| MIMO technique can make good use of time-space domain and frequency domain characteristic of signal to against flat fading channel efficiently, but it has no benefit in frequency elective fading channel. Frequency elective fading channel can be changed into flat fading channel by OFDM technique. The combination and complementation of MIMO and OFDM techniques can solve the problems of multi-path fading in channel and band efficiency of future wireless broadband telecommunication system, can also improve the capacity and transmission reliability of the system. MIMO-OFDM technique has become one of the most promising techniques of the forth generation mobile communication system.MIMO-OFDM system has the same problems of OFDM, they are high peak to average ratio caused by sub-carrier overlapping and frequency offset causing synchronization problem. High peak to average ratio and synchronization problems limit the application of MIMO-OFDM technique. It is necessary to study the techniques of reducing high peak to average ratio and solving synchronization problem in MIMO-OFDM system.In the research of reducing high peak to average ratio, the improved pulse shaping technique is proposed by the analysis of partial transmission sequence and pulse shaping techniques. By MATLAB simulation, it is got that the improved pulse shaping technique has good performance of reducing high peak to average ratio of MIMO-OFDM system. The comparison of the three techniques computation complexity is analyzed and given.In the research of synchronization problem, giving the analysis of the influence of frequency offset on MIMO-OFDM system and the selection of preamble sequence. The improved complete complementary sequence is introduced to MIMO-OFDM system as preamble sequence, by using synchronization algorithm to estimate and compensate frequency offset, the synchronization of MIMO-OFDM system is solved efficiently. |
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