CN113708898A

CN113708898A - Communication method and device

Info

Publication number: CN113708898A
Application number: CN202010438317.9A
Authority: CN
Inventors: 赵力; 徐海博; 王君
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-05-21
Filing date: 2020-05-21
Publication date: 2021-11-26
Also published as: WO2021233164A1

Abstract

A communication method and a device can solve the problem how to start a first timer and a second timer under the condition that PUCCH resources are not configured for a first terminal device, thereby reducing the communication time delay of Sidelink and meeting the QoS requirement of Sidelink. The method comprises two schemes, wherein one scheme is that after the first terminal equipment sends Sidelink data on PSSCH resources, a first timer is started according to the time domain position of the PSSCH resources, and then a second timer is started. The other is to start a first timer according to the time domain position of the PSFCH resource after receiving the HARQ feedback on the PSFCH resource, and then start a second timer.

Description

Communication method and device

Technical Field

The embodiment of the application relates to the technical field of communication, in particular to a communication method and device.

Background

In a Long Term Evolution (LTE) system or a New Radio (NR) system, a communication interface between a UE and a base station is called a Uu air interface. On the Uu air interface, a link through which the UE sends data to the base station is called Uplink (UL). A link, called Downlink (DL), through which the base station transmits data to the UE. The communication interface between the UE and the UE is referred to as the PC5 interface. On the PC5 interface, the link between the UE and the UE for transmitting data is called Sidelink (SL). Currently, there are two resource allocation methods for Sidelink. One is an allocation mode that the UE autonomously selects resources in a resource pool, that is, the UE itself selects resources in the resource pool configured or preconfigured by the network through system messages or dedicated signaling to transmit the Sidelink data. The other is a resource allocation mode based on base station scheduling, that is, the base station schedules the Sidelink resource for transmitting the user equipment TXUE to transmit the data of the Sidelink. In the method for allocating the Sidelink resource scheduled by the base station, the base station issues Downlink Control Information (DCI) in a Physical Downlink Control Channel (PDCCH) to dynamically allocate the Sidelink resource, and the TXUE needs to monitor the PDCCH to obtain a Sidelink grant (grant) issued by the base station. How the TX UE monitors the PDCCH is a technical problem to be solved by the embodiments of the present application.

Disclosure of Invention

The embodiment of the application provides a communication method and device, so that a first terminal device monitors a PDCCH.

In a first aspect, a communication method is provided, which is applicable to a case where a psch resource has an associated PUCCH resource and also applicable to a case where the psch resource does not have an associated PUCCH resource. The execution subject of the method is a first terminal device and a second terminal device. It is understood that the first terminal device and the second terminal device may be terminal devices, or may be components (e.g., chips, circuits, or others) configured in the terminal devices. The method comprises the following steps:

a first terminal device receives first DCI from a network device, wherein the first DCI is used for scheduling ith transmission of a Sidelink HARQ process, and the Sidelink HARQ process is associated with or maintains two timers, namely a first timer and a second timer; the first terminal device may send the Sidelink data to the second terminal device by using the above Sidelink HARQ process according to the scheduling of the first DCI. The first terminal device may start the first timer according to a time domain position of a psch resource transmitting the Sidelink data. And when the first timer is overtime, directly starting the second timer. Alternatively, the first terminal device may start or not start the second timer according to the condition that the PSFCH resource receives the HARQ feedback of the Sidelink HARQ process. Wherein the first terminal device may monitor the PDCCH during operation of the second timer.

Through the method, the first terminal equipment can start the first timer and the second timer according to the time domain position of the PSSCH resource. Therefore, the first timer and the second timer can be started successfully under the condition that the PUCCH resource is not configured, and the requirement that the first terminal equipment monitors the PDCCH is met. Further, during the operation period of the second timer, the (i + 1) th transmission for scheduling the Sidelink HARQ process can be monitored, so that the communication delay of the Sidelink can be reduced, and the QoS requirement of the Sidelink can be met.

In one possible design, the first terminal device may determine the first time domain location based on the time domain location of the psch resource and the first time domain offset; or, taking the first time unit after the end position of the time domain position of the PSSCH resource as the first time domain position; and starting a first timer at the first time domain position.

The first time domain offset may be protocol-specified, or configured by the network device, or implemented inside the terminal device, without limitation. By flexibly setting the first time domain offset, the time domain unit for starting the first timer can be flexibly set.

In one possible design, before starting the first timer, the terminal device may further determine the number of transmission times of the Sidelink data associated with the lower Sidelink HARQ process. And when the transmission times are greater than or equal to the maximum transmission times or the preset transmission times, indicating that the transmission of the current Sidelink data exceeds the maximum transmission times or the preset transmission times. At this point, the network device will not continue to allocate psch resources for the sildenk data. Therefore, it is not necessary to start the first timer at this time. And when the transmission times are smaller than the maximum transmission times or the preset transmission times, continuously starting the first timer.

Compared with the method that HARQ feedback of the Sidelink HARQ process is not considered completely, the method can directly start the first timer, and can reduce power consumption of the terminal equipment.

In one possible design, if the first terminal device is configured with PSFCH resources. And before the first timer expires, if the first terminal device can determine HARQ feedback for the Sidelink HARQ process. And when the HARQ feedback is NACK, directly starting a second timer when the first timer is overtime. And when the HARQ feedback is ACK, the first timer may be directly stopped, and at this time, there is no longer a case where the first timer is overtime, so that the second timer is not required to be started, or the first terminal device may not stop the first timer, but does not start the second timer when the first timer is overtime.

By the method, the first terminal equipment determines whether to start the first timer according to the HARQ feedback condition. Compared with the situation that the first timer is started under any condition, the power consumption of the terminal equipment can be reduced.

In one possible design, if the first terminal device is configured with PSFCH resources and before the first timer expires, HARQ feedback for the Sidelink HARQ process cannot be determined. The first terminal device may start the second timer directly after the first timer expires. During the running period of the second timer, if the HARQ feedback of the Sidelink HARQ process is ACK, the first terminal device may directly stop the second timer and no longer monitor the PDCCH. Or, if the HARQ feedback of the Sidelink HARQ process is NAKC, the first terminal device may not stop the second timer and continue to monitor the PDCCH.

By the method, when the HARQ feedback is determined to be ACK, the network equipment does not schedule PSSCH resources for the first terminal equipment any more, and the second timer is stopped at the moment, so that the power consumption of the terminal equipment can be reduced.

In a possible design, during the operation of the second timer, if the first terminal device monitors and receives the PDCCH for scheduling the Sidelink data retransmission, the first terminal device may directly stop the second timer, so as to further reduce the power consumption of the terminal device.

In a second aspect, a communication method is provided, which is applicable to both a case where a psch resource has an associated PUCCH resource and a case where the psch resource does not have an associated PUCCH resource. The execution subject of the method is a first terminal device and a second terminal device. It is understood that the first terminal device and the second terminal device may be terminal devices, or may be components (e.g., chips, circuits, or others) configured in the terminal devices. The method comprises the following steps:

the first terminal device receives first DCI from the network device, wherein the first DCI is used for scheduling the ith transmission of the Sidelink HARQ process. The Sidelink HARQ process maintains or associates two timers, a first timer and a second timer, respectively. The first terminal device may send the Sidelink data to the second terminal device by using the Sidelink HARQ process according to the scheduling of the first DCI. The first terminal device may or may not start the first timer according to the HARQ feedback of the Sidelink HARQ process and the time domain position of the PSFCH resource receiving the HARQ feedback. For example, when the HARQ feedback of the Sidelink HARQ process is NACK, the first timer may be started according to the time domain position of the PSFCH resource. And when the HARQ feedback of the Sidelink HARQ process is ACK, the first timer is not started any more. Under the condition of starting the first timer, when the first timer is overtime, the second timer can be directly started. The first terminal device monitors the PDCCH during the operation of the second timer.

Through the method, the first terminal device can start the first timer and the second timer according to the time domain position of the PSFCH resource. Therefore, the first timer and the second timer can be started successfully under the condition that the PUCCH resource is not configured, and the requirement that the first terminal equipment monitors the PDCCH is met. Further, during the operation period of the second timer, the (i + 1) th transmission for scheduling the Sidelink HARQ process can be monitored, so that the communication delay of the Sidelink can be reduced, and the QoS requirement of the Sidelink can be met.

In one possible design, the first terminal device determines a second time domain position according to the time domain resource position of the first PSFCH resource and the second time domain offset; or, the first terminal device uses the first time unit after the end position of the time domain resource of the first PSFCH resource as the second time domain position.

The second time domain offset may be protocol-specified, or configured by the network device, or implemented inside the terminal device, without limitation. By flexibly setting the second time domain offset, the time domain unit for starting the first timer can be flexibly set.

In one possible design, the first terminal device may start or not start the first timer at the second time domain position according to the HARQ feedback. For example, when the first terminal device determines that the HARQ feedback of the Sidelink HARQ process is NACK, the first terminal device starts the first timer at the second time domain position; otherwise, the first timer is not started any more at the second time domain position by the first terminal equipment.

Through the method, the first terminal equipment determines whether to start the first timer or not according to the HARQ feedback of the Sidelink HARQ process. Compared with the situation that the first terminal equipment is in the second time domain position, the first timer is started, and the power consumption of the terminal equipment can be reduced.

In one possible design, the starting of the first timer by the first terminal device at the second time domain position includes determining, by the first terminal device, the number of transmission times of the Sidelink data associated with the Sidelink HARQ process;

and if the transmission times of the Sidelink data associated with the Sidelink HARQ process are less than or equal to the maximum transmission times or preset transmission times, the first terminal equipment starts the first timer at the second time domain position. Otherwise, the first terminal device does not start the first timer at the second time domain position.

In the method, the maximum transmission number or the preset transmission number may be specified by a protocol, or configured by a network device, or implemented inside a terminal device. When the transmission frequency of the Sidelink data reaches the maximum transmission frequency or the preset transmission frequency, the network equipment does not schedule the (i + 1) th transmission of the Sidelink HARQ process, and at the moment, the first terminal equipment is set not to start the first timer any more, so that the power consumption of the first terminal equipment is reduced.

In one possible design, in a case where the first terminal device starts the second timer, the method further includes: during the running period of the second timer, if the first terminal device monitors a PDCCH for scheduling the first terminal device Sidelink data retransmission, the first terminal device stops the second timer.

In a third aspect, embodiments of the present application further provide an apparatus, and beneficial effects may be seen in the description of the first aspect. The apparatus has the functionality to implement the actions in the method embodiments of the first aspect described above. The functions may be implemented by executing corresponding hardware or software. The hardware or software may include one or more modules corresponding to the above functions. In one possible design, the apparatus may include: a transceiving unit, configured to receive first downlink control information DCI from a network device, where the first DCI is used to schedule initial transmission or retransmission of Sidelink data, and a Sidelink HARQ process associated with the Sidelink data is associated with two timers, which are a first timer and a second timer, respectively; a processing unit, configured to send Sidelink data to a second terminal device by using a physical Sidelink shared channel PSSCH resource according to the scheduling of the first DCI; the processing unit is further used for starting a first timer according to the time domain position of the PSSCH resource; the processing unit is also used for starting or not starting a second timer according to the first timer; and under the condition of starting a second timer, monitoring a Physical Downlink Control Channel (PDCCH) by the first terminal equipment during the running period of the second timer. The units may perform corresponding functions in the method example of the first aspect, for specific reference, detailed description of the method example is given, and details are not repeated here.

In a fourth aspect, the embodiments of the present application further provide an apparatus, and the beneficial effects can be seen in the description of the second aspect. The apparatus has the functionality to implement the actions in the method embodiment of the second aspect described above. The functions may be performed by executing corresponding hardware or software. The hardware or software may include one or more modules corresponding to the above functions. In one possible design, the apparatus includes: a transceiving unit, configured to receive first downlink control information DCI from a network device, where the first DCI is used to schedule initial transmission or retransmission of Sidelink data, and a Sidelink HARQ process associated with the Sidelink data is associated with two timers, which are a first timer and a second timer, respectively; a processing unit, configured to send Sidelink data to a second terminal device by using a physical Sidelink shared channel PSSCH resource according to the scheduling of the first DCI; the processing unit is further configured to receive, by using a physical Sidelink feedback channel PSFCH resource, HARQ feedback from the second terminal device to the Sidelink HARQ process, where the HARQ feedback is an ACK or NACK; the processing unit is further configured to start or not start a first timer according to the HARQ feedback and the time domain position of the PSFCH resource; under the condition that the first timer is started, when the first timer is over time, the first terminal equipment starts a second timer, and during the running period of the second timer, the first terminal equipment monitors a Physical Downlink Control Channel (PDCCH). The units may perform corresponding functions in the method example of the second aspect, for specific reference, detailed description of the method example is given, and details are not repeated here.

A fifth aspect provides an apparatus, which may be the terminal device in the method embodiment of the first aspect, or a chip disposed in the terminal device. The device comprises a communication interface, a processor and optionally a memory. Wherein the memory is adapted to store a computer program or instructions, and the processor is coupled to the memory and the communication interface, and when the processor executes said computer program or instructions, the apparatus is adapted to perform the method performed by the terminal device in the method embodiment of the first aspect.

In a sixth aspect, an apparatus is provided, which may be the terminal device in the method embodiment of the second aspect, or a chip disposed in the terminal device. The device comprises a communication interface, a processor and optionally a memory. Wherein the memory is adapted to store a computer program or instructions, and the processor is coupled to the memory and the communication interface, and when the processor executes the computer program or instructions, the apparatus is adapted to perform the method performed by the terminal device in the method embodiment of the second aspect.

In a seventh aspect, a computer program product is provided, the computer program product comprising: computer program code which, when run, causes the method performed by the terminal device in the above-described first aspect to be performed.

In an eighth aspect, there is provided a computer program product comprising: computer program code which, when executed, causes the method performed by the terminal device in the second aspect described above to be performed.

In a ninth aspect, the present application provides a chip system, where the chip system includes a processor, and is configured to implement the function of the terminal device in the method of the first aspect. In one possible design, the system-on-chip further includes a memory for storing program instructions and/or data. The chip system may be formed by a chip, or may include a chip and other discrete devices.

In a tenth aspect, the present application provides a chip system, where the chip system includes a processor, and is configured to implement the function of the terminal device in the method of the second aspect. In one possible design, the system-on-chip further includes a memory for storing program instructions and/or data. The chip system may be formed by a chip, or may include a chip and other discrete devices.

In an eleventh aspect, the present application provides a computer-readable storage medium storing a computer program that, when executed, implements the method performed by the terminal device in the first aspect.

In a twelfth aspect, the present application provides a computer-readable storage medium storing a computer program which, when executed, implements the method performed by the terminal device in the second aspect.

Drawings

Fig. 1 is a schematic diagram of a network architecture according to an embodiment of the present application;

fig. 2A, fig. 2B and fig. 2C are schematic diagrams of DRX provided in the embodiment of the present application;

fig. 3 is a flowchart of a communication method according to an embodiment of the present application;

fig. 4 is a flowchart of a communication method according to an embodiment of the present application;

fig. 5 is a flowchart of a communication method according to an embodiment of the present application;

fig. 6 is a flowchart of a communication method according to an embodiment of the present application;

fig. 7 is a flowchart of a communication method according to an embodiment of the present application;

fig. 8 is a schematic structural diagram of a communication device according to an embodiment of the present application;

fig. 9 is a schematic structural diagram of a communication device according to an embodiment of the present application.

