Systems over Frequency Selective Fading Channels
Feng Aigang,Yin Qinye,Zhao Zheng, Zhang Hong
(School of Electronics and Information Engineering,Xi'an Jiaotong Univercity710049,China)
Abstract:Orthogonal frequency division multiplexing code division multiple access (OFDM-CDMA) scheme can sufficiently utilize the subcarrier diversity and meet the demand of diverse multimedia services;therefore it is broadly considered as an effective approach for future wireless multimedia communications. But it is very sensitive to carrier drifts, while the orthogonal property between the subcarriers is lost with carrier frequency offset. After analyzing the cyclic prefix (CP) based maximum likelihood (ML) joint time-frequency synchronization and the blind carrier drift estimation with virtual subcarrier, a blind adaptive frequency offset estimation algorithm is proposed. It is the fast implementation of the MUSIC-Like estimator with curve fitting to the signal power. With the original value of carrier drift, the testing points are selected to obtain the analytical formation of the curve,and the frequency offset is acquired in closed form. The fast algorithm reduces the computing burden of MUSIC-Like method. The numerical simulations show that the complexity of the proposed algorithm is one eighth less than that of the MUSIC-Like algorithm and has a 25% improvement of spectrum.
Keywords:OFDM;frequency synchronization;freqency selective fading channel