CN115529607A - Channel reciprocity calibration method, device and system - Google Patents

Abstract

The application discloses a method, a device and a system for calibrating channel reciprocity. On one hand, one STA is matched with the AP to carry out channel reciprocity calibration, and inaccurate calibration caused by signal leakage caused by self-sending and self-receiving is avoided. On the other hand, the AP calculates a channel reciprocity calibration coefficient for the STA and sends the channel reciprocity calibration coefficient to the STA, so that inaccurate calibration caused by self-sending and self-receiving of the STA is avoided. The method and the device do not need the STA to calculate the reciprocity calibration coefficient, and prevent the calibration coefficient from being large in calculation error due to weak calculation capability of the STA.

Description

Channel reciprocity calibration method, device and system

Technical Field

The embodiment of the application relates to the technical field of communication, in particular to a method, a device and a system for calibrating channel reciprocity.

Background

The purpose of Beamforming (BF) is: the energy of all transmitting antennas is focused to be aligned to a target receiving end, so that the energy waste is reduced, and the quality of received signals is improved. To improve the beamforming effect, the transmitter needs to know the channel information accurately. The current way for the transmitter to acquire the channel information includes: (1) Explicit feedback, an Access Point (AP) sends a training sequence, and then a Station (STA) feeds back measurement information after measuring a channel, so that the AP calculates a beamforming parameter according to the fed-back channel information. (2) Implicit feedback mainly utilizes the reciprocity of the uplink and the downlink of a time division multiplexing (TDD) channel and utilizes a receiving channel to estimate a transmitting channel, thereby not needing to feed back measurement information. However, when the uplink and downlink channels are not completely reciprocal, calibration needs to be performed on the radio frequency channel of the transceiver, which is called "reciprocity calibration".

At present, an explicit feedback mode is mostly adopted, but when the STA moves fast, the air interface overhead when feeding back the measurement information is large. The implicit feedback can reduce the air interface overhead brought by the explicit feedback, but the implicit feedback generally adopts a calibration mode of self-sending and self-receiving, that is, a part of antennas of the implicit feedback send reference signals and the rest of antennas of the implicit feedback receive the reference signals to calibrate the reciprocity, but the reference signals of self-sending and self-receiving belong to near-field signals and generate leakage, so that the reciprocity calibration result is influenced.

Disclosure of Invention

The embodiment of the application provides a method, a device and a system for calibrating channel reciprocity, which are used for solving the problem of low accuracy of channel reciprocity calibration.

In a first aspect, embodiments of the present application provide a channel reciprocity calibration method, which may be executed by an AP or a component in the AP, such as a processor, a chip, or a system-on-chip. In the method, an Access Point (AP) sends a first Null Data Packet (NDP) to a Station (STA), the first NDP including a first training sequence for estimating a transmission channel of the AP. The AP receives a first NDP feedback packet from the STA, the first NDP feedback packet comprises a second training sequence and a third training sequence generated by the STA, the second training sequence is obtained by the STA through analysis according to the first training sequence in the received first NDP, and the third training sequence is used for estimating a receiving channel of the AP. The AP estimates a transmitting channel of the AP according to the first training sequence and the second training sequence; and the AP estimates a receiving channel of the AP according to a third training sequence and a fourth training sequence, wherein the fourth training sequence is obtained by analyzing the AP according to the third training sequence in the received first NDP feedback packet. And obtaining the channel reciprocity calibration coefficient of the AP according to the transmitting channel of the AP and the receiving channel of the AP. Further, the AP may perform channel calibration according to the channel reciprocity calibration coefficient. In the embodiment of the application, one STA is matched with the AP to carry out channel reciprocity calibration, so that inaccurate calibration caused by signal leakage caused by self-sending and self-receiving is avoided. And the calculation of the calibration coefficient is not required to be performed by the STA, so that the condition that the more accurate calibration coefficient cannot be obtained due to the lower operation estimation algorithm caused by the STA power consumption or the processing resource limitation is prevented. The first training sequence is generated according to the maximum number of spatial streams supported by the AP, or the AP generates the first training sequence according to its own maximum spatial stream, or the number of LTF symbols included in the first training sequence in the first NDP packet satisfies the maximum number of spatial streams of the AP, and both satisfy the orthogonality requirement, so that the STA can resolve all spatial streams with a single antenna and can resolve differences of different antennas of the AP.

In some scenarios, the AP sends the first NDP according to its maximum number of transmit antennas and receives the first NDP feedback packet according to its maximum number of receive antennas to achieve channel calibration for each antenna.

In one possible design, the third training sequence includes a number of long training field LTFs that matches the maximum number of spatial streams supported by the AP. When the STA generates the third training sequence according to the maximum number of spatial streams supported by the AP, the number of long training fields LTFs included in the third training sequence is matched with the maximum number of spatial streams supported by the AP, so that the AP may obtain a signal reception result by averaging a plurality of received LTF symbols, which may suppress noise, thereby improving an estimation result.

In some embodiments, the number of long training fields LTFs included in the third training sequence generated by the STA is 1, and the AP at the receiving end receives the third training sequence according to the maximum number of receiving antennas, so that the difference of channels can be distinguished.

In one possible design, the second training sequence is one of: the original time domain sequence of the first training sequence, the frequency domain sequence of the original time domain sequence after frequency domain transformation, or the sequence of the original time domain sequence after least square processing, which is analyzed by the STA from the first NDP. In the above design, the second training sequence fed back by the STA adopts a sequence that has not been subjected to channel smoothing, and due to channel smoothing, the signal may lose some information, which results in a decrease in accuracy when the subsequent AP performs channel estimation.

In one possible design, the first NDP feedback packet is a physical layer protocol data unit, PPDU, and the second training sequence is carried in a data portion of the PPDU. In the above design, a training sequence for performing channel calibration in cooperation with the AP is carried in the data portion of the PPDU, that is, an STA is used in cooperation with the AP to perform channel reciprocity calibration, so that inaccurate calibration due to signal leakage caused by self-emission and self-reception is avoided, and the training sequence is carried in the data portion of the PPDU of the NDP feedback packet, which can reduce signaling interaction.

In one possible design, the method further includes: before the AP sends the first null data packet NDP to the STA, sending null data packet declaration NDPA to the STA, wherein the NDPA comprises indication information, and the indication information is used for indicating the AP to carry out channel reciprocity calibration through the STA. In the above design, the STA is notified of the cooperating AP for channel reciprocity calibration through the NDPA, so that the STA generates a training sequence for the cooperating AP and feeds back the received sequence to the AP.

In one possible design, the STA with the strongest signal in the coverage area of the AP is used to perform channel calibration with the AP, so as to improve accuracy.

In a second aspect, the present application provides a channel reciprocity calibration method, which may be performed by an STA or a component in the STA, such as a processor, a chip, or a system-on-chip. In the method, a station STA receives a first Null Data Packet (NDP) sent by an Access Point (AP), wherein the first NDP comprises a first training sequence used for estimating a transmission channel of the AP, and the first training sequence is generated according to the maximum number of spatial streams supported by the AP; the method comprises the steps that an STA sends a first NDP feedback packet to an AP, the first NDP feedback packet comprises a second training sequence and a third training sequence generated by the STA, the second training sequence is obtained by the STA through analysis according to the first training sequence, the second training sequence is used for estimating a transmitting channel of the AP, and the third training sequence is used for estimating a receiving channel of the AP.

In one possible design, the STA receives the first NDP transmitted by the AP via one receive antenna. The STA adopts one antenna as a reference antenna to realize the channel calibration of the AP, and the realization is simple and effective. In some scenarios, the STA may also receive the first NDP sent by the AP by using multiple antennas, and vector superposition of antenna patterns of the multiple antennas may be equivalent to a receiving effect of one antenna.

In one possible design, the STA sends the first NDP feedback packet to the AP via one transmit antenna. In some scenarios, the STA may also send the first NDP feedback packet to the AP through multiple antennas, so that the AP may use an average value of received results sent by the multiple antennas as a receiving result during verification, thereby further improving accuracy.

In one possible design, when the STA receives the first NDP packet using one receiving antenna and transmits the first NDP feedback packet using one transmitting antenna, the transmitting antenna and the receiving antenna may be the same antenna. The antenna may be the antenna with the highest signal strength or the best signal quality.

In one possible design, the third training sequence includes a number of long training field LTFs that matches the maximum number of spatial streams supported by the AP.

In one possible design, the first NDP feedback packet is a physical layer protocol data unit, PPDU, and the second training sequence is carried in a data portion of the PPDU.

In one possible design, the second training sequence is one of: the original time domain sequence of the first training sequence, the frequency domain sequence of the original time domain sequence after frequency domain transformation, or the sequence of the original time domain sequence after least square processing, which is analyzed by the STA from the first NDP.

In a third aspect, embodiments of the present application provide a channel reciprocity calibration method, which may be executed by an AP or a component in the AP, such as a processor, a chip, or a system-on-chip. In the method, an Access Point (AP) sends a second Null Data Packet (NDP) to a Station (STA), wherein the second NDP comprises a fifth training sequence; the AP receives a second NDP feedback packet from the STA, wherein the second NDP feedback packet comprises a sixth training sequence and a seventh training sequence generated by the STA, the sixth training sequence is obtained by the STA through analysis according to the fifth training sequence, and the seventh training sequence is generated according to the maximum number of spatial streams supported by the STA; the AP estimates a receiving channel of the STA according to the fifth training sequence and the sixth training sequence; the AP estimates a transmitting channel of the STA according to the seventh training sequence and an eighth training sequence obtained from the second NDP feedback packet; the AP obtains a channel reciprocity calibration coefficient of the STA according to the transmitting channel and the receiving channel; the AP sends the STA channel reciprocity calibration coefficients to the STA, and the channel reciprocity calibration coefficients are used for channel calibration of the STA. In the embodiment of the application, the AP calculates the channel reciprocity calibration coefficient for the STA, so that inaccuracy caused by signal leakage caused by self-sending and self-receiving of the STA is avoided, the STA is not required to perform calculation of the channel reciprocity calibration coefficient, and the phenomenon that channel estimation errors are large due to weak calculation capacity of the STA is prevented. The training sequence for estimating the STA channel is generated according to the maximum number of spatial streams, or the number of LTF symbols included in the NDP satisfies the maximum number of spatial streams of the STA, and all the LTF symbols satisfy the orthogonality requirement, so that the AP can resolve all the spatial streams with a single antenna and can resolve the differences of different antennas of the STA.

