Analysis Of The Performance Of High-speed Scattering Communication System Based On Frequency Switching

In the high-speed scattering communication system,the data in a coding block is spread to different frequencies for transmission through the frequency switching technology,which can effectively obtain the diversity gain.Based on the scattering channel,the thesis explains the common diversity techniques,and analyzes how the frequency switching technique can obtain the frequency diversity gain in the scattering communication.Then the thesis introduces the block fading channel,studies the upper bound of the transmitted signal in different numbers of fading blocks.In order to obtain higher transmission rate and spectrum efficiency,studying the related coding and modulation algorithm,and LDPC error correction coding close to the Shannon limit is adopted to improve the overall coding efficiency of the system.On the basis of frequency switching technology,the number of transceiver antennas is increased,and space and frequency diversity are obtained at the same time to improve system performance.1.The channel characteristics of high-speed scattering communication are introduced.Different from traditional communication technology,there are problems such as large path loss and multipath delay during the process of scattering communication.Therefore,it is necessary to adopt frequency switching technology to combat signal fading and obtain greater diversity gain.2.This thesis builds a high-speed scattering communication system simulation platform,including channel coding,rate matching,likelihood ratio calculation,frequency domain equalization,frequency switching and some other modules,and designs a reasonable frame structure.On the basis of this system simulation platform,this thesis compares a variety of LDPC decoding algorithms,and calculates soft demodulation information to improve the decoding performance of the system.The number of switching frequency points on this system performance is compared,and it is proved that when the number of switching frequency points increases,this system can obtain greater diversity gain.Under the condition that the number of switching frequency points remains unchanged,the channel coding of variable code rate is combined with various modulation schemes,then analyzing the influence of parameters such as modulation order and code rate on system performance.It is proved that low code rate combined with high-order modulation is better than high code rate combined with low-order modulation.3.By introducing MIMO technology and realizing multi-diversity signal transmission,this thesis analyzes the relationship of the system capacity and the number of antenna,studies the maximum achievable transmission rate by the system when the number of switching frequency points limited.Comparing and analyzing the relationship between the number of antennas and the number of switchable frequency points,it is proved that when the number of receiving antennas increases,a small number of switched frequency points can effectively reduce the system bit error rate.When the system rate is constant,this thesis combines STBC and frequency switching technology,realizes the signal space-time-frequency diversity transmission,the system performance has further improvement.