Maen M. Artimy

Assignment of dynamic transmission range based on estimation of vehicle density

Vehicular Ad Hoc Networks (VANET) have several characteristics that distinguish them from other ad hoc networks. Among those is the rapid change in topology due to traffic jams, which also disturbs the homogenous distribution of vehicles on the road. For this reason, a dynamic transmission range is more effective in maintaining connectivity while minimizing the adverse effects of a high transmission power.We provide a relationship that allows vehicles to estimate the local density and distinguish between two phases of traffic, free-flow and congested traffic. The density estimate is used to develop an algorithm that sets a vehicle transmission range dynamically according to local traffic conditions.Simulations of various road configurations show that the algorithm is successful in maintaining connectivity in highly dynamic networks.

Local Density Estimation and Dynamic Transmission-Range Assignment in Vehicular Ad Hoc Networks

Vehicular ad hoc networks have several characteristics that distinguish them from other ad hoc networks. Among those is the rapid change in topology due to traffic jams, which also disturbs the homogeneous distribution of vehicles on the road. For this reason, a dynamic transmission range is more effective in maintaining the connectivity while minimizing the adverse effects of a high transmission power. This paper proposes a scheme that allows vehicles to estimate the local density and distinguish between the free-flow and the congested traffic phases. The density estimate is used to develop a dynamic transmission-range-assignment (DTRA) algorithm that sets a vehicle transmission range dynamically according to the local traffic conditions. Simulations of several road configurations validate the quality of the local density estimation and show that the DTRA algorithm is successful in maintaining the connectivity in highly dynamic networks.

Connectivity in inter-vehicle ad hoc networks

A two-stage simulation model is developed to investigate the effects of free flow traffic on connectivity in inter-vehicle ad hoc networks. A traffic microsimulator generates vehicle movement in a multi-lane, unidirectional highway, and a simple network model maintains connectivity graphs between the moving vehicles. The free flow conditions allow vehicles to travel at their maximum velocities, virtually unobstructed by other vehicles because of low vehicle density. We examine some factors that determine the networks ability to maintain an active communication session between a pair of vehicles. Vehicle density, relative velocity, and number of lanes are found to have a key influence on connectivity. The effect of distance, however, depends on the communication range. We also find that the probability distribution of connection lifetime resembles a power law function.

Connectivity with static transmission range in vehicular ad hoc networks

Connectivity in mobile wireless ad-hoc networks is maintained by setting the transmission range so that a node can establish a link to any other node in the network either directly or over multiple hops. Many analytical and experimental studies have focused on determining the minimum transmission range (MTR) that provides connectivity while minimizing transceiver power for various levels of node densities. In this paper, we determine, using simulations, the MTR in vehicular ad hoc networks (VANET) of various road configurations. We show that in 1-lane, 2-lane, and 2-way roads, MTR values confirm the analytical relations developed in the literature for 1-dimensional networks until density increases beyond a critical vehicle density. Moreover, where traffic jams are forming at intersections, MTR values are not affected by the change in vehicle density. Therefore, a large static transmission range must be chosen in order to keep the network connected in all traffic scenarios.

A web-based remote interactive laboratory for Internetworking education

A Web-based remote interactive laboratory (RIL) developed to deliver Internetworking laboratory experience to geographically remote graduate students is presented in this paper. The onsite Internetworking program employs hands-on laboratories in a group setting that correlates with the constructivist and collaborative pedagogical approach. This paper discusses the pedagogical and technical considerations that influence the design and implementation of the remote laboratory environment given the constraints of the special hardware and learning outcomes of the program. For wide-ranging usability, the remote Internetworking (INWK) laboratory uses de facto networking standards and commercial and broad-band Internet connectivity to ensure real-time secure interaction with equipment. A four-tier role architecture consisting of faculty, local facilitators, remote facilitators, and students has been determined appropriate to maintain academic integrity and ensure good quality of interaction with the remote laboratory. A survey employing a five-point scale has been devised to measure the usability of the remote access INWK laboratory.

Automatic detection of acoustic sub-word boundaries for single digit recognition

This paper investigates the use of a spectral variation function to automatically detect acoustic sub-word boundaries in single digits. The developed algorithm generates sub-words for single-digit recognition system using an RBF neural network.

New wavelet packet model for automatic speech recognition system

This paper introduces an automatic speaker-independent speech recognition system. We investigate the performance of the wavelet packet in the analysis of automatically generated subwords of single digits. The modeling of the subwords is accomplished using multienergy levels of a derived mel-like scale. A radial basis function artificial neural network (RBF-ANN) is employed for the recognition task. The proposed model is compared with two systems, one uses manual segmentation, the other segments words based on energy levels extracted from a filter bank. A comparison is made between the performance of systems using two orthogonal wavelets from the Daubechies set and two biorthogonal wavelets.