A channel estimation method, device and system

Abstract

This application relates to a channel estimation method, apparatus, and system. A terminal device transmits T1 reference signals, which are reflected to a network device via a RIS (Reference Array Indicator). T1 is a positive integer less than M, where M is the number of element arrays included in the RIS. The terminal device receives first information from the network device indicating the value of T2, where T2 is a positive integer less than M. The terminal device then transmits T2 reference signals, which are reflected to the network device via the RIS. These T2 reference signals are used to estimate a concatenated channel, which includes the channel between the network device and the RIS, and the channel between the RIS and the terminal device. The technical solution of this application can reduce the transmission overhead of the reference signals.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to a channel estimation method, apparatus and system. Background Technology

[0002] RIS-assisted networks, which control channel characteristics through reconfigurable intelligent meta-surfaces (RIS), are considered a key enabling technology for extending the coverage of wireless communication networks. RIS can be installed on large planes (such as indoor walls or ceilings, outdoor buildings or signs) to reflect radio frequency (RF) energy around obstacles and create a virtual line-of-sight (LoS) propagation path between the communication source and the target.

[0003] Taking a communication between a base station and user equipment (UE) as an example, the RIS channel can include the channel between the base station and the RIS, as well as the channel between the RIS and the UE. By estimating the RIS channel, the base station can perform downlink precoding and other processing. The RIS consists of multiple element arrays; to estimate the RIS channel, the number of reference signals transmitted by the UE needs to be greater than or equal to the number of element arrays in the RIS. Since the number of element arrays in a RIS is typically large, such as thousands, the overhead of reference signals due to RIS channel estimation is substantial. Summary of the Invention

[0004] This application provides a channel estimation method, apparatus, and system for reducing the overhead of the reference signal when estimating the RIS channel.

[0005] In a first aspect, a first channel estimation method is provided. This method can be executed by a terminal device, or by another device including the functions of the terminal device, or by a chip system (or chip) or other functional module capable of implementing the corresponding functions of the terminal device, such as being disposed in the terminal device. The method includes: transmitting T1 reference signals, the T1 reference signals being reflected to a network device via a RIS, where T1 is a positive integer less than M, and M is the number of element arrays included in the RIS; receiving first information from the network device, the first information indicating a value of T2, where T2 is a positive integer less than M; and transmitting T2 reference signals, the T2 reference signals being reflected to the network device via the RIS, the T2 reference signals being used to estimate a cascaded channel, the cascaded channel including a channel between the network device and the RIS, and a channel including the RIS and the terminal device.

[0006] In this embodiment, the terminal device can send two rounds of reference signals. In the first round, T1 reference signals are sent, where T1 is less than the total number of element arrays M included in the RIS. In the second round, T2 reference signals are sent, where T2 is a value indicated by the network device, and T2 is also less than M. For example, the sum of T1 and T2 is also less than M. Therefore, the number of reference signals sent by the terminal device is much smaller than the total number of element arrays included in the RIS, thereby saving the overhead of reference signals.

[0007] In one optional implementation, the value of T1 is predefined; or, the value of N is predefined; or, the method further includes: receiving second information from the network device, the second information being used to indicate the value of T1, or to indicate the value of N, where N is the number of element subarrays included in the first subarray of the RIS, the first subarray being used to reflect the T1 reference signals, wherein T1 is a positive integer greater than or equal to N. For example, if the value of T1 is predefined by the protocol, the terminal device can directly determine the value of T1 without the network device needing to indicate it, thus saving signaling overhead. Alternatively, if the value of N is predefined by the protocol, the terminal device can determine the value of T1 by setting T1 to be greater than or equal to N, without the need for the network device to indicate it. Alternatively, the value of T1 can also be determined and indicated by the network device, allowing for more flexible selection of the value of T1.

[0008] Secondly, a second channel estimation method is provided, which can be executed by a network device, or by other devices including network device functions, or by a chip system (or chip) or other functional module capable of implementing the functions of the network device, for example, being disposed within the network device. The method includes: receiving T1 reference signals reflected from a terminal device by a first subarray of a RIS, the RIS comprising M element elements, the first subarray comprising N element elements from the M element elements, where M is a positive integer, N is a positive integer less than M, and T1 is a positive integer greater than or equal to N and less than M; estimating the path of the cascaded channel in the angular domain based on the T1 reference signals, and determining a first codebook based on the path of the angular domain, the first codebook comprising at least one weight, the at least one weight being the weight of E element elements from the M element elements, the cascaded channel comprising... The channel between the network device and the RIS, and the channel between the RIS and the terminal device, where E is a positive integer less than or equal to M; third information is sent to the RIS, the third information indicating the first codebook, the first codebook being used by the RIS to reflect reference signals; T2 reference signals reflected from the terminal device by the E unit arrays, wherein the T2 reference signals are processed according to the first codebook, and T2 is a positive integer greater than or equal to the diameter of the angular domain and less than M; the cascaded channel is estimated based on the T2 reference signals. For the technical effects of this method, please refer to the description of the technical effects of the first aspect.

[0009] In one alternative implementation, the first codebook satisfies the following relationship: Among them, W Dr This represents the first codebook. D represents the new dictionary matrix of the angle domain obtained according to the first codebook. r Let X represent the original dictionary matrix of the angle domain, L represent the diameter of the angle domain, and X represent the original dictionary matrix of the angle domain. H Let X be the conjugate transpose of matrix X, and D(:,L) represent the L column vectors of matrix D. Since the construction of the dictionary matrix for the angle domain is similar to that of the DFT matrix, each column of the dictionary matrix is ​​mutually orthogonal. Therefore, if the new matrix obtained after weighting is still a dictionary matrix, it can be guaranteed that the new matrix remains orthogonal to the radius of the angle domain. In the embodiments of this application, This represents the new dictionary matrix in the angle domain obtained from the first codebook. In other words, after weighting the unit arrays of RIS according to the weights included in the first codebook, the new matrix obtained is still a dictionary matrix. This ensures the orthogonality of the new dictionary matrix with the path in the angle domain, thereby improving the accuracy of channel estimation.

[0010] In one alternative implementation, The dimension is T2×R, where R represents the resolution of the angular domain.

[0011] In one alternative implementation, the first subarray is a linear array, D r The dimension is N×R; or, the first subarray is a planar array. Among them, D rH D represents a row matrix. rV D represents a column matrix. rH The dimension is p×R, D rV The dimension of the matrix is ​​q×R, and the dimension of the first submatrix is ​​p×q. This represents calculating the Kronecker product of a and b. Where R represents the resolution of the angular domain. D r It can be used to weight the first subarray, therefore D r The dimension can vary depending on the first subarray.

[0012] In one optional implementation, sending third information to the RIS includes: sending the first codebook to the RIS; or sending the index of the path of the angle domain in the original dictionary matrix of the angle domain to the RIS. The network device can directly send the first codebook to the RIS, allowing the RIS to obtain the first codebook without performing other processing, thus simplifying the implementation of the RIS. Alternatively, the network device can also send the index of the path of the angle domain to the RIS, from which the RIS can obtain the first codebook. The index of the path of the angle domain contains less information than the first codebook, thereby saving signaling overhead.

[0013] In one optional implementation, estimating the diameter of the cascaded channel in the angle domain based on the T1 reference signals includes: using a compressed sensing algorithm or a statistical algorithm, etc., to estimate the diameter of the angle domain based on the T1 reference signals. This application does not limit the algorithm used.

[0014] In an optional implementation, the method further includes: sending fourth information to the RIS, the fourth information including one or more of the following: the value of N, the number of rows of the N cell arrays, or the number of columns of the N cell arrays. For example, if the first subarray is determined by a network device, the network device can send relevant parameters of the first subarray to the RIS, enabling the RIS to determine the first subarray accordingly. Alternatively, the first subarray can also be determined by another device, in which case the other device can send the parameters of the first subarray to the RIS, and optionally, also to the network device. Alternatively, the first subarray can also be determined by the RIS, in which case the RIS can send the fourth information to the network device to indicate the parameters of the first subarray.

[0015] In one alternative implementation, the N cell elements are consecutive cell elements. The N cell elements can be continuously distributed cell elements, thereby simplifying the calculation process when the network device estimates the diameter in the angular domain.

[0016] Thirdly, a third channel estimation method is provided, which can be performed by a RIS or a component in a RIS (such as a RIS device). This component includes, for example, at least one of a processor, transceiver, processing unit, or transceiver unit. Taking a RIS (Real Integrity Array) as an example, the method may include: sending T1 reference signals reflected from a first subarray of the RIS to a network device, wherein the RIS comprises M unit arrays, the first subarray comprises N unit arrays from the M unit arrays, M is a positive integer, N is a positive integer less than M, and T1 is a positive integer greater than or equal to N and less than M; receiving third information from the network device, the third information being used to indicate a first codebook, the first codebook comprising at least one weight, the at least one weight being the weight of E unit arrays from the M unit arrays, the first codebook being determined based on the T1 reference signals, E being a positive integer less than or equal to M; sending T2 reference signals reflected from the E unit arrays to the network device, the T2 reference signals being used to estimate a concatenated channel, wherein the T2 reference signals are processed based on the first codebook, T2 being a positive integer greater than or equal to the diameter of the angular domain of the concatenated channel and less than M, the concatenated channel including a channel between the network device and the RIS, and a channel including the RIS and the terminal device.

