Channel estimation method, device and system

Abstract

The invention relates to a channel estimation method, device and system. The terminal equipment sends T1 reference signals, the T1 reference signals are reflected to the network equipment through the RIS, T1 is a positive integer smaller than M, and M is the number of unit arrays included in the RIS. And the terminal equipment receives first information from the network equipment, the first information is used for indicating the value of T2, and T2 is a positive integer smaller than M. The terminal device sends T2 reference signals, the T2 reference signals are reflected to the network device through the RIS, the T2 reference signals are used for estimating a cascade channel, and the cascade channel comprises a channel between the network device and the RIS and a channel between the RIS and the terminal device. Through the technical scheme of the embodiment of the invention, the transmission overhead of the reference signal can be reduced.

Description

Channel estimation method, device and system Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a channel estimation method, device, and system. Background Art

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

[0003] For example, in a scenario where the communicating parties are a base station and user equipment (UE), the RIS channel includes both the channel between the base station and the RIS and 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 comprises multiple elements. To estimate the RIS channel, the number of reference signals transmitted by the UE must be greater than or equal to the number of elements in the RIS. Since the number of elements in the RIS is typically large, e.g., thousands, the reference signal overhead incurred by estimating the RIS channel is significant.

[0004] Summary of the Invention

[0005] Embodiments of the present application provide a channel estimation method, apparatus, and system for reducing reference signal overhead when estimating a RIS channel.

[0006] In a first aspect, a first channel estimation method is provided. The method can be executed by a terminal device, or by another device including terminal device functions, or by a chip system (or chip) or other functional module. The chip system or functional module can implement the corresponding functions of the terminal device. The chip system or functional module is, for example, provided in the terminal device. The method includes: sending T1 reference signals, wherein the T1 reference signals are reflected to a network device via a RIS, where T1 is a positive integer less than M, and M is the number of unit arrays included in the RIS; receiving first information from the network device, wherein the first information is used to indicate a value of T2, where T2 is a positive integer less than M; and sending T2 reference signals, wherein the T2 reference signals are reflected to the network device via the RIS, and the T2 reference signals are used to estimate a cascade channel, wherein the cascade channel includes a channel between the network device and the RIS, and a channel between the RIS and the terminal device.

[0007] In this embodiment of the present application, the terminal device may 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 included in the RIS, M. In the second round, T2 reference signals are sent, where T2 is a value indicated by the network device and is also less than M. For example, the sum of T1 and T2 is also less than M. This shows that the number of reference signals sent by the terminal device is much less than the total number of element arrays included in the RIS, thereby saving reference signal overhead.

[0008] In an optional embodiment, 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 indicating the value of T1 or indicating the value of N, where N is the number of element arrays included in the first subarray of the RIS, the first subarray being configured to reflect the T1 reference signals, and T1 is a positive integer greater than or equal to N. If the value of T1 is predefined by the protocol, for example, the terminal device can directly determine the value of T1 without requiring an indication from the network device, thus saving signaling overhead. Alternatively, if the value of N is predefined by the protocol, the terminal device can simply set T1 to be greater than or equal to N, thereby determining the value of T1 and eliminating the need for an indication from the network device. Alternatively, the value of T1 can be determined and indicated by the network device, allowing for greater flexibility in its value.

[0009] In a second aspect, a second channel estimation method is provided, which can be executed by a network device, or by other devices including the functions of a network device, or by a chip system (or, chip) or other functional module, the chip system or functional module can realize the functions of the network device, and the chip system or functional module is, for example, set in the network device. The method includes: receiving T1 reference signals from a terminal device reflected by a first subarray of a RIS, the RIS including M unit arrays, the first subarray including 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 and less than M; estimating the diameter of the angle domain of the cascaded channel based on the T1 reference signals, and determining a first codebook based on the diameter of the angle domain, the first codebook including at least one weight, the at least one weight being the weight of E unit arrays of the M unit arrays, the cascaded channel including The method includes: a channel between the network device and the RIS, and a channel between the RIS and the terminal device, where E is a positive integer less than or equal to M; sending third information to the RIS, the third information indicating the first codebook used for reflecting reference signals from the RIS; receiving T2 reference signals from the terminal device reflected by the E element 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 angle domain and less than M; and estimating the concatenated channel 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.

[0010] In an optional implementation, the first codebook satisfies the following relationship: Among them, W Dr represents the first codebook, Denotes the new dictionary matrix of the angle domain obtained according to the first codebook, D r represents the original dictionary matrix of the angle domain, L represents the diameter of the angle domain, X H = represents the conjugate transposed matrix of matrix X, and D(:,L) represents the L column vector of matrix D. Since the construction of the dictionary matrix in 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 is ​​still orthogonal to the diameter of the angle domain. In the embodiment of the present application, represents a new dictionary matrix in the angle domain obtained according to the first codebook. That is, after weighting the unit matrix of the 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 angle domain diameter, thereby improving the accuracy of channel estimation.

[0011] In an optional embodiment, The dimension is T2×R, where R represents the resolution of the angular domain.

[0012] In an optional embodiment, the first sub-array is a linear array, D r The dimension is N×R; or, the first sub-array is a planar array, Among them, D rH represents the row matrix, D rV represents the column matrix, D rH The dimensions are p×R, D rV The dimension of is q×R, the dimension of the first sub-matrix is ​​p×q, Denotes the Kronecker product of a and b. Where R represents the resolution of the angle domain. D r Can be used to weight the first sub-matrix, so D r The dimension of can vary with the change of the first sub-matrix.

[0013] In an optional embodiment, sending the third information to the RIS includes: sending the first codebook to the RIS; or sending the index of the angle-domain diameter 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, thereby simplifying RIS implementation. Alternatively, the network device can send the index of the angle-domain diameter to the RIS, allowing the RIS to obtain the first codebook based on the index. The angle-domain diameter index contains less information than the first codebook, thereby reducing signaling overhead.

[0014] In an optional embodiment, estimating the diameter of the angular domain of the concatenated channel according to the T1 reference signals includes: estimating the diameter of the angular domain according to the T1 reference signals using a compressed sensing algorithm or a statistical algorithm. This embodiment of the application does not limit the algorithm used.

[0015] In an optional embodiment, the method further includes: sending fourth information to the RIS, where the fourth information includes one or more of the following: the value of N, the number of rows of the N unit arrays, or the number of columns of the N unit arrays. For example, if the first subarray is determined by a network device, the network device may send relevant parameters of the first subarray to the RIS, allowing the RIS to determine the first subarray accordingly. Alternatively, the first subarray may be determined by another device, in which case the other device may send the parameters of the first subarray to the RIS, optionally also to the network device. Alternatively, if the first subarray is determined by the RIS, the RIS may send fourth information to the network device to indicate the parameters of the first subarray.

[0016] In an optional embodiment, the N unit arrays are continuous unit arrays. The N unit arrays can be continuously distributed unit arrays, thereby simplifying the calculation process of the network device when estimating the diameter of the angle domain.

[0017] In a third aspect, a third channel estimation method is provided, which can be performed by a RIS or a component in the RIS (such as a RIS device), wherein the component includes at least one of a processor, a transceiver, a processing unit, or a transceiver unit. Taking the execution entity as an RIS as an example, the method may include: sending T1 reference signals reflected by a first subarray of the RIS toward a network device, the RIS including M unit cells, the first subarray including N unit cells of the M unit cells, M being a positive integer, N being a positive integer less than M, and T1 being 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 including at least one weight, the at least one weight being a weight of E unit cells of the M unit cells, the first codebook being determined based on the T1 reference signals, E being a positive integer less than or equal to M; and sending T2 reference signals reflected by the E unit cells toward 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 a 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 between the RIS and the terminal device.

