A Low-Complexity Receiver for Cooperative Simultaneous Relaying

We consider the impact of carrier frequency offsets arising naturally when multiple relay terminals transmit simultaneously using a space-time code in a cooperative relaying scenario. In such a scenario, we design an adaptive, low-complexity receiver that attempts to eliminate the effect of frequency offsets. The adaptive receiver allows for decoupling of the decisionmaking of transmitted symbols utilizing the orthogonality of the underlying space-time code. In a quasi-static Rayleigh fading channel, we demonstrate the performance of the adaptive receiver over a range of frequency offsets by considering two transmitting relays. We prove that the adaptive receiver achieves full diversity, and using simulation results for two relays we show that the performance greatly improves over a conventional differential receiver that ignores the presence of frequency offsets.