SBA : un algorithme simple de backoff pour les réseaux ad hoc

National audienceLes performances d'un réseau ad hoc utilisant 802.11 se dégradent quand la charge du réseau augmente. Cette surcharge du réseau peut provenir de sa densité ou du trafic généré. La perte de performance vient essentiellement du protocole MAC (Medium Access Control) mis en place dans le mode DCF du standard 802.11. On trouve dans la littérature plusieurs solutions au niveau MAC permettant de maintenir les performances telles que l'équité ou l'efficacité mais peu de ces solutions n'abordent le problème de l'équité et de l'efficacité conjointement. Dans cet article nous proposons un algorithme de backoff, SBA (Simple Backoff Algorithm), permettant d'obtenir un bon compromis équité-efficacité quand le réseau est surchargé. De plus, notre algorithme est simple car il ne s'appuie que sur des informations locales. L'analyse et les simulations montrent que SBA permet d'obtenir un meilleur compromis entre équité, efficacité et simplicité comparé à certains protocoles décrits dans la littérature

SBA: A Simple Backoff Algorithm for Wireless Ad Hoc Networks

International audienceThe performance of ad hoc networks based on IEEE 802.11 DCF degrade when congestion increases. The issues concern efficiency and fairness. Many solutions can be found at the MAC layer in the literature, but very few solutions improve fairness and efficiency at the same time. In this paper, we design a new backoff solution, called SBA. SBA uses only local information and two contention window sizes. By simulations, we compare SBA with IEEE 802.11 and several alternatives to 802.11 in ad hoc networks. We show that SBA achieves a good trade-off between fairness, simplicity and efficiency

Traffic integration in personal, local and geograhical wireless networks

Currently, users identify wireless networks with the first and second generation of cellular-telephony networks. Although voice and short messaging have driven the success of these networks so far, data and more sophisticated applications are emerging as the future driving forces for the extensive deployment of new wireless technologies. In this chapter we will consider future wireless technologies that will provide support to different types of traffic including legacy voice applications, Internet data traffic, and sophisticated multimedia applications. In the near future, wireless technologies will span from broadband wide-area technologies (such as satellite-based network and cellular networks) to local and personal area networks. Hereafter, for each class of networks, we will present the emerging wireless technologies for supporting service integration. Our overview will start by analyzing the Bluetooth technology that is the de-facto standard for Wireless Personal Area Networks (WPANs), i.e. networks that connect devices placed inside a circle with radius of 10 meters. Two main standards exist for Wireless Local Area Networks (WLANs): IEEE 802. and HiperLAN. In this chapter we focus on the IEEE 802.11 technology, as it is the technology currently available on the market. In this chapter, after a brief description of the IEEE 802.11 architecture, we will focus on the mechanisms that have been specifically designed to support delay sensitive traffics

SBA : un algorithme simple de backoff pour les réseaux ad hoc

National audienceLes performances d'un réseau ad hoc utilisant 802.11 se dégradent quand la charge du réseau augmente. Cette surcharge du réseau peut provenir de sa densité ou du trafic généré. La perte de performance vient essentiellement du protocole MAC (Medium Access Control) mis en place dans le mode DCF du standard 802.11. On trouve dans la littérature plusieurs solutions au niveau MAC permettant de maintenir les performances telles que l'équité ou l'efficacité mais peu de ces solutions n'abordent le problème de l'équité et de l'efficacité conjointement. Dans cet article nous proposons un algorithme de backoff, SBA (Simple Backoff Algorithm), permettant d'obtenir un bon compromis équité-efficacité quand le réseau est surchargé. De plus, notre algorithme est simple car il ne s'appuie que sur des informations locales. L'analyse et les simulations montrent que SBA permet d'obtenir un meilleur compromis entre équité, efficacité et simplicité comparé à certains protocoles décrits dans la littérature

Optimization of Efficiency and Energy Consumption in p-persistent CSMA-based Wireless LANs

