Algorithm Research On Synchronization For The Multi-User OFDMA System

Compared to the traditional OFDM system, the synchronization of OFDMA system has the new difficulty. First of all, the received signal is the superposition of multi-user's, and their carrier frequency are different with each other, so the synchronization has became a multi-parameter estimation problem. Secondly, the Carrier Frequency Offset(CFO) become more complex, because the offset for one user may have the influence to others.In this thesis, at first I introduce the principle of OFDM technology and OFDM system. Then in the third chapter general OFDMA system model is established, and then do the research on the CFO estimation algorithm based on the block subcarrier-assignment scheme, do the analysis about the effect of the carrier-frequency offset estimation of OFDMA system by different distribution of preamble. Also do the analysis on the CFO estimation algorithm based on the interleaved subcarrier-assignment scheme.With the estimation results, we must do the compensation for the data received. Since the received signal is the superposition of multi-user's, it makes much difficult of CFO for the OFDMA system. In fourth chapter, we put great emphasis on the CFO algorithm based on the block subcarrier-assignment scheme, we can use circulation convolution, iterative algorithm for the CFO. The performance of the algorithm have the great relation with the time you used for iteration and the user number in the system, then we have the improved algorithm for the totally CFO: both integer and fraction. At last we research on the user separation algorithm for the OFDMA system based on the interleaved subcarrier-assignment scheme and use the simulation to demonstrate that it is useful for the multi-path channel.