Tarek Bejaoui

Handover and class-based Call Admission Control policy for 4G-heterogeneous mobile networks

In this paper we propose a handover and class-based Call Admission Control algorithm for UMTS/WLAN heterogeneous networks. Its main objective is to limit the occurrence of hard WLAN-UMTS handovers to mobile nodes moving across cells and using real time applications. Our mechanism is based on the service class differentiation, the call origination point, and a vertical handoff decision function as well. It aims at maximizing the utilization of the resources available at the WLAN cells, and meeting the QoS requirement of higher priority users as much as possible while maintaining the minimum requirements of lower priority users, especially when the UMTS and the WLAN networks suffer from congestion. The new CAC policy achieves a good performance and capacity gain.

SEAD: A simple and efficient adaptive data dissemination protocol in vehicular ad-hoc networks

Abstract Vehicular ad-hoc network (VANET) is becoming a promising technology for improving the efficiency and the safety of intelligent transportation systems by deploying a wide variety of applications. Smart vehicles are expected to continuously exchange a huge amount of data either through safety or non-safety messages dedicated for road safety or infotainment and passenger comfort applications, respectively. One of the main challenges posed by the study of VANET is the data dissemination design by which messages have to be efficiently disseminated in a high vehicular speed, intermittent connectivity, and highly dynamic topology. In particular, broadcast mechanism should guarantee fast and reliable data delivery within a limited wireless bandwidth in order to fit the real time applications’ requirements. In this work, we propose a simple and efficient adaptive data dissemination protocol called “SEAD”. On the one hand, the originality of this work lies in its simplicity and efficiency regardless the application’s type. Simplicity is achieved through a beaconless strategy adopted to take into account the surrounding vehicles’ density. Thanks to a metric locally measured, each vehicle is able to dynamically define an appropriate probability of rebroadcast to mitigate the broadcast storm problem. Efficiency is manifested by reducing excessive retransmitted messages and hence promoting the network capacity and the transmission delay. The simulation results show that the proposed protocol offers very low packet drop ratio and network load while still maintaining a low end-to-end delay and a high packet delivery. On the other hand, SEAD protocol presents a robust data dissemination mechanism which is suitable either for safety applications or for other kinds of application. This mechanism is able to adapt the protocol performance in terms of packet delivery ratio to the application’s requirements.

Network coding approach for vehicle-to-vehicle communication: Principles, protocols and benefits

Information dissemination in vehicular networks is becoming a hot topic of research in the field of Vehicle-to-Vehicle (V2V) communications, since efficient data exchange is needed for most crucial applications (road accident warning, traffic congestion warning ...). Many protocols have been then proposed for the sake of disseminating information with high reachability and low end-to-end delay in limited bandwidth. In this work, we propose to review the design of some of dissemination protocols based on the network coding technique. Newly adopted in wireless ad hoc networks, network coding paradigm seems to be a promising solution for data dissemination in vehicular environment. The goal of this work is then to classify the different network coding based protocols appeared in the literature and reveal the gain achieved once this technique is applied. To this end, a summary table for a comparative study of the numerous retained protocols is presented.

An enhanced chord-based P2P lookup protocol for mobile Ad hoc networks

Nowadays, a new paradigm is emerging: the challenging integration of Peer-to-Peer into mobile Ad hoc networks (MANETs). In this context, this paper proposes a new distributed lookup protocol for mobile P2P networks. Its main objective is to reduce the overhead traffic and the lookup delay. Simulation results indicate that the proposed scheme has an improved performance in comparison with the popularly used Chord protocol and its extension, the Backtracking Chord protocol.

A Cross Layer Balanced Routing Protocol for Differentiated Traffics over Mobile Ad Hoc Networks

We propose a cross layer approach to achieve greater routing performance for applications with real time constraints in Mobile Ad Hoc Networks. Interactions between MAC, Network and Application layers are fully exploited to get accurate information about the end-to-end path quality, and the applications’ characteristics. The improvements provided by our scheme come from considering a service class differentiation, a balanced routing protocol and a path quality cost function as well. It aims to enhance the routing performance for real time applications to meet the QoS requirements defined by the ITU-G1010 recommendation. The simulation results and analysis show that our contribution achieves a good performance and capacity gain.

