Patent Description:
Currently, a feedback mechanism of a sidelink (sidelink, SL) is introduced in device to device (device to device, D2D) communication based on a <NUM>th generation (<NUM>th generation, <NUM>) mobile communication technology, for example, vehicle to everything (vehicle to everything, V2X) communication based on a new radio (new radio, NR) technology. For example, a sending terminal device adjusts, based on feedback information, for example, response information of a hybrid automatic repeat request (hybrid automatic repeat request, HARQ) and channel state information (channel state information, CSI) of the side link, of a receiving terminal device in a circular area with the sending terminal device as a center, a communication policy between the sending terminal device and the receiving terminal device, for example, a resource scheduling policy or a data sending policy.

When a quantity of receiving terminal devices in the circular area with the sending terminal device as the center is relatively large, a large amount of feedback information needs to be transmitted. In addition, to ensure reliability of transmitting the feedback information, different resources of feedback information usually further need to be configured for different receiving terminal devices. However, feedback information of a receiving terminal device whose channel condition is good and/or that is relatively close to the sending terminal device, and feedback information of a receiving terminal device whose channel condition is poor and/or that is relatively far from the sending terminal device have no reference value. In addition, for a plurality of receiving terminal devices whose channel conditions are similar, content of feedback information is similar. Only a part of feedback information is needed to adjust a communication policy. In other words, in this case, most of the feedback information may be considered as redundant information. The feedback information that has no reference value and the redundant feedback information usually occupy a large quantity of resources of feedback information. Consequently, resources that can be used to transmit data become fewer. This adversely affects inter-device communication between the sending terminal device and the receiving terminal device. The document <CIT>shows a communication method for signaling between two terminals. Especially, a feedback scheme based upon the distance of the two terminals is shown. The document <CIT> also shows a communication method employed by two terminals. Also here, a distance-based feedback scheme is shown. The document <CIT> refers to a mobile communication system comprising: a roadside apparatus having a communication area of a movement passage of mobiles; and mobile communication devices included in the mobiles and wirelessly communicating with the roadside apparatus. The roadside apparatus simultaneously transmits information to the plural mobile communication devices; detects the presence/absence of a signal according to the wireless communication, uses a time slot for a retransmission request which is previously allocated for the retransmission request according to the information transmitted simultaneously; determines reception of the retransmission request when the signal according to the wireless communication is detected, uses the time slot for the retransmission request; and in the case of the reception of the retransmission request, retransmits the information. The plural mobile communication devices receive the information from the roadside apparatus; detect an error of the received information; and transmit the retransmission request using the time slot for the retransmission request.

dependent claims show further advantageous developments.

The following describes in detail a communication method, and a distance determining method and apparatus provided in embodiments of this application with reference to accompanying drawings.

Technical solutions in the embodiments of this application may be applied to various communication systems such as a D2D communication system, a V2X communication system, a machine type communication (machine type communication, MTC) system, a machine-to-machine (machine-to-machine, M2M) communication system, or an Internet of Vehicles communication system.

All aspects, embodiments, or features are presented in this application by describing a system that may include a plurality of devices, components, modules, and the like. It should be appreciated and understood that each system may include another device, component, module, and the like, and/or may not include all devices, components, modules, and the like discussed with reference to the accompanying drawings. In addition, a combination of these solutions may be used.

In addition, in the embodiments of this application, the terms such as "for example" and "such as" are used to represent giving an example, an illustration, or description. Any embodiment or design scheme described as an "example" in this application should not be explained as being more preferred or having more advantages than another embodiment or design scheme. Exactly, the term "example" is used to present a concept in a specific manner.

In the embodiments of this application, the terms "information (information)", "signal (signal)", "message (message)", "channel (channel)", and "signaling (signaling)" may sometimes be interchangeably used. It should be noted that meanings expressed by the terms are consistent when differences between the terms are not emphasized. "Of (of)", "relevant (relevant)", and "corresponding (corresponding)" may be interchangeably used sometimes. It should be noted that meanings expressed by the terms are consistent when differences between the terms are not emphasized.

In the embodiments of this application, sometimes a subscript, for example, W<NUM>, may be written in an incorrect form, for example, W1. Expressed meanings are consistent when differences are not emphasized.

A network architecture and a service scenario described in the embodiments of this application are intended to describe the technical solutions of the embodiments of this application more clearly, and do not constitute a limitation on the technical solutions provided in the embodiments of this application. A person of ordinary skill in the art may know that with evolution of the network architecture and emergence of a new service scenario, the technical solutions provided in the embodiments of this application are also applicable to a similar technical problem.

Some scenarios in the embodiments of this application are described by using a scenario in a communication system shown in <FIG> as an example. It should be noted that the solutions in the embodiments of this application may also be applied to another mobile communication system, and a corresponding name may also be replaced with a name of a corresponding function in the another mobile communication system.

For ease of understanding the embodiments of this application, the communication system shown in <FIG> is used as an example to describe in detail a communication system applicable to the embodiments of this application.

As shown in <FIG>, the communication system includes a plurality of terminal devices, or optionally, one or more network devices.

The terminal device may be a vehicle-mounted terminal device, for example, a first terminal device and a second terminal device, may be a road side unit (road side unit, RSU) having a function of the terminal device, or may be a terminal device used by a passenger or a pedestrian, for example, a mobile phone or a pad. The network device may be a base station, for example, an evolved NodeB (evolved NodeB, eNB) in a long term evolution (long term evolution, LTE) system, and a g NodeB (g NodeB, gNB) in a new radio (new radio, NR) system. The network device may alternatively be an RSU having a base station function. A type of the terminal device and a type of the network device are not limited in this embodiment of this application.

All the foregoing devices may communicate with each other. During communication, a spectrum of a cellular link may be used, or an intelligent transportation spectrum near <NUM> gigahertz (gigahertz, GHz) may be used. Mutual communication between the foregoing devices may be performed based on an LTE technology or an NR technology, or may be performed based on a device-to-device (device-to-device, D2D) communication technology, for example, a V2X technology. For example, the terminal devices may directly communicate with each other on a sidelink (sidelink, SL), or may indirectly communicate with each other by using the network device. For another example, the terminal devices may further communicate with the network device on an uplink/downlink (uplink&downlink, UL&DL).

It should be noted that the foregoing network device is optional. For example, if there is a base station, the scenario is a scenario in which network coverage is available. If there is no base station, the scenario is a scenario in which the network coverage is unavailable. When the network coverage is available, direct communication between the plurality of terminal devices on the sidelink may be performed based on a resource dynamically configured by the network device by using downlink signaling. When the network coverage is unavailable, direct communication between the plurality of terminal devices on the sidelink may be performed based on a preconfigured resource pool.

In this embodiment of this application, the network device is a device that is located on a network side of the communication system and has a wireless transceiver function, or a chip or a chip system that may be disposed in the device. The network device includes but is not limited to an evolved NodeB (evolved NodeB, eNB), a radio network controller (radio network controller, RNC), a NodeB (NodeB, NB), a base station controller (base station controller, BSC), a base transceiver station (base transceiver station, BTS), a home base station (for example, a home evolved NodeB, or a home NodeB, HNB), a baseband unit (baseband unit, BBU), an access point (access point, AP) in a wireless fidelity (wireless fidelity, Wi-Fi) system, a wireless relay node, a wireless backhaul node, a transmission point (transmission and reception point, TRP, or transmission point, TP), or the like. Alternatively, the network device may be a gNB or a transmission point (TRP or TP) in a <NUM> system, for example, a new radio (new radio, NR) system; may be one antenna panel or a group of antenna panels (including a plurality of antenna panels) of a base station in a <NUM> system; or may be a network node that constitutes a gNB or a transmission point, for example, a baseband unit (BBU) or a distributed unit (distributed unit, DU).

The terminal device is a terminal device that accesses the communication system and has the wireless transceiver function, or a chip or a chip system that may be disposed in the terminal device. The terminal device may also be referred to as a vehicle-mounted terminal device, a user apparatus, an access terminal device, a user unit, a user station, a mobile station, a remote station, a remote terminal device, a mobile device, a user terminal device, a terminal device, a wireless communication device, a user agent, or a user apparatus. The terminal device in this embodiment of application may be a mobile phone (mobile phone), a tablet computer (Pad), a computer with the wireless transceiver function, a virtual reality (virtual reality, VR) terminal device, an augmented reality (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 a smart grid (smart grid), a wireless terminal device in transportation safety (transportation safety), a wireless terminal device in a smart city (smart city), a wireless terminal device in a smart home (smart home), or the like.

It should be understood that <FIG> is merely a simplified schematic diagram of an example for ease of understanding. The communication system may further include another network device and/or another terminal device that are/is not shown in <FIG>.

The communication method provided in the embodiments of this application may be applied to a communication apparatus shown in <FIG>. The communication apparatus may be a terminal device, or may be a chip, a chip system, or another component that has a function of a terminal device applied to the terminal device. As shown in <FIG>, the communication apparatus <NUM> may include at least one processor <NUM>, a memory <NUM>, and a transceiver <NUM>.

The following specifically describes each component of the communication apparatus with reference to <FIG>.

The processor <NUM> is a control center of the communication apparatus, and may be one processor or may be a collective term of a plurality of processing elements. For example, the processor <NUM> may be a central processing unit (central processing unit, CPU), or an application-specific integrated circuit (application-specific integrated circuit, ASIC), or one or more integrated circuits configured to implement this embodiment of this application, for example, one or more microprocessors (for example, digital signal processor, DSP) or one or more field-programmable gate arrays (field-programmable gate array, FPGA).

