Mohamed Naimi

Toward an improvement of H.264 video transmission over IEEE 802.11e through a cross-layer architecture

The recently developed H.264 video standard achieves efficient encoding over a bandwidth ranging from a few kilobits per second to several megabits per second. Hence, transporting H.264 video is expected to be an important component of many wireless multimedia services, such as video conferencing, real-time network gaming, and TV broadcasting. However, due to wireless channel characteristics and lack of QoS support, the basic 802.11-based channel access procedure is merely sufficient to deliver non-real-time traffic. The delivery should be augmented by appropriate mechanisms to better consider different QoS requirements and ultimately adjust the medium access parameters to the video data content characteristics. In this article we address H.264 wireless video transmission over IEEE 802.11 WLAN by proposing a robust cross-layer architecture that leverages the inherent H.264 error resilience tools (i.e., data partitioning); and the existing QoS-based IEEE 802.11e MAC protocol possibilities. The performances of the proposed architecture are extensively investigated by simulations. Results obtained indicate that compared to 802.11 and 802.11e, our cross-layer architecture allows graceful video degradation while minimizing the mean packet loss and end-to-end delays.

A distributed energy aware routing protocol for wireless sensor networks

Future sensor networks will be composed of a large number of densely deployed sensors. A key feature of such networks is that their nodes have a limited battery power and they are unattended. Consequently, energy efficiency is an important design consideration for these networks. In this paper, we propose a Distributed Energy-efficient Clustering Hierarchy Protocol (DECHP), which distributes the energy dissipation evenly among all sensor nodes to improve network lifetime and average energy savings. The performance of DECHP is then compared to clustering-based schemes such as Low-Energy Adaptive Clustering Hierarchy (LEACH), LEACH-Centralized (LEACH-C), and Power-Efficient Gathering in Sensor Information Systems (PEGASIS). Simulation results show that DECHP reduces overall energy consumption and improves network lifetime over its comparatives.

Adaptive service differentiation for QoS provisioning in IEEE 802.11 wireless ad hoc networks

The proposed scheme IEEE 802.11e draft standard defines new MAC protocol for QoS in wireless networks, namely HCF and EDCF. EDCF is a contention based channel access scheme and is part of HCF for infrastructure networks and may be used as a separate coordination function for wireless Ad-hoc networks. In this paper we propose to enhance EDCF with a dynamic traffic classs management protocol, which allows firstly, a guarantee of QoS to the sensitive applications some as the network state. Secondly, a sliding QoS differentiation between the Traffic Classes (TC) according to the instantaneous channels fluctuations. This sliding differentiation is based on a dynamic tune of the IEEE 802.11 MACs parameters. The performances of the proposed scheme namely AMPA (Adaptive MAC Parameters), are extensively investigated by simulations. Results obtained indicate that AMPA scheme outperforms both DCF and EDCF.

Improving H.264 video transmission in 802.11e EDCA

Multimedia streaming over wired network, such as the Internet, has been popular now for quite some time. Further, as the bandwidth of wireless technologies have increased, consideration has only recently turned to delivering video over wireless networks. Meanwhile, an emerging new video compression standard namely H.264 is widely accepted. The H.264 standard outperforms all previous video compression, and can deliver high video quality at low rate. However, due to wireless channel characteristics, it is insufficient to merely deliver video data; instead delivery must consider also an adaptation of the video data to the networks specific and particularly network friendliness. In this paper, we address H.264 wireless video transmission over IEEE 802.11 wireless LAN by proposing a robust cross layer architecture which exploits: (i) the new standard IEEE 802.11e MAC protocol; (ii) the H.264 error resilience tools, namely data partitioning. The performances of the proposed architecture are extensively investigated by simulations. Results obtained indicate that our architecture can reliably transport the H.264 video stream, while the actual IEEE 802.11 standard in the same conditions, degrades considerably the transmitted video.

