Autonomous Mesh Networks potentially allows for cheaper networks, of use for impoverished areas with poor infrastructure and little interest from service providers for expansion. The subject of wireless mesh networks is interesting for several reasons. Non-reliance, or at the very least reduced reliance on existing infrastructure and service providers gives more control of a network to the users and their communities. These kinds of networks are however conceived to be quite complex to set up, manage and maintain. The goal of this paper was to create an autonomous network without any need for infrastructure, that was relatively easy to configure, use, and performs well. The implementation technique used succeeds at reaching these goals. The script and environment that was constructed makes it easy to set up and join nodes into the network, and the network can increase and decrease in size without affecting the core functionality of the network. The implementation for automatic host discovery makes it simple for anyone with a small amount of knowledge to find and communicate with other hosts, and the network has proven to be resilient to some common ways of tampering.

Multi-radio multi-channel wireless mesh networks (WMNs) have been the focus of numerous research efforts during the past few years. These efforts aimed at extending the utilization of technologies based on the IEEE 802.11 standard in large-scale communities and even for city wide networking. However, mesh nodes in these networks are typically limited in their resources (e.g., bandwidth, power and radio interfaces). Such a limitation has led to an unsatisfactory network performance as well as users dissatisfaction. This dissertation addresses three important performance issues related to WMNs, namely, network performance enhancement, network survivability and green communications. To address the first issue, a novel quality of service (QoS) aware joint channel assignment (CA) and routing algorithm is developed. The proposed algorithm employs both dynamic and static CA techniques and corresponding link schedules that maximize the network throughput and minimize the delay and packet loss ratio. Next, the thesis addresses the problem of network survivability and theoretically analyzes the effects of node failure probabilities on the ability of the remaining network nodes to maintain their connectivity. A tight upper bound on the node failure probabilities needed to maintain full network connectivity on the one hand is first developed. On the other hand, a lower bound, at which the system loses connectivity, is also derived. We show that these bounds are dependent only on the nodes' geometric distribution and density. Based on the premise that failure of nodes in a small area may lead to failure of dependent nodes in other areas due to the quick divergence of traffic in these areas, an efficient node failure backup scheme is presented. The scheme relies on the capacity of the surviving network components in order to find new paths that do not overload the neighbours of the failed node which reduces the probability of generating congestion. Finally, the thesis addresses the problem of realizing energy-efficient WMNs that can operate using renewable energy sources. In these systems, batteries are often used to store and regulate the use of the supplied green energy to transmit the received data at each network router in order to overcome the problem of supply fluctuating of various energy sources. To realize these networks, the behaviour of the residual energy of the battery at a heavily loaded green wireless mesh node with a general traffic arrival and energy charging functions is first analyzed. Based on obtained theoretical results, both an online and an offline QoS aware packet scheduling schemes are proposed to minimize the probability of depleting the battery. Each of the aforementioned contributions is supported with various experimental evaluations to demonstrate the achieved performance enhancements.

Ce travail de thèse présente trois contributions qui portent sur le routage et la fourniture de qualité de service dans les réseaux maillés sans fil basés sur IEEE 802.11. La première contribution définit une métrique de routage qui permet de sélectionner les chemins empruntant des liens avec de bonnes performances exprimées en termes d’interférences physiques (qui causent des pertes), d’interférences logiques (qui causent des délais) et de capacité. L’évaluation de cette métrique par rapport aux principales métriques de la littérature scientifique montre une amélioration des performances du réseau. La deuxième contribution concerne l’amélioration du mécanisme de maintenance de route le plus souvent utilisé par les protocoles de routage réactifs. Ce mécanisme considère qu'une route est coupée si l'un de ses liens observe plusieurs échecs successifs de retransmission. Nos études montrent que ces échecs sont assez souvent dûs à de problèmes transitoires sur les liens (bruit, interférence etc.). Nous avons donc proposé des algorithmes de maintenance de route qui appréhendent mieux les problèmes ponctuels ou soutenus sur les liens ce qui permet de prendre une décision cohérente et réfléchie quant à la coupure d’un lien (et donc d'une route). Les études de performances montrent une amélioration conséquente des performances globales du réseau. La dernière contribution propose un cadre pour la fourniture de la Qualité de Service (garantie de bande passante) dans les réseaux maillés multi-interfaces, multi-canaux. Ce cadre intègre un protocole de routage réactif couplé à un mécanisme de contrôle d'admission et de partage de charge. Ces derniers exploitent la diversité des liens entre nœuds voisins afin d’améliorer le taux d’admission des flux avec garantie de bande passante / This thesis presents three contributions in the area of routing and Quality of Service for IEEE 802.11-based Wireless Mesh Networks. The first contribution defines a routing metric for the selection of route by taking into consideration the performance of wireless links in terms of physical interference (which causes packet losses), logical interference (which causes delay) and the capacity of the links. The performance evaluation of the proposed metric compared to the popular existing metrics shows an improvement in the performance of the network. The second contribution improves the route maintenance mechanism most often used by reactive routing protocols. The existing mechanism considers a route as broken if any of the links in the route experiences multiple successive transmission failures. Our study shows that the transmission failures are often caused by transient problems on the wireless link (noise, interference etc). We propose a novel mechanism of route maintenance which distinguishes between links with temporary or transient transmission problems compared to those with sustained problems in order to make a coherent decision about link breakage (and consequently route breakage). The performance evaluation shows a substantial improvement in the performance of the network. The final contribution proposes a framework for providing Quality of Service (bandwidth guarantee) in multi-radio multi-channel wireless mesh networks. The framework integrates a reactive routing protocol coupled with an admission control mechanism and load balancing. The framework exploits link diversity between neighboring nodes to improve the flow admission ratio with bandwidth guarantees