The processor <NUM> may run or execute a software program stored in the memory <NUM> and invoke data stored in the memory <NUM>, to execute various functions of the communication apparatus.

During specific implementation, in an embodiment, the processor <NUM> may include one or more CPUs, for example, a CPU <NUM> and a CPU <NUM> shown in <FIG>.

During specific implementation, in an embodiment, the communication apparatus may include a plurality of processors, for example, the processor <NUM> and a processor <NUM> shown in <FIG>. Each of the processors may be a single-core processor (single-CPU) or may be a multi-core processor (multi-CPU). The processor herein may be one or more communication devices, circuits, and/or processing cores configured to process data (for example, computer program instructions).

The memory <NUM> may be a read-only memory (read-only memory, ROM) or another type of static storage communication device that can store static information and instructions; or a random access memory (random access memory, RAM) or another type of dynamic storage communication device that can store information and instructions. The memory <NUM> may alternatively be an electrically erasable programmable read-only memory (electrically erasable programmable read-only memory, EEPROM), a compact disc read-only memory (compact disc read-only memory, CD-ROM) or another compact disc storage, optical disc storage (including a compact disc, a laser disc, an optical disc, a digital versatile disc, a Blu-ray disc, or the like), a magnetic disk storage medium or another magnetic storage communication device, or any other medium that can be used to carry or store expected program code in a form of instructions or a data structure and that is accessible by a computer, but is not limited thereto. The memory <NUM> may exist independently, or may be integrated with the processor <NUM>.

The memory <NUM> is configured to store a software program for performing solutions of this application, and the processor <NUM> controls execution of the software program.

The transceiver <NUM> is configured to communicate with another communication apparatus. Certainly, the transceiver <NUM> may be further configured to communicate with a communication network, for example, the Ethernet, a radio access network (radio access network, RAN), or a wireless local area network (wireless local area network, WLAN). The transceiver <NUM> may include a receiving unit for implementing a receiving function and a sending unit for implementing a sending function.

In this embodiment of this application, the memory <NUM> may store the software program or instructions. After the communication apparatus <NUM> is powered on, the processor <NUM> may read and execute the software program or the instructions stored in the memory <NUM>, so that the communication apparatus <NUM> may perform the following communication method shown in <FIG>. For a specific implementation, refer to the following method embodiments.

The structure of the communication apparatus shown in <FIG> should not be considered as a limitation on the communication apparatus, in other words, the communication apparatus may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

The communication apparatus <NUM> may also be sometimes referred to as a terminal device apparatus, a terminal device, or a communication device, and may be a general-purpose device or a special-purpose device. For example, the communication apparatus <NUM> may be a vehicle-mounted terminal device, an RSU, a palmtop computer (for example, personal digital assistant, PDA), a mobile phone, a tablet computer, a wireless terminal device, an embedded device, or a device having a structure similar to that shown in <FIG>. A type of the communication apparatus <NUM> is not limited in this embodiment of this application.

The following describes in detail the communication method provided in the embodiments of this application with reference to <FIG>.

<FIG> is a schematic flowchart of a communication method according to an embodiment of this application. The communication method may be applied to any terminal device in <FIG>, for example, the first terminal device in <FIG> or the communication apparatus <NUM> shown in <FIG>, to complete direct communication with another terminal device, for example, the second terminal device in <FIG>, on a sidelink. As shown in <FIG>, the communication method includes the following steps.

S301: A first terminal device sends a first signal to a second terminal device. Correspondingly, the second terminal device receives the first signal from the first terminal device.

Optionally, the first signal includes one or more of data, a control signal, and a reference signal.

For example, the first terminal device may send the data to at least one and/or at least one type of second terminal device on the sidelink. The at least one second terminal device may include at least one of the following types of second terminal devices: at least one second terminal device having a point-to-point service with the first terminal device, for example, a unicast service; and at least one second terminal device having a point-to-multipoint service with the first terminal device, for example, a broadcast service, a multicast service, or a groupcast service. A type and a quantity of services of the first terminal device and a type and a quantity of second terminals that have the foregoing services with the first terminal device are not limited in this embodiment of this application.

For example, the first terminal device may send the control signal to the at least one and/or the at least one type of second terminal device on the sidelink.

For example, the first terminal device may send the reference signal to the at least one and/or the at least one type of second terminal device on the sidelink.

Optionally, the first terminal device may broadcast location information of the first terminal device. The location information of the first terminal device may be location information determined based on information provided by a global navigation satellite system (global navigation satellite system, GNSS). The location information may be absolute coordinates of a location in which the first terminal device is located, for example, longitude and latitude coordinates. The location information may alternatively be an identifier of a preset area in which the first terminal device is located and a position offset (which may also be referred to as relative coordinates) of the first terminal device relative to a reference point in the preset area. The preset area may be a zone whose length (length) and width (width) are respectively L and W, and the area identifier of the preset area corresponds to absolute coordinates of the reference point in the preset area. The area identifier may be an identifier of a physical cell accessed by the first terminal device, an identifier of a base station accessed by the first terminal device, an identifier of a service area accessed by the first terminal device, or the like. The reference point may be a geometric center, a vertex, or the like of the preset area. For example, the reference point in the zone may be a diagonal intersection point, any vertex, a midpoint of any edge, or the like of the zone.

It should be noted that there is a one-to-one correspondence between the area identifier of the preset area and the relative coordinates and the absolute coordinates of the preset area; and the absolute coordinates of the preset area may be calculated based on the area identifier of the preset area and the relative coordinates.

In a possible design method, the first terminal device enables radio resource control signaling, media access control signaling, a master information block, a system information block, or physical control information to carry longitude and/or latitude information of the first terminal device.

In a possible design method, the first terminal device enables the radio resource control signaling, the media access control signaling, the master information block, the system information block, or the physical control information to carry index of an area in which the first terminal device is located.

In a possible design method, the first terminal device enables the radio resource control signaling, the media access control signaling, the master information block, the system information block, or the physical control information to carry a longitude offset and/or a latitude offset of the first terminal device in a preset area.

Optionally, when network coverage is available, the first terminal device may also report the location information of the first terminal device to a network device, for example, a base station, and the network device broadcasts the location information of the first terminal device.

Correspondingly, the second terminal device may separately receive, on the sidelink or a downlink, the location information of the first terminal device from the first terminal device or the network device.

In a possible design method, the second terminal device receives the longitude and/or the latitude information of the first terminal device that are/is carried by the radio resource control signaling, the media access control signaling, the master information block, the system information block, or the physical control information and that is sent by the first terminal device or the network device.

In a possible design method, the second terminal device receives the index of the area in which the first terminal device is located that is carried by the radio resource control signaling, the media access control signaling, the master information block, the system information block, or the physical control information and that is sent by the first terminal device or the network device.

In a possible design method, the second terminal device receives the longitude offset and/or the latitude offset of the first terminal device that are/is carried by the radio resource control signaling, the media access control signaling, the master information block, the system information block, or the physical control information and that is sent by the first terminal device or the network device.

It should be noted that in an application scenario in which a location update speed of a terminal device is relatively fast, for example, a V2X communication scenario and a high-speed railway communication scenario, the first terminal device and/or the network device may need to update the location information of the first terminal device in a timely manner. For example, the location information of the first terminal device may be periodically broadcast within a relatively short update period, for example, <NUM>, <NUM>, or <NUM>. For another example, when the first terminal device learns that a distance between the first terminal device and the second terminal device may change greatly, for example, the first terminal device is moving at an accelerated speed, or a movement direction of the first terminal device changes greatly, the first terminal device may broadcast the location information of the first terminal device in real time.

S302: The second terminal device determines that the second terminal device is located in a specified area.

In a possible design method, the specified area may be determined based on the distance between the second terminal device and the first terminal device and a lower distance threshold and/or an upper distance threshold. The upper distance threshold is greater than the lower distance threshold.

Specifically, the second terminal device may calculate the distance between the second terminal device and the first terminal device based on location information of the second terminal device and the location information of the first terminal device, and determine, based on a result obtained through comparison between the distance with the upper distance threshold and/or the lower distance threshold, a specified area in which the second terminal device is located. The location information of the first terminal device may be received from the first terminal device or the network device. For content and an obtaining manner of obtaining the location information of the second terminal device, refer to the content and an obtaining manner of obtaining the location information of the first terminal device.

Optionally, it is assumed that longitude and latitude coordinates of the first terminal are (X<NUM>, Y<NUM>), and longitude and latitude coordinates of the second terminal device are (X<NUM>, Y<NUM>), therefore, the second terminal device may calculate the distance D (distance) between the second terminal device and the second terminal device according to the following formula: <MAT>.

It should be noted that if a requirement for calculation precision is relatively high, the longitude and latitude coordinates of the first terminal device (X<NUM>, Y<NUM>) may occupy relatively large signaling and resource overheads. To reduce signaling and the resource overheads, a geographic area may be divided into a plurality of zones (zone) whose length (length) and width (width) are respectively L and W. The first terminal device may broadcast an identifier of the zone (zone identifier, ZID) in which the first terminal device is located and an offset, for example, relative coordinates (x<NUM>, y<NUM>), of the first terminal in the zone. (x<NUM>, y<NUM>) is a modulus value of the longitude and latitude coordinates of the first terminal device in the zone, namely, x<NUM> = (X<NUM>)mod(L), and y<NUM> = (Y<NUM>)mod (W). Compared with (X<NUM>, Y<NUM>) , a value range of the modulus value (x<NUM>, y<NUM>) in the zone is much smaller, so that signaling overheads of the location information of the first terminal device can be reduced.