Detailed Description

The terminology used in the description of the embodiments section of the present application is for the purpose of describing particular embodiments of the present application only and is not intended to be limiting of the present application.

Fig. 1 illustrates a wireless communication system 100 to which the present application relates. The wireless communication system 100 may be a Long Term Evolution (LTE) system, a fifth generation mobile communication (5)^thgeneration, 5G) system, New Radio (NR) system, machine to machine (M2M) system, future-evolution, sixth-generation communication system, and the like. As shown in fig. 1, the wireless communication system 100 may include: one or more network devices 101, two or more terminal devices 103, and a core network (not shown). Wherein:

network device 101 may be configured to communicate with terminal device 103 via Uu interface 105 under the control of a network device controller (not shown), such as a Base Station Controller (BSC). On the Uu interface 105, a link in which the terminal device 103 transmits data to the network device 101 is called an Uplink (UL), and a link in which the terminal device 103 receives data transmitted by the network device 100 is called a Downlink (DL). In some embodiments, the network device controller may be part of the core network or may be integrated into the network device 101.

The network device 101 may also be configured to transmit control information or user data to the core network via a backhaul (backhaul) interface, such as an S1 interface.

The

network devices

101 and 101 may also communicate with each other directly or indirectly through a backhaul (backhaul) interface, such as an X2 interface.

The communication interface 107 between the terminal device 103 and the terminal device 103 is referred to as a PC5 interface. On the PC5 interface 107, a link between the terminal device 103 and the terminal device 103 for transmitting data is called a Sidelink (SL). The Uu interface 105 may be used under control of a cellular network when the terminal device 103 is within an evolved universal terrestrial radio access network (E-UTRAN) coverage area. Terminal equipment 103 may use PC5 interface 107 for Sidelink communications whether or not within the coverage area of the E-UTRAN. The Sidelink communication may be a point-to-point communication between two terminal devices 103, or may be a multicast communication performed by a group of two or more terminal devices 103.

The network device 101 may be a Base Transceiver Station (BTS) in a time division synchronous code division multiple access (TD-SCDMA) system, an evolved node B (eNB) in an LTE system, a base station in a 5G system, a new air interface (NR) system, or the like. In addition, a base station may also be an Access Point (AP), a Transmission and Reception Point (TRP), a Central Unit (CU), or other network entity, and may include some or all of the functionality of the above network entities.

The terminal device 103 may be a vehicle-mounted terminal, a smart phone, a Road Side Unit (RSU), an internet of things terminal device, a Machine Type Communication (MTC) terminal, or other wireless communication devices. The terminal device may also include one or more base stations, such as micro base stations, having partial UE functionality. The terminal devices may be distributed throughout the wireless communication system 100 and may be stationary or mobile.

It should be noted that the wireless communication system 100 shown in fig. 1 is only for more clearly illustrating the technical solution of the present application, and does not constitute a limitation to the present application, and as a person having ordinary skill in the art knows, the technical solution provided in the present application is also applicable to similar technical problems as the network architecture evolves and new service scenarios emerge.

The Sidelink communication can be generally used in the scene of direct connection communication between devices such as V2X and the like. V2X refers to the connection of vehicles to a network or the connection of vehicles to a network, and there are 4 different types of applications, namely vehicle to vehicle (V2V), vehicle to infrastructure (V2I), vehicle to network (V2N), and vehicle to pedestrian (V2P). Through these 4 applications, vehicles, infrastructure on the roadside, application servers, and pedestrians collect, process, and share status information of surrounding vehicles and environments to provide more intelligent services, such as unmanned driving (unmanned driving), automated driving (autonomous driving/ADS), assisted driving (driver assistance/ADAS), intelligent driving (intelligent driving), internet driving (connected driving), intelligent internet driving (intelligent network driving), vehicle sharing (car sharing), and the like.

As shown in fig. 1, in the V2V scenario, the terminal device 103 may be a vehicle-mounted terminal. On the PC5 interface 107, data such as vehicle position, vehicle speed, driving direction, etc., indicating the dynamics of the vehicle, can be exchanged between the in-vehicle terminal and the in-vehicle terminal through the Sidelink. For example, the in-vehicle terminal a may transmit data indicating the driving dynamics of the vehicle in which the in-vehicle terminal a is located to another in-vehicle terminal B through Sidelink. In the sildelink communication, the in-vehicle terminal a is a TX UE, and the in-vehicle terminal B is an RX UE. Upon receiving the data, the in-vehicle terminal B may display the user interface 20. The contents 21 expressed by the data, such as the license plate number of the rear vehicle ("FAF 787"), the driving operation being performed by the rear vehicle ("overtaking operation being performed by the rear vehicle FAF 787"), the current vehicle speed of the rear vehicle ("80 km/h"), and the like, may be displayed in the user interface 20. Therefore, the traffic accident rate can be reduced, and the driving safety can be enhanced.

Currently, one of the main resource allocation methods for the Sidelink communication is a resource allocation method based on base station scheduling. In the sildelink resource allocation method, a base station issues downlink control information DCI on a PDCCH to dynamically allocate resources, and TXUE needs to monitor the PDCCH to obtain a sildelink grant (grant) issued by the base station.

On the Uu interface 105, in order to reduce power consumption caused by the UE monitoring the PDCCH all the time, a solution adopted by the current 3GPP is a Discontinuous Reception (DRX) mechanism. The following describes the existing DRX mechanism.

(1) Basic working principle of DRX mechanism

As shown in fig. 2A, in LTE or NR system, the DRX mechanism is one DRX cycle (DRX cycle) configured by the network device for the UE in Radio Resource Control (RRC) connected state. The DRX cycle consists of two periods of "On Duration" and "Opportunity for DRX". "On Duration" may be referred to as Duration, "Opportunity for DRX" may be referred to as DRX Opportunity. Within the "On Duration", the UE monitors and receives the PDCCH. Within "Opportunity for DRX," the UE does not monitor the PDCCH to reduce power consumption. The value of "On Duration" (e.g., 10ms) specifies the time the UE needs to monitor the PDCCH from the start of the DRX Cycle. The "On Duration" may be greater than 1ms or less than 1 ms. Within the "On Duration", the UE is in an active state, i.e., the UE monitors the PDCCH. Within "Opportunity for DRX", the UE is in a dormant state, i.e., the UE does not monitor the PDCCH. Here, the sleep state is only for monitoring the PDCCH, and means that the UE does not monitor the PDCCH. The UE in the dormant state is still in the RRC connected state, and can transmit uplink data via a Physical Uplink Control Channel (PUCCH) or a Physical Uplink Shared Channel (PUSCH) on the Uu interface 105, receive downlink data transmitted by the base station via a Physical Downlink Shared Channel (PDSCH), and transmit Sidelink data via a physical Sidelink shared channel (PSCCH) or a Physical Sidelink Control Channel (PSCCH) on the PC5 interface 107.

(2) Introduction of drx-InactivityTimer

In most cases, after a certain PDCCH Occasion (occupancy) is scheduled to receive or transmit data, the UE is likely to continue scheduling in the next several subframes (subframes) to complete the reception or transmission of a large byte of data. If the UE enters the dormant state, the UE waits for the next DRX cycle and monitors the PDCCH acquisition resource scheduling to receive or send subsequent data. This increases the latency of data transmission. To reduce such delays, the DRX mechanism introduces a timer: drx-InactivityTimer. As shown in fig. 2B, when the UE monitors and receives a PDCCH for scheduling new data, the UE starts (or restarts) a timer drx-inactivity timer. The UE will monitor the PDCCH every subframe during the drx-inactivity timer run until the timer expires. The indication information of the new data is carried in the PDCCH, and occupies 1 bit. It can be seen that, the introduction of the drx-inactivity timer can ensure that the UE is in an active state during the drx-inactivity timer operation, and receive the scheduling of the next base station, which is equivalent to extending the "On Duration". If the UE continuously receives the PDCCH for scheduling different new data, the UE may turn On (or restart) multiple DRX-inactivity timers one after another, which may cause the UE to be active throughout the DRX cycle, i.e., "On Duration" may extend to the entire DRX cycle.

(3)DRX

In the NR system, if a base station configures a retransmission mechanism based on hybrid automatic repeat request (HARQ) feedback for TXUE, then for a resource allocation method based on base station scheduling, one possible HARQ operation method is: the base station schedules retransmission resources for the TXUE according to HARQ feedback (feedback) of the Sidelink data transmission. The HARQ feedback may be a positive Acknowledgement (ACK) or a Negative Acknowledgement (NACK). As shown in fig. 2C, if the HARQ feedback of data a is NACK, the base station schedules resources for retransmission of data a after receiving the NACK, and issues a Sidelink grant (grant) for retransmission of data a on the PDCCH.

However, as shown in fig. 2C, when the HARQ of the data a transmitted by the Tx UE to the base station confirms NACK, the Tx UE needs to receive the PDCCH sent by the base station for scheduling retransmission of the data a, so as to perform retransmission of the data a. However, based on the current DRX mechanism, when the base station issues the PDCCH, the TX UE may already enter the "opportunity for DRX" state and no longer monitors the PDCCH. The TX UE needs to wait until the "On Duration" of the next DRX cycle to monitor the PDCCH, and then receives the PDCCH sent by the base station for scheduling the retransmission of data a, and then retransmits the data a. This may cause the data retransmission of TxUE on Sidelink to be delayed, resulting in that the QoS requirements of the traffic transmitted on Sidelink cannot be met.

In order to solve the existing technical problem, a scheme beneficial to reducing transmission delay of the Sidelink data is provided based on a Sidelink resource allocation mode scheduled by a base station, and the scheme comprises the following steps: when the TX UE sends HARQ feedback to the base station using PUCCH resources, a first timer is started, where the first timer may be drx-HARQ-RTT-TimerSL, and when the first timer expires, a second timer is started, where the second timer may be drx-retransmission TimerSL. The TX UE monitors the PDCCH in the running period of the second timer, thereby avoiding that the TX UE can monitor the PDCCH only in the 'On Duration' of the next DRX cycle and reducing the transmission delay of the Sildelink data. As can be seen from the above, in the above scheme, the TX UE starts the first timer and the second timer when feeding back the HARQ to the base station by using the PUCCH resource. In one scenario, if the base station does not configure PUCCH resources for the TX UE, the TX UE cannot send HARQ feedback to the base station, and further cannot start the first timer and the second timer. In this scenario, how to reduce the transmission delay of the Sidelink data is a technical problem to be solved by the embodiment of the present application.

Based on the above, embodiments of the present application provide a communication method and apparatus, which can start a first timer and a second timer when a TX UE does not configure a PUCCH resource, so as to reduce transmission delay of Sidelink data. The method can comprise two schemes: the first scheme is as follows: after the TX UE sends Sidelink data on PSSCH resources, a first timer is started according to the time domain position of the PSSCH resources, and then a second timer is started. For details, reference may be made to the descriptions in examples one and two below. The second scheme is as follows: after receiving the HARQ feedback on the PSFCH resource, the TX UE starts a first timer according to the time domain position of the PSFCH resource, and then starts a second timer. For details, reference may be made to the description in example three below.

Besides, the embodiment of the present application also provides two schemes that do not involve the first timer and the second timer: in the third scheme, after sending Sidelink data on PSSCH resources, the TX UE monitors PDCCH according to the time domain position of the PSSCH resources. For details, the following description of example four can be referred to. In the fourth scheme, after receiving the HARQ feedback on the PSFCH resource, the TX UE monitors the PDCCH according to the time domain position of the PSFCH resource. For details, the description of the fifth example is given below.

For the sake of understanding, reference will first be made to a noun or a term referred to in the embodiments of the present application, which is also included as a part of the inventive content of the embodiments of the present application.

Terminal equipment

The terminal device may be referred to as a terminal for short, and is a device with a wireless transceiving function. The terminal equipment can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; can also be deployed on the water surface (such as a ship and the like); and may also be deployed in the air (e.g., airplanes, balloons, satellites, etc.). The terminal device may be a mobile phone (mobile phone), a tablet computer (pad), a computer with a wireless transceiving function, a Virtual Reality (VR) terminal device, an Augmented Reality (AR) terminal device, a wireless terminal device in industrial control (industrial control), a wireless terminal device in self driving (self driving), a wireless terminal device in remote medical (remote medical), a wireless terminal device in smart grid (smart grid), a wireless terminal device in transportation safety (transportation safety), a wireless terminal device in smart city (smart city), a wireless terminal device in smart home (smart home), and may further include a User Equipment (UE), and the like. The terminal device may also be a cellular phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device with wireless communication capability, a computing device or other processing device connected to a wireless modem, a vehicle-mounted device, a wearable device, a terminal device in a fifth generation (5G) network in the future, or a terminal device in a Public Land Mobile Network (PLMN) in the future, etc. A terminal device may also be sometimes referred to as a terminal, an access terminal device, a vehicle-mounted terminal device, an industrial control terminal device, a UE unit, a UE station, a mobile station, a remote terminal device, a mobile device, a UE terminal device, a wireless communication device, a UE agent, or a UE apparatus, etc. The terminal equipment may also be fixed or mobile. The embodiments of the present application do not limit this.

In the embodiment of the present application, the apparatus for implementing the function of the terminal may be a terminal; it may also be a device, such as a system-on-chip, capable of supporting the terminal to implement the function, which may be installed in the terminal. In the embodiment of the present application, the chip system may be composed of a chip, and may also include a chip and other discrete devices. In the technical solution provided in the embodiment of the present application, a device for implementing a function of a terminal is a terminal, and the terminal is a UE as an example, the technical solution provided in the embodiment of the present application is described.

Network device

The network device may be an access network device, and the access network device may also be referred to as a Radio Access Network (RAN) device, which is a device providing a wireless communication function for the terminal device. Access network equipment includes, for example but not limited to: a next generation base station (gbb) in 5G, an evolved node B (eNB), a Radio Network Controller (RNC), a Node B (NB), a Base Station Controller (BSC), a Base Transceiver Station (BTS), a home base station (e.g., home evolved node B or home node B, HNB), a Base Band Unit (BBU), a Transmission and Reception Point (TRP), a Transmission Point (TP), a mobile switching center, and the like. The access network device may also be a wireless controller, a Centralized Unit (CU), and/or a Distributed Unit (DU) in a Cloud Radio Access Network (CRAN) scenario, or the network device may be a relay station, an access point, a vehicle-mounted device, a wearable device, and a network device in a future 5G network or a network device in a future evolved PLMN network, and the like. The terminal device may communicate with multiple access network devices of different technologies, for example, the terminal device may communicate with an access network device supporting Long Term Evolution (LTE), may communicate with an access network device supporting 5G, and may also perform dual connectivity with an access network device supporting LTE and an access network device supporting 5G. The embodiments of the present application are not limited.

