Research On Technology Of Turbo Frequency Domain Equalization In Wireless Communication

With the development of the communication industry,various new communication methods gradually affect people's daily life,especially the development of wireless communication technology,which greatly enriches people's lifestyle.In the case of a harsh mobile communication channel,Inter symbol interference(ISI)caused by multi-path effect is still a major problem for communication systems.We usually use techniques such as equalization,spread spectrum,and multi-carrier modulation to counteract ISI.However,in the case of a harsh communication channel,the traditional frequency domain equalization technology can not meet the performance requirements of the system.By combining Turbo code technology,Turbo equalization technique is proposed.Turbo equalization technology can improve the performance of the system by exchanging soft information between the equalizer and the decoder through multiple iterations.This paper takes the single-carrier frequency domain equalization system as the research object,and mainly studies the Turbo frequency domain equalization technology of this system.First,the wireless channel model and single-carrier frequency domain equalization system are introduced in this paper,and the commonly used Turbo time domain equalization technology is analyzed and simulated.The next step is to focus on the key technologies of Turbo frequency domain equalization.The main research contents and contributions are as follows:1.The MMSE-based Turbo frequency domain equalization technology is theoretically analyzed and deduced in detail,and the algorithm flow is given in this paper.Then the performance of the MMSE-based Turbo time and frequency domain equalization technologies are compared.Furthermore,the frequency domain analyses of two timedomain approximate MMSE-Turbo equalization algorithms are presented,and the frequency domain expression and algorithm flow of two approximate MMSE-Turbo equalization algorithms are given in this paper.Finally,the performance simulations of these three Turbo frequency domain equalization algorithms are carried out and analyzed.Although the two approximation algorithms have some performance loss compared with the original algorithm,they reduce the complexity of the algorithm.The two approximation algorithms are used in combination,and the performance of the original algorithm can be approximated after multiple iterations.In addition,the complexity of the algorithm is reduced compared with the original algorithm2.The Turbo frequency domain equalization algorithm for time-varying channels is analyzed in this paper,and a frequency domain equalization algorithm based on subblock processing is introduced.In addition,by applying the frequency domain equalization algorithm to the Turbo frequency domain equalization system,this paper proposes a front-and-back block compensation Turbo frequency domain equalization algorithm and analyzes the performance by simulations.In time-varying channels,the front-and-back block compensation Turbo frequency domain equalization algorithm increases the computational complexity,but effectively improves the performance of the system.3.In this paper,the channel estimation and Turbo equalization techniques are jointly processed,the channel iterative frequency domain equalization processing system model is given,and the frequency domain channel iterative algorithm is analyzed in detail.In addition,two corrections are given based on the algorithm.One is to use the full information fed back by the decoder instead of the traditional external information for channel iterative estimation.The other is to use the mean of the known unique word(UW)sequence replace the partial mean of the feedback from decoder.While iteratively estimating the channel response,this paper considers the channel noise iterative method to estimate the variance of the noise in the channel.Finally,the error analyses and performance simulations of the channel iterative system under the algorithm are carried out.The modified channel iterative algorithm improves system performance without increasing system complexity.