[0018] In an optional implementation, the first codebook satisfies the following relationship: Among them, W Dr represents the first codebook, Denotes the new dictionary matrix of the angle domain obtained according to the first codebook, D r represents the original dictionary matrix of the angle domain, L represents the diameter of the angle domain, X H represents the conjugate transposed matrix of matrix X, and D(:,L) represents taking the L column vector of matrix D.

[0019] In an optional embodiment, The dimension is T2×R, where R represents the resolution of the angular domain.

[0020] In an optional embodiment, the first sub-array is a linear array, D r The dimension is N sub ×R,N sub represents the number of unit arrays included in the first sub-array; or, the first sub-array is a planar array, Among them, DrH represents the row matrix, D rV represents the column matrix, D rH The dimensions are p×R, D rV The dimension of is q×R, the dimension of the first sub-matrix is ​​p×q, represents the Kronecker product of a and b, wherein R represents the resolution of the angle domain.

[0021] In an optional implementation, receiving the third information from the network device includes: receiving the first codebook from the network device; or receiving the index of the angle-domain diameter in the original dictionary matrix of the angle domain from the network device.

[0022] In an optional embodiment, the method further includes: receiving fourth information from the network device, the fourth information including one or more of the following: a value of N, the number of rows of the N unit arrays, or the number of columns of the N unit arrays.

[0023] In an optional implementation, the N unit arrays are continuous unit arrays.

[0024] Regarding the technical effects brought about by the third aspect or various optional implementations, reference may be made to the introduction to the technical effects of the first aspect or the corresponding implementations, and / or reference may be made to the introduction to the technical effects of the second aspect or the corresponding implementations.

[0025] In a fourth aspect, a communication device is provided. This device can implement the method described in the first, second, or third aspects, or any possible design thereof, performed by a RIS; or, can be used to implement the method described in the first, second, or third aspects, or any possible design thereof, performed by a network device; or, can be used to implement the method described in the first, second, or third aspects, or any possible design thereof, performed by a terminal device. This device can 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.

[0026] In an optional implementation, the device may include a module that performs the methods / operations / steps / actions described in the first to third aspects and any possible implementations above. The module may be a hardware circuit, software, or a combination of a hardware circuit and software. In an optional implementation, the device includes a processing unit (sometimes also referred to as a processing module) and a transceiver unit (sometimes also referred to as a communication unit, a communication module, or a transceiver module). The transceiver unit is capable of implementing a sending function and a receiving function. When the transceiver unit implements the sending function, it may be referred to as a sending unit (sometimes also referred to as a sending module). When the transceiver unit implements the receiving function, it may be referred to as a receiving unit (sometimes also referred to as a receiving module). The sending unit and the receiving unit may be the same functional module, which is called a transceiver unit, and the functional module is capable of implementing a sending function and a receiving function; or, the sending unit and the receiving unit may be different functional modules, and the transceiver unit is a general term for these functional modules.

[0027] For another example, the apparatus includes a processor coupled to a memory, configured to execute instructions in the memory to implement the methods described in aspects 1 through 3 above and any possible implementations. Optionally, the apparatus also includes other components, such as an antenna, an input / output module, an interface, and the like. These components may be hardware, software, or a combination of hardware and software.

[0028] In a fifth aspect, a computer-readable storage medium is provided, which is used to store computer programs or instructions. When the computer-readable storage medium is executed, the method of any one of the first to third aspects is implemented.

[0029] In a sixth aspect, a computer program product comprising instructions is provided, which, when executed on a computer, enables the method described in any one of the first to third aspects to be implemented.

[0030] In the seventh aspect, a chip system is provided, which includes a logic circuit (or it can be understood that the chip system includes a processor, and the processor may include a logic circuit, etc.), and may also include an input and output interface. The input and output interface can be used to receive messages or to send messages. The input and output interfaces can be the same interface, that is, the same interface can implement both the sending function and the receiving function; or, the input and output interface includes an input interface and an output interface, the input interface is used to implement the receiving function, that is, for receiving messages; the output interface is used to implement the sending function, that is, for sending messages. The logic circuit 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 circuit can also be used to transmit messages to the input and output interface, or receive messages from other communication devices from the input and output interface. 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 a chip, or it can include a chip and other discrete devices.

[0031] Optionally, the chip system may further include a memory, which may be used to store instructions, and the logic circuit may call the instructions stored in the memory to implement corresponding functions.

[0032] In an eighth aspect, a communication system is provided, which may include an apparatus for implementing the first aspect and any possible design thereof, an apparatus for implementing the second aspect and any possible design thereof, and an apparatus for implementing the third aspect and any possible design thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a schematic diagram of an application scenario of an embodiment of the present application;

[0034] FIG2 is a schematic diagram showing the working principle of RIS;

[0035] FIG3 is a flow chart of a channel estimation method provided in an embodiment of the present application;

[0036] FIG4 is a schematic structural diagram of a communication device provided by the present application;

[0037] FIG5 is a schematic structural diagram of another communication device provided by the present application;

[0038] FIG6 is a schematic structural diagram of another communication device provided in this application. DETAILED DESCRIPTION

[0039] The embodiment of the present application provides a channel estimation method and device. Among them, the method and the device are based on the same inventive concept. Since the principles of the method and the device for solving the problem are similar, the implementation of the device and the method can refer to each other, and the repeated parts will not be repeated. In the description of the embodiment of the present application, "and / or" describes the association relationship of the associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. At least one involved in the embodiment of the present application refers to one or more; multiple refers to two or more. In addition, it should be understood that in the description of the embodiment of the present application, words such as "first" and "second" are only used to distinguish the purpose of description, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order.

[0040] The channel estimation method provided in the embodiment of the present application can be applied to a fourth generation (4G) communication system, such as a long term evolution (LTE) communication system, and can also be applied to a fifth generation (5G) communication system, such as a 5G new radio (NR) communication system, or to various future communication systems, such as a sixth generation (6G) communication system. The method provided in the embodiment of the present application can also be applied to a Bluetooth system, a wireless fidelity (Wifi) system, a long range radio (LoRa) system, or a vehicle networking system. The method provided in the embodiment of the present application can also be applied to a satellite communication system, wherein the satellite communication system can be integrated with the above-mentioned communication system.

[0041] For ease of understanding, the application scenarios of the embodiments of the present application are described using the communication system architecture shown in Figure 1 as an example. Referring to Figure 1, the communication system includes a network device 101 and a terminal device 102. The apparatus provided in the embodiments of the present application can be applied to the network device 101 or to the terminal device 102. It will be understood that Figure 1 only illustrates one possible communication system architecture that can be applied to the embodiments of the present application. In other possible scenarios, the communication system architecture may also include other devices.

[0042] The network device 101 is a node in a radio access network (RAN), which may also be referred to as a base station or a RAN node (or device). Currently, some examples of radio access network devices include: a next-generation base station (gNodeB / gNB / NR-NB), a transmission reception point (TRP), an evolved Node B (eNB), a radio network controller (RNC), a Node B (NB), a base station controller (BSC), a base transceiver station (BTS), a home base station (e.g., a home evolved NodeB, or home Node B, HNB), a base band unit (BBU), or a wireless fidelity (Wifi) access point (AP), satellite equipment, or network equipment in a 5G communication system, or network equipment in a possible future communication system. The network device 101 may also be another device having network device functions. For example, the network device 101 may also be a device that functions as a network device in device-to-device (D2D) communication, Internet of Vehicles (IoV) communication, or machine communication. The network device 101 may also be a network device in a possible future communication system.

[0043] In some deployments, a gNB may include a centralized unit (CU) and a distributed unit (DU). The gNB may also include a radio unit (RU). The CU implements some gNB functions, while the DU implements some gNB functions. 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. Because RRC layer information ultimately becomes PHY layer information, or is converted from PHY layer information, in this architecture, higher-layer signaling, such as RRC layer signaling or PDCP layer signaling, can also be considered to be sent by the DU, or by both the DU and the RU. It is understood that a network device can be a CU node, a DU node, or a device that includes both a CU node and a DU node. In addition, the CU can be divided into a network device in the access network RAN, and the CU can also be divided into a network device in the core network CN, which is not limited here.

