Research On The Key Technologies Of Scattering Communication Base On SC-FDMA

Troposcatter communication is an important wireless remote communication method,which has the advantages of anti-destruction and strong security.However,the scatter channel has a large transmission path loss,resulting in the system may work at low SNR regions,and it has time-frequency selective fading.Its channel fading is a fast time-varying non-stationary signal.Hence,studying a communication scheme to make the scattering communication transmit stably.Based on the characteristics of the channel,SC-FDMA with time-frequency combination structure is selected as the communication system,and the key technologies of the system are studied.In this thesis,two time-frequency analysis methods,FRFT and DCT are applied in the SC-FDMA system to improve its performance.The main research content is divided into three parts:(1)Analyze the characteristic of scatter channel.The large-scale parameter such as fading depth and median level,as well as small-scale parameter such as root mean square delay spread and Doppler spread can be obtained from the measured Zadoff-Chu sounding sequences.(2)the frame structure and parameters of SC-FDMA system are determined according to the scatter channel.And the effects of channel coding,frequency offset estimation,SNR estimation,channel estimation and equalization,subcarrier mapping and combining techniques on the system performance are investigated,and the corresponding optimal algorithm is obtained.link adaptation is discussed,in which the switching control scheme based on look-up table can effectively improve the system throughput compared with the fixed MCS.(3)The communication system structure FRFT-SCFDMA and DCT-SCFDMA based on new time-frequency analysis method are studied,which is simulated and compared with the traditional FFT-SCFDMA system.Simulation results show that the performance of FRFT-SCFDMA is superior to DCT-SCFDMA and FFT-SCFDMA successively,regardless of whether there is a carrier frequency offset in the system.Meanwhile,the order of FRFT-SCFDMA with the best performance is inconsistent under different conditions.For different application scenarios,the order of FRFT is adjusted to optimize the performance of the communication system.