In one possible design, when the AP sends the second null data packet NDP to the STA, the AP sends the second NDP to the STA through one transmit antenna; when the AP receives the second NDP feedback packet from the STA, the AP receives the second NDP feedback packet from the STA through one receiving antenna.

In one possible design, the receive antenna and the transmit antenna are the same antenna.

In one possible design, the fifth training sequence includes a number of long training field LTFs that matches the maximum number of spatial streams supported by the STA. When the AP generates the second NDP, the second NDP is generated according to the maximum number of spatial streams supported by the STA, and the STA may transmit the received multiple LTF symbols to the AP, so that the AP may calculate an STA channel according to a reception result, may suppress noise, and may improve an estimation result.

Optionally, when the AP generates the second NDP, the number of long training fields LTFs included in the generated fifth training sequence is 1, and the receiving end STA may receive the second NDP according to the maximum number of receiving antennas, and may distinguish differences of channels according to a receiving result.

In one possible design, the sixth training sequence is one of: and the STA acquires an original time domain sequence of a fifth training sequence from the second NDP, a frequency domain sequence of the original time domain sequence after frequency domain transformation or a sequence of the original time domain sequence after least square processing.

In one possible design, the second NDP feedback packet is in a physical layer protocol data unit, PPDU, and the sixth training sequence is carried in a data portion of the PPDU.

In one possible design, the method further includes: and before the AP sends the second null data packet NDP to the STA, sending a null data packet declaration NDPA to the STA, wherein the NDPA comprises indication information, and the indication information is used for indicating the AP to carry out channel reciprocity calibration through the STA.

In a fourth aspect, the present application provides a channel reciprocity calibration method, which may be performed by an STA or a component in the STA, such as a processor, a chip or a system-on-chip. In the method, the STA receives a second null data packet NDP transmitted by the access point AP, the second NDP including a fifth training sequence for estimating a reception channel of the STA. The STA sends a second NDP feedback packet to the AP, the second NDP feedback packet comprises a sixth training sequence and a seventh training sequence generated by the STA, the sixth training sequence is obtained by the STA through analysis according to the fifth training sequence, and the sixth training sequence is used for estimating a receiving channel of the STA; the seventh training sequence is used for estimating a transmitting channel of the STA, and the seventh training sequence is generated according to the maximum number of spatial streams supported by the STA; the STA receives a channel reciprocity calibration coefficient of the STA sent by the AP, wherein the channel reciprocity calibration coefficient is obtained by the AP according to a transmitting channel and a receiving channel; and the STA carries out channel calibration according to the channel reciprocity calibration coefficient.

In some scenarios, the STA receives the second NDP according to its maximum number of receive antennas and transmits the second NDP feedback packet according to its maximum number of transmit antennas to achieve channel calibration for each antenna of the STA.

In one possible design, the fifth training sequence may include a number of long training fields LTFs that matches the maximum number of spatial streams supported by the STA.

In one possible design, the sixth training sequence is one of: the original time domain sequence of the first training sequence, the frequency domain sequence of the original time domain sequence after frequency domain transformation or the sequence of the original time domain sequence after least square processing are analyzed by the STA from the second NDP.

In one possible design, the second NDP feedback packet is a physical layer protocol data unit PPDU, and the sixth training sequence is carried in a data portion of the PPDU.

In a fifth aspect, the present application provides a communication apparatus, where the communication apparatus may implement the function of the AP in the above method design. These functions may be implemented by hardware, or by hardware executing corresponding software. The hardware or software includes one or more units corresponding to the above functions. For example, the communication device may include a processing unit, a transmitting unit, and a receiving unit. The processing unit, the transmitting unit and the receiving unit may perform the method provided in any of the possible designs of the first aspect or the third aspect described above.

In one possible design, a sending unit is configured to send a first null packet NDP to a station STA, where the first NDP includes a first training sequence used for estimating a transmission channel of a communication device, and the first training sequence is generated according to a maximum number of spatial streams supported by the communication device;

a receiving unit, configured to receive a first NDP feedback packet from an STA, where the first NDP feedback packet includes a second training sequence and a third training sequence generated by the STA, and the second training sequence is obtained by the STA through analysis according to the first training sequence;

a processing unit for estimating a transmission channel of the communication apparatus based on the first training sequence and the second training sequence; estimating a receiving channel of the communication device according to a third training sequence and a fourth training sequence, wherein the fourth training sequence is obtained by analyzing the third training sequence by a processing unit; obtaining a channel reciprocity calibration coefficient of the communication device according to a transmitting channel of the communication device and a receiving channel of the communication device; and carrying out channel calibration according to the channel reciprocity calibration coefficient.

In another possible design, the sending unit is configured to send a second null data packet NDP to the station STA, where the second NDP includes a fifth training sequence;

a receiving unit, configured to receive a second NDP feedback packet from the STA, where the second NDP feedback packet includes a sixth training sequence and a seventh training sequence generated by the STA, the sixth training sequence is obtained by parsing by the STA according to a fifth training sequence, and the seventh training sequence is generated according to a maximum number of spatial streams supported by the STA;

a processing unit, configured to estimate a receiving channel of the STA according to the fifth training sequence and the sixth training sequence; estimating a transmitting channel of the STA according to the seventh training sequence and an eighth training sequence, wherein the eighth training sequence is obtained by analyzing the seventh training sequence by the processing unit; obtaining a channel reciprocity calibration coefficient of the STA according to the transmitting channel and the receiving channel;

and the sending unit is also used for sending the channel reciprocity calibration coefficient of the STA to the STA, and the channel reciprocity calibration coefficient is used for the STA to carry out channel calibration.

In a sixth aspect, embodiments of the present application provide a communication device, where the communication device may implement the function of the STA in the above method design. These functions may be implemented by hardware, or by hardware executing corresponding software. The hardware or software includes one or more units corresponding to the above functions. For example, the communication device may include a processing unit, a transmitting unit, and a receiving unit. The processing unit, the transmitting unit and the receiving unit may perform the method provided in any one of the possible designs of the second or fourth aspect described above.

In one possible design, the receiving unit is configured to receive a first null data packet NDP sent by an access point AP, where the first NDP includes a first training sequence used for estimating a transmission channel of the AP, and the first training sequence is generated according to a maximum number of spatial streams supported by the AP;

the processing unit is used for obtaining a second training sequence according to the analysis of the first training sequence and generating a third training sequence, wherein the second training sequence is used for estimating a transmitting channel of the AP, and the third training sequence is used for estimating a receiving channel of the AP;

a sending unit, configured to send a first NDP feedback packet to the AP, where the first NDP feedback packet includes a second training sequence and a third training sequence.

In another possible design, the receiving unit is configured to receive a second null data packet NDP sent by the access point AP, where the second NDP includes a fifth training sequence for estimating a reception channel of the communication device;

the processing unit is used for obtaining a sixth training sequence according to the analysis of the fifth training sequence and generating a seventh training sequence according to the maximum number of spatial streams supported by the communication device, wherein the sixth training sequence is used for estimating a receiving channel of the communication device, and the seventh training sequence is used for estimating a transmitting channel of the communication device;

a sending unit, configured to send a second NDP feedback packet to the AP, where the second NDP feedback packet includes a sixth training sequence and a seventh training sequence;

the receiving unit is also used for receiving a channel reciprocity calibration coefficient of the communication device sent by the AP, wherein the channel reciprocity calibration coefficient is obtained by the AP according to a transmitting channel and a receiving channel;

and the processing unit is used for carrying out channel calibration according to the channel reciprocity calibration coefficient.

In a seventh aspect, an embodiment of the present application provides a communication apparatus, which may be a processor. The processor is coupled to a memory for storing a program or instructions which, when executed by the processor, cause the apparatus to perform the method as provided in any one of the possible designs of the first or third aspect.

In an eighth aspect, embodiments of the present application provide a communication device, which may be a processor. The processor is coupled to a memory for storing a program or instructions which, when executed by the processor, cause the apparatus to perform the method as provided in any one of the possible designs of the second aspect described above.

In a ninth aspect, embodiments of the present application provide a computer-readable storage medium, which stores a computer program, and when the computer program runs on a computer, the computer program causes the computer to execute the method provided in any one of the possible designs of the first aspect or the third aspect.

In a tenth aspect, embodiments of the present application provide a computer-readable storage medium, in which a computer program is stored, and when the computer program runs on a computer, the computer is caused to execute the method provided in any one of the possible designs of the second aspect or the fourth aspect.

In an eleventh aspect, the present application provides a computer program product, which when run on a computer causes the computer to perform the method provided in any one of the possible designs of the first or third aspects.

In a twelfth aspect, embodiments of the present application provide a computer program product, which when run on a computer, causes the computer to execute the method provided in any one of the possible designs of the second aspect or the fourth aspect.

In a thirteenth aspect, an embodiment of the present application provides a communication system, including a communication device for implementing the method provided in any one of the possible designs of the first aspect or the third aspect, and a communication device for implementing the method provided in any one of the possible designs of the second aspect.

