Showing papers by "Robert M. Edwards published in 2005"

Performance evaluation of routing protocols in vehicular ad-hoc networks

Abstract: This paper presents a reactive location routing algorithm that uses cluster-based flooding for Vehicular Ad-hoc Networks (VANET). We compare both position-based and non-position-based routing strategies in typical urban and motorway traffic scenarios. A microscopic traffic model, developed in OPNET, is used to evaluate the performance of the Location Routing Algorithm with Cluster-Based Flooding (LORA_CBF), Ad-Hoc On-demand Distance Vector (AODV) and Dynamic Source Routing (DSR) in terms of average Route Discovery (RD) time, End-to-End Delay (EED), Routing Load, Routing Overhead, Overhead, and Delivery Ratio.

Applications of a genetic algorithm for identification of maxima in specific absorption rates in the human eye close to perfectly conducting spectacles

Abstract: Relative changes in specific absorption rates owing to perturbing metallic spectacles in proximity to the face are investigated. A representative electrical property biological matter model with twenty five distinct tissue types based on images of an adult male is used with the FDTD method. Both plane wave and dipole source stimuli are investigated and are used to represent a mobile cellular-enabled personal digital assistant held in front of the face. Results show that metallic spectacles may alter significantly specific absorption rate (SAR) level distributions within the head. The frequency range investigated is 1.5-3.0 GHz. Specific attention is given to energy interactions with the eyes. Results are given for several common spectacle frame shapes in addition to whole head energy absorption comparisons. Whole head and single mirrored half head sensitivity data are also presented. A Pareto ranked genetic algorithm (GA) is used to search for the spectacles that cause the highest and lowest SAR in the eye.

On the use of simulation-DFT based analysis for spectral estimation of PPM TH-IR UWB signals

Abstract: Ultra wide band (UWB) radio is thought to be a leading candidate for 4G communication systems and in particular short range low power personal communication systems (PCS). In this paper the periodogram-discrete Fourier transform (DFT) based spectral estimation techniques are reviewed in relation to application to power spectral density (PSD) estimation of pulse position modulated (PPM) time hopping (TH) impulse radio (IR) ultra wideband (UWB) signals. Issues regarding the spectral line power in relation to periodogram-DFT based, nonparametric spectral estimation methods are highlighted.

Spectrum shaping of PPM TH-IR based ultra wideband systems by means of the PPM modulation index and pulse doublets

Abstract: The paper presents the use of the pulse position modulation (PPM) index, /spl beta/, and pulse doublets for spectral line suppression on PPM time hopping impulse radio (TH-IR) ultra wideband (UWB) systems. We define a pulse doublet as a pulse waveform formed by two identical base pulses, with opposite polarity, separated by a fixed time, T/sub D/. It is shown that, by properly choosing the values of /spl beta/ and T/sub D/, a good number of the spectral lines present on the power spectral density (PSD) can be effectively eliminated. In the example presented, the time hopping code is not considered as it also can help to improve the PSD.