In the embodiment of the present application, the apparatus for implementing the function of the network device may be a network device; or may be a device, such as a system-on-chip, capable of supporting the network device to implement the function, and the device may be installed in the network device. In the technical solution provided in the embodiment of the present application, a device for implementing a function of a network device is a network device, and the network device is a base station, which is taken as an example, to describe the technical solution provided in the embodiment of the present application.

Three, side link (sidelink, SL)

The side link is used for communication between the terminal equipment and the terminal equipment, and a communication interface between the terminal equipment and the terminal equipment can be a PC5 interface. The channels involved in the edge link communication may include a physical edge link shared channel (PSCCH), a physical edge link control channel (PSCCH), and a physical edge link feedback channel (PSFCH).

The psch is used to carry side link data (SL data), and the PSCCH is used to carry side link control information (SCI), which may also be referred to as side link scheduling assignment (SL SA). The SL SA is information related to data scheduling, such as resource allocation and/or Modulation and Coding Scheme (MCS) for carrying the PSSCH. The PSFCH may be used to transmit side link feedback control information (SFCI). The side link feedback control information may include one or more of Channel State Information (CSI) and HARQ information. The HARQ information may include ACK or NACK, etc.

Four, Uu air interface

The Uu air interface may be referred to as Uu for short, and is used for communication between the terminal device and the network device. The transmission of the Uu air interface may include uplink transmission and downlink transmission.

The uplink transmission refers to that the terminal device sends information to the network device, and the information of the uplink transmission may be referred to as uplink information or an uplink signal. The uplink information or the uplink signal may include one or more of an uplink data signal, an uplink control signal, and a Sounding Reference Signal (SRS). A channel for transmitting uplink information or uplink signals is referred to as an uplink channel, and the uplink channel may include one or more of a Physical Uplink Shared Channel (PUSCH) and a Physical Uplink Control Channel (PUCCH). The PUSCH is used to carry uplink data, which may also be referred to as uplink data information. The PUCCH is used to carry Uplink Control Information (UCI) fed back by the terminal device. For example, the UCI may include one or more of Channel State Information (CSI), ACK, NACK, and the like fed back by the terminal device.

The downlink transmission refers to that the network device sends information to the terminal device, and the information of the downlink transmission may be downlink information or a downlink signal. The downlink information or the downlink signal may include one or more of a downlink data signal, a downlink control signal, a channel state information reference signal (CSI-RS), and a Phase Tracking Reference Signal (PTRS). A channel for transmitting downlink information or downlink signals is called a downlink channel, and the downlink channel may include one or more of a Physical Downlink Shared Channel (PDSCH) and a Physical Downlink Control Channel (PDCCH). The PDCCH is used to carry Downlink Control Information (DCI), and the PDSCH is used to carry downlink data (data), where the downlink data may also be referred to as downlink data information.

Five, Sidelink HARQ process

In the embodiment of the present application, the TX UE may set one Sidelink HARQ process for each Sidelink data, e.g., MAC PDU transmitted to the RX UE by the TX UE. That is, one Sidelink HARQ process is associated with one Sidelink data, which may be stored in the Sidelink HARQ buffer associated with the Sidelink HARQ process. A Sidelink HARQ process may maintain a state variable CURRENT _ SL _ TX _ NB that indicates the number of transmissions of Sidelink data associated with the Sidelink HARQ process. CURRENT _ SL _ TX _ NB may be initialized to 0.

The HARQ feedback resource of the Sidelink HARQ process associated with one Sidelink data may be used for the RX UE to send HARQ feedback of the Sidelink HARQ process to the TX UE. The HARQ feedback resource is a PSFCH resource, and may be used to carry the HARQ feedback sent by the RX UE to the TX UE. The HARQ feedback may be used to indicate whether the previous transmission of the Sidelink HARQ process was successfully received, i.e., whether the previous transmission of the Sidelink data associated with the Sidelink HARQ process was successfully received. If the HARQ feedback is ACK, the reception success of the previous transmission of the Sidelink HARQ process can be indicated; if the HARQ feedback is NACK, it may indicate that the reception of the previous transmission for the Sidelink HARQ process was unsuccessful.

Wherein, the TX UE is in an RRC connected state and is configured with a DRX cycle. The TX UE is in an active state for a period of time from the start time of the DRX cycle, and can monitor and receive one PDCCH. The PDCCH is used to schedule one transmission of the Sidelink data. The one transmission may be an initial transmission of the Sidelink data, or may be a retransmission of the Sidelink data, such as a second transmission, a third transmission, or the like.

Here, the period of time from the start time of the DRX cycle may be "On Duration" of the DRX cycle, or may be an extended "On Duration" formed after the DRX-inactivity timer is turned On. For the extension of "On Duration", reference may be made to the related description of fig. 2B above. That is, the start time of the period of time is the start time of the DRX cycle, and the Duration of the period of time is equal to or greater than the Duration of the "On Duration".

The Sidelink data referred to in the embodiments of the present application may be data of a Medium Access Control (MAC) layer, for example, without limitation, a MAC Protocol Data Unit (PDU), and the like. In the communication method provided in the embodiment of the present application, the TX UE may be referred to as a first terminal device, and the RX UE may be referred to as a second terminal device. The TX UE and the RX UE may use a unicast transmission method, a multicast transmission method, or the like, which is not limited. When the multicast transmission mode is adopted, the number of RX UEs may be one or more.

It should be noted that in the description of the present application, "/" indicates a relationship that the objects associated before and after are an "or" unless otherwise specified, for example, a/B may indicate a or B; in the present application, "and/or" is only an association relationship describing an associated object, and means that there may be three relationships, for example, a and/or B, and may mean: a exists alone, A and B exist simultaneously, and B exists alone, wherein A and B can be singular or plural. Also, in the description of the present application, "a plurality" means two or more than two unless otherwise specified. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, a-b, a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple. In addition, in order to facilitate clear description of technical solutions of the embodiments of the present application, in the embodiments of the present application, terms such as "first" and "second" are used to distinguish the same items or similar items having substantially the same functions and actions. Those skilled in the art will appreciate that the terms "first," "second," etc. do not denote any order or quantity, nor do the terms "first," "second," etc. denote any order or importance.

The embodiment of the present application provides a communication method, which may be used for the first scheme. It is understood that the first terminal device and the second terminal device in the method may be terminal devices, and may also be components (e.g., chips, circuits, or others) in the terminal devices. The network device may be an access network device, such as a base station or the like. The method specifically comprises the following steps:

the network equipment sends first DCI to first terminal equipment, wherein the first DCI is used for scheduling initial transmission or retransmission of the first terminal equipment Sidelink data. And the first terminal equipment transmits the Sidelink data to the second terminal equipment by utilizing the PSSCH resource according to the scheduling of the first DCI. The first terminal equipment determines a first time domain position according to the time domain position of the PSSCH resource, and starts a first timer at the first time domain position. And then starting a second timer when the first timer is over time.

Example one

In this embodiment of the present application, for each Sidelink HARQ process configured as a HARQ retransmission mechanism based on HARQ feedback of a Sidelink, a first terminal device maintains two timers for each Sidelink HARQ process: a first timer and a second timer. Alternatively, the above process may also be described as the first terminal device associating two timers for each Sidelink HARQ process, namely the first timer and the second timer. Illustratively, the first timer may be named: drx-HARQ-RTT-TimerSL; the second timer may be named drx-retransmission timersl. During the running of the second timer, the first terminal device monitors the PDCCH. The first timer and the second timer may be named otherwise, which is not limited in this embodiment of the application.

Fig. 3 shows a specific flow of the communication method according to the first embodiment.

S301, RRC connection is established between the first terminal device and the network device.

After the RRC connection is established, the first terminal device enters an RRC connected state.

S302, a Sidelink is established between the first terminal device and the second terminal device.

After the Sidelink is established, the first terminal device transmits data to the second terminal device through the Sidelink.

S303, the network device configures a DRX cycle for the first terminal device in the RRC connected state.

The DRX cycle consists of "On Duration" and "Opportunity for DRX": in the "On Duration", the first terminal device monitors and receives the PDCCH (active state); within "opportunity DRX", the first terminal device does not monitor the PDCCH (dormant state).

S304, the network device configures a timer for the first terminal device in the RRC connected state: drx-InactivityTimer, drx-HARQ-RTT-TimerSL, drx-retransmission TimerSL. In the embodiment of the present application, drx-HARQ-RTT-TimerSL may be referred to as a first timer, and drx-retransmission TimerSL may be referred to as a second timer.

Not limited to that shown in fig. 3, S302 may also be performed before S301. The timing sequence of S302 and S301, S303, and S304 is not limited in this application.

The first terminal device may also send a resource scheduling request to the network device to request the network device to schedule transmission resources for the Sidelink data transmission. Typically, the resource scheduling request may carry a buffer status report (buffer status report) to indicate how much Sidelink data is to be transmitted by the first terminal device on the Sidelink. Accordingly, after the network device receives the resource scheduling request, the network device may transmit scheduling resources for the Sidelink, and issue the scheduled Sidelink resources in the PDCCH. The first terminal device may learn the Sidelink resource scheduled by the network device by monitoring the PDCCH.

S305, the first terminal device may monitor and receive the PDCCH1 sent by the network device. PDCCH1 may indicate the Sidelink resource scheduled by the network device for the ith transmission of a certain Sidelink HARQ process (e.g. Sidelink HARQ process a), that is, PDCCH1 may be used to schedule the ith transmission of the Sidelink HARQ process a.

The Sidelink HARQ process a may associate data a. The Sidelink HARQ process a may be used for the first terminal device to transmit data a to the second terminal device on the Sidelink established in S302. The Sidelink HARQ process a may maintain one state variable: CURRENT _ SL _ TX _ NB. Where CURRENT _ SL _ TX _ NB may indicate the number of transmission of data a, CURRENT _ SL _ TX _ NB may be initialized to 0.

The initial value of the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a may be set to 0. The first terminal device may add 1 to CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a whenever the first terminal device monitors and receives a PDCCH for scheduling transmissions (including initial transmissions, retransmissions) of the Sidelink HARQ process a. The PDCCH used to schedule transmission of the Sidelink HARQ process a may indicate the transmission resources allocated by the network device to the Sidelink HARQ process a.

PDCCH1 may carry the following information: SL grant1, NDI, ID of Sidelink HARQ process a. Wherein, the SL grant1 may indicate resources scheduled by the network device for the ith transmission of the Sidelink HARQ process a. The NDI may indicate whether the ith transmission of the Sidelink HARQ process a scheduled by PDCCH1 is an initial transmission or a retransmission. Optionally, in a more specific implementation, the PDCCH1 may carry DCI1, and the DCI1 may carry information such as the IDs of the SL grant1, ND1, and the Sidelink HARQ process a.

Specifically, the first terminal device may determine whether the ith transmission of the Sidelink HARQ process a is an initial transmission or a retransmission by determining whether the NDI in the PDCCH1 is inverted (toggled): if the value of the NDI in the PDCCH1 is reversed compared with the NDI in the PDCCH of the Sidelink HARQ process a scheduled for the last time, the ith transmission of the Sidelink HARQ process a is represented as initial transmission; otherwise, it indicates that the ith transmission of the Sidelink HARQ process a is a retransmission. By NDI reversal, it may be meant that the value of NDI changes from 0 to 1, or from 1 to 0.

After receiving PDCCH1, the first terminal device may transmit data a to the second terminal device through a Sidelink HARQ process a on the psch resource indicated by PDCCH1, that is, perform the ith transmission of data a S306. Accordingly, the second terminal device may receive the data a transmitted by the first terminal device on the psch resource indicated by PDCCH 1.

Specifically, the second terminal device may know, by monitoring the PSCCH, which PSCCH resources the first terminal device may transmit data a on. Because, after receiving PDCCH1, the first terminal device may transmit Sidelink Control Information (SCI) on the PSCCH. The second terminal device may receive the SCI by listening to the PSCCH. The SCI is used to instruct the first terminal device on the resources to transmit data a.

S307, the first terminal device starts a first timer according to the time domain position of the pscch resource for the ith transmission of the data a.

The psch resources include time domain resources and frequency domain resources. The time domain resource of the psch for the ith transmission of data a may occupy one or more time units. The first time domain position for starting the first timer may be the first time unit after the last time unit in the time domain resource of the psch for the ith transmission of the data a. Alternatively, the first time domain position for starting the first timer may be a time unit which is offset from the last time domain unit in the time domain resource of the ith transmission psch by a first time domain offset. The first time domain offset may include one or more time units.

Illustratively, the time units may be symbols, slots, etc. The timing units of the two timers and the first time domain offset may be symbols, time slots, or absolute time units (e.g., milliseconds). The length of the symbol, slot may depend on the parameter set Numerology of the bandwidth part (BWP) of the Sidelink for transmitting the first data, such as the subcarrier space (SCS). Without being limited thereto, the length of the symbols, time slots may also depend on the parameter set Numerology, such as SCS, of the uplink bandwidth part BWP, where the first terminal device sends HARQ feedback to the network device.

In one possible implementation manner, the first terminal device may determine the first time domain position according to the time domain resource position of the psch resource performing the i-th transmission of the data a and the first time domain offset. In the first time domain position, a first timer is started. The first time domain offset may be protocol specified, or configured by the network device, or implemented internally in the first terminal device, without limitation. For example, one possible implementation manner is that the network device may carry the configuration of the first time domain offset through SL-psch-Config signaling. In the embodiment of the present application, the configuration mode, the configuration signaling, and the naming of the first time domain offset are not limited. The first time domain position may be a time domain offset from the time domain resource end position of the psch resource on which the ith transmission of data a is made. When the first time domain offset is 0, the first terminal device may start the first timer at the first time unit after the ith transmission of data a is sent on the pscch resource.

In another possible implementation manner, without defining the concept of the first time domain offset, the first terminal device uses the first time unit after the time domain resource end position of the pscch resource for the ith transmission of the data a as the first time domain position, and starts the first timer at the first time domain position.

Optionally, in addition to the above situation, when the first terminal device starts the first timer, the following condition may be satisfied: the first terminal equipment determines whether the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a indicates that the transmission frequency of the Sidelink HARQ process a exceeds the maximum transmission frequency or a preset transmission frequency.

When the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a is smaller than the maximum transmission time or a preset transmission time, the first terminal device starts a first timer at a first time domain position; otherwise, at the first time domain position, the first timer is not started any more. It should be noted that, when the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a is equal to the maximum transmission time or the preset transmission time, the first timer may be started, or the first timer may not be started, which is not limited. The maximum transmission times and the preset transmission times may be specified by a protocol, or configured by a network device, or implemented inside the first terminal device, without limitation. It can be understood that the number of transmissions of the Sidelink HARQ process a described above includes the initial and retransmission times of the Sidelink HARQ process a. For example, the transmission number of the Sidelink HARQ process a may be considered to be 3, where the Sidelink HARQ process a is initially transmitted 1 time and is retransmitted 2 times. If the maximum number of transmissions is 5, the number of transmissions of the Sidelink HARQ process a may be smaller than the maximum number of transmissions. At this time, in the first time domain position, the first timer may be started.

And S308, the first terminal equipment starts a second timer according to the first timer.

Specifically, when the first timer times out, the first terminal device may start the second timer. During the running of the second timer, the first terminal device monitors the PDCCH.

