Practical relay networks: a generalization of hybrid-ARQ

TLDR

Wireless networks exploit inherent spatial diversity via relaying, leveraging broadcast-oriented radio and node-based protocols, yet prior studies have relied on unrealistic assumptions, complex protocols, or single-relay setups. The paper proposes a practical multi-relay network scheme using a generalized hybrid-ARQ over orthogonal time slots. The scheme allows relays to retransmit packets instead of the source and employs an information-theoretic framework to characterize performance limits in block fading, with numerical results for representative topologies. The results show a significant improvement in the energy‑latency tradeoff versus conventional multihop cascades.

Abstract

Wireless networks contain an inherent distributed spatial diversity that can be exploited by the use of relaying. Relay networks take advantage of the broadcast-oriented nature of radio and require node-based, rather than link-based protocols. Prior work on relay networks has studied performance limits either with unrealistic assumptions, complicated protocols, or only a single relay. In this paper, a practical approach to networks comprising multiple relays operating over orthogonal time slots is proposed based on a generalization of hybrid-automatic repeat request (ARQ). In contrast with conventional hybrid-ARQ, retransmitted packets do not need to come from the original source radio but could instead be sent by relays that overhear the transmission. An information theoretic framework is exposed that establishes the performance limits of such systems in a block fading environment, and numerical results are presented for some representative topologies and protocols. The results indicate a significant improvement in the energy-latency tradeoff when compared with conventional multihop protocols implemented as a cascade of point-to-point links.