The Synchronization Of SC-FDMA Systems Over Double-selective Channels

High rate and high quality communication under high-speed environment has become an urgent demand of people's life.However,the channel's complexity under high speed brings great challenge to communication systems.These huge demand and difficulties attract the attention of the LTE project team of 3GPP.In order to avoid the high power waste and cost lead by the high peak to average ratio(PAPR)of orthogonal frequency division multiplexing(OFDM)systems,single carrier frequency division multiple access(SC-FDMA)technology is applied to LTE's uplink.SC-FDMA system works well under frequency selective channels,but it is sensitive to the time selectivity of the channel,which is caused by high-speed movement.Channel's double selectivity under high speed mobile environment makes synchronization,especially the carrier frequency synchronization difficult to achieve,it has also become a bottleneck to restrict the improvement of system performance.This thesis first introduces the basic principle and the system structure of SC-FDMA,and then focus on the symbol synchronization and carrier frequency synchronization technology over double-selective channel.The symbol synchronization algorithm determines the symbol synchronization point by detecting the peak value of the timing measure function,which is mainly designed based on the correlation between the sequences,while the frequency synchronization is mainly through phase shift to estimate the frequency offset value and then synchronization achieved by frequency offset compensation.After the study of several kinds of commonly used synchronization algorithm,summarized the reasons why these algorithms can not work well in double-selective channel.This thesis proposed a symbol synchronization algorithm and an improved frequency offset estimation algorithm based on the cyclic prefix and Gaussian weighting idea.After these,another new frequency offset estimation algorithm is designed in response to the timevariation of the double-selective channel,which is based on the basis expansion model and the criterion of maximum likelihood estimation.At last,the shortcomings of the original method under double-selective channel are shown by the MATLAB simulation,and the performance advantages of the improved and designed new algorithm under double-selective channel are also illustrated by the simulation results.