An Efficient Pilot Scheme in Large-Scale Two-Way Relay Systems

This letter considers an efficient pilot scheme for two-way relay system with massive antennas in the relay base station (BS). For such a system, we prove that user terminals (UTs) in the same communication pair can reuse the pilot sequence without performance loss. Hence, only K pilot symbols are required to support 2K UTs while 2K pilot symbols are needed in conventional cases. We analyze the asymptotic performance when the BS´s antenna number grows infinite. In such a case, the inter-pair interference and noise vanish, and the self-interference determined by the second-order statistics of channel vectors can be feasibly tackled. In this way, the desired signal can be obtained by subtracting the self-interference from the received signal, and the capacity increases with the BS´s antenna number.