[0044] Terminal device 102, such as user equipment (UE), mobile station (MS), or mobile terminal (MT), provides voice or data connectivity to users and may also be an IoT device. For example, terminal devices include handheld devices and vehicle-mounted devices with wireless connectivity. At present, terminal devices can be: mobile phones, tablet computers, laptops, PDAs, mobile internet devices (MIDs), wearable devices (such as smart watches, smart bracelets, pedometers, etc.), vehicle-mounted devices (such as cars, bicycles, electric vehicles, airplanes, ships, trains, high-speed railways, etc.), virtual reality (VR) devices, augmented reality (AR) devices, wireless terminals in industrial control, smart home devices (such as refrigerators, TVs, air conditioners, electric meters, etc.), intelligent robots, workshop equipment, wireless terminals in unmanned 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, flying equipment (such as intelligent robots, hot air balloons, drones, airplanes), etc. The terminal device can also be other devices with terminal functions. For example, the terminal device can also be a device that serves as a terminal function in D2D communication. In the embodiments of the present application, the terminal device with wireless transceiver functions and the chip that can be set in the aforementioned terminal device are collectively referred to as a terminal device.

[0045] The following is an introduction to the technical terms that may be involved in the embodiments of this application.

[0046] In this article, X H Represents the conjugate transpose of X. diag(X) represents taking the diagonal matrix of X. X(:,Y) represents taking the Y column vectors in the matrix X.

[0047] A reference signal may be provided by a transmitting end to a receiving end and may be used for channel estimation or channel detection, etc. For example, a reference signal may also be called a pilot signal, etc.

[0048] RIS is a digitally reconfigurable artificial electromagnetic surface (RIS), an artificial composite structure composed of a large number of subwavelength digitally reconfigurable artificial electromagnetic units (or reflective elements) arranged in a specific macroscopic pattern (periodic or aperiodic). Depending on the specific materials used for the reflective elements, RIS can be categorized as antenna array-based or metamaterial-based. By adjusting the phase shifts of all reflective elements, reflected signals can be configured to propagate in the desired direction. Thanks to the rapid development of metamaterials, the reflection coefficient of each element can be configured in real time to adapt to the dynamically fluctuating wireless propagation environment.

[0049] Because the basic units and arrangements of RIS can be arbitrarily designed, they can overcome the limitations of traditional materials, which are difficult to precisely manipulate at the atomic or molecular level. This allows the construction of extraordinary media parameters unattainable with traditional materials and technologies, such as those with both positive and negative permittivity. Materials with extraordinary media parameters are referred to as metamaterials. Because they control electromagnetic waves by varying the spatial arrangement of digitally encoded units—that is, by altering the state distribution of the basic units, the properties of the electromagnetic field at a specific spatial location can be controlled—in some embodiments, metamaterials can also be referred to as digital electromagnetic metamaterials or electromagnetically coded metamaterials.

[0050] RIS can be mounted on large flat surfaces (such as walls or ceilings indoors, buildings or signs outdoors) to reflect RF energy around obstacles and create a virtual line-of-sight propagation path between the communication source and destination.

[0051] For example, see Figure 2, which illustrates the working principle of the RIS. Figure 2 uses the uplink transmission process as an example, with a network device and a user equipment (UE) as the communicating parties. As shown in Figure 2, after the signal transmitted by the UE reaches the RIS, it is reflected by the RIS's cell array (or cells, array, etc.). The network device then receives the reflected signal from the RIS.

[0052] Assuming that the network device has K antennas, the RIS has M element arrays, and the UE uses a single antenna, the signal obtained by the network device after demodulating the received reference signal can be expressed as:

[0053] Y all =F H diag(W)H+H BS-UE (Formula 1)

[0054] Among them, F H Y represents the conjugate transpose of the channel F between the network device and RIS. all It represents the signal obtained by demodulating the received reference signal by the network device. W represents the weight of the unit array included in RIS, and diag(W) represents the diagonalization of the matrix W. H represents the channel between RIS and UE, and H represents the channel between RIS and UE. BS-UE Indicates the channel between the network device and the UE. all The dimension is K × 1, where K is the number of antennas on the network device. For channel estimation methods between network devices and UEs, refer to existing technologies and will not be elaborated on here. This article focuses on cascaded channels, namely, the channels between the network device and the RIS, and the channels between the RIS and the UE.

[0055] The cascaded channel can be obtained through two measurement processes, which are as follows:

[0056] The first measurement process: turn off RIS, then RIS will no longer work, and the channel H between the network device and the UE can be measured. BS-UE .

[0057] Second measurement process: Turn on RIS, RIS reflects the signal between the network device and the UE, and then Y can be measured. all , from which the cascade channel can be obtained. For example, the signal received by the network device through the cascade channel can be expressed as:

[0058] Y=Y all -H BS-UE =F H diag(W)H (Formula 2)

[0059] The dimension of Y is K×1. all The difference is that Y all In addition to considering the cascade channel,

[15] also considers the channel between the network device and the UE, while

[16] considers the cascade channel but does not consider the channel between the network device and the UE.

[0060] By performing a conjugate transpose on Y, we can obtain:

[0061] Y H =W H G (Formula 3)

[0062] Among them, Y H represents the conjugate transpose of Y, W H represents the conjugate transpose of W, G represents the cascade channel, G = diag(H H )The dimensions of F and G are M×K.

[0063] For example, if the UE sends T reference signals, the T reference signals received by the network device can be expressed as:

[0064]

[0065] in, The dimension is T×M, The dimension is T×K. W T The conjugate transpose of W T represents the weights of the unit arrays used to reflect T reference signals included in the RIS.

[0066] Generally, the cascade channel can be obtained by the following relationship:

[0067]

[0068] in, represents the estimated value of the cascade channel, express The pseudo-inverse matrix of . If Equation 5 is to have a solution, then T must be greater than or equal to M. It can be seen that when the number of unit arrays included in the RIS is too large, the reference signal overhead also increases accordingly.

[0069] In view of this, embodiments of the present application provide a channel estimation method for reducing reference signal overhead when performing channel estimation. In embodiments of the present application, the concatenated channel is, for example, a sparse channel. In embodiments of the present application, a terminal device may 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. The N element arrays are a portion of the element arrays included in the RIS, i.e., N is less than the total number of element arrays included in the RIS. Optionally, N may be much smaller than M. For example, N may be on a first order of magnitude, and M may be on a second order of magnitude, with the first order of magnitude being smaller than the second order of magnitude. For example, the first order of magnitude is "tens," meaning the first sub-array may include dozens of element arrays, e.g., N = 40; the second order of magnitude is "thousands," meaning the RIS may include thousands of element arrays, e.g., M = 1024. Optionally, even if T1 is larger than the diameter of the angular domain, the order of magnitude of T1 may 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 angular domain of the concatenated channel and less than M. Generally, the diameter of the angular domain is much smaller than the number of element arrays included in the RIS. For example, the diameter of the angular domain is of the same order of magnitude as N, such as the diameter of the angular domain = 20. Optionally, even if T2 is greater than the diameter of the angular domain, the order of magnitude of T2 and the diameter of the angular domain can be the same. 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, thereby saving reference signal overhead. Moreover, since T1 is greater than or equal to N, the accuracy of the angular domain diameter of the concatenated channel estimated based on the T1 reference signals can be guaranteed, and the first codebook determined based on the angular domain diameter will also be more accurate, thereby improving the accuracy of the concatenated channel estimated based on the T2 reference signals.

