Communication method and communication apparatus

Abstract

Provided in the present application are a communication method and a communication apparatus. The method provides a first basis or a channel covariance matrix for determining the first basis, wherein the first basis is a regional channel basis provided by a channel chart, or the channel covariance matrix is a regional channel covariance matrix provided by the channel chart, which can be used as prior information to be sent to a terminal, which is conducive to reducing the overheads of a reference signal. Moreover, after performing channel measurement on the basis of the reference signal, the terminal can only feed back the position index of the first basis without the need to feed back information, such as the index of one or more basis vectors constituting the first basis, and long-period coefficients, which is conducive to reducing the feedback overheads.

Description

Communication method and communication device

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on December 7, 2023, with application number 202311683910.X, and priority to the Chinese patent application entitled “A Communication Method and Communication Device”, all contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of communication technology, and in particular to a communication method and a communication device. Background Art

[0003] At present, the solution for channel reconstruction based on reference signals has the problems of large reference signal resource overhead and long-period basis feedback overhead. For example, the codebook of the 3rd Generation Partnership Project (3GPP) version 16 (release 16, R16) only utilizes the sparse characteristics of the channel in the angle-delay domain, and needs to report the spatial domain, frequency domain basis and combination coefficients, resulting in a large feedback overhead. For another example, the codebook of 3GPP version 18 (release 18, R18) further considers the sparse characteristics of the channel, and considers the inconsistent changes in the speed of different channel characteristics over time, and designs a codebook feedback method that combines long and short periods to reduce feedback overhead; however, as the number of antennas increases, the reference signal overhead that needs to be configured increases sharply, and the feedback overhead also increases sharply. Summary of the Invention

[0004] This application provides a communication method and device that can transmit a first basis as prior information to a first device, thereby reducing reference signal overhead. Furthermore, the first device only feeds back a position index and a short-period superposition coefficient based on the first basis, thereby reducing feedback overhead.

[0005] In a first aspect, the present application provides a communication method, which is performed by a first device. For example, the first device can be a terminal, or a component of the terminal (such as a processor, chip, or chip system), or a logic module that can implement all or part of the terminal functions. The first device receives indication information of a first basis, which indicates the projection coefficients of the first basis on a quantization basis of the first basis and the column index of the quantization basis of the first basis. After receiving the indication information of the first basis, the first device can determine and record the first basis. The first device receives a first reference signal and determines a first channel matrix based on the first reference signal. Furthermore, the first device can determine a first superposition coefficient vector based on a second basis constructed by indexing the positions of the first channel matrix and the first reference signal in the space-frequency domain corresponding to the rows of the first basis. For example, assuming that the dimension of the first channel matrix is ​​MN1*1 and the dimension of the second basis is MN1*L, M is the number of antenna ports receiving the first reference signal, N1 is the number of frequency domain elements carrying the first reference signal, the first superposition coefficient vector includes L superposition coefficients, the dimension of the first superposition coefficient vector is L*1, M and N1 are positive integers, and L is less than or equal to MN1. The first device may select K superposition coefficient vectors with the largest amplitudes from the first superposition coefficient vector to form a second superposition coefficient vector, and determine position indexes of the K superposition coefficient vectors in the first superposition coefficient vector to form a second basis selection vector. Further, the first device may transmit the second superposition coefficient vector and the second basis selection vector.

[0006] In this method, a first device may receive indication information of a first basis and a first reference signal. The first reference signal may be a sparse reference signal, which is beneficial for reducing reference signal overhead. Furthermore, based on the indication information of the first basis, the first device may determine the position index of the first reference signal in the space-frequency domain corresponding to the row of the first basis. This allows the first device to calculate and report short-cycle coefficients (such as a second superposition coefficient vector) in combination with the channel estimation result of the sparse reference signal, which is beneficial for reducing feedback overhead.

[0007] The present application also provides a communication method, which is different from the previous communication method in that the indication information of the first basis indicates the projection coefficients of the channel covariance matrix on the quantization basis and the corresponding indexes of the projection coefficients on the quantization basis; in this way, the first device can determine the channel covariance matrix based on the indicated projection coefficients and indexes of the channel covariance matrix; perform singular value decomposition or eigendecomposition on the channel covariance matrix to obtain the first basis corresponding to the channel covariance matrix, and then perform subsequent operations in the previous communication method, such as receiving a first reference signal and determining a first channel matrix based on the first reference signal; determining a first superposition coefficient vector based on a second basis constructed based on the position indexes of the first channel matrix and the first reference signal in the space-frequency domain corresponding to the rows of the first basis; sending a second superposition coefficient vector and a second basis selection vector, the second superposition coefficient vector including K superposition coefficients; the second basis selection vector including the position indexes of the K superposition coefficients in the first superposition coefficient vector, K being a positive integer less than or equal to L.

[0008] In this method, the first reference signal in the first device remains a sparse reference signal, which helps reduce reference signal overhead. Furthermore, based on the first basis, the first device can calculate and report the second superposition coefficient vector in combination with the channel estimation result of the sparse reference signal, which helps reduce feedback overhead.

[0009] Optionally, the indication information of the first basis may indicate: the first L diagonal elements of the projection coefficient matrix of the channel covariance matrix on the quantization basis with the largest numerical value or quantization value. delay projection coefficients, and the front L delay The index corresponding to each projection coefficient on the quantized basis. Since the diagonal elements of the projection coefficient matrix are real numbers, indicating the diagonal elements can reduce the indication overhead. In one possible implementation, the first device multiplies the second superposition coefficient vector by a third basis to obtain a second channel matrix; the third basis is composed of the K position indices in the second basis selection vector corresponding to the columns of the first basis.

[0010] In this method, the first device can determine the projection of the channel matrix based on the corresponding columns of the K position indices on the first basis. The channel matrix can be restored by combining the projection of the channel matrix with the short-cycle coefficient, which is conducive to reducing computational overhead.

[0011] In one possible implementation, the first device performs channel estimation based on a second reference signal to obtain a third channel matrix, where the second reference signal is a reference signal received before the first reference signal, and the second reference signal and the first reference signal are reference signals of the same type. The first device determines a fourth basis based on the third channel matrix, and determines that the common subspace where the fourth basis intersects with the first basis is the first common subspace, and determines that the subspace in the fourth basis excluding the first common subspace is the first non-common subspace. The first device sends indication information of the first non-common subspace, and the indication information of the first non-common subspace indicates the projection coefficient of the first non-common subspace on the quantization basis of the first non-common subspace and the column index of the quantization basis of the first non-common subspace; the first non-common subspace is composed of L1 column basis vectors, where L1 is a positive integer.

[0012] In this method, the first device can further perform channel estimation on the second reference signal (also called the historical reference signal) to obtain a third channel matrix (also called the historical channel matrix), so that the first device can determine the projection of the historical channel matrix. Further, the first device can determine a first non-common subspace, that is, the first non-common subspace is a non-common subspace of the projection of the historical channel matrix and the projection of the current channel matrix, representing the difference between the projection of the historical channel matrix and the projection of the current channel matrix, thereby facilitating the updating of the first basis based on the difference and improving the accuracy of the channel estimation.

[0013] In a possible implementation, the first device receives first indication information indicating a frequency domain location for sending a third reference signal, and sends the third reference signal based on the first indication information.

[0014] In this method, the first device can also receive first indication information of a third reference signal (such as an uplink reference signal), and thus send the third reference signal based on the indication of the first indication information, so that the receiving end of the third reference signal can perform channel estimation based on the third reference signal to restore channel state information.

[0015] In a second aspect, the present application provides a communication method, which is performed by a second device. For example, the second device can be a network device (such as a base station), or a component of the network device (such as a processor, chip, or chip system), or a logic module that can implement all or part of the network device functions. The second device sends indication information of a first basis, and the indication information of the first basis indicates the projection coefficient of the first basis on the quantization basis of the first basis and the column index of the quantization basis of the first basis. The second device sends a first reference signal, so that the receiving end of the first reference signal can perform channel estimation based on the first reference signal to obtain a first channel matrix, and the receiving end of the first reference signal can determine a first superposition coefficient vector based on a second basis constructed by the position index of the first channel matrix and the first reference signal in the space-frequency domain corresponding to the row of the first basis, thereby determining to select the K superposition coefficient vectors with the largest amplitude in the first superposition coefficient vector to form a second superposition coefficient vector, and the position index of the K superposition coefficient vectors in the first superposition coefficient vector to form a second basis selection vector. The second device receives the second superposition coefficient vector and the second basis selection vector.

[0016] In this method, the second device can determine a first basis and transmit an indication of the first basis and a first reference signal. The first reference signal can be a sparse reference signal, which helps reduce reference signal overhead. Furthermore, the second device receives a relatively small amount of data in the second superposition coefficient vector and the second basis selection vector, indicating low feedback overhead. Furthermore, based on these two types of feedback and the first basis, the second device can recover channel state information.

[0017] In another embodiment, the present application also provides a communication method, which differs from the previous communication method in that the indication information of the first basis indicates the projection coefficients of the channel covariance matrix on the quantized basis and the corresponding indexes of the projection coefficients on the quantized basis; so that the first device can first restore the channel covariance matrix based on the indicated projection coefficients and indexes of the channel covariance matrix, and then perform singular value decomposition or eigendecomposition on the channel covariance matrix to obtain the first basis corresponding to the channel covariance matrix. Furthermore, the second device sends a first reference signal and can correspondingly receive a second superposition coefficient vector and a second basis selection vector; the second device can restore the channel state information based on the received second superposition coefficient vector and the second basis selection vector.

[0018] In this method, the second device transmits indication information of the first basis and a first reference signal. The first reference signal can be a sparse reference signal, which helps reduce reference signal overhead. Furthermore, the second device receives a smaller amount of data for the second superposition coefficient vector and the second basis selection vector, resulting in lower feedback overhead.

[0019] Optionally, the indication information of the first basis may indicate: the first L diagonal elements of the projection coefficient matrix of the channel covariance matrix on the quantization basis with the largest numerical value or quantization value. delay projection coefficients, and the front L delay The index corresponding to each projection coefficient on the quantized basis. Since the diagonal elements of the projection coefficient matrix are real numbers, indicating the diagonal elements can reduce the indication overhead.

[0020] In a possible implementation, the second device multiplies the second superposition coefficient vector and the third basis to obtain a second channel matrix; the third basis is composed of K position indices in the second basis selection vector corresponding to columns in the first basis.

[0021] In this method, the second device can determine the projection of the channel matrix based on the corresponding columns of the K position indices on the first basis. The channel matrix can be restored by combining the projection of the channel matrix with the short-cycle coefficient, which is conducive to reducing computational overhead.

[0022] In one possible implementation, the second device receives indication information of the first non-common subspace, where the indication information of the first non-common subspace indicates the projection coefficients of the first non-common subspace on the quantization basis of the first non-common subspace and the column index of the quantization basis of the first non-common subspace. The second device performs Schmidt orthogonalization on the first basis and the first non-common subspace to obtain a fifth basis, and sends indication information of the fifth basis. The indication information of the fifth basis indicates the fifth basis, or indicates the projection coefficients of the fifth basis on the quantization basis of the fifth basis and the column index of the quantization basis of the fifth basis.

[0023] In this method, after the first device determines the non-common subspace of the projection of the historical channel matrix and the projection of the current channel matrix, it can indicate the non-common subspace (i.e., the first non-common subspace) to the second device. The specific indication method includes only indicating the projection coefficients of the first non-common subspace and the column index of the quantization basis, which is conducive to reducing feedback overhead. In addition, after the second device determines the first non-common subspace, it can also update the first basis based on the first non-common subspace to obtain the fifth basis. The fifth basis can be used to quantize the channel matrix subsequently, which is conducive to improving the accuracy of recovering channel state information. Optionally, the second device can also send indication information of the fifth basis to the core network device, which is conducive to the core network device updating the basis information and updating the channel spectrum.

[0024] In a possible implementation, the second device sends first indication information, where the first indication information indicates a frequency domain location for sending the third reference signal. The second device receives the third reference signal.

[0025] In this method, the second device may further send first indication information to instruct the first device to send a third reference signal, so that the channel state information can be restored based on the third reference signal.

[0026] In one possible implementation, the second device determines a fourth channel matrix based on a third reference signal, and determines a third superposition coefficient vector based on a sixth basis constructed by position indexes of the fourth channel matrix and the third reference signal in the spatial-frequency domain in corresponding rows of the first basis. The second device determines that the F superposition coefficients with the largest amplitudes in the third superposition coefficient vector constitute a fourth superposition coefficient vector, and determines that the position indexes of the F superposition coefficients in the third superposition coefficient vector constitute a fourth basis selection vector. The second device multiplies the fourth superposition coefficient vector by a seventh basis to obtain a fifth channel matrix, where the seventh basis is formed by the K position indexes in the fourth basis selection vector in corresponding columns of the fifth basis.

[0027] In this method, the second device may perform channel estimation and recovery of channel state information based on an uplink reference signal (eg, SRS).

[0028] In one possible implementation, the second device sends a first request message to the core network device, where the first request message requests to obtain a channel map, or requests to obtain the basis information corresponding to the first device in the channel map. The second device receives a first response message, where the first response message includes the channel map, or the basis information corresponding to the first device in the channel map. In this method, the second device can request to obtain the channel map from the core network device, thereby obtaining basis information (such as the first basis) based on the channel map, and can send the basis information as prior information to the first device, which is beneficial to reducing the overhead of the reference signal.

[0029] In one possible implementation, a second device sends a first request message to a core network device, requesting access to a channel map or a channel covariance matrix corresponding to the first device in the channel map. The second device receives a first response message, including the channel map or the channel covariance matrix corresponding to the first device in the channel map.

[0030] In this method, the second device can request the core network equipment to obtain the channel spectrum, thereby obtaining the channel covariance matrix corresponding to the first device based on the channel spectrum, and can send the channel covariance matrix to the first device as prior information, which is conducive to reducing the overhead of the reference signal.

[0031] In one possible implementation, the second apparatus performs channel estimation based on the fourth reference signal to obtain multiple sixth channel matrices, where the multiple sixth channel matrices include channel state information in the spatial-frequency domain. The fourth reference signal is a reference signal received before the third reference signal, and the fourth reference signal and the third reference signal are of the same type. The second apparatus determines an eighth basis based on the multiple sixth channel matrices.

[0032] In one possible implementation, the second device determines a common subspace where the eighth basis intersects the first basis as a second common subspace, and determines a subspace in the eighth basis excluding the second common subspace as a second non-common subspace, and the second non-common subspace is used to update the fifth basis.

[0033] In the above method, the second device can generate a corresponding eighth basis based on the information of the historical SRS signal, thereby obtaining the difference information between the first basis and the information of the historical SRS signal (such as the second non-common subspace), thereby updating the channel basis, which is conducive to improving the reconstruction accuracy of the channel state information.

[0034] In one possible implementation, the second device performs Schmidt orthogonalization on the fifth basis and the second non-common subspace to obtain a ninth basis. The second device determines a fifth superposition coefficient vector based on the fourth channel matrix and the row corresponding to the space-frequency position of the SRS signal on the ninth basis, and determines a sixth superposition coefficient vector and a sixth basis selection vector based on the fifth superposition coefficient vector. The second device multiplies the sixth superposition coefficient vector by the tenth basis to obtain a sixth channel matrix, thereby reconstructing the channel state information.

[0035] In a third aspect, the present application provides a communication method implemented by interaction between a first device and a second device. For example, the first device may be a terminal, and the second device may be a network device. The communication method includes the following steps: the second device sends indication information of a first basis, the indication information of the first basis indicating the projection coefficients of the first basis on a quantization basis of the first basis and the column index of the quantization basis of the first basis; and the first device receives the indication information of the first basis in response. The second device sends a first reference signal, and the first device receives the first reference signal in response, and determines a first channel matrix based on the first reference signal. Furthermore, the first device may determine a first superposition coefficient vector based on a second basis constructed by indexing the positions of the first channel matrix and the first reference signal in the spatial-frequency domain in corresponding rows of the first basis. The first device selects K superposition coefficient vectors with the largest amplitudes from the first superposition coefficient vector to form a second superposition coefficient vector, and determines the position indexes of the K superposition coefficient vectors in the first superposition coefficient vector to form a second basis selection vector. The first device may send the second superposition coefficient vector and the second basis selection vector; and the second device receives the second superposition coefficient vector and the second basis selection vector in response.