In one possible design, a communication system includes an access point AP and a station STA;

the AP configured to send a first Null Data Packet (NDP) to the STA, where the first NDP includes a first training sequence used for estimating a transmission channel of the AP, and the first training sequence is generated according to a maximum number of spatial streams supported by the AP;

the STA is configured to send a first NDP feedback packet to the AP after receiving the first NDP, where the first NDP feedback packet includes a second training sequence and a third training sequence generated by the STA, and the second training sequence is obtained by analyzing according to the first training sequence by the STA;

the AP is further configured to estimate a transmission channel of the AP according to the first training sequence and the second training sequence after receiving the first NDP feedback packet; estimating a receiving channel of the AP according to the third training sequence and a fourth training sequence, wherein the fourth training sequence is obtained by analyzing the AP according to the third training sequence; obtaining a channel reciprocity calibration coefficient of the AP according to the transmitting channel and the receiving channel; and carrying out channel calibration according to the channel reciprocity calibration coefficient.

In another possible design, the communication system includes an access point AP and a station STA;

the AP is configured to send a second null data packet NDP to the STA, where the second NDP includes a fifth training sequence;

the STA is configured to send a second NDP feedback packet to the AP after receiving the second NDP, where the second NDP feedback packet includes a sixth training sequence and a seventh training sequence generated by the STA, the sixth training sequence is obtained by the STA through analysis according to the fifth training sequence, and the seventh training sequence is generated according to the maximum number of spatial streams supported by the STA;

the AP is further configured to estimate a reception channel of the STA according to the fifth training sequence and the sixth training sequence after receiving the second NDP feedback packet; estimating a transmission channel of the STA according to the seventh training sequence and an eighth training sequence, where the eighth training sequence is obtained by the AP through parsing according to the seventh training sequence; obtaining a channel reciprocity calibration coefficient of the STA according to the transmitting channel and the receiving channel; and sending the channel reciprocity calibration coefficient to the STA;

and the STA is further used for carrying out channel calibration according to the channel reciprocity calibration coefficient after receiving the channel reciprocity calibration coefficient.

For technical explanation that can be achieved by any one of the fifth aspect to the thirteenth aspect, please refer to any possible design-achievable effect explanation in any one of the first aspect to the fourth aspect, and repeated description is omitted here.

Drawings

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

FIG. 2A is a flowchart illustrating a channel reciprocity calibration method according to an embodiment of the present application;

FIG. 2B is a schematic diagram illustrating a channel reciprocity calibration interaction in an embodiment of the present application;

FIG. 3 is a diagram illustrating an NDP format according to an embodiment of the present application;

FIG. 4 is a diagram illustrating another NDP format according to an embodiment of the present application;

FIG. 5 is a diagram illustrating an NDP feedback packet format according to an embodiment of the present application;

FIG. 6 is a diagram illustrating another NDP feedback packet format according to an embodiment of the present application;

FIG. 7A is a flowchart illustrating another method for calibrating channel reciprocity according to an embodiment of the present invention;

FIG. 7B is an interaction diagram illustrating another exemplary channel reciprocity calibration method according to an embodiment of the present application;

FIG. 8 is a diagram illustrating channel reciprocity calibration performance in an embodiment of the present application;

fig. 9 is a schematic structural diagram of a communication device 900 according to an embodiment of the present application;

fig. 10 is a schematic structural diagram of a communication device 1000 according to an embodiment of the present application.

Detailed Description

In order to make the technical problems solved, technical solutions adopted, and technical effects achieved by the present application clearer, the technical solutions of the present application will be described in further detail below in the form of embodiments with reference to the accompanying drawings. Detailed descriptionvarious embodiments of devices and/or processes are presented using block diagrams, flowcharts, and/or examples. Since these block diagrams, flowcharts, and/or examples contain one or more functions and/or operations, it will be understood by those within the art that each function and/or operation within these block diagrams, flowcharts, or examples can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or any combination thereof.

In this application "plurality" means two or more. The term "and/or" in this application is only one kind of association relationship describing the association object, and means that there may be three kinds of relationships, for example, a and/or B, and may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter associated objects are in an "or" relationship. The terms "first", "second", and the like in the present application are used for distinguishing different objects, and do not limit the order of the different objects.

The technical solution of the present application may be applied to various communication systems, for example, a global system for mobile communications (GSM) system, a Code Division Multiple Access (CDMA) system, a Wideband Code Division Multiple Access (WCDMA) system, a General Packet Radio Service (GPRS), a Long Term Evolution (LTE) system, an LTE Frequency Division Duplex (FDD) system, an LTE Time Division Duplex (TDD), a universal mobile telecommunications system (universal mobile telecommunications system, UMTS), a universal microwave access (WLAN) system, a Wireless Local Area Network (WLAN) security system, or a WiFi communication system.

In this application, the terms "network" and "system" are often used interchangeably, but those skilled in the art will understand the meaning. All references to "Station (STA)"/"terminal" herein may in some cases refer to mobile devices such as mobile phones, personal digital assistants, handheld or laptop computers and similar devices with telecommunication capabilities, and in some cases also wearable devices, etc., and may also refer to any hardware or software component that may terminate a user's communication session. Further, "User terminal," User equipment, "" UE, "" terminal device, "" User equipment, "" User agent t, "" UA, "" User equipment, "" mobile device, "and" device "are all alternative terms synonymous herein with" Station (STA) "/" terminal. For convenience of description, the above-mentioned devices are collectively referred to as a station or STA in this application.

An "Access Point (AP)" mentioned in this application is a network device, and a device deployed in a radio access network to provide a wireless communication function for a terminal device can be responsible for scheduling and configuring uplink/downlink transmission of an STA. The access points may include various forms of macro base stations, micro base stations, relay stations, access points, and the like, including systems and devices that are improvements to peer devices in conventional wireless telecommunications systems. Such advanced or next generation devices may be included in a long term evolution, LTE, communication system, a 5G communication system, a future evolution system, or a multiple communication convergence system, and the names of devices having access point functions may be different in systems using different radio access technologies. For convenience of description, the above-mentioned devices providing the STA with the wireless communication function are collectively referred to as an access point or an AP in this application.

The term "antenna" as used herein may include any suitable configuration, structure and/or arrangement of one or more antenna elements, components, units, components and/or arrays. In some embodiments, the antenna may implement transmit and receive functions using separate transmit and receive antenna elements. In some embodiments, the antenna may implement transmit and receive functions using common and/or integrated transmit/receive elements. The antennas may include, for example, a phased array antenna, a single element antenna, a set of switched beam antennas, and so on.

In the embodiments of the present application, a WLAN system or a Wi-Fi system is taken as an example for description. The WLAN system or the Wi-Fi system includes an Access Point (AP) and a Station (STA), and the AP may be configured to communicate with the STA through a wireless local area network and transmit data of the STA to a network side or transmit data from the network side to the STA.

It should be understood that the embodiments of the present application are only illustrated with a WLAN system as an example, but the present application is not limited thereto, and the method and apparatus according to the embodiments of the present application may also be applied to other communication systems. Similarly, the embodiments of the present application also take the AP and the STA in the WLAN system as an example for illustration, but the present application is not limited thereto, and the method and apparatus according to the embodiments of the present application may also be applied to a base station and a user equipment in other communication systems.

Referring to fig. 1, an example of a Wireless Local Area Network (WLAN) network 100 architecture is shown. WLAN network 100 may include an AP110 and one or more wireless devices or STAs 120, each of which may associate with and communicate with AP110 via a communication link 130. Each AP110 has a geographic coverage area 140 so that STAs 120 within that area can typically communicate with that AP 110. STAs 120 may be dispersed throughout the geographic coverage area 140. Each STA120 may be fixed or mobile.

In some embodiments, STA120 may be covered by one or more APs 110. Thus, the STA120 may associate with one or more APs 110 at different times. WLAN network 100 may include different types of APs (e.g., metropolitan area networks, home networks, etc.) that may have coverage areas of different sizes and have overlapping coverage areas for different technologies. Other wireless devices may also communicate with the AP 110.

The WLAN network may be a multiple-input multiple-output (MIMO) network. In a WLAN, in the WLAN network 100, an AP110 may transmit messages, such as communication frames, to one or more STAs 120 simultaneously. The communication frame between the AP110 and the STA120 may include a Null Data Packet (NDP) or a Null Data Packet Announcement (NDPA) or a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PDU). The PLCP PDU may be referred to as a PPDU for short.

The AP110 includes one or more transmit antennas and one or more receive antennas. STA120 includes one or more transmit antennas and one or more receive antennas. In the embodiment of the present application, AP110 may transmit multiple spatial streams to STA120 through at least two transmit antennas. Each transmitting antenna can transmit a Spatial stream (Spatial stream). STA120 may receive one or more spatial streams transmitted by AP110 via one or more antennas. STA120 may transmit at least two spatial streams to AP110 via at least two transmit antennas. AP110 may receive one or more spatial streams transmitted by STA120 via one or more antennas.

It is to be appreciated that the protocol generally specifies the maximum number of spatial streams that can be supported by the AP based on the number of antennas of the AP and the maximum number of spatial streams that can be supported by the STA based on the number of antennas of the STA. Taking the AP as an example, the number of antennas of the AP is greater than or equal to the maximum number of spatial streams supported by the AP. In some scenarios, the number of antennas of the AP is equal to the maximum number of spatial streams supported by the AP. In some scenarios, the number of antennas of the AP is greater than the maximum number of spatial streams supported by the AP, for example, the maximum number of spatial streams supported by the AP is 4, but the AP includes 8 antennas, and each of the 8 antennas may be used as a transmitting antenna, and then one spatial stream may correspond to multiple transmitting antennas.

In the embodiment of the present application, a channel reciprocity calibration method is provided, which may implement, on one hand, channel reciprocity calibration of an AP, and in another way, channel reciprocity calibration of an STA.

The following describes a channel reciprocity calibration scheme for an AP in conjunction with a specific embodiment.

