A simple distributed differential transmit beamforming technique for two-way wireless relay networks

Various differential distributed space-time coding techniques for cooperative relay networks have recently been proposed which do not require channel state information (CSI) neither at the relays nor at the terminals. Differential encoding schemes are generally associated with a low bit error rate (BER) performance and a comparably high latency and decoding complexity. Another popular approach used in relay networks are distributed beamforming techniques which enjoy a high BER performance, low decoding complexity and optimal decoding delay. However, their common requirement is perfect CSI available at all nodes. In this paper, we combine the differential diversity and the distributed beamforming technique while retaining the benefits of both approaches. The proposed technique enjoys high BER performance, optimal delay, and low decoding complexity without requiring CSI at any node.