Research On Isi Signal Detection Technology In Wireless Communication System

With the rapid development of wireless mobile communication,the demand for highspeed signal transmission is increasing.In order to transmit more data in limited bandwidth,the technique of Faster-Than-Nyquist transmission and the theory of overlapping X division multiplexing are proposed.These technologies effectively improve the utilization efficiency of spectrum,but Inter-Symbol Interference(ISI)is artificially introduced due to their violation of Nyquist criterion.In addition,in the signal transmission process of wireless communication system,due to the influence of scattering and reflection,the received signal has ISI after multiple paths propagation,which seriously affects the signal quality.In order to eliminate the influence of the above ISI,it is necessary to use equalization technology and corresponding detection algorithm at the receiver.This thesis systematically studies the key technology of signal detection under the influence of multiple ISI.The main contents and innovation of this thesis are as follows:Firstly,the existing ISI signal detection technology is analyzed.Its basic principle is to use the constraint relationship of known interference and the matrix eigenvalue decomposition detection algorithm to recover the transmitted signal,but the performance of the algorithm decreases with the severity of ISI.For the poor performance of matrix eigenvalue decomposition detection algorithm in dealing with multiple interference in multipath channel,this thesis proposes a frequency domain equalization combined with Viterbi detection algorithm.The simulation results show that the system performance has been improved.This thesis also studies the system performance of zero forcing algorithm and minimum mean square error algorithm in frequency domain equalization.The zero forcing algorithm does not consider the influence of noise,so its performance is slightly worse than that of the minimum mean square error algorithm.However,the artificial ISI has a greater impact on multiple interference,so the performance gap of different algorithms for frequency domain equalization is not obvious.To further improve the performance of the system,this thesis proposes a multipath ISI signal detection algorithm based on trellis structure.Through simulation,it is found that the system performance of this algorithm is further improved than the above frequency domain equalization combined with Viterbi detection algorithm.In addition,for the case of whether the channel estimation is perfect,this thesis analyzes the system performance of the two proposed algorithms.The results show that the imperfect channel estimation will degrade the performance of both algorithms,but whether the channel estimation is perfect or not has a greater impact on the algorithm that based on trellis structure.Finally,due to the high computational complexity of the proposed two detection algorithms,this thesis studies the receiving and detection algorithm of ISI signal under the condition of low complexity,and proposes a detection algorithm based on ordered successive interference cancellation structure.The simulation results show that the performance of this algorithm is better than the first two detection algorithms under the same low complexity conditions.So it is a low complexity algorithm that can be applied to multiple ISI signal detection,and it makes up for the poor performance of joint detection algorithm and trellis-based structure detection algorithm under the condition of low complexity.