S309, the first terminal device may stop the second timer when monitoring and receiving PDCCH 2.

In one possible implementation, the resource indicated by PDCCH2 may be a resource scheduled by the network device for the i +1 th transmission of the Sidelink HARQ process a, that is, PDCCH2 may be used to schedule the i +1 th transmission of data a of the Sidelink HARQ process a. PDCCH2 may carry the following information: SL grant 2, NDI, ID of Sidelink HARQ process a. Illustratively, SL grant 2 is the resource scheduled by the network device for the i +1 th transmission of the Sidelink HARQ process a. The NDI may indicate whether the i +1 st transmission of the Sidelink HARQ process a scheduled by PDCCH2 is an initial transmission or a retransmission. The i +1 th transmission is a retransmission relative to the ith transmission, which is the previous transmission of the i +1 th transmission.

In another possible implementation, the resource indicated by PDCCH2 may be a resource scheduled by the network device for initial transmission of the Sidelink HARQ process a. At this time, the Sidelink HARQ process a associates new data, such as data b. I.e. the Sidelink HARQ process a has been used for the first terminal device to transmit new data instead of data a. In general, this possible situation may occur when the transmission of data a has reached a maximum number of transmissions (e.g., 5). In this case, in subsequent S310, the first terminal device may also stop the second timer.

After receiving PDCCH2, the first terminal device may transmit data a to the second terminal device through the Sidelink HARQ process a on the resource indicated by PDCCH2, that is, perform i +1 th transmission of data a S310. Accordingly, the second terminal device may receive the data a transmitted by the first terminal device on the resource indicated by PDCCH 2.

It can be seen that in the first embodiment, in the first time domain position, the first terminal device may start the first timer, and when the first timer times out, the second timer is started. That is to say, after the data of the Sidelink HARQ process a is sent, during the running period of the second timer, the first terminal device is in an active state, and can monitor and receive the PDCCH which is sent by the network device during the active state and used for scheduling the retransmission of the Sidelink HARQ process a. Thus, the retransmission efficiency of the Sidelink HARQ process a can be improved, and the increase of the delay of the Sidelink data retransmission is avoided.

It should be noted that the above scheme may be applied to point-to-point unicast transmission, may also be applied to point-to-multipoint multicast transmission, and may also be applied to the case where the PSFCH resource is configured, or may also be applied to the case where the PSFCH resource is not configured.

The embodiment of the present application also provides another possible implementation manner for the case that the PSFCH resource is not configured. Similar to the above method, except that the first terminal device may default the HARQ feedback for the ith transmission of data a to ACK. The above-mentioned flow of S307 may be replaced with: the first terminal device does not start the first timer any more at the first time domain position. As to the way of determining the first time domain position by the first terminal device, refer to the above description, and will not be described.

For the case of configuring PSFCH resources, embodiment (two) of the present application provides another possible implementation manner, which may correspond to the first scheme described above, and the difference from embodiment (one) described above is that: when the first timer times out, the first terminal equipment does not directly start the second timer any more. Whether the first terminal device starts the second timer also needs to consider HARQ feedback fed back by the second terminal device through the PSFCH resource.

(II) example II

In this embodiment, for each Sidelink HARQ process configured as a HARQ retransmission mechanism based on HARQ feedback of a Sidelink, the first terminal device maintains two timers for each Sidelink HARQ process: a first timer and a second timer. Alternatively, the above process may also be described as the first terminal device associating two timers for each Sidelink HARQ process, namely the first timer and the second timer. Illustratively, the first timer may be named: drx-HARQ-RTT-TimerSL; the second timer may be named drx-retransmission timersl. During the running of the second timer, the first terminal device monitors the PDCCH. The first timer and the second timer may be named otherwise, which is not limited in this application.

Fig. 4 shows a specific flow of the communication method provided in the second embodiment.

S401, RRC connection is established between the first terminal device and the network device.

S402, a Sidelink is established between the first terminal device and the second terminal device.

S403, the network device configures DRX cycle for the first terminal device in RRC connection state.

The DRX cycle consists of "On Duration" and "Opportunity for DRX": in the "On Duration", the first terminal device monitors and receives the PDCCH (active state); within "opportunity DRX", the first terminal device no longer monitors the PDCCH (dormant state).

S404, the network device configures a timer for the first terminal device in the RRC connected state: drx-InactivityTimer, drx-HARQ-RTT-TimerSL, drx-retransmission TimerSL. In the embodiment of the present application, drx-HARQ-RTT-TimerSL may be referred to as a first timer, and drx-retransmission TimerSL may be referred to as a second timer.

Not limited to that shown in fig. 4, S402 may also be performed before S401. The timing sequence of S402, S401, S403, and S404 is not limited in this application.

Optionally, the first terminal device may further send a resource scheduling request to the network device, so as to request the network device to schedule transmission resources for the Sidelink data transmission. Typically, the resource scheduling request may carry a buffer status report (buffer status report) to indicate how much Sidelink data the first terminal device has on the Sidelink to send. Accordingly, after receiving the resource scheduling request, the network device may transmit a scheduling resource for the Sidelink, and issue the scheduled resource in the PDCCH. The first terminal device may learn the resources scheduled by the network device by monitoring the PDCCH.

S405, the first terminal device may monitor and receive the PDCCH1 sent by the network device. PDCCH1 may indicate a resource scheduled by the network device for the ith transmission of a certain Sidelink HARQ process (e.g., Sidelink HARQ process a), that is, PDCCH1 may be used to schedule the ith transmission of the Sidelink HARQ process a.

Optionally, the Sidelink HARQ process a may associate data a. The Sidelink HARQ process a may be used for the first terminal device to transmit data a to the second terminal device on the Sidelink established in S402. The Sidelink HARQ process a may maintain one state variable: CURRENT _ SL _ TX _ NB. For example, CURRENT _ SL _ TX _ NB may indicate the number of transmission of data a, and CURRENT _ SL _ TX _ NB may be initialized to 0.

PDCCH1 may carry the following information: SL grant1, NDI, ID of Sidelink HARQ process a. Illustratively, SL grant1 may indicate resources scheduled by the network device for the ith transmission of the Sidelink HARQ process a. The NDI may indicate whether the ith transmission of the Sidelink HARQ process a scheduled by PDCCH1 is an initial transmission or a retransmission.

S406, after receiving PDCCH1, the first terminal device may transmit data a to the second terminal device through a Sidelink HARQ process a on the psch resource indicated by PDCCH1, that is, perform the ith transmission of data a. Accordingly, the second terminal device may receive the data a transmitted by the first terminal device on the psch resource indicated by PDCCH 1.

S407, the first terminal device starts a first timer according to the time domain position of the pscch resource for the ith transmission of the data a. As to the manner of starting the first timer by the first terminal device, reference may be made to the description in fig. 3, and a description thereof will not be provided herein.

S408, the first terminal device receives HARQ feedback of ith transmission of the Sidelink HARQ process a on a PSFCH resource, where the PSFCH resource may be used to carry HARQ feedback of ith transmission of the Sidelink HARQ process a sent to the first terminal device by the second terminal device.

S409, the first terminal device determines the HARQ feedback of the ith transmission of the Sidelink HARQ process a. The HARQ feedback of the ith transmission of the Sidelink HARQ process a is used to indicate whether the reception of the ith transmission of the data a is successful or not. The following description will be made as to how to determine whether the reception of the ith transmission of the data a is successful or not.

S410, the first terminal device starts or does not start or stop the second timer according to the HARQ feedback of the ith transmission of the Sidelink HARQ process a.

Specifically, in one possible case, before the first timer expires, the first terminal device may determine HARQ feedback for the ith transmission of the Sidelink HARQ process a. If the first terminal device determines that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is NACK, that is, determines that the reception of the ith transmission of the Sidelink HARQ process a is unsuccessful, the first terminal device may start the second timer when the first timer expires. During the running of the second timer, the first terminal device monitors the PDCCH. If the first terminal device determines that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is ACK, that is, it determines that the reception of the ith transmission of the Sidelink HARQ process a is successful, the first terminal device directly stops the first timer, and there is no longer a case that the first timer is overtime, and the second timer is not started, or the first terminal device may not stop the first timer, and only when the first timer is overtime, the second timer is not started.

In another possible case, the first terminal device may not determine the HARQ feedback for the ith transmission of the Sidelink HARQ process a before the first timer expires. The second timer has already been started due to the first timer being out of time, and during the running of the second timer, if the first terminal device determines that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is NACK, i.e. determines that the reception of the ith transmission of the Sidelink HARQ process a is not successful, the first terminal device does not stop the second timer. During the running of the second timer, the first terminal device monitors the PDCCH. During the running of the second timer, if the first terminal device determines that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is ACK, that is, determines that the reception of the ith transmission of the Sidelink HARQ process a is successful, the first terminal device directly stops the second timer and does not monitor the PDCCH any more.

S411, when monitoring and receiving PDCCH2, the first terminal device may stop the second timer.

In a possible implementation manner, the resource indicated by PDCCH2 may be a resource scheduled by the network device for the i +1 th transmission of the Sidelink HARQ process a, that is, PDCCH2 may be used to schedule the i +1 th transmission of the Sidelink HARQ process a. PDCCH2 may carry the following information: SL grant 2, NDI, ID of Sidelink HARQ process a. Illustratively, SL grant 2 is the resource scheduled by the network device for the i +1 th transmission of the Sidelink HARQ process a. The NDI may indicate whether the i +1 st transmission of the Sidelink HARQ process a scheduled by PDCCH2 is an initial transmission or a retransmission. The i +1 th transmission is a retransmission relative to the ith transmission, which is the previous transmission of the i +1 th transmission. The second timer may be stopped when the first terminal device monitors and receives PDCCH 2.

In another possible implementation, the resource indicated by PDCCH2 may be a resource scheduled by the network device for initial transmission of the Sidelink HARQ process a. At this time, the Sidelink HARQ process a associates new data, such as data b. I.e. the Sidelink HARQ process a has been used for the first terminal device to transmit new data instead of data a. In general, this possible situation may occur when the transmission of data a has reached a maximum number of transmissions (e.g., 5). In this case, the first terminal device may also stop the second timer.

After receiving PDCCH2, the first terminal device may transmit data a to the second terminal device through the Sidelink HARQ process a on the resource indicated by PDCCH2, that is, perform i +1 th transmission of data a S412. Accordingly, the second terminal device may receive the data a transmitted by the first terminal device on the resource indicated by PDCCH 2.

It can be seen that, in the second embodiment, in the first time domain position, the first terminal device may start the first timer, and start the second timer according to the HARQ feedback of the ith transmission of the Sidelink HARQ process a, or does not start or stop the second timer. Specifically, before the first timer expires, the first terminal device may determine the HARQ feedback of the ith transmission of the Sidelink HARQ process a. If the first terminal device determines that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is NACK, the first terminal device may start the second timer when the first timer expires. And if the first terminal equipment determines that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is ACK, the first terminal equipment does not start the second timer any more. Before the first timer is overtime, the first terminal equipment cannot determine the HARQ feedback of the ith transmission of the Sidelink HARQ process a, and during the running period of the second timer, if the first terminal equipment determines that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is NACK, the first terminal equipment does not stop the second timer. During the running of the second timer, if the first terminal device determines that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is ACK, the first terminal device directly stops the second timer. Compared with the scheme that the second timer is directly started when the first timer is overtime, the power consumption of the first terminal equipment can be reduced.

In the first and second embodiments, the data transmission of the Sidelink is scheduled once by one PDCCH as an example. In the embodiment of the present application, one PDCCH may also schedule multiple transmissions of one Sidelink data, for example, 2 times or 3 times. When one PDCCH schedules multiple transmissions of data of one sildenk, one PDCCH may indicate multiple pscch resources. In this embodiment of the present application, when one PDCCH schedules multiple transmissions of one Sidelink data, in S307 or S407, a first time domain position is determined according to a time domain position of a pscch resource, and a first timer is started. The method can be specifically as follows: determining a first time domain position according to a time domain position of a PSSCH resource transmitting a first repetition (repetition), starting a first timer, and specifically, how to determine the first time domain position, refer to the description in S307 or S407, which is not described again. Of course, the above is only an exemplary illustration, and the first time domain position may also be determined according to the time domain position of the last repeated pscch resource, the first timer is started, or even the time domain position of any repeated pscch resource, the first time domain position is determined, the first timer is started, and the like, without limitation. The first repetition refers to a first transmission of a plurality of transmissions of one Sidelink data scheduled by the PDCCH.

For the case of configuring PSFCH resources, an embodiment (three) of the present application provides another possible implementation manner, which may correspond to the second scheme described above, and the scheme may be: the network equipment sends first DCI to the first terminal equipment, wherein the first DCI is used for scheduling the first terminal equipment to carry out initial transmission or retransmission of the Sidelink data. And the first terminal equipment transmits the Sidelink data to the second terminal equipment by utilizing the PSSCH resource according to the scheduling of the first DCI. And the second terminal equipment sends HARQ feedback to the first terminal equipment after receiving the Sidelink data. And the first terminal equipment receives the HARQ feedback by using the PSFCH resource. And starting or not starting the first timer according to the HARQ feedback and the time domain position of the PSFCH resource. Further, in the case of starting the first timer, when the first timer times out, the second timer is started. And during the running period of the second timer, the first terminal equipment is in an active state and monitors the PDCCH.

(III) example III

Fig. 5 shows a specific flow of the communication method provided in the third embodiment.

S501, RRC connection is established between the first terminal device and the network device.

S502, a Sidelink is established between the first terminal device and the second terminal device.

S503, the network device configures DRX cycle for the first terminal device in RRC connection state.

The DRX cycle consists of "On Duration" and "Opportunity for DRX": in the "On Duration", the first terminal device monitors and receives the PDCCH (active state); within "opportunity DRX", the first terminal device does not receive PDCCH to save power consumption (sleep state).

S504, the network device configures a timer for the first terminal device in the RRC connected state: drx-InactivityTimer, drx-HARQ-RTT-TimerSL, drx-retransmission TimerSL. In the embodiment of the present application, drx-HARQ-RTT-TimerSL may be referred to as a first timer, and drx-retransmission TimerSL may be referred to as a second timer

Not limited to that shown in fig. 5, S502 may also be executed before S501. The timing sequence of S502 and S501, S503, S504 is not limited in this application.

S505, the first terminal device may monitor and receive the PDCCH1 sent by the network device. PDCCH1 may indicate a resource scheduled by the network device for the ith transmission of a certain Sidelink HARQ process (e.g., Sidelink HARQ process a), that is, PDCCH1 may be used to schedule the ith transmission of the Sidelink HARQ process a.

Optionally, the Sidelink HARQ process a may associate data a. The Sidelink HARQ process a may be used for the first terminal device to transmit data a to the second terminal device on the Sidelink established in S502. The Sidelink HARQ process a may maintain one state variable: CURRENT _ SL _ TX _ NB. For example, CURRENT _ SL _ TX _ NB may indicate the number of transmission of data a, and CURRENT _ SL _ TX _ NB may be initialized to 0.