[0036] In another communication method, a second device transmits indication information of a first basis. The indication information of the first basis indicates the projection coefficients of the channel covariance matrix on the quantized basis and the corresponding indices of the projection coefficients on the quantized basis. The projection coefficients and indices of the channel covariance matrix are used by a receiving end to recover the channel covariance matrix and determine the first basis. Accordingly, the first device receives the indication information. The second device transmits a first reference signal. Accordingly, the first device receives the first reference signal and determines the first channel matrix based on the first reference signal. Furthermore, the first device may determine a first superposition coefficient vector based on a second basis constructed by indexing the positions of the first channel matrix and the first reference signal in the spatial-frequency domain in corresponding rows of the first basis. The first device selects K superposition coefficient vectors with the largest amplitudes from the first superposition coefficient vector to form a second superposition coefficient vector, and determines the position indices of the K superposition coefficient vectors in the first superposition coefficient vector to form a second basis selection vector. The first device may transmit the second superposition coefficient vector and the second basis selection vector; accordingly, the second device receives the second superposition coefficient vector and the second basis selection vector.

[0037] In this method, the first device can receive the indication information of the first basis and the first reference signal, and the first reference signal can be a sparse reference signal, which is beneficial to reducing the reference signal overhead. Moreover, based on the indication information of the first basis, the first device can determine the position index of the first reference signal in the space-frequency domain corresponding to the row of the first basis, so that the first device can calculate the short-period coefficient (such as the second superposition coefficient vector) in combination with the channel estimation result of the sparse reference signal and report it, which is beneficial to reducing the feedback overhead. The amount of data of the second superposition coefficient vector and the second basis selection vector received by the second device is small, indicating that the feedback overhead is low. Further, based on these two types of feedback and the first basis, the second device can restore the channel state information.

[0038] Optionally, other implementations of the communication method may refer to the corresponding descriptions in the first aspect and the second aspect, and will not be repeated here.

[0039] In a fourth aspect, the present application provides a communication device. The communication device may be a terminal, or a component of a terminal (such as a processor, chip, or chip system), or a device that can be used in conjunction with a terminal. In one possible implementation, the communication device may include a functional module, which may be a hardware circuit, software, or a combination of hardware circuit and software.

[0040] In one possible embodiment, the communication device includes a communication unit and a processing unit. The communication unit is configured to receive indication information of a first basis, the indication information of the first basis indicating projection coefficients of the first basis on a quantization basis of the first basis and a column index of the quantization basis of the first basis. The processing unit is configured to determine and record the first basis. The communication unit is further configured to receive a first reference signal and to determine a first channel matrix based on the first reference signal. The processing unit is further configured to determine a first superposition coefficient vector based on a second basis constructed by position indexes of the first channel matrix and the first reference signal in the spatial-frequency domain in corresponding rows of the first basis. The processing unit is further configured to select K superposition coefficient vectors with the largest amplitudes from the first superposition coefficient vector to form a second superposition coefficient vector, and to determine the position indexes of the K superposition coefficient vectors in the first superposition coefficient vector to form a second basis selection vector. The communication unit is further configured to transmit the second superposition coefficient vector and the second basis selection vector.

[0041] In a possible implementation, the processing unit is configured to multiply the second superposition coefficient vector and a third basis to obtain a second channel matrix; the third basis is formed by corresponding columns of K position indices in the second basis selection vector in the first basis.

[0042] In one possible implementation, the processing unit is configured to perform channel estimation based on a second reference signal to obtain a third channel matrix, wherein the second reference signal is a reference signal received before the first reference signal, and the second reference signal and the first reference signal are reference signals of the same type. The processing unit is configured to determine a fourth basis based on the third channel matrix, and to determine that a common subspace where the fourth basis intersects with the first basis is the first common subspace, and to determine that a subspace in the fourth basis excluding the first common subspace is the first non-common subspace. The communication unit is configured to send indication information of the first non-common subspace, wherein the indication information of the first non-common subspace indicates the projection coefficients of the first non-common subspace on the quantization basis of the first non-common subspace and the column index of the quantization basis of the first non-common subspace; the first non-common subspace is composed of L1 column basis vectors, where L1 is a positive integer.

[0043] In one possible implementation, the communication unit is configured to receive first indication information indicating a frequency domain location for sending a third reference signal, and the processing unit is configured to send the third reference signal through the communication unit based on the first indication information.

[0044] In a fifth aspect, the present application provides a communication device. The communication device may be a network device, or a component of a network device (such as a processor, chip, or chip system), or a device that can be used in conjunction with a network device. In one possible implementation, the communication device may include a functional module, which may be a hardware circuit, software, or a combination of hardware circuit and software.

[0045] In one possible embodiment, the communication device includes a communication unit and a processing unit. The communication unit is configured to send indication information of a first basis, where the indication information of the first basis indicates the projection coefficients of the first basis on a quantization basis of the first basis and the column index of the quantization basis of the first basis. The communication unit is further configured to send a first reference signal, so that a receiving end of the first reference signal can perform channel estimation based on the first reference signal to obtain a first channel matrix, and the receiving end of the first reference signal can determine a first superposition coefficient vector based on a second basis constructed by the position index of the first channel matrix and the first reference signal in the space-frequency domain corresponding to the row of the first basis, thereby determining to select the K superposition coefficient vectors with the largest amplitudes in the first superposition coefficient vector to form a second superposition coefficient vector, and the position indexes of the K superposition coefficient vectors in the first superposition coefficient vector to form a second basis selection vector. The communication unit is further configured to receive the second superposition coefficient vector and the second basis selection vector.

[0046] In a possible implementation, the processing unit is configured to multiply the second superposition coefficient vector and a third basis to obtain a second channel matrix; the third basis is formed by corresponding columns of K position indices in the second basis selection vector in the first basis.

[0047] In one possible implementation, the communication unit is configured to receive indication information of a first non-common subspace, where the indication information of the first non-common subspace indicates projection coefficients of the first non-common subspace on a quantized basis of the first non-common subspace and a column index of the quantized basis of the first non-common subspace. The processing unit is configured to perform Schmidt orthogonalization on the first basis and the first non-common subspace to obtain a fifth basis, and the communication unit is configured to send indication information of the fifth basis. The indication information of the fifth basis indicates the fifth basis, or indicates projection coefficients of the fifth basis on a quantized basis of the fifth basis and a column index of the quantized basis of the fifth basis.

[0048] In a possible implementation, the communication unit is configured to send first indication information, where the first indication information indicates a frequency domain location for sending the third reference signal. The communication unit is further configured to receive the third reference signal.

[0049] In one possible implementation, the processing unit is configured to determine a fourth channel matrix based on a third reference signal, and to determine a third superposition coefficient vector based on a sixth basis constructed by position indexes of the fourth channel matrix and the third reference signal in the spatial-frequency domain in corresponding rows of the first basis. The processing unit is further configured to determine that the F superposition coefficients with the largest amplitudes in the third superposition coefficient vector constitute a fourth superposition coefficient vector, and to determine that the position indexes of the F superposition coefficients in the third superposition coefficient vector constitute a fourth basis selection vector. The processing unit is further configured to multiply the fourth superposition coefficient vector by a seventh basis to obtain a fifth channel matrix, where the seventh basis is formed by corresponding columns of the fifth basis indices of the K position indexes in the fourth basis selection vector.

[0050] In one possible implementation, a communication unit is configured to send a first request message to a core network device, the first request message requesting access to a channel map or requesting access to baseline information corresponding to a first device in the channel map. The communication unit is further configured to receive a first response message, the first response message including the channel map or the baseline information corresponding to the first device in the channel map.

[0051] In one possible implementation, the processing unit is configured to perform channel estimation based on the fourth reference signal to obtain multiple sixth channel matrices, where the multiple sixth channel matrices include channel state information in a spatial dimension; the fourth reference signal is a reference signal received before the third reference signal, and the fourth reference signal and the third reference signal are of the same type. The processing unit is configured to determine an eighth basis based on the multiple sixth channel matrices.

[0052] In one possible implementation, the processing unit is configured to determine a common subspace where the eighth basis intersects the first basis as a second common subspace, and to determine a subspace in the eighth basis excluding the second common subspace as a second non-common subspace, where the second non-common subspace is used to update the fifth basis.

[0053] In one possible implementation, the processing unit is configured to perform Schmidt orthogonalization on the fifth basis and the second non-common subspace to obtain a ninth basis. The processing unit is configured to determine a fifth superposition coefficient vector based on the fourth channel matrix and the row corresponding to the space-frequency position of the SRS signal in the ninth basis, and to determine a sixth superposition coefficient vector and a sixth basis selection vector based on the fifth superposition coefficient vector. The processing unit is configured to multiply the sixth superposition coefficient vector by the tenth basis to obtain a sixth channel matrix, thereby reconstructing the channel state information.

[0054] For the fourth and fifth aspects, as an example, the processing unit may be a processor, and the communication unit may be a transceiver unit, a transceiver, or a communication interface. It is understood that when the communication device is a communication device (such as a terminal or a network device), the communication unit may be a transceiver in the communication device (for example, a transceiver includes a transmitter and a receiver), for example, implemented by an antenna, a feeder, and a codec in the communication device, or, if the communication device is a chip provided in the device, the processing unit may be a processing circuit, a logic circuit, etc. of the chip, and the communication unit may be an input / output interface of the chip, such as an input / output circuit, a pin, etc.

[0055] In a sixth aspect, the present application provides a communication device, comprising: a processor configured to execute instructions; optionally, the communication device further comprising a memory configured to store the instructions, wherein when the instructions are executed by the processor, the communication device implements at least one of the following: the method according to the first aspect and any possible implementation of the first aspect, and the method according to the second aspect and any possible implementation of the second aspect. Optionally, the processor and the memory are coupled.

[0056] In the seventh aspect, the present application provides a communication system, which includes at least one device or equipment among the above-mentioned aspects from the fourth to the sixth, so that the above-mentioned at least one device or equipment performs at least one of the following: the method in the first aspect and any possible implementation of the first aspect, the method in the second aspect and any possible implementation of the second aspect.

[0057] In an eighth aspect, the present application provides a computer-readable storage medium storing instructions, which, when executed on a computer, causes the computer to execute at least one of the following: the method in the first aspect and any possible implementation of the first aspect, the method in the second aspect and any possible implementation of the second aspect.

[0058] In a ninth aspect, the present application provides a computer program product comprising instructions, which, when executed on a computer, cause the computer to execute at least one of the following: the method of the first aspect and any possible implementation of the first aspect, the method of the second aspect and any possible implementation of the second aspect.

[0059] In a tenth aspect, the present application provides a chip comprising a processor (or a logic circuit). Optionally, the chip may further comprise a communication interface (or interface) for implementing at least one of the following: the method in the first aspect and any possible implementation of the first aspect, the method in the second aspect and any possible implementation of the second aspect. In one possible implementation, if the chip is the smallest processing unit in the entire machine, the chip may be a processor, or may comprise a processor and a memory, or may comprise a processor, a memory, and a transceiver, for implementing at least one of the following: the method in the first aspect and any possible implementation of the first aspect, the method in the second aspect and any possible implementation of the second aspect.

[0060] In an eleventh aspect, the present application provides a chip system. The chip system includes a processor and an interface. Optionally, the chip system may also include a memory for implementing at least one of the following: the method in the first aspect and any possible implementation of the first aspect, and the method in the second aspect and any possible implementation of the second aspect. The chip system may be composed of a chip or may include a chip and other discrete components. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] FIG1 is a schematic diagram of a communication system provided by the present application;

[0062] FIG2 is a schematic diagram of a network element structure provided by the present application;

[0063] FIG3 is a schematic diagram of a channel map;

[0064] FIG4 is a schematic diagram of a process of performing CSI measurement by a network device and a terminal;

[0065] FIG5 is a schematic diagram of an R16 codebook structure;

[0066] FIG6 is a schematic diagram showing an equivalent representation of a channel matrix H using column vectors;

[0067] FIG7 is a schematic diagram of a matrix decomposition of a space-frequency joint channel h;

[0068] FIG8 is a schematic diagram of a space-frequency joint long-short cycle combined with codebook feedback process;

[0069] FIG9 is a flow chart of a communication method provided by the present application;

[0070] FIG10 is a schematic diagram of a channel spectrum combined with a CSI-RS enabled downlink channel reconstruction process provided by the present application;

[0071] FIG11 is a schematic diagram of a channel map combined with CSI-RS to enable downlink channel reconstruction and channel basis update process provided by the present application;

[0072] FIG12 is a schematic diagram of a channel spectrum combined with CSI-RS and SRS to enable downlink channel reconstruction process provided by the present application;

[0073] FIG13 is a schematic diagram of a channel spectrum provided by the present application in combination with CSI-RS and SRS to enable downlink channel reconstruction and a channel basis update process;

[0074] FIG14 is a schematic diagram of a channel map combined with SRS-enabled channel reconstruction and channel basis update process provided by the present application;

[0075] FIG15 is a schematic diagram of a communication device provided by the present application;

[0076] FIG16 is a schematic diagram of another communication device provided in this application. DETAILED DESCRIPTION

[0077] The communication method provided herein can be applied to a communication system 1000 as shown in FIG1 . For example, the communication system includes a radio access network (RAN) 100, wherein the RAN 100 includes at least one RAN node (such as 110a and 110b in FIG1 , collectively referred to as 110), and may also include at least one terminal (such as 120a-120j in FIG1 , collectively referred to as 120). The RAN 100 may also include other RAN nodes, such as wireless relay devices and / or wireless backhaul devices (not shown in FIG1 ). The terminal 120 is wirelessly connected to the RAN node 110. Terminals and RAN nodes may be connected to each other via wired or wireless connections. The communication system 1000 may also include a core network 200. The RAN node 110 is wirelessly or wiredly connected to the core network 200. The core network devices in the core network 200 and the RAN node 110 in the RAN 100 may be independent and distinct physical devices, or they may be a single physical device that integrates the logical functions of the core network devices and the logical functions of the RAN nodes. The communication system 1000 may also include the Internet 300 .

[0078] RAN 100 may be an evolved universal terrestrial radio access (E-UTRA) system, a new radio (NR) system, or a future radio access system defined in 3GPP. RAN 100 may also include two or more of the aforementioned different radio access systems. RAN 100 may also be an open RAN (O-RAN).

[0079] A RAN node, also known as a radio access network device, RAN entity, or access node, facilitates wireless access to a communication system by a terminal. In one application scenario, a RAN node can be a base station, an evolved NodeB (eNodeB), a transmission reception point (TRP), a next-generation NodeB (gNB) in a fifth-generation (5G) mobile communication system, a next-generation base station in a sixth-generation (6G) mobile communication system, or a base station in a future mobile communication system. A RAN node can be a macro base station (such as 110a in Figure 1), a micro base station, an indoor station (such as 110b in Figure 1), a relay node, or a donor node.

[0080] In another application scenario, multiple RAN nodes can collaborate to help terminals achieve wireless access, with different RAN nodes implementing portions of the base station's functions. For example, a RAN node can be a centralized unit (CU), a distributed unit (DU), or a radio unit (RU). The CU implements the base station's radio resource control protocol and packet data convergence protocol (PDCP) functions, as well as the service data adaptation protocol (SDAP) functions. The DU implements the base station's radio link control layer and medium access control (MAC) layer functions, as well as some or all of the physical layer functions. For detailed descriptions of each of the above protocol layers, please refer to the relevant 3GPP technical specifications. The RU can be used to implement the transmission and reception of radio frequency signals. The CU and DU can be two independent RAN nodes, or they can be integrated into the same RAN node, such as in a baseband unit (BBU). The RU can be included in radio frequency equipment, such as a remote radio unit (RRU) or an active antenna unit (AAU). The CU can be further divided into two types of RAN nodes: CU-control plane and CU-user plane.