[0070] In order to better introduce the embodiments of the present application, the methods provided by the embodiments of the present application are described below in conjunction with the accompanying drawings. In each embodiment of the present application, the terminal device is described using the UE as an example. The methods provided by each embodiment of the present application can be applied to the network architecture shown in Figure 1. For example, the UE involved in the embodiment of the present application is the terminal device 102 in Figure 1; the network device involved in the embodiment of the present application is the network device 101 in Figure 1; the RIS involved in the embodiment of the present application can be set between the terminal device 102 and the network device 101 in Figure 1, for example, refer to Figure 2.

[0071] Please refer to FIG3 , which is a flow chart of a channel estimation method provided in an embodiment of the present application.

[0072] S301: UE sends T1 reference signals. UE sends T1 reference signals to network equipment, but RIS is set between UE and network equipment and will receive T1 reference signals first.

[0073] It can also be understood that the UE sends T1 reference signals, where each reference signal sent can be considered as one reference signal. For example, the UE can send T1 reference signals at T1 times, where one time is, for example, a time point, or an orthogonal frequency division multiplexing (OFDM) symbol, or a time slot.

[0074] The value of T1 is, for example, predefined, such as predefined by a protocol; or, the value of T1 is determined by negotiation between the UE and the network device before S301; or, the value of T1 can be configured by the network device, for example, before S301, the network device sends second information to the UE to indicate the value of T1.

[0075] S302: The first sub-array of the RIS reflects T1 reference signals, and the corresponding network device receives the T1 reference signals reflected by the first sub-array of the RIS.

[0076] The RIS may include M unit arrays, and the first subarray may 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 may be continuous, which does not reduce the resolution of the RIS. Alternatively, at least two unit arrays in the N unit arrays may be discontinuous. For example, if the spacing between adjacent unit arrays in the RIS is small, the coupling between the unit arrays may be excessive. In this case, the first subarray may include discontinuous unit arrays, thereby reducing the resolution of the first subarray.

[0077] In other words, the RIS can reflect T1 reference signals using some of the element arrays, rather than using all of them, thus reducing RIS power consumption. T1 can be a positive integer greater than or equal to N, for example, T1 is also less than M. Therefore, the UE's overhead for transmitting T1 reference signals is low. For example, N can be much smaller than M, with M being in the thousands and N being in the hundreds or tens. This significantly reduces reference signal transmission overhead.

[0078] As described in S301, the network device may send second information to the UE to indicate the value of T1. Alternatively, the second information may not indicate the value of T1, but instead indicate the value of N. After receiving the second information, the UE may 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.

[0079] If the RIS uses the first subarray to reflect T1 reference signals, it must first determine the first subarray. Optionally, the first subarray can be determined by pre-negotiation between the RIS and the network device, for example, before S302; alternatively, the first subarray can be pre-defined via a protocol; alternatively, 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. The fourth information can indicate the first subarray. For example, the fourth information can indicate (or include) one or more of the following: the value of N, the number of rows of the N element array (or, the number of rows of the first subarray), or the number of columns of the N element array (or, the number of columns of the first subarray). In other words, the fourth information can indicate the first subarray by indicating the parameters of the first subarray, and the RIS can determine the first subarray based on the fourth information.

[0080] The RIS uses the first subarray, and changes the weight of the first subarray every time a reference signal is reflected. For example, the RID can use a discrete Fourier transform (DFT) method to determine the weight, or use Hadamard weights.

[0081] S303: The network device estimates the angle domain diameter of the concatenated channel based on the T1 reference signals, and determines a first codebook based on the angle domain diameter. 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 the present application may be applied to a time division duplexing (TDD) system. In a TDD system, uplink and downlink channels have corresponding characteristics, so the concatenated channel can be either an uplink channel or a downlink channel.

[0082] Optionally, the network device may use a compressed sensing algorithm to estimate the angle domain diameter of the concatenated channel based on the T1 reference signals. Alternatively, the network device may use other algorithms to estimate the angle domain diameter of the concatenated channel based on the T1 reference signals, such as a statistical algorithm, without further limitation.

[0083] For example, the diameter of the angle domain of the cascaded channel is represented by L. Taking the case where the network device uses a compressed sensing algorithm to determine L as an example, the network device may use a compressed sensing algorithm such as an orthogonal matching pursuit (OMP) algorithm, a subspace pursuit (SP) algorithm, or a compressive sampling matching pursuit (CoSaMP) algorithm to determine L. Alternatively, the network device may also use an improved OMP algorithm (such as a multi-step OMP algorithm) to determine L.

[0084] The following is a brief introduction to the OMP algorithm. For example, for the linear equation system Ax=b, if each column in the matrix A is regarded as a variable, then the OMP algorithm selects the variable with the highest correlation with the current residual in each iteration process. Among them, after each iteration, the residual used to judge the correlation of the variables can be obtained in the previous iteration process, and each iteration process can obtain the residual used in the next iteration process. The residual of an iterative process can be obtained by calculating the difference between b and the orthogonal projection of b on the subspace of the matrix A. The subspace is composed of the variables selected in each iteration process. For example, after each iteration, the variables selected in this iteration can be added to the subspace. Among them, one iterative process can obtain one variable, and the number of iterations can be determined according to the number of variables required. For example, if 30 variables are required, 30 iterations can be performed.

[0085] In other words, if there are no zero elements in x, then b should belong to the column vector space Span(A) of matrix A. However, since there are many zero elements in x, b should belong to a subspace of Span(A) (wherein, belonging to the subspace also belongs to the entire space of Span(A)). For example, the subspace of Span(A) to which b belongs is denoted as Span(A) sub ), where A sub Includes one or more column vectors of matrix A, and the x corresponding to these column vectors is denoted as x sub If you can get an A sub and x sub , we can solve the following optimization problem:

[0086]

[0087] Here, argmin f(x) represents the variable value that minimizes the objective function f(x). Represents the second normal form of matrix X.

[0088] The steps of the OMP algorithm are as follows.

[0089] S11. Input matrices A, 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 x=0. represents the empty set, that is, the set S is empty initially.

[0090] S12. Calculate i=argmax i |A i H r k |, put i into the set S, that is, S = S∪{i}. Among them, ∪ means to find the union, and i means the index of the variable selected from the matrix A in one iteration. A i Represents the column vector with the largest residual among the column vectors included in matrix A. k represents the residual of the k-th cycle (or, iteration).

[0091] S13. Calculate P k =A S (A S H A S ) -1 A S H , r k =(IP k )b. Among them, P k Represents the projection of the variable selected in the kth iteration on the subspace of matrix A. S Denotes the set of column vectors with the largest residual determined from the matrix A in each cycle after the k-th cycle (or iteration). I denotes the identity matrix.

[0092] S14. Repeat steps 2 and 3 Q times.

[0093] S15. Calculate x s =(A S H A S ) -1 A S H b, x s Represents the value of the position in x indicated by the element included in the set S.

[0094] S16. Return x s .

[0095] When A cycles (or iterations) are completed, A S =A sub , x S =x sub .

[0096] In the embodiment of the present application, A=D r Or A=W H D r , that is, the matrix A can be regarded as a dictionary matrix. k =Res t , about Res t This will be introduced later. x=G. Indicates the T reference signals Y received by the network device T The conjugate transpose of G represents the cascade channel. r 、W H D r etc. will be introduced later.

[0097] The residual of each iteration process can be determined as follows:

[0098]

[0099] L t =L t-1 ∩i (Formula 8)

[0100]

[0101]

[0102] Among them, L t-1 ∩i represents L t-1 The intersection with i. D r (:,i) means taking matrix D r The i column vector of D r (:,i) H Indicates D r The conjugate transpose of (:,i). argmax f(x) represents the variable value when the objective function f(x) takes the maximum value. Res represents the residual, where Res0 represents the initial residual (for example, b), and Res t-1 Represents the residual obtained during the t-1th cycle (or iteration), Res t Represents the residual obtained from the t-th cycle (or iteration). t-1Represents the index set of the diameter of the angle domain determined in the t-1th cycle (or iteration) in the dictionary matrix, L t Represents the set of indices in the dictionary matrix of the diameter of the angle domain determined during the t-th cycle (or iteration).