Vehicle density-based resource allocation policy for QoS provisioning in vehicular communication networks

In this paper, we propose a combined fair packet scheduling and vehicle density-based call admission control policy that provides throughput guarantee, for vehicular ad hoc networks (VANETs). It takes into account a realistic behaviour of traffic while considering the spatial variation of the system characterizing both the vehicle mobility and the signal propagation impairments due to the surrounding effects. The new adaptive QoS oriented CAC scheme decides whether the connection request is to be admitted into the system, on the basis of the density of vehicles and the guarantee of the desired throughput. It aims then at maximizing the use of available resources and meeting the QoS requirement of users of constraining services. As for the proposed scheduling policy, a priority level computing function is presented, which enables packets to be queued and served fairly. The results indicate that our proposed algorithms achieve good performances and capacity gains.

User satisfaction based scheduling algorithm for high-speed wireless networks

High-Speed Downlink Packet Access (HSDPA) is an emerging wireless cellular-based system that promises a peak data rate of up to 14 Mbps. HSDPA relies on new technologies that make it possible to achieve such high data rate. These new technologies include: adaptive modulation and coding, hybrid automatic repeat request, fast cell selection and fast packet scheduling. In this paper, we propose an efficient packet scheduling algorithm for HSDPA to provide priority scheduling between non-real time services of different Quality of Service (QoS) classes and fairness between users within the same class. Simulation results show that the proposed algorithm meets QoS requirements of different non-real time traffic classes, with the proposed algorithm having a better performance compared to existing algorithm, Max-CIR, in the literature.

Network Coding scheme behavior in a Vehicle-to-Vehicle safety message dissemination

Message dissemination is considered as a challenging task in Vehicular Ad-hoc network (VANET). In particular, safety messages, such as, road accident warning, traffic congestion warning, etc., are the most critical messages type that need to be efficiently transmitted in a wireless and mobile network where the topology changes dynamically. Many protocols have been proposed for the sake of disseminating information with a high data reachability and a low end-to-end delay in a limited bandwidth. In this work, we focus on a new trend of dissemination protocols based on the “Network Coding” (NC) scheme. Precisely, we intent to study the NC gain toward safety message dissemination and deduce its suitability in accordance to such application requirements. To this end, three NC-based protocols are proposed for the aim at thoroughly studying the impact of such technique on the safety message dissemination performance. The gain of NC scheme is studied under different traffic densities (from low to high dense network). The simulation results show that NC could be an efficient solution to overcome the intermittent connectivity in sparse network mainly for comfort applications but not suitable for safety message dissemination, especially in high dense network, since it may introduce a high transmission delay.

Network coding-based dissemination protocols for inter-vehicle communication

Inter-vehicle communication or vehicle to vehicle (V2V) communication is becoming a challenging issue for most Vehicular Ad-Hoc Networks (VANETs) applications, where data are needed to be disseminated. In this context, many protocols have been proposed in an attempt to give an efficient dissemination design. In this paper, we propose to review a special class of dissemination protocols that relays on the network coding technique. This technique, recently deployed in wireless ad hoc networks, has theoretically proved its benefits in message dissemination in vehicular environment. The aim of this work is to enumerate the different network coding-based dissemination protocols and to classify them in order to reveal the strengths and the limits of this trend of protocols. At the end a comparison table of the all considered protocols is presented.

Enhanced Relay Selection and Scheduling for Better Load Balancing in Multi-Hop Networks

Relaying technology is likely to bring real progress to the next generation cellular networks due to its capability of boosting the system capacity and coverage. However, despite recent advances in relay deployment, some challenging problems still remain such as radio resource allocation and relay selection. The authors investigate both relay selection and scheduling strategy in order to improve the system radio capacity as well as the network load balancing. They propose a new path selection scheme based on the radio channel quality and the relay station load criteria. Performance analysis showed that the authors approach outperforms the existing path selection algorithms in terms of outage probability and global throughput in the system, especially in high traffic conditions. It is revealed that most of the cell edge users which would be rejected when applying common selection scheme, can now have access to a selected relay station and achieve a high end-to-end throughput. A new scheduling strategy is proposed in the second part of this paper, on the basis of a dynamic subframe partitioning. Simulation results show that the outage probability is reduced and more balanced resource allocation is provided. Simulation results showed that some relay stations which were not able to offer any service with the fixed subframe partitioning, can achieve a high data rate with the authors proposed dynamic scheduling strategy.