Differential Modulation and Non-Coherent Detection in Wireless Relay Networks

TL;DR

This paper investigates differential modulation and non-coherent detection in cooperative wireless relay networks, analyzing their robustness in mobile environments with time-varying channels and various relay topologies.

Contribution

It develops a time-series model for cascaded channels and evaluates the performance of non-coherent detection in different relay configurations under mobility.

Findings

Non-coherent detection performance varies with channel mobility.

Time-series model accurately characterizes cascaded channel variations.

Relay topology impacts robustness in mobile environments.

Abstract

The technique of cooperative communications is finding its way in the next generations of many wireless communication applications. Due to the distributed nature of cooperative networks, acquiring fading channels information for coherent detection is more challenging than in the traditional point-to-point communications. To bypass the requirement of channel information, differential modulation together with non-coherent detection can be deployed. This thesis is concerned with various issues related to differential modulation and non-coherent detection in cooperative networks. Specifically, the thesis examines the behaviour and robustness of non-coherent detection in mobile environments (i.e., time-varying channels). The amount of channel variation is related to the normalized Doppler shift which is a function of user's mobility. The Doppler shift is used to distinguish between slow time-varying (slow-fading) and rapid time-varying (fast-fading) channels. The performance of several important relay topologies, including single-branch and multi-branch dual-hop relaying with/without a direct link that employ amplify-and-forward relaying and two-symbol non-coherent detection, is analyzed. For this purpose, a time-series model is developed for characterizing the time-varying nature of the cascaded channel encountered in amplify-and-forward relaying.