A two-dimensional DFT double-point ratio-based DoA estimation method for a symbiotic radio system

Abstract

The application belongs to the field of signal processing and discloses a DoA estimation method based on two-dimensional DFT double-point ratio for a symbiotic radio system: (1) according to a single sample receiver signal y R obtaining an interference-free two-dimensional DFT spectrum Z; (2) sorting all elements in the two-dimensional DFT spectrum Z, finding the maximum value and the adjacent row maximum value and column maximum value, and then obtaining the to-be-estimated DoA according to the three maximum values. The application realizes high-precision DoA estimation by using a single signal sample, can resist interference in the symbiotic radio system, has good mobile target scene adaptability, and provides a feasible method for efficient positioning of the symbiotic radio system.

Description

Technical Field

[0001] The present invention relates to the field of wireless communications, and in particular to a DoA estimation method based on a two-dimensional DFT double-point ratio for a symbiotic radio system. Background Art

[0002] Thanks to the convergence of IoT and modern communications technologies, the scale of applications in vertical industries such as smart agriculture, smart logistics, and smart homes continues to expand. The massive influx of connected devices has led to high hardware costs, high energy consumption, and limited spectrum resources. Consequently, symbiotic radio technology has garnered widespread attention in recent years. Secondary communication systems share the hardware, energy, and spectrum resources of existing wireless communication systems, transmitting information from passive IoT devices using low-power reflection modulation. This system also provides additional multipath gain to enhance the performance of active systems, creating a mutually beneficial ecosystem for primary and secondary communication.

[0003] In many Internet of Things application scenarios, on the one hand, the network access nodes and the control system need to maintain reliable communication cooperation, such as interacting with the information of the goods, uploading the sensing data and feeding back the device information, and on the other hand, the control system also needs to timely and quickly grasp the position and motion state of the Internet of Things nodes, so as to realize the applications such as cargo positioning, personal luggage identification and positioning, breeding management and home device control. Under the driving of the dual application requirements of high-efficiency communication and perception of the Internet of Things, the research of the integrated technology of communication and perception is imminent. In the research of perception positioning, the parameter estimation based on the direction of arrival (DoA) is widely used due to its excellent anti-interference performance, including the discrete Fourier transform (DFT), the multiple signal classification algorithm (MUSIC) based on the signal subspace and the estimating signal parameters via rotational invariance techniques (ESPRIT) algorithm. For example, the Chinese patent with the publication number CN111413668A discloses a DOA estimation method based on DFT enhancement in a large-scale array, which obtains accurate estimation of the DOA through the combination of DFT and Taylor expansion algorithm. The Chinese patent with the publication number CN111342876A discloses a LTE uplink signal DOA estimation method based on the MUSIC algorithm, which uses a multi-antenna array to receive the LTE uplink signal, separates the PUSCH signal of the user equipment after the CP and FFT processing, and then inputs it into the MUSIC algorithm estimation module to calculate the DOA. The Chinese patent with the publication number CN discloses an ESPRIT-DOA estimation method in a mixed noise environment of a co-prime array; receives the signal using the co-prime array antenna to obtain the received signal; calculates the corresponding phase fraction low-order moment estimation matrix and the symbol covariance matrix; then performs virtualization operation on the obtained estimation covariance matrix to obtain the virtual uniform linear array receiving signal with a half-wavelength array element spacing; then performs spatial smoothing processing to obtain the reconstructed covariance matrix; finally, the DOA estimation can be obtained by processing through the ESPRIT method.

[0004] When considering the mobility of passive devices, the widely used perception method based on the signal subspace cannot be applied to the mobile scene because it needs to estimate the covariance matrix based on a large number of samples in the same space. Although the DFT algorithm can be executed based on a single sample, its accuracy is greatly limited by the number of search points, resulting in poor estimation performance. SUMMARY

[0005] The application aims to provide a DoA estimation method based on two-dimensional DFT double-point ratio for a symbiotic radio system, which realizes high-precision DoA estimation with single signal sample.