[0081] In different systems, RAN nodes may have different names. For example, in an O-RAN system, a CU may be called an open CU (O-CU), a DU may be called an open DU (O-DU), and a RU may be called an open RU (O-RU). The RAN node in the embodiments of the present application may be implemented by a software module, a hardware module, or a combination of a software module and a hardware module. For example, the RAN node may be a server loaded with the corresponding software module. The embodiments of the present application do not limit the specific technology and specific device form adopted by the RAN node. For ease of description, the following description takes a base station as an example of a RAN node.

[0082] A terminal is a device with wireless transceiver capabilities that can send signals to a base station or receive signals from a base station. A terminal may also be referred to as a terminal device, user equipment (UE), mobile station, mobile terminal, etc. Terminals can be widely used in various scenarios, such as device-to-device (D2D), vehicle-to-everything (V2X) communication, machine-type communication (MTC), Internet of Things (IoT), virtual reality, augmented reality, industrial control, autonomous driving, telemedicine, smart grid, smart furniture, smart office, smart wearable, smart transportation, smart city, etc. A terminal can be a mobile phone, tablet computer, computer with wireless transceiver capabilities, wearable device, vehicle, airplane, ship, robot, robotic arm, smart home device, etc. The embodiments of this application do not limit the specific technology and specific device form adopted by the terminal.

[0083] Base stations and terminals can be fixed or mobile. They can be deployed on land, indoors or outdoors, handheld or vehicle-mounted; on water; or on aircraft, balloons, and satellites. The embodiments of this application do not limit the application scenarios of base stations and terminals.

[0084] The roles of base stations and terminals can be relative. For example, the helicopter or drone 120i in Figure 1 can be configured as a mobile base station. To terminals 120j accessing the wireless access network 100 via 120i, terminal 120i is a base station. However, to base station 110a, 120i is a terminal, meaning that communication between 110a and 120i occurs via a wireless air interface protocol. Of course, communication between 110a and 120i can also occur via a base station-to-base station interface protocol. In this case, 120i is also a base station relative to 110a. Therefore, base stations and terminals can be collectively referred to as communication devices. 110a and 110b in Figure 1 can be referred to as communication devices with base station functionality, while 120a-120j in Figure 1 can be referred to as communication devices with terminal functionality.

[0085] Communication between base stations and terminals, between base stations, and between terminals can be carried out through authorized spectrum, unauthorized spectrum, or both; communication can be carried out through spectrum below 6 gigahertz (GHz), spectrum above 6 GHz, or spectrum below 6 GHz and spectrum above 6 GHz. The embodiments of the present application do not limit the spectrum resources used for wireless communication.

[0086] In the embodiments of the present application, the functions of the base station may also be performed by a module (such as a chip) in the base station, or by a control subsystem that includes the base station functions. The control subsystem that includes the base station functions here may be a control center in the above-mentioned application scenarios such as smart grid, industrial control, smart transportation, and smart city. The functions of the terminal may also be performed by a module (such as a chip or modem) in the terminal, or by a device that includes the terminal functions.

[0087] In this application, a base station sends downlink signals or downlink information to a terminal, and the downlink information is carried on a downlink channel; the terminal sends uplink signals or uplink information to the base station, and the uplink information is carried on an uplink channel. In order to communicate with the base station, the terminal needs to establish a wireless connection in the cell controlled by the base station. The cell with which the terminal has established a wireless connection is called the serving cell of the terminal. When the terminal communicates with the serving cell, it will also be interfered with by signals from neighboring cells.

[0088] The core network may include, but is not limited to, one or more of the following devices or network elements: access and mobility management function (AMF), location management function (LMF), and map management function (MMF). The AMF is primarily responsible for mobility management in mobile networks, such as user location updates, user network registration, and user handovers. The LMF is primarily responsible for obtaining positioning information such as user location. The MMF is primarily responsible for storing channel characteristics based on location information and generating channel maps.

[0089] Optionally, the network element structure involved in this application is shown in Figure 2, which mainly includes the following network elements and modules:

[0090] (1) Radio resource control (RRC) signaling interaction module: The module used by the base station and the terminal to send and receive RRC signaling.

[0091] (2) MAC signaling interaction module: a module used by base stations and terminals to send and receive MAC control element (MAC-CE) signaling.

[0092] (3) Physical layer (PHY) signaling and data interaction module: The module used by the base station and the terminal to send and receive uplink / downlink control signaling (such as physical downlink control channel (PDCCH), physical uplink control channel (PUCCH)), and uplink / downlink data (such as data transmitted on physical downlink shared channel (PDSCH), data transmitted on physical uplink shared channel (PUSCH)).

[0093] (4) The base station and AMF communicate through the NG-C interface. The AMF is equivalent to the router for communication between the base station and LMF / MMF. The LMF realizes the location estimation of the UE. The map construction process is completed in the LMF / MMF. The AMF and LMF / MMF communicate through the NLs interface.

[0094] It can be understood that in this application, PDSCH, PDCCH, PUSCH and PUCCH are only examples of downlink data channels, downlink control channels, uplink data channels and uplink control channels, respectively. In different systems and different scenarios, data channels and control channels may have different names, and this application does not limit this.

[0095] It should be noted that:

[0096] "Sending" and "receiving" in the embodiments of the present application indicate the direction of signal transmission. For example, "sending information to a terminal" can be understood as the destination end of the information being the terminal device, which can include direct sending through the air interface, and also includes indirect sending through the air interface by other units or modules. "Receiving information from a network device" can be understood as the source end of the information being the network device, which can include direct receiving from the network device through the air interface, and also includes indirect receiving from the network device through the air interface from other units or modules. "Sending" can also be understood as the "output" of the chip interface, and "receiving" can also be understood as the "input" of the chip interface.

[0097] In other words, sending and receiving can be performed between devices, for example, between a network device and a terminal device, or can be performed within a device, for example, sending or receiving between components, modules, chips, software modules or hardware modules within the device through a bus, wiring or interface.

[0098] It is understandable that information may be processed between the source and destination of information transmission, such as coding, modulation, etc., but the destination can understand the valid information from the source. Similar expressions in this application can be understood similarly and will not be repeated.

[0099] In the embodiments of the present application, "indication" may include direct indication and indirect indication, and may also include explicit indication and implicit indication. The information indicated by a certain information (such as the indication information described below) is called information to be indicated. In the specific implementation process, there are many ways to indicate the information to be indicated, such as but not limited to, the information to be indicated can be directly indicated, such as the information to be indicated itself or the index of the information to be indicated. The information to be indicated can also be indirectly indicated by indicating other information, wherein there is an association between the other information and the information to be indicated; it is also possible to indicate only a part of the information to be indicated, while the other parts of the information to be indicated are known or agreed in advance, for example, the indication of specific information can be achieved with the help of the arrangement order of each information agreed in advance (such as predefined by the protocol), thereby reducing the indication overhead to a certain extent. The present application does not limit the specific method of indication. It is understandable that, for the sender of the indication information, the indication information can be used to indicate the information to be indicated, and for the receiver of the indication information, the indication information can be used to determine the information to be indicated.

[0100] For ease of understanding, the following is a detailed introduction to the definitions of relevant terms involved in this application:

[0101] 1. Channel map:

[0102] A channel map can be understood as a database that stores location-based channel characteristics, including but not limited to the channel statistical covariance matrix, angular spectrum, delay spectrum, and path loss. For example, Figure 3 shows a schematic diagram of a channel map. In this channel map, the physical cell is divided into two-dimensional grid points (each square in Figure 3 is a grid point). Each grid point stores a number of channel characteristics (such as the channel statistical covariance matrix, angular spectrum, delay spectrum, and path loss) in the form of a matrix, vector, or scalar.

[0103] Among them, the commonly used channel map construction method is to build a database based on historical measurement data and establish a mapping relationship between location information and channel characteristics. However, historical measurement data has limitations. For example, historical measurement data is usually based on channel characteristics at known locations, and the channel characteristics at unknown locations are supplemented by interpolation methods to obtain the channel map of the entire cell. With the development of digital twin technology, channel maps can be obtained through channel twin technology. For example, a computer can combine a priori environmental maps (such as environmental information obtained by measurement) and use electromagnetic simulation calculations to simulate the reflection, diffraction, and scattering characteristics of communication multipaths, thereby obtaining deterministic channels for constructing channel maps.

[0104] 2. Channel map-assisted communication technology:

[0105] With the increase in system bandwidth, the increase in terminal antennas, the increase in network load, the surge in wireless channel dimensions (for example, the wireless channel dimensions can be expanded to multiple dimensions such as the spatial domain, spatial frequency domain, and frequency domain), and the limited pilot measurement resources, high-precision measurement of wireless channels faces huge challenges. Accurate measurement of wireless channels is the cornerstone of mobile communication network research and is crucial to the design, analysis, and optimization of wireless communication networks. However, traditional wireless channel measurement methods based on reference signals (such as pilot symbols) are difficult to meet the needs of technological development such as large bandwidth and multiple antennas. In order to solve the problem of limited reference signal measurement resources in wireless communication systems, channel maps can be used to achieve channel measurement with low pilot overhead; for example, the channel covariance matrix of a specific location is provided by the channel map, and the sounding reference signal (SRS) overhead is assisted reduced based on the channel covariance matrix.

[0106] 3. Downlink channel reconstruction technology:

[0107] In 5G communication systems, the use of massive multiple input multiple output (MIMO) technology helps improve the system's spectral efficiency. When using MIMO technology, network devices need to perform signal precoding based on channel state information (CSI) when sending data to terminal devices.

[0108] In a time division duplexing (TDD) system, downlink CSI can be obtained based on channel reciprocity, for example, by estimating the downlink channel by sending uplink SRS data. As the number of users increases and the load continues to increase, SRS transmission in large bandwidth scenarios may lead to insufficient SRS resources and severe channel aging.

[0109] In frequency division duplexing (FDD) systems, due to the large frequency separation between uplink and downlink channels, the uplink and downlink channels do not directly exchange with each other, making it impossible to use uplink channel information for accurate downlink precoding. In FDD systems, users are required to provide downlink channel CSI feedback to the base station.

[0110] For example, FIG4 is a schematic diagram of a process of performing CSI measurement by a network device and a terminal, which may include the following steps:

[0111] Step 1: The network device sends channel measurement configuration information to the terminal. The channel measurement configuration information is used to configure the channel measurement, for example, to indicate the channel measurement time to the terminal.

[0112] Step 2: The network device sends a channel state information reference signal (CSI-RS) to the terminal. This pilot is used for channel measurement. For example, the terminal receives the CSI-RS and performs measurements based on the CSI-RS to obtain CSI feedback information. Optionally, the CSI-RS can also be called a CSI-RS pilot.

[0113] Step 3: The terminal sends channel state information to the network device. For example, the terminal sends channel state information such as channel rank indicator (RI), channel quality indicator (CQI), and precoding matrix indicator (PMI) to the network device.

[0114] Step 4: The network device sends data to the terminal based on the CSI. The network device determines the precoding information for the service data based on the CSI fed back by the terminal, thereby transmitting the service data.

[0115] Optionally, channel state information (CSI) includes information used to describe the channel properties of the communication link reported by the receiving device to the transmitting device in a wireless communication system. CSI may include, but is not limited to, precoding matrix indication (PMI), rank indication (RI), channel quality indication (CQI), CSI-RS resource indicator (CSI-RS resource indicator, CRI) and layer indicator (layer indicator, LI), etc. It should be understood that the specific content of the CSI listed above is only an example and should not constitute any limitation to this application. CSI may include one or more of the items listed above, and may also include other information used to characterize CSI in addition to the above-mentioned items, which is not limited in this application.

[0116] 4. R16 codebook solution for channel reconstruction based on reference signals:

[0117] For example, the R16 codebook is a dual-domain compression codebook in the spatial domain and the frequency domain. It compresses the channels of all subbands in the frequency domain. The codebook structure satisfies formula (1):

[0118] in, is the spatial compression matrix, is the combination coefficient matrix, is the frequency domain compression matrix, N1 and N2 are the number of horizontal and vertical antenna ports of the base station, L is the number of spatial basis, and M is the number of frequency domain basis. For example, Figure 5 is a schematic diagram of an R16 codebook structure, which shows each matrix and its dimensions. Optionally, spatial-frequency dual-domain compression refers to quantizing the channel using both spatial and frequency sparsity to reduce the number of weighting coefficients required to be reported, thereby achieving channel matrix compression.

[0119] However, the R16 codebook only utilizes the sparse characteristics of the channel in the angle-delay domain, that is, the spatial information correlation characteristics on different subbands for feedback and compression. For example, it is necessary to feedback the spatial domain, frequency domain basis and combination coefficients, which results in a large feedback overhead. And because the basis needs to be reported, the protocol stipulates that both the spatial domain and frequency domain basis are discrete Fourier transform (DFT) codebooks, which limits the sparsity of the combination coefficient matrix W2. In addition, in actual channels, especially in scenarios where the channel propagation environment changes slowly, the basis changes very slowly and can be fed back over a long period. However, R16 does not support reporting the basis and combination coefficients at different periods.

[0120] 5. R18 codebook solution for channel reconstruction based on reference signals:

[0121] To achieve a sparse representation of the channel in the space-frequency domain, fully exploit the channel's sparse characteristics, and consider the inconsistent temporal variations of different channel characteristics. For example, the path angle-delay information (joint space-frequency basis) changes slowly, while the path superposition coefficient (the superposition coefficient corresponding to the basis) changes rapidly. The R18 codebook scheme for channel reconstruction based on a reference signal is designed with a combined long- and short-cycle codebook feedback method, which helps reduce feedback overhead. For example, the following describes two scenarios: joint space-frequency compression and feedback, and independent space-frequency compression and feedback.

[0122] Case 1: Joint space-frequency compression and feedback:

[0123] Taking the downlink channel as an example, assuming that the terminal has a single antenna, the channel matrix of the terminal satisfies formula (2):

[0124] in, is the spatial compression matrix, is the frequency domain compression matrix, is a combination coefficient matrix (which is a diagonal matrix), M is the number of base station antennas, L is the number of channel multipaths, and N is the number of frequency units (for example, a frequency unit is a subcarrier or a resource element (RE) or a resource block (RB) or a resource group (RBG) or a sub-band). For example, FIG6 is a schematic diagram of an equivalent representation of a channel matrix H using a column vector. It can be seen that the channels H1, H2, ..., H represented by the matrix in the spatial-frequency domain shown in FIG6 t The column vectors h1, h2, ..., h in the space frequency domain can be used t Equivalent representation. The equivalent column vector satisfies formula (3):

[0125] Where diag(C) represents the column vector consisting of the diagonal elements of matrix C ⊙ represents the Khatri-Rao product. For example, a l is the lth column of A, is the Kronecker product, b l is the lth column of B, where l is an integer greater than 0. * The lth (i=1, ..., N) column of ⊙S can satisfy formula (4):

[0126] in, represents the Kronecker product, where [:,l] represents the lth column of the matrix. The above operation can represent the channel represented by a matrix in the space-frequency domain using a space-frequency column vector.

