Showing papers by "Geoffrey G. Messier published in 2010"

The Wireless/Power-Line Diversity Channel

Abstract: Wireless devices are often connected to power outlets in residential data and smart-home networks. As a result, physical layer performance can be improved by using the power distribution tree as a diversity channel. This paper proposes a hardware-efficient, low intermediate-frequency (low-IF) transceiver architecture which allows existing wireless protocols to be used over both wireless and power-line communication (PLC) channels. A signal model for this form of hybrid transmission is presented assuming Rayleigh flat-fading and Middleton Class A impulsive noise in the wireless and PLC channels, respectively. Analysis of maximal-ratio combining (MRC) reveals that detector input noise is also Class A-distributed. Expressions for average bit-error rate (BER) of a BPSK subcarrier show that BER is a function of PLC impulsiveness and significant improvement can be achieved with diversity and PLC SNR > 10 dB. In regions of low and high wireless SNR, BER curves are approximately linear with slope of 0 and -1, respectively. The inflection point between these two regions can be used by transceivers to select between PLC-only and hybrid transmission modes.

Wireless network performance for residential demand-side participation

Abstract: In this paper, we investigate the performance of wireless technology for monitoring and controlling the electrical load of a residential neighborhood. An event-based power metering scheme is assumed where transmissions are sent only when a change occurs in household consumption. Analysis of highresolution, empirical data suggests that consumption transitions can be modeled as a Poisson process in the time-domain. A peer-to-peer 802.11 wireless network was simulated to determine latency between houses and a local sub-station. Probability distributions for monitoring and control traffic show that packet latency is exponential distributed and neighborhoods larger than 400 homes may not be able to respond within a fraction of the 60 Hz cycle.

A Gaussian Model for Dead-Reckoning Mobile Sensor Position Error

Abstract: The use of mobile nodes within a wireless sensor network are an asset since they can considerably extend the lifetime of that network. In order for mobile sensor nodes to be effective in most cases, their position must be known. Dead reckoning (DR) is a simple location method that is well suited to complexity constrained sensor nodes. The contribution of this paper is to present a Gaussian model for DR positioning error that is based on measurements collected using a popular robot chassis. The model is verified using Monte Carlo simulations that incorporate the empirical DR error.

Peer-Assisted Caching for Scalable Media Streaming in Wireless Backhaul Networks

Abstract: This paper presents a method for supporting wireless media streaming using a cache that is distributed across the mobile devices in the network. The performance of this scheme is compared to traditional institutional server (IS) caching on a network with a bandwidth constrained wireless backhaul. In addition to traditional caching hit ratio metrics, the paper studies how caching affects the call drop ratio due to limited backhaul bandwidth. These results indicate that the distributed caching method provides better service than IS caching as the number of users is increased. Finally, this paper also presents a scheme for conserving mobile device energy by limiting its participation in the caching scheme. Results show that most of the benefit of the distributed cache can be realized even with relatively few cache assists from each client.

Opportunistic Transmission using Large Scale Channel Effects

Abstract: This paper quantifies the multi-user wireless diversity benefit of basing opportunistic transmission on large scale shadowing. This technique is primarily aimed at wireless sensor nodes. The processing capability of these nodes is limited and transmissions between sensor nodes are very sporadic. It is therefore easier for these devices to track large scale shadowing variations than the small scale shadowing variations normally used for opportunistic transmission. This paper will derive closed form expressions that compare the average SNR improvement provided by opportunistic transmission when based on large scale and small scale channel effects. Closed form bit error rate (BER) expressions will also be used to illustrate that opportunistic transmission based on shadowing can achieve very good performance improvements for modestly sized scheduling groups and realistic indoor shadowing standard deviation values.

A Combined Technical and Economic Comparison of Indoor and Outdoor 4G OFDMA Infrastructure

Abstract: This paper presents a technique for using propagation measurements to perform a site-specific technical and economic comparison of indoor and outdoor orthogonal frequency division multiple access (OFDMA) infrastructure. This work is motivated by the fact that fourth generation (4G) network operators have a choice when provisioning a network to serve indoor users. An operator can choose to retrofit existing outdoor cellular macro-cell base station sites with 4G equipment or to deploy new compact indoor pico-cell base stations. This paper will illustrate how multi-antenna propagation measurements can be collected and used to estimate the throughput of an indoor or outdoor base station. This information will then be incorporated into an economic analysis that determine what sort of network will have the lowest operating and capital costs while still meeting user requirements. This approach is illustrated using a university campus case study.

A 0.13-µm CMOS wireless reflector for phase sweep cooperative diversity

Abstract: A 4-GHz 1.2-V all-analog wireless reflector acting as a cooperative diversity repeater is built in 0.13-µm CMOS technology. Interfaced with a dipole antenna, the circuit achieves 22.3-dB gain for a low power consumption equal to 120 µW. By applying slow phase sweeping at the reflector node, diversity gain is achieved and the coverage area of an indoor wireless network is increased by a factor of 2.5.

Evaluating Wireless Network Effects for SLAM Robot Map Making

Abstract: This work investigates how wireless network performance affects a rescue robot that is running a simultaneous localization and mapping (SLAM) algorithm. The SLAM algorithm is used to generate a map of an unknown disaster site. Odometry and laser range data collected by the robot is transferred via an ad-hoc wireless network to a central access point (AP) that is running the SLAM algorithm. Simulation is used to determine how losses, latency and the use of relays in the network affect the quality and completeness of the SLAM maps. This is illustrated using new metrics for SLAM map quality and completeness that are based on Hausdorff distance.

Implementation of an all-analog active reflector

Abstract: A 3.65-GHz all-analog wireless reflector acting as a cooperative diversity repeater is built in 0.13-μm CMOS technology and its performance is evaluated. Interfaced with a folded dipole antenna, the circuit can achieve a 23.5-dB gain for a very low power consumption equal to 300 μW.