Anne-Marie Poussard

A survey of V2V channel modeling for VANET simulations

Most Vehicle to Vehicle (V2V) network protocols are evaluated by simulation. However in most network simulators, the physical layer suffers from a lack of realism. Therefore, realistic V2V channel modeling has become a crucial issue in Intelligent Transportation Systems (ITS) networks. V2V channels are known to exhibit specific features which imply the design of new simulation models. In this survey paper, we first recall the main physical features of such wireless time and frequency dispersive channels. Next, three “simulation-ready” V2V channel models found in the literature are reviewed. Finally, two complete VANET simulation frameworks are presented. They illustrate the importance of a realistic channel and physical layer modeling in vehicular networking.

Improving ZRP performance by taking into account quality of links

MANET are characterized by their limited bandwidth and high packet error rate. In mobility, multi-path and shared bandwidth contexts, routing protocols play a major role. On-demand routing approaches lead to high delay while, in link-state protocols, controls messages broadcasting consumes much bandwidth. Hybrid protocols such as Zone Routing Protocol (ZRP) attempt to exploit the advantages of both approaches. It uses limited scope proactive approach to maintain routes towards a surrounding zone and reactive approach to communicate with farther destinations. For a better exploitation of network capabilities, we propose a Binary Error Rate (BER) based approach of ZRP (BER-ZRP). With BER-ZRP, all phases of link-state recording and routing tables calculation are under Quality of Service control so that better paths in terms of BER are preferred. The overhead induced by route maintenance and route discovery processes is better managed. This approach allows to improve ZRP Packet Delivery Ratio and Normalized Oversize Load.

A new BER-based approach to improve OLSR protocol

This paper presents a method to enhance OLSR quality of service. Our approach heavily relies on the binary error rate metric and allows to rise the packet delivery ratio (PDR). We find that two elements of OLSR must be changed, the MPR selection algorithm and the route computation. We show that our approach provides better PDR than the original OLSR algorithm.

A Semi-Deterministic Channel Model for VANETs Simulations

Todays advanced simulators facilitate thorough studies on Vehicular Ad hoc NETworks (VANETs). However the choice of the physical layer model in such simulators is a crucial issue that impacts the results. A solution to this challenge might be found with a hybrid model. In this paper, we propose a semi-deterministic channel propagation model for VANETs called UM-CRT. It is based on CRT (Communication Ray Tracer) and SCME—UM (Spatial Channel Model Extended—Urban Micro) which are, respectively, a deterministic channel simulator and a statistical channel model. It uses a process which adjusts the statistical model using relevant parameters obtained from the deterministic simulator. To evaluate realistic VANET transmissions, we have integrated our hybrid model in fully compliant 802.11 p and 802.11 n physical layers. This framework is then used with the NS-2 network simulator. Our simulation results show that UM-CRT is adapted for VANETs simulations in urban areas as it gives a good approximation of realistic channel propagation mechanisms while improving significantly simulation time.

AODV enhancements in a realistic VANET context

Ad hoc On demand Distance Vector (AODV) is a commonly used routing protocol for Vehicular Ad hoc NETworks (VANET). This paper presents and analyzes several AODV enhancements propositions dedicated to the VANET context. Communication protocol tuning can yield significant gains in energy efficiency, resource requirement, and overall network performance, all of which is of particular importance in VANETs. Alternatively, multipath routing allows the establishment of multiple paths between a pair of source and destination nodes in mobile ad hoc networks. It has recently received more and more attention and is typically proposed to increase the reliability of data transmission. This paper shows how AODV tuning and multipath routing behave under realistic VANET simulations.

Realistic SISO and MIMO physical layer implemented in two routing protocols for vehicular ad hoc network

In the most of ad hoc network simulators, the physical layer is considered with a simple approach. Moreover, the information routing is realized in order to only minimize the number of hops or the delay. In this paper, the authors propose two contributions: the first one consists in considering a 3D propagation model taking into account the characteristics of the propagation environment for SISO and MIMO physical layers; the second one allows to introduce the BER as a metric of quality of the radio link used in two routing protocols. The impact of these two contributions is evaluated in two environments.

