Collaborative Communication System Of Frequency And Time Synchronization Technology In Research

Cooperative communicaton is an emerging technique which single-antennaterminals share their antennas in a special way to transmit information through a virtualmulti-antenna environment. In this situation, it employs distributed spatial diversity tocombat the deep fading. With the growing demand for high transmission rate of wirelesscommunication in recent years, how to improve the spectral efficiency in limitedresources become a hot spot in wieless communication fields. But, due to hardwarelimitation, MIMO system can not be applied to portable terminals. Therefore,Cooperative communication technique aroused extensive attention.In this dissertation, both frequency and timing synchronization of cooperativecommunication have been studied. Frist of all, we focus on multi-antenna codingtechniques, which the difference between traditional Space-Time coding and distributedST coding and two ditributed ST code examples have been introduced. Secondly, wedescribed synchronization problems in cooperative system and a detailed anslysis ofhow the multi-carrier frequency offsets (MCFOs) and multiple timing offsets (MTOs)impact the Alamouti coding performance. Most cooperative communicationsynchronization only consided MCFOs by assume a perfect timing, or assume no CFOsto conside timing synchronization. Therefore, a cooperative system model included bothMCFOs and MTOs have been built in this dissertation. And, a maximum likelihoodestimation method on frequency and timing synchronization with channel estimationwas studied. Then, the Cramer-Rao bound (CRB) for the problem was derived. As thecomputational complexity of joint ML estimation method is very high, the ECMalgorithm and SAGE algorithm were used instead. Simulation results show that theECM and SAGE algorithms can greatly reduce the computational complexity ofestimation in cooperative system.