Further, the initial value of the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a may be set to 0. The first terminal device may add 1 to CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a whenever the first terminal device monitors and receives a PDCCH for scheduling transmissions (including initial transmissions, retransmissions) of the Sidelink HARQ process a. The PDCCH used to schedule transmission of the Sidelink HARQ process a may indicate the transmission resources allocated by the network device to the Sidelink HARQ process a.

S506, after receiving PDCCH1, the first terminal device may transmit data a to the second terminal device through a Sidelink HARQ process a on the psch resource indicated by PDCCH1, that is, perform the ith transmission of data a. Accordingly, the second terminal device may receive the data a transmitted by the first terminal device on the psch resource indicated by PDCCH 1.

Specifically, the second terminal device may know, by monitoring the PSCCH, which PSCCH resources the first terminal device may transmit data a on. Because, after receiving PDCCH1, the first terminal device may send SCI on the PSCCH. The second terminal device may receive the SCI by listening to the PSCCH. The SCI is used to instruct the first terminal device on the resources to transmit data a.

S507, the first terminal device receives HARQ feedback of ith transmission of the Sidelink HARQ process a on a PSFCH resource, where the PSFCH resource may be used to carry HARQ feedback of ith transmission of the Sidelink HARQ process a sent to the first terminal device by the second terminal device.

S508, the first terminal device determines the ith transmission HARQ feedback of the Sidelink HARQ process a. The ith transmission HARQ feedback of the Sidelink HARQ process a is used to indicate whether the reception of the ith transmission of the data a is successful or not. The following description will be made as to how to determine whether the reception of the ith transmission of the data a is successful or not.

S509, the first terminal device starts or does not start the first timer according to the ith transmission HARQ feedback of the Sidelink HARQ process a and the time domain position of the PSFCH resource receiving the ith transmission HARQ feedback of the Sidelink HARQ process a.

Specifically, in a possible case, if the first terminal device determines that HARQ feedback of ith transmission of the Sidelink HARQ process a is NACK, that is, it determines that reception of the ith transmission of the Sidelink HARQ process a is unsuccessful, the first terminal device starts a first timer at the second time domain position; if the first terminal device determines that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is ACK, that is, determines that the reception of the ith transmission of the Sidelink HARQ process a is successful, the first terminal device does not start the first timer at the second time domain position. How to determine the second time domain position has the following possible implementation manners:

the PSFCH resources include time domain resources and frequency domain resources. The time domain resource of the PSFCH receiving the HARQ feedback for the ith transmission of the Sidelink HARQ process a may occupy one or more time units. The second time domain position for starting the first timer may be a first time unit after a last time unit in the time domain resources of the PSFCH resources for receiving the HARQ feedback of the ith transmission of the Sidelink HARQ process a. Or, the time unit may be a second time domain offset from the last time unit in the time domain resources of the PSFCH resources receiving the HARQ feedback of the ith transmission of the Sidelink HARQ process a. The second time domain offset may include one or more time cells.

In a possible implementation manner, the first terminal device may determine the second time domain position according to the time domain resource position of the PSFCH resource receiving the HARQ feedback of the ith transmission of the Sidelink HARQ process a and the second time domain offset. At a second time domain location, a first timer is started. The second time domain offset may be predefined by a protocol, or configured by the network device, or implemented inside the first terminal device, for example, a possible implementation manner is that the network device carries the configuration of the second time domain offset through SL-PSFCH-Config signaling, and a specific configuration manner and configuration signaling of the second time domain offset and a name of the second time domain offset are not limited. The second time domain position may be a time domain offset from a time domain resource end position of a PSFCH resource receiving HARQ feedback for an ith transmission of the Sidelink HARQ process a. When the second time domain offset is 0, the first terminal device starts the first timer at the first time unit after receiving the HARQ feedback of the ith transmission of the data a on the PSFCH resource. Alternatively, it may be described that the first terminal device starts the first timer at the first time unit after receiving the PSFCH resource end position of the HARQ feedback of the ith transmission of the Sidelink HARQ process a.

In another possible implementation manner, without defining the concept of the second time domain offset, the first terminal device uses a first time unit after receiving the time domain resource end position of the PSFCH resource of the HARQ feedback of the ith transmission of the Sidelink HARQ process a as the second time domain position, and starts the first timer at the second time domain position.

Optionally, in addition to the above situation, when the first terminal device starts the first timer, the following condition may be satisfied: the first terminal equipment determines that a state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a indicates the transmission times of the Sidelink HARQ process a; whether the maximum number of transmissions or the preset number of transmissions is exceeded.

When the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a is smaller than the maximum transmission time or the preset transmission time, the first terminal device starts or does not start the first timer at the second time domain position according to the ith transmission HARQ feedback of the Sidelink HARQ process a; for example, if the HARQ feedback of the ith transmission of the Sidelink HARQ process a is ACK, that is, it is determined that the ith transmission of the Sidelink HARQ process a is successfully received, the first terminal device does not start the first timer at the second time domain position. And if the HARQ feedback of the ith transmission of the Sidelink HARQ process a is NACK, that is, the ith transmission of the Sidelink HARQ process a fails, the first terminal equipment starts a first timer at a second time domain position. And when the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a is greater than the maximum transmission time or the preset transmission time, the first terminal device does not start the first timer any more at the second time domain position. It should be noted that, when the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a is equal to the maximum transmission time or the preset transmission time, the first timer may be started, or the first timer may not be started, which is not limited. The maximum transmission times and the preset transmission times may be specified by a protocol, or configured by a network device, or implemented inside the first terminal device, without limitation.

S510, if the first timer is started, and when the first timer times out, the first terminal device may start a second timer. During the running of the second timer, the first terminal device monitors the PDCCH.

S511, the first terminal device may stop the second timer when monitoring and receiving the PDCCH 2.

In a possible implementation manner, the resource indicated by PDCCH2 may be a resource scheduled by the network device for the i +1 th transmission of the Sidelink HARQ process a, that is, PDCCH2 may be used to schedule the i +1 th transmission of the Sidelink HARQ process a. The i +1 th transmission is a retransmission relative to the ith transmission, which is the previous transmission of the i +1 th transmission. The second timer may be stopped when the first terminal device monitors PDCCH 2.

S512, after receiving PDCCH2, the first terminal device may transmit data a to the second terminal device through the Sidelink HARQ process a on the resource indicated by PDCCH2, that is, perform i +1 th transmission of data a. Accordingly, the second terminal device may receive the data a transmitted by the first terminal device on the resource indicated by PDCCH 2.

It can be seen that, in the third embodiment, the first terminal device starts or does not start the first timer according to the ith transmission HARQ feedback of the Sidelink HARQ process a and the time domain position of the PSFCH resource receiving the ith transmission HARQ feedback of the Sidelink HARQ process a. For example, when the ith transmission HARQ feedback of the Sidelink HARQ process a is ACK, the first terminal device may not start the first timer any more. And when the ith transmission HARQ feedback of the Sidelink HARQ process a is NACK, the first terminal equipment starts a first timer, and when the first timer is over, a second timer is started. And during the running period of the second timer, the first terminal device is in an active state and can monitor and receive the PDCCH which is sent by the network device during the active state and used for scheduling the retransmission of the Sildelink process a. Therefore, the retransmission efficiency of the Sidelink process a can be improved, and the increase of the retransmission delay of the Sidelink data is avoided. Further, the power consumption of the first terminal device can be reduced.

In the following description, the process of the first terminal device determining that the HARQ feedback of the Sidelink HARQ process a is ACK or NACK will be discussed continuously: for ease of understanding, the following harq feedback for several communication schemes will be first introduced.

1. Point-to-point unicast communication mode

For the point-to-point unicast communication mode, the RX UE may feed back HARQ to the TX UE every time it receives one data packet sent by the TX UE. Illustratively, if the RX UE successfully receives the data packet and decodes without error, an ACK is fed back to the TX UE, otherwise a NACK is fed back.

2. Point-to-multipoint multicast communication.

For the point-to-multipoint multicast communication method, HARQ feedback methods are divided into two types. The first is a NACK-only feedback approach. The RX UEs within a group only feed back NACKs to TX UEs and not ACKs. When the TX UE receives at least one NACK, the HARQ feedback for this packet is considered to be a NACK. The HARQ feedback for this packet is considered to be an ACK if the TX did not receive the HARQ feedback. The second is an ACK-NACK HARQ feedback method, and RX UEs in one group may feed back ACK or NACK to TXUEs. The HARQ feedback for this data packet is considered to be ACK only if the TX UE receives HARQ feedback for all RX UEs in the group and is all ACK, otherwise it is considered to be NACK. Specifically, the NACK-only feedback manner may refer to NACK-only feedback based on location (distance-based), or may refer to NACK-only feedback not based on location (non-distance-based). For example, the NACK-only feedback based on location indicates that the RX UE within a location range can perform NACK-only feedback only when the TX UE can obtain location information, so as to avoid unnecessary retransmission caused by receiving NACK sent by a distant RX UE.

HARQ feedback Properties of SL MAC PDUs

Currently, configuring the HARQ attribute of a downlink logical channel (SL LCH) through an SL-HARQ-Feedback-Enabled parameter is supported. If the SL-HARQ-Feedback-Enabled parameter of one SL LCH is configured to Enable, it indicates that the SL LCH supports HARQ Feedback. If the SL-HARQ-Feedback-Enabled parameter of a SL LCH is configured to Disable, it indicates that the SL LCH does not support HARQ Feedback.

When TX UE is packaged, a logical channel multiplexing (logical channel multiplexing) process cannot multiplex SL LCHs with different HARQ attributes into one Media Access Control (MAC) Protocol Data Unit (PDU). When the HARQ attribute of one MAC PDU is enable, the TX UE may set the HARQ feedback bit to enable in the SCI, and request the RX UE to perform HARQ feedback on the MAC PDU. And when the HARQ attribute of one MAC PDU is disabled, the TX UE may set the HARQ feedback bit to disabled in the SCI, requesting the RX UE not to perform HARQ feedback on the MAC PDU.

(1) In any of the following cases, the first terminal device may determine that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is NACK, that is, may determine that the reception of the ith transmission of the Sidelink HARQ process a is unsuccessful:

case 1: in the unicast communication mode, the HARQ feedback received by the first terminal device and sent by the second terminal device is NACK.

Specifically, the HARQ feedback is used to indicate whether the ith transmission of data a associated with the Sidelink HARQ process a is successfully received by the second terminal device. When the HARQ feedback is NACK, it may indicate that the second terminal device has not successfully received the ith transmission of data a associated with the Sidelink HARQ process a. The second terminal device does not successfully receive the ith transmission of data a associated with the Sidelink HARQ process a, and the reasons may include but are not limited to: the second terminal device does not successfully decode the data a.

Case 2: in a unicast communication mode or an ACK-NACK feedback mode of a multicast communication mode, the first terminal device does not receive HARQ feedback sent by the second terminal device.

Specifically, the first terminal device does not receive the HARQ feedback of the ith transmission of the data a associated with the Sidelink HARQ process a sent by the second terminal device, which may specifically be that the first terminal device does not receive the HARQ feedback of the ith transmission of the data a associated with the Sidelink HARQ process a sent by the second terminal device on the PSFCH resource associated with the Sidelink HARQ process a. The PSFCH resource associated with the Sidelink HARQ process a may be configured by the network device.

Case 3: the first terminal device does not transmit the Sidelink data to the second terminal device on the psch resource.

Specifically, the psch resource is a resource scheduled by the network device for the ith transmission of the Sidelink HARQ process a. The reason for the occurrence of case 3 may be a resource conflict, i.e. the first terminal device transmits other data on the psch resource than data a. Case 3 is applicable to NACK-only feedback or ACK-NACK feedback in a unicast communication scheme or a multicast communication scheme.

Case 4: in a NACK-only feedback mode of a multicast communication mode, the first terminal device receives at least one NACK feedback for the ith transmission of the Sidelink HARQ process a.

Specifically, in a NACK-only feedback mode of a multicast communication mode, the first terminal device may send data a to at least one terminal device (including the second terminal device) in a multicast transmission mode. For any terminal device of the at least one terminal device, if the data a is successfully received, the HARQ is not fed back. And if the data a is unsuccessfully received, feeding back NACK. And the first terminal equipment receives the NACK sent by any terminal equipment, and then considers that the transmission of the current data a fails.

Case 5: in an ACK-NACK feedback mode of the multicast transmission mode, the first terminal device receives at least one NACK feedback and/or at least one Discontinuous Transmission (DTX) for the ith transmission of the Sidelink HARQ process a, where the DTX means that the first terminal device does not receive the HARQ feedback sent by any terminal device in the group.

Specifically, in an ACK-NACK feedback manner of a multicast communication manner, the first terminal device may send the data a to at least one terminal device (including the second terminal device) in a multicast transmission manner. And if the data a is successfully received by any one of the at least one terminal device, feeding back an ACK to the first terminal device, otherwise, feeding back a NACK to the first terminal device. Therefore, if the first terminal device receives NACK sent by any terminal device, it considers that transmission of the current data a fails. Or, after receiving the data a, any one of the at least one terminal device may feed back ACK or NACK to the first terminal device. Therefore, if the first terminal device does not receive the HARQ feedback of any terminal device in the group, it may be considered that the transmission of the current data a is failed.

(2) The first terminal device may determine that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is ACK, that is, may determine that the reception of the ith transmission of the Sidelink HARQ process a is successful:

case 1: in the unicast communication mode, the HARQ feedback received by the first terminal device and sent by the second terminal device is ACK. When the HARQ feedback is ACK, the second terminal device may be indicated to successfully receive the ith transmission of the Sidelink HARQ process a.

Case 2: in a NACK-only feedback mode in the multicast communication mode, the first terminal device does not receive NACK feedback for the ith transmission of the Sidelink HARQ process a.

Case 3: in an ACK-NACK feedback mode in the multicast communication mode, the first terminal device receives HARQ feedback for the ith transmission of the Sidelink HARQ process a, where the HARQ feedback is ACK feedback, that is, all the terminal devices at the receiving end in the multicast group feed back ACKs.

In addition, in one possible implementation. Under the condition of a unicast communication mode, or NACK-only feedback of a multicast communication mode or ACK-NACK feedback of the multicast communication mode, if the HARQ attribute of the data a associated with the Sidelink HARQ process a is disable (disable), the first terminal equipment disables the HARQ feedback bit in SCI, that is, the first terminal equipment instructs the second terminal equipment not to perform HARQ feedback on ith transmission of the Sidelink HARQ process a. The first terminal device cannot receive HARQ feedback from the second terminal device for the ith transmission of the Sidelink HARQ process a. In this case, the first terminal device may determine the HARQ feedback of the ith transmission of the Sidelink HARQ process a as NACK, or determine the HARQ feedback of the ith transmission of the Sidelink HARQ process a as ACK, which is not limited. Specifically, it is determined that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is NACK or ACK, depending on the internal implementation of the first terminal device.

The embodiment of the present application further provides a communication method, which may correspond to the third scheme, where in the scheme, a timer is not introduced, and the first terminal device may directly monitor a PDCCH of the network device according to a time domain position of a pscch resource that sends sillink data.

(IV) example IV

Fig. 6 shows a specific flow of the communication method according to the fourth embodiment.

S601, an RRC connection is established between the first terminal device and the network device. After the RRX connection is established, the first terminal device may enter an RRC connected state.