Wireless technologies in the LAN environment are becoming increasingly important. The IEEE 802.11 is the most mature technology for Wireless Local Area Networks (WLANs). The limited bandwidth and the finite battery power of mobile computers represent one of the greatest limitations of current WLANs. In this paper we deeply investigate the efficiency and the energy consumption of MAC protocols that can be described with a p-persistent CSMA model. As already shown in the literature, the IEEE 802.11 protocol performance can be studied using a p-persistent CSMA model [Cal00]. For this class of protocols, in the paper we define an analytical framework to study the theoretical performance bounds from the throughput and the energy consumption standpoint. Specifically, we derive the p values (i.e., the average size of the contention window in the IEEE 802.11 protocol) that maximizes the throughput, $p^C_{opt}$, and minimizes the energy consumption, $p^E_{opt}$. By providing analytical closed formulas for the optimal values, we discuss the trade-off between efficiency and energy consumption. Specifically, we show that power saving and throughput maximization can be jointly achieved. Our analytical formulas indicate that the optimal $p$ values depend on the network configuration, i.e., number of active stations and length of the messages transmitted on the channel

Hybrid routing and bridging strategies for large scale mobile ad hoc networks

Multi-hop packet radio networks (or mobile ad-hoc networks) are an ideal technology to establish instant communication infrastructure for military and civilian applications in which both hosts and routers are mobile. In this dissertation, a position-based/link-state hybrid, proactive routing protocol (Position-guided Sliding-window Routing - PSR) that provides for a flat, mobile ad-hoc routing architecture is described, analyzed and evaluated. PSR is based on the superposition of link-state and position-based routing, and it employs a simplified way of localizing routing overhead, without having to resort to complex, multiple-tier routing organization schemes. A set of geographic routing zones is defined for each node, where the purpose of the ith routing zone is to restrict propagation of position updates, advertising position differentials equal to the radius of the (i-i )th routing zone. Thus, the proposed protocol controls position-update overhead generation and propagation by making the overhead generation rate and propagation distance directly proportional to the amount of change in a node\u27s geographic position. An analytical model and framework is provided, in order to study the various design issues and trade-offs of PSR routing mechanism, discuss their impact on the protocol\u27s operation and effectiveness, and identify optimal values for critical design parameters, under different mobility scenarios. In addition an in-depth performance evaluation, via modeling and simulation, was performed in order to demonstrate PSR\u27s operational effectiveness in terms of scalability, mobility support, and efficiency. Furthermore, power and energy metrics, such as path fading and battery capacity considerations, are integrated into the routing decision (cost function) in order to improve PSR\u27s power efficiency and network lifetime. It is demonstrated that the proposed routing protocol is ideal for deployment and implementation especially in large scale mobile ad hoc networks. Wireless local area networks (WLAN) are being deployed widely to support networking needs of both consumer and enterprise applications, and IEEE 802.11 specification is becoming the de facto standard for deploying WLAN. However IEEE 802.11 specifications allow only one hop communication between nodes. A layer-2 bridging solution is proposed in this dissertation, to increase the range of 802.11 base stations using ad hoc networking, and therefore solve the hotspot communication problem, where a large number of mobile users require Internet access through an access point. In the proposed framework nodes are divided into levels based on their distance (hops) from the access point. A layer-2 bridging tree is built based on the level concept, and a node in certain level only forwards packets to nodes in its neighboring level. The specific mechanisms for the forwarding tree establishment as well as for the data propagation are also introduced and discussed. An analytical model is also presented in order to analyze the saturation throughput of the proposed mechanism, while its applicability and effectiveness is evaluated via modeling and simulation. The corresponding numerical results demonstrate and confirm the significant area coverage extension that can be achieved by the solution, when compared with the conventional 802.1 lb scheme. Finally, for implementation purposes, a hierarchical network structure paradigm based on the combination of these two protocols and models is introduced