[0103] As can be seen from the above steps, the OMP algorithm selects a variable and places it in the subspace during each iteration, thus ensuring that the optimal solution is selected each time. However, if two variables are correlated, the two variables, when taken together, may not be the two globally optimal solutions. For example, referring to Table 1, we can see that the OMP algorithm focuses on the current optimal solution during each iteration, but not on the global optimal solution. The variable ultimately selected may not be the globally optimal variable, which can lead to the OMP algorithm being subject to local optimality. The index in Table 1 represents the index of the column vector in matrix A.

[0104] Table 1

[0105]

[0106] In view of this, the embodiment of the present application may use a multi-step-OMP algorithm to determine the angle domain diameter L. The steps of the multi-step-OMP algorithm are as follows.

[0107] S21, input matrix A, b and the sparsity Q of the b matrix. Initialize the residual r0 = b, the orthogonal projection matrix P0 = 0, and the subspace index set The restored signal x = 0, the residual convergence threshold ε. represents the empty set, that is, the set S is empty initially.

[0108] S22. Calculate P=argmax P |A P H r k |, put set P into set S, that is, 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 with the current residual during one iteration. P is a positive integer, for example, P can be greater than or equal to 2. As can be seen, in the multi-step-OMP algorithm, multiple variables can be selected in each iteration, thereby increasing the probability of obtaining the global optimal solution. When P = Q, the multi-step-OMP algorithm can be regarded as the SP algorithm, and when Q = 2P, the multi-step-OMP algorithm can be regarded as the CoSaMP algorithm.

[0109] A PRepresents the set of P column vectors with the largest residual among the column vectors included in the matrix A. k represents the residual of the k-th cycle (or, iteration).

[0110] S23. Calculate P k =A S (A S H 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 with the largest residual determined from matrix A in each cycle after the kth cycle (or iteration). k Represents the projection of the variable selected in the kth iteration on the subspace of matrix A.

[0111] S24. Repeat steps 2 and 3 until the number of elements in set S is equal to Q+P.

[0112] S25. Calculate Q = argmax K |A S H b|, that is, determine the Q elements in the set S with the largest projection on the matrix b, let S = {Q}. And calculate P k =A S (A S H A S ) -1 A S H , r k =(IP k )b.

[0113] Through S25, the elements in the set S with smaller projections on the matrix b can be removed, and the removed elements may include correlated elements in the set S. Among them, in the beam domain of the channel, when multiple paths are grouped together (for example, in the angle domain of the channel, the path clusters are relatively close, and the path clusters include the multiple paths, and it is not easy to distinguish each path at this time), due to the concentration of energy of these multiple paths, side lobes may be generated on the variables corresponding to other indices in the set S. When the OMP algorithm is used, if a side lobe is generated on a variable, it will cause the projection of the variable on the matrix b to become larger, so it will be misjudged that the variable corresponding to the index is also a path, and the index is regarded as a related element in the set S. Therefore, when the embodiment of the present application adopts the multi-step-OMP algorithm, the correlated elements can be removed, which is equivalent to removing the misjudged path, so that the result obtained is closer to the true path in the angle domain.

[0114] Therefore, the multi-step-OMP algorithm is used to minimize the local optimal situation and increase the probability of obtaining the global optimal solution by selecting more variables in each iteration and removing related elements.

[0115] S26, repeat steps 2, 3, 4, and 5 until |r k -r k-1 |<ε.

[0116] S27. Calculate x s =(A S H A S ) -1 A S H b.x s Represents the value of the element at position S in x.

[0117] S28. Return x s .

[0118] In the embodiment of the present application, A=D r Or A=W H Dr,r k =Res t , x = G. For the calculation method of the residual, please refer to the previous article.

[0119] Once the network device obtains the angle domain diameter L, it can determine the first codebook based on the angle domain diameter. The first codebook may include at least one weight, for example, a row vector in the first codebook is a weight, or a column vector in the first codebook is 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. In other words, each weight may be a weight of the M unit arrays included in the RIS, or may be a weight of a portion of the unit arrays included in the RIS. If the E unit arrays are a portion of the unit arrays included in the RIS, for example, the E unit arrays are the unit arrays included in the first sub-array, then E = N; alternatively, 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 an intersection but are not identical. In both cases, E may be equal to N or not equal to N.

[0120] When reflecting a reference signal, the RIS can weight the reference signal according to the weights included in the first codebook. For example, each time the RIS reflects a reference signal, it weights the reference signal according to a weight included in the first codebook. In other words, the RIS weights the angle-domain dictionary matrix, resulting in a new matrix. If the new matrix is ​​not orthogonal to the angle-domain diameter, residual errors will occur, thereby reducing the accuracy of the channel estimation results. To this end, in embodiments of the present application, the new matrix obtained according to each weight included in the first codebook can be orthogonal to the angle-domain diameter to improve the accuracy of the channel estimation results.

[0121] For example, the angle domain of the concatenated channels can be expressed as:

[0122] G angle =D r H G (Formula 11)

[0123] Among them, G angle represents the angle domain matrix of the cascaded channel, G angle The dimension of D is M×K. r Represents the original dictionary matrix of the angle domain, D r H Indicates D r The conjugate transpose of D. r It can be expressed as:

[0124]

[0125] in, For example, X can be replaced by N, and θ can be replaced by or replace with Etc., that is, here is the formula 12 The calculation method of the formula is as follows. d represents the physical distance between adjacent unit arrays included in RIS, λ represents the wavelength of the operating frequency band of RIS. φ0 represents D r The first angle of the matrix, φ R Indicates D r The Rth 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), and so on. Among them, if f(φ) is cos(a)sin(φ) or sin(a)cos(φ), it means that the structure of RIS is a two-dimensional planar structure. In this case, φ can represent a horizontal angle and a can represent a vertical angle; or, φ can represent a vertical angle and a can represent a horizontal angle. Optionally, D r The dimension of can be related to the first sub-matrix. For example, if the first sub-matrix is ​​a linear array, then D r The dimension of can be N×R. For another example, the first sub-array is a planar array, such as At this time D r The dimension can be pq×R 2 Among them, D rH represents the row matrix, D rV represents the column matrix, D rH The dimensions are p×R, D rV The dimension of is q×R, p×q is the dimension of the first sub-matrix, that is, p is the number of rows of the unit matrix included in the first sub-matrix, and q is the number of columns of the unit matrix included in the first sub-matrix. It means to find the Kronecker product of a and b.

[0126] In addition, the cascade channel can be restored through the following relationship:

[0127] G=D r G angle =D r D r H G=IG=G (Formula 13)

[0128] Where I represents the identity matrix. It can be seen that the channel of the cascade channel in the angle domain can be compressed by the compressed sensing method, for example, the compression method is as follows:

[0129]

[0130] Among them, D r (:,L) means taking D r The L column vectors in D r The dimension of (:,L) is M×L. represents the angular domain estimate of the concatenated channel, The dimension is L × K. L represents the diameter of the angular domain of the cascaded channel.

[0131] If D in Formula 14 is r Replaced with W H D r , then the new matrix obtained by one weighting can be expressed, for example, formula 14 is transformed as follows:

[0132]

[0133] Since the construction of the dictionary matrix in the angle domain is similar to that of the DFT matrix, each column of the dictionary matrix is ​​mutually orthogonal. Therefore, by 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 diameter of the angle domain. To this end, the first codebook in the embodiment of the present application can satisfy the following relationship:

[0134]

[0135] Among them, W Dr represents the first codebook, Denotes the new dictionary matrix in the angle domain obtained according to the first codebook, D r Represents the original dictionary matrix of the angle domain, L represents the diameter of the angle domain, D r (:,L) -1 Indicates D r The inverse of (:,L).