The second terminal device calculates the distance D, based on the received coordinate information (x<NUM>, y<NUM>) of the first terminal device and the identifier ZID <NUM> of the zone, and relative coordinates (x<NUM>, y<NUM>) of the second terminal device in a zone <NUM> in which the second terminal device is located and an identifier ZID <NUM> of the zone, by using the following formula: <MAT>.

G is a size of a zone, for example, may be represented by a diagonal length: <MAT>. When the zone is large, a front half of the formula can be ignored. When the identifier of the zone in which the second terminal device is located and the identifier of the zone in which the first terminal device is located are the same, namely, ZID <NUM> = ZID <NUM>, the last half of the foregoing distance calculation formula is zero.

Optionally, when an area of the zone is relatively small, absolute coordinates of a reference point in a first zone and absolute coordinates of a reference point in a second zone may also be obtained based on an area identifier of the first zone in which the first terminal device is located and an area identifier of the second zone in which the second terminal device is located. Then, calculating the distance between the second terminal device and the first terminal device is simplified to calculating a distance between the two reference points. In this case, the first terminal device only needs to broadcast or report an area identifier of a zone in which the first terminal device is currently located when the zone in which the first terminal device is located changes, so that signaling overheads and resource overheads can be greatly reduced. In this case, the zone may also be replaced with a regular hexagon area, and a reference point may be a geometric center of the regular hexagon area.

It is easy to understand that if the second terminal device and the first terminal device are in a same zone, the distance may be obtained through calculation directly based on relative coordinates (x<NUM>, y<NUM>) of the first terminal device in the zone and relative coordinates (x<NUM>, y<NUM>) of the second terminal device in the zone, namely, <MAT>.

It is easy to understand that the second terminal device may also send the location information of the second terminal device, so that another terminal device, for example, the first terminal device, determines a distance between the another terminal device and the second terminal device based on the location information of the second terminal device.

<FIG> is a schematic diagram of a communication scenario according to an embodiment of this application. As shown in <FIG>, the scenario includes three specified areas: an inner circle area, an annular area, and an outer circle area. The three specified areas are divided based on a lower distance threshold and an upper distance threshold. The lower distance threshold is used to determine a radius of an inner circle, the radius of the inner circle is used to determine a circumference of the inner circle, and the circumference of the inner circle is used to divide the inner circle area and the annular area. The upper distance threshold is used to determine a radius of an outer circle, the radius of the outer circle is used to determine a circumference of the outer circle, and the circumference of the outer circle is used to divide the annular area and the outer circle area.

For example, when the distance between the second terminal device and the first terminal device is less than or equal to the lower distance threshold, the second terminal device may determine that the second terminal device, for example, a second terminal device A in <FIG>, is located in the inner circle area. For another example, when the distance between the second terminal device and the first terminal device is greater than or equal to the upper distance threshold, the second terminal device may determine that the second terminal device, for example, a second terminal device B in <FIG>, is located in the outer circle area. For still another example, when the distance between the second terminal device and the first terminal device is greater than or equal to the lower distance threshold and less than or equal to the upper distance threshold, the second terminal device may determine that the second terminal device, for example, a second terminal device C in <FIG>, is located in the annular area.

In another possible design method, the specified area may alternatively be determined based on strength of a signal received by the second terminal device from the first terminal device, a lower signal strength threshold and/or an upper signal strength threshold. The upper signal strength threshold is greater than the lower signal strength threshold. The strength of the signal may be reference signal received power (reference signal received power, RSRP), a received signal strength indicator (received signal strength indicator, RSSI), or reference signal received quality (reference signal received quality, RSRQ) received by the second terminal device; or may be another technical indicator used to indicate the strength of the received signal. This is not limited in this embodiment of this application.

Specifically, the second terminal device may determine, based on a result obtained through comparison between the strength of the signal received by the second terminal device from the first terminal device with the lower signal strength threshold and/or the upper signal strength threshold, a specified area in which the second terminal device is located.

The three areas in the communication scenario shown in <FIG> may alternatively be divided based on the lower signal strength threshold and/or the upper signal strength threshold. As shown in <FIG>, the upper signal strength threshold is used to determine the radius of the inner circle, the radius of the inner circle is used to determine the circumference of the inner circle, and the circumference of the inner circle is used to divide the inner circle area and the annular area. The lower signal strength threshold is used to determine the radius of the outer circle, the radius of the outer circle is used to determine the circumference of the outer circle, and the circumference of the outer circle is used to divide the annular area and the outer circle area.

For example, when the strength of the signal received by the second terminal device from the first terminal device is greater than or equal to the upper signal strength threshold, the second terminal device may determine that the second terminal device, for example, the second terminal device A in <FIG>, is located in the inner circle area. For another example, when the strength of the signal received by the second terminal device from the first terminal device is less than or equal to the lower signal strength threshold, the second terminal device may determine that the second terminal device, for example, the second terminal device B in <FIG>, is located in the outer circle area. For still another example, when the strength of the signal received by the second terminal device from the first terminal device is greater than or equal to the lower signal strength threshold and less than or equal to the upper signal strength threshold, the second terminal device may determine that the second terminal device, for example, the second terminal device C in <FIG>, is located in the annular area.

It should be noted that the specified areas in the communication scenario shown in <FIG> are described by using concentric circle areas as an example. Actually, the specified area can also be defined by using an area of another geometry. The another geometry may be an elliptical area, a sector area, a rectangular area, or the like. For example, in a highway scenario shown in <FIG>, elliptical areas in which the first terminal device is a center and major axes are consistent with a front-to-back extension direction of a highway is used (for example, implemented by using front-to-back beamforming). Three specified areas, namely, an inner elliptical area, an annular elliptical area and an outer elliptical area based on a circumference of an inner ellipse and a circumference of an outer ellipse. A person skilled in the art should further understand that, given that channel conditions and propagation manners of wireless signals in various directions may be different, for example, whether there is an obstacle on a channel, different signals have different attenuation speeds, different signals have different propagation manners such as direct radiation, diffraction, scattering, transmission, multipath, and the like, and whether a beamforming technology is used, demarcation lines of the specified areas determined by using the upper signal strength threshold and/or the lower signal strength threshold are likely not to be circles or ellipses.

In addition, the communication scenarios shown in <FIG> and <FIG> only involve three specified areas divided by using a maximum of two thresholds (the upper distance threshold and the lower distance threshold, or the upper signal strength threshold and the lower signal strength threshold). In actual application, a quantity of thresholds and a quantity of specified areas may be greater.

In addition, the upper distance threshold and the lower distance threshold, and the upper signal strength threshold and the lower signal strength threshold may also be used in combination, for example, the lower distance threshold and the upper signal strength threshold are used together, or the upper distance threshold and the lower signal strength threshold are used together. As long as different specified areas can be distinguished, a manner in which the thresholds are used is not limited in this embodiment of this application.

In this embodiment of this application, the upper distance threshold and the lower distance threshold, and the upper signal strength threshold and the lower signal strength threshold may be determined and broadcast by the first terminal device, or may be determined and reported by the first terminal device to the base station, and then be broadcast by the base station. Correspondingly, the second terminal device may receive the upper distance threshold and the lower distance threshold, and the upper signal strength threshold and the lower signal strength threshold broadcast by the first terminal device and/or the base station. Alternatively, the upper distance threshold and the lower distance threshold, and the upper signal strength threshold and the lower signal strength threshold may be determined by each terminal device according to a preset threshold determining rule. A subject for determining the upper distance threshold and the lower distance threshold, and the upper signal strength threshold and the lower signal strength threshold is not limited in this embodiment of this application.

The following describes in detail a method for determining the upper distance threshold and the lower distance threshold and a method for determining the upper signal strength threshold and the lower signal strength threshold by using the annular area in the communication scenario shown in <FIG>. The upper distance threshold may be determined based on quality of service or a priority of service, and is used to ensure specified quality of service and transmission of a high-priority service. The lower distance threshold may be determined based on a resource of feedback information or a feedback quantity, and is used to ensure that the first terminal can obtain a specific feedback amount and feedback overheads are not excessively large, so that the resource of feedback information is properly used. The lower distance threshold corresponds to the radius of the inner circle of the annular area, and the upper distance threshold corresponds to the radius of the outer circle of the annular area. The determining method may be stored in various forms such as an application program, an executable script, a configuration file, or a spreadsheet in each terminal device or the base station for backup according to a distance threshold determining rule.

In a possible design method, the following rule <NUM> may be used to determine the upper distance threshold and the lower distance threshold.

Rule <NUM>: The upper distance threshold is positively correlated with the quality of service (quality of service, QoS), the priority of service (priority of service, POS), or the quantity of resources of feedback information; and/or the lower distance threshold is negatively correlated with the quality of service QoS, the priority of service, or the quantity of resources of feedback information.

For example, the quality of service may include one or more of the following: a minimum bit error rate, a maximum delay, a minimum data rate, and the like. It is easy to understand that for a service that has a high requirement on reliability, a minimum bit error rate with a relatively small value may be set, for example, <NUM>/<NUM>. For a service that has a high requirement on a data transmission delay, for example, an online game service and an autonomous driving service, a maximum delay with a relatively small value may be set, for example, <NUM> millisecond (millisecond, ms) or <NUM>. For a service that has a high requirement on a data rate, for example, an online video playback service, a minimum data rate with a relatively large value may be set, for example, <NUM> megabits per second (megabits per second, Mbps) or <NUM> Mbps.

For example, the priority of service may be a priority defined for a proximity-based service (proximity-based services, ProSe) (ProSe per packet priority, PPPP) on the sidelink. Currently, there are eight priorities.

