Marwane Ayaida

Joint routing and location-based service in VANETs

Geographic routing protocols use location information when they need to route packets. In the meantime, location information are maintained by location-based services provided by network nodes in a distributed manner. Routing and location services are very related but are used separately. Therefore, the overhead of the location-based service is not considered when we evaluate the geographic routing overhead. Our aim is to combine routing protocols with location-based services in order to reduce communication establishment latency and routing overhead. Our main contribution is to reduce the location overhead. Thus, we propose two combinations: (1) a geographic routing protocol with GLS called Hybrid Routing and Grid Location Service (HRGLS) and (2) a geographic routing protocol with HLS denoted Hybrid Routing and Hierarchical Location Service (HRHLS), where instead of launching an exact position request, we send the packet to the old destination position and when the packet is approaching the former position, we request the exact one. The complexity of the location query cost in both proposed schemes is O(logN), while it is O(N) in the case of HLS and GLS. Simulation results also confirm the complexity analysis and show promising results in terms of latency, packet delivery ratio and control message overhead.

A Comparison of Reactive, Grid and Hierarchical Location-Based Services for VANETs

VANETs (Vehicular Ad-hoc NETworks) are a special case of MANETs (Mobile Ad-hoc NETworks). Their main feature is the high mobility range of nodes, which causes topology changes and frequent disconnections. Topology-based routing protocols have weak performances in such networks. This is why a new set of routing protocols, designated as geographic routing protocols, were designed to enhance performances and ensure a better scalability. These geographic protocols assume on one hand that all nodes must be aware about their position (by using a positioning system like GPS). On the other hand they also assume a certain knowledge about the position of the destination node and the position of their neighbors thanks to Location-based Services. In this paper, we compare three location-based services: Reactive Location Service (RLS), Grid Location Service (GLS) and Hierarchical Location Service (HLS) while coupled to the well known geographic routing protocol Greedy Perimeter Stateless Routing (GPSR). As far as we know, our work is the first that targets the performance evaluation of location-based services while coupled with a routing protocol. The simulations were performed using the NS-2 simulator on a realistic map about the city of Reims (France). Besides, a scalability study of GLS and HLS is presented. This study is based on three qualitative metrics (the location maintenance cost, the location query cost and the storage cost).

HHLS: A hybrid routing technique for VANETs

In this paper, we propose a combination between a routing protocol Greedy Perimeter Stateless Routing (GPSR) and Hierarchical Location Service (HLS) that we denote Hybrid Hierarchical Location Service (HHLS). HLS and GPSR used to be combined in the original work with a direct method, i.e. GPRS takes care of routing packets and HLS is called to get the destination position when the target node position is not known or is not fresh enough. When a destination is quite far away from the sender, the exact position of the target is calculated, and an extra overhead is generated from sender to receiver. Our main purpose is to reduce this overhead in HHLS. We suggest to proceed as follows: when a packet has to be sent to the destination, it will be sent directly to the former position of the target instead of requesting for the exact position. When the packet is approaching the former position, the exact position request is then sent. We have proposed a patch over the NS-2 simulator for HHLS according to our proposal. We have conducted experimentations which show promising results in terms of latency, packet delivery rate and overhead.

PHRHLS: A movement-prediction-based joint routing and Hierarchical Location Service for VANETs

Location-based services provide (and maintain) location information used by geographic routing protocols. Routing and location service are widely related, but handled separately in usual studies about Vehicular Ad hoc Network (VANET). In this paper, we propose a hybrid approach, denoted mobility-Prediction-based Hybrid Routing and Hierarchical Location Service (PHRHLS), coupling a VANET routing protocol, the Greedy Perimeter Stateless Routing (GPSR), and the Hierarchical Location Service (HLS) extended with a mobility prediction algorithm. We show that our approach, PHRHLS, reduces the localization overhead and enhances the routing performances. Indeed, our extensive simulations show promising results in terms of end-to-end latency, packet delivery ratio and control message overhead.

A testing framework for Intelligent Transport Systems

Experimental deployment of Cooperative Intelligent Transportation Systems have been undertaken these last years. But a real deployment is lower than expected. One reason is the lack of complete validation techniques which handle the whole system. The aim of this paper is to present a complete framework able to test each component involved in a C-ITS and which is able to check the interoperability of all components. This framework ensures the conformance testing of all the C-ITS components regarding their specifications (mainly the communication protocols which ensure the interoperability over various layers) as well as the interoperability testing of these components in order to guarantee their correct functioning where they perform together. This framework has been used with mobile ITS stations and fixed ITS stations provided by different vendors. Many test series have been undertaken. C-ITS development is not quite mature, then many bugs have been detected thanks to the execution of test cases. The design of this framework and its use have shown that a deployment of an actual C-ITS is still a difficult task. The use of our framework has underlined that some standard specifications (either protocols or test case specifications) need to be improved.

