Outage Capacity of Incremental Relaying at Low Signal-to-Noise Ratios

TL;DR

This paper analyzes the psilon-outage capacity of incremental relaying in low SNR wireless networks, deriving optimal relay placement and comparing it to theoretical bounds, with extensions to multiple relays.

Contribution

It provides a new expression for optimal relay location in low SNR regimes and compares incremental relaying capacity to the cut-set bound, including multiple relay scenarios.

Findings

Optimal relay location depends only on channel conditions, not outage probability or SNR.

The ratio of incremental relaying capacity to the cut-set bound is between 1/2 and 1.

Lower bounds on capacity are derived for networks with multiple relays.

Abstract

We present the \epsilon-outage capacity of incremental relaying at low signal-to-noise ratios (SNR) in a wireless cooperative network with slow Rayleigh fading channels. The relay performs decode-and-forward and repetition coding is employed in the network, which is optimal in the low SNR regime. We derive an expression on the optimal relay location that maximizes the \epsilon-outage capacity. It is shown that this location is independent of the outage probability and SNR but only depends on the channel conditions represented by a path-loss factor. We compare our results to the \epsilon-outage capacity of the cut-set bound and demonstrate that the ratio between the \epsilon-outage capacity of incremental relaying and the cut-set bound lies within 1/\sqrt{2} and 1. Furthermore, we derive lower bounds on the \epsilon-outage capacity for the case of K relays.