Efficient Energy Saving in Wireless Sensor Networks Through Hierarchical-based Clustering

Prolonged network lifetime, scalability, and load balancing are important requirements for many wireless sensor network applications. Clustering sensor nodes is an effective approach for achieving these goals. In this paper, we propose a Distributed Energy-efficient Clustering-based Hierarchy Protocol (DECHP), which distributes the energy dissipation evenly among all sensor nodes to improve network lifetime and average energy savings. The performance of DECHP is then compared to different clustering-based schemes. Simulation results show that DECHP reduces overall energy consumption and improves network lifetime over its comparatives.

Novel architecture for reliable H.26L video transmission over IEEE 802.11e

Today the great challenge to the IEEE 802.11 wireless LAN is to support real time and multimedia applications. However, the characteristics of wireless channel (low and fluctuating bandwidth link and the large error rate) post different problems in supporting the requirements on QoS (bandwidth, delays, jitters) of these sensitive applications. We focus on the JVC H.26L video encoder, the wireless LAN and their interaction in QoS. The interaction is made by the guarantee of a reliable H.26L video transport over the IEEE 802.11 wireless LAN. In this context, we propose a novel cross layer architecture. This architecture is based on a marking scheme, which exploits the new propositions of the IEEE 802.11 E group for supporting QoS.

A clustering Group Mutual Exclusion algorithm for mobile ad hoc networks

A mobile ad hoc network can be defined as a network that is spontaneously deployed and is independent of any static network. The network consists of mobile nodes1 with wireless interfaces and has an arbitrary dynamic topology. The networks suffers from frequent link formation and disruption due to the mobility of the nodes. A clustering method is used for obtaining a hierarchical organization for the ad hoc networks. In this paper we present a clustering token based algorithm for Group Mutual Exclusion in ad hoc mobile networks. The proposed algorithm is adapted from the RL algorithm in [1] and utilizes the concept of weight throwing in [2]. The proposed algorithm is sensitive to link forming and link breaking. The algorithm ensures the mutual exclusion, the bounded delay, and the concurrent entering properties.

A new IEEE 802.11 MAC protocol with admission control for sensitive multimedia applications

Actually, the quality of service (QoS) provisioning in IEEE 802.11-based wireless network is assured by the enhanced coordination channel access (EDCA) mechanism, which lacks the aptitude to ensure: (i) an intra-QoS differentiation between the access class (AC), where flows belonging to the same service class are assigned the same MAC parameters regardless theirs respective bit rate, which leads to throughput fairness rather than perceived QoS fairness; (ii) an admission control mechanism that manages the network traffic. In this paper we propose a new MAC protocol featuring a dynamic reservation of the wireless channel (by using the TXOPlimit parameter) along with a distributed admission control mechanism. By monitoring the MAC queue, each flow computes at runtimes the TXOPlimits value that satisfies the application requested data rate. Meanwhile we specify a fully distributed admission control mechanism that regulates the network load and protects the admitted flows from the new ones. Simulation results show that compared to the EDCA scheme of 802.1 Ie, our protocol excels, in terms of network utilization and ability to maintain intra-QoS data rate differentiation. Further when introducing the admission control mechanism, we ensure high protection to the admitted flows, and maintain the network in steady state

Distributed Groups Mutual Exclusion Based on Clients/Servers Model

In this paper we present a new distributed group mutual exclusion (DGME) based on clients/servers model, and uses a dynamic data structures. Several processes (clients) can access simultaneously to a same opened session (server). The algorithm ensures that, at any time, at most one session is opened, and any requested session will be opened in a finite time. The number of messages is between 0 and m, where m is the number of session in the network. In the average case, O(Log(m)) messages are necessary to open a session. The maximum concurrency is n, where n is the number of processes in the network

A Group k-Mutual Exclusion Algorithm for Mobile Ad Hoc Networks

A mobile ad hoc network can be defined as a network that is spontaneously deployed and is independent of any static network. The network consist of mobile nodes with wireless interfaces and has an arbitrary dynamic topology. In this paper we present a toke- based group k -mutual exclusion algorithm for mobile ad hoc networks. The Gk -ME problem is concerned with controlling the concurrent accesses of some resources by at most k nodes with the constraint that no two distinct resources can be accessed simultaneously. The proposed algorithm is adapted from the RL algorithm. The algorithm ensures the mutual exclusion, the bounded delay, and the k -concurrent entering property.