[0127] Among them, for the channel h represented by the column vector, its statistical covariance matrix satisfies formula (5):

[0128] in, Indicates the expectation of random numbers / matrices, U is the covariance matrix R h The matrix of the eigenvectors of U, the i-th column is R h The i-th eigenvector of , whose corresponding eigenvalue is the i-th element on the diagonal of the diagonal matrix Λ, the eigenvalue corresponding to each column of U is the element on the diagonal of the diagonal matrix Λ, and the elements on the diagonal of Λ are arranged from large to small. The average covariance matrix between polarizations satisfies formula (6):

[0129] Among them, h + is the channel corresponding to positive polarization, h - is the channel corresponding to negative polarization, is the mean covariance matrix The matrix of eigenvectors, The i-th column of The i-th eigenvector of The i-th element on the diagonal of The eigenvalue corresponding to each column is a diagonal matrix The elements on the diagonal of , and The elements on the diagonal are arranged from large to small, then the instantaneous channel satisfies formula (7):

[0130] Among them, U p is the matrix composed of the first P columns of the basis U. The channel has a sparse characteristic in the angular delay domain (i.e. Only some elements in the θ are non-zero or have large values), and the angular delay changes slowly (i.e. at different times h1, h2…h t ,U can be considered to be basically unchanged or change slowly, and Then it changes with time). In addition, using KL decomposition (Karhunen-Loeve decomposition), when based on the matrix R h The eigenvectors corresponding to the P largest eigenvalues ​​(i.e. the first P columns of U p ) is used to expand h, the truncated statistical mean square error is the smallest. Considering that the statistical covariance matrix can be approximated by the statistical covariance matrix after polarization averaging, the instantaneous channel h satisfies formula (8):

[0131] in, for Before The matrix consists of columns, In designing a CSI feedback solution, a longer period can be used to Provide quantitative feedback in a short-term or non-periodic manner Provide quantitative feedback.

[0132] For example, a specific CSI compression reporting solution includes the following steps:

[0133] S1: UE performs space-frequency joint covariance matrix statistics on the downlink channel and performs inter-polarization averaging to obtain right Perform singular value decomposition (SVD) or eigendecomposition to obtain the matrix of eigenvectors UE pair matrix Truncate and select the one with the largest energy The corresponding eigenvalues Column matrix Contains most of the channel energy (the choice of P can be determined by the UE, or the gNB specifies an optional range and then the UE selects it).

[0134] S2: UE uses the DFT codebook to construct a matrix of statistical eigenvectors Make an approximation, that is, find W f , W s , C1 makes or Where W f With W s is a submatrix composed of some columns of the oversampled DFT matrix, representing the beam / basis vectors in the frequency domain and spatial domain respectively; C1 is The projection on the quantization matrix W1 can correct W1 into a statistical feature matrix The W calculated in this step f , W s , C1 is reported to the base station with a long period (optional, "long period" is to distinguish it from the "short period" in the following text, and it does not necessarily emphasize that the reporting period of these matrices is the same, because the time change scale of each matrix may be different, for example, the rate of change of C1 over time is more likely to be higher than W f , W s faster, and thus can have a different granularity of feedback cycles).

[0135] S3: The UE calculates the codebook C2 to be fed back based on the instantaneous channel h and W1C1 obtained in S2. C2 can be the projection of the instantaneous channel h on W1C1, that is, C2 = (W1C1) H h; or C2 can be calculated in other ways (for example, when the columns of W1C1 are not orthogonal, W1C1 needs to be orthogonalized). The UE feeds back C2 to the base station in a short period or aperiodically for reconstructing the downlink channel.

[0136] The above CSI compression reporting scheme is mapped to the codebook form to satisfy formula (9):

[0137] Where ⊙ represents the KR (Khatri-Rao) product. For example, Figure 7 shows a matrix decomposition diagram of a space-frequency joint channel h, where h is the space-frequency joint channel, M is the number of base station antennas (dual-polarization array), and N is the number of frequency units (subcarrier granularity or RB granularity or RBG granularity or subband granularity). Since W f , W s , C1 is used to quantify the approximation Therefore, 2K≥P is satisfied, and K is the matrix W s The number of columns. is the DFT basis for quantizing the joint space-frequency basis.

[0138] Case 2: Space-frequency independent compression and feedback:

[0139] Taking the downlink channel as an example, assuming that the terminal has a single antenna, the channel matrix of the terminal satisfies formula (10): H≈S′C1C2C3F′ H (10)

[0140] in, is the spatial basis, which is a matrix composed of B spatial vectors; is the frequency domain basis, which is a matrix composed of F frequency domain vectors. is the first superposition coefficient matrix, which represents the coefficient matrix composed of multiple groups of spatial vector coefficients; is a second superposition coefficient matrix, representing a coefficient matrix composed of weighting coefficients corresponding to a set of space-frequency vectors composed of each space-domain vector in the B space-domain vectors and each frequency-domain vector in the F frequency-domain vectors; is the third superposition coefficient matrix, which represents a matrix composed of multiple sets of frequency domain vector coefficients. B is the number of spatial domain vectors determined by the network device or terminal; K s represents the number of weighted coefficients corresponding to each spatial domain vector; D represents the number of weighted coefficients corresponding to each frequency domain vector; and F is the number of frequency domain vectors determined by the network device or terminal.

[0141] Optionally, the spatial domain vector may also be called a beam vector, a spatial beam basis vector, or a spatial basis vector. The length of the spatial domain vector may be the number M of transmit antenna ports in a polarization direction, where M is a positive integer greater than 1. For example, if the spatial domain vector is a column vector or a row vector of length M, then the M column vectors or row vectors correspond to M transmit antenna ports, respectively, and this application does not limit this. Each element in the spatial domain vector may represent the weight of each antenna port. Based on the weights of each antenna port represented by each element in the spatial domain vector, the signals of each antenna port are linearly superimposed to form an area with a strong signal in a certain direction or certain directions in space. Optionally, the spatial domain vector may be determined based on a DFT vector. In other words, the spatial domain vector may be a DFT vector. The spatial domain vector may, for example, be a DFT vector defined in the type II codebook in the 3GPP technical specification TS 38.214 version 15 (release 15, R15).

[0142] Optionally, a frequency domain vector (frequency domain vector), also known as a frequency domain basis vector, is a vector used to represent the variation pattern of the channel in the frequency domain. A frequency domain vector can represent a variation pattern. Since a signal can reach the receiving antenna from the transmitting antenna through multiple paths when transmitted through a wireless channel. Multipath delay causes frequency selective fading, which is a change in the frequency domain channel. Therefore, different frequency domain vectors can be used to represent the variation pattern of the channel in the frequency domain caused by delays on different transmission paths. The length of the frequency domain vector can be determined by the number of frequency domain units to be reported configured by the network side in the reporting bandwidth, or it can be a protocol predefined value. This application does not limit the length of the frequency domain vector. Among them, the reporting bandwidth can, for example, refer to the CSI reporting bandwidth (CSI-Reporting Band) carried in the CSI reporting configuration in the high-level signaling (such as RRC message). The length of the frequency domain vector can be denoted as N, where N is a positive integer greater than 1. The frequency domain vector can, for example, be a column vector or row vector whose length includes N. This application does not limit it.

[0143] Optionally, a joint space-frequency basis can represent common characteristics of the spatial and frequency domains; for example, the joint space-frequency basis is a matrix constructed from one or more space-frequency basis vectors. The space-frequency basis vectors can represent the channel's frequency-domain variation pattern and the signal characteristics in one or more spatial directions. For example, the characteristics of space-domain and frequency-domain vectors can be described above and will not be repeated here.

[0144] Corresponding to the channel decomposition method shown in formula (10), the mapping to the codebook form satisfies formula (11):

[0145] in, It is the spatial basis of the downlink channel determined by the network device or terminal. It is the frequency domain basis of the downlink channel determined by the network device or terminal. s The calculation method satisfies formulas (12) and (13): U s =W S C1 (13)

[0146] in, is the spatial statistical covariance matrix of H, R S The matrix composed of the eigenvectors of S The eigenvalue corresponding to each column is a diagonal matrix The elements on the diagonal of , and Λ S The elements on the diagonal are arranged from large to small. Indicates the expectation of random numbers / matrices. W fThe calculation method is to satisfy formulas (14) and (15):

[0147] in, is the frequency domain statistical covariance matrix of H, R F The matrix composed of the eigenvectors of F The eigenvalue corresponding to each column is a diagonal matrix The elements on the diagonal of , and Λ F The elements on the diagonal are arranged from largest to smallest.

[0148] For example, Figure 8 is a schematic diagram of a space-frequency joint long-short cycle combined with codebook feedback process. For example, assuming that the base station configuration includes 64T dual-polarization antennas, 50RB, and uses 64 DFT column vectors to approximate The number of columns is 13, Long-cycle feedback W1C1, period T L ; Short-cycle feedback C2, period is T s During each long-period baseline feedback, ignoring the amount of feedback required for W1, the 64 × 13 = 832 coefficients that make up C1 must be fed back. This indicates that the combined space-frequency, long- and short-period codebook feedback overhead is significant. Furthermore, the base station must be configured with a 32-port CSI-RS for channel information measurement, resulting in significant pilot overhead. This increases dramatically with the number of antennas and frequency bands.

[0149] Therefore, the present application provides a communication method, in which the base station uses the regional channel basis provided by the channel map as prior information (which can be a space-frequency joint basis U, a spatial basis U S , frequency domain basis U F , or it can be the spatial compression matrix W s , frequency domain compression matrix W f , not limited in this application), then the space-frequency joint basis U is sent to the UE over a long period, and the sparse CSI-RS is sent over a short period. After receiving the sparse CSI-RS, the UE calculates the superposition coefficient C2 and feeds it back over a short period. Simultaneously, it updates and feeds back the column index value of the space-frequency joint basis, which helps reduce feedback overhead.

[0150] In order to reduce the overhead of reference signals and reduce the feedback overhead of reference signals, the present application provides a communication method, which effectively reduces the overhead of reference signals and reduces the feedback overhead of reference signals by sending channel basis information based on a channel map, thereby improving the accuracy of channel reconstruction.

[0151] For example, Figure 9 is a flow chart of a communication method provided by this application. The method can be implemented by interaction between a first device and a second device. The first device in this application can be a terminal or a module applied to a terminal, and the second device can be a network device or a module applied to a network device. The method includes the following steps:

[0152] S101, the second device sends indication information of the first base; correspondingly, the first device receives the indication information of the first base.

[0153] For example, according to the above-mentioned scheme of R16 and R18 codebooks for channel reconstruction based on reference signals, the matrix of the terminal's channel can be equivalently represented by a column vector in the space-frequency domain. The terminal determines the channel based on the CSI-RS, and the base station recovers the channel based on the quantization basis and coefficients fed back by the terminal. Therefore, in this embodiment, the second device is designed to directly send indication information of the first basis to the first device (used to indicate the first basis to the first device), so that the first device can directly obtain the basis information. In addition, different from the scheme of R16 and R18 codebooks (the channel basis is calculated on the terminal side and then quantized and fed back to the base station side, so there is a loss of accuracy in the basis calculated on the base station side), in this embodiment, the first basis is the regional channel basis (prior information) provided by the channel map, and the second device can obtain the channel basis without quantization loss based on the channel map, which is beneficial to improving the accuracy of CSI reconstruction.

[0154] In an optional implementation, the indication information of the first basis indicates the projection coefficient of the first basis on the quantization basis of the first basis and the column index of the quantization basis of the first basis; the second device can determine the first basis based on the projection coefficient and column index of the first basis.

[0155] In another optional implementation, the indication information of the first basis indicates the projection coefficients of the channel covariance matrix on the quantization basis and the corresponding indices of the projection coefficients on the quantization basis; the second device can restore the channel covariance matrix based on the projection coefficients and indices of the channel covariance matrix, and then determine the first basis based on the channel covariance matrix.

[0156] The first basis is composed of L columns of basis vectors, where L is a positive integer. For example, the quantization basis of the first basis is any one of a DFT codebook, a fast Fourier transformation (FFT) codebook, an oversampled DFT codebook, an oversampled FFT codebook, or a codebook determined based on a preset rule, and this application is not limited thereto. Wherein, the basis vector is determined based on the quantization basis. For example, the basis vector is any one of a DFT basis vector (a DFT basis vector is a vector determined based on a DFT codebook), an FFT basis vector (an FFT basis vector is a vector determined based on an FFT codebook), an oversampled DFT basis vector (an oversampled DFT basis vector is a vector determined based on an oversampled DFT codebook), an oversampled FFT basis vector (an oversampled FFT basis vector is a vector determined based on an oversampled FFT codebook), or a vector determined based on a preset rule. Assuming that one or more basis vectors are one or more DFT basis vectors, the first basis is a matrix composed of L columns of DFT basis vectors selected from the one or more DFT basis vectors (that is, the elements in the first basis satisfy the preset rules and have relevant characteristics).

[0157] The column index of the quantization basis of the first basis includes the index of the basis vectors constituting the first basis. For example, assuming that the first basis is obtained by quantizing and projecting the quantization basis of the first basis, for example, the quantization basis of the first basis can be a DFT codebook, then the first basis is obtained by quantizing and projecting the DFT codebook. However, the DFT codebook may have multiple DFT basis vectors arranged in sequence. Assuming that the first, third, and fifth DFT basis vectors are selected to construct the first basis, the column index of the quantization basis of the first basis is {1, 3, 5}.

[0158] Optionally, the first basis is a space-frequency joint basis, or a space domain basis and a frequency domain basis. For example, assuming that the first basis is a space-frequency joint basis U, and the quantization basis of the first basis is a DFT codebook, the indication information of the first basis indicates the projection coefficient of the space-frequency joint basis U in the DFT codebook and the column index of the DFT codebook. It should be noted that the basis in this application can also be referred to as a codebook. For example, the first basis can also be referred to as a first codebook, the second basis can also be referred to as a second codebook, and so on. This application is not limited thereto.

[0159] Optionally, specific implementations of the indication information of the first base include the following:

[0160] (1) Case 1: The indication information of the first basis includes the first basis. That is, the second device directly sends the first basis to the first device. For example, assuming that the first basis is the space-frequency joint basis U, the second device uses PDCCH / PDSCH to send the space-frequency joint basis corresponding to the first device to the first device. M is the number of antennas of the second device, L is the number of paths, and N is the number of frequency units (for example, a frequency unit is a subcarrier, RB, RBG, or subband). It should be noted that the values ​​in the first basis can be in complex form. In this case, the complex values ​​need to be subjected to amplitude and phase quantization processing. The second device can obtain and transmit the first basis after the amplitude and phase quantization processing.

[0161] (2) Case 2: The indication information of the first basis includes the projection coefficient of the first basis on the quantization basis of the first basis and the column index of the quantization basis of the first basis. That is, the second device indirectly indicates the first basis to the first device. For example, assuming that the first basis is a space-frequency joint basis U, the second device can use the quantization basis B of the first basis constructed by one or more basis vectors to quantize the space-frequency joint basis U, and the quantization process satisfies formula (16): U = B × C 13 (16)

[0162] Where B represents the quantized basis of the first basis, C 13 Represents the projection coefficient of the first basis on the quantized basis of the first basis, C 13 The role of is similar to the coefficient W1C1 above. Therefore, the indication information of the first basis includes the column index of the quantization basis of the first basis (indicating the basis vector used for quantizing the space-frequency joint basis U) and C 13 For another example, suppose the first basis is the spatial basis U S and frequency domain basis U F When , you can refer to the description of the space-frequency independent compression and feedback process described in the first part of the previous article, such as the spatial basis U S Satisfy formula (13), use W S Perform quantization processing; frequency domain basis U F Satisfy formula (15), use W f Perform quantification processing.

[0163] Optionally, the second device may use PDCCH / PDSCH to send the projection coefficient of the first basis on the quantization basis of the first basis and the column index of the quantization basis of the first basis to the first device; correspondingly, the first device receives the projection coefficient of the first basis on the quantization basis of the first basis and the column index of the quantization basis of the first basis, so that the space-frequency joint basis U can be restored in combination with the quantization basis B of the first basis. Optionally, the quantization basis B of the first basis is known and the same for both the first device and the second device. Optionally, the indication overhead of case 2 is lower than the indication overhead of case 1, but both the first device and the second device need to preset (such as pre-store) the quantization basis B of the first basis.

[0164] (3) Case 3: The indication information of the first basis includes the projection coefficients of the channel covariance matrix on the quantized basis and the indexes (or position indexes) corresponding to the projection coefficients on the quantized basis. That is, the second device indirectly indicates the first basis to the first device. The first device can determine the channel covariance matrix based on the indicated projection coefficients and indexes of the channel covariance matrix, perform singular value decomposition or eigendecomposition on the channel covariance matrix, and obtain the first basis corresponding to the channel covariance matrix.