[0136] Optionally, each weight included in the first codebook may be a weight for E element arrays included in the RIS, where E may be a positive integer less than or equal to M. For example, the first codebook represented by Formula 16 may have dimensions of M × T2, where T2 is the number of reference signals reflected by the RIS according to the first codebook. In other words, the first codebook represented by Formula 16 corresponds to E = M. If the RIS uses this first codebook, it uses all element arrays to reflect T2 reference signals.

[0137] Alternatively, if E is less than M, the weights included in the first codebook may also be the weights of some of the M element arrays. That is, the RIS may also use some of the element arrays to reflect T2 reference signals. If this is the case, the first codebook can satisfy the following relationship:

[0138]

[0139] Among them, W Dr_sub It represents the first codebook corresponding to the E unit array, which can be understood as, W Dr_sub It includes one or more weights, each of which is the weight of E unit arrays. represents the new dictionary matrix of the angle domain obtained according to the first codebook, Dr_sub represents the dictionary matrix of the angle domain of E unit arrays, whose dimension is E×L, L represents the diameter of the angle domain, Dr sub (:,L) -1 Indicates Dr. sub The inverse of (:,L).

[0140] S304: The network device sends the third information to the RIS. Correspondingly, the RIS receives the third information from the network device.

[0141] The third information may indicate the first codebook. The third information may indicate the first codebook in various ways. For example, the third information may include the first codebook. In this case, the RIS can directly obtain the first codebook upon receiving the third information without requiring further processing, resulting in a simpler implementation.

[0142] Alternatively, the third information may include L indices, where the L indices are the original dictionary matrix (e.g. D r ) in the index, RIS is based on these L indexes and D r The first codebook can be obtained. For example, if the RIS stores one or more dictionary matrices, and if L indexes are received, the RIS can determine the corresponding L column vectors in the one or more stored dictionary matrices based on these L indexes, and then determine the first codebook based on some algorithms, such as formula (17). If the RIS only stores one dictionary matrix, the number of rows of the dictionary matrix can be greater than or equal to the total number M of unit arrays included in the RIS. Compared to the first codebook, the L indexes contain less information. By indicating the first codebook with L indexes, the transmission overhead of the third information can be reduced.

[0143] S305: The UE sends T2 reference signals. The UE sends T2 reference signals to the network device, but the RIS is set between the UE and the network device and will receive the T2 reference signals first.

[0144] It can also be understood that the UE sends T2 reference signals, where each reference signal sent can be considered as one reference signal. For example, the UE can send T2 reference signals at T2 times, where one time is, for example, a time point, an OFDM symbol, or a time slot.

[0145] For example, T2 is a positive integer greater than or equal to the diameter L of the angle domain. The diameter of the angle domain is determined by the network device, and therefore, the network device can indicate the value of T2 to the UE. Optionally, before S305, the network device can also send first information to the UE, and the first information can indicate the value of T2, so that the UE can determine the value of T2. Alternatively, the first information can indicate the diameter of the angle domain, so that the UE can select a positive integer greater than or equal to the diameter of the angle domain as T2.

[0146] S306: The E unit cells of the RIS reflect T2 reference signals, and accordingly, the network device receives the T2 reference signals reflected by the E unit cells, where E may be equal to M or may be less than M.

[0147] If the RIS uses E element arrays to reflect T2 reference signals, it must first determine the E element arrays. Optionally, the E element arrays may be pre-negotiated between the RIS and the network device, for example, completed before S302; alternatively, the E element arrays may be pre-defined via a protocol; alternatively, the E element arrays may be determined by the network device; or alternatively, the E element arrays may be determined by the RIS. If the E element arrays are determined by the network device, the network device may send fifth information to the RIS before S306. The fifth information may indicate the E element arrays. For example, the fifth information may indicate (or include) one or more of the following: the value of E, the number of rows of the E element arrays, or the number of columns of the E element arrays. In other words, the fifth information indicates the E element arrays by indicating parameters of the E element arrays, and the RIS may determine the E element arrays based on the fifth information. Optionally, the E element arrays are continuous element arrays.

[0148] The RIS uses E element arrays, and each time a reference signal is reflected, the weights of the E element arrays are changed. 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 included in the first codebook can be greater than or equal to T2. The RIS can then select a weight from the first codebook each time a reference signal is reflected. For example, if the weights included in the first codebook are arranged in chronological order, the RIS can select the corresponding weights from the first codebook in chronological order.

[0149] S307: The network device estimates the concatenated channel according to T2 reference signals.

[0150] For example, the network device may estimate the concatenated channel in the following manner:

[0151]

[0152] in, represents the estimated value of the cascade channel, Denote W Dr as the conjugate transpose of D r (:,L) denotes taking the L-th column of matrix D r in it

[0153] 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.

[0154] The embodiment of this application adopts two estimation processes. The first time, it estimates 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 second estimation process by using the estimated paths in the angular domain and transmits them to the RIS. The second time, it estimates the cascaded channel by using the designed RIS weights. Generally speaking, the paths in the angular domain are 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 this application can greatly reduce the overhead of the uplink reference signal and improve the accuracy of channel estimation.

[0155] The following introduces a simulation process to reflect the effects brought by the embodiment of this application. This simulation process adopts the 3rd generation partnership project (3GPP) - cluster delay line type A model (CDL-A).

[0156] During the simulation, in order to construct a sparse channel, a part of the path is intercepted to construct the sparse channel. The parameters of the sparse channel can be referred to Table 2.

[0157] Table 2

[0158]

[0159]

[0160] In Table 2, the channel model parameter 3GPP 38.901, CDL-A, indicates the CDL-A channel model defined in 3GPP protocol version 38.901. 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, and U2 represents the number of vertical antennas. (U1, U2) = (32, 1) indicates 32 horizontal antennas and one vertical antenna, for a total of U1 * U2. The "32" before the colon represents the total number of antennas. The explanations for the base station antenna configuration in Case 2 and the RIS antenna configurations in Cases 1 and 2 are similar. dH represents the horizontal antenna spacing, and dV represents the vertical antenna spacing. λ represents the wavelength. (dH, dV) = (0.5, 0.5)λ, indicating that the horizontal and vertical array spacings of the antenna are both 0.5 wavelengths.

[0161] Please refer to Table 3 for the parameters of the CDL-A channel model.

[0162] Table 3

[0163]

[0164]

[0165] Among them, C ASD Indicates the departure angle extension parameter, C ASA Indicates the arrival angle expansion parameter, C ZSD represents the zenith angle of departure, C ZSA represents the zenith angle of arrival, and XPR represents the cross-polarization power ratio of the antenna.

[0166] As shown in Table 3 above, the content in brackets (eg, []) represents the unit of the parameter.

[0167] The indicator of this simulation is the normalized mean square error Among them, F represents the mean, G krepresents the actual cascade channel corresponding to the k-th UE, represents the estimated value of the concatenated channel corresponding to the kth UE.

[0168] Simulation solution:

[0169] Solution 1: Use the channel estimation process provided in the embodiment of this application. Use the full array of RIS and traditional OMP to estimate L based on T1 reference signals; use the constructed W Dr , estimate the concatenated channel based on T2 reference signals.

[0170] Solution 2: Use the channel estimation process provided in the embodiment of this application. Use the RIS subarray and traditional OMP to estimate L based on T1 reference signals; use the constructed W Dr , estimate the concatenated channel based on T2 reference signals.

[0171] Solution 3: Use the channel estimation process provided in the embodiment of this application. Use the RIS subarray and multi-step-OMP to estimate L based on T1 reference signals; use the constructed W Dr , estimate the concatenated channel based on T2 reference signals.

[0172] Solution 4: Using the current channel estimation solution (technical solution provided by 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 RIS and traditional OMP.

[0173] Solution 5: Using the current channel estimation scheme, the UE sends T reference signals, and the RIS uses random Hadamard code weights to estimate the channel based on the full array of RIS and traditional OMP.