Referring to fig. 2A and fig. 2B, a flowchart of a possible method for calibrating channel reciprocity of an AP is shown.

201, the ap sends a Null Data Packet (NDP) including a training sequence to the station STA. The null packet is referred to herein as a first NDP for ease of distinction. The training sequence is referred to as a first training sequence, which is used to estimate the transmit channel of the AP.

Illustratively, the STA may be the STA with the strongest signal within the coverage of the AP. For example, the coverage area of the AP includes 10 STAs, and the AP selects the STA with the strongest signal from the 10 STAs to transmit the first NDP, so as to perform channel reciprocity calibration of the AP by using the STA with the strongest signal.

In some embodiments, the AP may transmit the first NDP to the STA by the maximum number of antennas of the AP. For example, the maximum number of antennas of the AP is M. The AP may send the first NDP to the STA through the M antennas.

In some embodiments, the AP may transmit the first NDP to the STA in accordance with a maximum number of spatial streams supported by the AP, or may be described as the AP generating the first training sequence in accordance with the maximum number of spatial streams supported by the AP. Illustratively, the number of Long Training Fields (LTFs) included in the first training sequence matches the maximum number of spatial streams supported by the AP. For example, the maximum number of spatial streams supported by the AP is 8, and the number of LTFs included in the first training sequence may be 8. Illustratively, the first NDP may employ a High Efficiency (HE), very High Throughput (VHT) or High Throughput (HT) packet format or Very High Throughput (VHT) or a combination format. For example, the first NDP may be in an HE message format, and the LTF included in the first training sequence may be referred to as an HE-LTF. The first NDP is in a VHT packet format, and the LTFs included in the first training sequence may be referred to as VHT-LTFs. The first NDP is in HT packet format, and the LTF included in the first training sequence may be referred to as HT-LTF. The first NDP is in a VHT message format, and the LTFs included in the first training sequence may be referred to as VHT-LTFs.

The protocol provides that the number of LTFs included in the training sequence is matched to the maximum number of spatial streams supported by the AP. It is generally satisfied that the number of LTFs included in the training sequence is greater than or equal to the maximum number of spatial streams supported by the AP. For example, the number of VHT-LTFs in a possible training sequence is matched to the maximum number of spatial streams supported by the AP, as shown in table 1. Table 1 is intended as an example only and not to be limiting.

TABLE 1

N sts,total (maximum number of spatial streams)	N VHT-LTF (number of LTFs)
		1	1
2	2
		3	4
4	4
		5	6
6	6
		7	8
8	8

In some embodiments, taking the example that the first NDP employs the HE message format, the first NDP includes a common preamble portion and a training sequence portion. The format of the first NDP can be seen in fig. 3, where M is an example of the maximum number of spatial streams supported by the AP in fig. 3. Ext> theext> commonext> preambleext> portionext> includesext> aext> transmissionext> shortext> trainingext> fieldext> Lext> -ext> STFext>,ext> aext> legacyext> longext> trainingext> fieldext> Lext> -ext> LTFext>,ext> aext> legacyext> signalingext> fieldext> Lext> -ext> SIGext>,ext> aext> repeatedext> legacyext> signalingext> fieldext> RLext> -ext> SIGext>,ext> andext> aext> signalingext> fieldext> Aext> (ext> e.g.ext>,ext> HEext> -ext> SIGext> -ext> Aext>)ext>.ext> The training sequence portion may include a short training field HE-STF and N long training fields HE-LTF. In other embodiments, the first NDP may not include the common preamble portion and may include a training sequence portion, as shown in fig. 4. The training sequence portion may include a short training field HE-STF and M long training fields HE-LTF.

202, the STA sends a first NDP feedback packet to the AP. The first NDP feedback packet includes the second training sequence and a third training sequence generated by the STA.

Illustratively, the second training sequence is parsed by the STA from the first training sequence in the first NDP. After receiving the first NDP, the STA performs a parsing operation on the first NDP, where the parsing operation includes parsing the first training sequence. It is understood that after the channel transmission, the signal may be attenuated, and for convenience of distinction, the training sequence obtained by the STA performing the parsing operation on the first training sequence in the first NDP is referred to as a second training sequence. The STA also generates a training sequence for estimating a reception channel of the AP, and the training sequence generated by the STA is referred to as a third training sequence for convenience of distinction. Alternatively, the STA may generate a third training sequence for estimating a reception channel of the AP according to the maximum number of spatial streams supported by the AP.

In some scenarios, the STA may receive the first NDP packet transmitted by the AP through one receive antenna.

In some scenarios, the STA may send the first NDP feedback packet to the AP through one transmit antenna.

The transmitting antenna and the receiving antenna may be different antennas or the same antenna. For example, when the same antenna is used, the antenna with the highest signal strength or the best quality among the antennas on the STA may be used for receiving the first NDP packet and transmitting the first NDP feedback packet.

In one example, the third training sequence generated by the STA includes 1 number of long training fields LTFs. Further, the receiving end AP receives according to the maximum number of receiving antennas, and the AP can distinguish the difference of channels. In another example, when the STA generates the third training sequence according to the maximum number of spatial streams supported by the AP, the number of long training fields LTFs included in the third training sequence matches the maximum number of spatial streams supported by the AP. Therefore, the AP can obtain a signal receiving result by averaging the received results of the plurality of LTF symbols, and can suppress noise, thereby improving the estimation result.

It should be noted that, in the connection establishment or handshake phase between the AP and the STA, the maximum number of spatial streams or the number of antennas supported by the AP may be interacted.

In one possible embodiment, the second training sequence fed back by the STA in the first NDP feedback packet may be an original time domain sequence of the first training sequence obtained by the STA from the first NDP. Or the second training sequence may be a frequency domain sequence obtained by transforming the original time domain sequence in the frequency domain. Or the second training sequence may be a sequence of the original time domain sequence after least square processing. In the embodiment of the application, the original time domain sequence, or the frequency domain sequence only subjected to frequency domain transformation or the sequence only subjected to least square processing are sequences without channel smoothing, and because the channel smoothing processing can cause signals to lose some information, the accuracy is reduced when the AP performs channel estimation subsequently, therefore, the sequence without channel smoothing is adopted, and the accuracy is higher when the AP performs channel estimation.

Alternatively, the first NDP feedback packet may be a Physical Protocol Data Unit (PPDU). The second training sequence may be carried in the data portion of the PPDU. Illustratively, the first NDP feedback packet may be in an HE, VHT, or HT message format or a combined format. For example, the first NDP feedback packet adopts an HE packet format, and the number of HE-LTFs included in the third training sequence matches the maximum number of spatial streams supported by the AP.

In some embodiments, the first NDP feedback includes a common preamble portion, a training sequence portion, and a data portion. The format of the first NDP feedback packet can be seen in fig. 5, where in fig. 5, the maximum number of spatial streams supported by the AP is M as an example. Ext> theext> commonext> preambleext> portionext> includesext> aext> transmissionext> shortext> trainingext> fieldext> Lext> -ext> STFext>,ext> aext> legacyext> longext> trainingext> fieldext> Lext> -ext> LTFext>,ext> aext> legacyext> signalingext> fieldext> Lext> -ext> SIGext>,ext> aext> repeatedext> legacyext> signalingext> fieldext> RLext> -ext> SIGext>,ext> andext> aext> signalingext> fieldext> Aext> (ext> e.g.ext>,ext> HEext> -ext> SIGext> -ext> Aext>)ext>.ext> The training sequence portion may include a short training field HE-STF generated by the STA and M long training fields HE-LTFs included in the third training sequence. The data portion includes a second training sequence.

In other embodiments, the first NDP feedback packet may not include the common preamble portion and may include a training sequence portion and a data portion, as shown in fig. 6. The training sequence portion may include a short training field HE-STF generated by the STA and M long training fields HE-LTFs included in the third training sequence. The data portion includes a second training sequence parsed from the first NDP.

203, the AP estimates a transmission channel of the AP according to the first training sequence and the second training sequence;

the AP estimates the AP's receive channel based on the third training sequence and the fourth training sequence 204.

Illustratively, the fourth training sequence is parsed by the AP according to the third training sequence in the first NDP feedback packet. After receiving the first NDP feedback packet, the AP first performs an analysis operation on the first NDP feedback packet, where the analysis operation includes analyzing a third training sequence. It is understood that after the channel transmission, the signal is attenuated, and for the convenience of distinction, the training sequence parsed from the first NDP feedback packet by the AP with respect to the third training sequence is referred to as a fourth training sequence.

It should be noted that, in the embodiment of the present application, the execution sequence of step 203 and step 204 is not specifically limited, for example, step 203 may be executed before step 204, or step 204 may be executed before step 203, or step 203 and step 204 may be executed simultaneously.

205, the AP obtains the channel reciprocity calibration coefficients of the AP according to the transmitting channel of the AP and the receiving channel of the AP.

206, the AP carries out channel calibration according to the channel reciprocity calibration coefficient. For example, in beamforming, channel calibration may be performed by reciprocity calibration coefficients.

According to the scheme provided by the embodiment of the application, the STA is matched with the AP to calibrate the channel reciprocity, so that the phenomenon that the channel calibration is inaccurate due to signal leakage caused by self-sending and self-receiving is avoided. And the STA is not needed to perform the calculation of the calibration coefficient, so that the condition that more accurate calibration coefficient cannot be obtained due to STA power consumption or processing resource limitation is prevented. The AP sends the NDP according to the maximum number of spatial streams, that is, the number of LTF symbols included in the NDP satisfies the maximum number of spatial streams of the AP, and both satisfy the orthogonality requirement, so that the STA can resolve all spatial streams with a single antenna and can resolve differences of different antennas of the AP.

