Performance Analysis of a Multi-Hop Communication System with Decode-and-Forward Relaying

Abstract

This paper analyzes the performance of a multi-hop wireless communication system, consisting of a source node, N intermediate nodes or relays, and a destination node in a Rayleigh fading environment with decode-and-forward relaying at each intermediate node. The data is therefore transmitted from source to destination through N + 1 hops. Two types of modulation, namely, M -ary phase-shift keying (MPSK) and orthogonal M -ary frequency-shift keying (OMFSK), are considered for the transmitted data. In case of MPSK, each relay performs coherent detection, while in case of OMFSK, each relay performs noncoherent detection. Using a difference equation approach, analytical expressions for the end-toend symbol error probability are derived in both cases. We find that (1) although the performance degrades with increasing number of hops for fixed average signal-to-noise ratio per hop, the incremental degradation in performance with the addition of each extra hop decreases, (2) when each node transmits with fixed power, multi-hop transmission offers significant performance improvement over direct transmission. Keywords -Coherent and non-coherent detection, decode-and-forward (DF) relaying, M -ary phase-shift keying (MPSK), multi-hop communication, orthogonal M -ary frequency-shift keying (OMFSK), symbol error probability (SEP). I. IntroductionCooperation when considered in a multi-hop wireless communication scenario offers lower attenuation at distant points, that helps to extend the cell coverage area. It enables users to act as information sources as well as relays, thus increasing data rate [1] and system throughput, and decreasing sensitivity to channel variation [2].Multi-hop systems [3] have raised considerable attention recently as they avoid severe shadowing in long distance communication, or when the transmitted signal energy is relatively low. They also provide broader and cheaper coverage along with large spectral efficiency.Cooperation among users can be established by using the amplify-and-forward (AF) or the decode-and-forward