The Research Of MIMO-OFDM System Compressed Sensing Sparse Reconstruction Algorithm

The development of analog communication system to digital communication system is a major change in the field of mobile communications.With the demand for high-speed and high-capacity data transmission,communication transmission technology is also developing.Orthogonal Frequency Division Multiplexing(OFDM)technology to effectively improve the channel utilization,Multiple Input Multiple Output(MIMO)technology to make full use of space resources and improve channel capacity.However,in the actual channel,OFDM technology is very sensitive to the time and frequency of the wireless communication system.Especially the application of MIMO technology will increase the seriousness of this problem.If the receiver accepts accurate wireless channel characteristics can reduce the distortion,so the channel estimation technology is particularly important.Aiming at some problems existing in the real transmission signal system,this paper first studies the traditional pilot estimation algorithm,and then studies the estimation algorithm based on Compressed Sensing(CS).The main research work and innovative research results are as follows:(1)OFDM channel estimation based on Discrete Fourier Transform(DFT).Against the problem that the DFT only improves the sample point noise outside the CP without taking into account the problem of noise within the CP,a new algorithm to improve the threshold is proposed.The idea of the new algorithm is to first take the average of the energy of the sample points in the CP,and take the mean of the energy on the appropriate interval after ascending the energy of the sample outside the CP,then take the sum of the two as the threshold of this paper.The simulation results show that the new threshold method adopted in this paper can improve the performance of the system.(2)Research on MIMO-OFDM system channel estimation for CS reconstruction algorithm.The traditional channel estimation algorithm needs for a large number of pilot to achieve high accuracy of the channel characteristics which resulting in low spectrum utilization,pilot pollution serious problem.Using MIMO-OFDM system in the time domain sparse characteristics,the use of CS the simulation results show that the number of pilots used in CS reconstruction signal method is much less than that of using traditional pilot parameters when obtaining the same accuracy performance.(3)Research on MIMO-OFDM sparse channel estimation for Gradient Pursuit(GP).In order to improve the much high computational complexity causing by dealing with a large number of least squares calculations,when orthogonal performance tracking and its improved algorithm are used to deal with large-scale data.The gradient tracking and reconstruction method used to estimate the channel performance of MIMO-OFDM systems.The algorithm uses the gradient idea to select the atoms,avoids the calculation of the least squares,and improves the computational complexity while ensuring the estimation accuracy of the channel,thus improving the system estimation performance.The simulation results show that the computational complexity of the method based on GP method is lower than that of OMP method.