[0174] 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.

[0175] The simulation results can be found in Tables 4 to 7 below.

[0176] Table 4

[0177]

[0178]

[0179] Table 4 shows the comparison of NMSE of different technical solutions in case 1 (refer to Table 2) when the number of reference signals in sparse channels is equal. The values ​​in Table 4 (such as 0.03, 0.82, etc.) represent NMSE.

[0180] Table 5

[0181]

[0182] Table 5 shows the comparison of NMSE of different technical solutions in case 2 (refer to Table 2) when the number of reference signals in the sparse channel is equal. The values ​​in Table 5 (such as 0.083, 0.41, etc.) represent NMSE.

[0183] Table 6

[0184]

[0185] Table 6 shows a comparison of the number of reference signals required by different technical solutions for sparse channels with equal NMSE in Case 1 (see Table 2). The value corresponding to T in Table 6 represents the number of reference signals. For the technical solutions of the embodiments of this application, T refers to the sum of T1 and T2.

[0186] Table 7

[0187]

[0188] Table 7 shows a comparison of the number of reference signals required by different technical solutions for Case 2 (see Table 2) when the NMSE of a sparse channel is equal. The value corresponding to T in Table 7 represents the number of reference signals. For the technical solutions of the embodiments of this application, T refers to the sum of T1 and T2.

[0189] From the above simulation results we can see that:

[0190] (1) Existing channel estimation schemes using DFT or Hadamard code weights have unstable performance when the number of reference signals is small, and require a lot of time to search for better weights, which is inefficient.

[0191] (2) When the number of reference signals used is equal, the NMSE of the channel estimation solution provided by the embodiment of the present application is lower than 50% of the existing solution.

[0192] (3) Under the condition of the same error (eg, the same NMSE), the channel estimation solution provided by the embodiment of the present application reduces the pilot overhead by at least 50% compared to the existing solution.

[0193] It is understandable that in order to implement the functions in the above embodiments, the embodiments of the present application also provide a communication device. The communication device may include hardware structures and / or software modules corresponding to the execution of each function. Those skilled in the art should readily appreciate that, in combination with the units and method steps of each example described in the embodiments disclosed in this application, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in hardware or in a manner driven by computer software depends on the specific application scenario and design constraints of the technical solution.

[0194] Figures 4 to 6 are schematic diagrams of the structures of possible communication devices provided by embodiments of the present application. The communication device can be used to implement the functions of the RIS, network device, or UE in the above-mentioned method embodiments, and thus can also achieve the beneficial effects possessed by the above-mentioned method embodiments. In one possible implementation, the communication device can be a network device or UE as shown in Figure 1 or Figure 2, or a RIS as shown in Figure 2, or a module (such as a chip) applied to a UE, network device, or RIS. For relevant details and effects, please refer to the description of the aforementioned embodiments.

[0195] As shown in Figure 4 , communication device 400 includes a processing unit 410 and a communication unit 420 , wherein communication unit 420 may also be a transceiver unit or an input / output interface, etc. Communication device 400 may be used to implement the functions of a RIS, network device, or terminal device in the method embodiment shown in Figure 3 .

[0196] Exemplarily, when the communication device 400 is used to implement the function of the RIS in the method embodiment shown in FIG3 , the communication unit 420 is configured to send T1 reference signals reflected by a first subarray of the RIS to a network device, wherein the RIS includes M element arrays, the first subarray includes N element arrays of the M element 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; the communication unit 420 is further configured to receive third information from the network device, wherein the third information is used to indicate a first codebook, wherein the first codebook includes at least one weight value, and the at least one weight value is The weights of the multiple unit arrays are determined by the first codebook based on the T1 reference signals. The communication unit 420 is further configured to send T2 reference signals reflected by E unit arrays among the M unit arrays to the network device, where the T2 reference signals are used to estimate a cascade channel. 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 cascade channel and less than M, the cascade channel includes a channel between the network device and the RIS, and a channel between the RIS and the terminal device, and E is a positive integer less than or equal to M.

[0197] When the communication apparatus 400 is used to implement the functions of the network device in the method embodiment shown in FIG3 : the communication unit 420 is configured to receive T1 reference signals reflected by a first subarray of a RIS from a UE, where the RIS includes M element arrays, the first subarray includes N element arrays of the M element 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; the processing unit 410 is configured to estimate the angle domain diameter of the concatenated channel based on the T1 reference signals, and determine a first codebook based on the angle domain diameter, where the first codebook includes at least one weight, where the at least one weight is a weight of E element arrays of the M element arrays. The cascaded channel includes a channel between a 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, where the third information is used to indicate the first codebook, where the first codebook is used for the RIS to reflect a reference signal. The communication unit 420 is further configured to receive T2 reference signals from the UE reflected by the E element arrays, where 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 angle domain and less than M. The processing unit 410 is further configured to estimate the cascaded channel based on the T2 reference signals.

[0198] When the communication device 400 is used to implement the function of the UE in the method embodiment shown in Figure 3: the communication unit 420 is used to send T1 reference signals, and the T1 reference signals are reflected to the network device through the RIS, where T1 is a positive integer less than M, and M is the number of unit arrays included in the RIS; the communication unit 420 is also used to receive first information from the network device, where the first information is used to indicate the value of T2, and T2 is a positive integer less than M; the communication unit 420 is also used to send T2 reference signals, and the T2 reference signals are reflected to the network device through the RIS, and the T2 reference signals are used to estimate the cascade channel, where the cascade channel includes the channel between the network device and the RIS, and the channel between the RIS and the UE.

[0199] The terms and explanations of the terms involved in the above device embodiments can be found in the description of the aforementioned method embodiments and will not be expanded here.

[0200] The division of modules in the embodiments of the present application is illustrative and is merely a logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional modules in the various embodiments of the present application may be integrated into a single processor, or may exist physically separately, or two or more modules may be integrated into a single module. The aforementioned integrated modules may be implemented in the form of hardware or software functional modules.

[0201] As shown in FIG5 , a communication device 500 provided in an embodiment of the present application is used to implement the channel estimation method provided in the present application. The communication device 500 can be a communication device that applies the channel estimation method, or a component in a communication device, or a device that can be used in conjunction with a communication device. The communication device 500 can be a RIS, a network device, or a UE. Specifically, the communication device 500 can be a chip system or a chip. In the embodiment of the present application, the chip system can be composed of a chip, or can include a chip and other discrete devices. The communication device 500 includes at least one processor 520 for implementing the channel estimation method provided in the embodiment of the present application. The communication device 500 can also include an output interface 510, which can also be referred to as an input / output interface. In the embodiment of the present application, 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, transmission is performed with other chips or devices via the output interface 510. The processor 520 can be used to implement the method provided in the above method embodiment.

[0202] Exemplarily, the processor 520 may be used to execute actions executed by the processing unit 410 , and the output interface 510 may be used to execute actions executed by the communication unit 420 , which will not be described in detail.

[0203] 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. Coupling in the embodiments of the present application is an indirect coupling or communication connection between devices, units, or modules, which may be electrical, mechanical, or other forms, and is used 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.

[0204] In an embodiment of the present application, the memory 530 may be a non-volatile memory, such as a hard disk drive (HDD) or a solid-state drive (SSD), or may be a volatile memory, such as a random-access memory (RAM). A memory is any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory in the embodiment of the present application may also be a circuit or any other device that can implement a storage function, for storing program instructions and / or data.

[0205] In the embodiments of the present 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, and may implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of the present application. A general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of the present application may be directly implemented as being executed by a hardware processor, or may be executed by a combination of hardware and software modules in the processor.