[0006] The application adopts the following technical solutions:

[0007] A DoA estimation method based on two-dimensional DFT double-point ratio for a symbiotic radio system, the symbiotic radio system comprising a single-antenna base station, a K x ×K y dimensional uniform planar antenna array receiver, and an intelligent reflecting surface (IRS), wherein the IRS comprises N x ×N y dimensional independent reflecting subarrays;

[0008] The DoA estimation method comprises the following steps:

[0009] (1) obtaining an interference-free two-dimensional DFT spectrum Z according to a single-sample receiver signal y R

[0010] (2) sorting all elements in the two-dimensional DFT spectrum Z, finding the maximum value and its adjacent row maximum value and column maximum value, and then obtaining the DoA to be estimated according to the three maximum values;

[0011] Further, in step (1), the interference-free two-dimensional DFT spectrum Z is obtained according to y R

[0012] (1-1) performing two-dimensional DFT transformation on y R to obtain a two-dimensional DFT spectrum Z;

[0013] (1-2) removing the interference of the base station signal from the two-dimensional DFT spectrum Z.

[0014] Further, in step (1-1), the two-dimensional DFT transformation is performed on y R

[0015]

[0016] wherein Abs(X) is an operation of taking the modulus of each element of a matrix X, is a two-dimensional DFT matrix, each element of which is represented as:

[0017]

[0018] wherein i=1,…K x ,j=1,…K​​​y diag(a) denotes diagonalization of vector a, denotes the conjugate transpose operation of , θ BR,x is the effective DoA angle between the base station and the receiver in the x-axis direction, θ BR,y is the effective DoA angle between the base station and the receiver in the y-axis direction.

[0019] Further, the first row and the first column element z 1,1 contains interference from the base station signal, and the method for removing the interference is:

[0020]

[0021] where [WY R ] 1,1 is the first row and the first column corresponding element of WY R , α BR represents the complex gain of the channel between the base station and the receiver. Further, in step (2), the method for obtaining the to-be-estimated DoA is:

[0022] Sort all the elements in the two-dimensional DFT spectrum Z without interference, and let

[0023] The corresponding maximum value is denoted as The maximum value adjacent to in the J1th column is denoted as The maximum value adjacent to in the I1th column is denoted as The maximum value adjacent to

[0024] The angles θ and θ are estimated by the following relationship: τ,x τ,y

[0025]

[0026] where k x and k y are integers satisfying and

[0027] wherein the two-dimensional DFT spectrum Z is periodic, and thus when I1=1, I1-1=K x -1; when I1=K x , I1+1=1; when J1=1, J1-1=K y -1; and when J1=K y , J1+1=1.​​J1+1=1.

[0028] where h BR can be obtained by conventional channel estimation methods, and thus θ BR,x and θ BR,y are known a priori.

[0029] The DoAs to be estimated are contained in the channels between the IRS-receivers, and the single-sample receiver signal y R is the received signal of the incident signal through the channels between the IRS-receivers, and thus the DoAs to be estimated can be recovered from the single-sample receiver signal y R .

[0030] In the present application, for downlink transmission, the single-sample receiver signal y R of the co-existing radio system is represented as:

[0031]

[0032] where s B represents the information of the primary system base station, s I is the information of the secondary system IRS, and has the same symbol rate as s B ; is the base station transmit power; n R is the noise of the receiver; v R is the Doppler shift; j is a complex number h BR , H IR , and h BI are the channels between the base station-IRS, IRS-receiver, and base station-receiver, respectively.

[0033] where, for ease of illustration, it can be assumed that s B is binary phase modulation, i.e., s B = ±1.

[0034] In the present application, the channels between the base station-IRS, IRS-receiver, and base station-receiver in the co-existing radio system are modeled as:

[0035]

[0036]

[0037]

[0038] where α τ represents the complex gain of the corresponding channel, and τ ∈ {BI, BR, IR}; where is the Kronecker product, d represents the distance between adjacent antennas, usually set to half the wavelength d = λ / 2; θ τ,x and θ τ,y are the effective DoA angles along the x and y axes, respectively, where θ RI,x and θ RI,y is the DoA to be estimated.

