In cooperative communications, carrier frequency offsets (CFOs) between pairs of nodes may be different, making CFO 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 an SF-coded cooperative communication system with multiple CFOs, where the SF codes are rotational based and can achieve both full spatial and full multipath diversity orders in a multiantenna system. By exploiting the structure of the SF codes, we propose three signal detection methods to deal with the multiple CFOs problem in the SF-coded orthogonal frequency-division multiplexing (OFDM) system - the minimum mean-squared error (MMSE) filtering method, the two-stage simple frequency-shift Q taps method, and the multiple fast Fourier transform (M-FFT) method - all 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.
['Feng Tian', 'Xiang-Gen Xia', 'P. C. Ching', 'Wing-Kin Ma']
Signal Detection in a Space–Frequency Coded Cooperative Communication System With Multiple Carrier Frequency Offsets by Exploiting Specific Properties of the Code Structure