On the Equal-Rate Capacity of the AWGN Multiway Relay Channel

TL;DR

This paper analyzes the capacity of the L-user AWGN multiway relay channel, deriving new achievable rate regions and exact capacity results for certain cases, and comparing different relaying strategies across SNR levels.

Contribution

It introduces a new achievable rate region based on functional-decode-forward and derives the exact capacity for specific scenarios with multiple users.

Findings

Capacity is achieved for three or more users with equal power.

Functional-decode-forward outperforms other strategies at high SNR.

Both compress-forward and functional-decode-forward are within a constant gap of capacity.

Abstract

The L-user additive white Gaussian noise multiway relay channel is investigated, where L users exchange information at the same rate through a single relay. A new achievable rate region, based on the functional-decode-forward coding strategy, is derived. For the case where there are three or more users, and all nodes transmit at the same power, the capacity is obtained. For the case where the relay power scales with the number of users, it is shown that both compress-forward and functional-decode-forward achieve rates within a constant number of bits of the capacity at all SNR levels; in addition, functional-decode-forward outperforms compress-forward and complete-decode-forward at high SNR levels.