Leila Azzouz Saidane

Performance evaluation of IEEE 802.15.6 CSMA/CA-based CANet WBAN

In the recent few years, Wireless Body Area networks (WBANs) showed what can be done remotely to greatly improve healthcare systems and facilitate the life to elderly. One of the recent ehealth projects is CANet which aims at embedding a WBAN into a cane to monitor elderly/patients. Our main goal in this paper is to evaluate the performances of the emerging standard IEEE 802.15.6 when applied on different sensors from CANet eHealth project. At this end, we defined a small scenario extracted from CANet, and we assigned IEEE 802.15.6 priorities to the selected cane sensors according to their inherent characteristics. We considered further the mandatory RAP period of IEEE 802.15.6 superframe under the beacon period with superframes mode since it supports both normal and urgent traffic. Our results showed that the contention access behavior of this considered model of simulation depends on several constraints (including the nature of the studied application and the traffic types and frequency). This would be necessarily taken into account to get the most advantage of all features offered by WBANs standard IEEE 802.15.6.

Towards an optimised traffic-aware routing in wireless mesh networks

In this paper we study through simulations the impact of PHY/MAC protocols on higher layers. In a comparative way, we investigate the effectiveness of some protocols when they coexist on a wireless mesh network environment. Results show that PHY/MAC parameters have an important impact on routing performances. Based on these results, we propose two tra c-aware routing metrics based on link availability. The information about the link availability/occupancy is picked up from lower layers using a cross-layer approach. The rst metric is load-sensitive and aims to balance the tra c load according to the availability of a link to support additional ows. The second metric reproduces better the capacity of a link since it is based on its residual bandwidth. Using several real experiments, we have shown that our proposals can accurately determine better paths in terms of throughput and delay. Our experiments are carried out into an heterogeneous IEEE 802.11n based network running with OLSR routing protocol.

Impact of IEEE 802.11 PHY/MAC Strategies on Routing Performance in Wireless Mesh Networks

Current routing mechanisms proposed for adhocnetworks are still feasibly applied in Wireless Mesh Networks given their similarities. Many researchers have conducted numerous simulations for comparing the performances of these routing protocols under various conditions and constraints. Most made comparisons are not aware of PHY/MAC layers and their impact on routing performances. In this paper we study through simulations the impact of PHY/MAC protocols on higher layers. The considered protocols include three propagation models, i.e., Free Space, TwoRayGround and Shadowing, three different PHY/MAC protocols specified IEEE 802.11 standards namely, 802.11b, 802.11s and 802.11n, and finally three routing protocols, i.e., AODV, OLSR and HWMP. In a comparative way, we investigate the effectiveness of these protocols when they coexist on a wireless mesh network environment. Our results show that the routing strategy can significantly impact the network performance only if it is strongly linked to the characteristics of the lower layers.

Experimental performance analysis of routing metrics in Wireless Mesh Networks

This paper provides a description of a wireless mesh network testbed setup and a measurement-based performance evaluation of the Optimized Link State Routing (OLSR) protocol [7] under three different routing metrics. The considered metrics include hop-count, ETX and ETT. The network performances are evaluated in an indoor testbed formed by heterogeneous MIMO devices. A part of our tests was about the impact of 802.11n features on the network performances showing the importance of lower layers consideration. Our measurements point out the shortcoming of each metric and eventual optimizations towards a more efficient routing. Experimental results show that OLSR-ETT outperforms OLSR-ETX and OLSR-hopcount significantly in terms of packet loss, end-to-end delay, and efficiency.

A survey on quality of service in cloud computing

The quality of service is one of challenges posed by the Cloud Computing. This issue plays an important role in making the Cloud services acceptable to customers, denotes the levels of performance, reliability, and availability offered by Cloud services. Literature has reported many implementations for measuring and ensuring QoS in Cloud Computing systems to achieve better results and meet the needs of producers and consumers. In this paper, we have presented a survey on QoS in Cloud Computing, the mechanisms and methods to guarantee quality of service (QoS) used to Cloud Computing services.