[0165] For example, the frequency domain statistical covariance matrix R shown in formula (14) F For example, the first device calculates the R by the following formula (17): F Compress the matrix W in the frequency domain f Projection is performed on the projection coefficient matrix S delay :

[0166] The second device can obtain the projection coefficient matrix S delay Select the K' projection coefficients with the largest quantization value to send, and send the K' projection coefficients in the frequency domain compression matrix W f The corresponding row and column index.

[0167] Optionally, for the projection coefficient matrix of the channel covariance matrix on the quantization basis, the second device may only send down the diagonal elements of the projection coefficient matrix. Since the diagonal elements are real numbers (the coefficients are real numbers), the indication overhead can be reduced.

[0168] For example, the projection coefficient matrix S delay The diagonal elements are:

[0169] Among them, S delay The diagonal elements of are real numbers, and the projection coefficients are also real numbers. The second device can send the S delay The first L with the largest median or quantized value delay The projection coefficients and the front L delay The index id corresponding to the projection coefficient on the quantized basis d,part Since the row and column indices of the diagonal elements are equal, the row and / or column indices can be downloaded.

[0170] Optionally, before S101, the following steps are further included:

[0171] The second device sends a first request message to the core network device, requesting a channel map and thereby obtaining the basis information corresponding to the first device. For example, the channel map is shown in Figure 3. When the first device moves to any grid in the channel map, the second device can trigger a first request message to obtain the basis information corresponding to the first device. The basis information is determined based on the channel map. For example, the second device can determine the first basis as a joint space-frequency basis based on the path angle-delay information in the channel map. Optionally, if the core network device is an AMF, the second device sends the first request message to the AMF. The AMF acts as a router for communication between the second device and the LMF / MMF. The second device then requests the channel map from the LMF / MMF via the AMF. Correspondingly, the LMF / MMF can send the channel map to the second device via the AMF. Therefore, after obtaining the channel map, the second device can determine the first basis based on the channel map.

[0172] S102, the second device sends a first reference signal; correspondingly, the first device receives the first reference signal.

[0173] The first reference signal is used to measure channel information, and may be a downlink reference signal, which may include a CSI-RS, a synchronization signal / physical broadcast channel block (SSB), or a demodulation reference signal (DMRS).

[0174] Optionally, the density of the first reference signal is positively correlated with the number of columns of the first basis. Specifically, the density ρ of the first reference signal is proportional to the number of columns L of the first basis. For example, the smaller L is, the smaller ρ is. It can be understood that the smaller the number of columns L of the first basis, the fewer the number of channel multipaths, and the fewer the values ​​required for channel measurement, and correspondingly, the fewer the reference signals required to be sent; therefore, the density ρ of the first reference signal is proportional to the number of columns L of the first basis. For example, assuming that the first basis is a space-frequency joint basis U, it is known that the space-frequency joint basis corresponding to the first device is Among them, M is the number of antennas of the second device, L is the number of channel multipaths, and N is the number of frequency units; the second device sets the density ρ of the first reference signal based on the number of columns L of the space-frequency joint basis U, which can reduce the frequency domain granularity from N to N1, thereby reducing the reference signal overhead.

[0175] S103: The first device determines a first channel matrix based on the first reference signal.

[0176] S104: The first device determines a first superposition coefficient vector based on a second basis constructed by position indexes of the first channel matrix and the first reference signal in the space-frequency domain and corresponding rows of the first basis.

[0177] The first device performs channel estimation based on the first reference signal, and can obtain the first channel matrix as the channel state information of the first reference signal in the corresponding space-frequency domain dimension. For example, assuming that the first reference signal is a CSI-RS signal, the first device performs channel estimation on the CSI-RS signal and obtains the first channel matrix h in the space-frequency domain dimension. s The dimension of the first channel matrix is ​​MN1×1, for example, h s satisfy M is the spatial domain granularity of the first reference signal (such as the number of antennas), and N1 is the frequency domain granularity of the first reference signal (such as the number of subcarriers or the number of RBs or the number of RBGs or the number of subbands, etc.).

[0178] The second basis constructed by the position index of the first reference signal in the space-frequency domain in the corresponding row of the first basis is represented by U s The dimension of the second base is MN1×L, for example, U s satisfy For example, the first device receives the first reference signal and can determine the position index of the first reference signal in the space-frequency domain; based on the position index (M and N1) of the first reference signal in the space-frequency domain, obtain the row corresponding to the position index from the first basis to form the second basis U s .

[0179] The first superposition coefficient vector is determined based on the second basis constructed by the position index of the first channel matrix and the first reference signal in the space-frequency domain in the corresponding row of the first basis, and satisfies formula (19): c=pinv(U s )×h s (19)

[0180] Among them, c is the first superposition coefficient vector, h s is the first channel matrix, U s is the second basis, and pinv(A) represents the pseudo-inverse of matrix A. Optionally, formula (19) is only an example, and the first superposition coefficient vector can also satisfy the deformation based on formula (19), or satisfy the h s and U s The present application does not limit other methods of generating . The first superposition coefficient vector includes L superposition coefficients, the dimension of the first superposition coefficient vector is L*1, and L is a positive integer; for example, c satisfies Optionally, the superposition coefficient vector represents the projection coefficients of the channel matrix on the basis.

[0181] S105, the first device transmits a second superposition coefficient vector and a second basis selection vector; correspondingly, the second device receives the second superposition coefficient vector and the second basis selection vector.

[0182] Among them, the second superposition coefficient vector includes K superposition coefficients, and the K superposition coefficients are the K elements with the largest amplitudes in the first superposition coefficient vector. K is a positive integer less than or equal to L. For example, it is known that the first superposition coefficient vector includes L superposition coefficients. Assuming that the K elements with the largest amplitudes among the L superposition coefficients form the second superposition coefficient vector c′, then c′ satisfies K satisfies 0 < K ≤ L. It can be understood that the K elements with the largest amplitudes among the L superposition coefficients satisfy that the K coefficients are greater than the L - K superposition coefficients other than the K coefficients among the L superposition coefficients; for example, assuming that the L superposition coefficients are 1, 3, 4, 6, 2, 5, then L = 6; assuming K = 3, then the K elements with the largest amplitudes among all the elements of the L superposition coefficients include 4, 5, 6, that is, the second superposition coefficient vector includes three elements, namely 4, 5, 6.

[0183] Among them, the second basis selection vector includes the position indexes of the K superposition coefficients in the first superposition coefficient vector. For example, assuming that the L superposition coefficients are 1, 3, 4, 6, 2, 5, then L = 6; assuming K = 3, then the second superposition coefficient vector includes three superposition coefficients, namely 4, 5, 6. The position indexes of these three superposition coefficients in the first superposition coefficient vector are 3, 6, 4 respectively, that is, the second basis selection vector includes three elements, namely 3, 4, 6.

[0184] Optionally, the first device transmits the second superposition coefficient vector and the second basis selection vector. For example, the first device can use PUCCH / PUSCH to transmit the second superposition coefficient vector and the second basis selection vector to the second device. Optionally, the first device can report the second superposition coefficient vector in a short period, and the first device can report the second basis selection vector in a short period or a long period. This application does not make any restrictions.

[0185] It can be seen that the first device only needs to feedback K superposition coefficients (similar to the short - period superposition coefficients shown in FIG. 8), and the position indexes of the K superposition coefficients in the first superposition coefficient vector (indicating the position indexes in the first basis), which is beneficial to reducing the feedback overhead. For example, since the second device knows the channel map and the first basis, the first device only needs to feedback the position indexes in the first basis, rather than the indexes of one or more basis vectors constituting the first basis and the long - period coefficients (such as the long - period superposition coefficients shown in FIG. 8), thus reducing the feedback overhead.

[0186] In this embodiment, the first basis is a regional channel basis provided by the channel map. The second device transmits the first basis as prior information to the first device, which helps reduce reference signal overhead. Furthermore, the first device only feeds back the location index and short-period superposition coefficient based on the first basis, which helps reduce feedback overhead.

[0187] 1. The channel base updating method provided by this application:

[0188] The first device may multiply the second superposition coefficient vector by the third basis to obtain a second channel matrix, thereby recovering the CSI information. Furthermore, the first device may determine a historical channel basis associated with the historical CSI information based on the recovered CSI information and the historical CSI information, and update the channel basis (e.g., updating the first basis) based on the historical channel basis.

[0189] For example, the channel base updating method provided in this application includes the following steps:

[0190] (1) The first device multiplies the second superposition coefficient vector by the third basis to obtain a second channel matrix. The third basis is composed of K position indices in the second basis selection vector corresponding to the columns of the first basis. For example, the second channel matrix satisfies the formula (20): h = U′×c′ (20)

[0191] Where h is the second channel matrix, U′ is the third basis, and c′ is the second superposition coefficient vector. For example, the second device selects K position indices in the vector according to the second basis, obtains the corresponding columns of the K position indices in the first basis, and constructs the corresponding columns into a third basis U′. The dimension of the third basis is MN×K. For example, U′ satisfies Optionally, the second channel matrix may also satisfy a variation of formula (20), or satisfy other implementation methods of generating the second channel matrix based on the second superposition coefficient vector and the third basis, which is not limited in this application.

[0192] (2) The first device determines the fourth basis based on multiple third channel matrices. The third channel matrix is ​​the channel state information in the spatial frequency domain dimension obtained by channel estimation based on the second reference signal. The second reference signal is the reference signal received before the first reference signal, and the second reference signal and the first reference signal are reference signals of the same type. For example, the second reference signal is the reference signal received before the first reference signal, that is, the second reference signal is a historical reference signal; wherein, the second reference signal can be the reference signal received at the previous moment before the first device receives the first reference signal, or it can be multiple reference signals received at the previous moments before receiving the second reference signal, which is not limited in this application. Moreover, the second reference signal and the first reference signal are reference signals of the same type (for example, if the first reference signal is CSI-RS, the second reference signal is also CSI-RS). The first device performs channel estimation based on the second reference signal and can obtain the third channel matrix in the spatial frequency domain dimension. Since the statistical covariance matrix of the channel h represented by the column vector satisfies formula (5), the statistical covariance matrix of the third channel matrix satisfies formula (21):

[0193] Among them, R h is the statistical covariance matrix of the third channel matrix, U h is the covariance matrix R h The matrix composed of the eigenvectors of (that is, the fourth basis).

[0194] (3) The first device determines the subspace where the fourth basis intersects the first basis as the first common subspace. The subspace where the fourth basis intersects the first basis is also called the common subspace of the fourth basis and the first basis. For example, the fourth basis U h The common subspace with the first basis U is denoted as V (that is, the first common subspace is V), and any vector v in V satisfies formula (22):

[0195] Among them, P U =U(U H U) -1 U H is the projection matrix of U, For U h The projection matrix.

[0196] (4) The first device determines a first non-common subspace, which includes the subspace in the fourth basis excluding the first common subspace. The subspace in the fourth basis excluding the first common subspace is also called a non-common subspace, or a subspace in the fourth basis orthogonal to the first common subspace. For example, the fourth basis U hThe non-public subspace excluding the first public subspace V is D, which satisfies formula (23):

[0197] Where D is the first non-public subspace, represents the direct sum of the subspace.

[0198] (5) The first device sends indication information of the first non-public subspace; correspondingly, the second device receives the indication information of the first non-public subspace. The indication information of the first non-public subspace indicates the projection coefficient of the first non-public subspace on the quantization basis of the first non-public subspace and the column index of the quantization basis of the first non-public subspace. The first non-public subspace is composed of L1 column vectors. For example, the quantization basis of the first non-public subspace is any one of a DFT codebook, an FFT codebook, an oversampled DFT codebook, an oversampled FFT codebook, or a codebook determined based on a preset rule, and the column vector of the first non-public subspace is determined based on the above codebook.

[0199] Optionally, the implementation methods of the indication information of the first non-public subspace and the indication information of the first basis are similar; for example, the indication information of the first non-public subspace includes the first non-public subspace. That is, the first device directly sends the first non-public subspace D to the second device. For another example, the indication information of the first non-public subspace includes the projection coefficient of the first non-public subspace on the quantization basis of the first non-public subspace and the column index of the quantization basis of the first non-public subspace. That is, the first device indirectly indicates the first non-public subspace to the second device. Assume that the first non-public subspace D can adopt the oversampled DFT basis W d Perform projection quantization (that is, the quantization basis of the first non-common subspace is the oversampled DFT basis W d ), then the first non-public subspace D satisfies formula (24): D=W d C d (twenty four)

[0200] Among them, C d Denotes the projection coefficient of D on the oversampled DFT basis. Based on formula (24), the indication information of the first non-common subspace may include the projection coefficient C d , and the column index of the quantization basis of the first non-common subspace. Optionally, the oversampled DFT basis W d Both the first device and the second device are known and identical.

[0201] (6) The second device performs Schmidt orthogonalization on the first basis and the first non-common subspace to obtain a fifth basis. For example, the second device receives indication information of the first non-common subspace, and the indication information of the first non-common subspace includes the projection coefficient C d, and the column index of the quantization basis of the first non-common subspace. The second device can restore the first non-common subspace D=W d C d , and determine that the fifth basis satisfies formula (25): U p =oth{[UW d C d ]} (25)

[0202] Among them, U p represents the fifth basis, the dimension of the fifth basis is MN×(K+L1), for example, U p satisfy oth{A} represents Schmidt orthogonalization of the columns of matrix A. Orthogonalization is required because quantization may destroy the orthogonality between the columns of the basis.

[0203] Optionally, the second device sends the indication information of the fifth basis. The implementation method of the indication information of the fifth basis is similar to that of the indication information of the first basis; for example, the indication information of the fifth basis includes the fifth basis, then the second device sends the fifth basis U to the core network device. p , correspondingly, the core network device receives the fifth basis U p For another example, the indication information of the fifth basis includes the projection coefficient of the fifth basis on the quantization basis of the fifth basis and the column index of the quantization basis of the fifth basis. Optionally, the second device may send the indication information of the first non-public subspace (for example, directly indicating D or indicating W d and C d ), and the first basis U is known to the core network device, then after receiving the indication information of the first non-public subspace, the core network device can also determine the fifth basis. In other words, the second device indirectly indicates the fifth basis to the core network device. Optionally, the core network device is, for example, an AMF, which is equivalent to a router for communication between the second device and the LMF / MMF. The second device then sends the fifth basis U to the LMF / MMF via the AMF. p Optionally, LMF / MMF can be based on the fifth substrate U p Update the channel map; for example, based on the path angle-delay information corresponding to the fifth basis, update the path angle-delay information of the corresponding grid in the channel map.

[0204] Optionally, the first basis, the second basis, the third basis, the fourth basis, or the fifth basis described in the second and third parts above are the same type of basis, and the same type of basis is: a space-frequency joint basis, or a spatial basis and a frequency domain basis. Among them, the space-frequency joint basis is a matrix constructed by one or more space-frequency domain basis vectors; the spatial basis is a matrix constructed by one or more space-domain basis vectors, and the frequency domain basis is a matrix constructed by one or more frequency domain basis vectors. For example, assuming that the first basis is a space-frequency joint basis, the first basis is a matrix constructed by one or more space-frequency domain basis vectors, which can characterize the common characteristics of the space domain and the frequency domain; for another example, assuming that the first basis is a space domain basis and a frequency domain basis, the first basis includes a matrix constructed by one or more space domain basis vectors and a matrix constructed by one or more frequency domain basis vectors (for example, a set of matrices), which respectively characterize the characteristics of the space domain and the frequency domain.

[0205] In this embodiment, the first device can determine the historical channel basis associated with the historical CSI information based on the recovered CSI information and the historical CSI information, and update and report the channel basis based on the historical channel basis, so that the second device and the core network equipment can obtain the updated channel basis information, which is conducive to improving the accuracy of channel estimation.

