Research On The Synchronization Problem Of MIMO-OFDM Systems

MIMO-OFDM is a modulation technique which is getting more and more attention in recentyears. It is considered as a key technology in the4thgeneration mobile communication because ofits high transmission rate, high bandwidth efficiency, anti multi-path fading.But it is very sensitiveto synchronization. If synchronization can’t finish complete, system will introduce inter-symbolinterference (ISI) and inter-carrier interference (ICI), so that the system performance willdeterioration badly.In this paper，the main research goal is the synchronization of MIMO-OFDM. First of all,this paper introduced the MIMO-OFDM system model, advantages, key technology anddevelopment status of MIMO and OFDM,some classic algorithm of OFDM system. secondly, thispaper introduced two kind systems which are demarcated by the topological structure of thenetwork--the centralized MIMO-OFDM system and distributed MIMO-OFDM system, andintroduce their respective classical algorithm. This paper completes the work on these systems.After that, we introduces a classic sequence with good autocorrelation and correlation characteristic--Constant Amplitude Zero Auto Correlation sequences (CAZAC), and has been given theclassical algorithm using of CAZAC sequence as the training sequence, in which Zhang Jian-hua’sWPS algorithm for optimal. At last, this paper designed a training sequence--take half lengthCAZAC training sequence and it’s conjugate as a training sequence, and structures new pilotrespectively correspond to the centralized and distributed system, gives the correspondingimprovement algorithm. The simulation results show that the improved algorithm compares to theoptimal WPS algorithm and other algorithms, timing synchronization function peak is sharp. In thecentralized system, the algorithm can accurately determine timing synchronization point, in thedistributed system, also can accurately determine the different antenna timing synchronizationpoint, calculate inter time delay (ITD); At the same time, it’s frequency offset estimation value ofMSE than the WPS algorithm’s is slightly better, therefore, can be considered synchronousperformance of improved algorithm than the previous algorithm improved.