A New Scaling Law on Throughput and Delay Performance of Wireless Mobile Relay Networks over Parallel Fading Channels

TL;DR

This paper introduces a novel relay scheme that leverages relay buffers and mobility to optimize throughput and delay in wireless relay networks over fading channels, outperforming existing methods especially with mobile relays.

Contribution

It proposes an opportunistic decode-wait-and-forward relay scheme that exploits relay buffers and mobility to improve throughput-delay tradeoffs in dense relay networks.

Findings

Achieves asymptotic throughput of (\, ext{log}\, K) with (\,K/q) delay for mobile relays.

Matches optimal throughput with fewer relays in fixed relay scenarios.

Effectively exploits relay mobility to enhance network performance.

Abstract

In this paper, utilizing the relay buffers, we propose an opportunistic decode-wait-and-forward relay scheme for a point-to-point communication system with a half-duplexing relay network to better exploit the time diversity and relay mobility. For instance, we analyze the asymptotic throughput-delay tradeoffs in a dense relay network for two scenarios: (1) fixed relays with \textit{microscopic fading} channels (multipath channels), and (2) mobile relays with \textit{macroscopic fading} channels (path loss). In the first scenario, the proposed scheme can better exploit the \textit{multi-relay diversity} in the sense that with $K$ fixed relays and a cost of $\mathcal{O}(K)$ average end-to-end packet delay, it could achieve the same optimal asymptotic average throughput as the existing designs (such as regular decode-and-forward relay schemes) with $K^2$ fixed relays. In the second scenario, the proposed scheme achieves the maximum throughput of $\Theta(\log K)$ at a cost of $\mathcal{O}(K/q)$ average end-to-end packet delay, where $0<q\leq {1/2}$ measures the speed of relays' mobility. This system throughput is unattainable for the existing designs with low relay mobility, the proposed relay scheme can exploit the relays' mobility more efficiently.