Optimal Power Allocation Strategies in Full-duplex Relay Networks

TL;DR

This paper develops optimal power allocation strategies for dual-hop relay networks operating in full-duplex or half-duplex modes, considering practical constraints where the source only knows relay power distribution, not instantaneous symbols.

Contribution

It introduces a novel power allocation scheme that adapts to relay mode and power distribution, improving performance over traditional strategies assuming full symbol knowledge.

Findings

Optimal strategies often involve full or partial full-duplex transmission.

Proposed scheme outperforms or matches traditional methods in various scenarios.

Strategy adapts to relay mode and power distribution for enhanced efficiency.

Abstract

In this work, we consider a dual-hop, decode-and-forward network where the relay can operate in full- duplex (FD) or half-duplex (HD) mode. We model the residual self-interference as an additive Gaussian noise with variance proportional to the relay transmit power, and we assume a Gaussian input distribution at the source. Unlike previous work, we assume that the source is only aware of the transmit power distribution adopted by the relay over a given time horizon, but not of the symbols that the relay is currently transmitting. This assumption better reflects the practical situation where the relay node also forwards signaling traffic, or data originated by other sources. Under these conditions, we identify the optimal power allocation strategy at the source and relay, which in some cases coincides with the half duplex transmission mode. In particular, we prove that such strategy implies either FD transmissions over an entire frame, or FD/HD transmissions over a variable fraction of the frame. We determine the optimal transmit power level at the source and relay for each frame, or fraction thereof. We compare the performance of the proposed scheme against reference FD and HD techniques, which assume that the source is aware of the symbols instantaneously transmitted by the relay. Our results highlight that our scheme closely approaches or outperforms such reference strategies.