Distributed optimal congestion control and channel assignment in wireless mesh networks

Wireless mesh networks have numerous advantages in terms of connectivity as well as reliability. Traditionally the nodes in wireless mesh networks are equipped with single radio, but the limitations are lower throughput and limited use of the available wireless channel. In order to overcome this, the recent advances in wireless mesh networks are based on multi-channel multi-radio approach. Channel assignment is a technique that selects the best channel for a node or to the entire network just to increase the network capacity. To maximize the throughput and the capacity of the network, multiple channels with multiple radios were introduced in these networks. In the proposed system, algorithms are developed to improve throughput, minimise delay, reduce average energy consumption and increase the residual energy for multi radio multi-channel wireless mesh networks. In literature, the existing channel assignment algorithms fail to consider both interflow and intra flow interferences. The limitations are inaccurate bandwidth estimation, throughput degradation under heavy traffic and unwanted energy consumption during low traffic and increase in delay. In order to improve the performance of the network distributed optimal congestion control and channel assignment algorithm (DOCCA) is proposed. In this algorithm, if congestion is identified, the information is given to previous node. According to the congestion level, the node adjusts itself to minimise congestion

Interference Mitigation Based on Radio Aware Channel Assignment for Wireless Mesh Networks

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. An intricate network deployment for high demand users leads to simultaneous transmission in wireless mesh networks. Multiple radios are adapted to individual nodes for improving network performance and Quality of Service (QoS). However, whenever multiple radios are assigned to the same channel, co-located radio interference occurs, which poses a major drawback. This paper proposes a Radio aware Channel Assignment (Ra-CA) mechanism based on a direct graphical model for mitigation of interference in multi-radio multi-channel networks. Initially, the co-located radio interference is identified by classifying non-interfering links for simultaneous transmission in the network. Proposed channel assignment mechanism helps in allocating the minimal number of channels to the network that mitigate co-located radio interference. Performance analysis of the proposed Ra-CA strategy is carried out compared with other existing techniques, like Breadth First Search-Channel Assignment (BFS-CA) and Maximal Independent Set Channel Assignment (MaIS-CA), in multi-radio networks. Simulation results demonstrate that the proposed channel assignment scheme is more efficient compared to the existing ones, in terms of QoS parameters like, packet drop rate, packet delivery ratio, transmission delay and throughput

Scalable and interference aware wi-fi mesh networks using cots devices

A crescente tendencia no acesso móvel tem sido potenciada pela tecnologia IEEE 802.11. Contudo, estas redes têm alcance rádio limitado. Para a extensão da sua cobertura é possível recorrer a redes emalhadas sem fios baseadas na tecnologia IEEE 802.11, com vantagem do ponto de vista do custo e da flexibilidade de instalação, face a soluções cabladas. Redes emalhadas sem fios constituídas por nós com apenas uma interface têm escalabilidade reduzida. A principal razão dessa limitação deve-se ao uso do mecanismo de acesso ao meio partilhado Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) em topologias multi-hop. Especificamente, o CSMA/CA não evita o problema do nó escondido levando ao aumento do número de colisões e correspondente degradação de desempenho com impacto direto no throughput e na latência. Com a redução da tecnologia rádio torna-se viável a utilização de múltiplos rádios por nó, sem com isso aumentar significativamente o custo da solução final de comunicações. A utilização de mais do que um rádio por nó de comuniações permite superar os problemas de desempenho inerentes ás redes formadas por nós com apenas um rádio. O objetivo desta tese, passa por desenvolver uma nova solução para redes emalhadas multi-cana, duar-radio, utilizando para isso novos mecanismos que complementam os mecanismos definidos no IEEE 802.11 para o estabelecimento de um Basic Service Set (BSS). A solução é baseada na solução WiFIX, um protocolo de routing para redes emalhadas de interface única e reutiliza os mecanismos já implementados nas redes IEEE 802.11 para difundir métricas que permitam à rede escalar de forma eficaz minimizando o impacto na performance. A rede multi-hop é formada por nós equipados com duas interfaces, organizados numa topologia hierárquica sobre múltiplas relações Access Point (AP) – Station (STA). Os resultados experimentais obtidos mostram a eficácia e o bom desempenho da solução proposta face à solução WiFIX original.The increasing trend on mobile access has been mainly potentied for IEEE 802.11 technology. However these networks suffer from reduced radio range. The extension of coverage can be potentiated by mesh deployments since they provide an ease, robust, flexible and cost effective solution for this problem. These networks are built upon nodes scattered in a mesh topology that form the backbone of an extended basic service set. Single radio Wireless Mesh Networks (WMN) however suffer from reduced scalability. The main reason to such limitation is the use of Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) in the multi-hop topology. Specifically, CSMA/CA fails to prevent the hidden and exposed node occurrence, which respectively, lead to an increase on the number of collisions and flow retentions. The direct impact on throughput and latency reduces the overall network performance to values that no longer match user increasing demands. As radio technology becomes cheaper, it became possible to equip nodes with multiple interfaces and operate them in multiple channels in order the reduce interference from links operating on a common channel. Therefore the goal of this thesis is to develop a new WMN Multi-Radio Multi-Channel (MRMC) solution addressing new mechanisms not yet covered in state of art. The proposed solution, is based on WiFIX, a Single Radio (SR) WMN routing protocol and reuses the mechanisms already implemented in IEEE 802.11 networks to broadcast metrics that enable the network to auto-configure efficiently and to scale with minimum overhead. The multi-hop backbone is formed by nodes equipped with two interfaces disposed in a hierarchical topology, under multiple Access Point (AP) - Station (STA) relations. The results obtained from an experimental testbed clearly show the effectiveness of the solution compared with the original WiFIX and its capability to scale resulting from the overhead control and co-channel interference reduction