For example, the resource of feedback information is a radio resource that can be used to carry feedback information on the sidelink. The radio resource may include at least one of a time domain resource, a frequency domain resource, a code domain resource, a space domain resource, and a power domain resource. The frequency domain resource includes, for example, an index of a resource block RB, a quantity of RBs, an index of a subchannel, and an identifier of an RB in a subchannel. The time domain resource includes, for example, a sign location (including a commanding sign or a terminating sign), a quantity of signs, a timeslot location (including a start timeslot or an end timeslot), a quantity of timeslots, and the like. The code domain resource includes a root sequence, a mask, scrambling code, a cyclic shift, a comb tooth, and the like. The space domain resource includes a codeword, a stream, a layer, a quantity of antennas, numbers of antenna ports, a quantity of antenna ports, and the like. The power domain resource includes a power value, a power range, a power offset, and a power threshold.

In this embodiment of this application, the radio resource may be one or more groups of resources or one or more resource pools dynamically configured or preconfigured by the network device in the terminal device. This is not limited in this embodiment of this application.

For example, Table <NUM> to Table <NUM> respectively show a correspondence between the quality of service QoS (QoS x) and the upper distance threshold, a correspondence between the priority of service PPPP (PPPP x) and the upper distance threshold, or a correspondence between the quantity of resources of feedback information (resource of feedback information) (FIBR x) and the upper distance threshold. A larger value of "x" indicates higher quality of service or a higher priority of service, or a larger quantity of resources of feedback information.

Refer to Table <NUM> and Table <NUM>. Higher quality of service or a higher priority of service indicates a higher requirement on communication reliability, and indicates that more second terminal devices need to send feedback information for reference by the first terminal device. Correspondingly, a range of the annular area needs to be extended. Optionally, the range of the annular area may be extended outward. As shown in Table <NUM> and Table <NUM>, the upper distance threshold is increased from R <NUM> to R <NUM>, to extend the annular area. Conversely, lower quality of service or a lower priority of service indicates a lower requirement on communication reliability, and indicates a quantity of second terminal devices that can send feedback information may be appropriately reduced, to reduce resource consumption of feedback information. Optionally, the range of the annular area may be narrowed inward. As shown in Table <NUM> and Table <NUM>, the upper distance threshold is reduced from R <NUM> to R <NUM>, to narrow the annular area.

It can be learned from Table <NUM> that, a larger quantity of resources of feedback information may allow more second terminal devices to send feedback information for reference by the first terminal device, thereby improving communication reliability. Correspondingly, the range of the annular area may be extended. Optionally, the range of the annular area may be extended outward. As shown in Table <NUM>, the upper distance threshold is increased from R <NUM> to R <NUM>, to extend the annular area. Conversely, a smaller quantity of resources of feedback information indicates that an amount of feedback information needs to be reduced. For example, the quantity of second terminal devices that can send feedback information may be appropriately reduced, to reduce resource consumption of feedback information. Optionally, the range of the annular area may be narrowed inward. As shown in Table <NUM>, the upper distance threshold is reduced from R <NUM> to R <NUM>, to narrow the annular area.

For example, Table <NUM> to Table <NUM> respectively show a correspondence between the quality of service QoS (QoS x) and the lower distance threshold, a correspondence between the priority of service PPPP (PPPP x) and the lower distance threshold, or a correspondence between the quantity of resources of feedback information (FIBR x) and the lower distance threshold. A larger value of "x" indicates higher quality of service or a higher priority of service, or a larger quantity of resources of feedback information.

Refer to Table <NUM> and Table <NUM>. Higher quality of service or a higher priority of service indicates a higher requirement on communication reliability, and indicates that more second terminal devices need to send feedback information for reference by the first terminal device. Correspondingly, the range of the annular area needs to be extended. Optionally, the range of the annular area may be extended inward. As shown in Table <NUM> and Table <NUM>, the lower distance threshold is reduced from R <NUM> to R <NUM>, to extend the annular area. Conversely, lower quality of service or a lower priority of service indicates a lower requirement on communication reliability, and indicates the quantity of second terminal devices that can send feedback information may be appropriately reduced, to reduce resource consumption of feedback information. Optionally, the range of the annular area may be narrowed outward. As shown in Table <NUM> and Table <NUM>, the lower distance threshold is increased from R <NUM> to R <NUM>, to narrow the annular area.

It can be learned from Table <NUM> that, a larger quantity of resources of feedback information may allow more second terminal devices to send feedback information for reference by the first terminal device, thereby improving communication reliability. Correspondingly, the range of the annular area may be extended. Optionally, the range of the annular area may be extended inward. As shown in Table <NUM>, the lower distance threshold is reduced from R <NUM> to R <NUM>, to extend the annular area. Conversely, a smaller quantity of resources of feedback information indicates that the amount of feedback information needs to be reduced. For example, the quantity of second terminal devices that can send feedback information may be appropriately reduced, to reduce resource consumption of feedback information. Optionally, the range of the annular area may be narrowed outward. As shown in Table <NUM>, the lower distance threshold is increased from R <NUM> to R <NUM>, to narrow the annular area.

It should be noted that the quality of service QoS may be represented by using different technical indicators such as a bit error rate, a delay, and a data rate, and correspondences between the different technical indicators with different values and the quality of service may be different. For example, for the bit error rate and the delay, a smaller value indicates higher quality of service QoS; but for the data rate, a larger value indicates higher quality of service.

Similarly, the priority of service may also be expressed in different forms. For example, a larger value of the priority of service indicates a higher priority, or a smaller value of the priority of service indicates a higher priority. Correspondences between the service priorities expressed in different forms with different values and the quality of service may also be different.

In this embodiment of this application, the upper distance threshold and/or the lower distance threshold may alternatively be determined based on the feedback information. Details are described below. The feedback information may include an acknowledgment ACK or a negative acknowledgment NACK, and/or channel state information CSI.

The CSI includes at least one piece of the following information: a channel quality indicator (channel quality indicator, CQI), a precoding matrix indicator (precoding matrix indicator, PMI), a rank indicator (rank indicator, RI), reference signal received power (reference signal received power, RSRP), reference signal received quality (reference signal received quality, RSRQ), a pathloss (Pathloss), a sounding reference signal SRS resource indicator (sounding reference signal resource indicator, SRI), a channel state information-reference signal CSI-RS resource indicator (channel state information-reference signal resource indicator, CRI), a received signal strength indicator (received signal strength indicator, RSSI), a precoding type indicator (precoding type indicator, PTI), a direction of vehicle movement, an interference condition, and the like.

Optionally, the CSI may include a wideband CSI and/or a subband CSI of at least one piece of the foregoing information.

Optionally, the CSI may include periodic CSI, semi-persistent CSI, or aperiodic CSI of at least one piece of the foregoing information.

Optionally, the CSI may include layer <NUM> CSI and/or layer <NUM> CSI of at least one piece of the foregoing information.

In another possible design method, the following rule <NUM> may be used to determine the upper distance threshold and the lower distance threshold.

Rule <NUM>: The upper distance threshold is negatively correlated with a quantity of negative acknowledgments NACKs or an amount of channel state information CSI less than or equal to a first threshold; and/or the lower distance threshold is positively correlated with the quantity of negative acknowledgments NACKs or the amount of channel state information CSI less than or equal to the first threshold. When a first specified time period is one timeslot, the quantity of negative acknowledgments NACKs may be a quantity of timeslots in which negative acknowledgments NACKs are received by the first terminal device within the first specified time period. Alternatively, when the first specified time period is a plurality of timeslots, the quantity of negative acknowledgments NACKs may be the quantity of timeslots in which the negative acknowledgments NACKs are received by the first terminal device within the first specified time period. The plurality of timeslots may be a plurality of consecutive timeslots, or a time window (time window) including a plurality of consecutive timeslots, for example, <NUM> or <NUM>. This is not limited in this embodiment of this application.

In another possible design method, the first threshold may be preconfigured, or configured by the base station or the first terminal device by using the radio resource control signaling, the media access control signaling, the master information block, the system information block, or the physical control information.

It should be noted that the timeslot in which the negative acknowledgment NACK is received is a timeslot in which at least one negative acknowledgment NACK is received. That is, as long as a negative acknowledgment NACK is received in the timeslot, the timeslot may be considered as a timeslot in which the negative acknowledgment NACK is received. Only when all HARQ acknowledgments received in a timeslot are acknowledgments ACKs, the timeslot can be considered as a timeslot in which an acknowledgment ACK is received.

For example, Table <NUM> and Table <NUM> respectively show a correspondence between the quantity of negative acknowledgments NACKs (NACK x) and the upper distance threshold, or a correspondence between the amount of channel state information CSI (CSI x) less than or equal to the first threshold and the upper distance threshold. A larger value of "x" indicates a larger quantity.

Refer to Table <NUM> and Table <NUM>. A larger quantity of negative acknowledgments NACKs or a larger amount of channel state indicators CSI less than or equal to the first threshold may indicate a larger quantity of second terminal devices that actually send feedback information, and a larger value of the upper distance threshold. However, in actual application, the first terminal device still needs to resend data even if the first terminal device receives only one negative acknowledgment NACK. In other words, only one negative acknowledgment NACK is needed. Therefore, to reduce the amount of feedback information and reduce signaling consumption and resource consumption, the range of the annular area needs to be narrowed. Optionally, the range of the annular area may be narrowed inward. As shown in Table <NUM> and Table <NUM>, the upper distance threshold is reduced from R <NUM> to R <NUM>, to narrow the annular area.

