the first terminal device, or feedback scheme information indicating a Hybrid Automatic Repeat reQuest (HARQ) feedback scheme, wherein the HARQ feedback scheme is determined based on the activation status. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the second terminal device as discussed above.

According to embodiments of the present disclosure, a first terminal device comprising a circuitry is provided. The circuitry is configured to: obtain compatibility information about carriers for at least one destination identity; in response to an activation of Packet Data Convergence Protocol (PDCP) duplication for an original packet, determine a first carrier configured to a second terminal device based on the compatibility information and a destination identity of the second terminal device, wherein the destination identity of the second terminal device corresponds to at least one of the second terminal device or a service type associated with the second terminal device, and the second terminal device is incapable of carrier aggregation (CA) ; and transmit the original packet over the first carrier and a duplicated packet corresponding to the original packet over a second carrier configured for CA communication. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the first terminal device as discussed above.

According to embodiments of the present disclosure, a network device comprising a circuitry is provided. The circuitry is configured to: transmit, to a first terminal device capable of carrier aggregation (CA) , compatibility information about carriers for at least one destination identity, wherein the compatibility information indicates at least one of: whether a compatibility is required for each destination identity of at least one destination identity, a carrier for a terminal device incapable of CA, for each destination identity of at least one destination identity, a carrier to be used for original packet transmission, or for each destination identity of at least one destination identity, a carrier to be used for duplicated packet transmission. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the network device as discussed above.

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.

According to embodiments of the present disclosure, a first terminal apparatus is provided. The first terminal apparatus comprises means for establishing a connection with a second terminal device capable of carrier aggregation (CA) ; and means for transmitting, to a network device, a request to switch from a first mode to a second mode, wherein the first and second modes are different in sidelink resource allocation. In some embodiments, the first apparatus may comprise means for performing the respective operations of the method 500. In some example embodiments, the first apparatus may further comprise means for performing other operations in some example embodiments of the method 500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a network apparatus is provided. The network apparatus comprises means for receiving, from a first terminal device, a request to switch from a first mode to a second mode, means for wherein a connection is established between the first terminal device and a second terminal device capable of carrier aggregation (CA) , and the first and second modes are different in sidelink resource allocation. In some embodiments, the second apparatus may comprise means for performing the respective operations of the method 600. In some example embodiments, the second apparatus may further comprise means for performing other operations in some example embodiments of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a second terminal apparatus is provided. The second terminal apparatus comprises means for establishing a connection with a first terminal device; and means for transmitting, to the first terminal device, information about CA communication between the first and second terminal devices. In some embodiments, the third apparatus may comprise means for performing the respective operations of the method 700. In some example embodiments, the third apparatus may further comprise means for performing other operations in some example embodiments of the method 700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a first terminal apparatus is provided. The first terminal apparatus comprises means for determining an activation status of Packet Data Convergence Protocol (PDCP) duplication for an original packet to be transmitted to at least one second terminal device, the at least one second terminal device performing carrier aggregation (CA) communication with the first terminal device, respectively; and means for based on the activation status, transmitting, to the at least one second terminal device, at least one of: means for PDCPing duplication information at least indicating the activation status for the packet, or means for feedbacking scheme information indicating a Hybrid Automatic Repeat reQuest (HARQ) feedback scheme. In some embodiments, the fourth apparatus may comprise means for performing the respective operations of the method 800. In some example embodiments, the fourth apparatus may further comprise means for performing other operations in some example embodiments of the method 800. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a second terminal apparatus is provided. The second terminal apparatus comprises means for receiving, from a first terminal device performing carrier aggregation (CA) communication with the second terminal device, at least one of: means for Packeting Data Convergence Protocol (PDCP) duplication information at least indicating an activation status of PDCP duplication for an original packet from the first terminal device, or means for feedbacking scheme information indicating a Hybrid Automatic Repeat reQuest (HARQ) feedback scheme, wherein the HARQ feedback scheme is determined based on the activation status. In some embodiments, the fifth apparatus may comprise means for performing the respective operations of the method 900. In some example embodiments, the fifth apparatus may further comprise means for performing other operations in some example embodiments of the method 900. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a first terminal apparatus is provided. The first terminal apparatus comprises means for obtaining compatibility information about carriers for at least one destination identity; means for in response to an activation of Packet Data Convergence Protocol (PDCP) duplication for an original packet, determining a first carrier configured to a second terminal device based on the compatibility information and a destination identity of the second terminal device, wherein the destination identity of the second terminal device corresponds to at least one of the second terminal device or a service type associated with the second terminal device, and the second terminal device is incapable of carrier aggregation (CA) ; and means for transmitting the original packet over the first carrier and a duplicated packet corresponding to the original packet over a second carrier configured for CA communication. In some embodiments, the sixth apparatus may comprise means for performing the respective operations of the method 1000. In some example embodiments, the sixth apparatus may further comprise means for performing other operations in some example embodiments of the method 1000. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a network apparatus is provided. The network apparatus comprises means for transmitting, to a first terminal device capable of carrier aggregation (CA) , compatibility information about carriers for at least one destination identity, wherein the compatibility information indicates at least one of: means for whether a compatibility is required for each destination identity of at least one destination identity, means for a carrier for a terminal device incapable of CA, means for for each destination identity of at least one destination identity, a carrier to be used for original packet transmission, or means for for each destination identity of at least one destination identity, a carrier to be used for duplicated packet transmission. In some embodiments, the seventh apparatus may comprise means for performing the respective operations of the method 1100. In some example embodiments, the seventh apparatus may further comprise means for performing other operations in some example embodiments of the method 1100. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In summary, embodiments of the present disclosure provide the following aspects.