A slot assignment for Wireless Body Area Networks

This study presents a dynamic slot assignment for tasks executed over Wireless Body Area Networks. We consider tasks which have timing constraints for their execution. and different priorities. They are usually repeated periodically. In this study we propose an algorithm which is able to provide a dynamic scheduling procedure for all tasks. In the actual version, the scheduling algorithm is executed over the network coordinator. This algorithm is implemented over TelosB nodes composing a Wireless Body Area Network.

A dynamic slot scheduling for wireless sensors networks

This paper proposes a dynamic slot scheduling for tasks having different time constraints executed over wireless sensor networks (WSN). These tasks may have different priorities. They are usually repeated periodically. We present an algorithm which is able to provide a dynamic scheduling procedure for all tasks. In the actual version, the scheduling algorithm is executed on the network coordinator which monitor the slot distribution for all nodes. This algorithm is implemented over TelosB nodes.

A validation tool for cooperative intelligent transport systems

Abstract This paper aims to present a set of tools that could be used in order to check the conformance of an Cooperative-Intelligent Transport System (C-ITS). These tools will consider each C-ITS component, i.e. C-ITS-R Road Side Units (RSU), C-ITS-V On-Board Unit (OBU), C-ITS-C (Central Server) with their specific features as location precision for an OBU and adequate forwarding of security events for an RSU. We first tackle in this study the conformance testing aspect for each component (in fact a C-ITS component has to respect all the basic specifications) before checking the interoperability of all components (in order to ensure a correct functioning when they work together). Basic specifications have been mainly described by standardisation institutes as ETSI or IEEE. But some additional specifications could be considered for particular purposes (for example, car manufacturers do not all agree on the pertinent moment to inform drivers on next hazardous events). This framework has been experimented with various RSUs and OBUs from different providers and many troubles have been detected. Most of the bugs are due to a wrong interpretation of specifications. But, in some other cases, troubles reveal that specifications have been proposed with incorrect behaviours. The main conclusion is that such frameworks have to be improved and deployed widely in order to facilitate the deployment of large scale Intelligent Transport Systems.

Scheduling approaches in beacon-enabled mode for wireless sensor networks

Efficient energy consumption is the most important challenge in wireless sensors networks. Many solutions have been proposed since many years as efficient medium access control protocols, smart sensing applications, appropriate task scheduling, and so on. Task scheduling allows could participate to optimise energy consumption, it aims to propose planning over repetitive time periods where sensors need to sleep, to collect data and to communicate. In this paper, we propose two scheduling procedures (semi‐dynamic and dynamic) which are executed over the ZigBee network in beacon‐enabled mode. Each of these algorithms has its own features and advantages. The Zigbee super‐frame is used as a means to inform each node on its duties (when to sleep or when to communicate). In order to evaluate our proposals, we have implemented them over TelosB motes running on operating system TinyOS. These algorithms have been implemented on the Z‐Monitor tool . We have compared our scheduling approaches to the usual static scheduling method provided by Zigbee. These evaluations show that our proposals enhance network lifetime and ensure better packet data rate and lower latency. Copyright

A Framework for Validation of Cooperative Intelligent Transport Systems

This paper aims to present a methodology and a set of tools that could be used in order to check the validity of an Intelligent Transport System. These tools will consider each ITS component, i.e. C-ITS- R (Road Side Units) RSU, C-ITS-V (On-Board Unit) OBUU, C-ITS-C (Central Server) with its specific fea- tures as location precision for an OBU and adequate forwarding of dangerous events for an RSU. The aim of this paper is to tackle first con- formance testing for each component (in fact the component have to respect all basic specifications) before check the interoperability of all components (in order to ensure a correct functioning of the when they work together). Basic specifications have been mainly described by standardization institutes as ETSI or IEEE. But some additional specifications could be considered for particular aims (for example, car manufacturers do all agree on the distance to inform drivers on next dangerous events). This framework has been experimented with var- ious RSUs and OBUs from different providers. We have experimented the framework with all of them and many troubles have been detected. Most of the bugs are due to a wrong interpretation of specifica- tions. Sometimes, troubles reveal that specifications have been proposed with incorrect behaviors. The main conclusion is that such frameworks have to be improved and deployed widely in order to allow the deployment of large scale Intelligent Transport Systems.