For example, Table <NUM> and Table <NUM> respectively show a correspondence between the quantity of negative acknowledgments NACKs (NACK x) and the lower distance threshold, or a correspondence between the amount of channel state information CSI (CSI x) less than or equal to the first threshold and the lower distance threshold. A larger value of "x" indicates a larger quantity.

Refer to Table <NUM> and Table <NUM>. A larger quantity of negative acknowledgments NACKs or a larger amount of channel state information CSI less than or equal to the first threshold may indicate a larger quantity of second terminal devices that actually send feedback information, and a smaller value of the lower distance threshold. However, in actual application, the first terminal device still needs to resend data even if the first terminal device receives only one negative acknowledgment NACK. In other words, only one negative acknowledgment NACK is needed. Therefore, to reduce the amount of feedback information and reduce signaling consumption and resource consumption, the range of the annular area needs to be narrowed. Optionally, the range of the annular area may be narrowed outward. As shown in Table <NUM> and Table <NUM>, the lower distance threshold is increased from R <NUM> to R <NUM>, to narrow the annular area.

In still another possible design method, the following rule <NUM> may be used to determine the upper distance threshold and the lower distance threshold.

Rule <NUM>: The upper distance threshold is positively correlated with a quantity of acknowledgments ACKs or an amount of CSI information greater than or equal to a second threshold; and/or the lower distance threshold is positively correlated with the quantity of acknowledgments ACKs or the amount of CSI information greater than or equal to the second threshold. Optionally, the quantity of acknowledgments ACKs may be a quantity of timeslots in which all HARQ acknowledgments received by the first terminal device within a second specified time period are acknowledgments ACKs. The second specified time period may generally include a plurality of timeslots, for example, may be a plurality of consecutive timeslots or a time window including a plurality of consecutive timeslots, for example, <NUM> or <NUM>. This is not limited in this embodiment of this application. The second threshold is greater than the first threshold.

In another possible design method, the second threshold may be preconfigured, or configured by the base station or the first terminal device by using the radio resource control signaling, the media access control signaling, the master information block, the system information block, or the physical control information.

For example, Table <NUM> to Table <NUM> respectively show a correspondence between the quantity of acknowledgments ACKs (ACK x) and the upper distance threshold, or a correspondence between the amount of channel state information CSI (CSI x) greater than or equal to the second threshold and the upper distance threshold. A larger value of "x" indicates a larger quantity.

Refer to Table <NUM> to Table <NUM>. A larger quantity of acknowledgments ACKs or a larger amount of channel state indicators CSI greater than or equal to the second threshold indicates that a channel condition of the annular area is better, and corresponding data transmission quality is better, for example, no bit error occurs. In other words, a setting of the annular area may be inappropriate. For example, a distance between the annular area and the first terminal device is extremely close, and feedback information sent by the second terminal device in the annular area has no reference value. In addition, another risk may also exist. Refer to <FIG>. It is assumed that the first terminal device resends data only based on the negative acknowledgment NACK sent by the second terminal device in the annular area or the channel state information CSI less than or equal to the first threshold. In this case, the second terminal device in the outer circle area is not allowed to send feedback information. In addition, when the second terminal device in the outer circle area fails to receive data, the first terminal device does not resend data. As a result, the second terminal device in the outer circle area has no opportunity to receive data again. As a result, reliability of direct communication between the terminal devices is degraded. To resolve the foregoing problem, the annular area may be moved outward as a whole, to be specific, the lower distance threshold and the upper distance threshold are increased at the same time. As shown in Table <NUM> and Table <NUM>, the upper distance threshold is increased from R <NUM> to R <NUM>; and/or as shown in Table <NUM> and Table <NUM>, the lower distance threshold is increased from R <NUM> to R <NUM>, to improve reliability of direct communication between the terminal devices.

The following describes in detail the method for determining the upper signal strength threshold and the lower signal strength threshold by using the annular area in the communication scenario shown in <FIG>. The upper signal strength threshold may be determined based on the resource of feedback information or the feedback quantity, and is used to ensure that the first terminal can obtain a specific feedback amount, and feedback overheads are not excessively large, so that the resource of feedback information is properly used. The lower signal strength threshold may be determined based on the quality of service or the priority of service, and is used to ensure the specified quality of service and transmission of the high-priority service. The upper signal strength threshold corresponds to the radius of the inner circle of the annular area, and the lower signal strength threshold corresponds to the radius of the outer circle of the annular area. The determining method may be stored in various forms such as the application program, the executable script, the configuration file, or the spreadsheet in each terminal device or the base station for backup according to a signal strength threshold determining rule.

In a possible design method, the following rule <NUM> may be used to determine the upper signal strength threshold and the lower signal strength threshold.

Rule <NUM>: The upper signal strength threshold is positively correlated with the quality of service QoS, the priority of service POS, or the quantity of resources of feedback information; and/or the lower signal strength threshold is negatively correlated with the quality of service QoS, the priority of service, or the quantity of resources of feedback information.

For example, Table <NUM> to Table <NUM> respectively show a correspondence between the quality of service QoS (QoS x) and the upper signal strength threshold, a correspondence between the priority of service PPPP (PPPP x) and the upper signal strength threshold, or a correspondence between the quantity of resources of feedback information (FIBR x) and the upper signal strength threshold. A larger value of "x" indicates higher quality of service or a higher priority of service, or a larger quantity of resources of feedback information.

Refer to Table <NUM> and Table <NUM>. Higher quality of service or a higher priority of service indicates a higher requirement on communication reliability, and indicates that more second terminal devices need to send feedback information for reference by the first terminal device. Correspondingly, the range of the annular area needs to be extended. Optionally, the range of the annular area may be extended inward. As shown in Table <NUM> and Table <NUM>, the upper signal strength threshold is increased from RSRP <NUM> to RSRP <NUM>, to extend the annular area. Conversely, lower quality of service or a lower priority of service indicates a lower requirement on communication reliability, and indicates the quantity of second terminal devices that can send feedback information may be appropriately reduced, to reduce resource consumption of feedback information. Optionally, the range of the annular area may be narrowed outward. As shown in Table <NUM> and Table <NUM>, the upper signal strength threshold is reduced from RSRP <NUM> to RSRP <NUM>, to narrow the annular area.

It can be learned from Table <NUM> that, a larger quantity of resources of feedback information may allow more second terminal devices to send feedback information for reference by the first terminal device, thereby improving communication reliability. Correspondingly, the range of the annular area may be extended. Optionally, the range of the annular area may be extended inward. As shown in Table <NUM>, the upper signal strength threshold is increased from RSRP <NUM> to RSRP <NUM>, to extend the annular area. Conversely, a smaller quantity of resources of feedback information indicates that the amount of feedback information needs to be reduced. For example, the quantity of second terminal devices that can send feedback information may be appropriately reduced, to reduce resource consumption of feedback information. Optionally, the range of the annular area may be narrowed outward. As shown in Table <NUM>, the upper signal strength threshold is reduced from RSRP <NUM> to RSRP <NUM>, to narrow the annular area.

For example, Table <NUM> to Table <NUM> respectively show a correspondence between the quality of service QoS (QoS x) and the lower signal strength threshold, a correspondence between the priority of service PPPP (PPPP x) and the lower signal strength threshold, or a correspondence between the quantity of resources of feedback information (FIBR x) and the lower signal strength threshold. A larger value of "x" indicates higher quality of service or a higher priority of service, or a larger quantity of resources of feedback information.

Refer to Table <NUM> and Table <NUM>. Higher quality of service or a higher priority of service indicates a higher requirement on communication reliability, and indicates that more second terminal devices need to send feedback information for reference by the first terminal device. Correspondingly, the range of the annular area needs to be extended. Optionally, the range of the annular area may be extended outward. As shown in Table <NUM> and Table <NUM>, the upper signal strength threshold is reduced from RSRP <NUM> to RSRP <NUM>, to extend the annular area. Conversely, lower quality of service or a lower priority of service indicates a lower requirement on communication reliability, and indicates the quantity of second terminal devices that can send feedback information may be appropriately reduced, to reduce resource consumption of feedback information. Optionally, the range of the annular area may be narrowed inward. As shown in Table <NUM> and Table <NUM>, the lower signal strength threshold is increased from RSRP <NUM> to RSRP <NUM>, to narrow the annular area.

It can be learned from Table <NUM> that, a larger quantity of resources of feedback information may allow more second terminal devices to send feedback information for reference by the first terminal device, thereby improving communication reliability. Correspondingly, the range of the annular area may be extended. Optionally, the range of the annular area may be extended outward. As shown in Table <NUM>, the lower signal strength threshold is reduced from RSRP <NUM> to RSRP <NUM>, to extend the annular area. Conversely, a smaller quantity of resources of feedback information indicates that the amount of feedback information needs to be reduced. For example, the quantity of second terminal devices that can send feedback information may be appropriately reduced, to reduce resource consumption of feedback information. Optionally, the range of the annular area may be narrowed inward. As shown in Table <NUM>, the lower signal strength threshold is increased from RSRP <NUM> to RSRP <NUM>, to narrow the annular area.

It should be noted that the quality of service QoS may be represented by using the different technical indicators such as the bit error rate, the delay, and the data rate, and the correspondences between the different technical indicators with the different values and the quality of service may be different. For example, for the bit error rate and the delay, a smaller value indicates higher quality of service QoS; but for the data rate, a larger value indicates higher quality of service.

Similarly, the priority of service may also be expressed in the different forms. For example, a larger value of the priority of service indicates a higher priority, or a smaller value of the priority of service indicates a higher priority. The correspondences between the service priorities expressed in the different forms with the different values and the quality of service may also be different.

