Signal Detection in a Cooperative Communication System with Multiple CFOs by Exploiting the Properties of Space-Frequency Codes

In cooperative communications, carrier frequency offsets (CFOs) between pairs of nodes may be different, making CFOs compensation difficult if not impossible. These multiple CFOs may drastically degrade the performance of a space-frequency (SF) coded cooperative system. In this paper, we consider the signal detection problem in SF coded cooperative communication systems with multiple CFOs, where the SF codes are rotational based and can achieve both the full cooperative and the full multipath diversities. By exploiting the structure of the SF codes, we propose two signal detection methods to deal with the multiple CFOs problem in the SF coded OFDM systems. They are the minimum mean-squared error filtering (MMSE-F) method, the two-stage simple frequency shift Q taps (FS-Q-T) method, both of which offer different tradeoffs between performance and computational complexity. Simulation results indicate that our proposed detection methods work well as long as the carrier frequency offsets between nodes are not unreasonably large.