Pedro Coronel

Geographic Routing with Cooperative Relaying and Leapfrogging in Wireless Sensor Networks

A novel geographic routing protocol for multi-hop wireless sensor networks is presented. It exploits the broadcast nature of the wireless channel to enable on-demand cooperative relaying and leapfrogging for circumventing weak radio links. In order to achieve energy efficiency, a metric is introduced for next-hop selection that takes into account information on the residual battery energy, the geographical position of the sensor nodes, and the channel quality of the involved radio links when available. Performance results show that the completely decentralized protocol offers significant benefits by reducing the number of (re)transmissions required to reach the destination. This translates into network-wide energy savings that extend the network lifetime.

Simple ergodic and outage capacity expressions for correlated diversity ricean fading channels

Multiple-antenna systems have been shown to achieve very high spectral efficiencies. In this paper, we derive simple single-integral expressions for the ergodic and outage capacity of a diversity system in correlated Ricean fading channels, where the channel coefficients are assumed to be known to the receiver only. For illustration purpose, we present numerical results showing the effect of channel correlation, Ricean components, angular spread and multipath components in an orthogonal frequency-division multiplexing (OFDM) system

Diversity-multiplexing tradeoff in selective-fading multiple-access MIMO channels

We establish the optimal diversity-multiplexing (DM) tradeoff of coherent selective-fading multiple-access multiple-input multiple-output (MIMO) channels and provide corresponding code design criteria. As a byproduct, on the conceptual level, we find an interesting relation between the DM tradeoff framework and the notion of dominant error event regions which was first introduced in the AWGN case by Gallager, IEEE Trans. IT, 1985. This relation allows to accurately characterize the error mechanisms in MIMO fading multiple-access channels. In particular, we find that, for a given rate tuple, the maximum achievable diversity order is determined by the error event that dominates the total error probability exponentially in SNR. Finally, we show that the distributed space-time code construction proposed recently by Badr and Belfiore, Int. Zurich Seminar on Commun., 2008, satisfies the code design criteria derived in this paper.

An opportunistic energy-efficient medium access scheme for wireless sensor networks

This paper introduces an opportunistic medium-access control (MAC) scheme for controlling the uplink message transfer from sensor nodes to a central controller in wireless sensor networks (WSN). By equipping the controller with multiple antennas to communicate with single-antenna sensors, we propose a scheme that benefits from diversity reception at the controller and leads to a considerable reduction of battery energy consumption in sensor nodes. The performance of the scheme is illustrated using a Rayleigh fading channel model.

Location-Based Cooperative Relaying in Wireless Sensor Networks

In this work, we present a novel routing protocol for energy constrained multi-hop wireless sensor networks. The proposed mechanism exploits the broadcast nature of the wireless channel to enable cooperative relaying in an on-demand manner. It also introduces the concept of leapfrogging that aids in circumventing links with weak channels. Further, in order to achieve energy efficiency, we define a novel metric that takes into account both location as well as channel state information for next-hop selection. The protocol is completely decentralized and preliminary analysis shows that the proposed approach offers significant benefits by reducing the number of (re)transmissions required to reach a destination. This translates into network-wide energy savings that can potentially increase the network lifetime.

Spatial Multiplexing in the Single-Relay MIMO Channel

This work considers the problem of relaying spatially multiplexed signals between a source and a destination using a non-regenerative relay equipped with multiple antennas. In addition to the usual power amplification, the relay is assumed to process the received data vector before forwarding it to the destination. We present two linear filtering techniques that perform this processing in an optimal manner when channel state information (CSI) on the backward and forward channels is available at the relay. Firstly, we derive the relay filter that minimizes the pairwise error probability (PEP) assuming maximum-likelihood (ML) detection at the destination. Secondly, we simultaneously optimize the relay and destination filters in the mean-square error (MSE) sense. The proposed relaying techniques are shown to achieve error performance improvements, especially when the number of antennas at the relay is increased.