In this embodiment of this application, the upper signal strength threshold and/or the lower signal strength threshold may alternatively be determined based on the feedback information. Details are described below. The feedback information may include an acknowledgment ACK or a negative acknowledgment NACK, and/or channel state information CSI.

In another possible design method, the following rule <NUM> may be used to determine the upper signal strength threshold and the lower signal strength threshold.

Rule <NUM>: The upper signal strength threshold is negatively correlated with a quantity of negative acknowledgments NACKs or an amount of channel state information CSI less than or equal to a first threshold; and/or the lower signal strength threshold is positively correlated with the quantity of negative acknowledgments NACKs or the amount of channel state information CSI less than or equal to the first threshold. The quantity of negative acknowledgments NACKs may be a quantity of timeslots in which negative acknowledgments NACKs are received by the first terminal device within a first specified time period. The first specified time period may generally include a plurality of timeslots, for example, may be a plurality of consecutive timeslots or a time window (time window) including a plurality of consecutive timeslots, for example, <NUM> or <NUM>. This is not limited in this embodiment of this application.

It should be noted that the timeslot in which the negative acknowledgment NACK is received is a timeslot in which the at least one negative acknowledgment NACK is received. That is, as long as the negative acknowledgment NACK is received in the timeslot, the timeslot may be considered as a timeslot in which the negative acknowledgment NACK is received. Only when all HARQ acknowledgments received in a timeslot are acknowledgments ACKs, the timeslot can be considered as a timeslot in which an acknowledgment ACK is received.

For example, Table <NUM> and Table <NUM> respectively show a correspondence between the quantity of negative acknowledgments NACKs (NACK x) and the upper signal strength threshold, or a correspondence between the amount of channel state information CSI (CSI x) less than or equal to the first threshold and the upper signal strength threshold. A larger value of "x" indicates a larger quantity.

Refer to Table <NUM> and Table <NUM>. A larger quantity of negative acknowledgments NACKs or a larger amount of channel state indicators CSI less than or equal to the first threshold may indicate the larger quantity of second terminal devices that actually send feedback information, and a larger value of the upper signal strength threshold. However, in actual application, the first terminal device still needs to resend data even if the first terminal device receives only one negative acknowledgment NACK. In other words, only one negative acknowledgment NACK is needed. Therefore, to reduce the amount of feedback information and reduce signaling consumption and resource consumption, the range of the annular area needs to be narrowed. Optionally, the range of the annular area may be narrowed outward. As shown in Table <NUM> and Table <NUM>, the upper signal strength threshold is reduced from RSRP <NUM> to RSRP <NUM>, to narrow the annular area.

For example, Table <NUM> and Table <NUM> respectively show a correspondence between the quantity of negative acknowledgments NACKs (NACK x) and the lower signal strength threshold, or a correspondence between the amount of channel state information CSI (CSI x) less than or equal to the first threshold and the lower signal strength threshold. A larger value of "x" indicates a larger quantity.

Refer to Table <NUM> and Table <NUM>. A larger quantity of negative acknowledgments NACKs or a larger amount of channel state information CSI less than or equal to the first threshold may indicate the larger quantity of second terminal devices that actually send feedback information, and a smaller value of the lower signal strength threshold. However, in actual application, the first terminal device still needs to resend data even if the first terminal device receives only one negative acknowledgment NACK. In other words, only one negative acknowledgment NACK is needed. Therefore, to reduce the amount of feedback information and reduce signaling consumption and resource consumption, the range of the annular area needs to be narrowed. Optionally, the range of the annular area may be narrowed inward. As shown in Table <NUM> and Table <NUM>, the lower signal strength threshold is increased from RSRP <NUM> to RSRP <NUM>, to narrow the annular area.

In still another possible design method, the following rule <NUM> may be used to determine the upper signal strength threshold and the lower signal strength threshold.

Rule <NUM>: The upper signal strength threshold is positively correlated with a quantity of acknowledgments ACKs or an amount of CSI information greater than or equal to a second threshold; and/or the lower signal strength threshold is positively correlated with the quantity of acknowledgments ACKs or the amount of CSI information greater than or equal to the second threshold. Optionally, the quantity of acknowledgments ACKs may be a quantity of timeslots in which all HARQ acknowledgments received by the first terminal device within a second specified time period are acknowledgments ACKs. The second specified time period may generally include a plurality of timeslots, for example, may be a plurality of consecutive timeslots or a time window including a plurality of consecutive timeslots, for example, <NUM> or <NUM>. This is not limited in this embodiment of this application. The second threshold is greater than the first threshold.

For example, Table <NUM> to Table <NUM> respectively show a correspondence between the quantity of acknowledgments ACKs (ACK x) and the upper signal strength threshold, or a correspondence between the amount of channel state information CSI (CSI x) greater than or equal to the second threshold and the upper signal strength threshold. A larger value of "x" indicates a larger quantity.

Refer to Table <NUM> and Table <NUM>. A larger quantity of acknowledgments ACKs or a larger amount channel state indicators CSI greater than or equal to the second threshold indicates that the channel condition of the annular area is better, and the corresponding data transmission quality is better, for example, no bit error occurs. In other words, the setting of the annular area may be inappropriate. For example, the distance between the annular area and the first terminal device is extremely close, and the feedback information sent by the second terminal device in the annular area has no reference value. In addition, another risk may also exist. Refer to <FIG>. It is assumed that the first terminal device resends data only based on the negative acknowledgment NACK sent by the second terminal device in the annular area or the channel state information CSI less than or equal to the first threshold. In this case, the second terminal device in the outer circle area is not allowed to send feedback information. In addition, when the second terminal device in the outer circle area fails to receive data, the first terminal device does not resend data. As a result, the second terminal device in the outer circle area has no opportunity to receive data again. As a result, reliability of direct communication between the terminal devices is degraded. To resolve the foregoing problem, the annular area may be moved outward as a whole, to be specific, the lower distance threshold and the upper distance threshold are reduced at the same time. As shown in Table <NUM> and Table <NUM>, the upper distance threshold is reduced from RSRP <NUM> to RSRP <NUM>; and/or as shown in Table <NUM> and Table <NUM>, the lower distance threshold is reduced from RSRP <NUM> to RSRP <NUM>, to improve reliability of direct communication between the terminal devices.

S303: The second terminal device sends feedback information to the first terminal device. Correspondingly, the first terminal device receives the feedback information from the at least one second terminal device.

Optionally, if the first signal includes data, the feedback information sent by the second terminal device to the first terminal device is HARQ information. If the HARQ information fed back by the second terminal device is NACK information, the first terminal device resends data. If the HARQ information fed back by the second terminal device is not the NACK information, the first terminal device does not resend data. Optionally, if the first terminal device receives HARQ information fed back by a plurality of second terminal devices, as long as the at least one second terminal device in the annular area feeds back a NACK, the first terminal device needs to resend data.

Optionally, if the first signal includes the control signal, the feedback information sent by the second terminal device to the first terminal device is channel state information CSI. The control signal is used to trigger the aperiodic CSI. The first terminal device determines a modulation and coding scheme (modulation and coding scheme, MCS) of the data based on the CSI.

Optionally, if the first signal includes the reference signal, the feedback information sent by the second terminal device to the first terminal device is channel state information CSI. The second terminal obtains the channel state information CSI by measuring the reference signal. The first terminal device determines the MCS of the data based on the CSI.

Optionally, if the first terminal device receives CSI fed back by the plurality of second terminal devices, the first terminal device may determine the MCS of the data based on worst CSI.

In a possible design method, there may be a plurality of specified areas; and a feedback policy of any one of the plurality of specified areas may be independently determined, and/or a resource of feedback information of the any one of the plurality of specified areas may be independently determined. The feedback policy may include one or more of the following: sending a negative acknowledgment NACK and skipping sending an acknowledgment ACK indication; or sending an acknowledgment ACK or sending a negative acknowledgment NACK indication; or skipping sending an acknowledgment ACK and skipping sending a negative acknowledgment NACK indication; or sending channel state information CSI less than the first threshold and skipping sending channel state information CSI greater than or equal to the first threshold; or sending channel state information CSI; or skipping sending channel state information CSI. The feedback policy may alternatively use different feedback modes such as a periodic feedback mode, an aperiodic feedback mode, and a semi-persistent feedback mode. Alternatively, the feedback policy may use different feedback formats, for example, use a long feedback channel or a short feedback channel, or use a large-bit feedback channel or a small-bit feedback channel.

The following separately describes the feedback policy in detail by using the inner circle area, the annular area, and the outer circle area in <FIG> as an example.

For example, refer to <FIG>. Given that a distance from the inner circle area to the first terminal device is relatively short and/or a signal in the inner circle area is relatively strong, it may be considered that a success rate for the second terminal in the inner circle area to receive a signal sent by the first terminal is relatively high. Therefore, a probability of feeding back an acknowledgment (acknowledgement, ACK) and/or good channel state information (channel state information, CSI) by the second terminal in the inner circle area is relatively high. The inner circle area has little reference value for adjusting a data sending policy by the first terminal device. Correspondingly, the second terminal device in the inner circle area may be prohibited from feeding back the acknowledgment ACK and the channel state information CSI greater than or equal to the second threshold, in other words, the second terminal device in the inner circle area is only allowed to feed back the negative acknowledgment NACK and the channel state information CSI less than or equal to the first threshold. Therefore, the amount of feedback information sent by the second terminal device in the inner circle area can be effectively reduced, and resource consumption and signaling consumption for transmitting feedback information can be reduced.

