Guy Juanole

Gateway Selection in Backbone Wireless Mesh Networks

IEEE 802.11-based backbone mesh networks comprise of static Wireless Mesh Routers (WMRs) which create a wireless multihop backbone to provide high-speed last-mile wireless Internet access to communities. Specialized WMRs called Gateways provide the interconnection between the mesh network and fixed IP networks. Mesh routers perform backhaul routing and may additionally serve as Access Points (APs) for clients. Their main task is to maintain backhaul mesh connectivity and find routes to gateways for clients. An important research problem which has received little attention is the optimal selection of gateway and the route to that gateway by mesh routers within the mesh backbone. We propose an efficient gateway and route selection scheme for backbone mesh networks which can be adopted for upcoming 802.11s mesh standard [1] with minimal changes. Gateway load, route interference and path quality metrics are used to select the best available gateway and the route to that gateway. Simulation results show improved performance compared to schemes using nearest gateway, gateway load metric or the ETX [2] metric for gateway selection.

An Interference and Link-Quality Aware Routing Metric for Wireless Mesh Networks

This paper presents the expected link performance (ELP) metric for finding high throughput, low delay paths in 802.11 mesh networks. ELP combines three different mechanisms to accurately determine the expected link performance. Link quality information is combined with cross-layered link interference estimation to select optimal paths. Simulation results show that ELP significantly outperforms both hop count as well as the popular ETX metric. ELP has up to 12% higher throughput and about 40% smaller delay than ETX.

Route selection in IEEE 802.11 wireless mesh networks

This paper addresses the problem of route selection in IEEE 802.11 based Wireless Mesh Networks (WMNs). Traditional routing protocols choose the shortest path between two routers. However, recent research reveals that there can be enormous differences between links in terms of quality (link loss ratio, interference, noise etc) and therefore selecting the shortest path (hop count metric) is a poor choice. We propose a novel routing metric—Expected Link Performance (ELP) metric for wireless mesh networks which takes into consideration multiple factors pertaining to quality (link loss ratio, link capacity and link interference) to select the best end-to-end route. Simulation based performance evaluation of ELP against contemporary routing metrics shows an improvement in terms of throughput and delay. Moreover, we propose an extension of the metric called ELP-Gateway Selection (ELP-GS) which is an extension meant for traffic specifically oriented towards the gateway nodes in the mesh network. We also propose a gateway discovery protocol which facilitates the dissemination of ELP-GS in the network. Simulation results for ELP-GS show substantial improvement in performance.

Efficient route maintenance in wireless mesh networks

In this paper, we address the problem of route fragility in backhaul wireless mesh networks. Mesh routing protocols rely on intermediate nodes in the multihop path to forward data and detect route breakage. An intermediate node reports the link to next hop as broken after a fixed number of unsuccessful packet transmission attempts at the MAC layer. Transmission failure of a single packet on any link in the multihop path thus renders the route unusable. In practice, many transmission failures are isolated and temporary, caused by transient congestion on the wireless link. False route failures triggered by temporary transmission failures render otherwise good routes as unusable and degrade performance. We propose a novel route maintenance mechanism Congestion Aware Routing (CAR) which addresses this problem and makes a more dasiainformedpsila decision about the link status. CAR uses estimation of medium congestion and the frequency and distribution of link failures to distinguish between broken (or poor quality) links from those experiencing temporary losses. Simulation results for TCP traffic show that CAR can provide up to 15% higher throughput, 50% delay reduction with 8 times smaller routing overhead.

