Frame-asynchronous physical-layer network coding using cyclic codes

Physical-layer network coding (PNC) is an innovative technique for improving the efficiency of wireless communication systems. In theory, due to the utilisation of superimposed signals at a wireless relay, PNC can double the system throughput when compared to traditional point-to-point systems. However, achieving perfect synchronisation between transmitted signals at the relay is challenging. The use of cyclic low-density parity-check (LDPC) codes and cyclic redundancy check (CRC) to combat frame asynchrony in PNC has recently been proposed. In this paper, we propose a novel approach to cope with frame misalignment in PNC using cyclic codes with a cyclic prefix. We also introduce a new frame structure for PNC systems, which adopts Gold sequences as its pilot sequences. Due to particular properties of the Gold sequences, arrival delay between two signals overlapped at the relay can be estimated effectively. Simulation results show that cyclic prefix usage can significantly compensate for frame misalignment.