Performance Analysis over Slow Fading Channels of a Half-Duplex Single-Relay Protocol: Decode or Quantize and Forward

TL;DR

This paper introduces a new Decode or Quantize and Forward (DoQF) protocol for half-duplex single-relay wireless channels, analyzing its outage performance and diversity-multiplexing tradeoff, showing it outperforms existing protocols in slow fading scenarios.

Contribution

The paper proposes a novel static relaying protocol, derives its outage gain and DMT, and demonstrates its optimality among half-duplex protocols in slow fading channels.

Findings

Outage gain converges to a constant as SNR increases.

DoQF achieves the 2x1 MISO upper bound for multiplexing gains below 0.25.

The protocol outperforms existing half-duplex relaying schemes.

Abstract

In this work, a new static relaying protocol is introduced for half duplex single-relay networks, and its performance is studied in the context of communications over slow fading wireless channels. The proposed protocol is based on a Decode or Quantize and Forward (DoQF) approach. In slow fading scenarios, two performance metrics are relevant and complementary, namely the outage probability gain and the Diversity-Multiplexing Tradeoff (DMT). First, we analyze the behavior of the outage probability P_o associated with the proposed protocol as the SNR tends to infinity. In this case, we prove that SNR^2 P_o converges to a constant. We refer to this constant as the outage gain and we derive its closed-form expression for a general class of wireless channels that includes the Rayleigh and the Rice channels as particular cases. We furthermore prove that the DoQF protocol has the best achievable outage gain in the wide class of half-duplex static relaying protocols. A method for minimizing the outage gain with respect to the power distribution between the source and the relay, and with respect to the durations of the slots is also provided. Next, we focus on Rayleigh distributed fading channels to derive the DMT associated with the proposed DoQF protocol. Our results show that the DMT of DoQF achieves the 2 by 1 MISO upper-bound for multiplexing gains r < 0.25.