Realistic transmitter vs receiver cooperation in wireless sensor networks with non ideal carrier synchronization

This paper addresses a mathematical formulation and performance evaluation of a wireless sensor network allowed to cooperate at the transmitter, receiver or both sides. The main point is that we consider imperfect carrier synchronization and evaluate how this realistic assumption degrades the performance of also realistic cooperative strategies: we have selected V-BLAST as a representative receiver cooperation strategy, Tomlinson-Harashima for the transmitter cooperation and the SVD decomposition (with optimum power allocation among the modes) for the full cooperative case. If theoretical analysis provided by other papers recommend the use of just transmitter cooperation because receiver and full cooperation do not provide significant gain, on our hand we will show that receiver cooperation is more robust and closes the optimum performance under non ideal conditions.

1. INTRODUCTION

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This work has been partly supported by National Spanish Projects PCT- 350100-2004-1, TEC2004-06915-C03-02/TCM TIC2003-09061-C03-01 and European IST-2002 507039

Sensor networks and ad-hoc networks are receiving more and more attention from the research community. There are several challenges from many points of view coming up from Information Theory limits, device efficiency (power saving) and network issues (routing). In particular, cooperative diversity is a novel technique where several nodes work together to form a virtual antenna array [1], [2]. This point is quite important because connects more mature experience in MIMO communications in the real antenna array with this field. Vector Gaussian, Broadcast, Multiple Access and Interference Channels (GC, BC, MAC, IC) are the standard models assumed for different degrees of cooperation in real MIMO links [3] that can provide asymptotic performances in Wireless Sensor Networks (WSN) if cooperation is not penalized. However, although these results are very valuable it is also important to review critically these conclusions considering more realistic models.