In addition, the number of long training fields LTFs included in the third training sequence generated by the STA is 1, and the AP at the receiving end receives the third training sequence according to the maximum number of receiving antennas, which may also distinguish the difference of channels. When the STA generates the third training sequence according to the maximum number of spatial streams supported by the AP, the number of long training fields LTFs included in the third training sequence is matched with the maximum number of spatial streams supported by the AP, so that the AP may obtain a signal reception result by averaging a plurality of received LTF symbols, which may suppress noise and improve an estimation result.

As an example, the AP includes M antennas. The STA includes one or more antennas. When the STA includes multiple antennas, the antenna with the strongest signal is selected to transmit the first NDP feedback packet to the AP. LTF symbol data generated by the STA included in the first NDP feedback packet is M.

AP- > STA direction (transmit channel estimation):

for example, the AP transmits a signal X1 (corresponding to the first training sequence X1) _M×M ) Via a channel H1 (H1) _1×M ) When the STA is reached, the received signal of the STA is Y1 (corresponding to the second training sequence Y1) _1×M ). The relationship among X1, H1, and Y1 satisfies the condition shown in the following formula (1).

Y1 _1×M ＝H1 _1×M X1 _M×M (1)

The estimation result of the transmission channel of the AP can be expressed as formula (2):

wherein the content of the first and second substances,

it is shown that the pseudo-inverse operation,

representing the estimation of the transmit channel H1.

STA- > AP direction (receive channel estimation):

such as STA transmitting signal X2 (corresponding to the third training sequence X) _M×M ) Via channel H2 (H2) _1×M ) When the AP is reached, the received signal of the AP is Y2 (corresponding to the fourth training sequence Y2) _1×M )。

The relationship among X2, H2, and Y2 satisfies the condition shown in the following formula (3).

Y2 _M×1 ＝H2 _M×1 X2 _M×M (3)

The estimation result of the reception channel of the AP may be expressed as formula (4):

indicating the result of the estimation of the received channel H2.

Alternatively, correlation between channel subcarriers may be used before calculating reciprocity calibration results, and correlation between channel subcarriers may be used

Noise reduction is performed to further improve performance. Based on noise reduced

Reciprocity calibration results for the AP may be obtained. For example, the reciprocity calibration result is the calibration matrix δ. δ satisfies the condition shown in the following formula (5).

Wherein, the first and the second end of the pipe are connected with each other,

indicates the channel estimation result corresponding to the 1 st receiving antenna,

indicating the channel estimation result corresponding to the 1 st transmitting antenna, \8230 \ 8230;,

indicating the channel estimation result corresponding to the mth receiving antenna,

and representing the channel estimation result corresponding to the Mth transmitting antenna.

In a possible implementation manner, before sending the first NDP to the STA, the AP executes 201a, and sends a Null Data Packet Announcement (NDPA) to the STA to initiate a reciprocity calibration procedure of the AP. Indication information may be included in the NDPA, the indication information being used to indicate that the AP performs channel reciprocity calibration by the STA. Illustratively, the indication information may be carried in Sounding/calibration (Sounding/calibration) indicator bits of the NDPA. For example, the NDPA related to the present application may use a format of an HE-NDPA in a conventional 802.11ax protocol, and may also use a modification of the HE-NDPA in the conventional 802.11ax protocol, and the format of the NDPA is not specifically limited in this embodiment of the present application. After receiving the NDPA, the STA may listen to the NDP sent by the AP according to the indication information.

The channel reciprocity calibration scheme of the STA is described below with reference to specific embodiments.

Fig. 7A and 7B are schematic diagrams illustrating a possible method for calibrating channel reciprocity of STAs.

701, the ap sends a Null Data Packet (NDP) including a training sequence to the station STA. For ease of distinction, the null packet is referred to herein as a second NDP. To facilitate the distinction between the training sequences in the channel reciprocity calibration with the AP, the training sequence included in the second NDP is referred to as a fifth training sequence, and the fifth training sequence is used to estimate the reception channel of the STA.

In some embodiments, the AP may transmit the second NDP to the STA using one transmit antenna. For example, the AP includes M transmit antennas, and one transmit antenna with the strongest signal may be used to transmit the second NDP.

In one example, when the AP generates the second NDP, the fifth training sequence generated includes 1 number of long training fields LTFs. In another example, when generating the second NDP, the AP generates a fifth training sequence according to the maximum number of spatial streams supported by the STA, and the number of Long Training Fields (LTFs) included in the fifth training sequence matches the maximum number of spatial streams supported by the STA. For example, the STA includes 8 antennas, the maximum number of supported spatial streams is 8, and the number of long training field LTFs included in the fifth training sequence is 8. Illustratively, the second NDP may employ a High Efficiency (HE), very High Throughput (VHT), or High Throughput (HT) packet format or a combination format. For example, the format adopted by the second NDP is similar to the format of the first NDP, which is specifically described in the related description of the structure of the first NDP, and is not described herein again.

And 702, after the STA receives the second NDP, the STA sends a second NDP feedback packet to the AP. The second NDP feedback packet includes a sixth training sequence and a seventh training sequence generated by the STA.

Illustratively, the sixth training sequence is parsed by the STA according to the fifth training sequence in the second NDP. After receiving the second NDP, the STA performs a parsing operation on the second NDP, where the parsing operation includes parsing a fifth training sequence. It is to be understood that, after the channel transmission, the signal may be attenuated, and for convenience of distinction, a training sequence obtained by the STA performing an analysis operation on the fifth training sequence in the second NDP is referred to as a sixth training sequence. The STA also generates a training sequence for estimating a transmission channel of the STA, and for convenience of distinction, the training sequence generated by the STA for estimating the transmission channel of the STA is referred to as a seventh training sequence. Alternatively, the STA may generate a seventh training sequence for estimating a reception channel of the STA according to the maximum number of spatial streams supported by the STA.

Illustratively, when the STA generates the seventh training sequence according to the maximum number of spatial streams supported by the STA, the number of long training fields LTFs included in the third training sequence matches the maximum number of spatial streams supported by the STA.

In one possible embodiment, the sixth training sequence fed back by the STA in the second NDP feedback packet is an original time domain sequence of the fifth training sequence obtained by the STA from the first NDP. Or the sixth training sequence may be a frequency domain sequence obtained by frequency domain transforming the original time domain sequence. Or the sixth training sequence may be a sequence of the original time domain sequence after least square processing. In the embodiment of the application, the original time domain sequence, or the frequency domain sequence only subjected to frequency domain transformation or the sequence only subjected to least square processing is a sequence without channel smoothing, and because the channel smoothing processing can cause signals to lose some information, the accuracy is reduced when subsequent APs perform channel estimation, and therefore, the sequence without channel smoothing is adopted in the application, so that the AP is more accurate in channel estimation.

In some scenarios, the AP may send a second NDP packet to the STA via one transmit antenna.

In some scenarios, the AP may receive the second NDP feedback packet sent by the STA through one receive antenna.

The transmitting antenna and the receiving antenna may be different antennas or the same antenna. For example, when the same antenna is used, the antenna with the highest signal strength or the best quality among the antennas in the AP may be used for transmitting the second NDP packet and receiving the second NDP feedback packet.

Optionally, the second NDP feedback packet is a Physical Protocol Data Unit (PPDU). The sixth training sequence is carried in the data portion of the PPDU. Illustratively, the second NDP feedback packet may be in an HE, VHT, or HT message format or a combined format. For example, the second NDP feedback packet adopts an HE packet format, and the number of HE-LTFs included in the seventh training sequence matches the maximum number of spatial streams supported by the STA.

For example, the format of the second NDP feedback packet is similar to the format of the first NDP feedback packet, which is specifically referred to the related description of the structure of the first NDP feedback packet, and is not described herein again.

703, after the AP receives the second NDP feedback packet, the AP estimates a reception channel of the STA according to the fifth training sequence and the sixth training sequence.

The ap estimates the transmission channel of the STA based on the seventh training sequence and the eighth training sequence 704.

Illustratively, the eighth training sequence is parsed by the AP from the seventh training sequence in the second NDP feedback packet. After receiving the second NDP feedback packet, the AP first performs an analysis operation on the second NDP feedback packet, where the analysis operation includes analyzing a seventh training sequence. It is to be understood that after the channel transmission, the signal is attenuated, and for the convenience of distinction, the training sequence parsed from the second NDP feedback packet by the AP with respect to the seventh training sequence is referred to as an eighth training sequence.

It should be noted that, in the embodiment of the present application, the execution sequence of step 703 and step 704 is not specifically limited, for example, step 703 may be executed before step 704, or step 704 may be executed before step 703, or step 703 and step 704 may be executed simultaneously.

705, the ap obtains the channel reciprocity calibration coefficients of the STA according to the transmit channel of the STA and the receive channel of the STA.

706, the ap sends the STA's channel reciprocity calibration coefficients to the STA.

707, after receiving the channel reciprocity calibration factor, the sta performs channel calibration according to the channel reciprocity calibration factor.

According to the scheme provided by the embodiment of the application, the AP calibrates the channel reciprocity of the STA, the inaccurate calibration caused by signal leakage caused by self-sending and self-receiving is avoided, the STA is not required to execute calibration coefficient calculation, and the large channel estimation error caused by the weak computing power of the STA is prevented. The STA sends the NDP according to the maximum number of spatial streams, that is, the number of LTF symbols included in the NDP matches the maximum number of spatial streams of the STA, and both satisfy the orthogonality requirement, so that the AP can resolve all spatial streams with a single antenna and can resolve differences of different antennas of the STA. In addition, when the AP generates the second NDP, if the number of the long training fields LTFs included in the generated fifth training sequence is 1, the receiving end STA may receive the second NDP according to the maximum number of the receiving antennas, so that the difference of the channels may be distinguished according to the receiving result. When the AP generates the second NDP, if the fifth training field is generated according to the maximum number of spatial streams supported by the STA, the STA may transmit the received multiple LTF symbols to the AP, so that the AP may estimate an STA channel according to an average value of reception results of the respective symbols, may suppress noise, and may improve the estimation result.