S602, a Sidelink is established between the first terminal device and the second terminal device. After the Sidelink is established, the first terminal device may transmit data to the second terminal device through the Sidelink.

S603, the network device configures DRX cycle for the first terminal device in RRC connection state.

The DRX cycle consists of "On Duration" and "Opportunity for DRX": in the "On Duration", the first terminal device monitors and receives the PDCCH (active state); within "Opportunity for DRX", the first terminal device does not monitor the PDCCH to save power consumption (sleep state).

S604, the first terminal device may monitor and receive the PDCCH1 sent by the network device. PDCCH1 may indicate the resource scheduled by the network device for the ith transmission of a certain Sidelink HARQ process (e.g., Sidelink HARQ process a), i.e., PDCCH1 may be used to schedule the ith transmission of the Sidelink HARQ process a.

Optionally, the Sidelink HARQ process a may associate data a. The Sidelink HARQ process a may be used for the first terminal device to transmit data a to the second terminal device on the Sidelink established in S602. The Sidelink HARQ process a may maintain one state variable: CURRENT _ SL _ TX _ NB. For example, CURRENT _ SL _ TX _ NB may indicate the number of transmission of data a, and CURRENT _ SL _ TX _ NB may be initialized to 0.

S605, after receiving PDCCH1, the first terminal device may transmit data a to the second terminal device through Sidelink HARQ process a on the psch resource indicated by PDCCH1, that is, perform the ith transmission of data a. Accordingly, the second terminal device may receive data a transmitted by the first terminal device on the psch resource indicated by PDCCH 1.

S606, the first terminal device starts to monitor the PDCCH according to the time domain position of the psch resource for the ith transmission of the data a.

The psch resources include time domain resources and frequency domain resources. The time domain resource of the psch for the ith transmission of data a may occupy one or more time units. The first terminal device monitors a third time domain location of the PDCCH, which may be the first time unit after the last time unit in the time domain resource of the psch on which the ith transmission of data a is made. Alternatively, the third time domain position of the monitored PDCCH may be a time unit that is offset from the last time domain unit in the time domain resource of the i-th transmitted psch by a third time domain. The third time domain offset may include one or more time cells.

In a possible implementation manner, the first terminal device may determine the third time domain position according to the time domain resource position of the psch resource for the ith transmission of the data a and the third time domain offset. And starting to monitor the PDCCH at a third time domain position. The third time domain offset may be protocol-specified, or configured by the network device, or implemented internally in the first terminal device, without limitation. For example, a possible implementation manner is that the network device may carry the configuration information of the third time domain offset through SL-psch-Config signaling. In the embodiment of the present application, the configuration mode, the configuration signaling, and the naming of the third time domain offset are not limited. The third time domain offset may be one time domain offset from the time domain resource end position of the psch resource on which the ith transmission of data a is made. When the third time domain offset is 0, the first terminal device may monitor the PDCCH in the first time unit after the first transmission of the data a is sent on the pscch resource.

In another possible implementation manner, without defining the concept of the third time domain offset, the first terminal device uses the first time unit after the time domain resource end position of the psch resource for the ith transmission of the data a as the third time domain position, and starts to monitor the PDCCH at the third time domain position.

In addition to the above situation, the first terminal device may monitor the PDCCH when the following conditions are satisfied: the first terminal equipment determines that a state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a indicates the transmission times of the Sidelink HARQ process a; whether the maximum number of transmissions or the preset number of transmissions is exceeded.

When the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a is smaller than the maximum transmission time or a preset transmission time, the first terminal device monitors the PDCCH at a third time domain position according to the ith transmission HARQ feedback of the Sidelink HARQ process a; otherwise, at the third time domain position, the PDCCH is not monitored any more. It should be noted that, when the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a is equal to the maximum transmission time or the preset transmission time, the first terminal device may monitor the PDCCH, or the first terminal device may not monitor the PDCCH, which is not limited. The maximum transmission times and the preset transmission times may be specified by a protocol, or configured by a network device, or implemented inside the first terminal device, without limitation.

S607, the first terminal device receives PDCCH 2.

In one possible implementation, the resource indicated by PDCCH2 may be a resource scheduled by the network device for the i +1 th transmission of the Sidelink HARQ process a, that is, PDCCH2 may be used to schedule the i +1 th transmission of the Sidelink HARQ process a. The (i + 1) th transmission is a retransmission relative to the (i) th transmission relative to a previous transmission of the (i + 1) th transmission.

In another possible implementation, the resource indicated by PDCCH2 may be a resource scheduled by the network device for initial transmission of the Sidelink HARQ process a. At this time, the Sidelink HARQ process a associates new data, such as data b. I.e. the Sidelink HARQ process a has been used for the first terminal device to transmit new data instead of data a. In this case, in subsequent S608, the first terminal device may also stop the second timer.

S608, upon monitoring and receiving the PDCCH2, the first terminal device may stop monitoring the PDCCH. Thereafter, the first terminal device may perform i +1 th transmission of the Sidelink HARQ process a to the second terminal device according to the scheduling of the PDCCH 2.

Or, the first terminal device may stop monitoring the PDCCH at a preset time. The preset time may be specified by a protocol, or configured by a network device, or implemented in the first terminal device, without limitation.

It should be noted that the above scheme may be applied to point-to-point unicast transmission, may also be applied to point-to-multipoint multicast transmission, may be applied to the case of configuring the PSFCH resource, may also be applied to the case of not configuring the PSFCH resource, and is not limited.

In the fourth scheme of the embodiment, the first terminal device does not introduce any timer, and directly monitors the PDCCH of the network device according to the time domain position of the psch resource. The method can also reduce the transmission time delay of the Sidelink data and meet the QoS requirement of the Sidelink service.

In the fourth embodiment of the present application, data transmission of the Sidelink is scheduled once by using one PDCCH as an example. Of course, one PDCCH may also schedule multiple transmissions of one sildelink data. At this time, one PDCCH may indicate a plurality of pscch resources. In S606, the time domain position of the psch resource of the first terminal device, determining a third time domain position, and starting to monitor the PDCCH may specifically be: the first terminal device may determine the third time domain position according to the time domain position of the psch resource transmitting the first repetition (repetition), start monitoring the PDCCH, and specifically refer to the description in S606, which is not described again. Of course, the above is only an exemplary illustration, and the third time domain position may be determined according to the time domain position of the last repeated pscch resource, and the PDCCH starts to be monitored, or even the time domain position of any repeated pscch resource, and the third time domain position is determined, and the PDCCH starts to be monitored, and the like, without limitation. The first repetition refers to a first transmission of a plurality of transmissions of one sildelink data scheduled by the PDCCH. The embodiment of the present application further provides a communication method, which may correspond to the fourth scheme, where in the scheme, a timer is not introduced, and the first terminal device may directly monitor the PDCCH according to the time domain position of the PSFCH resource when receiving the HARQ feedback on the PSFCH resource.

(V) example V

An embodiment is provided for the case of configuring PSFCH resources.

As shown in fig. 7, a detailed flow of the communication method provided in the fifth embodiment is described.

S701, RRC connection is established between the first terminal device and the network device.

S702, a Sidelink is established between the first terminal device and the second terminal device.

After the Sidelink is established, the first terminal device may transmit data to the second terminal device through the Sidelink.

S703, the network device configures a DRX cycle for the first terminal device in the RRC connected state.

Illustratively, a DRX cycle consists of "On Duration" and "Opportunity for DRX": in the "On Duration", the first terminal device monitors and receives the PDCCH (active state); within "opportunity DRX", the first terminal device does not monitor the PDCCH (dormant state).

Optionally, the first terminal device may further send a resource scheduling request to the network device, so as to request the network device to schedule transmission resources for the Sidelink data transmission. Typically, the resource scheduling request may carry a buffer status report to indicate how much Sidelink data the first terminal device has on the Sidelink to transmit. Accordingly, after receiving the resource scheduling request, the network device may transmit a scheduling resource for the Sidelink, and issue the scheduled resource in the PDCCH. The first terminal device may learn the resources scheduled by the network device by monitoring the PDCCH.

S704, the first terminal device may monitor and receive the PDCCH1 sent by the network device. PDCCH1 may indicate the resource scheduled by the network device for the ith transmission of a certain Sidelink HARQ process (e.g., Sidelink HARQ process a), i.e., PDCCH1 may be used to schedule the ith transmission of the Sidelink HARQ process a.

Optionally, the Sidelink HARQ process a may associate data a. The Sidelink HARQ process a may be used for the first terminal device to transmit data a to the second terminal device on the Sidelink established in S702. The Sidelink HARQ process a may maintain one state variable: CURRENT _ SL _ TX _ NB. For example, CURRENT _ SL _ TX _ NB may indicate the number of transmission of data a, and CURRENT _ SL _ TX _ NB may be initialized to 0.

S705, after receiving PDCCH1, the first terminal device may transmit data a to the second terminal device through Sidelink HARQ process a on the psch resource indicated by PDCCH1, that is, perform the ith transmission of data a. Accordingly, the second terminal device may receive data a transmitted by the first terminal device on the psch resource indicated by PDCCH 1.

Specifically, the second terminal device may know, by monitoring the PSCCH, which PSCCH resources the first terminal device may transmit data a on. Thus, after receiving PDCCH1, the first terminal device may send the SCI on the PSCCH. The second terminal device may receive the SCI by listening to the PSCCH. The SCI is used to instruct the first terminal device on the resources to transmit data a.

S706, the first terminal device receives HARQ feedback of ith transmission of the Sidelink HARQ process a on a PSFCH resource, where the PSFCH resource may be used to carry HARQ feedback of ith transmission of the Sidelink HARQ process a sent to the first terminal device by the second terminal device.

S707, the first terminal device determines the ith transmission HARQ feedback of the Sidelink HARQ process a. The ith transmission HARQ feedback of the Sidelink HARQ process a is used to indicate whether the reception of the ith transmission of the data a is successful or not. For the process of the first terminal device determining whether the HARQ feedback of the ith transmission of the Sidelink HARQ process a is successful, refer to the above description, and will not be described here.

S708, the first terminal device monitors or does not monitor the PDCCH according to the ith transmission HARQ feedback of the Sidelink HARQ process a and the time domain position of the PSFCH resource receiving the ith transmission HARQ feedback of the Sidelink HARQ process a. When the first terminal device monitors and receives PDCCH2, PDCCH2 may be used to schedule the i +1 th transmission of Sidelink HARQ process a. The first device may transmit data a to the second terminal device through a Sidelink HARQ process a on the psch resource indicated by PDCCH2, i.e. an i +1 th transmission of data a is made.

In a possible implementation manner, if the first terminal device determines that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is NACK, that is, determines that the reception of the ith transmission of the Sidelink HARQ process a is unsuccessful, the first terminal device may determine the fourth time domain position according to the time domain position of the PSFCH resource receiving the HARQ feedback of the ith transmission of the Sidelink HARQ process a; and the first terminal equipment monitors the PDCCH at the fourth time domain position. Thereafter, when the first terminal device monitors and receives PDCCH2, the first terminal device stops monitoring PDCCH. Alternatively, the first terminal device may stop monitoring the PDCCH at a preset time. The preset time may be specified by a protocol, or configured by a network device, or implemented inside the first terminal device, and the like, without limitation.

Optionally, the first terminal device may determine the fourth time domain position according to the time domain resource position of the PSFCH resource receiving the HARQ feedback of the ith transmission of the Sidelink HARQ process a and the fourth time domain offset. And monitoring the PDCCH at a fourth time domain position. The fourth time domain offset may be predefined by a protocol, or configured by a network device, or implemented internally by the first terminal device, etc., without limitation. For example, in a possible implementation manner, the network device carries the configuration of the fourth time domain offset through the SL-PSFCH-Config signaling, and a specific configuration manner and configuration signaling of the fourth time domain offset and a name of the fourth time domain offset are not limited. The fourth time domain position may be one time domain offset from the time domain resource end position of the PSFCH resource receiving the HARQ feedback for the ith transmission of the Sidelink HARQ process a. When the fourth time domain offset is 0, the first terminal device monitors the PDCCH on the first time unit after receiving the HARQ feedback of the ith transmission of the data a on the PSFCH resource. Alternatively, it may be described that the first terminal device monitors the PDCCH in the first time unit after receiving the PSFCH resource end position of the HARQ feedback of the ith transmission of the Sidelink HARQ process a.

In another possible implementation manner, without defining the concept of the fourth time domain offset, the first terminal device uses the first time unit after the time domain resource end position of the PSFCH resource receiving the HARQ feedback of the ith transmission of the Sidelink HARQ process a as the fourth time domain position, and monitors the PDCCH at the fourth time domain position.

In another possible implementation manner, if the first terminal device determines that the HARQ feedback of the ith transmission of the Sidelink HARQ process a is ACK, that is, determines that the reception of the ith transmission of the Sidelink HARQ process a is successful, the first terminal device does not monitor the PDCCH at the fourth time domain position.

When the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a is smaller than the maximum transmission time or the preset transmission time, the first terminal device may monitor or not monitor the PDCCH at the fourth time domain position according to the HARQ feedback of the ith transmission of the Sidelink HARQ process a; for example, if the HARQ feedback of the ith transmission of the Sidelink HARQ process a is ACK, that is, it is determined that the ith transmission of the Sidelink HARQ process a is successfully received, the first terminal device may not monitor the PDCCH. And if the HARQ feedback of the ith transmission of the Sidelink HARQ process a is NACK, that is, the ith transmission of the Sidelink HARQ process a fails, the first terminal equipment monitors the PDCCH. And when the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a is greater than the maximum transmission time or the preset transmission time, the first terminal device does not monitor the PDCCH any more at the fourth time domain position.

It should be noted that, when the state variable CURRENT _ SL _ TX _ NB associated with the Sidelink HARQ process a is equal to the maximum transmission time or the preset transmission time, the first terminal device may monitor the PDCCH, or the first terminal device may not monitor the PDCCH, which is not limited. The maximum transmission times and the preset transmission times may be specified by a protocol, or configured by a network device, or implemented inside the first terminal device, without limitation.

In the communication method, a timer is not introduced any more, and the first terminal device can directly monitor the PDCCH of the network device according to the time domain position of the PSFCH resource. The method can also reduce the transmission time delay of the Sidelink data and meet the QoS requirement of the Sidelink service.

It should be noted that the first to fifth embodiments are not limited, and may be applied to a case where PUCCH resources are mapped or a case where PUCCH resources are not mapped. The configured PUCCH resource may also be referred to as a PUCCH resource associated with the psch resource (psch resource for i-th transmission of data a), and the non-configured PUCCH resource may also be referred to as a PUCCH resource not associated with the psch resource (psch resource for i-th transmission of data a). For example, the PUCCH resource may be a resource for the first terminal device to send HARQ feedback of the ith transmission of the data a to the network device.

Alternatively, the first to fifth embodiments may be applied to the sildenk transmission in the dynamic DCI scheduling, that is, the ith transmission of the data a is the sildenk transmission in the PDCCH dynamic scheduling, or may be applied to the preconfigured sildenk grant (configured sildenk grant), that is, the ith transmission of the data a is the sildenk transmission on the preconfigured sildenk grant. Optionally, in the preconfigured sildenk grant, the preconfigured sildenk grant may not have an associated PUCCH resource, and the pusch resource may be, for example, a resource for the first terminal device to send HARQ feedback of the ith transmission of the data a to the network device.

