Timing And Frequency Synchronization Algorithms And Strategies For Uplink/downlink Of OFDMA System

The"Timing and Frequency Synchronization Algorithms and Strategies for uplink/downlink of OFDMA system"is discussed in the thesis, which is a subproject of the research of the broadband wireless access.Firstly, the basic principle of OFDM and OFDMA is briefly introduced and the advantages and disadvantages of them are investigated. And the impact of uncompensated timing and frequency errors on the performance of OFDMA system is analysised later.Then some common methods to achieve timing and frequency alignment in downlink and uplink are reviewed. In OFDMA downlink, each user's frequency and timing estimation are similar to the synchronized estimation of each single user in OFDM broadcast channel. Based on different training sequences, three synchronized estimation algorithms are mainly studied. In OFDMA uplink, synchronization is difficult for the base station has to estimate on several parameters. A MUSIC algorithms based on interleaved carrier allocation schemes is studied, which can estimate the frequency offset.Timing and frequency correction is another challenge. In the thesis, the synchronization policy is feeding back the estimation results to the transmitter through downlink channel. Each user exploits to properly adjust its transmitted signal.Finally, an algorithm based on Chu sequence can be applied in the project studied, followed by the computer simulation and the performance analysis.