Research On Joint Time Delay And Angle Estimation For OFDM Signal

With the wide application of OFDM technology and the improvement of corresponding communication network,while people are enjoying the data service provided by OFDM technology,the demand for wireless target location information in the military and civilian fields is also increasing.The wireless location parameter estimation technology is gradually developing towards the multi-dimensional,joint and efficient direction.In recent years,the joint estimation of two-dimensional parameters of time delay and angle has attracted much attention because of its remarkable advantages in improving the accuracy of parameter estimation and reducing the number of receiving nodes.It has important theoretical value and application prospects to carry out joint estimation of OFDM signal delay and angle parameters with high accuracy and good performance.In order to improve the accuracy and timeliness of parameter estimation,this paper focuses on the time-varying characteristics of OFDM signals and the wireless multipath environment.Considering the relative size between the number of receiving elements and the number of multipath,the number of sampling snapshots,the accuracy of parameter estimation,the complexity of calculation etc.,the joint estimation methods of time delay and angle for multi-snapshot multi-element,multi-snapshot few-element and single snapshot data are studied in depth to meet the requirement of positioning system efficiency.The main contributions are as follows:1.For stationary or slow time-varying target signals,when the number of multipath is less than the number of array elements,the time delay and angle of arrival parameters can be estimated by the two-dimensional Multiple Signal Classification(2D-MUSIC)algorithm.However,this algorithm needs much time to complete the two-dimensional pseudo spectral peak search,which makes it difficult to apply in practice.Aiming at solving this problem,a fast joint estimation algorithm of time delay and angle based on Hadamard product is proposed.Firstly,according to the channel frequency domain response vectors on each array element,the channel frequency domain response estimation vectors are constructed,which include the Hadamard product of location parameter information.Then,the autocorrelation matrix and noise subspace are computed,and the polynomials of time delay and angle are constructed respectively to solve the closed-form solution.Finally,the fast joint estimation of time delay and angle parameters is realized by using parameter paring method.The simulation results show that the proposed method can obtain high accuracy of parameter estimation while significantly reducing the computational complexity,and has certain adaptability to multipath environment,and improves the ability of rapid acquisition of positioning parameters.2.In order to make full use of the advantages of two-dimensional information and further improve the performance of parameter estimation without greatly increasing the complexity,a joint estimation algorithm of time delay and angle based on orthogonal matrix characteristics is proposed.First of all,according to the intrinsic relationship of signal data model,we first use rotation factor to estimate angle parameters.Then,the corresponding time delay vector matrix is constructed by using column corresponding attributes of orthogonal matrix operations and exchange rules.Finally,the delay parameters are obtained by solving the diagonal elements.The two-dimensional parameters are solved by closed-form solution and paired automatically,which improves the efficiency and accuracy of pairing.Simulation results show that the proposed algorithm has higher estimation accuracy and better performance than the existing algorithms at low SNR.3.For stationary or slow time-varying target signals,when the number of multipaths is larger than the number of array elements,the method of independent estimation of delay and angle parameters and parameter pairing can no longer complete angle parameter estimation.In order to avoid two-dimensional peak searching,a joint estimation algorithm of time delay and angle based on modified propagation operator is presented according to the characteristics of wave path phase shift between two array elements.Firstly,the vector dimension of channel frequency response estimation is extended.Then,the modified propagator operator algorithm is used to estimate the time delay parameters.Finally,the angle parameters are calculated by the same eigenvector relation matrix,therefore the joint estimation of time delay and angle parameters is realized.The algorithm needs neither covariance decomposition nor peak searching.The delay and angle parameters are obtained by closed-form solution,and the two-dimensional parameters can be automatically paired.Simulation results show that the proposed algorithm not only significantly reduces the computational complexity,but also can achieve high precision parameter estimation when the number of multipath is greater than and equal to the number of array elements.4.For the short-time burst signal or fast motion signal,the valid data received is only a single snapshot or several snapshots.A single snapshot or small sample data can only provide limited amount of information so that the rank of covariance matrix is not full,which is not adopted to complete the parameter estimation directly using the traditional super-resolution method.Aiming at solving the problem,a joint estimation algorithm of time delay and angle using matrix pencil based on information reconstruction vector is proposed.Firstly,according to the channel frequency response vectors on each array element,the data with time delay and angle parameter information vectors are reconstructed from two dimensions of frequency and space.Then,the enhanced data matrix of the extended array element is constructed,and the parameter vectors of the delay and angle are estimated by the two-dimensional matrix pencil algorithm.Finally,the joint estimation of two-dimensional parameters of time delay and angle is realized by parameter pairing.Simulation results show that the proposed algorithm has higher accuracy in parameter estimation and has a certain application value.5.A single snapshot or small sample data make the subspace class location parameter estimation algorithm based on covariance matrix invalid,and two-dimensional matrix pencil algorithm still needs parameter pairing after angle and delay parameters are obtained respectively.Aiming at solving the problem,a joint estimation algorithm of first-arrival path delay and angle based on generalized inverse eigenvalue is proposed.Firstly,the algorithm estimates the minimum delay parameters,and then calculates the angle of arrival parameter of the target signal through the eigenvector relationship,which can thus avoid the parameter pairing process,significantly reduce the complexity,and achieve better parameter estimation performance.Simulation results verify the effectiveness of the proposed algorithm and relatively improve the computation efficiency of parameter acquisition.