The preconfigured sildelink grant may refer to a resource required for the network device to transmit the sildelink preconfigured for the terminal in the NR sildelink. For example, the resource required for transmitting the preconfigured sildenk may be referred to as a sildenk CG configuration, or a preconfigured sildenk grant configuration. The terminal can perform the sildelink transmission on the sildelink CG configuration without dynamic scheduling of the network device. The sildelink CG configuration includes, but is not limited to, two pre-configured authorized resources employed by the fifth Generation mobile communication technology (5th-Generation, 5G). The two pre-configured authorized resources adopted by 5G are obtained through two authorization manners, respectively, where the two authorization manners include a configured authorization manner 1(configured grant type1) and a configured authorization manner 2(configured grant type 2).

For example, the configuration authorization manner 1 is that the network device pre-configures resources (CG configuration) required for uplink transmission for the terminal in a semi-static configuration manner, that is, active CG configuration is configured periodically, and it is not necessary for the terminal to obtain uplink authorization configured by the CG to the network device before sending uplink data each time. For example, the network device may configure a CG configuration for uplink transmission for the terminal through RRC signaling, and the RRC signaling may further include a cycle of the CG configuration. For the sildelink CG configuration, the network device pre-configures resources (sildelink CG configuration) required for the sildelink transmission for the terminal in a semi-static configuration mode, that is, the activated sildelink CG configuration is configured periodically, and it is not required that the terminal acquires the sildelink authorization configured for the sildelink CG configuration from the network device before sending the sildelink data each time. For example, the network device may configure, for the terminal, a Sidelink CG configuration for Sidelink transmission through RRC signaling, where the RRC signaling may further include a period of the Sidelink CG configuration.

The configuration authorization manner 2 refers to that the network device may configure, through RRC signaling, part of information for the terminal to use for uplink transmission, for example, a cycle of CG configuration for uplink transmission, and the like. Then, the network device activates the CG configuration through a physical layer signaling carrying the CG configuration for uplink transmission, so that the terminal can perform uplink transmission in the CG configuration. Wherein the physical layer signaling comprises DCI. For the Sidelink configuration, it means that the network device may configure, through RRC signaling, part of information for the Sidelink transmission for the terminal, for example, a period of the Sidelink _ CG configuration for the Sidelink transmission, and the like. Then, the network device activates the Sidelink CG configuration through a physical layer signaling carrying the CG configuration for the Sidelink transmission, so that the terminal can perform the Sidelink transmission in the Sidelink CG configuration. Wherein the physical layer signaling comprises DCI.

It should be noted that the names of the two authorization manners are not limited to the configuration authorization manner 1 and the configuration authorization manner 2, and other names may also be used. The communication system to which the two authorization manners are applicable may be an LTE communication system or another communication system, besides the 5G communication system, and the embodiment of the present application does not limit the communication system to which the two authorization manners are applicable.

The method provided in the present application is described in detail above with reference to fig. 1 to 7. The device provided by the embodiment of the application is described in detail below with reference to fig. 8 and 9. It is to be understood that the description of the apparatus embodiments corresponds to the description of the method embodiments. Therefore, reference may be made to the description in the above method examples for what is not described in detail.

Fig. 8 is a schematic block diagram of an apparatus 800 provided in an embodiment of the present application, configured to implement the functions of the first terminal device in the foregoing method embodiments. The apparatus may be a software unit or a system of chips. The chip system may be constituted by a chip, but may also comprise a chip or other discrete devices. The apparatus may include a communication unit 801 for communicating with the outside. The apparatus may also include a processing unit 802 for performing the processing.

In one example, the apparatus 800 is configured to implement the steps of the first terminal device in the first and second embodiments of the method. The apparatus 800 may be a terminal device, or may be a chip or a circuit configured in the terminal device. The communication unit 801 is configured to perform transceiving related operations on the first terminal device side in the first embodiment or the second embodiment, and the processing unit 802 is configured to perform processing related operations on the first terminal device side in the first embodiment or the second embodiment.

For example, the communication unit 801 is configured to receive first downlink control information DCI from a network device, where the first DCI is used to schedule initial transmission or retransmission of Sidelink data, and two timers, namely a first timer and a second timer, are associated with a Sidelink hybrid automatic repeat request HARQ process associated with the Sidelink data; a processing unit 802, configured to send, according to the scheduling of the first DCI, Sidelink data to a second terminal device using a pscch resource of a physical side uplink shared channel; a processing unit 802, further configured to start a first timer according to the time domain position of the psch resource, and start or not start a second timer according to the first timer; and under the condition of starting a second timer, monitoring a Physical Downlink Control Channel (PDCCH) by the first terminal equipment during the running period of the second timer.

Optionally, the processing unit 802 starts a first timer according to the time domain position of the pscch resource, where the first timer includes: determining a first time domain position according to the time domain resource position of the PSSCH resource and the first time domain offset; or, taking a first time unit after the time domain resource end position of the PSSCH resource as the first time domain position; starting the first timer at the first time domain position.

Optionally, the processing unit 802 starts a first timer at the first time domain position, including: determining the transmission times of the Sidelink data associated with the Sidelink HARQ process; and when the transmission times of the Sidelink data associated with the Sidelink HARQ process are less than or equal to the maximum transmission times or preset transmission times, starting the first timer at the first time domain position.

Optionally, the processing unit 802 is further configured to, when the number of transmission times of the Sidelink data associated with the Sidelink HARQ process is greater than a maximum number of transmission times or a preset number of transmission times, no longer start the first timer at the first time domain position.

Optionally, the processing unit 802 starts or does not start a second timer according to the first timer, and includes: and when the first timer is overtime, directly starting the second timer.

Optionally, the processing unit 802 starts or does not start a second timer according to the first timer, where the method includes determining that HARQ feedback of the Sidelink HARQ process is negative acknowledgement NACK before the first timer expires, and starting the second timer when the first timer expires; or before the first timer is overtime, determining that the HARQ feedback of the Sidelink HARQ process is positive ACK, directly stopping the first timer, and at this time, if the first timer is not overtime, not starting the second timer, or not stopping the first timer, but when the first timer is overtime, not starting the second timer.

Optionally, the processing unit 802 starts or does not start a second timer according to the first timer, and includes: before the first timer expires, HARQ feedback for the Sidelink HARQ process cannot be determined; and starting the second timer when the first timer is overtime.

Optionally, the processing unit 802 is further configured to: when determining that the HARQ feedback of the Sidelink HARQ process is NACK during the running period of the second timer, not stopping the second timer, and continuously monitoring the PDCCH during the running period of the second timer; or, in the running period of the second timer, when it is determined that the HARQ feedback of the Sidelink HARQ process is ACK, directly stopping the second timer, and not monitoring the PDCCH any more.

Optionally, in the case that the second timer is started, the processing unit 802 is further configured to: and during the running period of the second timer, if the PDCCH for scheduling the Sidelink data retransmission is monitored and received, stopping the second timer.

In another example, the apparatus 800 is configured to implement the steps of the first terminal device in the third method embodiment above. The apparatus 800 may be a terminal device, or may be a chip or a circuit configured in the terminal device. The communication unit 801 is configured to perform the transceiving related operations on the first terminal device side in the third embodiment, and the processing unit 802 is configured to perform the processing related operations on the first terminal device side in the third embodiment.

For example, the communication unit 801 is configured to receive first downlink control information DCI from a network device, where the first DCI is used to schedule initial transmission or retransmission of Sidelink data, and two timers, namely a first timer and a second timer, are associated with a Sidelink hybrid automatic repeat request HARQ process associated with the Sidelink data; the first terminal equipment transmits Sidelink data to second terminal equipment by utilizing physical side uplink shared channel PSSCH resources according to the scheduling of the first DCI; a communication unit 801, further configured to receive, by using a physical Sidelink feedback channel PSFCH resource, HARQ feedback from the second terminal device to the Sidelink HARQ process, where the HARQ feedback is an acknowledgement ACK or a negative acknowledgement NACK; a processing unit 802, configured to start or not start a first timer according to the HARQ feedback and the time domain position of the PSFCH resource;

under the condition that the first timer is started, when the first timer is over time, the first terminal equipment starts a second timer, and during the running period of the second timer, the first terminal equipment monitors a Physical Downlink Control Channel (PDCCH).

Optionally, the processing unit 802 starts or does not start the first timer according to the HARQ feedback and the time domain position of the PSFCH resource, including: determining a second time domain position according to the time domain resource position of the first PSFCH resource and the second time domain offset; or, taking a first time unit after the ending position of the time domain resource of the first PSFCH resource as the second time domain position; and starting or not starting the first timer at the second time domain position according to the HARQ feedback.

Optionally, the processing unit 802 starts or does not start the first timer at the second time domain position according to the HARQ feedback, including: when determining that the HARQ feedback of the Sidelink HARQ process is ACK, not starting the first timer at the second time domain position; or, when it is determined that the HARQ feedback of the Sidelink HARQ process is NACK, starting the first timer at the second time domain position.

Optionally, the processing unit 802 starts the first timer at the second time domain position, including determining the number of transmission times of the Sidelink data associated with the Sidelink HARQ process; and if the transmission times of the Sidelink data associated with the Sidelink HARQ process are less than or equal to the maximum transmission times or preset transmission times, starting the first timer at the second time domain position.

Optionally, the processing unit 802 is further configured to: and when the transmission times of the Sidelink data associated with the Sidelink HARQ process are greater than the maximum transmission times or preset transmission times, the first timer is not started any more at the second time domain position.

Optionally, in a case that the first terminal device starts the second timer, the processing unit 802 is further configured to:

and during the running period of the second timer, if a PDCCH for scheduling the first terminal equipment Sildelink data retransmission is monitored, stopping the second timer.

The division of the unit in the embodiment of the present application is schematic, and is only a logic function division, and there may be another division manner in actual implementation, and in addition, each functional unit in each embodiment of the present application may be integrated in one processor, may also exist alone physically, or may also be integrated in one unit by two or more units. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

It is to be understood that the functions of the communication unit in the above embodiments may be implemented by a transceiver, and the functions of the processing unit may be implemented by a processor. The transceiver may comprise a transmitter and/or a receiver or the like for performing the functions of the transmitting unit and/or the receiving unit, respectively. This is illustrated below with reference to fig. 9.

The communication device 900 shown in fig. 9 includes at least one processor 901. The communications apparatus 900 can also include at least one memory 902 for storing program instructions and/or data. The memory 902 is coupled to the processor 901. The coupling in the embodiments of the present application is an indirect coupling or a communication connection between devices, units or modules, and may be an electrical, mechanical or other form for information interaction between the devices, units or modules. The processor 901 may cooperate with the memory 902, the processor 901 may execute program instructions stored in the memory 902, and at least one of the at least one memory 902 may be included in the processor 901.

The apparatus 900 may also include a communication interface 903 for communicating with other devices over a transmission medium, such that the apparatus 900 may communicate with other devices. In embodiments of the present application, the communication interface may be a transceiver, circuit, bus, module, or other type of communication interface. In the embodiment of the present application, when the communication interface is a transceiver, the transceiver may include an independent receiver and an independent transmitter; a transceiver that integrates transceiving functions, or an interface circuit may be used.

It should be understood that the connection medium between the processor 901, the memory 902 and the communication interface 903 is not limited in the embodiment of the present application. In the embodiment of the present application, the memory 902, the processor 901, and the communication interface 903 are connected by the communication bus 904 in fig. 9, the bus is represented by a thick line in fig. 9, and the connection manner between other components is only illustrative and not limiting. The bus may include an address bus, a data bus, a control bus, and the like. For ease of illustration, fig. 9 is shown with only one thick line, but does not show only one bus or one type of bus or the like.

In an example, the apparatus 900 is configured to implement the steps performed by the first terminal device in the first embodiment or the second embodiment of the foregoing method. The communication interface 903 is configured to perform the transceiving related operations on the first terminal device side in the foregoing embodiments, and the processor 901 is configured to perform the processing related operations on the first terminal device side in the foregoing first or second embodiment of the method.

For example, the communication interface 903 is configured to receive first downlink control information DCI from a network device, where the first DCI is used to schedule initial transmission or retransmission of Sidelink data, and two timers are associated with a Sidelink hybrid automatic repeat request HARQ process associated with the Sidelink data, where the two timers are a first timer and a second timer, respectively; a processor 901, configured to send, according to the scheduling of the first DCI, Sidelink data to a second terminal device using a physical Sidelink shared channel PSSCH resource; the processor 901 is further configured to start a first timer according to the time domain position of the psch resource, and start or not start a second timer according to the first timer; and under the condition of starting a second timer, monitoring a Physical Downlink Control Channel (PDCCH) by the first terminal equipment during the running period of the second timer.

Optionally, the processor 901 starts a first timer according to the time domain position of the psch resource, including:

determining a first time domain position according to the time domain resource position of the PSSCH resource and the first time domain offset; or, taking a first time unit after the time domain resource end position of the PSSCH resource as the first time domain position; starting the first timer at the first time domain position.

Optionally, the processor 901 starts a first timer at the first time domain position, including: determining the transmission times of the Sidelink data associated with the SidelinkHARQ process; and when the transmission times of the Sidelink data associated with the Sidelink HARQ process are less than or equal to the maximum transmission times or preset transmission times, starting the first timer at the first time domain position.

Optionally, the processor 901 is further configured to not start the first timer at the first time domain position when the number of transmission times of the Sidelink data associated with the Sidelink HARQ process is greater than the maximum number of transmission times or a preset number of transmission times.

Optionally, the starting or not starting, by the processor 901, the second timer according to the first timer includes: and when the first timer is overtime, directly starting the second timer.

Optionally, the processor 901 starts or does not start a second timer according to the first timer, where the starting includes, before the first timer is overtime, when determining that the HARQ feedback of the Sidelink HARQ process is negative acknowledgement NACK, starting the second timer when the first timer is overtime; or, when determining that the HARQ feedback of the Sidelink HARQ process is ACK, directly stopping the first timer, and at this time, when the first timer is not overtime, not starting the second timer, or not stopping the first timer, but when the first timer is overtime, not starting the second timer.

Optionally, the starting or not starting, by the processor 901, the second timer according to the first timer includes: before the first timer expires, HARQ feedback for the Sidelink HARQ process cannot be determined; and starting the second timer when the first timer is overtime.

Optionally, the processor 901 is further configured to: during the running period of the second timer, determining that the HARQ feedback of the Sidelink HARQ process is NACK, not stopping the second timer, and during the running period of the second timer, continuing monitoring the PDCCH; or, in the running period of the second timer, when it is determined that the HARQ feedback of the Sidelink HARQ process is ACK, directly stopping the second timer, and not monitoring the PDCCH any more.

Optionally, in the case that the second timer is started, the processor 901 is further configured to: and during the running period of the second timer, if the PDCCH for scheduling the Sidelink data retransmission is monitored and received, stopping the second timer.