[0039] The symbiotic radio system is considered to operate in the millimeter wave band, so the line-of-sight path is dominant and the device size is ignored, thereby performing the above modeling.

[0040] Compared with the existing technology, the DoA estimation method provided by the present invention uses a single signal sample to achieve high-precision DoA estimation. It can not only combat interference in symbiotic radio systems, but also has good adaptability to mobile target scenarios, providing a feasible method for efficient positioning of symbiotic radio systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 FIG. 4 is a comparison between the DoA estimation method based on two-dimensional DFT double-point ratio in an embodiment of the present invention and the existing DoA estimation method. DETAILED DESCRIPTION

[0042] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings and examples.

[0043] In this embodiment, the symbiotic radio system includes a base station configured with a single antenna, a base station configured with K x ×N y A receiver with a 3D uniform planar antenna array and an intelligent reflecting surface (IRS), wherein the IRS contains N x ×N y Dimensional independent reflection array.

[0044] In this embodiment, considering operation in the millimeter wave band, line-of-sight paths are dominant. Ignoring device size, the channels between the base station and the IRS, between the IRS and the receiver, and between the base station and the receiver in the symbiotic radio system can be modeled as follows:

[0045]

[0046]

[0047]

[0048] where α τ represents the complex gain of the corresponding channel, τ∈{BI,BR,IR}; in is the Kronecker product, d denotes the distance between adjacent antennas, usually set to half wavelength d = λ / 2; θ τ，x and θ τ,y are the effective DoA angles in x and y axis directions, respectively, where θ RI,x and θ RI,y are the DoAs to be estimated.

[0049] For a coexisting radio system, the received signal at the receiver for downlink transmission can be expressed as:

[0050]

[0051] where s B denotes the information of the primary system base station, for ease of presentation and illustration, it is assumed to be binary phase modulation, i.e., s B = ±1; s I is the information of the secondary system IRS, satisfying E[|s I | 2 ] = 1, and has the same symbol rate as s B ; is the transmit power of the base station; n R is the noise at the receiver; v R is the Doppler shift; and j is the imaginary unit

[0052] The method for recovering the DoA of the received signal at the receiver, i.e., the DoA estimation method, is as follows:

[0053] (1) Obtain the interference-free two-dimensional DFT spectrum Z R from y

[0054] (1-1) Perform two-dimensional DFT transformation on the single signal sample y R to obtain the two-dimensional DFT spectrum Z

[0055]

[0056] where Abs(X) is an operation of taking the modulus of each element of the matrix X, is a two-dimensional DFT matrix, each element of which can be expressed as:

[0057]

[0058] where i = 1, …, K x , j = 1, …, K y . The channel h BR can be obtained by a conventional channel estimation method, and thus θ BR,x and θ BR,y are considered to be known a priori.

[0059] (1-2) Removing the interference of base station signals from the two-dimensional DFT spectrum Z

[0060] The analysis finds that the first row and the first column elements of Z are z 1,1 The interference from the base station signals is included, and in order to eliminate the interference, the following operations can be performed:

[0061]

[0062] where [WY R ] 1,1 is the first row and the first column corresponding elements of WY R .

[0063] (2) Estimating the two-dimensional DoA: θ τ,x and θ τ,y

[0064] All elements in Z are sorted, and let the corresponding maximum value be the maximum value adjacent to in the J1th column be the maximum value adjacent to in the I1th column be Since the DFT spectrum is periodic, when I1=1, I1-1=K x -1; when I1=K x , I1+1=1; when J1=1, J1-1=K y -1; when J1=K y , J1+1=1. By using and θ τ,x and θ τ,y angles can be estimated by the following relationship:

[0065]

[0066] where k x and k y are integers satisfying and .

[0067] The performance and advantages of the two-dimensional DFT double-point ratio-based DoA estimation algorithm proposed in the application are verified by simulation results. The technical effects achieved by the embodiments are:

[0068] Figure 1 The two-dimensional DFT double-point ratio-based DoA estimation method proposed in the application is compared with existing methods, including the traditional DFT search method, the MUSIC method and the ESPRIT method.