In an aspect, it is proposed a first terminal device comprising: a processor configured to cause the first terminal device to: establish a connection with a second terminal device capable of carrier aggregation (CA) ; and transmit, to a network device, a request to switch from a first mode to a second mode, wherein the first and second modes are different in sidelink resource allocation.

In some embodiments, the first terminal device is caused to transmit the request to the network device in response to at least one of: that the first terminal device is configured with the first mode, that the first terminal device is configured with the second mode without a CA configuration, that the connection is established and capability information from the second terminal device indicates a CA capability of the second terminal device, that the connection is established, capability information from the second terminal device indicates a CA capability of the second terminal device, and a decision of the first terminal device to perform CA communication with the second terminal device, that the connection is established, or that the connection is established, capability information from the second terminal device indicates a CA capability of the second terminal device, and a CA configuration for the second terminal device is received from the second terminal device.

In some embodiments, the request comprises at least one of: an indication to switch from the first mode to the second mode, information about one or more frequencies preferred by the first terminal device, information about one or more frequencies preferred by the second terminal device, information about one or more frequencies supported by the second terminal device, or a destination identity corresponding to at least one of the second terminal device or a service type associated with the second terminal device.

In some embodiments, the first terminal device is further caused to in response to a failure in obtaining a configuration associated with CA communication with the second terminal device, transmit, to the second terminal device, a first message for requesting a non-CA communication with the second terminal device, the first message indicating the failure, or transmit, to the second terminal device, a second message to release a link between the first and second terminal devices, the second message indicating the failure.

In some embodiments, the failure in obtaining the configuration associated with the CA communication with the second terminal device comprises at least one of: a failure in switching to the second mode, or a failure in obtaining a CA configuration from the network device.

In some embodiments, the first terminal device is further caused to in response to a success in obtaining a configuration associated with CA communication with the second terminal device, perform at least one of: in presence of a sidelink grant assigned by the network device, clearing the sidelink grant, or in absence of a sensing result on a resource pool configured by the network device, randomly selecting, from a further resource pool, a resource for communicating with the second terminal device.

In some embodiments, the first terminal device is further caused to: in presence of the sidelink grant, transmit, to the network device, an indication to release the sidelink grant.

In some embodiments, the first terminal device is further caused to: receive, from the second terminal device, information about CA communication between the first and second terminal devices.

In an aspect, it is proposed a network device comprising: a processor configured to cause the network device to: receive, from a first terminal device, a request to switch from a first mode to a second mode, wherein a connection is established between the first terminal device and a second terminal device capable of carrier aggregation (CA) , and the first and second modes are different in sidelink resource allocation.

In some embodiments, the network device is further caused to: receive, from the first terminal device, an indication to release a sidelink grant assigned by the network device to the first terminal device.

In an aspect, it is proposed a second terminal device comprising: a processor configured to cause the second terminal device capable of carrier aggregation (CA) to: establish a connection with a first terminal device; and transmit, to the first terminal device, information about CA communication between the first and second terminal devices.

In some embodiments, the second terminal device is further caused to: receive, from the first terminal device, a first message for requesting a non-CA communication with the second terminal device, the first message indicating a failure of the first terminal device in obtaining a configuration associated with CA communication with the second terminal device, or receive, from the first terminal device, a second message to release a link between the first and second terminal devices, the second message indicating the failure.

In some embodiments, the failure in obtaining the configuration associated with the CA communication with the second terminal device comprises at least one of: a failure of the first terminal device in switching to the second mode, or a failure of the first terminal in obtaining a CA configuration from a network device.