[0017] In one alternative implementation, the first codebook satisfies the following relationship: Among them, W Dr This represents the first codebook. D represents the new dictionary matrix of the angle domain obtained according to the first codebook. r Let X represent the original dictionary matrix of the angle domain, L represent the diameter of the angle domain, and X represent the original dictionary matrix of the angle domain. H Let X denote the conjugate transpose of matrix X, and D(:,L) denote the L column vectors of matrix D.

[0018] In one alternative implementation, The dimension is T2×R, where R represents the resolution of the angular domain.

[0019] In one alternative implementation, the first subarray is a linear array, D r The dimension is N sub ×R, N sub This indicates the number of element subarrays included in the first subarray; or, the first subarray is a planar array. Among them, D rHD represents a row matrix. rV D represents a column matrix. rH The dimension is p×R, D rV The dimension of the matrix is ​​q×R, and the dimension of the first submatrix is ​​p×q. This represents the Kronecker product of a and b; where R represents the resolution of the angular domain.

[0020] In one optional implementation, receiving third information from the network device includes: receiving the first codebook from the network device; or, receiving the index of the angular field's path in the original dictionary matrix of the angular field from the network device.

[0021] In one optional implementation, the method further includes: receiving fourth information from the network device, the fourth information including one or more of the following: the value of N, the number of rows of the N cell arrays, or the number of columns of the N cell arrays.

[0022] In one alternative implementation, the N unit arrays are consecutive unit arrays.

[0023] Regarding the technical effects of the third aspect or various alternative implementations, refer to the description of the technical effects of the first aspect or corresponding implementations, and / or refer to the description of the technical effects of the second aspect or corresponding implementations.

[0024] Fourthly, a communication apparatus is provided. This apparatus can implement the methods executed by a RIS in the first, second, or third aspects and any possible designs thereof; or, it can implement the methods executed by a network device in the first, second, or third aspects and any possible designs thereof; or, it can implement the methods executed by a terminal device in the first, second, or third aspects and any possible designs thereof. The apparatus may be, for example, a RIS, a terminal device, a network device, a component in a RIS, a component in a terminal device, or a component in a network device.

[0025] In one optional implementation, the device may include modules corresponding to the methods / operations / steps / actions described in the first to third aspects and any possible implementations above. These modules may be hardware circuits, software, or a combination of hardware circuits and software. In another optional implementation, the device includes a processing unit (sometimes also called a processing module) and a transceiver unit (sometimes also called a communication unit, communication module, or transceiver module). The transceiver unit is capable of both sending and receiving functions. When the transceiver unit performs the sending function, it may be called a sending unit (sometimes also called a sending module), and when it performs the receiving function, it may be called a receiving unit (sometimes also called a receiving module). The sending unit and the receiving unit may be the same functional module, referred to as the transceiver unit, which performs both sending and receiving functions; or, the sending unit and the receiving unit may be different functional modules, with the transceiver unit being a collective term for these functional modules.

[0026] For example, the device includes a processor coupled to a memory for executing instructions in the memory to implement the methods described in the first to third aspects and any possible implementations above. Optionally, the device may also include other components, such as an antenna, input / output modules, interfaces, etc. These components may be hardware, software, or a combination of both.

[0027] Fifthly, a computer-readable storage medium is provided for storing a computer program or instructions that, when executed, cause the methods of any one of the first to third aspects to be implemented.

[0028] A sixth aspect provides a computer program product containing instructions that, when run on a computer, enables the method described in any one of the first to third aspects to be implemented.

[0029] In a seventh aspect, a chip system is provided, comprising logic circuitry (or, as understood, a processor, which may include logic circuitry, etc.), and further comprising input / output interfaces. The input / output interfaces can be used to receive messages and to send messages. The input / output interfaces can be the same interface, i.e., the same interface can implement both sending and receiving functions; or, the input / output interface includes an input interface and an output interface, where the input interface is used to implement the receiving function, i.e., to receive messages; and the output interface is used to implement the sending function, i.e., to send messages. The logic circuitry can be used to perform operations other than the sending and receiving functions in the methods described in the first to third aspects and any possible implementations above; the logic circuitry can also be used to transmit messages to the input / output interfaces or to receive messages from other communication devices from the input / output interfaces. The chip system can be used to implement the methods described in the first to third aspects and any possible implementations above. The chip system can be composed of chips or can include chips and other discrete devices.

[0030] Optionally, the chip system may also include a memory, which can be used to store instructions, and the logic circuits can call the instructions stored in the memory to implement the corresponding functions.

[0031] Eighthly, a communication system is provided, which may include means for implementing the first aspect and any possible design thereof, means for implementing the second aspect and any possible design thereof, and means for implementing the third aspect and any possible design thereof. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating an application scenario according to an embodiment of this application;

[0033] Figure 2 This is a schematic diagram illustrating the working principle of RIS;

[0034] Figure 3 A flowchart illustrating a channel estimation method provided in an embodiment of this application;

[0035] Figure 4 A schematic diagram of the structure of a communication device provided in this application;

[0036] Figure 5 A schematic diagram of another communication device provided in this application;

[0037] Figure 6 A schematic diagram of another communication device provided in this application. Detailed Implementation

[0038] This application provides a channel estimation method and apparatus. The method and apparatus are based on the same inventive concept. Since the principles by which the method and apparatus solve problems are similar, their implementations can be mutually referenced, and repeated details will not be elaborated further. In the description of this application's embodiments, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship. In this application's embodiments, "at least one" refers to one or more; "multiple" refers to two or more. Furthermore, it should be understood that in the description of this application's embodiments, terms such as "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or order.

[0039] The channel estimation method provided in this application can be applied to fourth-generation (4G) communication systems, such as Long Term Evolution (LTE) systems, as well as fifth-generation (5G) communication systems, such as 5G New Radio (NR) systems, or to various future communication systems, such as sixth-generation (6G) systems. The method also applies to Bluetooth systems, Wireless Fidelity (Wi-Fi) systems, Long Range Radio (LoRa) systems, or vehicle-to-everything (V2X) systems. Furthermore, the method can be applied to satellite communication systems, where the satellite communication system can be integrated with the aforementioned communication systems.

[0040] For ease of understanding, Figure 1 The application scenario of this application embodiment is illustrated using the communication system architecture shown below. (See also...) Figure 1 As shown, the communication system includes network device 101 and terminal device 102. The apparatus provided in this embodiment can be applied to network device 101 or to terminal device 102. It is understood that... Figure 1 This application only illustrates one possible communication system architecture that can be applied to an embodiment of the present application. In other possible scenarios, the communication system architecture may also include other devices.

[0041] Network device 101 is a node in the radio access network (RAN), also known as a base station or RAN node (or device). Examples of current RAN devices include: next-generation base stations (gNodeB / gNB / NR-NB), transmission reception points (TRP), evolved Node Bs (eNB), radio network controllers (RNC), Node Bs (NB), base station controllers (BSC), base transceiver stations (BTS), home base stations (e.g., home evolved NodeB, or home Node B, HNB), base band units (BBU), wireless fidelity (Wi-Fi) access points (APs), satellite equipment, network devices in 5G communication systems, or network devices in future communication systems. Network device 101 can also be other devices with network device functions. For example, network device 101 can also be a device that performs network device functions in device-to-device (D2D) communication, vehicle-to-everything (V2X) communication, and machine-to-machine (M2M) communication. Network device 101 can also be a network device in a possible future communication system.

[0042] In some deployments, a gNB may include a centralized unit (CU) and a distributed unit (DU). A gNB may also include a radio unit (RU). The CU implements some of the gNB's functions, and the DU implements others. For example, the CU implements radio resource control (RRC) and packet data convergence protocol (PDCP) layer functions, while the DU implements radio link control (RLC), media access control (MAC), and physical (PHY) layer functions. Since RRC layer information ultimately becomes PHY layer information, or is derived from PHY layer information, in this architecture, higher-layer signaling, such as RRC or PDCP layer signaling, can also be considered as being sent by the DU, or by the DU+RU. It is understood that network devices can be CU nodes, DU nodes, or devices including both CU and DU nodes. Furthermore, the CU can be classified as a network device in the access network RAN ​​or as a network device in the core network CN; there is no restriction on this.

