Learning-Based Constraint Satisfaction With Sensing Restrictions

In this paper we consider graph-coloring problems, an important subset of general constraint satisfaction problems that arise in wireless resource allocation. We constructively establish the existence of fully decentralized learning-based algorithms that are able to find a proper coloring even in the presence of strong sensing restrictions, in particular sensing asymmetry of the type encountered when hidden terminals are present. Our main analytic contribution is to establish sufficient conditions on the sensing behaviour to ensure that the solvers find satisfying assignments with probability one. These conditions take the form of connectivity requirements on the induced sensing graph. These requirements are mild, and we demonstrate that they are commonly satisfied in wireless allocation tasks. We argue that our results are of considerable practical importance in view of the prevalence of both communication and sensing restrictions in wireless resource allocation problems. The class of algorithms analysed here requires no message-passing whatsoever between wireless devices, and we show that they continue to perform well even when devices are only able to carry out constrained sensing of the surrounding radio environment

A Topology Control-Based Self-Organisation in Wireless Mesh Networks

An algorithm for self-organisation that assigns the channels intelligently in multi-radio wireless mesh networks (MR-WMN) is important for the proper operation of MR-WMN. The aim of the self-organisation algorithm is to reduce the overall interference and increase the aggregate capacity of the network. In this paper, we have first proposed a generic self-organisation algorithm that addresses these two challenges. The basic approach is that of a distributed, light-weight, cooperative multiagent system that guarantees scalability. Second, we have evaluated the performance of the proposed self-organisation algorithm for two sets of initialisation schemes. The initialisation process results in a topology control of MR-WMN by way of spatial distribution of connectivity between the mesh nodes. The results have been obtained for realistic scenarios of MR-WMN node densities and topologies. We have shown in addition the need to develop non-transmit power control based algorithms to achieve a further increase in system capacity

Dynamic Interference Adaptation for Wireless Mesh Networks

ABSTRACT Most wireless meshes will have to operate within the crowded unlicensed spectrum that is also shared by numerous uncoordinated 802.11 hotspot

WLAN Channel Selection Without Communication

In this paper we consider how a group of wireless access-points can self-configure their channel choice so as to avoid interference between one another and thereby maximise network capacity. We make the observation that communication between access points is not necessary, although it is a feature of almost all published channel allocation algorithms. We argue that this observation is of key practical importance as, except in special circumstances, interfering WLANs need not all lie in the same administrative domain and/or may be beyond wireless communication distance (although within interference distance). We demonstrate the feasibility of the communicationfree paradigm via a new class of decentralized algorithms that are simple, robust and provably correct for arbitrary interference graphs. The algorithm requires only standard hardware and we demonstrate its effectiveness via experimental measurements

Uma Análise experimental de alocação de canal para redes sem fio 802.11

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência da Computação, Florianópolis, 2010As redes IEEE 802.11, por operarem em uma faixa de freqüência não licenciada, enfrentam interferências de diversos dispositivos e de outras redes. Tendo isto em vista, somado ao aumento da adoção das tecnologias sem fio, necessitou-se um método eficaz de análise da qualidade do sinal, possibilitando a escolha do melhor canal. Objetivando solucionar o problema, este trabalho apresenta um método de análise da vazão dos canais baseado no histórico de desempenho destes. O trabalho procura projetar, em um futuro próximo, o canal que possibilite uma vazão elevada e estável. Este trabalho se propôs a desenvolver uma solução independente dos clientes e sem a necessidade de comunicação entre pontos de acesso. Tendo em vista que toda comunicação, em uma rede infra-estruturada, é feita através do ponto de acesso, analisou-se então a qualidade do sinal próximo ao ponto de acesso. Uma área que afeta a todos os clientes da rede

Context aware self-configuring wi-fi network

Wireless networks are increasingly popular among end users primarily to provide Internet access services. For this reason it is becoming easier to find highly congested zones with multiple wireless networks. Many of these networks use default settings which causes, in some cases, that some of communication channels in the 2.4GHz band are overused. This document presents the work done to design a context aware self-configuring system which is intended to improve the performance of independent WI-FI networks by avoiding the interference generated by neighboring wireless networks. For the realization of this system were carried out many experiments which show that wireless networks working on the same channels suffer interference among them that reduces the capacity of each network. In addition to these experiments multiple metrics were proposed in an attempt to predict the capacity of a channel. The number of interfering radios and the number of rogue data packets were the two proposed metric that better fit the needs for capacity forecast. From the obtained results a prototype that implements context aware self-configuring system was developed. The proposed algorithm uses a quality value which is calculated from the weighted sum of the two metrics explained before. This prototype was tested against two algorithms (random and static). The results show that the proposed system improves the mean Throughput of the wireless network under realistic conditions

An Autonomous Channel Selection Algorithm for WLANs

IEEE 802.11 wireless devices need to select a channel in order to transmit their packets. However, as a result of the contention-based nature of the IEEE 802.11 CSMA/CA MAC mechanism, the capacity experienced by a station is not fixed. When a station cannot win a sufficient number of transmission opportunities to satisfy its traffic load, it will become saturated. If the saturation condition persists, more and more packets are stored in the transmit queue and congestion occurs. Congestion leads to high packet delay and may ultimately result in catastrophic packet loss when the transmit queue’s capacity is exceeded. In this thesis, we propose an autonomous channel selection algorithm with neighbour forcing (NF) to minimize the incidence of congestion on all stations using the channels. All stations reassign the channels based on the local monitoring information. This station will change the channel once it finds a channel that has sufficient available bandwidth to satisfy its traffic load requirement or it will force its neighbour stations into saturation by reducing its PHY transmission rate if there exists at least one successful channel assignment according to a predicting module which checks all the possible channel assignments. The results from a simple C++ simulator show that the NF algorithm has a higher probability than the dynamic channel assignment without neighbour forcing (NONF) to successfully reassign the channel once stations have become congested. In an experimental testbed, the Madwifi open source wireless driver has been modified to incorporate the channel selection mechanism. The results demonstrate that the NF algorithm also has a better performance than the NONF algorithm in reducing the congestion time of the network where at least one station has become congested