For example, refer to <FIG>. Given that a distance from the outer circle area to the first terminal device is relatively long and/or a signal in the outer circle area is relatively poor, it may be considered that a success rate for the second terminal in the outer circle area to receive the signal sent by the first terminal is relatively low. Therefore, a probability of feeding back a negative acknowledgment (negative acknowledgement, NACK) and/or bad channel state information (channel state information, CSI) by the second terminal in the outer circle area is relatively high. The outer circle area has little reference value for adjusting the data sending policy by the first terminal device. Correspondingly, the second terminal device in the outer circle area may be prohibited from sending feedback information. Therefore, the amount of feedback information sent by the second terminal device in the outer circle area can be effectively reduced, and resource consumption and signaling consumption for transmitting feedback information can be reduced.

For example, refer to <FIG>. Different from the inner circle area and the outer circle area, a distance from the annular area to the first terminal device and/or strength of a signal in the annular area are/is between the distance from the inner circle area to the first terminal device and/or strength of the signal in the inner circle area and the distance from the outer circle area to the first terminal device and/or strength of the signal in the outer circle area. A success rate for the second terminal in the annular area to receive the signal sent by the first terminal is also between the success rate for the second terminal in the inner circle area to receive the signal sent by the first terminal and the success rate for the second terminal in the outer circle area to receive the signal sent by the first terminal. In addition, the annular area is more sensitive to a change of a radio channel condition, and has most reference value for adjusting the data sending policy by the first terminal device. Therefore, the second terminal device in the annular area may be allowed to send a plurality of types of feedback information, for example, the acknowledgment ACK or the negative acknowledgment NACK, and channel state information CSI with various values.

The first terminal device and/or the network device may adjust, in real time, one or more of an upper distance threshold, a lower distance threshold, an upper signal strength threshold, and a lower signal strength threshold of the specified area according to rule <NUM> to rule <NUM> in S302. Specifically, this may specifically include:.

In a possible design method, the communication method may further include the following step: The first terminal device sends one or more of the upper distance threshold, the lower distance threshold, the upper signal strength threshold, and the lower signal strength threshold of the specified area to the at least one second terminal device. Correspondingly, the second terminal device receives the one or more of the upper distance threshold, the lower distance threshold, the upper signal strength threshold, and the lower signal strength threshold of the specified area sent by the first terminal device. The first terminal device may send the one or more of the upper distance threshold, the lower distance threshold, the upper signal strength threshold, and the lower signal strength threshold by using the radio resource control signaling, the media access control signaling, the master information block, the system information block, or the physical control information.

In another possible design method, the communication method may further include the following step: The first terminal device reports the one or more of the upper distance threshold, the lower distance threshold, the upper signal strength threshold, and the lower signal strength threshold of the specified area to the network device. Then, the network device broadcasts the foregoing thresholds. Correspondingly, the second terminal device may receive the one or more of the upper distance threshold, the lower distance threshold, the upper signal strength threshold, and the lower signal strength threshold of the specified area sent by the network device.

In still another possible design method, the communication method may further include the following step: The first terminal device reports a statistical result of the feedback information received by the first terminal device from the at least one second terminal device to the network device. Then, the network device determines the one or more of the upper distance threshold, the lower distance threshold, the upper signal strength threshold, and the lower signal strength threshold of the specified area based on the statistical result of the feedback information, and broadcasts the foregoing various thresholds. Correspondingly, the first terminal device and the second terminal device may receive the one or more of the upper distance threshold, the lower distance threshold, the upper signal strength threshold, and the lower signal strength threshold of the specified area sent by the network device.

The first terminal device receives the feedback information, and the first terminal device may further adjust the data sending policy based on the feedback information, for example, adjust transmit power or a resource. Therefore, in a possible design method, the communication method may further include the following step: The first terminal device adjusts the data sending policy based on the feedback information.

Optionally, that the first terminal device adjusts the data sending policy based on the feedback information may include the following step: If the feedback information includes the negative acknowledgment NACK, the first terminal device resends data. Alternatively, if the first terminal device does not receive any feedback information within the second specified time period, the first terminal device resends data.

Optionally, that the first terminal device adjusts the data sending policy based on the feedback information may include the following step: The first terminal device adjusts a new data sending policy based on the feedback information, for example, increasing or decreasing transmit power; increasing, decreasing, or changing a data sending resource; increasing/decreasing a bit rate; or the like.

It should be noted that, in the foregoing method embodiment, an example in which the first terminal device is a sender and the at least one second terminal device is a receiver is used for description. In actual application, roles of the sender and the receiver may be dynamically changed. In addition, the first terminal device may separately directly communicate with the at least two second terminal devices such as the second terminal device A, the second terminal device B, and the second terminal device C in <FIG> and <FIG>, but roles of the first terminal device may be different for different second terminal devices. For example, for the second terminal device A and the second terminal device B, the first terminal device is a sender, but for the second terminal device C, the first terminal device is a receiver. A sending/receiving role of a terminal device in communication between different terminal devices is not limited in this embodiment of this application.

According to the communication method provided in this application, after sending the first signal, the first terminal device receives only the feedback information sent by the second terminal device in the specified area determined based on the upper distance threshold and the lower distance threshold or the upper signal strength threshold and the lower signal strength threshold, for example, an annular area, and does not receive feedback information sent by a terminal device that communicates with the first terminal device outside the specified area. This can resolve a problem that feedback information sent by a terminal device that is extremely close to the first terminal device has no reference value but occupies a large quantity of resources of feedback information. Therefore, the amount of feedback information and the quantity of resources of feedback information occupied by the feedback information are reduced, and resource utilization and communication efficiency can be improved.

The foregoing describes in detail the communication method in the embodiments of this application with reference to <FIG> and Table <NUM> to Table <NUM>. With reference to <FIG>, the following describes in detail a communication apparatus that can perform the communication method in the method embodiments of this application.

<FIG> is a schematic diagram of a structure of another communication apparatus according to an embodiment of this application. The communication apparatus is configured to perform functions performed by the first terminal device in the foregoing method embodiments. As shown in <FIG>, the communication apparatus <NUM> includes a sending module <NUM> and a receiving module <NUM>.

The sending module <NUM> is configured to send a first signal.

Optionally, the sending module <NUM> is further configured to send location information of the communication apparatus <NUM>, so that another terminal device, for example, a second terminal device, determines a distance between the another terminal device and the communication apparatus <NUM> based on the location information of the communication apparatus <NUM>. For content, a determining method, and a sending manner of the location information, refer to the foregoing method embodiments.

The receiving module <NUM> is configured to receive feedback information from at least one second terminal device in a specified area. The specified area is an area to which a distance from the first terminal device is greater than or equal to a lower distance threshold and/or less than or equal to an upper distance threshold; or the specified area is an area in which strength of a signal received from the first terminal device is greater than or equal to a lower signal strength threshold and/or less than or equal to an upper signal strength threshold.

In a possible design, the upper distance threshold is positively correlated with quality of service QoS, a priority of service, or a quantity of resources of feedback information; and/or the lower distance threshold is negatively correlated with the quality of service QoS, the priority of service, or the quantity of resources of feedback information.

Optionally, the feedback information may include a negative acknowledgment NACK and/or channel state information CSI. Correspondingly, the upper distance threshold is negatively correlated with a quantity of negative acknowledgments NACKs, an amount of channel state information CSI less than or equal to a first threshold, or a quantity of timeslots in which negative acknowledgments NACKs are received within a first specified time period; and/or the lower distance threshold is positively correlated with the quantity of negative acknowledgments NACKs, the amount of channel state information CSI less than or equal to the first threshold, or the quantity of timeslots in which the negative acknowledgments NACKs are received within the first specified time period.

Optionally, the feedback information may include an acknowledgment ACK and/or channel state information CSI. Correspondingly, the upper distance threshold is positively correlated with a quantity of acknowledgments ACKs or an amount of CSI information greater than or equal to a second threshold; and/or the lower distance threshold is positively correlated with the quantity of acknowledgments ACKs or the amount of CSI information greater than or equal to the second threshold.

In a possible design, the upper signal strength threshold is positively correlated with quality of service QoS, a priority of service, or a quantity of resources of feedback information; and/or the lower signal strength threshold is negatively correlated with the quality of service QoS, the priority of service, or the quantity of resources of feedback information.

Optionally, the feedback information may include a negative acknowledgment NACK and/or channel state information CSI. Correspondingly, the upper signal strength threshold is negatively correlated with a quantity of negative acknowledgments NACKs, an amount of channel state information CSI less than or equal to a first threshold, or a quantity of timeslots in which negative acknowledgments NACKs are received within a first specified time period; and/or the lower signal strength threshold is positively correlated with the quantity of negative acknowledgments NACKs, the amount of channel state information CSI less than or equal to the first threshold, or the quantity of timeslots in which the negative acknowledgments NACKs are received within the first specified time period.

Further, when the first specified time period is one timeslot, the quantity of negative acknowledgments NACKs may be the quantity of timeslots in which the negative acknowledgments NACKs are received by the first terminal device within the first specified time period. Alternatively, when the first specified time period is a plurality of timeslots, the quantity of negative acknowledgments NACKs may be the quantity of timeslots in which the negative acknowledgments NACKs are received by the first terminal device within the first specified time period. The plurality of timeslots may be a plurality of consecutive timeslots, or a time window (time window) including a plurality of consecutive timeslots, for example, <NUM> or <NUM>. This is not limited in this embodiment of this application.

Optionally, the feedback information may include an acknowledgment ACK and/or channel state information CSI. Correspondingly, the upper signal strength threshold is negatively correlated with a quantity of acknowledgments ACKs or an amount of CSI information greater than or equal to a second threshold; and/or the lower signal strength threshold is negatively correlated with the quantity of acknowledgments ACKs or the amount of CSI information greater than or equal to the second threshold.