[0043] Terminal equipment 102, such as user equipment (UE), mobile station (MS), mobile terminal (MT), etc., is a device that provides voice or data connectivity to users, and can also be an Internet of Things (IoT) device. For example, terminal equipment includes handheld devices with wireless connectivity, vehicle-mounted devices, etc. Currently, terminal devices can be: mobile phones, tablets, laptops, PDAs, mobile internet devices (MIDs), wearable devices (such as smartwatches, smart bracelets, pedometers, etc.), in-vehicle devices (such as cars, bicycles, electric vehicles, airplanes, ships, trains, high-speed trains, etc.), virtual reality (VR) devices, augmented reality (AR) devices, wireless terminals in industrial control, smart home devices (such as refrigerators, televisions, air conditioners, electricity meters, etc.), intelligent robots, workshop equipment, wireless terminals in autonomous driving, wireless terminals in remote surgery, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, or wireless terminals in smart homes, and flying devices (such as intelligent robots, hot air balloons, drones, airplanes), etc. Terminal devices can also be other devices with terminal functions; for example, a terminal device can also be a device that performs terminal functions in D2D communication. In this application embodiment, terminal devices with wireless transceiver functions and chips that can be set in the aforementioned terminal devices are collectively referred to as terminal devices.

[0044] The following describes the technical terms that may be involved in the embodiments of this application.

[0045] In this article, X H This represents the conjugate transpose of X. `diag(X)` represents taking the diagonal matrix of X. `X(:,Y)` represents taking the Y column vectors of matrix X.

[0046] A reference signal, provided by the transmitter to the receiver, can be used for channel estimation or channel sounding. For example, a reference signal can also be called a pilot signal.

[0047] A Reconfigurable Artificial Electromagnetic Surface (RIS) is an artificial composite structure formed by a large number of subwavelength digitally reconfigurable artificial electromagnetic units (or reflective elements) arranged in a certain macroscopic pattern (periodic or aperiodic). Depending on the specific material of the reflective elements, RIS can be divided into antenna array-based structures and metamaterial-based structures. By adjusting the phase shift of all reflective elements, the reflected signal can be configured to propagate in the desired direction. Due to the rapid development of metamaterials, the reflection coefficient of each element can be configured in real time to adapt to dynamically fluctuating wireless propagation environments.

[0048] Because the basic units and arrangement of RIS can be arbitrarily designed, it can overcome the limitations of traditional materials that are difficult to manipulate precisely at the atomic or molecular level, and construct unconventional medium parameters that cannot be achieved by traditional materials and technologies, such as medium parameters that include both positive and negative permittivity. Materials with unconventional medium parameters can be called metamaterials or metamaterials. Since they are based on the characteristic of controlling electromagnetic waves by changing the spatial arrangement of digital coding units, that is, controlling the electromagnetic field at a specific spatial location by changing the state distribution of basic units, in some embodiments, metamaterials can also be called digital electromagnetic metamaterials or electromagnetically coded metamaterials.

[0049] RIS can be installed on large flat surfaces (such as indoor walls or ceilings, outdoor buildings or signs) to reflect radio frequency energy around obstacles and create a virtual line-of-sight propagation path between the communication source and the target.

[0050] For example, please see Figure 2 This is a schematic diagram illustrating the working principle of RIS. Figure 2 Taking a scenario where the communicating parties are a network device and a UE, and the process involves uplink transmission, as an example. Figure 2 As shown, after the signal emitted by the UE reaches the RIS, it will be reflected by the RIS's cell array (or cell, array, etc.), and the network device can receive the reflected signal from the RIS.

[0051] Assuming the network device has K antennas, the RIS has M element arrays, and the UE has a single antenna, the signal obtained by the network device after demodulating the received reference signal can be expressed as:

[0052] Y all =F H diag(W)H+H BS-UE (Formula 1)

[0053] Among them, F H Y represents the conjugate transpose of channel F between the network device and the RIS. all This represents the signal obtained after the network device demodulates the received reference signal. W represents the weights of the element arrays included in the RIS, and diag(W) represents diagonalization of matrix W. H represents the channel between the RIS and the UE. BS-UE This represents the channel between the network device and the UE. all The dimension is K×1, where K is the number of antennas of the network device. For methods of estimating the channel between the network device and the UE, please refer to existing technologies; they will not be elaborated upon here. This paper focuses on cascaded channels, namely, the channel between the network device and the RIS, and the channel between the RIS and the UE.

[0054] The cascaded channel can be obtained through two measurement processes, as follows:

[0055] First measurement procedure: With the RIS turned off, the RIS will no longer be working, and the channel H between the network device and the UE can be measured. BS-UE .

[0056] Second measurement process: RIS is activated. The RIS reflects the signal between the network device and the UE, allowing Y to be measured. all This leads to the concept of a cascaded channel. For example, the signal received by a network device through a cascaded channel can be represented as:

[0057] Y = Y all -H BS-UE =F H diag(W)H (Formula 2)

[0058] Where Y has a dimension of K×1. Y and Y all The difference is that Y all In addition to considering the cascaded channel, Y also considers the channel between the network device and the UE, while Y considers the cascaded channel but does not consider the channel between the network device and the UE.

[0059] Taking the conjugate transpose of Y, we get:

[0060] Y H =W H G (Formula 3)

[0061] Among them, Y H W represents the conjugate transpose of Y. H Let W denote the conjugate transpose, and G denote the cascaded channel, G = diag(H). H The dimensions of F and G are M×K.

[0062] If the UE sends T reference signals, then the T reference signals received by the network device can be represented as:

[0063]

[0064] in, The dimension is T×M. The dimension is T×K. W T The conjugate transpose of W T This represents the weights of the unit arrays in the RIS used to reflect the T reference signals.

[0065] Typically, cascaded channels can be obtained through the following relationship:

[0066]

[0067] in, This represents the estimated value of the cascaded channel. express The pseudo-inverse matrix. For Equation 5 to have a solution, T >= M is required. It is evident that when the number of unit elements included in RIS is too large, the overhead of the reference signal also increases accordingly.

[0068] Therefore, embodiments of this application provide a channel estimation method to reduce the reference signal overhead when performing channel estimation. In embodiments of this application, the cascaded channel is, for example, a sparse channel. In embodiments of this application, the terminal device can transmit two rounds of reference signals. In the first round, T1 reference signals are transmitted, where T1 is a positive integer greater than or equal to N and less than M. N unit arrays are a subset of the unit arrays included in the RIS, that is, N is less than the total number of unit arrays included in the RIS. Optionally, N can be much smaller than M. For example, the order of magnitude of N is a first order of magnitude, and the order of magnitude of M is a second order of magnitude, where the first order of magnitude is smaller than the second order of magnitude. For example, the first order of magnitude is "ten", meaning that the first subarray can include dozens of unit arrays, such as N = 40; the second order of magnitude is "thousand", meaning that the RIS can include thousands of unit arrays, such as M = 1024. Optionally, even if T1 is greater than the diameter of the angular domain, the order of magnitude of T1 can be the same as the order of magnitude of the diameter of the angular domain. In the second round, the terminal device can send T2 reference signals, where T2 is a positive integer greater than or equal to the diameter of the cascaded channel's angle domain and less than M. Generally, the diameter of the angle domain is much smaller than the number of element arrays included in the RIS; for example, the diameter of the angle domain is on the same order of magnitude as N, such as diameter = 20. Optionally, even if T2 is greater than the diameter of the angle domain, the order of magnitude of T2 can be the same as that of the diameter of the angle domain. Therefore, the number of reference signals sent by the terminal device can be less than (or even much less than) the total number of element arrays included in the RIS, thus saving reference signal overhead. Furthermore, since T1 is greater than or equal to N, the accuracy of the diameter of the cascaded channel's angle domain estimated based on T1 reference signals can be guaranteed, and the first codebook determined based on this diameter will also be more accurate, thereby improving the accuracy of the cascaded channel estimated based on T2 reference signals.

[0069] To better illustrate the embodiments of this application, the methods provided by the embodiments of this application are described below with reference to the accompanying drawings. In the various embodiments of this application, the terminal device is described using a UE as an example. The methods provided by the various embodiments of this application can be applied to... Figure 1 The network architecture shown. For example, the UE involved in the embodiments of this application is... Figure 1 Terminal device 102; the network device involved in the embodiments of this application is... Figure 1 Network device 101 in the embodiment of this application; the RIS involved in this application embodiment can be set in Figure 1 Between terminal device 102 and network device 101, for example, refer to Figure 2 .

[0070] Please refer to Figure 3 The above is a flowchart of a channel estimation method provided in an embodiment of this application.

[0071] S301, UE sends T1 reference signals. The UE sends T1 reference signals to the network device, but the RIS (Reference Information Set) is located between the UE and the network device and will receive T1 reference signals first.

[0072] This can also be understood as the UE sending T1 reference signals, where each transmitted reference signal can be considered a single reference signal. For example, the UE can send T1 reference signals at T1 time intervals, where one time interval can be a point in time, an orthogonal frequency division multiplexing (OFDM) symbol, or a time slot, etc.

