Distributed Consensus over Wireless Sensor Networks Affected by Multipath Fading

The design of sensor networks capable of reaching a consensus on a globally optimal decision test, without the need for a fusion center, is a problem that has received considerable attention in the last years. Many consensus algorithms have been proposed, with convergence conditions depending on the graph describing the interaction among the nodes. In most works, the graph is undirected and there are no propagation delays. Only recently, the analysis has been extended to consensus algorithms incorporating propagation delays. In this work, we propose a consensus algorithm able to converge to a globally optimal decision statistic, using a wideband wireless network, governed by a fairly simple MAC mechanism, where each link is a multipath, frequency-selective, channel. The main contribution of the paper is to derive necessary and sufficient conditions on the network topology and sufficient conditions on the channel transfer functions guaranteeing the exponential convergence of the consensus algorithm to a globally optimal decision value, for any bounded delay condition.Comment: Paper submitted to IEEE Transactions on Signal Processing, August 2007. Revised November 30, 2007. Accepted January 14, 200

Distributed decision in sensor networks based on local coupling through Pulse Position Modulated signals

In this work we propose a physical layer design, based on Pulse Position Modulated (PPM) signals, for a decentralized wireless sensor network implementing an iterative consensus algorithm. The proposed scheme does not require any MAC protocol to avoid or resolve collisions, and is also suitable for a half-duplex implementation. The considered network model assumes only local coupling among the nodes, thus allowing for low transmit power even in large scale networks. Furthermore, we show how to remove the effect of propagation delays, multipath, and non perfect synchronization among the nodes, without requiring any channel parameter estimate. As an example of application, we consider a simple parameter estimation problem, which is instrumental to discuss the fundamental trade-offs arising in the system parameters settings, when both observation noise and coupling noise are considered in the performance analysis. ©2008 IEEE