In a possible design, there may be a plurality of specified areas; and a feedback policy of any one of the plurality of specified areas may be independently determined, and/or a resource of feedback information of the any one of the plurality of specified areas may be independently determined. The feedback policy may include: sending a negative acknowledgment NACK and skipping sending an acknowledgment ACK indication; or sending an acknowledgment ACK or sending a negative acknowledgment NACK indication; or skipping sending an acknowledgment ACK and skipping sending a negative acknowledgment NACK indication; or sending channel state information CSI less than the first threshold and skipping sending channel state information CSI greater than or equal to the first threshold; or sending channel state information CSI; or skipping sending channel state information CSI.

In a possible design, the sending module <NUM> is further configured to send one or more of an upper distance threshold, a lower distance threshold, an upper signal strength threshold, and a lower signal strength threshold of the specified area.

In a possible design, as shown in <FIG>, the communication apparatus <NUM> may further include a processing module <NUM>. The processing module <NUM> is configured to adjust a data sending policy based on the feedback information.

Optionally, the processing module <NUM> is further configured to: if the feedback information includes the negative acknowledgment NACK, control the sending module <NUM> to resend data. Alternatively, optionally, the processing module <NUM> is further configured to: if the receiving module <NUM> does not receive any feedback information within a second specified time period, control the sending module <NUM> to resend data.

It should be noted that the communication apparatus <NUM> may be a terminal device, or may be a chip or a chip system disposed in a terminal device. This is not limited in this application.

In a possible design, the communication apparatus <NUM> may further include a storage module (not shown in <FIG> and <FIG>). The storage module is configured to store instructions, and the processing module <NUM> is configured to execute the instructions stored in the storage module, so that the processing module <NUM> performs the communication method in the foregoing method embodiments.

<FIG> is a schematic diagram of a structure of still another communication apparatus according to an embodiment of this application. The communication apparatus is configured to perform functions performed by the second terminal device in the foregoing method embodiments. As shown in <FIG>, the communication apparatus <NUM> includes a receiving module <NUM>, a sending module <NUM>, and a processing module <NUM>.

The receiving module <NUM> is configured to receive a first signal from a first terminal device.

Optionally, the receiving module <NUM> is configured to receive location information of the first terminal device. Correspondingly, the processing module <NUM> is further configured to determine a distance between the first terminal device and the communication apparatus <NUM> based on location information of the communication apparatus <NUM> and the location information of the first terminal device. For content, a receiving manner, and a distance determining method of the location information, refer to the foregoing method embodiments.

The processing module <NUM> is configured to determine that the communication apparatus is located in a specified area. The specified area is an area to which a distance from the first terminal device is greater than or equal to a lower distance threshold and/or less than or equal to an upper distance threshold; or the specified area is an area in which strength of a signal received from the first terminal device is greater than or equal to a lower signal strength threshold and/or less than or equal to an upper signal strength threshold.

The sending module <NUM> is configured to send feedback information to the first terminal device.

In a possible design, the receiving module <NUM> is further configured to receive one or more of an upper distance threshold, a lower distance threshold, an upper signal strength threshold, and a lower signal strength threshold of the specified area from the first terminal device or a base station.

The communication apparatus <NUM> may be a terminal device, or may be a chip or a chip system disposed in a terminal device. This is not limited in this application.

In a possible design, the communication apparatus <NUM> may further include a storage module (not shown in <FIG>). The storage module is configured to store instructions, and the processing module <NUM> is configured to execute the instructions stored in the storage module, so that the processing module <NUM> performs the communication method or the distance determining method in the foregoing method embodiments.

An embodiment of this application provides a computer program product. The computer program product includes computer program code. When the computer program code is run on a computer, the computer is enabled to perform the communication method or the distance determining method in the foregoing method embodiments.

An embodiment of this application provides a readable storage medium. The readable storage medium stores a program or instructions. When the program or the instructions is/are run on a computer, the computer is enabled to perform the communication method or the distance determining method in the foregoing method embodiments.

It should be understood that, the processor in the embodiments of this application may be a central processing unit (central processing unit, CPU), or may be another general-purpose processor, a digital signal processor (digital signal processor, DSP), an application-specific integrated circuit (application-specific integrated circuit, ASIC), a field-programmable gate array (field-programmable gate array, FPGA), or another programmable logic device, a discrete gate or a transistor logic device, a discrete hardware component, or the like. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor or the like.

It should be further understood that the memory in the embodiments of this application may be a volatile memory or a non-volatile memory, or may include a volatile memory and a non-volatile memory. The non-volatile memory may be a read-only memory (read-only memory, ROM), a programmable read-only memory (programmable ROM, PROM), an erasable programmable read-only memory (erasable PROM, EPROM), an electrically erasable programmable read-only memory (electrically EPROM, EEPROM), or a flash memory. The volatile memory may be a random access memory (random access memory, RAM), and is used as an external cache. For example but not limitation, many forms of random access memories (random access memories, RAM) may be used such as a static random access memory (static RAM, SRAM), a dynamic random access memory (DRAM), a synchronous dynamic random access memory (synchronous DRAM, SDRAM), a double data rate synchronous dynamic random access memory (double data rate SDRAM, DDR SDRAM), an enhanced synchronous dynamic random access memory (enhanced SDRAM, ESDRAM), a synchlink dynamic random access memory (synchlink DRAM, SLDRAM), and a direct rambus random access memory (direct rambus RAM, DR RAM).

All or some of the foregoing embodiments may be implemented by software, hardware (for example, a circuit), firmware, or any combination thereof. When the software is used to implement the embodiments, all or some of the foregoing embodiments may be implemented in a form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or the computer programs are loaded or executed on a computer, all or some of the procedures or functions according to the embodiments of this application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or another programmable apparatus. The computer instructions may be stored in a computer-readable storage medium or may be transmitted from a computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center in a wired (for example, infrared, radio, or microwave) manner. The computer-readable storage medium may be any usable medium accessible by the computer, or a data storage device, for example, a server or a data center, integrating one or more usable media. The usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, or a magnetic tape), an optical medium (for example, a DVD), or a semiconductor medium. The semiconductor medium may be a solid-state drive.

It should be understood that the term "and/or" in the embodiments of this application describes only an association relationship for describing associated objects and represents that three relationships may exist. A and B may be singular or plural. In addition, the character "/" in this specification usually represents an "or" relationship between the associated objects, or may represent an "and/or" relationship. For details, refer to foregoing and following description for understanding.

In this embodiment of this application, "at least one" means one or more, and "a plurality of" means two or at least two. "At least one of the following items (pieces)" or a similar expression thereof means any combination of these items, including any combination of singular items (pieces) or plural items (pieces). For example, at least one item (piece) of a, b, or c may represent: a, b, c, a and b, a and c, b and c, or a, b, and c, where a, b, and c may be singular or plural.

In the embodiments of this application, the terms "first", "second", and the like are intended to distinguish between different objects or distinguish between different processing of a same object, but do not indicate a particular order of the objects.

In the embodiments of this application, the terms "include", "have", and any other variant thereof are intended to cover a non-exclusive inclusion. For example, a process, a method, a system, a product, or a device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes other unlisted steps or units, or further includes another inherent step or unit of the process, the method, the product, or the device.

In the embodiments of this application, the word "example" or "for example" is used to represent giving an example, an illustration, or description. Any embodiment or design scheme described as an "example" or "for example" in the embodiments of this application should not be explained as being more preferred or having more advantages than another embodiment or design scheme. Specifically, use of "example" or "for example" is intended to present a relative concept in a specific manner.

A person of ordinary skill in the art may be aware that, in combination with the examples described in the embodiments disclosed in this specification, units and algorithm steps can be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are performed by the hardware or the software depends on particular applications and design constraints of the technical solutions.

It may be clearly understood by the person skilled in the art that, for the purpose of convenient and brief description, for a detailed working process of the foregoing system, apparatus, and unit, refer to a corresponding process in the foregoing method embodiments.

For example, division into the units is merely logical function division and may be other division in an actual implementation. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented through some interfaces.

Units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected based on an actual requirement to achieve an objective of the solutions of the embodiments.

When the functions are implemented in a form of a software functional unit and sold or used as an independent product, the functions may be stored in a computer-readable storage medium. Based on such an understanding, the technical solutions of this application essentially, or the part contributing to the conventional technology, or some of the technical solutions may be implemented in a form of a software product. The computer software product is stored in a storage medium, and includes several instructions for instructing a computer device (which may be a personal computer, a server, or a network device) to perform all or some of the steps of the methods described in the embodiments of this application. The foregoing storage medium includes: any medium, for example, a USB flash drive, a removable hard disk, a read-only memory (read-only memory, ROM), a random access memory (random access memory, RAM), a magnetic disk, or an optical disc, that can store program code.

Claim 1:
A communication method performed by a first terminal device, wherein the communication method comprises the steps of:
• sending (S301) a first signal to a second terminal device; and
• receiving (S303) feedback information from the second terminal device when the second terminal device is located in a specified area, wherein:
∘ the specified area is an area to which a distance from the first terminal device is greater than or equal to a lower distance threshold and less than or equal to an upper distance threshold,
∘ wherein the feedback information comprises a negative acknowledgment, NACK, and/or channel state information, CSI, and the upper distance threshold is negatively correlated with a quantity of negative acknowledgments, NACKs, or an amount of channel state information, CSI, less than or equal to a first threshold, and the lower distance threshold is positively correlated with the quantity of negative acknowledgments, NACKs, or the amount of channel state information, CSI, less than or equal to the first threshold.