In one possible implementation, before sending the second NDP to the STA, the AP performs 701a to send a Null Data Packet Announcement (NDPA) to the STA to initiate a reciprocity calibration procedure of the STA. Indication information may be included in the NDPA, the indication information indicating that channel reciprocity calibration is performed for the STA. For example, the indication information may be carried in Sounding/calibration (Sounding/calibration) indicator bits of the NDPA. As an example, the NDPA related to the present application may use a format of an HE-NDPA in a conventional 802.11ax protocol, and may also use a modification of the HE-NDPA in the conventional 802.11ax protocol, and the format of the NDPA is not specifically limited in this embodiment of the present application. After receiving the NDPA, the STA may listen to a second NDP sent by the AP according to the indication information.

In the embodiment of the application, the channel reciprocity coefficient calculation of the STA is carried out at the AP end, the AP can improve the estimation precision by 10-20 dB by using a higher-precision channel estimation algorithm, and the precision of TDD reciprocity calibration is improved. Referring to the performance after channel reciprocity calibration shown in fig. 8, it can be seen that as the calibration precision is improved, the performance of high-stream high-order Quadrature Amplitude Modulation (QAM) can be improved. In fig. 8, the horizontal axis represents signal-to-noise ratio (SNR) and the vertical axis represents Packet Error Rate (PER) taking 8 spatial streams and 8 STA scenarios as an example.

In the embodiments provided in the present application, the methods provided in the embodiments of the present application are introduced from the perspective of interaction between the AP and the STA. In order to implement the functions in the method provided by the embodiments of the present application, the AP and the STA may include a hardware structure and/or a software module, and implement the functions in the form of a hardware structure, a software module, or a hardware structure and a software module. Whether any of the above functions is implemented as a hardware structure, a software module, or a combination of a hardware structure and a software module depends upon the particular application and design constraints imposed on the technical solution.

Fig. 9 shows a schematic structural diagram of a communication device 900. The communications apparatus 900 can be a hardware structure, a software module, or a hardware structure plus a software module. The communication apparatus 900 may be implemented by a system-on-chip. In the embodiment of the present application, the chip system may be formed by a chip, and may also include a chip and other discrete devices.

The communication device 900 may comprise a processing unit 901 and a transmitting unit 902 and a receiving unit 903. In one example, the sending unit 902 may be a transmitter, the receiving unit 903 may be a receiver, the transmitter may include an antenna, a radio frequency circuit, and the like, the receiver may also include an antenna, a radio frequency circuit, and the like, the transmitter and the receiver may belong to one functional unit, for example, referred to as a transceiver, or the transmitter and the receiver may also be independent functional units; the processing unit 901 may be a processor, such as a baseband processor, which may include one or more Central Processing Units (CPUs). In another example, the sending unit 902 and the receiving unit 903 may be radio frequency units, and the processing unit 901 may be a processor, such as a baseband processor. In yet another example, the sending unit 902 and the receiving unit 903 may be an input/output interface of a chip (e.g., a baseband chip) (e.g., the sending unit 902 is an output interface, the receiving unit 903 is an input interface, or an input and an output are the same interface, and then both the sending unit 902 and the receiving unit 903 are the interfaces), and the processing unit 901 may be a processor of a chip system and may include one or more central processing units. It should be understood that the processing unit 901 in the embodiments of the present application may be implemented by a processor or a processor-related circuit component, the sending unit 902 may be implemented by a transmitter or a transmitter-related circuit component, and the receiving unit 903 may be implemented by a receiver or a receiver-related circuit component.

The sending unit 902 and the receiving unit 903 may be one functional unit, which may be called a transceiving unit, and the transceiving unit can perform both sending and receiving operations; alternatively, the sending unit 902 and the receiving unit 903 may also be two functional units, and the transceiving unit may be regarded as a general term of the two functional units, where the sending unit 902 is used to complete the sending operation, and the receiving unit 903 is used to complete the receiving operation.

In some scenarios, the communication apparatus 900 may be an AP in an embodiment shown in any one of fig. 2A to 2B and fig. 7A to 7B, and is capable of implementing the function of the AP in the method provided by the embodiment of the present application; the communication apparatus 900 may also be an apparatus capable of supporting an AP to implement the functions of the AP in the method provided by the embodiment of the present application.

In a possible implementation manner, the sending unit 902 is configured to send a first null data packet NDP to a station STA, where the first NDP includes a first training sequence used for estimating a transmission channel of a communication device, and the first training sequence is generated according to a maximum number of spatial streams supported by the communication device; a receiving unit 903, configured to receive a first NDP feedback packet from an STA, where the first NDP feedback packet includes a second training sequence and a third training sequence generated by the STA, and the second training sequence is obtained by the STA through analysis according to the first training sequence; a processing unit 901, configured to estimate a transmission channel of a communication apparatus according to a first training sequence and a second training sequence; estimating a receiving channel of the communication device according to a third training sequence and a fourth training sequence, where the fourth training sequence is obtained by parsing the processing unit 901 according to the third training sequence; obtaining a channel reciprocity calibration coefficient of the communication device according to a transmitting channel of the communication device and a receiving channel of the communication device; and carrying out channel calibration according to the channel reciprocity calibration coefficient.

As an example, the third training sequence includes a number of long training field LTFs that matches the maximum number of spatial streams supported by the AP.

As an example, the second training sequence is one of: an original time domain sequence of a first training sequence analyzed by the STA from the first NDP, a frequency domain sequence of the original time domain sequence after frequency domain transformation, or a sequence of the original time domain sequence after least square processing.

As an example, the first NDP feedback packet is a physical layer protocol data unit PPDU, and the second training sequence is carried in a data portion of the PPDU.

As an example, before the communication unit 902 sends the first null packet NDP to the STA, the null packet announcement NDPA is sent to the STA, and the NDPA includes indication information for indicating that the AP performs channel reciprocity calibration by the STA.

As an example, the STA is the STA with the strongest signal in the coverage area of the AP.

In a possible implementation manner, the sending unit 902 is configured to send a second null data packet NDP to the station STA, where the second NDP includes a fifth training sequence; a receiving unit 903, configured to receive a second NDP feedback packet from the STA, where the second NDP feedback packet includes a sixth training sequence and a seventh training sequence generated by the STA, the sixth training sequence is obtained by parsing by the STA according to a fifth training sequence, and the seventh training sequence is generated according to a maximum number of spatial streams supported by the STA; a processing unit 901, configured to estimate a receiving channel of the STA according to the fifth training sequence and the sixth training sequence; estimating a transmission channel of the STA according to the seventh training sequence and an eighth training sequence, where the eighth training sequence is obtained by analyzing the seventh training sequence by the processing unit 901; obtaining a channel reciprocity calibration coefficient of the STA according to the transmitting channel and the receiving channel; the sending unit 902 is further configured to send a channel reciprocity calibration coefficient of the STA to the STA, where the channel reciprocity calibration coefficient is used for channel calibration of the STA.

As an example, the fifth training sequence includes a number of long training field LTFs matching a maximum number of spatial streams supported by the STA.

As an example, the sixth training sequence is an original time domain sequence of the fifth training sequence obtained by the STA from the second NDP, or a frequency domain sequence obtained by frequency domain transforming the original time domain sequence, or a sequence obtained by least square processing the original time domain sequence.

As an example, the second NDP feedback packet is in a physical layer protocol data unit PPDU, and the sixth training sequence is carried in a data portion of the PPDU.

As an example, the sending unit 902 further sends a null packet announcement NDPA to the STA before sending the second null packet NDP to the STA, where the NDPA includes indication information for indicating that the AP performs channel reciprocity calibration by the STA.

As an example, the sending unit 902 sends the second NDP to the STA through one transmitting antenna; the receiving unit 903 receives the second NDP feedback packet from the STA through one receiving antenna. Illustratively, the receiving antenna and the transmitting antenna are the same antenna.

In some scenarios, the communication apparatus 900 may be an STA in the embodiment shown in any one of fig. 2A to 2B and fig. 7A to 7B, and is capable of implementing the functions of the STA according to the method provided by the embodiment of the present application; the communication apparatus 900 may also be an apparatus capable of supporting the STA to implement the functions of the STA in the method provided in the embodiment of the present application.

In a possible implementation manner, the receiving unit 903 is configured to receive a first null data packet NDP sent by an access point AP, where the first NDP includes a first training sequence used for estimating a transmission channel of the AP, and the first training sequence is generated according to a maximum number of spatial streams supported by the AP; a processing unit 901, configured to obtain a second training sequence according to the first training sequence, and generate a third training sequence, where the second training sequence is used to estimate a transmission channel of the AP, and the third training sequence is used to estimate a reception channel of the AP; a sending unit 902, configured to send a first NDP feedback packet to the AP, where the first NDP feedback packet includes the second training sequence and the third training sequence.

As an example, the first NDP feedback packet is a physical layer protocol data unit PPDU, and the second training sequence is carried in a data portion of the PPDU.

As an example, the receiving antenna and the transmitting antenna are the same antenna.

As an example, the second training sequence is one of: an original time domain sequence of a first training sequence analyzed by the STA from the first NDP, a frequency domain sequence of the original time domain sequence after frequency domain transformation, or a sequence of the original time domain sequence after least square processing.

As an example, the receiving unit 903 is further configured to receive a null data packet announcement, NDPA, from the AP before receiving the first NDP, where the NDPA includes indication information, and the indication information is used to indicate that the AP performs channel reciprocity calibration by the STA.

