Design and implementation of physical-layer network-coding protocols

Recently, there has been a growing interest in physical-layer network-coding techniques that facilitate information transfer in wireless relay networks. Physical-layer network-coding techniques take advantage of the additive nature of wireless signals by allowing two terminals to transmit simultaneously to the relay node. This technique has several performance benefits, such as improving utilization and throughput of wireless channels and reducing delay. In this paper, we present an algorithm for joint decoding of two unsynchronized transmitters to the modulo-2 sum of their transmitted messages. We address the problems that arise when the boundaries of the signals do not align with each other and when their phases are not identical. Our approach uses a state-based Viterbi decoding scheme that takes into account the timing offsets between the interfering signals. Our simulation studies show that this decoder outperforms previous approaches in the presence of noise and timing offset.