Research And Application Of MIMO-OFDM System Synchronization Method

Due to the characteristics of increasing channel capacity and reducing bit error rate,multiple input multiple output(MIMO)technology has attracted wide attention and application.The massive MIMO technology is the development of traditional MIMO technology.As one of the key technologies of 5G,it can improve the spectrum efficiency and power efficiency of the system effectively.In practical applications,MIMO technology is often combined with the orthogonal frequency division multiplexing(OFDM)technology.Through taking advantage of the characteristics of OFDM technology,such as high spectrum utilization and strong anti-interference ability,the performance of the communication system is promoted significantly.Synchronization is the key factor that affects the performance of the MIMO-OFDM system,and the effective improvement of the synchronization technology is the fundamental guarantee for enhancing the stability performance of the system.In this paper,the synchronization algorithms of pilot structure and cyclic prefix structure of the MIMO-OFDM system were studied,as well as the synchronization method of massive MIMO-OFDM system.The main research contents are as follows:Firstly,an improved synchronization method is proposed for the pilot structure and algorithm of the MIMO-OFDM system.Based on GCL sequence and Minn algorithm prototype,a new pilot structure is designed.First,the algorithm is improved through the introduction of pseudo-noise(PN)taking positive 1 or negative 1,and the location of timing synchronization is obtained by using decision function.Then,the average value of the frequency offset is gained by conducting the correlation calculations twice.Thus timing synchronization accuracy and frequency offset become more accurate.The simulation results show that the improved pilot structure and algorithm have good performance in timing synchronization and frequency offset estimation.Then,an improved synchronization method of cyclic prefix(CP)structure and algorithm is proposed.Structurally,the CP is divided into three parts.The head of the previous OFDM symbol is copied to the first part,and the tail of the current OFDM symbol is copied to the other two parts.The average value of the second part is calculated before conducting its correlation calculation,and the PN sequence is introduced before the correlation calculation is carried out in the third part.At last,the symbol timing synchronization position and frequency offset estimation are derived based on the second and the third parts.The simulation results reveal that the improved CP structure and algorithm can improve the synchronization performance of the system while the calculated amount is reduced.Finally,a synchronization method of joint pilot and CP of the massive MIMO-OFDM system is presented.First,the initial frequency offset is obtained through the correlation of time domain pilots.Then the frequency compensation of the received data is made.And the frequency offset is then further obtained according to the correlation of CP.At last,the accurate frequency offset value relatively is obtained through the calculation of the average value of the two results.The simulation results indicate that the synchronization performance of the system is improved by the improvement of the algorithm.