In a possible implementation manner, the receiving unit 903 is configured to receive a second null data packet NDP sent by the access point AP, where the second NDP includes a fifth training sequence used for estimating a receiving channel of the communications apparatus; a processing unit 901, configured to obtain a sixth training sequence according to the fifth training sequence, and generate a seventh training sequence according to the maximum number of spatial streams supported by the communication device, where the sixth training sequence is used to estimate a receiving channel of the communication device, and the seventh training sequence is used to estimate a transmitting channel of the communication device; a sending unit 902, configured to send a second NDP feedback packet to the AP, where the second NDP feedback packet includes a sixth training sequence and a seventh training sequence; a receiving unit 903, configured to receive a channel reciprocity calibration coefficient of the communication device sent by the AP, where the channel reciprocity calibration coefficient is obtained by the AP according to a transmitting channel and a receiving channel; a processing unit 901, configured to perform channel calibration according to the channel reciprocity calibration coefficient.

As an example, the fifth training sequence includes a number of long training field LTFs that matches the maximum number of spatial streams supported by the STA.

As an example, the sixth training sequence is one of: the original time domain sequence of the first training sequence, the frequency domain sequence of the original time domain sequence after frequency domain transformation or the sequence of the original time domain sequence after least square processing are analyzed by the STA from the second NDP.

As an example, the second NDP feedback packet is a physical layer protocol data unit, PPDU, and the sixth training sequence is carried in a data portion of the PPDU.

As an example, the receiving unit 903 is further configured to receive a null packet announcement, NDPA, from the AP before receiving the first NDP, where the NDPA includes indication information, and the indication information is used to indicate that the AP performs channel reciprocity calibration by the STA.

All relevant contents of each step related to the above method embodiment may be referred to the functional description of the corresponding functional module, and are not described herein again.

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

Fig. 10 illustrates a communication device 1000 according to an embodiment of the present disclosure, where the communication device 1000 may be a system on a chip. In the embodiment of the present application, the chip system may be composed of a chip, and may also include a chip and other discrete devices. In a hardware implementation, the communication unit 902 may be a transceiver, and the transceiver may be integrated in the communication interface 1010 in the communication device 1000.

Communications device 1000 may include at least one processor 1020 and, optionally, communications device 1000 may also include at least one memory 1030 for storing program instructions and/or data. A memory 1030 is coupled to the processor 1020. The coupling in the embodiments of the present application is an indirect coupling or communication connection between devices, units or modules, and may be in an electrical, mechanical or other form, which is used for information interaction between the devices, units or modules. The processor 1020 may operate in conjunction with the memory 1030. Processor 1020 may execute program instructions stored in memory 1030. At least one of the at least one memory may be included in the processor. Communications apparatus 1000 may also include a communications interface 1010 for communicating with other devices over a transmission medium such that the apparatus used in communications apparatus 1000 may communicate with other devices. The processor 1020 may transmit and receive data using the communication interface 1010. The communication interface 1010 may specifically be a transceiver.

In some scenarios, the communication apparatus 1000 may be an AP in an embodiment shown in any one of fig. 2A to 2B and fig. 7A to 7B, and is capable of implementing the function of the AP in the method provided by the embodiment of the present application; the communication apparatus 1000 may also be an apparatus capable of supporting the AP to implement the function of the AP in the method provided by the embodiment of the present application.

At least one processor 1020 configured to implement or support the communication apparatus 1000 to implement the functions of the AP in the method provided by the embodiment of the present application. For example, the processor 1020 may determine the transmission channel and the reception channel, and further determine the channel reciprocity calibration coefficient, which is specifically described in the detailed description of the method example and is not repeated herein.

Illustratively, communications apparatus 1000 is an AP and communication interface 1010 is configured to communicate with a STA via a transmission medium such that devices in communications apparatus 1000 may communicate with the STA.

In other scenarios, the communication apparatus 1000 may be an STA in the embodiment shown in any one of fig. 2A to 2B and fig. 7A to 7B, and is capable of implementing the function of the STA in the method provided by the embodiment of the present application; the communication apparatus 1000 may also be an apparatus capable of supporting the STA to implement the functions of the STA in the method provided in the embodiment of the present application.

At least one processor 1020 configured to implement or be used to support the communications apparatus 1000 to implement the functions of the STA in the method provided in the embodiments of the present application. For example, the processor 1020 may generate the NDP feedback packet, which is described in detail in the method example and is not described herein again. Illustratively, communications device 1000 is a STA and communications interface 1010 is used to communicate with an AP over a transmission medium so that devices used in communications device 1000 may communicate with the AP.

The specific connection medium among the communication interface 1010, the processor 1020 and the memory 1030 is not limited in the embodiment of the present application. In the embodiment of the present application, the memory 1030, the processor 1020, and the communication interface 1010 are connected by a bus 1040 in fig. 10, the bus is represented by a thick line in fig. 10, and the connection manner between other components is merely illustrative and not limited thereto. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 10, but this is not intended to represent only one bus or type of bus.

In the embodiment of the present application, the processor 1020 may be a general processor, a digital signal processor, an application specific integrated circuit, a field programmable gate array or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component, and may implement or execute the methods, steps, and logic blocks disclosed in the embodiment of the present application. A general purpose processor may be a microprocessor or any conventional processor or the like. The steps of a method disclosed in connection with the embodiments of the present application may be directly implemented by a hardware processor, or may be implemented by a combination of hardware and software modules in a processor.

In the embodiment of the present application, the memory 1030 may be a non-volatile memory, such as a Hard Disk Drive (HDD) or a solid-state drive (SSD), and may also be a volatile memory (RAM), for example, a random-access memory (RAM). The memory is any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer, but is not limited to such. The memory in the embodiments of the present application may also be circuitry or any other device capable of performing a storage function for storing program instructions and/or data.

Also provided in embodiments of the present application is a computer-readable storage medium, comprising instructions, which when executed on a computer, cause the computer to perform the method performed by the STA in the foregoing embodiments.

Also provided in an embodiment of the present application is a computer-readable storage medium, which includes instructions, when executed on a computer, cause the computer to perform the method performed by the AP in the foregoing embodiment.

Also provided in an embodiment of the present application is a computer program product including instructions, which when run on a computer, cause the computer to perform the method performed by the STA in the foregoing embodiment.

Also provided in an embodiment of the present application is a computer program product including instructions, which when executed on a computer, cause the computer to perform the method performed by the AP in the foregoing embodiment.

The embodiment of the present application provides a chip system, where the chip system includes a processor and may further include a memory, and is configured to implement the functions of the STA in the foregoing method. The chip system may be formed by a chip, and may also include a chip and other discrete devices.

The embodiment of the present application provides a chip system, where the chip system includes a processor and may further include a memory, and is configured to implement the function of the AP in the foregoing method. The chip system may be formed by a chip, and may also include a chip and other discrete devices.

An embodiment of the present application provides a communication system, where the communication system includes the STA and the AP in the foregoing embodiments.

The method provided by the embodiment of the present application may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the invention to occur, in whole or in part. The computer may be a general purpose computer, special purpose computer, computer network, network appliance, user equipment, or other programmable device. The computer instructions may be stored in or transmitted from a computer-readable storage medium to another computer-readable storage medium, e.g., from one website, computer, server, or data center, over a wired (e.g., coaxial cable, fiber optic, digital Subscriber Line (DSL), or wireless (e.g., infrared, wireless, microwave, etc.) network, the computer-readable storage medium may be any available medium that can be accessed by a computer or a data storage device including one or more integrated servers, data centers, etc. the available medium may be magnetic (e.g., floppy disks, hard disks, tapes), optical (e.g., digital Video Disks (DVDs)), or semiconductor media (e.g., SSDs), etc.

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

Claims (25)

1. A method for calibrating channel reciprocity, comprising:

an Access Point (AP) sends a first Null Data Packet (NDP) to a Station (STA), wherein the first NDP comprises a first training sequence used for estimating a transmission channel of the AP, and the first training sequence is generated according to the maximum number of spatial streams supported by the AP;

the AP receives a first NDP feedback packet from the STA, wherein the first NDP feedback packet comprises a second training sequence and a third training sequence generated by the STA, and the second training sequence is obtained by the STA through analysis according to the first training sequence;

the AP estimates a transmitting channel of the AP according to the first training sequence and the second training sequence;

the AP estimates a receiving channel of the AP according to the third training sequence and a fourth training sequence, wherein the fourth training sequence is obtained by analyzing the AP according to the third training sequence;

the AP obtains a channel reciprocity calibration coefficient of the AP according to the transmitting channel and the receiving channel;

and the AP carries out channel calibration according to the channel reciprocity calibration coefficient.

2. The method of claim 1, wherein the third training sequence comprises a number of Long Training Field (LTFs) matching a maximum number of spatial streams supported by the AP.

3. A method according to claim 1 or 2, wherein the second training sequence is one of: the original time domain sequence of the first training sequence, the frequency domain sequence of the original time domain sequence after frequency domain transformation, or the sequence of the original time domain sequence after least square processing, which is analyzed by the STA from the first NDP.

4. The method of any of claims 1-3, wherein the first NDP feedback packet is a physical layer protocol data unit (PPDU), and wherein the second training sequence is carried in a data portion of the PPDU.

5. The method of any one of claims 1-4, further comprising:

before the AP sends a first Null Data Packet (NDP) to the STA, the AP sends a null data packet declaration (NDPA) to the STA, wherein the NDPA comprises indication information, and the indication information is used for indicating the AP to carry out channel reciprocity calibration through the STA.

6. The method of any of claims 1-5, wherein the STA is the strongest signal STA within the coverage area of the AP.

7. A method for calibrating channel reciprocity, comprising:

a Station (STA) receives a first Null Data Packet (NDP) sent by an Access Point (AP), wherein the first NDP comprises a first training sequence used for estimating a transmission channel of the AP, and the first training sequence is generated according to the maximum number of spatial streams supported by the AP;

the STA sends a first NDP feedback packet to the AP, wherein the first NDP feedback packet comprises a second training sequence and a third training sequence generated by the STA, the second training sequence is obtained by the STA through analysis according to the first training sequence, the second training sequence is used for estimating a transmitting channel of the AP, and the third training sequence is used for estimating a receiving channel of the AP.