Route Maintenance in IEEE 802.11 wireless mesh networks

In this paper, we propose a novel Route Maintenance scheme for IEEE 802.11 wireless mesh networks. Despite lack of mobility and energy constraints, reactive routing protocols such as AODV and DSR suffer from frequent route breakages in 802.11 based infrastructure wireless mesh networks. In these networks, if any intermediate node fails to successfully transmit a packet to the next hop node after a certain number of retransmissions, the link layer reports a transmission problem to the network layer. Reactive routing protocols systematically consider this as a link breakage (and therefore a route breakage). Transmission failures can be caused by a number of factors e.g. interference or noise and can be transient in nature. Frequent route breakages result in significant performance degradation. The proposed mechanism considers multiple factors to differentiate between links with transient transmission problems from those links which have permanent transmission problems and takes a coherent decision on link breakage. The proposed mechanism is implemented in AODV for single-radio single-channel mesh network and an extension is incorporated in multi-radio multi-channel scenarios. Simulation results show substantial performance improvement compared to classical AODV and local route repair schemes.

An Uplink Bandwidth Management Framework for IEEE 802.16 with QoS Guarantees

This paper presents a novel uplink bandwidth management framework for IEEE 802.16 WiMAX. This framework is destined to be used in a scenario where a large number of connections are simultaneously active, as may be the case when WiMAX is used as a backhaul for WiFi hotspots. In such a scenario we propose a simple and efficient scheduling discipline for the WiMAX uplink traffic. We also propose an admission control algorithm and a modification of the complex bandwidth request mechanisms. The framework we propose in this paper was analyzed: simulation results show a significant performance improvement in terms of overall throughput and delay when compared to recently published work.

Hybrid Admission Control Algorithm for IEEE 802.11e EDCA: Analysis

One of the main quality of service mechanisms, allowing mainly the protection of already active flows, is admission control. This is even truer on the MAC level of 802.11 based networks due to scarce resources. We present in this paper a hybrid admission control algorithm for IEEE 802.11e EDCA. The algorithm uses the synthetic Markov chain model of EDCA that we developed in previous work injecting into it network state measurements. Simulations and results presented in this paper show a good protection of admitted flows and a good utilization of the network resources.

Proposal of a Novel Bandwidth Management Framework for IEEE 802.16 Based on Aggregation

In an environment where IEEE 802.16 access networks are used as a backbone for a heterogeneous wireless access network, the question of Quality of Service brings along a questioning on several other aspects: scalability, guarantees, scheduling among others. We give in this paper a general solution answering those questions. This solution is based on an aggregated bandwidth management in the backbone. This aggregation along with specific bandwidth request and scheduling policies are herein specified and discussed.

Interference-Aware Bandwidth Reservation in multi-radio multi-channel mesh networks

In this paper, we propose the Interference-Aware Bandwidth Reservation (IABR) scheme for providing flow admission control and bandwidth reservation for end-to-end flows in 802.11 multi-radio multi-channel wireless mesh networks. The effects of inter-flow and intra-flow interference have often been neglected in existing solutions, which can lead to inaccurate bandwidth estimation and reservation. IABR models both the current inter-flow interference from existing flows and the expected intra-flow interference of the incoming flow to make accurate estimation of the available bandwidth and perform admission control. Moreover, IABR exploits wireless link diversity between neighboring nodes in multi-radio multi-channel mesh networks to improve flow admission ratio and ensure efficient load-balancing. Simulation results show that IABR provides accurate bandwidth estimation, excellent load distribution and high flow admission ratio.

Formal modelling and verification of the common hopping multi-channel MAC protocols

The use of multiple channels in MAC protocols offers a great potentiality for improving the network throughput. But consequently to the multi-channel aspect and with respect to a mono-channel network, a MAC protocol has now a supplementary function which is the channel assignment. There are many variations for the channel assignment which have been defined and studied in the literature. However, there are few studies with formal models and verification techniques for analysis of these protocols. The goal of this paper is precisely to propose a formal modelling and verification of the multi-channel MAC protocols based on the common hopping approach using Stochastic Timed Petri Net (STPN). We verify the properties of the common hopping pattern (rendezvous) of all nodes and the resynchronization of the sender and receiver nodes on the common hopping sequence after the end of a successful transmission.