A Novel Timing Estimation Method Using Subblock Correlation for OFDM Systems

• Main Authors: Jin-Tong Chang, 張晉通
• Other Authors: Jyh-Horng Wen
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/91279801569721050264

碩士 === 國立中正大學 === 通訊工程研究所 === 91 === Recently, interest has focused on modulation techniques which can provide broadband transmission over wireless channels for applications including wireless multimedia, wireless internet access, and future-generation mobile communication system. One of the main requirements on the modulation technique is the ability to combat inter symbol interference (ISI) that is a major problem in wideband transmission over multipath fading channel. Orthogonal Frequency Division Multiplex (OFDM) technique is a good method proposed to combat the ISI nowadays. In this thesis, the basic principles of OFDM system are investigated in advance. We discuss the maximum likelihood timing estimate method and its performance in AWGN and multipath channels. Then, a novel timing estimation for OFDM system by subblock correlation is proposed. We use the subblock correlation between cyclic prefix and copied data to estimate symbol timing. The efficiency of this technique will be demonstrated by simulation results. It can be observed that the proposed method has better MSE performance than ML method in timing estimation, and the delay spread can also be estimated via ensemble average of the subblock correlation over several OFDM symbols. Since the subblock correlation technique can give the information of the delay spread, when the channel variation is slow, an adaptive cyclic prefix concept may be used to effectively reduce the system overhead caused by the cyclic prefix.