[0206] 2. Interaction process between the first device and the second device when different reference signals are used and whether the channel basis is updated:

[0207] Example 1: Assuming that the first reference signal is CSI-RS and the channel basis is not updated:

[0208] In this example 1, the second device uses the regional channel basis provided by the channel map as prior information (for example, the first basis can be a space-frequency basis U, the spatial basis U S , frequency domain basis U F , or it can be the spatial compression matrix W s , frequency domain compression matrix W f (Example 1 uses the joint space-frequency basis U as an example) and sends the regional channel basis and the first reference signal. Correspondingly, the first device calculates the short-cycle coefficient based on the regional channel basis and the first reference signal and reports the short-cycle coefficient and its position index on the first basis. The second device recovers the full-dimensional CSI based on the full-dimensional channel basis and short-cycle coefficient provided by the spectrum and the position index on the first basis.

[0209] For example, Figure 10 is a schematic diagram of a channel spectrum combined with CSI-RS enabled downlink channel reconstruction process provided by this application. This process is implemented by interaction between the first device, the second device, and the core network device. The core network device in this application can be AMF / LMF / MMF. The process includes the following steps:

[0210] S201, the second device sends a first request message to the core network device, where the first request message requests to obtain a channel map, or requests to obtain base information corresponding to the first device in the channel map; correspondingly, the core network device receives the first request message.

[0211] S202, the core network device sends a first response message to the second device, where the first response message includes a channel map, or base information corresponding to the first device in the channel map; correspondingly, the second device receives the first response message.

[0212] For example, the channel map is shown in Figure 3. When the first device moves to any grid in the channel map, the second device can trigger a first request message to request the entire channel map, or request the basis information corresponding to the first device in the channel map. The basis information is determined based on the channel map. For example, the space-frequency joint basis can be determined based on the path angle-delay information of the channel map. The space-frequency joint basis corresponding to the first device is determined based on the path angle-delay information of the grid where the first device is located. Optionally, the core network device includes, for example, AMF / LMF / MMF. The interaction between the second device and the core network device can refer to the corresponding description in S101 and will not be repeated here.

[0213] S203, the second device sends the indication information of the first base; correspondingly, the first device receives the indication information of the first base.

[0214] The specific implementation of S202 can refer to the corresponding description in S101. For example, assuming that the first basis is a space-frequency joint basis U, the second device uses PDCCH / PDSCH to send the space-frequency joint basis corresponding to the first device to the first device. Or send the column index of the first basis in the quantization basis of the first basis and C to the first device. 13 , I will not go into details here.

[0215] Optionally, when the first basis is a spatial basis U s , frequency domain basis U F , or it can be the spatial compression matrix W s , frequency domain compression matrix W f The processing flow is similar to that described in S101. For example, assuming that the first basis includes a spatial basis U S and frequency domain basis U F The second device sends the spatial basis U corresponding to the first device to the first device. S and frequency domain basis U F , or sending the spatial basis U to the first device S and frequency domain basis U FThe projection coefficients of the quantization basis B on the first basis respectively, and the column index of the first quantization basis.

[0216] S204, the second device sends a CSI-RS signal; correspondingly, the first device receives the CSI-RS signal.

[0217] The specific implementation of S203 may refer to the corresponding description in S102. For example, the second apparatus transmits a CSI-RS signal to the first apparatus for downlink channel measurement. Optionally, the density ρ of the CSI-RS signal is proportional to the number of columns L of the first basis. For example, the second apparatus may reduce the density of the CSI-RS signal, thereby reducing CSI-RS signal overhead.

[0218] S205: The first device determines a first channel matrix based on the CSI-RS signal.

[0219] S206: The first device determines a first superposition coefficient vector based on a second basis constructed by the first channel matrix and the position index of the CSI-RS signal in the space-frequency domain in the corresponding rows of the first basis.

[0220] The specific implementation of S205 and S206 can refer to the corresponding descriptions in S103 and S104. For example, the first device estimates the corresponding first channel matrix based on the received CSI-RS signal. And according to the position index of the CSI-RS signal in the space-frequency domain, the corresponding row in the first basis is searched to form the second basis Thereby, the first superposition coefficient vector c is determined.

[0221] S207: The first device determines a second superposition coefficient vector and a second basis selection vector based on the first superposition coefficient vector.

[0222] S208 , the first device sends a second superposition coefficient vector and a second basis selection vector; correspondingly, the second device receives the second superposition coefficient vector and the second basis selection vector.

[0223] The specific implementation of S207 and S208 may refer to the corresponding description in S105. For example, the first device selects K superposition coefficients with the largest amplitudes from the first superposition coefficient vector to form a second superposition coefficient vector, and determines K position indexes of the K superposition coefficients in the first superposition coefficient vector to form a second basis selection vector. The first device sends the second superposition coefficient vector (including the K superposition coefficients) and the second basis selection vector (including the K index values) to the second device.

[0224] S209: The second device multiplies the second superposition coefficient vector and the second basis to obtain a second channel matrix.

[0225] The specific implementation of S209 can refer to the description of the second channel matrix in Part 3, which will not be repeated here. Therefore, the second device realizes the recovery of CSI information.

[0226] Optionally, when the first reference signal is other downlink reference signals (such as SSB / DMRS, etc.) and the channel map is not updated, the specific implementation process is similar to that of Example 1, for example, the first reference signal is replaced by CSI-RS with other downlink reference signals, and other processes remain unchanged and will not be repeated here.

[0227] In this first example, the first basis is the regional channel basis provided by the channel map. The second device transmits this basis as prior information to the first device, which helps reduce reference signal overhead. Furthermore, the first device only feeds back the location index and short-period superposition coefficient based on the first basis, which reduces feedback overhead compared to feeding back the entire channel basis.

[0228] Example 2: Assuming that the first reference signal is CSI-RS, and the channel map is updated:

[0229] This example 2 is based on example 1, and adds a process in which the first device calculates the statistical channel basis based on the historical CSI reconstruction results, updates and reports the newly added channel basis information, thereby realizing the update of the channel basis information, which is conducive to improving the channel reconstruction accuracy.

[0230] For example, FIG11 is a schematic diagram of a channel map combined with CSI-RS to enable downlink channel reconstruction and channel basis update process provided by this application. The process is implemented by interaction between the first device, the second device, and the core network device. The process includes the following steps:

[0231] S301, the second device sends a first request message to the core network device, where the first request message requests to obtain a channel map, or requests to obtain base information corresponding to the first device in the channel map; correspondingly, the core network device receives the first request message.

[0232] S302, the core network device sends a first response message to the second device, where the first response message includes a channel map, or base information corresponding to the first device in the channel map; correspondingly, the second device receives the first response message.

[0233] S303, the second device sends the indication information of the first base; correspondingly, the first device receives the indication information of the first base.

[0234] S304, the second device sends a CSI-RS signal; correspondingly, the first device receives the CSI-RS signal.

[0235] S305: The first device determines first channel state information based on the CSI-RS signal.

[0236] S306, the first device determines a first superposition coefficient vector based on a second basis constructed by the first channel state information corresponding to the CSI-RS signal and the position index of the CSI-RS signal in the space-frequency domain corresponding to the row of the first basis.

[0237] S307: The first device determines a second superposition coefficient vector and a second basis selection vector based on the first superposition coefficient vector.

[0238] S308 , the first device sends a second superposition coefficient vector and a second basis selection vector; correspondingly, the second device receives the second superposition coefficient vector and the second basis selection vector.

[0239] S309: The second device multiplies the second superposition coefficient vector and the third basis to obtain a second channel matrix.

[0240] The specific implementation of the above S301-S309 can refer to the corresponding descriptions in S101-S105 and S201-S209, which will not be repeated here.

[0241] S310: The first device determines a fourth basis based on the third channel matrix.

[0242] The specific implementation of this step can refer to the description of the fourth basis and the third channel matrix in the third part. For example, the third channel matrix is ​​the channel state information in the spatial frequency domain dimension obtained by channel estimation based on the second reference signal; the second reference signal is the reference signal received before the first reference signal, that is, the second reference signal is a historical reference signal; the second reference signal and the first reference signal are the same type of reference signals (for example, if the first reference signal is CSI-RS, the second reference signal is also CSI-RS); the fourth basis satisfies formula (21), and other related descriptions are not repeated here.

[0243] S311: The first device determines a common subspace where the fourth basis and the first basis intersect as a first common subspace.

[0244] S312: The first device determines a first non-common subspace, where the first non-common subspace includes a subspace in the fourth basis excluding the first common subspace.

[0245] The specific implementation of S311 and S312 can refer to the description of the first non-common subspace, the first common subspace, and the common subspace where the fourth basis and the first basis intersect in the third part. For example, the first non-common subspace D satisfies formula (23), and the first common subspace V is the fourth basis U h And the common subspace of the first basis U, any vector v in V satisfies formula (22), and other related descriptions, which will not be repeated here.

[0246] S313 , the first device sends indication information of the first non-public subspace; correspondingly, the second device receives the indication information of the first non-public subspace.

[0247] For the specific implementation of S313, reference may be made to the description of the indication information of the first non-common subspace in Section 3. For example, the first apparatus may directly send the first non-common subspace D to the second apparatus, or may send the projection coefficients of the first non-common subspace on the quantization basis of the first non-common subspace and the column index of the quantization basis of the first non-common subspace to the second apparatus, as well as other related descriptions, which are not repeated here.

[0248] S314: The second device performs Schmidt orthogonalization on the first basis and the first non-common subspace to obtain a fifth basis.

[0249] S315, the second device sends indication information of the fifth basis to the core network device.

[0250] For the specific implementation of S314 and S315, please refer to the description of the fifth base and the indication information of the fifth base in the third part. p Formula (25) and other related descriptions are satisfied and will not be repeated here.

[0251] Optionally, when the first reference signal is other downlink reference signals (such as SSB / DMRS, etc.) and the channel map is not updated, the specific implementation process is similar to that of Example 2, for example, the first reference signal is replaced by CSI-RS with other downlink reference signals, and other processes remain unchanged and will not be repeated here.

[0252] In this second example, the first basis is the regional channel basis provided by the channel map. The second device transmits the first basis as prior information to the first device, which helps reduce reference signal overhead. Furthermore, the first device only feeds back the position index and short-period superposition coefficient of the first basis, which reduces feedback overhead compared to feeding back the entire channel basis. Furthermore, the first device can update and report the channel basis based on historical and recovered CSI information, which facilitates further updating of the channel map and improves its accuracy.

[0253] Example 3: Assuming that the first reference signal is a CSI-RS, and the first device sends a third reference signal, so that the second device performs channel estimation based on the first reference signal and the third reference signal:

[0254] This example three is based on example one, and adds a process in which the first device sends a third reference signal (such as an uplink reference signal SRS) so that the second device performs channel estimation based on the third reference signal and recovers the CSI, which is beneficial to improving the CSI reconstruction accuracy.

[0255] For example, FIG12 is a schematic diagram of a channel spectrum combined with CSI-RS and SRS to enable downlink channel reconstruction process provided by this application. The process is implemented by interaction between the first device, the second device and the core network device. The process includes the following steps:

[0256] S401, the second device sends a first request message to the core network device, where the first request message requests to obtain a channel map, or requests to obtain base information corresponding to the first device in the channel map; correspondingly, the core network device receives the first request message.

[0257] S402, the core network device sends a first response message to the second device, where the first response message includes a channel map, or base information corresponding to the first device in the channel map; correspondingly, the second device receives the first response message.

[0258] S403, the second device sends the indication information of the first base; correspondingly, the first device receives the indication information of the first base.

[0259] S404, the second device sends a CSI-RS signal; correspondingly, the first device receives the CSI-RS signal.

[0260] S405: The first device determines a first channel matrix based on the CSI-RS signal.

[0261] S406: The first device determines a first superposition coefficient vector based on a second basis constructed by indexing the first channel matrix and the position of the CSI-RS signal in the space-frequency domain in corresponding rows of the first basis.

[0262] S407: The first device determines a second superposition coefficient vector and a second basis selection vector based on the first superposition coefficient vector.

[0263] S408 , the first device sends a second superposition coefficient vector and a second basis selection vector; correspondingly, the second device receives the second superposition coefficient vector and the second basis selection vector.

[0264] The specific implementation of the above S401-S408 can refer to the corresponding descriptions in S101-S105 and S201-S208, which will not be repeated here.

[0265] S409, the second device sends the first indication information; correspondingly, the first device receives the first indication information.

[0266] S410, the first device sends a third reference signal based on the first indication information; correspondingly, the second device receives the third reference signal.

[0267] The third reference signal is used to measure channel information, and may specifically be an uplink reference signal. For example, the uplink reference signal may include an SRS, etc., which is not limited in this application.

[0268] The first indication information indicates the frequency domain position of the third reference signal. For example, assuming the third reference signal is an SRS, the first indication information indicates the frequency domain position of the SRS, such as indicating the frequency domain unit (such as RE / RB, etc.) carrying the SRS.

[0269] Optionally, the first indication information may further indicate a resource pattern of a third reference signal. For example, assuming that the third reference signal is an SRS, the second apparatus may indicate a resource pattern of an uplink reference signal (eg, an SRS pattern) to the first apparatus through the first indication information.

[0270] Optionally, the first indication information indicates the density of the third reference signal; the density of the third reference signal is positively correlated with the length of the second superposition coefficient vector. Specifically, the density of the third reference signal is proportional to the length of the second superposition coefficient vector. For example, the smaller the length of the second superposition coefficient vector, the fewer the number of channel multipaths, and the fewer the values ​​required for channel measurement; correspondingly, the fewer the reference signals that need to be sent, the smaller the density of the third reference signal. Optionally, the second device can set the density of the third reference signal based on the length of the second superposition coefficient vector, for example, reducing the spatial domain granularity of the third reference signal from M to M2, and the frequency domain granularity from N to N2, thereby reducing the reference signal overhead.

[0271] S411: The second device determines a fourth channel matrix based on the third reference signal.

[0272] S412: The second device determines a third superposition coefficient vector based on a sixth basis constructed by position indexes of the fourth channel matrix and the third reference signal in the space-frequency domain and corresponding rows of the first basis.

[0273] The second device can perform channel estimation based on the third reference signal, and can obtain the fourth channel matrix as the channel state information of the third reference signal in the space-frequency domain. For example, assuming that the third reference signal is an SRS signal, the first device performs channel estimation on the SRS signal and obtains the fourth channel matrix in the space-frequency domain as The dimension of the fourth channel matrix is ​​M2N2×1, for example, satisfy M2 is the spatial domain granularity of the third reference signal, and N2 is the frequency domain granularity of the third reference signal.

[0274] The sixth basis constructed by the position index of the third reference signal in the space-frequency domain in the corresponding row of the first basis is The dimensions of the sixth base are M2N2×L, for example, satisfy For example, the second device receives the third reference signal and can determine the position index of the third reference signal in the space-frequency domain; based on the position index (M2 and N2) of the third reference signal in the space-frequency domain, obtain the row corresponding to the position index from the first basis to form the sixth basis The sixth substrate has the same number of columns as the first substrate.

[0275] The third superposition coefficient vector is determined based on a sixth basis constructed based on the position indexes of the fourth channel matrix and the third reference signal in the space-frequency domain in corresponding rows of the first basis, and satisfies formula (26):

[0276] Among them, c srs is the third superposition coefficient vector, is the fourth channel matrix, is the sixth basis, and pinv(A) represents the pseudo-inverse of the matrix A. Optionally, formula (26) is only an example, and the third superposition coefficient vector can also satisfy the deformation based on formula (26), or satisfy the deformation based on formula (26). and The present application does not limit other methods of generating . The third superposition coefficient vector includes E superposition coefficients, and the dimension of the third superposition coefficient vector is E*1, where E is a positive integer; for example, c srs satisfy

[0277] S413: The second device determines a fourth superposition coefficient vector and a fourth basis selection vector.

[0278] The fourth superposition coefficient vector includes F superposition coefficients, where the F superposition coefficients are the F elements with the largest amplitudes in the third superposition coefficient vector. F is a positive integer less than or equal to E. The fourth basis selection vector includes positional indices of the F superposition coefficients in the third superposition coefficient vector (e.g., including F index values). It will be understood that the specific implementation of the fourth superposition coefficient vector and the fourth basis selection vector is similar to the specific implementation of the second superposition coefficient vector and the second basis selection vector, and reference may be made to the corresponding description above, which will not be repeated here.

