Frequency offset correction for space-time block coded OFDM systems based on maximum likelihood estimation

摘要

This paper discusses the Maximum Likelihood (ML) frequency offset estimation and subsequent correction for a Space-Time Block Coded Orthogonal Frequency Division Multiplexing (STBC-OFDM) system. Carrier frequency offset in OFDM system destroys the orthogonality between subcar-riers resulting in performance deterioration. Also, it considerably reduces the diversity gain for STBC. Accurate frequency offset estimation and subsequent correction will significantly improve the performance of a STBC-OFDM system. This paper proposes an averaging approach for frequency offset estimation. The proposed scheme has been simulated with parameters in conformity with WLAN standards in a Rayleigh fading environment. Simulation results show that after the frequency offset correction, the STBC system may acquire the same level of performance as the system that possesses perfect frequency synchronization.