Optimisation of IEEE 802.15.4: overview, theoretical study and simulation

In this paper we study, through theoretical analysis and simulation, the impact of beacon order (BO) and superframe order (SO) parameters of IEEE 802.15.4 on the networks performance and we investigate their optimal values for different classes of traffic. The traffic is dimensioned according to the requirements of the CANet project in which a cane becomes a mean of communication and a surveillance system embedding several sensors to monitor the elderly health and environment(voice, pressure, temperature, etc.). The canes sensors impose different QoS constraints. Depending on the expected throughput, a sensors traffic will fall within one of three classes that we defined. Therefore, in order to ease the understanding of our optimisation, we introduce a classification scheme which applies to the existing quality of service algorithms. We derive by theoretical study the optimal values of BO and SO that should be used to fit each traffic class QoS requirements and we validate our results by simulation.

An Optimal Strategy for Collision-Free Slots Allocations in Vehicular Ad-hoc Networks

Research in vehicular ad-hoc networks (VANETs) have attracted a lot of attention in the recent years as emerging wireless technologies have opened up the way to many new exciting applications. VANETs are highly dynamic wireless networks that are designed to support vehicular safety, traffic management, and user-oriented applications. Each vehicle can exchange information to inform other vehicles about the current status or a dangerous situation such as an accident. Detecting and sending information about such situations requires a reliable broadcast service between vehicles, thus increasing the need for an efficient medium access control (MAC) protocol. In this paper, we propose ASAS, an Adaptive Slot Assignment Strategy, which takes advantage of bandwidth spatial reuse and reduces intra-cluster and inter-cluster message collisions without having to use an expensive spectrum and complex mechanisms such as CDMA or FDMA. Cluster heads (CHs) which are elected among the vehicles are then responsible for assigning time slots to the other vehicles in their clusters. The evaluation results show the interest of ASAS in terms of slot reuse and collision rates in different speed conditions.

Novel link availability aware metrics for routing in wireless mesh networks

This paper presents two novel metrics, Link Occupancy aware routing Metric (LOM) and Residual Link Capacity based routing metric with Interference Consideration (RLCIC), for accurately finding high-throughput paths in multihop wireless mesh networks. The first metric is load-sensitive and aims to balance the traffic load according to the availability of a link to support additional flows. The second metric reproduces better the capacity of a link since it is based on its residual bandwidth. It captures accurately the available path bandwidth information when considering both the intra-flow and the interflow interferences. Using several real experiments carried out into an heterogeneous IEEE 802.11n based network running with OLSR routing protocol, we have shown that our first proposal can accurately determine better paths in terms of throughput and delay, thereby significantly outperforming the other existing metrics. The consistency of the second metric RLCIC is proved formally based on notions of graph theory.

Link availability aware routing metric for wireless mesh networks

This paper investigates the design of effective routing metrics in the purpose of network resources optimization and the satisfaction of users QoS requirements. Using several real experiments, we point out the shortcoming of the Expected Transmission Count (ETX) metric for eventual optimizations towards a more efficient routing. Experiments were carried out into an heterogeneous IEEE 802.11n based network running with OLSR routing protocol and have shown that ETX presents several shortcoming resulting in inaccurate estimation of the link quality and then of the routing decision. This paper presents improvements of the ETX metric based on link availibility for accurately finding high-throughput paths in multihop wireless mesh networks.

Satisfying QoS Requirements in NGN Networks Using a Dynamic Adaptive Queuing Delay Control Method

Abstract The Next Generation Networks (NGN) are required to support the seamless delivery of voice, video and data with high quality. One of the most important key features of NGN is Quality of Service (QoS), which has been a focal point of NGN research, development and standardization. In this work, we propose and demonstrate an efficient NGN QoS control method, which guarantees the QoS requirements expressed in terms of per-service traffic flow authorized queuing delay. Multiple service levels are used in order to provide differentiated services and prioritize traffic requiring high-level QoS. The advantages of the proposed method are demonstrated through modeling of the QoS queuing delay parameters. Simulation results are generated to evaluate the performance of the proposed method in terms of supporting the QoS and improving the network scalability based on queuing delay control and adjustment.