In an aspect, it is proposed a first terminal device comprising: a processor configured to cause the first terminal device to: determine an activation status of Packet Data Convergence Protocol (PDCP) duplication for an original packet to be transmitted to at least one second terminal device capable of carrier aggregation (CA) ; and based on the activation status, transmit, to the at least one second terminal device, at least one of: PDCP duplication information at least indicating the activation status for the packet, or feedback scheme information indicating a Hybrid Automatic Repeat reQuest (HARQ) feedback scheme.

In some embodiments, the activation status indicates that the PDCP duplication is activated for the original packet, and the PDCP duplication information further indicates at least one of: a carrier for transmitting the original packet, or a carrier for transmitting a duplicated packet corresponding to the original packet.

In some embodiments, the PDCP duplication information is comprised in at least one of: a PDCP header of the original packet, a radio link control (RLC) header of the original packet, or a medium access control (MAC) header of the original packet.

In some embodiments, the PDCP duplication information or the feedback scheme information is comprised in at least one of: sidelink control information (SCI) transmitted to the at least one second terminal device before the original packet, a MAC control element (CE) transmitted to the at least one second terminal device before the original packet, or a radio resource control (RRC) message transmitted to the at least one second terminal device before the original packet.

In some embodiments, the activation status indicates that the PDCP duplication is activated for the original packet, and the feedback scheme information indicates a negative acknowledge only scheme to be used for the original packet.

In an aspect, it is proposed a second terminal device comprising: a processor configured to cause the second terminal device to: receive, from a first terminal device performing carrier aggregation (CA) communication with the second terminal device, at least one of: Packet Data Convergence Protocol (PDCP) duplication information at least indicating an activation status of PDCP duplication for an original packet from the first terminal device, or feedback scheme information indicating a Hybrid Automatic Repeat reQuest (HARQ) feedback scheme, wherein the HARQ feedback scheme is determined based on the activation status.

In some embodiments, the PDCP duplication information or the feedback scheme information is comprised in at least one of: sidelink control information (SCI) received from the first terminal device before the original packet, a MAC control element (CE) received from the first terminal device before the original packet, or a radio resource control (RRC) message received from the first terminal device before the original packet.

In an aspect, it is proposed a first terminal device comprising: a processor configured to cause the first terminal device to: obtain compatibility information about carriers for at least one destination identity; in response to an activation of Packet Data Convergence Protocol (PDCP) duplication for an original packet, determine a first carrier configured to a second terminal device based on the compatibility information and a destination identity of the second terminal device, wherein the destination identity of the second terminal device corresponds to at least one of the second terminal device or a service type associated with the second terminal device, and the second terminal device is incapable of carrier aggregation (CA) ; and transmit the original packet over the first carrier and a duplicated packet corresponding to the original packet over a second carrier configured for CA communication.

In some embodiments, the compatibility information is received from a network device.

In some embodiments, the compatibility information indicates at least one of: whether a compatibility is required for each destination identity of at least one destination identity, a carrier for a terminal device incapable of CA, for each destination identity of at least one destination identity, a carrier to be used for original packet transmission, or for each destination identity of at least one destination identity, a carrier to be used for duplicated packet transmission.

In some embodiments, the compatibility information is a profile generated by an upper layer of the first terminal device for the destination identity of the second terminal device.

In some embodiments, the compatibility information indicates at least one of: whether a compatibility is required for the destination identity of the second terminal device, a mapping between a carrier for using by a terminal device incapable of CA and the destination identity of the second terminal device, a mapping between one or more carriers for using by a terminal device capable of CA and the destination identity of the second terminal device, a mapping between a carrier for original packet transmission and the destination identity of the second terminal device, or a mapping between a carrier for duplicated packet transmission and the destination identity of the second terminal device.

In an aspect, it is proposed a network device comprising: a processor configured to cause the network device to: transmit, to a first terminal device capable of carrier aggregation (CA) , compatibility information about carriers for at least one destination identity, wherein the compatibility information indicates at least one of: whether a compatibility is required for each destination identity of at least one destination identity, a carrier for a terminal device incapable of CA, for each destination identity of at least one destination identity, a carrier to be used for original packet transmission, or for each destination identity of at least one destination identity, a carrier to be used for duplicated packet transmission.

In an aspect, a first terminal device comprises: at least one processor; and at least one memory coupled to the at least one processor and storing instructions thereon, the instructions, when executed by the at least one processor, causing the device to perform the method implemented by the first terminal device discussed above.