[0279] S414: The second device multiplies the fourth superposition coefficient vector and the seventh basis to obtain a fifth channel matrix.

[0280] The seventh basis is composed of the corresponding columns of the F position indices in the fourth basis selection vector in the fifth basis. For example, similar to formula (20), the fifth channel matrix satisfies formula (27): srs =U′ p×c′ srs (27)

[0281] Among them, h srs is the fifth channel matrix, U′ p is the seventh basis, c′ srs For example, the second device selects the F position indexes in the fourth basis vector, obtains the corresponding columns of the F position indexes in the fifth basis, and forms the seventh basis U′ with the corresponding columns p , the dimension of the seventh basis is MN×F, for example, U′ p satisfy Optionally, the fifth channel matrix may also satisfy a variation of formula (27), or satisfy other implementation methods of generating the fifth channel matrix based on the fourth superposition coefficient vector and the seventh basis, which is not limited in this application.

[0282] In this third example, the first basis is the regional channel basis provided by the channel map. The second device transmits the first basis as prior information to the first device, which helps reduce reference signal overhead. Furthermore, the first device only feeds back the position index and short-period superposition coefficient of the first basis, which reduces feedback overhead compared to feeding back the entire channel basis. Furthermore, the first device can also transmit an uplink reference signal, allowing the second device to recover CSI based on the uplink and downlink reference signals, improving CSI reconstruction accuracy.

[0283] Example 4: Assuming that the first reference signal is a CSI-RS, and the first device sends a third reference signal, so that the second device performs channel estimation and channel floor update based on the first reference signal and the third reference signal:

[0284] This example four is based on example three, and adds a second device to calculate the statistical channel basis based on the historical CSI reconstruction results, and update and report the newly added channel basis information, thereby realizing the update of the channel basis information, which is conducive to improving the channel reconstruction accuracy.

[0285] For example, FIG13 is a schematic diagram of a channel spectrum provided by this application in combination with CSI-RS and SRS to enable downlink channel reconstruction and channel basis update process. The process is implemented by the interaction between the first device, the second device and the core network device. The process includes the following steps:

[0286] S501, the second device sends a first request message to the core network device, where the first request message requests to obtain a channel map, or requests to obtain base information corresponding to the first device in the channel map; correspondingly, the core network device receives the first request message.

[0287] S502, the core network device sends a first response message to the second device, where the first response message includes a channel map, or base information corresponding to the first device in the channel map; correspondingly, the second device receives the first response message.

[0288] S503, the second device sends the indication information of the first base; correspondingly, the first device receives the indication information of the first base.

[0289] S504, the second device sends a CSI-RS signal; correspondingly, the first device receives the CSI-RS signal.

[0290] S505: The first device determines a first channel matrix based on the CSI-RS signal.

[0291] S506: The first device determines a first superposition coefficient vector based on a second basis constructed by the first channel matrix and the position index of the CSI-RS signal in the space-frequency domain on the corresponding rows of the first basis.

[0292] S507: The first device determines a second superposition coefficient vector and a second basis selection vector based on the first superposition coefficient vector.

[0293] S508 The first device sends the second superposition coefficient vector and the second basis selection vector; correspondingly, the second device receives the second superposition coefficient vector and the second basis selection vector.

[0294] S509, the second device sends the first indication information; correspondingly, the first device receives the first indication information.

[0295] S510, the first device sends a third reference signal based on the first indication information; correspondingly, the second device receives the third reference signal.

[0296] The specific implementation of the above S501-S510 can refer to the corresponding descriptions in S101-S105 and S401-S410, which will not be repeated here.

[0297] S511: The second device determines a fourth channel matrix based on the third reference signal.

[0298] For example, assuming that the third reference signal is an SRS signal, the first device performs channel estimation on the SRS signal to obtain a fourth channel matrix in the space-frequency domain dimension: The dimension of the fourth channel matrix is ​​M2N2×1, for example, satisfy M2 is the spatial domain granularity of the third reference signal, and N2 is the frequency domain granularity of the third reference signal.

[0299] S512: The second device determines an eighth basis based on the plurality of sixth channel matrices.

[0300] Among them, the sixth channel matrix is ​​the channel state information in the space-frequency domain dimension obtained by channel estimation based on the fourth reference signal, the fourth reference signal is the reference signal received before the third reference signal, and the fourth reference signal and the third reference signal are reference signals of the same type. For example, the fourth reference signal is the reference signal received before the third reference signal, that is, the fourth reference signal is a historical reference signal; wherein, the fourth reference signal can be the reference signal received at the previous moment before the second device receives the third reference signal, or it can be a plurality of reference signals received at the previous moments before receiving the third reference signal, and this application does not limit it. Moreover, the fourth reference signal and the third reference signal are reference signals of the same type (for example, if the third reference signal is SRS, the fourth reference signal is also SRS). The second device performs channel estimation based on the fourth reference signal and can obtain the sixth channel matrix in the space-frequency domain dimension. Since the statistical covariance matrix of the channel h represented by the column vector satisfies formula (5), the statistical covariance matrix of the sixth channel matrix also satisfies formula (21).

[0301] S513: The second device determines a common subspace where the eighth basis intersects the first basis as a second common subspace.

[0302] S514: The first device determines a second non-common subspace, where the second non-common subspace includes a subspace in the eighth basis excluding the second common subspace.

[0303] The common subspace where the eighth basis intersects the first basis is also called the second common subspace. For example, any vector v in the second common subspace also satisfies formula (22). The subspace in the eighth basis excluding the second common subspace is also called the second non-common subspace, or the subspace in the eighth basis that is orthogonal to the second common subspace. For example, the second non-common subspace in the eighth basis excluding the second common subspace also satisfies formula (23).

[0304] S515, the second device performs Schmidt orthogonalization on the fifth basis and the second non-common subspace to obtain a ninth basis.

[0305] S516, the second device sends the indication information of the ninth basis; correspondingly, the core network device receives the indication information of the ninth basis.

[0306] For example, similar to formula (25), the second device determines that the ninth basis satisfies formula (28): U p′ =oth{[U p D′]} (28)

[0307] Among them, U p′represents the ninth basis, the dimension of the ninth basis is MN×(K+L1+L2), for example, U p′ satisfy U p Denotes the fifth basis, and D′ denotes the second non-common subspace.

[0308] Optionally, the second device sends the indication information of the ninth basis. The implementation method of the indication information of the ninth basis is similar to that of the indication information of the first basis; for example, the indication information of the ninth basis includes the ninth basis, then the second device sends the ninth basis U to the core network device. p′ , correspondingly, the core network device receives the ninth basis U p′ For another example, the indication information of the ninth basis includes the projection coefficient of the ninth basis on the quantization basis of the ninth basis and the column index of the quantization basis of the ninth basis. Optionally, the second device may send indication information of the second non-common subspace (for example, directly indicating D′ or indicating the column index of the quantization basis of the second non-common subspace and the projection coefficient of the second non-common subspace), and the fifth basis U p If it is known to the core network device, the core network device can also determine the ninth basis after receiving the indication information of the second non-public subspace. That is, the second device indirectly indicates the ninth basis to the core network device. Optionally, the core network device is, for example, an AMF, and the AMF is equivalent to a router for the second device to communicate with the LMF / MMF, then the second device sends the ninth basis to the LMF / MMF through the AMF. Optionally, the LMF / MMF can update the channel map based on the ninth basis; for example, based on the path angle-delay information corresponding to the ninth basis, the path angle-delay information of the corresponding grid in the channel map is updated.

[0309] S517: The second device determines a fifth superposition coefficient vector based on the fourth channel matrix and the corresponding row of the space-frequency position of the SRS signal on the ninth basis.

[0310] The fifth superposition coefficient vector includes P superposition coefficients, where P is a positive integer. The specific implementation of this step may refer to the corresponding description in S104. For example, the second device searches for the corresponding row of the ninth basis based on the position index of the SRS signal in the spatial frequency domain, and determines that the fifth superposition coefficient vector satisfies formula (29):

[0311] Among them, c srs ′ is the fifth superposition coefficient vector, is the fourth channel matrix, It is composed of the corresponding row of the ninth basis at which the position index of the third reference signal in the space-frequency domain is located.

[0312] S518: The second device determines a sixth superposition coefficient vector and a sixth basis selection vector.

[0313] The sixth superposition coefficient vector includes Q superposition coefficients, where the Q superposition coefficients are the Q elements with the largest amplitudes among all elements in the fifth superposition coefficient vector. The sixth basis selection vector includes positional indices of the Q superposition coefficients in the fifth superposition coefficient vector, where Q is a positive integer less than or equal to P.

[0314] The specific implementation of this step can refer to the description in S104. For example, the sixth superposition coefficient vector is c′ srs , similar to the implementation of the second superposition coefficient vector, the implementation of the sixth basis selection vector is similar to that of the second basis selection vector.

[0315] S519: The second device multiplies the sixth superposition coefficient vector and the tenth basis to obtain a sixth channel matrix.

[0316] The tenth basis is formed by the corresponding columns of the Q position indices in the sixth basis selection vector in the ninth basis. For example, the specific implementation of this step can refer to the specific implementation of the second channel matrix described in Part III. Similar to formula (20), the sixth channel matrix satisfies formula (30): h′ srs =U′ p′ ×c′ srs (30)

[0317] Where h′ srs is the sixth channel matrix, c′ srs is the sixth superposition coefficient vector, U′ p′ For example, the second device selects Q position indexes in the vector according to the sixth basis, obtains the corresponding columns of the Q position indexes in the ninth basis, and forms the tenth basis U′ with the corresponding columns p′ , the dimension of the tenth basis is MN×Q, for example, U′ p′ satisfy Optionally, the sixth channel matrix may also satisfy a variation of formula (30), or satisfy other implementation methods of generating the sixth channel matrix based on the sixth superposition coefficient vector and the tenth basis, which is not limited in this application.

[0318] In this fourth example, the first basis is the regional channel basis provided by the channel map. The second device transmits the first basis as prior information to the first device, which helps reduce reference signal overhead. Furthermore, the first device only feeds back the position index and short-cycle superposition coefficient of the first basis, which helps reduce feedback overhead. Furthermore, the first device can also transmit an uplink reference signal, allowing the second device to recover the CSI based on the uplink reference signal and the downlink reference signal, which helps improve CSI reconstruction accuracy. Furthermore, the first device can update and report the channel basis based on historical CSI information and recovered CSI information, which helps further update the channel map and improve its accuracy.

[0319] Example 5: Assuming that the first device sends a third reference signal, so that the second device performs channel estimation and channel floor update based on the third reference signal:

[0320] The channel estimation solution provided in Example 5 may be a solution in which the second device directly performs channel estimation and channel basis update based on SRS (not based on CSI-RS), which can improve the accuracy of channel reconstruction.

[0321] For example, FIG14 is a schematic diagram of a channel map combined with an SRS-enabled channel reconstruction and channel base update process provided by this application. The process is implemented by the interaction between the first device, the second device, and the core network device. The process includes the following steps:

[0322] S601, the second device sends a first request message to the core network device, where the first request message requests to obtain a channel map, or requests to obtain base information corresponding to the first device in the channel map; correspondingly, the core network device receives the first request message.

[0323] S602, the core network device sends a first response message to the second device, where the first response message includes a channel map, or base information corresponding to the first device in the channel map; correspondingly, the second device receives the first response message.

[0324] The specific implementation of the above S601 and S602 can refer to the corresponding descriptions in S101 and S102 and S201 and S202, and will not be repeated here.

[0325] S603, the second device sends the first indication information; correspondingly, the first device receives the first indication information.

[0326] S604, the first device sends an SRS signal based on the first indication information; correspondingly, the second device receives the SRS signal.

[0327] S605: The second device determines a fourth channel matrix based on the SRS signal.

[0328] S606: The second device determines an eighth basis based on the plurality of sixth channel matrices.

[0329] S607: The second device determines a common subspace where the eighth basis intersects the first basis as a second common subspace.

[0330] S608: The first device determines a second non-common subspace, where the second non-common subspace includes a subspace in the eighth basis excluding the second common subspace.

[0331] S609: The second device performs Schmidt orthogonalization on the fifth basis and the second non-common subspace to obtain a ninth basis.

[0332] S610, the second device sends indication information of the ninth basis; correspondingly, the core network device receives the indication information of the ninth basis.

[0333] S611: The second device determines a fifth superposition coefficient vector based on the fourth channel matrix and the corresponding row of the space-frequency position of the SRS signal on the ninth basis.

[0334] S612: The second device determines a sixth superposition coefficient vector and a sixth basis selection vector.

[0335] S613: The second device multiplies the sixth superposition coefficient vector and the tenth basis to obtain a sixth channel matrix.

[0336] Among them, the specific implementation method of S603-S613 can refer to the corresponding description in S509-S519, which will not be repeated here.

[0337] In this fifth example, the first basis is the regional channel basis provided by the channel map. The second device transmits the first basis as a priori information to the first device, which helps reduce reference signal overhead. Furthermore, without considering the downlink reference signal, the first device can transmit an uplink reference signal, allowing the second device to perform channel reconstruction based on the uplink reference signal (SRS). Furthermore, the first device can update the channel basis based on historical and current SRS signal information, which helps further update the channel map and improve its accuracy.

[0338] It is understood that, in order to implement the functions in the above embodiments, the base station and the terminal include hardware structures and / or software modules corresponding to the execution of each function. Those skilled in the art should readily appreciate that, in conjunction with the units and method steps of the various examples described in the embodiments disclosed in this application, this application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in hardware or in a computer software-driven hardware manner depends on the specific application scenario and design constraints of the technical solution.

[0339] Figures 15 and 16 are schematic diagrams of the structures of possible communication devices provided in the embodiments of the present application. These communication devices can be used to implement the functions of the terminal or base station in the above method embodiments, and thus can also achieve the beneficial effects possessed by the above method embodiments. In the embodiments of the present application, the communication device can be the terminal 120 as shown in Figure 1, or the base station 110 as shown in Figure 1, or a module (such as a chip) applied to the terminal or base station.

[0340] As shown in Figure 15, communication device 1500 includes a processing unit 1510 and a transceiver unit 1520. Communication device 1500 is used to implement the functions of a terminal or base station in the method embodiments shown in Figures 9 to 14 above. Optionally, transceiver unit 1520 may also be referred to as a communication unit. Optionally, the transceiver unit includes a transmitting unit and a receiving unit, where the transmitting unit is used to transmit signals and the receiving unit is used to receive signals.

[0341] For example, when the communication device 1500 is used to implement the functions of a terminal in the method embodiment shown in FIG9 , the transceiver unit 1520 is configured to receive indication information of a first basis, where the indication information of the first basis indicates projection coefficients of the first basis on a quantization basis of the first basis and column indices of the quantization basis of the first basis. The processing unit 1510 is configured to determine and record the first basis. The transceiver unit 1520 is further configured to receive a first reference signal and determine a first channel matrix based on the first reference signal. The processing unit 1510 is further configured to determine a first superposition coefficient vector based on a second basis constructed by position indices of the first channel matrix and the first reference signal in the spatial-frequency domain in corresponding rows of the first basis. The processing unit 1510 is further configured to select K superposition coefficient vectors with the largest amplitudes from the first superposition coefficient vector to form a second superposition coefficient vector, and determine the position indices of the K superposition coefficient vectors in the first superposition coefficient vector to form a second basis selection vector. The transceiver unit 1520 is further configured to transmit the second superposition coefficient vector and the second basis selection vector.

