Design And Impementation Of Uplink Synchronization Of OFDMA System Based On IEEE802.16e

Orthogonal frequency division multiple access (OFDMA) is the IEEE802.16e mainstream technology, which is a muli-user access technology based on OFDM. OFDMA inherits the advantage and disadvantage of OFDM, especially sensitive to synchonization error. The paper studies the uplink technology of synchronization, including the uplink ranging codes, ranging algorithms and frequency offset estimation algorithms.Firstly, some theoretical knowledge is outlined, including the principles of OFDM system, the purpose and the process of the uplink ranging. Based on theoretical derivation, the inflences of all kinds of synchronization errors to the performance of OFDM system are analyzed.Then, the uplink synchronization technology is studied, including three aspects. First, our research work is mainly concerned with ranging codes, including ranging code of PN sequences, an enhanced ranging code of GCL sequences, and a given ranging code based on modified GCL sequences against frequency selective fading with a good performance. Second,the two traditional ranging detection algorithms are researched,which are the time domain detection and the frequency domain detection.A new detection algorithm in frequency domain is presented with superior performance, which overcomes the existing ranging method’s drawbacks namely high complexity, high probability of a false alarm and misdetection.Third,three uplink frequency offset estimation algorithms are derived.And our research work mainly includes two improved algorithms,an improved version of the frequency offset estimation algorithm based on interleaving subcarrier allocation reducing the computational complexity with better performance of frequency offset estimation,a novel estimation algorithm named multi-symbol joint estimation of frequency offset making full use of the correlation between ranging symbols which liminates the affect of data users and residual time offset in frequency domain.Finally, the DSP implementation of uplink ranging process based on PC205 is proposed, including the details of the design process and the processing of each module.