[0206] As shown in Figure 6, a communication device 600 provided in an embodiment of the present application is used to implement the channel estimation method provided in the present application. The communication device 600 can be a communication device that applies the channel estimation method shown in the embodiment of the present application, or it can be a component in the communication device, or it can be a device that can be used in combination with the communication device. The communication device 600 can be a RIS, a network device, or a UE. Among them, the communication device 600 can be a chip system or a chip. In the embodiment of the present application, the chip system can be composed of a chip, or it can include a chip and other discrete devices. Part or all of the channel estimation method provided in the above embodiment can be implemented by hardware or by software. When implemented by hardware, the communication device 600 may include an input interface circuit 601, a logic circuit 602 and an output interface circuit 603.

[0207] Optionally, taking the device being used to implement the function of the receiving end as an example, the input interface circuit 601 can be used to execute the above-mentioned receiving action performed by the communication unit 420, the output interface circuit 603 can be used to execute the above-mentioned sending action performed by the communication unit 420, and the logic circuit 602 can be used to execute the above-mentioned action performed by the processing unit 410, which will not be repeated.

[0208] Optionally, the communication device 600 may be a chip or an integrated circuit in specific implementation.

[0209] Part or all of the operations and functions performed by the communication device described in the above method embodiments of the present application can be completed using a chip or an integrated circuit.

[0210] An embodiment of the present application provides a computer-readable storage medium storing a computer program, wherein the computer program includes instructions for executing the above method embodiment.

[0211] An embodiment of the present application provides a computer program product comprising instructions, which, when executed on a computer, enables the computer to execute the above method embodiment.

[0212] The present application provides a communication system. Specifically, the communication system may include at least two of a network device, a RIS, or a UE for implementing the method shown in FIG3 . For details, please refer to the relevant description in the above method embodiment, which will not be repeated here.

[0213] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0214] The present application is described with reference to the flow chart and / or block diagram of the method, device (system), and computer program product according to the embodiment of the present application. It should be understood that each flow process and / or box in the flow chart and / or block diagram and the combination of the flow process and / or box in the flow chart and / or block diagram can be realized by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processing machine or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for realizing the function specified in one flow chart flow or multiple flows and / or one box or multiple boxes of the block diagram.

[0215] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0216] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0217] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0218] Obviously, those skilled in the art may make various changes and modifications to the embodiments of the present application without departing from the embodiments and scope of the present application. Thus, if these modifications and variations of the embodiments of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations.

Claims

1. A channel estimation method, characterized in that: The method comprises: Sending T1 reference signals, wherein the T1 reference signals are reflected to the network device through the reconfigurable intelligent surface (RIS), where T1 is a positive integer less than M, and M is the number of unit arrays included in the RIS; receiving first information from the network device, where the first information is used to indicate a value of T2, where T2 is a positive integer less than M; T2 reference signals are sent, and the T2 reference signals are reflected to the network device through the RIS. The T2 reference signals are used to estimate a cascade channel, and the cascade channel includes a channel between the network device and the RIS, and a 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, where the second information is used to indicate a value of T1 or a value of N, where N is the number of unit arrays included in a first sub-array of the RIS, and the first sub-array is used to reflect the T1 reference signals, where 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 comprises: receiving T1 reference signals reflected by a first subarray of a RIS from a terminal device, wherein the RIS includes M element arrays, the first subarray includes N element arrays of the M element 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; estimating a diameter of a concatenated channel in an angle domain according to the T1 reference signals, and determining a first codebook according to the diameter in the angle domain, wherein the first codebook includes at least one weight, and the at least one weight is a weight of E unit arrays in the M unit arrays, the concatenated channel includes a channel between a network device and the RIS, and a channel between the RIS and the terminal device, and E is a positive integer less than or equal to M; Sending third information to the RIS, where the third information is used to indicate the first codebook, where the first codebook is used for a reflected reference signal of the RIS; receiving T2 reference signals from the terminal device reflected by the E element 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 angle domain and less than M; The concatenated channel is estimated according to 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 represents the first codebook, represents the new dictionary matrix of the angle domain obtained according to the first codebook, D r represents the original dictionary matrix of the angle domain, L represents the diameter of the angle domain, X H represents the conjugate transposed matrix of matrix X, and D(:,L) represents taking the L column vector 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 dimensions are N × R; or, The first sub-array is a planar array, Among them, D rH represents the row matrix, D rV represents the column matrix, D rH The dimensions are p×R, D rV The dimension of is q×R, the dimension of the first sub-matrix is ​​p×q, It means to find the Kronecker product of a and b; Wherein, R represents the resolution of the angle domain.

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

8. The method according to any one of claims 3 to 7, characterized in that Estimating the angle domain diameter of the concatenated channel according to the T1 reference signals includes: A compressed sensing algorithm is used to estimate the diameter of the angle domain according to the T1 reference signals.

9. The method according to any one of claims 3 to 8, characterized in that The method further comprises: Fourth information is sent to the RIS, where the fourth information includes one or more of the following: a value of N, the number of rows of the N unit arrays, or the number of columns of the N unit arrays.

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

11. A channel estimation method, characterized in that: The method comprises: Sending T1 reference signals reflected by a first subarray of a RIS to a network device, wherein the RIS includes M element arrays, the first subarray includes N element arrays of the M element 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 including at least one weight, the at least one weight being a 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; Sending T2 reference signals reflected by the E unit arrays to the network device, where the T2 reference signals are used to estimate a concatenated channel, wherein 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, and the concatenated channel includes a channel between the network device and the RIS, and a channel between the RIS and a terminal device.

12. The method according to claim 11, characterized in that The first codebook satisfies the following relationship: Among them, W Dr represents the first codebook, represents the new dictionary matrix of the angle domain obtained according to the first codebook, D r represents the original dictionary matrix of the angle domain, L represents the diameter of the angle domain, X H represents the conjugate transposed matrix of matrix X, and D(:,L) represents taking the L column vector 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 represents the number of unit arrays included in the first sub-array; or, The first sub-array is a planar array, Among them, D rH represents the row matrix, D rV represents the column matrix, D rH The dimensions are p×R, D rV The dimension of is q×R, the dimension of the first sub-matrix is ​​p×q, It means to find the Kronecker product of a and b; Wherein, R represents the resolution of the angle domain.

15. The method according to any one of claims 11 to 14, characterized in that: Receiving third information from the network device, including: receiving the first codebook from the network device; or, An index of the diameter of the angle domain in an original dictionary matrix of the angle domain is received from the network device.

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

17. The method according to any one of claims 11 to 16, characterized in that: The N unit arrays are continuous 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, so that the communication device performs the method according to any one of claims 1 to 2, or the communication device performs the method according to any one of claims 3 to 10, or the communication device performs the method according to any one of claims 11 to 17.

19. The communication device according to claim 18, wherein: The communication device further includes the memory.

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

21. A communication device, characterized in that: The method comprises a module for executing the method according to any one of claims 1 to 2, or a module for executing the method according to any one of claims 3 to 10, or a module for executing the method according to any one of claims 11 to 17.

22. A chip system, characterized in that: The chip system includes a logic circuit and an input / output interface, wherein the input / output interface is used to communicate with other communication devices outside the chip system, and the logic circuit is used to execute the method as described in any one of claims 1 to 2, or the logic circuit is used to execute the method as described in any one of claims 3 to 10, or the logic circuit is used to execute 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. When the computer program is run on a computer, the computer is caused to execute the method according to any one of claims 1 to 2, or the method according to any one of claims 3 to 10, or the method according to any one of claims 11 to 17.

24. A computer program product, characterized in that The computer program product includes a computer program, which, when executed on a computer, causes the computer to execute the method according to any one of claims 1 to 2, or causes the computer to execute the method according to any one of claims 3 to 10, or causes the computer to execute the method according to any one of claims 11 to 17.

25. A communication system, characterized in that: The invention comprises a communication device for executing the method according to any one of claims 1 to 2, a communication device for executing the method according to any one of claims 3 to 10, and a communication device for executing the method according to any one of claims 11 to 17.

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