On the Impact of Relay-side Channel State Information on Opportunistic Relaying

TL;DR

This paper analyzes how different levels of channel state information at relays affect the outage performance of distributed opportunistic relay selection, highlighting the trade-offs between CSI accuracy and power efficiency.

Contribution

It provides an analytical comparison of relay selection performance with exact versus statistical CSI, revealing the impact on power requirements and diversity at various SNR levels.

Findings

Similar diversity order with both CSI types

Increased power needed with less precise CSI

Performance degradation at low SNR with statistical CSI

Abstract

In this paper, outage performance of network topology-aware distributed opportunistic relay selection strategies is studied with focus on the impact of different levels of channel state information (CSI) available at relays. Specifically, two scenarios with (a) exact instantaneous and (b) only statistical CSI are compared with explicit account for both small-scale Rayleigh fading and path loss due to random inter-node distances. Analytical results, matching closely to simulations, suggest that although similar diversity order can be achieved in both cases, the lack of precise CSI to support relay selection translates into significant increase in the power required to achieve the same level of QoS. In addition, when only statistical CSI is available, achieving the same diversity order is associated with a clear performance degradation at low SNR due to splitting of system resources between multiple relays.