Asynchronous Physical-layer Network Coding Scheme for Two-way OFDM Relay

TL;DR

This paper introduces an asynchronous physical-layer network coding scheme for two-way OFDM relays that effectively mitigates CFO-induced interference with reduced computational complexity.

Contribution

A novel two-step asynchronous PLNC scheme employing SAGE algorithm for ICI reconstruction and XOR decoding, improving performance in CFO-affected two-way OFDM relay systems.

Findings

Significantly reduces CFO impact in two-way OFDM relay

Uses SAGE algorithm for efficient ICI parameter estimation

Achieves lower computational complexity compared to traditional methods

Abstract

In two-way OFDM relay, carrier frequency offsets (CFOs) between relay and terminal nodes introduce severe intercarrier interference (ICI) which degrades the performance of traditional physical-layer network coding (PLNC). Moreover, traditional algorithm to compute the posteriori probability in the presence of ICI would incur prohibitive computational complexity at the relay node. In this paper, we proposed a two-step asynchronous PLNC scheme at the relay to mitigate the effect of CFOs. In the first step, we intend to reconstruct the ICI component, in which space-alternating generalized expectationmaximization (SAGE) algorithm is used to jointly estimate the needed parameters. In the second step, a channel-decoding and network-coding scheme is proposed to transform the received signal into the XOR of two terminals' transmitted information using the reconstructed ICI. It is shown that the proposed scheme greatly mitigates the impact of CFOs with a relatively lower computational complexity in two-way OFDM relay.