In an aspect, a network device comprises: at least one processor; and at least one memory coupled to the at least one processor and storing instructions thereon, the instructions, when executed by the at least one processor, causing the device to perform the method implemented by the network device discussed above.

In an aspect, a second terminal device comprises: at least one processor; and at least one memory coupled to the at least one processor and storing instructions thereon, the instructions, when executed by the at least one processor, causing the device to perform the method implemented by the second terminal device discussed above.

In an aspect, a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the first terminal device discussed above.

In an aspect, a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the network device discussed above.

In an aspect, a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the second terminal device discussed above.

In an aspect, a computer program comprising instructions, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the first terminal device discussed above.

In an aspect, a computer program comprising instructions, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the network device discussed above.

In an aspect, a computer program comprising instructions, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the second terminal device discussed above.

Generally, various 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 embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it will be appreciated that the blocks, apparatus, systems, techniques or methods 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 process or method as described above with reference to FIGS. 1 to 11. 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 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.

The above program code may be embodied on a machine readable medium, which may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine 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 machine 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) , 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 embodiments. Certain features that are described in the context of separate 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 embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language 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.

Claims

A first terminal device comprising:

a processor configured to cause the first terminal device to:

establish a connection with a second terminal device capable of carrier aggregation (CA) ; and

transmit, to a network device, a request to switch from a first mode to a second mode, wherein the first and second modes are different in sidelink resource allocation.
The first terminal device of claim 1, wherein the first terminal device is caused to transmit the request to the network device in response to at least one of:

that the first terminal device is configured with the first mode,

that the first terminal device is configured with the second mode without a CA configuration,

that the connection is established and capability information from the second terminal device indicates a CA capability of the second terminal device,

that the connection is established, capability information from the second terminal device indicates a CA capability of the second terminal device, and a decision of the first terminal device to perform CA communication with the second terminal device,

that the connection is established, or

that the connection is established, capability information from the second terminal device indicates a CA capability of the second terminal device, and a CA configuration for the second terminal device is received from the second terminal device.
The first terminal device of claim 1, wherein the first terminal device is further caused to in response to a failure in obtaining a configuration associated with CA communication with the second terminal device,

transmit, to the second terminal device, a first message for requesting a non-CA communication with the second terminal device, the first message indicating the failure, or

transmit, to the second terminal device, a second message to release a link between the first and second terminal devices, the second message indicating the failure.
The first terminal device of claim 1, wherein the first terminal device is further caused to in response to a success in obtaining a configuration associated with CA communication with the second terminal device, perform at least one of:

in presence of a sidelink grant assigned by the network device, clearing the sidelink grant, or

in absence of a sensing result on a resource pool configured by the network device, randomly selecting, from a further resource pool, a resource for communicating with the second terminal device.
A network device comprising:

a processor configured to cause the network device to:

receive, from a first terminal device, a request to switch from a first mode to a second mode,

wherein a connection is established between the first terminal device and a second terminal device capable of carrier aggregation (CA) , and the first and second modes are different in sidelink resource allocation.
A second terminal device comprising:

a processor configured to cause the second terminal device capable of carrier aggregation (CA) to:

establish a connection with a first terminal device; and

transmit, to the first terminal device, information about CA communication between the first and second terminal devices.
The second terminal device of claim 6, wherein the second terminal device is further caused to:

receive, from the first terminal device, a first message for requesting a non-CA communication with the second terminal device, the first message indicating a failure of the first terminal device in obtaining a configuration associated with CA communication with the second terminal device, or

receive, from the first terminal device, a second message to release a link between the first and second terminal devices, the second message indicating the failure.
A first terminal device comprising:

a processor configured to cause the first terminal device to:

determine an activation status of Packet Data Convergence Protocol (PDCP) duplication for an original packet to be transmitted to at least one second terminal device capable of carrier aggregation (CA) ; and

based on the activation status, transmit, to the at least one second terminal device, at least one of:

PDCP duplication information at least indicating the activation status for the original packet, or

feedback scheme information indicating a Hybrid Automatic Repeat reQuest (HARQ) feedback scheme.
The first terminal device of claim 8, wherein the PDCP duplication information or the feedback scheme information is comprised in at least one of:

sidelink control information (SCI) transmitted to the at least one second terminal device before the original packet,

a MAC control element (CE) transmitted to the at least one second terminal device before the original packet, or

a radio resource control (RRC) message transmitted to the at least one second terminal device before the original packet.
A second terminal device comprising:

a processor configured to cause the second terminal device to:

receive, from a first terminal device performing carrier aggregation (CA) communication with the second terminal device, at least one of:

Packet Data Convergence Protocol (PDCP) duplication information at least indicating an activation status of PDCP duplication for an original packet from the first terminal device, or

feedback scheme information indicating a Hybrid Automatic Repeat reQuest (HARQ) feedback scheme, wherein the HARQ feedback scheme is determined based on the activation status.
The second terminal device of claim 10, wherein the activation status indicates that the PDCP duplication is activated for the original packet, and the PDCP duplication information further indicates at least one of:

a carrier for transmitting the original packet, or

a carrier for transmitting a duplicated packet corresponding to the original packet.
The second terminal device of claim 10, wherein the PDCP duplication information or the feedback scheme information is comprised in at least one of:

sidelink control information (SCI) received from the first terminal device before the original packet,

a MAC control element (CE) received from the first terminal device before the original packet, or

a radio resource control (RRC) message received from the first terminal device before the original packet.
A first terminal device comprising:

a processor configured to cause the first terminal device to:

obtain compatibility information about carriers for at least one destination identity;

in response to an activation of Packet Data Convergence Protocol (PDCP) duplication for an original packet, determine a first carrier configured to a second terminal device based on the compatibility information and a destination identity of the second terminal device, wherein the destination identity of the second terminal device corresponds to at least one of the second terminal device or a service type associated with the second terminal device, and the second terminal device is incapable of carrier aggregation (CA) ; and

transmit the original packet over the first carrier and a duplicated packet corresponding to the original packet over a second carrier configured for CA communication.
The first terminal device of claim 13, wherein the compatibility information is received from a network device and indicates at least one of:

whether a compatibility is required for each destination identity of at least one destination identity,

a carrier for a terminal device incapable of CA,

for each destination identity of at least one destination identity, a carrier to be used for original packet transmission, or

for each destination identity of at least one destination identity, a carrier to be used for duplicated packet transmission.
The first terminal device of claim 13, wherein the compatibility information is a profile generated by an upper layer of the first terminal device for the destination identity of the second terminal device, and the compatibility information indicates at least one of:

whether a compatibility is required for the destination identity of the second terminal device,

a mapping between a carrier for using by a terminal device incapable of CA and the destination identity of the second terminal device,

a mapping between one or more carriers for using by a terminal device capable of CA and the destination identity of the second terminal device,

a mapping between a carrier for original packet transmission and the destination identity of the second terminal device, or

a mapping between a carrier for duplicated packet transmission and the destination identity of the second terminal device.
A network device comprising:

a processor configured to cause the network device to:

transmit, to a first terminal device capable of carrier aggregation (CA) , compatibility information about carriers for at least one destination identity, wherein the compatibility information indicates at least one of:

whether a compatibility is required for each destination identity of at least one destination identity,

a carrier for a terminal device incapable of CA,

for each destination identity of at least one destination identity, a carrier to be used for original packet transmission, or

for each destination identity of at least one destination identity, a carrier to be used for duplicated packet transmission.
A communication method implemented at a first terminal device, comprising:

establishing a connection with a second terminal device capable of carrier aggregation (CA) ; and

transmitting, to a network device, a request to switch from a first mode to a second mode, wherein the first and second modes are different in sidelink resource allocation.
A communication method implemented at a first terminal device, comprising:

determining an activation status of Packet Data Convergence Protocol (PDCP) duplication for an original packet to be transmitted to at least one second terminal device capable of carrier aggregation (CA) ; and

based on the activation status, transmitting, to the at least one second terminal device, at least one of:

PDCP duplication information at least indicating the activation status for the packet, or

feedback scheme information indicating a Hybrid Automatic Repeat reQuest (HARQ) feedback scheme.
A communication method implemented at a second terminal device, comprising:

receiving, from a first terminal device performing carrier aggregation (CA) communication with the second terminal device, at least one of:

Packeting Data Convergence Protocol (PDCP) duplication information at least indicating an activation status of PDCP duplication for an original packet from the first terminal device, or

feedback scheme information indicating a Hybrid Automatic Repeat reQuest (HARQ) feedback scheme, wherein the HARQ feedback scheme is determined based on the activation status.
A communication method implemented at a first terminal device, comprising:

obtaining compatibility information about carriers for at least one destination identity;

in response to an activation of Packet Data Convergence Protocol (PDCP) duplication for an original packet, determining a first carrier configured to a second terminal device based on the compatibility information and a destination identity of the second terminal device, wherein the destination identity of the second terminal device corresponds to at least one of the second terminal device or a service type associated with the second terminal device, and the second terminal device is incapable of carrier aggregation (CA) ; and

transmitting the original packet over the first carrier and a duplicated packet corresponding to the original packet over a second carrier configured for CA communication.