Equalization in Space-Frequency Coded Cooperative Communication System with Multiple Frequency Offsets

To combat synchronization errors in cooperative communication, [1] applied the orthogonal frequency division multiplexing (OFDM) technique to achieve the full cooperative diversity and full multipath diversity for asynchronous cooperative communications, in which a kind of high rate space-frequency (SF) code was used at relay nodes. However, as we all know, although OFDM can combat timing errors, it is very sensitive to carrier frequency offset (CFO). For a conventional MIMO-OFDM system, only one CFO exists and its effect can be easily compensated. But for cooperative communication, the CFO between each relay and destination may be different. These multiple CFO make frequency compensation difficult if not impossible. This paper proposes an equalization scheme with its simplified form for SF codes to combat multiple CFO. Simulation results show that the proposed scheme works well with moderate computational complexity when the CFO is not very high.