8. The method of claim 7, wherein the third training sequence comprises a number of Long Training Field (LTFs) matching a maximum number of spatial streams supported by the AP.

9. The method of claim 7 or 8, wherein the second training sequence is one of: the original time domain sequence of the first training sequence, the frequency domain sequence of the original time domain sequence after frequency domain transformation, or the sequence of the original time domain sequence after least square processing, which is analyzed by the STA from the first NDP.

10. The method of any of claims 7-9, wherein the first NDP feedback packet is a physical layer protocol data unit, PPDU, and the second training sequence is carried in a data portion of the PPDU.

11. A method for calibrating channel reciprocity, comprising:

an Access Point (AP) sends a second Null Data Packet (NDP) to a Station (STA), wherein the second NDP comprises a fifth training sequence;

the AP receives a second NDP feedback packet from the STA, where the second NDP feedback packet includes a sixth training sequence and a seventh training sequence generated by the STA, the sixth training sequence is obtained by the STA through parsing according to the fifth training sequence, and the seventh training sequence is generated according to the maximum number of spatial streams supported by the STA;

the AP estimates a receiving channel of the STA according to the fifth training sequence and the sixth training sequence;

the AP estimates a transmitting channel of the STA according to the seventh training sequence and an eighth training sequence, wherein the eighth training sequence is obtained by analyzing the seventh training sequence by the AP;

the AP obtains a channel reciprocity calibration coefficient of the STA according to the transmitting channel and the receiving channel;

and the AP sends a channel reciprocity calibration coefficient of the STA to the STA, and the channel reciprocity calibration coefficient is used for the STA to carry out channel calibration.

12. The method of claim 11, wherein the fifth training sequence comprises a number of Long Training Field (LTFs) matching a maximum number of spatial streams supported by the STA.

13. The method of claim 11 or 12, wherein the sixth training sequence is one of: an original time domain sequence of the fifth training sequence, a frequency domain sequence of the original time domain sequence after frequency domain transformation, or a sequence of the original time domain sequence after least square processing, which is obtained by the STA from the second NDP.

14. The method of any of claims 11-13, wherein the second NDP feedback packet is a physical layer protocol data unit, PPDU, and the sixth training sequence is carried in a data portion of the PPDU.

15. The method of any one of claims 11-14, further comprising:

before the AP sends a second Null Data Packet (NDP) to the STA, sending a null data packet declaration (NDPA) to the STA, wherein the NDPA comprises indication information, and the indication information is used for indicating the AP to carry out channel reciprocity calibration through the STA.

16. A method for calibrating channel reciprocity, comprising:

a Station (STA) receives a second Null Data Packet (NDP) sent by an Access Point (AP), wherein the second NDP comprises a fifth training sequence used for estimating a receiving channel of the STA;

the STA sends a second NDP feedback packet to the AP, wherein the second NDP feedback packet comprises a sixth training sequence and a seventh training sequence generated by the STA, the sixth training sequence is obtained by the STA through analysis according to the fifth training sequence, and the sixth training sequence is used for estimating a receiving channel of the STA; the seventh training sequence is used for estimating a transmission channel of the STA, and the seventh training sequence is generated according to the maximum number of spatial streams supported by the STA;

the STA receives a channel reciprocity calibration coefficient of the STA sent by the AP, wherein the channel reciprocity calibration coefficient is obtained by the AP according to the transmitting channel and the receiving channel;

and the STA carries out channel calibration according to the channel reciprocity calibration coefficient.

17. The method of claim 16, wherein the fifth training sequence comprises a number of Long Training Field (LTFs) matching a maximum number of spatial streams supported by the STA.

18. The method of claim 16 or 17, wherein the sixth training sequence is one of: the original time domain sequence of the first training sequence, the frequency domain sequence of the original time domain sequence after frequency domain transformation, or the sequence of the original time domain sequence after least square processing, which is analyzed by the STA from the second NDP.

19. The method of any of claims 16-18, wherein the second NDP feedback packet is a physical layer protocol data unit, PPDU, and the sixth training sequence is carried in a data portion of the PPDU.

20. A communication apparatus, characterized in that the communication apparatus comprises:

a sending unit, configured to send a first null data packet NDP to a station STA, where the first NDP includes a first training sequence used for estimating a transmission channel of the communication device, and the first training sequence is generated according to a maximum number of spatial streams supported by the communication device;

a receiving unit, configured to receive a first NDP feedback packet from the STA, where the first NDP feedback packet includes a second training sequence and a third training sequence generated by the STA, and the second training sequence is obtained by analyzing the first training sequence by the STA;

the processing unit is configured to estimate a transmission channel of the communication apparatus according to the first training sequence and the second training sequence; estimating a receiving channel of the communication device according to the third training sequence and a fourth training sequence, wherein the fourth training sequence is obtained by analyzing according to the third training sequence by the processing unit; obtaining a channel reciprocity calibration coefficient of the communication device according to a transmitting channel of the communication device and a receiving channel of the communication device; and carrying out channel calibration according to the channel reciprocity calibration coefficient.

21. A communication apparatus, characterized in that the communication apparatus comprises:

a receiving unit, configured to receive a first null data packet NDP sent by an access point AP, where the first NDP includes a first training sequence used for estimating a transmission channel of the AP, and the first training sequence is generated according to a maximum number of spatial streams supported by the AP;

a processing unit, configured to obtain a second training sequence according to the first training sequence, and generate a third training sequence, where the second training sequence is used to estimate a transmission channel of the AP, and the third training sequence is used to estimate a reception channel of the AP;

a sending unit, configured to send a first NDP feedback packet to the AP, where the first NDP feedback packet includes the second training sequence and the third training sequence.

22. A communication apparatus, characterized in that the communication apparatus comprises:

a sending unit, configured to send a second null data packet NDP to a station STA, where the second NDP includes a fifth training sequence;

a receiving unit, configured to receive a second NDP feedback packet from the STA, where the second NDP feedback packet includes a sixth training sequence and a seventh training sequence generated by the STA, the sixth training sequence is obtained by the STA through parsing according to the fifth training sequence, and the seventh training sequence is generated according to a maximum number of spatial streams supported by the STA;

a processing unit, configured to estimate a receiving channel of the STA according to the fifth training sequence and the sixth training sequence; estimating a transmitting channel of the STA according to the seventh training sequence and an eighth training sequence, where the eighth training sequence is obtained by parsing by the processing unit according to the seventh training sequence; obtaining a channel reciprocity calibration coefficient of the STA according to the transmitting channel and the receiving channel;

the sending unit is further configured to send a channel reciprocity calibration coefficient of the STA to the STA, where the channel reciprocity calibration coefficient is used for channel calibration of the STA.

23. A communication apparatus, characterized in that the communication apparatus comprises:

a receiving unit, configured to receive a second null data packet NDP sent by an access point AP, where the second NDP includes a fifth training sequence for estimating a receiving channel of the communication device;

a processing unit, configured to obtain a sixth training sequence according to the fifth training sequence, and generate a seventh training sequence according to a maximum number of spatial streams supported by the communication apparatus, where the sixth training sequence is used to estimate a receiving channel of the communication apparatus, and the seventh training sequence is used to estimate a transmitting channel of the communication apparatus;

a sending unit, configured to send a second NDP feedback packet to the AP, where the second NDP feedback packet includes the sixth training sequence and the seventh training sequence;

the receiving unit is further configured to receive a channel reciprocity calibration coefficient of the communication device sent by the AP, where the channel reciprocity calibration coefficient is obtained by the AP according to the transmission channel and the reception channel;

and the processing unit is used for carrying out channel calibration according to the channel reciprocity calibration coefficient.

24. A communication system, comprising an Access Point (AP) and a Station (STA);

the AP configured to send a first Null Data Packet (NDP) to the STA, where the first NDP includes a first training sequence used for estimating a transmission channel of the AP, and the first training sequence is generated according to a maximum number of spatial streams supported by the AP;

the STA is configured to send a first NDP feedback packet to the AP after receiving the first NDP, where the first NDP feedback packet includes a second training sequence and a third training sequence generated by the STA, and the second training sequence is obtained by analyzing according to the first training sequence by the STA;

the AP is further configured to estimate a transmission channel of the AP according to the first training sequence and the second training sequence after receiving the first NDP feedback packet; estimating a receiving channel of the AP according to the third training sequence and a fourth training sequence, wherein the fourth training sequence is obtained by analyzing the AP according to the third training sequence; obtaining a channel reciprocity calibration coefficient of the AP according to the transmitting channel and the receiving channel; and carrying out channel calibration according to the channel reciprocity calibration coefficient.

25. A communication system, comprising an access point AP and a station STA;

the AP is configured to send a second null data packet NDP to the STA, where the second NDP includes a fifth training sequence;

the STA is configured to send a second NDP feedback packet to the AP after receiving the second NDP, where the second NDP feedback packet includes a sixth training sequence and a seventh training sequence generated by the STA, the sixth training sequence is obtained by parsing by the STA according to the fifth training sequence, and the seventh training sequence is generated according to a maximum number of spatial streams supported by the STA;

the AP is further configured to estimate a reception channel of the STA according to the fifth training sequence and the sixth training sequence after receiving the second NDP feedback packet; estimating a transmitting channel of the STA according to the seventh training sequence and an eighth training sequence, where the eighth training sequence is obtained by parsing by the AP according to the seventh training sequence; obtaining a channel reciprocity calibration coefficient of the STA according to the transmitting channel and the receiving channel; and sending the channel reciprocity calibration coefficient to the STA;

and the STA is further used for carrying out channel calibration according to the channel reciprocity calibration coefficient after receiving the channel reciprocity calibration coefficient.

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