The Modulation Scheme with Unknown CSI for Analog Network Coding in Multi-Antenna Relay Channel

Abstract Analog network coding (ANC) is a hot topic in recent pioneer researches. Two end-sources can exchange information with the help of a relay by making use of the additive nature of electro-magnetic waves in the wireless two-way relay channel (TWRC). The relay amplify and forward the XORed signal to both of the two sources. In this paper, we assume that each source is equipped with a single antenna and the relay is equipped with multiple antennas. Neither the sources nor the relay can acquire the channel state information (CSI). We propose a novel modulation scheme based on differential modulation. The receivers in TWRC can eliminate the self-interference when their transmitting signals are independent. Then we derive the maximum likelihood (ML) detector for the ANC system with differential modulation signal. We compare the system bit error rate (BER) performance with coherent detection and perfect CSI. Theoretical and simulated results show that even without the aid of CSI, the performance of the proposed system is approximately 1-2 dB away from the optimal coherent detection scheme.