Abstract:

In cooperative communication systems based on space-time block coded orthogonal frequency division
multiplexing (STBC-OFDM), inter-channel interference (ICI) and co-channel interference (CCI) arise from multiple
carrier frequency offsets (CFO) among different user nodes. Practical equalization methods are studied to combat these two interferences. When difference of normalized CFOs (DCFOs) is small, a low-complexity iterative approach named IAZF is proposed, which achieves zero forcing (ZF) equalization. In case of large DCFOs, a joint equalization algorithm (JEA) is given, which combines successive minimum mean square error (MMSE) inter-block interference cancellation with parallel interference cancellation. Furthermore, by exploiting the approximate banded structure of channel matrix, we implement recursive calculation of matrix inversion of JEA to reduce the computation burden. Simulation results show that, in a quite large range of DCFOs, JEA is robust with significant improvement over the existing methods, especially when DCFOs is larger than 0.25. The performance of IAZF approaches those of other methods when DCFOs is less than 0.15, and requires low computation load.

Key words: communication, equalization, carrier frequency offset, space-time block coding, OFDM, cooperative communication