In an example, the apparatus 900 is configured to implement the steps performed by the first terminal device in the third embodiment of the foregoing method. The communication interface 903 is configured to perform the transceiving related operations on the first terminal device side in the foregoing embodiments, and the processor 901 is configured to perform the processing related operations on the first terminal device side in the third method embodiment.

For example, the communication interface 903 is configured to receive first downlink control information DCI from a network device, where the first DCI is used to schedule initial transmission or retransmission of Sidelink data, and two timers, namely a first timer and a second timer, are maintained in association with a Sidelink hybrid automatic repeat request HARQ associated with the Sidelink data; the first terminal equipment transmits Sidelink data to second terminal equipment by utilizing physical side uplink shared channel PSSCH resources according to the scheduling of the first DCI; the communication interface 903 is further configured to receive, by using a physical Sidelink feedback channel PSFCH resource, HARQ feedback from the second terminal device to the Sidelink HARQ process, where the HARQ feedback is an ACK or NACK; a processor 901, configured to start or not start a first timer according to the HARQ feedback and the time domain position of the PSFCH resource;

Optionally, the processor 901 starts or does not start the first timer according to the HARQ feedback and the time domain position of the PSFCH resource, including: determining a second time domain position according to the time domain resource position of the first PSFCH resource and the second time domain offset; or, taking a first time unit after the ending position of the time domain resource of the first PSFCH resource as the second time domain position; and starting or not starting the first timer at the second time domain position according to the HARQ feedback.

Optionally, the processor 901 starts or does not start the first timer at the second time domain position according to the HARQ feedback, including: determining that the HARQ feedback of the Sidelink HARQ process is ACK, and not starting the first timer at the second time domain position; or, if the HARQ feedback of the Sidelink HARQ process is determined to be NACK, starting the first timer at the second time domain position.

Optionally, the processor 901 starts the first timer at the second time domain position, including determining the number of transmission times of the Sidelink data associated with the Sidelink HARQ process; and if the transmission times of the Sidelink data associated with the Sidelink HARQ process are less than or equal to the maximum transmission times or preset transmission times, starting the first timer at the second time domain position.

Optionally, the processor 901 is further configured to: and when the transmission times of the Sidelink data associated with the Sidelink HARQ process are greater than the maximum transmission times or preset transmission times, the first timer is not started any more at the second time domain position.

Optionally, in a case that the first terminal device starts the second timer, the processor 901 is further configured to:

Further, an apparatus for performing the method in the above method embodiments is also provided in the embodiments of the present application. A computer readable storage medium comprising a program which when executed by a processor performs the method of the above method embodiments. A computer program product comprising computer program code which, when run on a computer, causes the computer to implement the method in the above method embodiments. A chip, comprising: a processor coupled with a memory for storing a program or instructions which, when executed by the processor, cause an apparatus to perform the method in the above method embodiments.

In the embodiments of the present application, the processor may be a general processor, a digital signal processor, an application specific integrated circuit, a field programmable gate array or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component, and may implement or execute the methods, steps, and logic blocks disclosed in the embodiments of the present application. A general purpose processor may be a microprocessor or any conventional processor or the like. The steps of a method disclosed in connection with the embodiments of the present application may be directly implemented by a hardware processor, or may be implemented by a combination of hardware and software modules in a processor.

In the embodiment of the present application, the memory may be a nonvolatile memory, such as a Hard Disk Drive (HDD) or a solid-state drive (SSD), and may also be a volatile memory, for example, a random-access memory (RAM). The memory is any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer, but is not limited to such. The memory in the embodiments of the present application may also be circuitry or any other device capable of performing a storage function for storing program instructions and/or data.

The method provided by the embodiment of the present application may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the invention to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a computer network, a network appliance, a user device, or other programmable apparatus. The computer instructions may be stored on a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wire (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)), or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that incorporates one or more of the available media. The usable medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a magnetic tape), an optical medium (e.g., a Digital Video Disk (DVD)), or a semiconductor medium (e.g., an SSD), among others.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims

1. A method of communication, comprising:

a first terminal device receives first Downlink Control Information (DCI) from a network device, wherein the first DCI is used for scheduling initial transmission or retransmission of Sidelink Sidelink data, and Sidelink hybrid automatic repeat request (HARQ) processes associated with the Sidelink data are associated with two timers, namely a first timer and a second timer respectively;

the first terminal equipment transmits Sidelink data to second terminal equipment by utilizing physical side uplink shared channel PSSCH resources according to the scheduling of the first DCI;

the first terminal equipment starts a first timer according to the time domain position of the PSSCH resource;

the first terminal equipment starts or does not start a second timer according to the first timer;

and under the condition of starting a second timer, monitoring a Physical Downlink Control Channel (PDCCH) by the first terminal equipment during the running period of the second timer.

2. The method of claim 1, wherein the first terminal device starting a first timer based on the time domain location of the psch resource comprises:

the first terminal equipment determines a first time domain position according to the time domain resource position of the PSSCH resource and the first time domain offset; or, the first terminal device uses a first time unit after the time domain resource end position of the psch resource as the first time domain position;

and the first terminal equipment starts the first timer at the first time domain position.

3. The method of claim 1 or 2, wherein the first terminal device starting a first timer at the first time domain location comprises:

the first terminal equipment determines the transmission times of the Sidelink data associated with the Sidelink HARQ process;

and when the transmission times of the Sidelink data associated with the Sidelink HARQ process are less than or equal to the maximum transmission times or preset transmission times, the first terminal equipment starts the first timer at the first time domain position.

4. The method of claim 3, further comprising:

and when the transmission times of the Sidelink data associated with the Sidelink HARQ process are greater than the maximum transmission times or preset transmission times, the first terminal equipment does not start the first timer at the first time domain position.

5. The method of any of claims 1 to 4, wherein the first terminal device starting or not starting a second timer based on the first timer comprises:

and when the first timer is over time, the first terminal equipment starts the second timer.

6. The method of any of claims 1 to 4, wherein the first terminal device starting or not starting a second timer based on the first timer comprises:

prior to the expiration of the first timer,

when the first terminal equipment determines that the HARQ feedback of the Sidelink HARQ process is Negative Acknowledgement (NACK), the first terminal equipment starts the second timer when the first timer is overtime; alternatively, the first and second electrodes may be,

before the first timer expires, the first terminal device stops the first timer if determining that the HARQ feedback of the Sidelink HARQ process is ACK, and does not start the second timer if the first timer expires, or the first terminal device does not stop the first timer but does not start the second timer if the first timer expires.

7. The method of any of claims 1 or 4, wherein the first terminal device starting or not starting a second timer based on the first timer comprises:

before the first timer expires, the first terminal device being unable to determine HARQ feedback for the Sidelink HARQ process;

and the first terminal equipment starts the second timer when the first timer is overtime.

8. The method of claim 7, wherein the method further comprises:

in the running period of the second timer, if the first terminal device determines that the HARQ feedback of the Sidelink HARQ process is NACK, the first terminal device does not stop the second timer, and continues to monitor the PDCCH in the running period of the second timer; alternatively, the first and second electrodes may be,

and in the running period of the second timer, the first terminal equipment stops the second timer and stops monitoring the PDCCH when the first terminal equipment determines that the HARQ feedback of the Sidelink HARQ process is ACK.

9. The method of any of claims 1 to 8, wherein in the case that the first terminal device starts the second timer, the method further comprises:

during the running period of the second timer, if the first terminal device monitors and receives the PDCCH for scheduling the sildenk data retransmission, the first terminal device stops the second timer.

10. A method of communication, comprising:

the first terminal equipment receives HARQ feedback of the Sidelink HARQ process from the second terminal equipment by utilizing a physical side-row feedback channel PSFCH resource, wherein the HARQ feedback is positive acknowledgement ACK or negative acknowledgement NACK;

the first terminal equipment starts or does not start a first timer according to the HARQ feedback and the time domain position of the PSFCH resource;

11. The method of claim 10, wherein the first terminal device starting or not starting a first timer according to the HARQ feedback and the time domain location of the PSFCH resource comprises:

the first terminal equipment determines a second time domain position according to the time domain resource position of the first PSFCH resource and the second time domain offset; or, the first terminal device uses a first time unit after the end position of the time domain resource of the first PSFCH resource as the second time domain position;

and the first terminal equipment starts or does not start the first timer at the second time domain position according to the HARQ feedback.

12. The method of claim 11, wherein the first terminal device turning on or off the first timer at the second time domain location based on the HARQ feedback comprises:

when the first terminal device determines that the HARQ feedback of the Sidelink HARQ process is ACK, the first terminal device does not start the first timer at the second time domain position; alternatively, the first and second electrodes may be,

and the first terminal equipment starts the first timer at the second time domain position when determining that the HARQ feedback of the Sidelink HARQ process is NACK.

13. The method of claim 12, wherein the first terminal device starting the first timer at the second time domain location comprises:

and if the transmission times of the Sidelink data associated with the Sidelink HARQ process are less than or equal to the maximum transmission times or preset transmission times, the first terminal equipment starts the first timer at the second time domain position.

14. The method of claim 13, further comprising:

and if the transmission times of the Sidelink data associated with the Sidelink HARQ process are greater than the maximum transmission times or preset transmission times, the first terminal equipment does not start the first timer at the second time domain position.

15. The method according to any of claims 10 to 14, wherein in case the first terminal device starts the second timer, the method further comprises:

during the running period of the second timer, if the first terminal device monitors a PDCCH for scheduling the first terminal device Sidelink data retransmission, the first terminal device stops the second timer.

16. A communications apparatus, comprising:

a communication unit, configured to receive first downlink control information DCI from a network device, where the first DCI is used to schedule initial transmission or retransmission of Sidelink data, and two timers, namely a first timer and a second timer, are associated with a Sidelink hybrid automatic repeat request HARQ process associated with the Sidelink data;

a processing unit, configured to send Sidelink data to a second terminal device by using a physical Sidelink shared channel PSSCH resource according to the scheduling of the first DCI;

the processing unit is further configured to start a first timer according to the time domain position of the psch resource, and start or not start a second timer according to the first timer;

17. The apparatus of claim 16, wherein the processing unit starts a first timer based on the time domain position of the pscch resource, comprising:

determining a first time domain position according to the time domain resource position of the PSSCH resource and the first time domain offset; or, taking a first time unit after the time domain resource end position of the PSSCH resource as the first time domain position;

starting the first timer at the first time domain position.

18. The apparatus as claimed in claim 16 or 17, wherein said processing unit starts a first timer at said first time domain location, comprising:

determining the transmission times of the Sidelink data associated with the Sidelink HARQ process;

and when the transmission times of the Sidelink data associated with the Sidelink HARQ process are less than or equal to the maximum transmission times or preset transmission times, starting the first timer at the first time domain position.

19. The apparatus of claim 18,

the processing unit is further configured to not start the first timer at the first time domain position when the number of transmission times of the Sidelink data associated with the Sidelink HARQ process is greater than a maximum number of transmission times or a preset number of transmission times.

20. The apparatus of any one of claims 16 to 19, wherein the processing unit, in response to the first timer, either starts or does not start a second timer, comprising:

and when the first timer is overtime, starting the second timer.

21. The apparatus of any one of claims 16 to 19, wherein the processing unit, in response to the first timer, either starts or does not start a second timer, comprising:

before the first timer is overtime, the first terminal equipment starts the second timer when the first timer is overtime under the condition that the HARQ feedback of the Sidelink HARQ process is determined to be Negative Acknowledgement (NACK); alternatively, the first and second electrodes may be,

before the first timer is overtime, the first terminal device stops the first timer when determining that the HARQ feedback of the Sidelink HARQ process is ACK, and does not start the second timer when the first timer is overtime, or does not stop the first timer but does not start the second timer when the first timer is overtime.

22. The apparatus of any of claims 16 or 20, wherein the processing unit, in response to the first timer, either starts or does not start a second timer, comprising:

before the first timer expires, HARQ feedback for the Sidelink HARQ process cannot be determined;

and starting the second timer when the first timer is overtime.

23. The apparatus as recited in claim 22, said processing unit to further:

during the running period of the second timer, the first terminal device determines that the HARQ feedback of the Sidelink HARQ process is NACK, does not stop the second timer, and continues to monitor the PDCCH during the running period of the second timer; alternatively, the first and second electrodes may be,

and during the running period of the second timer, the first terminal equipment stops the second timer and stops monitoring the PDCCH if the first terminal equipment determines that the HARQ feedback of the Sidelink HARQ process is ACK.

24. The apparatus of any of claims 16 to 23, wherein, in the event the second timer is started, the processing unit is further to:

and during the running period of the second timer, if the PDCCH for scheduling the Sidelink data retransmission is monitored and received, stopping the second timer.

25. A communications apparatus, comprising:

a communication unit, configured to receive first downlink control information DCI from a network device, where the first DCI is used to schedule initial transmission or retransmission of Sidelink data, and two timers, namely a first timer and a second timer, are associated with a Sidelink hybrid automatic repeat request HARQ process associated with the Sidelink data; the first terminal equipment transmits Sidelink data to second terminal equipment by utilizing physical side uplink shared channel PSSCH resources according to the scheduling of the first DCI;

the communication unit is further configured to receive, by using a physical Sidelink feedback channel PSFCH resource, HARQ feedback from the second terminal device to the Sidelink HARQ process, where the HARQ feedback is an ACK or NACK;

a processing unit, configured to start or not start a first timer according to the HARQ feedback and the time domain position of the PSFCH resource;

26. The apparatus of claim 25, wherein the processing unit to turn on or not turn on a first timer based on the HARQ feedback and the time domain location of the PSFCH resource comprises:

determining a second time domain position according to the time domain resource position of the first PSFCH resource and the second time domain offset; or, taking a first time unit after the ending position of the time domain resource of the first PSFCH resource as the second time domain position;

and starting or not starting the first timer at the second time domain position according to the HARQ feedback.

27. The apparatus of claim 26, wherein the processing unit turns on or off the first timer at the second time domain location based on the HARQ feedback, comprising:

when determining that the HARQ feedback of the Sidelink HARQ process is ACK, not starting the first timer at the second time domain position; alternatively, the first and second electrodes may be,

and starting the first timer at the second time domain position when the HARQ feedback of the Sidelink HARQ process is determined to be NACK.

28. The apparatus of claim 27, wherein the processing unit to start the first timer at the second time domain location comprises:

and if the transmission times of the Sidelink data associated with the Sidelink HARQ process are less than or equal to the maximum transmission times or preset transmission times, starting the first timer at the second time domain position.

29. The apparatus as recited in claim 28, said processing unit to further:

and when the transmission times of the Sidelink data associated with the Sidelink HARQ process are greater than the maximum transmission times or preset transmission times, not starting the first timer at the second time domain position.

30. The apparatus according to any one of claims 25 to 29, wherein in case the first terminal device starts the second timer, the processing unit is further configured to:

31. A communications apparatus comprising a processor coupled with at least one memory, the processor to read a computer program stored by the at least one memory to perform the method of any of claims 1 to 9 or to perform the method of any of claims 10 to 15.

32. A computer-readable storage medium, characterized by comprising a program which, when executed by a processor, performs the method of any of claims 1 to 9, or performs the method of any of claims 10 to 15.