[0073] The value of T1 may be predefined, such as by a protocol; or the value of T1 may be determined by the UE and the network device through negotiation before S301; or the value of T1 may be configured by the network device, for example, by the network device sending second information to the UE before S301 to indicate the value of T1.

[0074] S302, the first subarray of the RIS reflects T1 reference signals, and the corresponding network device receives the T1 reference signals reflected by the first subarray of the RIS.

[0075] A RIS can include M unit arrays, and the first subarray can include N unit arrays from the M unit arrays, where M is a positive integer and N is a positive integer less than M. For example, the N unit arrays can be consecutive unit arrays, which will not reduce the resolution of the RIS; or, at least two unit arrays among the N unit arrays can be non-consecutive. For example, if the spacing between adjacent unit arrays in the RIS is small, the coupling between unit arrays may be too large. In this case, the first subarray can include non-consecutive unit arrays to reduce the resolution of the first subarray.

[0076] In other words, the RIS can reflect T1 reference signals using only a portion of the cell array, instead of using all the cell arrays, thus reducing the RIS's power consumption. Here, T1 can be a positive integer greater than or equal to N, for example, T1 is also less than M, therefore the overhead of the UE transmitting T1 reference signals is relatively small. For example, N can be much smaller than M, for example, M is on the order of thousands, and N is on the order of hundreds or tens, thereby significantly saving the transmission overhead of the reference signals.

[0077] As described in S301, the network device can send a second message to the UE to indicate the value of T1. Alternatively, the second message can indicate the value of N instead of the value of T1. After receiving the second message, the UE can determine the value of T1 based on the value of N, for example, by setting T1 to a positive integer greater than or equal to N.

[0078] If the RIS needs to reflect T1 reference signals using the first subarray, the RIS must first determine the first subarray. Optionally, the first subarray can be pre-determined by the RIS and the network device, for example, by negotiation before S302; or, the first subarray can be predefined by the protocol; or, the first subarray can be determined by the network device. If the first subarray is determined by the network device, the network device can send fourth information to the RIS before S302, which can indicate the first subarray. For example, the fourth information indicates (or includes) one or more of the following: the value of N, the number of rows of the N cell array (or, the number of rows of the first subarray), or, the number of columns of the N cell array (or, the number of columns of the first subarray). Essentially, the fourth information indicates the first subarray by indicating its parameters, and the RIS can determine the first subarray based on the fourth information.

[0079] In this system, RIS uses the first subarray, and the weights of the first subarray are changed once for each reference signal reflected. For example, RID can use the Discrete Fourier Transform (DFT) to determine the weights, or it can use Hadamard weights.

[0080] S303. The network device estimates the path of the angular domain of the concatenated channel based on T1 reference signals, and determines the first codebook based on the path of the angular domain. The concatenated channel includes the channel between the network device and the RIS, and the channel between the RIS and the UE. For example, embodiments of this application can be applied to time division duplex (TDD) systems. In TDD systems, uplink and downlink channels have corresponding characteristics; therefore, the concatenated channel can be either an uplink channel or a downlink channel.

[0081] Optionally, the network device can use a compressed sensing algorithm to estimate the angular domain path of the concatenated channel based on T1 reference signals. Alternatively, the network device can use other algorithms to estimate the angular domain path of the concatenated channel based on T1 reference signals, such as statistical algorithms, etc., without any specific restrictions.

[0082] For example, the radius of the cascaded channel in the angular domain can be denoted by L. Taking the network device's use of compressed sensing algorithms to determine L as an example, the network device can use compressed sensing algorithms such as orthogonal matching pursuit (OMP), subspace pursuit (SP), or compressed sampling matching pursuit (CoSaMP) to determine L. Alternatively, the network device can also use an improved OMP algorithm (such as multi-step OMP) to determine L.

[0083] The OMP algorithm is briefly introduced below. For example, for a linear system of equations Ax = b, if each column of matrix A is considered a variable, the OMP algorithm selects the variable with the highest correlation to the current residual in each iteration. After each iteration, the residual used to evaluate the correlation of the variables can be obtained from the previous iteration, and each iteration can yield the residual used in the next iteration. The residual of one iteration can be obtained by calculating the difference between b and its orthogonal projection onto a subspace of matrix A. This subspace consists of the variables selected in each iteration; for example, each iteration adds the selected variable to this subspace. One iteration yields one variable, and the number of iterations depends on the required number of variables; for example, if 30 variables are needed, 30 iterations are required.

[0084] In other words, if x has no zero elements, then b should belong to the column vector space Span(A) of matrix A. However, since x has many zero elements, b should belong to a subspace of Span(A) (where belonging to a subspace also belongs to the entire space of Span(A)). For example, let Span(A) denote the subspace of Span(A) to which b belongs. sub ), where A sub This includes one or more column vectors of matrix A, and the corresponding x is denoted as xi. sub If we can obtain A sub and x sub This allows us to solve the following optimization problem:

[0085]

[0086] Here, argmin f(x) represents the value of the variable that minimizes the objective function f(x). Let X represent the second normal form of matrix X.

[0087] The steps of the OMP algorithm are as follows.

[0088] S11. Input matrices A and b, and the number of variables to be selected Q. Initialize the residual r0 = b, the orthogonal projection matrix P0 = 0, and the subspace index set. The restored signal is x = 0. Where, This indicates the empty set, meaning that the set S is initially empty.

[0089] S12, Calculate i = argmax i |A i H r k |, let i be placed into set S, i.e., S = S∪{i}. Here, ∪ represents the union of sets, and i represents the index of the variable selected from matrix A in one iteration. A i Let r represent the column vector in matrix A that has the largest residual. k This represents the residual of the k-th cycle (or iteration).

[0090] S13, Calculate P k =A S (A S H A S ) -1 A S H r k =(IP k b. Among them, P k Let A represent the projection of the variable selected in the k-th iteration onto the subspace of matrix A. S Let I represent the set of column vectors that maximize the residual from matrix A after each k-th iteration (or cycle). I denotes the identity matrix.

[0091] S14. Repeat steps 2 and 3 Q times.

[0092] S15, Calculate x s =(A S H A S ) -1 A S H b, x s The value of x represents the position indicated by the element included in set S.

[0093] S16, Return x s .

[0094] After A iterations (or loops) have completed, A S =A sub x S =x sub .

[0095] In this embodiment of the application, A = D r Or A = W H D r In other words, matrix A can be viewed as a dictionary matrix. k =Res t Regarding Res t This will be discussed later. x = G. This represents the T reference signals Y received by the network device. T The conjugate transpose of , where G represents the cascaded channel. And, regarding D... r W H D r This will be discussed later.

[0096] The residual of each iteration can be determined as follows:

[0097]

[0098] L t =L t-1 ∩i (Formula 8)

[0099]

[0100]

[0101] Among them, L t-1 ∩i represents L t-1 The intersection with i. D r (:,i) indicates taking matrix D r The i-th column vector, D r (:,i) H D represents r The conjugate transpose of (:,i). argmax f(x) represents the variable value that maximizes the objective function f(x). Res represents the residual, where Res0 represents the initial residual (e.g., b), and Res... t-1 Res represents the residual obtained in the (t-1)th iteration (or t-th cycle) of the process. t L represents the residual obtained in the t-th iteration (or loop). t-1 L represents the set of indices in the dictionary matrix of the paths in the angle domain determined during the (t-1)th loop (or iteration). t This represents the set of indices in the dictionary matrix of the path of the angle domain determined during the t-th loop (or iteration).

[0102] As can be seen from the above steps, the OMP algorithm selects one variable and places it into a subspace in each iteration, thus ensuring that the selected variable is the optimal solution in each iteration. However, if two variables are correlated, then the two variables combined may not be two globally optimal solutions. For example, referring to Table 1, we can see that the OMP algorithm focuses on the current optimal solution in each iteration, but not on the globally optimal solution. Therefore, the variable ultimately selected may not be the globally optimal variable, which makes the OMP algorithm prone to local optima. In Table 1, "index" represents the index of the column vector in matrix A.

[0103] Table 1

[0104]

[0105] Therefore, embodiments of this application can employ the multi-step-OMP algorithm to determine the radius L in the angle domain. The steps of the multi-step-OMP algorithm are as follows.

[0106] S21. Input matrices A and b, and the sparsity Q of matrix b. Initialize the residual r0 = b, the orthogonal projection matrix P0 = 0, and the subspace index set. The restored signal x = 0, and the threshold ε for residual convergence. Wherein, This indicates the empty set, meaning that the set S is initially empty.