[0342] For another example, when the communication device 1500 is used to implement the functions of the network device in the method embodiment shown in FIG9 : the transceiver unit 1520 is configured to transmit indication information of a first basis, where the indication information of the first basis indicates the projection coefficients of the first basis on the quantization basis of the first basis and the column index of the quantization basis of the first basis. The transceiver unit 1520 is further configured to transmit a first reference signal, so that a receiver of the first reference signal can perform channel estimation based on the first reference signal to obtain a first channel matrix. The receiver of the first reference signal can determine a first superposition coefficient vector based on a second basis constructed by the position indexes of the first channel matrix and the first reference signal in the space-frequency domain corresponding to the rows of the first basis, thereby determining to select the K superposition coefficient vectors with the largest amplitudes in the first superposition coefficient vector to form a second superposition coefficient vector, and the position indexes of the K superposition coefficient vectors in the first superposition coefficient vector to form a second basis selection vector. The transceiver unit 1520 is further configured to receive the second superposition coefficient vector and the second basis selection vector. The processing unit 1510 is configured to process data received by the transceiver unit 1520.

[0343] For a more detailed description of the processing unit 1510 and the transceiver unit 1520 , reference may be made to the relevant description in the method embodiment shown in FIG. 9 .

[0344] Optionally, when the communication device 1500 is used to implement the functions of a terminal or base station in the method embodiments of Figures 10 to 14, a more detailed description of the above-mentioned processing unit 1510 and the transceiver unit 1520 can be referred to the relevant description in the method embodiments shown in Figures 10 to 14, and will not be repeated here.

[0345] As shown in Figure 16, communication device 1600 includes a processor 1610 and an interface circuit 1620. Processor 1610 and interface circuit 1620 are coupled to each other. It is understood that interface circuit 1620 can be a transceiver or an input / output interface. Optionally, communication device 1600 may also include a memory 1630 for storing instructions executed by processor 1610, or storing input data required by processor 1610 to execute instructions, or storing data generated after processor 1610 executes instructions. Sometimes, interface circuit 1620 can also be understood as part of processor 1610, in which case communication device 1600 includes processor 1610.

[0346] When the communication device 1600 is used to implement the method shown in FIG9 , the processor 1610 is used to implement the functions of the processing unit 1510, and the interface circuit 1620 is used to implement the functions of the transceiver unit 1520. Optionally, when the communication device 1600 is used to implement the methods shown in FIG10 to FIG14 , the implementation of the processor 1610 and the interface circuit 1620 refers to the corresponding description in the method embodiment, and will not be repeated here.

[0347] When the above-mentioned communication device is a chip applied to a terminal, the terminal chip implements the functions of the terminal in the above-mentioned method embodiment. When the terminal chip receives information from the base station, it can be understood that the information is first received by other modules in the terminal (such as a radio frequency module or antenna) and then sent to the terminal chip by these modules. When the terminal chip sends information to the base station, it can be understood that the information is first sent to other modules in the terminal (such as a radio frequency module or antenna) and then sent to the base station by these modules.

[0348] When the above-mentioned communication device is a chip applied to a base station, the base station chip implements the functions of the base station in the above-mentioned method embodiment. When the base station chip receives information from the terminal, it can be understood that the information is first received by other modules in the base station (such as a radio frequency module or antenna) and then sent to the base station chip by these modules. When the base station chip sends information to the terminal, it can be understood that the information is sent to other modules in the base station (such as a radio frequency module or antenna) and then sent to the terminal by these modules.

[0349] In this application, when entity A sends information to entity B, it can be done directly from A to B or indirectly through another entity. Similarly, when entity B receives information from entity A, it can be done directly from entity B or indirectly through another entity. Entities A and B herein can be RAN nodes or terminals, or modules within a RAN node or terminal. The sending and receiving of information can be information exchange between a RAN node and a terminal, for example, between a base station and a terminal; the sending and receiving of information can also be information exchange between two RAN nodes, for example, between a CU and a DU; the sending and receiving of information can also be information exchange between different modules within a device, for example, between a terminal chip and other modules in the terminal, or between a base station chip and other modules within the base station.

[0350] It is understood that the processor in the embodiments of the present application may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0351] The method steps in the embodiments of the present application can be implemented in hardware or in software instructions that can be executed by a processor. The software instructions can be composed of corresponding software modules, and the software modules can be stored in random access memory, flash memory, read-only memory, programmable read-only memory, erasable programmable read-only memory, electrically erasable programmable read-only memory, registers, hard disk, mobile hard disk, CD-ROM or any other form of storage medium well known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. The storage medium can also be an integral part of the processor. The processor and storage medium can be located in an ASIC. In addition, the ASIC can be located in a base station or a terminal. The processor and storage medium can also exist in a base station or a terminal as discrete components.

[0352] In the above embodiments, all or part of the embodiments may be implemented using software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments may be implemented in the form of a computer program product. The computer program product includes one or more computer programs or instructions. When the computer program or instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present application are performed in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, a network device, a user device, or other programmable device. The computer program or instructions may be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another. For example, the computer program or instructions may be transferred from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. The computer-readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium may be a magnetic medium, such as a floppy disk, hard disk, or magnetic tape; an optical medium, such as a digital video disk; or a semiconductor medium, such as a solid-state drive. The computer-readable storage medium may be a volatile or nonvolatile storage medium, or may include both volatile and nonvolatile types of storage media.

[0353] In the various embodiments of the present application, unless otherwise specified or there is any logical conflict, the terms and / or descriptions between different embodiments are consistent and can be referenced by each other. The technical features in different embodiments can be combined to form new embodiments according to their inherent logical relationships.

[0354] It is understood that the various numbers used in the embodiments of this application are merely for ease of description and are not intended to limit the scope of the embodiments of this application. The order of the sequence numbers of the above-mentioned processes does not necessarily imply a specific order of execution; the order of execution of the processes should be determined by their functions and inherent logic.

[0355] In this application, "at least one" means one or more, and "more" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. In the text description of this application, the character " / " generally indicates that the previous and next associated objects are in an "or" relationship; in the formula of this application, the character " / " indicates that the previous and next associated objects are in a "division" relationship. "Including at least one of A, B and C" can mean: including A; including B; including C; including A and B; including A and C; including B and C; including A, B and C.

Claims

1. A communication method, characterized in that: The method comprises: receiving indication information of a first basis, where the indication information of the first basis indicates a projection coefficient of the first basis on a quantization basis of the first basis and a column index of the quantization basis of the first basis; the first basis is composed of L column basis vectors, where L is a positive integer; receiving a first reference signal, and determining a first channel matrix based on the first reference signal; Determine a first superposition coefficient vector based on a second basis constructed by indexing the positions of the first channel matrix and the first reference signal in the space-frequency domain in corresponding rows of the first basis, wherein the dimension of the first channel matrix is ​​MN1*1, the dimension of the second basis is MN1*L, M is the number of antenna ports receiving the first reference signal, and N1 is the number of frequency domain units carrying the first reference signal; the first superposition coefficient vector includes L superposition coefficients, the dimension of the first superposition coefficient vector is L*1, M and N1 are positive integers, and L is less than or equal to MN1; Send a second superposition coefficient vector and a second basis selection vector, where the second superposition coefficient vector includes K superposition coefficients, and the K superposition coefficients are the K elements with the largest amplitudes in the first superposition coefficient vector; the second basis selection vector includes the position indexes of the K superposition coefficients in the first superposition coefficient vector, and K is a positive integer less than or equal to L.

2. A communication method, characterized in that: The method comprises: Receiving indication information of a first basis, where the indication information of the first basis indicates projection coefficients of a channel covariance matrix on a quantization basis and indexes corresponding to the projection coefficients on the quantization basis; Determine the channel covariance matrix based on the indicated projection coefficients and indexes of the channel covariance matrix; perform singular value decomposition or eigendecomposition on the channel covariance matrix to obtain a first basis corresponding to the channel covariance matrix; the first basis is composed of L columns of basis vectors, where L is a positive integer; receiving a first reference signal, and determining a first channel matrix based on the first reference signal; Determine a first superposition coefficient vector based on a second basis constructed by indexing the positions of the first channel matrix and the first reference signal in the space-frequency domain in corresponding rows of the first basis, wherein the dimension of the first channel matrix is ​​MN1*1, the dimension of the second basis is MN1*L, M is the number of antenna ports receiving the first reference signal, and N1 is the number of frequency domain units carrying the first reference signal; the first superposition coefficient vector includes L superposition coefficients, the dimension of the first superposition coefficient vector is L*1, M and N1 are positive integers, and L is less than or equal to MN1; Send a second superposition coefficient vector and a second basis selection vector, where the second superposition coefficient vector includes K superposition coefficients, and the K superposition coefficients are the K elements with the largest amplitudes in the first superposition coefficient vector; the second basis selection vector includes the position indexes of the K superposition coefficients in the first superposition coefficient vector, and K is a positive integer less than or equal to L.

3. The method according to claim 1 or 2, characterized in that: The method further comprises: The second superposition coefficient vector is multiplied by a third basis to obtain a second channel matrix; the third basis is composed of K position indices in the second basis selection vector in corresponding columns of the first basis.

4. The method according to claim 1 or 2, characterized in that: The method further comprises: determining a fourth basis based on a third channel matrix, wherein the third channel matrix is ​​channel state information in a space-frequency domain dimension obtained by performing channel estimation based on a second reference signal, wherein the second reference signal is a reference signal received before the first reference signal, and the second reference signal and the first reference signal are reference signals of the same type; Determine a first non-common subspace, where the first non-common subspace includes a subspace of the fourth basis excluding the first common subspace, and the first common subspace is a common subspace where the fourth basis and the first basis intersect; Send indication information of the first non-common subspace, wherein the indication information of the first non-common subspace indicates the projection coefficient of the first non-common subspace on the quantization basis of the first non-common subspace and the column index of the quantization basis of the first non-common subspace; the first non-common subspace is composed of L1 column basis vectors, and L1 is a positive integer.

5. The method according to any one of claims 1 to 4, characterized in that: The method further comprises: receiving first indication information, where the first indication information indicates a frequency domain position at which a third reference signal is sent; The third reference signal is sent based on the first indication information.

6. The method according to any one of claims 1 to 4, characterized in that: The first basis, the second basis, the third basis, the fourth basis, or the fifth basis is a same type of basis, and the same type of basis is: a space-frequency joint basis, or a space domain basis and a frequency domain basis; Among them, the space-frequency joint basis is a matrix constructed by one or more space-frequency domain basis vectors; the space domain basis is a matrix constructed by one or more space domain basis vectors, and the frequency domain basis is a matrix constructed by one or more frequency domain basis vectors.

7. The method according to any one of claims 1 to 4, characterized in that: The basis vectors are any one of discrete Fourier transform DFT basis vectors, fast Fourier transform FFT basis vectors, oversampled DFT basis vectors, oversampled FFT basis vectors, or vectors determined based on preset rules.

8. A communication method, characterized in that: The method comprises: Sending indication information of a first basis, where the indication information of the first basis indicates a projection coefficient of the first basis on a quantization basis of the first basis and a column index of the quantization basis of the first basis; the first basis is composed of L column basis vectors, where L is a positive integer; sending a first reference signal; Receive a second superposition coefficient vector and a second basis selection vector, the second superposition coefficient vector including K superposition coefficients, the K superposition coefficients being the K elements with the largest amplitudes in the first superposition coefficient vector; the second basis selection vector including position indexes of the K superposition coefficients in the first superposition coefficient vector, the first superposition coefficient vector being obtained based on a second basis constructed based on position indexes of a first channel matrix and the first reference signal in the space-frequency domain in corresponding rows of the first basis, the first channel matrix being determined based on the first reference signal; wherein the dimension of the first channel matrix is ​​MN1*1, the dimension of the second basis is MN1*L, M is the number of antenna ports for sending the first reference signal, and N1 is the number of frequency domain units carrying the first reference signal; the first superposition coefficient vector includes L superposition coefficients, the dimension of the first superposition coefficient vector is L*1, M and N1 are positive integers, L is less than or equal to MN1, and K is a positive integer less than or equal to L.

9. A communication method, characterized in that: The method comprises: Sending indication information of a first basis, where the indication information of the first basis indicates projection coefficients of a channel covariance matrix on a quantized basis and indexes corresponding to the projection coefficients on the quantized basis, and the projection coefficients and indexes of the channel covariance matrix are used by a receiving end to restore the channel covariance matrix and determine a first basis; the first basis is composed of L columns of basis vectors, where L is a positive integer; sending a first reference signal; Receive a second superposition coefficient vector and a second basis selection vector, the second superposition coefficient vector including K superposition coefficients, the K superposition coefficients being the K elements with the largest amplitudes in the first superposition coefficient vector; the second basis selection vector including position indexes of the K superposition coefficients in the first superposition coefficient vector, the first superposition coefficient vector being obtained based on a second basis constructed based on position indexes of a first channel matrix and the first reference signal in the space-frequency domain in corresponding rows of the first basis, the first channel matrix being determined based on the first reference signal; wherein the dimension of the first channel matrix is ​​MN1*1, the dimension of the second basis is MN1*L, M is the number of antenna ports for sending the first reference signal, and N1 is the number of frequency domain units carrying the first reference signal; the first superposition coefficient vector includes L superposition coefficients, the dimension of the first superposition coefficient vector is L*1, M and N1 are positive integers, L is less than or equal to MN1, and K is a positive integer less than or equal to L.

10. The method according to claim 8 or 9, characterized in that: The method further comprises: The second superposition coefficient vector is multiplied by a third basis to obtain a second channel matrix; the third basis is composed of K position indices in the second basis selection vector in corresponding columns of the first basis.

11. The method according to claim 8 or 9, characterized in that: The method further comprises: Receive indication information of a first non-common subspace, where the indication information of the first non-common subspace indicates a projection coefficient of the first non-common subspace on a quantization basis of the first non-common subspace and a column index of the quantization basis of the first non-common subspace; the first non-common subspace is composed of L1 column basis vectors, where L1 is a positive integer; Performing Schmidt orthogonalization on the first basis and the first non-common subspace to obtain a fifth basis; Send indication information of the fifth basis, wherein the indication information of the fifth basis indicates the fifth basis, or indicates the projection coefficient of the fifth basis on the quantization basis of the fifth basis and the column index of the quantization basis of the fifth basis; the fifth basis is composed of (L+L1) column vectors.

12. The method according to any one of claims 8 to 11, characterized in that The method further comprises: Sending first indication information, where the first indication information indicates a frequency domain position at which a third reference signal is sent; A third reference signal is received.

13. The method according to any one of claims 8 to 11, characterized in that The first basis, the second basis, the third basis, the fourth basis, or the fifth basis are the same type of basis, and the same type of basis is: a joint space-frequency basis, or a spatial domain basis and a frequency domain basis; the joint space-frequency basis is a matrix constructed by one or more space-frequency domain basis vectors; the spatial domain basis is a matrix constructed by one or more spatial domain basis vectors, and the frequency domain basis is a matrix constructed by one or more frequency domain basis vectors.

14. The method according to any one of claims 8 to 11, characterized in that The basis vectors are any one of discrete Fourier transform DFT basis vectors, fast Fourier transform FFT basis vectors, oversampled DFT basis vectors, oversampled FFT basis vectors, or vectors determined based on preset rules.

15. A communication device, characterized in that: The method comprises a communication unit and a processing unit, wherein the communication unit and the processing unit are used to execute the method according to any one of claims 1 to 7 or 8 to 14.

16. A communication device, characterized in that: It includes a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices and transmit them to the processor or send signals from the processor to other communication devices, and the processor is used to implement the method as described in any one of claims 1 to 7 or 8 to 14 through a logic circuit or executing code instructions.

17. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program or instruction. When the computer program or instruction is executed by the communication device, the method according to any one of claims 1 to 7 or 8 to 14 is implemented.

18. A chip system, characterized in that: The chip system comprises a processor and an interface, wherein the processor is configured to execute a computer program so that the chip system implements the method as claimed in any one of claims 1 to 7 or 8 to 14.

19. A computer program product, characterized in that The method comprises instructions which, when executed on a computer, cause the computer to perform the method according to any one of claims 1 to 7 or 8 to 14.

20. A communication system, characterized in that: The communication system comprises an apparatus for executing the method according to any one of claims 1 to 7, and an apparatus for executing the method according to any one of claims 8 to 14.

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