Physical-Layer Network Coding with High-Order Modulations

Abstract

Physical-Layer Network Coding (PNC) can double the throughput of a Two-Way Relay Network (TWRN) by reducing packet exchanging timeslots. In a multi-user wireless communication system, time domain phase shift can inevitably lead to deterioration of PNC performance. In previous studies, there have been many studies result to enhance the performance of some low-order modulation techniques such as BPSK and QPSK, but fewer studies are designed for high-order modulation such as 16-QAM. It is known that high-order modulation is the only way to improve the spectrum utilization rate. This paper uses simulation to explain that the time domain phase shift will greatly affect the performance of 16-QAM PNC, and its’ performance couldn’t be improved even polar code is used. To address this phase penalty problem, we propose a half-symbol asynchronous algorithm to introduce correlations using belief propagation (BP). Simulation results show that the time domain phase shift problem of 16-QAM modulated PNC systems can be solved effectively using our proposed half-symbol asynchronous BP algorithm.

The work of L. Lu was supported by the NSFC under Project 61501390. The work of X. Wang was supported in party by the Science and Technology on Communication Networks Laboratory under Project 614210401050217, and in part by the Special Presidential Foundation of Technology and Engineering Center for Space Utilization of the Chinese Academy of Sciences under Project CSU-ZDBS-201702.