[0107] S22. Calculate P = argmax P |A P H r k | We insert set P into set S, i.e., S = S∪{P}. Set P is the set of indices of the P variables selected from matrix A in one iteration. The P variables are the P variables with the highest correlation to the current residual in one iteration, and P is a positive integer, for example, P can be greater than or equal to 2. It can be seen that in the multi-step-OMP algorithm, multiple variables can be selected in each iteration, thereby increasing the probability of obtaining the global optimum. Specifically, when P = Q, the multi-step-OMP algorithm can be considered as the SP algorithm; when Q = 2P, the multi-step-OMP algorithm can be considered as the CoSaMP algorithm.

[0108] A P Let r represent the set of P column vectors in matrix A that have the largest residuals. k This represents the residual of the k-th cycle (or iteration).

[0109] S23, Calculate P k =A S (A SH A S ) -1 A S H r k =(IP k b. I represents the identity matrix. A S P represents the set of column vectors that maximize the residual from matrix A after each k-th cycle (or iteration). k This represents the projection of the variable selected in the k-th iteration onto the subspace of matrix A.

[0110] S24. Repeat steps 2 and 3 until the set S contains an element equal to Q+P.

[0111] S25. Calculate Q = argmax K |A S H b|, that is, determine the Q elements in set S whose projection onto matrix b is the largest among the Q+P elements in set S, let S = {Q}. And, calculate P k =A S (A S H A S ) -1 A S H r k =(IP k )b.

[0112] S25 removes elements from set S with small projections onto matrix b. These removed elements may include correlated elements from set S. Specifically, in the beam domain of a channel, when multiple paths are clustered together (e.g., in the angular domain of a channel, path clusters are close together, and it's difficult to distinguish each path individually), the concentrated energy of these paths may generate sidelobes on variables corresponding to other indices within set S. When using the OMP algorithm, if a sidelobe is generated on a variable, its projection onto matrix b increases, leading to a misjudgment that the variable corresponding to that index is also a path, and that index is considered a correlated element in set S. Therefore, in this embodiment, when using the multi-step-OMP algorithm, correlated elements are removed, effectively eliminating misjudged paths and making the result closer to the true paths in the angular domain.

[0113] Therefore, by employing the multi-step-OMP algorithm, which selects more variables in each iteration and removes correlated elements, we can minimize the possibility of local optima and increase the probability of obtaining the global optimum.

[0114] S26. Repeat steps 2, 3, 4, and 5 until |r k -r k-1 |<ε.

[0115] S27, Calculate x s =(A S H A S ) -1 A S H b. x s This represents the value of the element at position S in x.

[0116] S28, Return x s .

[0117] In this embodiment of the application, A = D r Or A = W H Dr,r k =Res t , x = G. For details on how to calculate the residuals, please refer to the previous text.

[0118] Once the network device obtains the radius L of the angle domain, it can determine the first codebook based on the radius L. The first codebook may include at least one weight, for example, a row vector or a column vector in the first codebook may be a weight. Each of the at least one weight is a weight of the E unit arrays included in the RIS, where E is a positive integer less than or equal to M. That is, each weight may be a weight of the M unit arrays included in the RIS, or it may be a weight of a subset of the unit arrays included in the RIS. If the E unit arrays are a subset of the unit arrays included in the RIS, for example, the E unit arrays are unit arrays included in the first subarray, then E = N; or, the E unit arrays and the N unit arrays are different unit arrays, or the E unit arrays and the N unit arrays may have intersection but are not completely identical. In both cases, E may be equal to N or not equal to N.

[0119] When the RIS reflects a reference signal, it can weight the reference signal according to the weights included in the first codebook. For example, for each reference signal reflected by the RIS, the reference signal is weighted according to a weight included in the first codebook, or in other words, the dictionary matrix in the angle domain is weighted, resulting in a new matrix. If the new matrix is ​​not orthogonal to the path in the angle domain, residuals will occur, thereby reducing the accuracy of the channel estimation result. Therefore, in the embodiments of this application, the new matrix obtained according to each weight included in the first codebook can be orthogonal to the path in the angle domain to improve the accuracy of the channel estimation result.

[0120] For example, the angular domain of a cascaded channel can be represented as:

[0121] G angle =D r H G (Formula 11)

[0122] Among them, G angle G represents the angle domain matrix of the cascaded channel. angle The dimension is M×K. D r D represents the original dictionary matrix in the angle domain. r H D represents r The conjugate transpose of D. r It can be represented as:

[0123]

[0124] in, For example, X can be replaced with N, and θ can be replaced with Or replace with Etc., that is, here is given the formula 12. The calculation method of the formula. d represents the physical distance between adjacent unit arrays included in the RIS, and λ represents the wavelength of the RIS's operating frequency band. φ0 represents D r The first angle of the matrix, φ R D represents r The R-th angle of the matrix. R represents the resolution of the angle domain. f(φ) is, for example, sin(φ), or cos(φ), or cos(a)sin(φ), or sin(a)cos(φ), etc. Where f(φ) is cos(a)sin(φ) or sin(a)cos(φ), it indicates that the structure of RIS is a two-dimensional planar structure. In this case, φ can represent the horizontal angle and a can represent the vertical angle; or, φ can represent the vertical angle and a can represent the horizontal angle. Optionally, D r The dimension of D can be related to the first subarray. For example, if the first subarray is a linear array, then D... r The dimension can be N×R. For example, the first subarray is a planar array, such as... At this time, D r The dimension can be pq×R 2 Among them, D rH D represents a row matrix. rV D represents a column matrix. rH The dimension is p×R, D rV The dimension is q×R, where p×q is the dimension of the first subarray, that is, p is the number of rows of the unit arrays included in the first subarray, and q is the number of columns of the unit arrays included in the first subarray. This indicates the calculation of the Kronecker product of a and b.

[0125] In addition, cascaded channels can be restored using the following relationship:

[0126] G=D r G angle =D r D r H G = IG = G (Formula 13)

[0127] Here, I represents the identity matrix. It can be seen that the cascaded channel in the angular domain can be compressed using compressed sensing methods, such as the following compression method:

[0128]

[0129] Among them, D r (:,L) indicates taking D r L column vectors in D r The dimension of (:,L) is M×L. This represents the estimated value in the angular domain of the cascaded channel. The dimension is L×K. L represents the diameter of the cascaded channel in the angular domain.

[0130] If we take D in formula 14 r Replace with W H D r Then, it can be represented as a new matrix obtained by a single weighting, for example, Equation 14 is transformed as follows:

[0131]

[0132] Since the construction of the dictionary matrix for the angle domain is similar to that of the DFT matrix, and each column of the dictionary matrix is ​​mutually orthogonal, comparing formulas 14 and 15, it can be seen that if the new matrix obtained after weighting is still a dictionary matrix, it can be guaranteed that the new matrix is ​​still orthogonal to the radius of the angle domain. Therefore, the first codebook in this embodiment can satisfy the following relationship:

[0133]

[0134] Among them, W Dr Represents the first codebook, D represents the new dictionary matrix in the angle field obtained from the first codebook. r Let L represent the original dictionary matrix of the angle domain, and D represent the radius of the angle domain. r (:,L) -1 D represents r The inverse of (:,L).

[0135] Optionally, each weight in the first codebook can be the weight of the E unit arrays included in the RIS, where E can be a positive integer less than or equal to M. For example, the first codebook represented by Equation 16 has a dimension of M×T2, where T2 is the number of reference signals reflected by the RIS according to the first codebook. That is, the first codebook represented by Equation 16 corresponds to E=M. If the RIS uses this first codebook, then the RIS uses all unit arrays to reflect T2 reference signals.

[0136] Alternatively, if E is less than M, then the weights included in the first codebook can also be the weights of some of the M unit arrays. That is, RIS may also use some unit arrays to reflect T2 reference signals. In this case, the first codebook can satisfy the following relationship:

[0137]

[0138] Among them, W Dr_sub The first codebook corresponding to E unit elements can be understood as W Dr_sub It includes one or more weights, each of which is the weight of E unit arrays. Dr_sub represents the new dictionary matrix of angle fields obtained from the first codebook, and Dr_sub represents the dictionary matrix of angle fields with E unit elements, having a dimension of E×L, where L represents the diameter of the angle field. sub (:,L) -1 Dr sub The inverse of (:,L).

[0139] S304. The network device sends third information to the RIS. Correspondingly, the RIS receives the third information from the network device.

[0140] The third information can indicate the first codebook. The third information can indicate the first codebook in different ways. For example, the third information can include the first codebook; in this case, the RIS can directly obtain the first codebook after receiving the third information, without needing to perform excessive processing, making the implementation relatively simple.

[0141] Alternatively, the third information may include L indices, which are the original dictionary matrix (e.g., D) of the angular field's diameter in the angular field. r The indexes in ) are used by RIS based on these L indexes and D. rThe first codebook can then be obtained. For example, if the RIS stores one or more dictionary matrices, and receives L indices, the RIS can determine the corresponding L column vectors in one or more stored dictionary matrices based on these L indices, and then determine the first codebook according to some algorithms, such as formula (17). Wherein, if the RIS stores only one dictionary matrix, the number of rows of the dictionary matrix can be greater than or equal to the total number M of the unit arrays included in the RIS. Compared with the first codebook, the information content of L indices is relatively small. By indicating the first codebook by indicating L indices, the transmission overhead of the third information can be reduced.

