Alternative Awaiting and Broadcast for Two-Way Relay Fading Channels

TL;DR

This paper introduces new schemes for two-way relay fading channels that significantly improve data exchange rates by approaching theoretical capacity bounds, with practical delay considerations.

Contribution

It proposes two novel awaiting and broadcast schemes that outperform traditional methods and approach the ergodic sum-capacity upper bound at high SNR.

Findings

A new upper bound on ergodic sum-capacity is derived.

Proposed AAB schemes outperform traditional PLNC methods.

CBD with SF-II significantly increases maximum sum-rate with minimal delay.

Abstract

We investigate a two-way relay (TWR) fading channel based on store-and-forward (SF), where two source nodes wish to exchange information with the help of a relay node. A new upper bound on the ergodic sum-capacity for the TWR fading system is derived when delay tends to infinity.We further propose two alternative awaiting and broadcast (AAB) schemes: pure partial decoding (PPD) with SF-I and combinatorial decoding (CBD) with SF-II, which approach the new upper bound at high SNR with unbounded and bounded delay respectively. Numerical results show that the proposed AAB schemes significantly outperform the traditional physical layer network coding (PLNC) methods without delay. Compared to the traditional TWR schemes without delay, the proposed CBD with SF-II method significantly improves the maximum sum-rate with an average delay of only some dozen seconds in the relay buffer.