[0069] Without loss of generality, taking the mean square error (MSE) of θ RI,x as an example, the simulation conditions are: N x =N y =8, the channel complex gain is set as |α IR |=|α IB |=0.1, K x =16, And the number of iterations of all methods is consistent. It can be found that the DoA estimation method provided by the present application is superior to the MUSIC method and the ESPRIT method in the entire transmit signal-to-noise ratio range, but is inferior to the DFT search method in the low transmit signal-to-noise ratio area. This phenomenon can be explained as follows: since the DoA estimation method provided by the present application needs the peak value and the second largest value of the DFT spectrum, and the second largest value is easily affected by noise in the low transmit signal-to-noise ratio area, the error is larger compared with the DFT search algorithm which only uses the maximum value. However, the accuracy of the DFT search method is seriously limited by the number of searches, while the MSE of the DoA estimation method provided by the present application is always decreasing with the increase of the transmit signal-to-noise ratio. Overall, the above results demonstrate the performance advantage of the DoA estimation method provided by the present application.

[0070] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be covered within the protection scope of the present application.

Claims

1. A two-dimensional DFT-based two-point ratio method for DoA estimation for a symbiotic radio system, characterized in that, The described coexisting radio system comprises a single-antenna configured base station, a K x ×K y dimensional uniform planar antenna array, and an intelligent reflecting surface, IRS, wherein the IRS comprises N x ×N y dimensional independent reflecting elements; The DoA estimation method comprises the following steps: (1) According to the single sample receiver signal y R Obtain the interference-free two-dimensional DFT spectrum Z; (2) sorting all elements in the two-dimensional DFT spectrum Z, finding the maximum value and its adjacent row maximum value and column maximum value, and then obtaining the to-be-estimated DoA according to the three maximum values; In step (1), according to y R The method for obtaining the interference-free two-dimensional DFT spectrum Z is: (1-1) for y R The two-dimensional DFT spectrum Z is obtained by performing a two-dimensional DFT transform. (1-2) removing the interference of the base station signal from the two-dimensional DFT spectrum Z; In step (2), the method for obtaining the to-be-estimated DoA is: Sort all elements in the interference-free two-dimensional DFT spectrum Z, let The corresponding maximum value is denoted as The maximum value in the J1th column adjacent to The maximum value is denoted as The maximum value in the I1th column adjacent to The maximum value is denoted as By using and θ IR,x and θ IR,y θ IR,x and θ IR,y the estimates of the DoAs, θ and are obtained by the following relations, respectively: wherein k x and k y are integers satisfying and θ BR,x is the effective DoA angle in the x-axis direction between the base station and the receiver, and θ BR,y is the effective DoA angle in the y-axis direction between the base station and the receiver.

2. The method of claim 1, wherein the method is a two-dimensional DFT-based two-point ratio method for a coexisting radio system. In step (1-1), y R is subjected to a two-dimensional DFT transform: where Abs(X) is the operation of taking the modulus of each element of matrix X, is a two-dimensional DFT matrix whose elements are given by: where i = 1,... K x j = 1,... K y diag(a) denotes the diagonalization of the vector a, denotes the conjugate transpose operation on ; wherein wherein is a Kronecker product and d denotes the distance of adjacent antennas.

3. The method of claim 1, wherein the method is a two-dimensional DFT-based two-point ratio method for a coexisting radio system. The first row first column element z of the two-dimensional DFT spectrum Z 1,1 The method for removing the interference from the base station signal is: where [WY R ] 1,1 is the first row first column pair element of WY R is the base station transmit power, a BR represents the complex gain of the channel between the base station and the receiver.​ 4. The method of claim 2, wherein the method is a two-dimensional DFT-based two-point ratio method for a coexisting radio system. The channels between the base station-IRS, the IRS-receiver and the base station-receiver of the symbiotic radio system are respectively: where α τ represents the complex gain of the corresponding channel, τ ∈ {BI, BR, IR}; d is set to half the wavelength λ / 2.

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