[0142] S305, UE sends T2 reference signals. The UE sends T2 reference signals to the network device, but the RIS (Reference Information Set) is located between the UE and the network device and will receive the T2 reference signals first.

[0143] This can also be understood as the UE sending T2 reference signals, where each transmitted reference signal can be considered a single reference signal. For example, the UE can send T2 reference signals at T2 time intervals, where one of the time intervals can be a point in time, an OFDM symbol, or a time slot, etc.

[0144] For example, T2 is a positive integer greater than or equal to the diameter L of the angle domain. Since the diameter of the angle domain is determined by the network device, the network device can indicate the value of T2 to the UE. Optionally, prior to S305, the network device can also send first information to the UE, which can indicate the value of T2, allowing the UE to determine the value of T2. Alternatively, the first information can indicate the diameter of the angle domain, allowing the UE to select a positive integer greater than or equal to the diameter of that angle domain as T2.

[0145] S306, the E element arrays of RIS reflect T2 reference signals, and correspondingly, the network device receives the T2 reference signals reflected by the E element arrays. Here, E can be equal to M, or it can be less than M.

[0146] If the RIS needs to reflect T2 reference signals using E cell arrays, the RIS must first determine the E cell arrays. Optionally, the E cell arrays can be pre-determined by the RIS and the network device, for example, by negotiation before S302; or, the E cell arrays can be predefined by the protocol; or, the E cell arrays can be determined by the network device; or, the E cell arrays can be determined by the RIS. If the E cell arrays are determined by the network device, the network device can send fifth information to the RIS before S306, which can indicate the E cell arrays. For example, the fifth information indicates (or includes) one or more of the following: the value of E, the number of rows of the E cell arrays, or the number of columns of the E cell arrays. Essentially, the fifth information indicates the E cell arrays by indicating the parameters of the E cell arrays, and the RIS can determine the E cell arrays based on the fifth information. Optionally, the E cell arrays are consecutive cell arrays.

[0147] The RIS uses E element arrays, and changes the weights of these E element arrays each time a reference signal is reflected. For example, the RIS can use a first codebook to determine the weights. The first codebook includes at least one weight; for example, the number of weights in the first codebook can be greater than or equal to T2. The RIS can then select one weight from the first codebook each time a reference signal is reflected. For instance, if the weights in the first codebook are arranged in chronological order, the RIS can select the corresponding weights from the first codebook sequentially according to the chronological order.

[0148] S307. The network device estimates the cascaded channel based on T2 reference signals.

[0149] For example, network devices can estimate cascaded channels in the following way:

[0150]

[0151] in, This represents the estimated value of the cascaded channel. W Dr The conjugate transpose of D. r (:,L) indicates taking matrix D r Column L in the text.

[0152] If E = M, that is, the E unit dipoles are all the unit dipoles of the RIS, the network device estimates the complete cascaded channel. Or, if E < M, that is, the E unit dipoles are partial unit dipoles of the RIS, what the network device estimates may be a sub-matrix of the cascaded channel. If this is the case, the network device can take further measures to obtain the complete cascaded channel. For example, the network device can use an algorithm for parameter estimation for the channel corresponding to the E unit dipoles, such as the multiple signal classification (MUSIC) algorithm or the estimating signal parameters via rotational invariance techniques (ESPRIT) algorithm, etc., to estimate the small-scale coefficients and the information in the angular domain of this channel, and then use the channel model of the cluster delay line (CDL) to restore this channel to obtain the cascaded channel.

[0153] The embodiment of the present application adopts two estimation processes. The first time is to estimate the paths in the angular domain of the cascaded channel by using the first sub-array and a small number of reference signals. The network device designs the RIS weights applied to the secondary estimation process by using the estimated paths in the angular domain and transmits them to the RIS. The second time is to estimate the cascaded channel by using the designed RIS weights. Generally speaking, the number of paths in the angular domain is much smaller than the number of unit dipoles included in the RIS (for example, in the case of high frequency, the number of unit dipoles currently included in the RIS is generally about 1000, while the paths in the angular domain are generally sparse, possibly less than 20), and the weights included in the designed first codebook will not destroy the orthogonality with the angular domain of the cascaded channel. Therefore, the solution provided by the embodiment of the present application can greatly reduce the overhead of the uplink reference signal and improve the accuracy of channel estimation.

[0154] The following introduces a simulation process to reflect the effects brought by the embodiment of the present application. This simulation process adopts the 3rd generation partnership project (3GPP) - cluster delay line type A model (CDL-A).

[0155] In this simulation process, in order to construct a sparse channel, part of the paths are intercepted to construct this sparse channel, and the parameters of this sparse channel can be referred to Table 2.

[0156] Table 2

[0157]

[0158]

[0159] In Table 2, the channel model parameter 3GPP 38.901, CDL-A, indicates that the CDL-A channel model defined by the 3GPP protocol version number 38.901 is used. The value corresponding to the UE antenna configuration (e.g., "1" in Table 2) refers to the number of UE antennas. In Case 1, the base station antenna configuration is "32:(U1,U2)=(32,1);(dH,dV)=(0.5,0.5)λ", where U1 represents the number of horizontal antennas of the base station, U2 represents the number of vertical antennas of the base station, (U1,U2)=(32,1) means there are 32 horizontal antennas and one vertical antenna, and the total number of antennas is U1*U2. The "32" before the colon indicates the total number of antennas. The explanations for the base station antenna configuration in Case 2, and the RIS antenna configuration in Case 1 and Case 2 are similar. dH represents the horizontal element spacing of the antenna, dV represents the vertical element spacing of the antenna, and λ represents the wavelength. (dH,dV)=(0.5,0.5)λ, indicating that the horizontal and vertical element spacing of the antenna are both 0.5 wavelengths.

[0160] Please refer to Table 3 for the parameters of the CDL-A channel model.

[0161] Table 3

[0162]

[0163]

[0164] Among them, C ASD C represents the extended parameter for the departure angle. ASA C represents the arrival angle extension parameter. ZSD C represents the zenith angle of departure. ZSA XPR represents the zenith angle reached, and XPR represents the cross-polarization power ratio of the antenna.

[0165] In Table 3 above, the content in square brackets (e.g., []) indicates the unit of the parameter.

[0166] The metric used in this simulation is the normalized mean square error. Where F represents the mean, G k This represents the actual concatenated channel corresponding to the k-th UE. This represents the estimated value of the cascaded channel corresponding to the k-th UE.

[0167] Simulation scheme:

[0168] Option 1: Adopt the channel estimation process provided in the embodiments of this application. Use the full array of RIS and traditional OMP to estimate L based on T1 reference signals; use the constructed WDr The cascaded channel is estimated based on T2 reference signals.

[0169] Option 2: Employ the channel estimation process provided in the embodiments of this application. Use a RIS subarray and traditional OMP to estimate L based on T1 reference signals; use the constructed W... Dr The cascaded channel is estimated based on T2 reference signals.

[0170] Option 3: Employ the channel estimation process provided in the embodiments of this application. Use a RIS subarray and multi-step-OMP to estimate L based on T1 reference signals; use the constructed W Dr The cascaded channel is estimated based on T2 reference signals.

[0171] Option 4: Adopt the current channel estimation scheme (the technical scheme provided in existing literature). The UE sends T reference signals, and the RIS uses random DFT weights to estimate the channel based on the full array of the RIS and traditional OMP.

[0172] Option 5: Using the current channel estimation scheme, the UE sends T reference signals, and the RIS uses random Hada code weights to estimate the channel based on the full array of the RIS and traditional OMP.

[0173] To ensure fairness, the number of reference signals T1+T2 in each of Schemes 1 to 3 is equal to the number of reference signals T in each of Schemes 4 and 5.

[0174] The simulation results can be found in Tables 4 to 7 below.

[0175] Table 4

[0176]

[0177]

[0178] Table 4 shows a comparison of NMSE for different technical solutions in Case 1 (refer to Table 2) when the number of reference signals in a sparse channel is equal. The values ​​in Table 4 (e.g., 0.03, 0.82, etc.) represent NMSE.

[0179] Table 5

[0180]

[0181] Table 5 shows a comparison of NMSE for different technical solutions in Case 2 (refer to Table 2) when the number of reference signals in a sparse channel is equal. The values ​​in Table 5 (e.g., 0.083, 0.41, etc.) represent NMSE.

[0182] Table 6

[0183]

[0184] Table 6 shows a comparison of the number of reference signals required by different technical solutions for case 1 (refer to Table 2) when the NMSE of the sparse channel is equal. The value of T in Table 6 represents the number of reference signals. For the technical solutions of this application embodiment, the number of T refers to the sum of T1 and T2.