Numerical simulation of LEP Trimpis observed at Poitiers, France, on signals from VLF transmitters

Abstract Transient amplitude and phase perturbations on subionospheric VLF signals, known as the Trimpi effect, are caused by the scattering of VLF radiation from localized ionization enhancements in the nighttime D-region. The patches of ionization are due to precipitation from the radiation belts of keV electrons, that is induced by lightning-generated whistlers.This work is concerned with the numerical simulation of such VLF perturbations, termed LEP (lightning-induced electron precipitation) or classic Trimpis. Two different codes are used to compute the VLF propagation in the Earth-ionosphere waveguide in the presence of a D-region inhomogeneity. The first is based on mode theory, and the second on the FDTD (finite-difference time-domain) method. Both codes are two-dimensional and, therefore, relevant only to LEP events lying on the transmitter-receiver great circle path (TRGCP). A method of simulation is proposed to interpret quantitatively VLF amplitude and phase changes in terms of the approximate location and size of the associated ionospheric perturbation along the TRGCP. The method is applied to LEP Trimpis observed at Poitiers ( L = 2) on signals from the NAA and GQD transmitters. Results are discussed in the light of the information that may be deduced from the high-resolution analysis of VLF temporal signatures. A sequence of simultaneous LEP Trimpis observed at Poitiers on three widely separated transmission paths is studied; two alternative interpretations are proposed.

Impact of Realistic Simulation on the Evaluation of Mobile Ad Hoc Routing Protocols

Todays advanced simulators facilitate thorough studies on vehicular ad hoc networks (VANETs). However, the choice of the physical layer and the mobility models in such simulators is a crucial issue that greatly impacts the results. Realistic simulation of routing protocols in VANETs is still an open question. Indeed, only a few works address routing protocols comparison performed under realistic conditions. This paper compares common reactive, proactive, hybrid, and geographic routing protocols using a simulation platform integrating a realistic physical layer and mobility models. It also presents and analyzes several reactive protocol enhancement propositions dedicated to the VANETs context, such as multipath routing, but also protocols tuning, which allows it to adapt faster. They all have lot of attention and are typically proposed to increase the reliability of data transmission. This paper studies the behavior of each protocol in different situations and analyzed their advantages and drawbacks. Results presented in this paper give an important explanation on the contradictory results found in similar works. Finally, our realistic simulations show that reactive protocols are the best suited for VANETs, and more especially the dynamic Mobile Adhoc NETwork on-demand protocol.

High Frequency MV/LV transformer modelling for Power Line Communication applications

In recent years, design and service evolution in electric distribution networks are mainly guided by the increasing in the customer consumption and the emergence of new sources and loads such as renewable energy, electric and hybrids vehicles. The lack of control over these new constraints in the future may lead to technical and financial problems. Therefore, establishing a supervisory strategy offering a more advanced knowledge of distribution networks is an interesting alternative compared to an expensive strengthening of current networks. Power Line Communication (PLC) technologies present a significant advantage for a supervision application of electric distribution networks. Nevertheless, these networks have not been developed to transmit High Frequency (HF) signals like a PLC. Thus, they induce difficult propagation conditions for PLC. This paper presents an approach to model in HF one element of the distribution network: the MV/LV transformers which established the connection between Medium Voltage (MV) and Low Voltage (LV). The proposed modeling method is based on a black box model whose parameters are obtained from various impedance measurements. It has been applied to four transformers most commonly used by Gérédis, French Distribution System Operator (DSO).

Propagation Models and Physical Layer Quality Criteria Influence on Ad hoc Networks Routing

Modelling of the physical layer is an important factor in ad hoc wireless networks simulation. Thus, the aim of this study is to investigate a realistic physical layer simulator. More precisely, this last one is able to quantify each radio link by various physical layer criteria, thanks to a propagation model, and after compute the optimal route between a source and a destination by using the Dijkstra algorithm.