[0185] Table 7

[0186]

[0187] Table 7 shows a comparison of the number of reference signals required by different technical solutions for case 2 (refer to Table 2) when the NMSE of the sparse channel is equal. The value of T in Table 7 represents the number of reference signals. For the technical solutions of this application embodiment, the number of T refers to the sum of T1 and T2.

[0188] The simulation results above show that:

[0189] (1) Existing channel estimation schemes using DFT or Hada code weights are unstable when the number of reference signals is small, and require a lot of time to search for better weights, resulting in low efficiency.

[0190] (2) When the number of reference signals used is equal, the NMSE of the channel estimation scheme provided in this application embodiment is less than 50% of that of the existing scheme.

[0191] (3) Under the same error (e.g. the same NMSE), the channel estimation scheme provided in this application embodiment reduces pilot overhead by at least 50% compared to existing schemes.

[0192] It is understood that, in order to achieve the functions described in the above embodiments, this application also provides a communication device. This communication device may include hardware structures and / or software modules corresponding to the execution of various functions. Those skilled in the art should readily recognize that, based on the units and method steps of the various examples described in conjunction with the embodiments disclosed in this application, this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed by hardware or by computer software driving hardware depends on the specific application scenario and design constraints of the technical solution.

[0193] Figures 4 to 6 This is a schematic diagram of a possible communication device provided for embodiments of this application. This communication device can be used to implement the functions of the RIS, network device, or UE in the above method embodiments, and therefore can also achieve the beneficial effects of the above method embodiments. In one possible implementation, the communication device can be as follows: Figure 1 or Figure 2 The network device or UE shown can also be as follows: Figure 2 The RIS shown can also be a module (such as a chip) applied to a UE, network device, or RIS. For related details and effects, please refer to the description of the foregoing embodiments.

[0194] like Figure 4 As shown, the communication device 400 includes a processing unit 410 and a communication unit 420, wherein the communication unit 420 may also be a transceiver unit or an input / output interface, etc. The communication device 400 can be used to implement the above-mentioned... Figure 3 The illustrated method embodiments demonstrate the functions of the RIS, network device, or terminal device.

[0195] For example, when the communication device 400 is used to implement Figure 3 In the illustrated method embodiment, when the RIS functions, the communication unit 420 is used to send T1 reference signals reflected from the first subarray of the RIS to the network device. The RIS includes M unit arrays, and the first subarray includes N unit arrays from the M unit arrays, where M is a positive integer, N is a positive integer less than M, and T1 is a positive integer greater than or equal to N and less than M. The communication unit 420 is also used to receive third information from the network device, the third information indicating a first codebook, the first codebook including at least one weight, the at least one weight being the weight of the plurality of unit arrays. The first codebook is determined based on the T1 reference signals; the communication unit 420 is further configured to transmit T2 reference signals reflected to the network device by E unit elements from the M unit elements, the T2 reference signals being used to estimate the cascaded channel, wherein the T2 reference signals are processed based on the first codebook, T2 is a positive integer greater than or equal to the diameter of the angular domain of the cascaded channel and less than M, the cascaded channel including the channel between the network device and the RIS, and the channel including the channel between the RIS and the terminal device, and E is a positive integer less than or equal to M.

[0196] When the communication device 400 is used to implement Figure 3In the method embodiment shown, the network device functions as follows: a communication unit 420 is used to receive T1 reference signals from a UE reflected by a first subarray of a RIS, wherein the RIS comprises M element subarrays, the first subarray comprises N element subarrays from the M element subarrays, M is a positive integer, N is a positive integer less than M, and T1 is a positive integer greater than or equal to N and less than M; a processing unit 410 is used to estimate the path of the angular domain of the concatenated channel based on the T1 reference signals, and determine a first codebook based on the path of the angular domain, wherein the first codebook includes at least one weight, the at least one weight being the weight of E element subarrays from the M element subarrays, and the concatenated channel packet The communication unit 420 includes a channel between the network device and the RIS, and a channel between the RIS and the UE, where E is a positive integer less than or equal to M; the communication unit 420 is further configured to send third information to the RIS, the third information being used to indicate the first codebook, the first codebook being used by the RIS to reflect reference signals; the communication unit 420 is further configured to receive T2 reference signals from the UE reflected by the E unit elements, wherein the T2 reference signals are processed according to the first codebook, and T2 is a positive integer greater than or equal to the diameter of the angular domain and less than M; the processing unit 410 is further configured to estimate the cascaded channel based on the T2 reference signals.

[0197] When the communication device 400 is used to implement Figure 3 In the illustrated method embodiment, the UE functions as follows: Communication unit 420 is configured to send T1 reference signals, which are reflected to the network device via a RIS, where T1 is a positive integer less than M, and M is the number of element arrays included in the RIS; Communication unit 420 is also configured to receive first information from the network device, which indicates the value of T2, where T2 is a positive integer less than M; Communication unit 420 is also configured to send T2 reference signals, which are reflected to the network device via the RIS, and the T2 reference signals are used to estimate a concatenated channel, which includes a channel between the network device and the RIS, and a channel between the RIS and the UE.

[0198] The terms and definitions used in the above device embodiments can be found in the descriptions of the foregoing method embodiments, and will not be elaborated here.

[0199] The module division in this embodiment is illustrative and represents only one logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional modules in each embodiment of this application can be integrated into a single processor, exist as separate physical entities, or be integrated into a single module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0200] like Figure 5 The diagram shows a communication device 500 provided in an embodiment of this application, used to implement the channel estimation method provided in this application. The communication device 500 can be a communication device applying the channel estimation method, a component within a communication device, or a device compatible with a communication device. The communication device 500 can be a RIS, a network device, or a UE. The communication device 500 can be a chip system or a chip. In this embodiment, the chip system can be composed of chips or may include chips and other discrete devices. The communication device 500 includes at least one processor 520, used to implement the channel estimation method provided in this embodiment. The communication device 500 may also include an output interface 510, which can also be called an input / output interface. In this embodiment, the output interface 510 can be used to communicate with other devices via a transmission medium, and its functions may include sending and / or receiving. For example, when the communication device 500 is a chip, it transmits data with other chips or devices through the output interface 510. The processor 520 can be used to implement the method provided in the above-described method embodiments.

[0201] For example, processor 520 can be used to perform actions performed by processing unit 410, and output interface 510 can be used to perform actions performed by communication unit 420, which will not be described in detail here.

[0202] Optionally, the communication device 500 may further include at least one memory 530 for storing program instructions and / or data. The memory 530 is coupled to the processor 520. The coupling in this embodiment is an indirect coupling or communication connection between devices, units, or modules, and can be electrical, mechanical, or other forms, for information exchange between devices, units, or modules. The processor 520 may operate in conjunction with the memory 530. The processor 520 may execute program instructions stored in the memory 530. At least one of the at least one memory may be integrated with the processor.

[0203] In this embodiment, the memory 530 can be non-volatile memory, such as a hard disk drive (HDD) or a solid-state drive (SSD), or it can be volatile memory, such as random-access memory (RAM). Memory is any other medium capable of carrying or storing desired program code in the form of instructions or data structures, and accessible by a computer, but is not limited thereto. The memory in this embodiment can also be a circuit or any other device capable of implementing storage functions, used to store program instructions and / or data.

[0204] In the embodiments of this application, the processor 520 may be a general-purpose processor, a digital signal processor, an application-specific integrated circuit, a field-programmable gate array or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component, capable of implementing or executing the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor may be a microprocessor or any conventional processor, etc. The steps of the methods disclosed in the embodiments of this application can be directly manifested as being executed by a hardware processor, or being executed by a combination of hardware and software modules in the processor.

[0205] like Figure 6 The diagram shows a communication device 600 provided in an embodiment of this application, used to implement the channel estimation method provided in this application. The communication device 600 can be a communication device applying the channel estimation method shown in the embodiments of this application, a component within the communication device, or a device compatible with the communication device. The communication device 600 can be a RIS, a network device, or a UE. The communication device 600 can be a chip system or a chip. In this embodiment, the chip system can be composed of chips or may include chips and other discrete devices. Part or all of the channel estimation method provided in the above embodiments can be implemented in hardware or software. When implemented in hardware, the communication device 600 may include an input interface circuit 601, a logic circuit 602, and an output interface circuit 603.

[0206] Optionally, taking the device as an example of implementing the function of the receiving end, the input interface circuit 601 can be used to perform the receiving action performed by the communication unit 420, the output interface circuit 603 can be used to perform the sending action performed by the communication unit 420, and the logic circuit 602 can be used to perform the action performed by the processing unit 410, which will not be described in detail here.

[0207] Optionally, the communication device 600 may be a chip or an integrated circuit in its specific implementation.

[0208] Some or all of the operations and functions performed by the communication device described in the above method embodiments of this application can be implemented using chips or integrated circuits.

[0209] This application provides a computer-readable storage medium storing a computer program, the computer program including instructions for performing the above-described method embodiments.

[0210] This application provides a computer program product containing instructions that, when run on a computer, cause the computer to execute the above-described method embodiments.

[0211] This application provides a communication system. Specifically, the communication system may include components for implementing... Figure 3The method described herein requires at least two of the following: a network device, a RIS (Reference Equipment), or a UE (User Equipment). Please refer to the relevant descriptions in the above method embodiments for details; they will not be repeated here.

[0212] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0213] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0214] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0215] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0216] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0217] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this application without departing from the embodiments and scope of this application. Therefore, if these modifications and variations to the embodiments of this application fall within the scope of the claims of this application and their equivalents, this application also intends to include these modifications and variations.

Claims

1. A channel estimation method, characterized in that, The method includes: T1 reference signals are sent, and the T1 reference signals are reflected to the network device through the reconfigurable smart surface RIS, where T1 is a positive integer less than M, and M is the number of unit arrays included in the RIS; Receive first information from the network device, the first information being used to indicate the value of T2, where T2 is a positive integer less than M; T2 reference signals are sent, which are reflected back to the network device via the RIS. The T2 reference signals are used to estimate the cascaded channel, which includes the channel between the network device and the RIS, and the channel between the RIS and the terminal device.

2. The method according to claim 1, characterized in that, The value of T1 is predefined; or, The method further includes: receiving second information from the network device, the second information being used to indicate the value of T1, or to indicate the value of N, where N is the number of unit array subarrays included in the first subarray of the RIS, the first subarray being used to reflect the T1 reference signals, wherein T1 is a positive integer greater than or equal to N and less than M.

3. A channel estimation method, characterized in that, The method includes: Receive T1 reference signals from the terminal device reflected by the first subarray of the RIS, wherein the RIS comprises M unit arrays, the first subarray comprises N unit arrays of the M unit arrays, M is a positive integer, N is a positive integer less than M, and T1 is a positive integer greater than or equal to N. The path of the cascaded channel in the angle domain is estimated based on the T1 reference signals, and a first codebook is determined based on the path of the angle domain. The first codebook includes at least one weight, which is the weight of E unit arrays in the M unit arrays. The cascaded channel includes a channel between the network device and the RIS, and a channel between the RIS and the terminal device. E is a positive integer less than or equal to M. Send a third message to the RIS, the third message being used to instruct the first codebook, the first codebook being used by the RIS to reflect the reference signal; Receive T2 reference signals from the terminal device reflected by the E unit arrays, wherein the T2 reference signals are processed according to the first codebook, and T2 is a positive integer greater than or equal to the diameter of the angular domain and less than M; The cascaded channel is estimated based on the T2 reference signals.

4. The method according to claim 3, characterized in that, The first codebook satisfies the following relationship: Among them, W Dr This represents the first codebook. D represents the new dictionary matrix of the angle domain obtained according to the first codebook. r Let X represent the original dictionary matrix of the angle domain, L represent the diameter of the angle domain, and X represent the original dictionary matrix of the angle domain. H Let X denote the conjugate transpose of matrix X, and D(:,L) denote the L column vectors of matrix D.

5. The method according to claim 4, characterized in that, The dimension is T2×R, where R represents the resolution of the angular domain.

6. The method according to claim 4 or 5, characterized in that, The first subarray is a linear array, D r The dimension is N×R; or, The first subarray is a planar array. Among them, D rH D represents a row matrix. rV D represents a column matrix. rH The dimension is p×R, D rV The dimension of the matrix is ​​q×R, and the dimension of the first submatrix is ​​p×q. This expresses the expression for the Kronecker product of a and b; Where R represents the resolution of the angular domain.

7. The method according to any one of claims 3 to 6, characterized in that, Sending third information to the RIS includes: Send the first codebook to the RIS; or, Send the index of the path of the angle domain in the original dictionary matrix of the angle domain to the RIS.

8. The method according to any one of claims 3 to 7, characterized in that, Estimating the angular domain path of the cascaded channel based on the T1 reference signals includes: The diameter of the angle domain is estimated based on the T1 reference signals using a compressed sensing algorithm.

9. The method according to any one of claims 3 to 8, characterized in that, The method further includes: Send a fourth message to the RIS, the fourth message including one or more of the following: the value of N, the number of rows of the N cell arrays, or the number of columns of the N cell arrays.

10. The method according to any one of claims 3 to 9, characterized in that, The N unit arrays are consecutive unit arrays.

11. A channel estimation method, characterized in that, The method includes: T1 reference signals are sent from the first subarray of the RIS to the network device. The RIS includes M unit subarrays, and the first subarray includes N unit subarrays from the M unit subarrays. M is a positive integer, N is a positive integer less than M, and T1 is a positive integer greater than or equal to N and less than M. Receive third information from the network device, the third information being used to indicate a first codebook, the first codebook including at least one weight, the at least one weight being the weight of E unit arrays in the M unit arrays, the first codebook being determined based on the T1 reference signals, where E is a positive integer less than or equal to M; T2 reference signals reflected from the E unit arrays to the network device are transmitted. The T2 reference signals are used to estimate the concatenated channel. The T2 reference signals are processed according to the first codebook. T2 is a positive integer greater than or equal to the diameter of the angular domain of the concatenated channel and less than M. The concatenated channel includes the channel between the network device and the RIS, and the channel between the RIS and the terminal device.

12. The method according to claim 11, characterized in that, The first codebook satisfies the following relationship: Among them, W Dr This represents the first codebook. D represents the new dictionary matrix of the angle domain obtained according to the first codebook. r Let X represent the original dictionary matrix of the angle domain, L represent the diameter of the angle domain, and X represent the original dictionary matrix of the angle domain. H Let X denote the conjugate transpose of matrix X, and D(:,L) denote the L column vectors of matrix D.

13. The method according to claim 12, characterized in that, The dimension is T2×R, where R represents the resolution of the angular domain.

14. The method according to claim 12 or 13, characterized in that, The first subarray is a linear array, D r The dimension is N sub ×R, N sub This indicates the number of element subarrays included in the first subarray; or, The first subarray is a planar array. Among them, D rH D represents a row matrix. rV D represents a column matrix. rH The dimension is p×R, D rV The dimension of the matrix is ​​q×R, and the dimension of the first submatrix is ​​p×q. This expresses the expression for the Kronecker product of a and b; Where R represents the resolution of the angular domain.

15. The method according to any one of claims 11 to 14, characterized in that, Receive third information from the network device, including: Receive the first codebook from the network device; or, Receive the index of the path of the angle domain from the network device in the original dictionary matrix of the angle domain.

16. The method according to any one of claims 11 to 15, characterized in that, The method further includes: Receive fourth information from the network device, the fourth information including one or more of the following: the value of N, the number of rows of the N cell arrays, or the number of columns of the N cell arrays.

17. The method according to any one of claims 11 to 16, characterized in that, The N unit arrays are consecutive unit arrays.

18. A communication device, characterized in that, include: processor; The processor is configured to execute one or more computer programs stored in the memory to cause the communication device to perform the method as described in any one of claims 1 to 2, or to cause the communication device to perform the method as described in any one of claims 3 to 10, or to cause the communication device to perform the method as described in any one of claims 11 to 17.

19. The communication device according to claim 18, characterized in that, The communication device also includes the memory.

20. The communication device according to claim 18 or 19, characterized in that, The communication device is a chip or chip system.

21. A communication device, characterized in that, It includes a module for performing the method as described in any one of claims 1 to 2, or includes a module for performing the method as described in any one of claims 3 to 10, or includes a module for performing the method as described in any one of claims 11 to 17.

22. A chip system, characterized in that, The chip system includes logic circuits and input / output interfaces, wherein the input / output interfaces are used to communicate with other communication devices outside the chip system, and the logic circuits are used to perform the method as described in any one of claims 1 to 2, or the logic circuits are used to perform the method as described in any one of claims 3 to 10, or the logic circuits are used to perform the method as described in any one of claims 11 to 17.

23. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store a computer program that, when run on a computer, causes the computer to perform the method as described in any one of claims 1 to 2, or causes the computer to perform the method as described in any one of claims 3 to 10, or causes the computer to perform the method as described in any one of claims 11 to 17.

24. A computer program product, characterized in that, The computer program product includes a computer program that, when run on a computer, causes the computer to perform the method as described in any one of claims 1 to 2, or causes the computer to perform the method as described in any one of claims 3 to 10, or causes the computer to perform the method as described in any one of claims 11 to 17.

25. A communication system, characterized in that, It includes a communication device for performing the method as described in any one of claims 1 to 2, a communication device for performing the method as described in any one of claims 3 to 10, and a communication device for performing the method as described in any one of claims 11 to 17.

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