Thesis (MSc.) -- University of Limpopo, 2017 / The notion of ubiquitous computing, Internet of things (IoT), big data, cloud computing and other emerging technologies has brougt forward the innovative paradigms and incredible developments in wireless communication technologies. The Wireless Mesh Networks (WMNs) technology has recently emerged as the promising high speed wireless technology to provide the last mile broadband Internet access and deliver flexible and integrated wireless communication solutions. The WMNs has the potential to enable people living in rural, peri-urban areas and small businesses to interconnect their networks and share the affordable Internet connectivity. The recent multimedia applications developed, such as voice over Internet protocol (VoIP), online gaming, cloud storage, instant messaging applications, and video sharing applications require high speed communication media and networks. These applications have witnessed enormous growth in the recent decade and continue to enhance communication amongst the users. Hence, the WMNs must have adequate capacity to support high bandwidth and real-time and multimedia applications. While the wireless communications networks are dependent on the radio frequency (RF) spectrum, the traditional wireless technologies utilise the RF spectrum bands inefficiently, resulting in sporadic and underutilisation of the RF spectrum. This inefficient usage of RF spectrum calls for novel techniques to leverage the available RF spectrum amongst different players in the wireless communication arena. There have been developments on integration of the WMNs with cognitive ratios to allow unlicensed users of RF spectrum to operate in the licensed portions of spectrum bands. This integration will provide the required bandwidth to support the required high speed broadband communication infrastructure. In this dissertation, we focus our research on the routing layer in a multi-hop wireless network environment. We addressed the routing challenges in both the WMNs and the cognitive radio based wireless mesh networks (CR-WMNs). The primary focus was to identify the routing protocols most suitable for the dynamic WMN environment. Once identified, the routing protocol was then ported to the CR-WMN environment to evaluate its performance given all the dynamics of cognitive radio environment. vi We further proposed the routing protocol called the extended weighted cumulative expected transmission time (xWCETT) routing protocol for the CR-WMNs. The design of our proposed xWCETT routing protocol is based on the multi-radio multi-channel architecture as it gives the base framework matching the cognitive radio environment. The xWCETT integrates features from the Ad-hoc On-demand Distance Vector (AODV) routing protocol and the weighted cumulative expected transmission time (WCETT) routing metric. The xWCETT was implemented using the Cognitive Radio Cognitive Network (CRCN) patch ported in network simulator (NS2) to incorporate the shared and dynamic spectrum access features. We compared the performance of our proposed xWCETT routing protocol with the AODV, dynamic source routing (DSR), the optimised link source routing (OLSR), Destination Sequences Distance Vector (DSDV), and the CRCN-WCETT routing protocols. The extensive simulation and numerical results show that the proposed xWCETT protocol obtained on average, around 10% better performance results in the CR-WNNs as compared to its routing counterparts. The comparative analysis and evaluation was performed in terms of the average end-to-end latency, throughput, jitter, packet delivery ratio, as well as the normalised routing load. The performance results obtained indicates that the proposed xWCETT routing protocol is a promising routing solution for dynamic CR-WMNs environment. / National Research Foundation (NRF)

Current wireless networks still employ techniques originally designed for their xed wired counterparts. These techniques make assumptions (such as a xed topology, a static enviroment and non-mobile nodes) that are no longer valid in the wireless communication environment. Furthermore, the techniques and protocols used in wireless networks should take the number of users of a network into consideration, since the channel is a shared and limited resource. This study deals with nding an optimal solution to resource allocation in wireless mesh networks. These networks require a solution to fair and optimal resource allocation that is decentralised and self-con guring, as users in such networks do not submit to a central authority. The solution presented is comprised of two sections. The rst section nds the optimal rate allocation, by making use of a heuristic. The heuristic was developed by means of a non-linear mixed integer mathematical formulation. This heuristic nds a feasible rate region that conforms to the set of constraints set forth by the wireless communication channel. The second section nds a fair allocation of rates among all the users in the network. This section is based on a game theory framework, used for modelling the interaction observed between the users. The fairness model is de ned in strategic form as a repeated game with an in nite horizon. The rate adaptation heuristic and fairness model employs a novel and e ective information distribution technique. The technique makes use of the optimized link state routing protocol for information distribution, which reduces the overhead induced by utilising multi-point relays. In addition, a novel technique for enforcing cooperation between users in a network is presented. This technique is based on the Folk theorem and ensures cooperation by threat of punishment. The punishment, in turn, is executed in the form of banishment from the network. The study describes the performance of the rate adaptation heuristic and fairness model when subject to xed and randomised topologies. The xed topologies were designed to control the amount of interference that a user would experience. Although these xed topologies might not seem to re ect a real-world scenario, they provide a reasonable framework for comparison. The randomised network topology is introduced to more accurately represent a real-world scenario. Furthermore, the randomised network topologies consist of a signi cant number of users, illustrating the scalability of the solution. Both data and voice tra c have been applied to the rate adaptation heuristic and fairness model. It is shown that the heuristic e ectively reduces the packet loss ratio which drops below 5% after about 15 seconds for all xed topologies. Furthermore, it is shown that the solution is near-optimal in terms of data rate and that a fair allocation of data rates among all nodes is achieved. When considering voice tra c, an increase of 10% in terms of data rate is observed compared to data tra c. The heuristic is successfully applied to large networks, demonstrating the scalability of the implementation. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / unrestricted

Wireless mesh networks (WMN) is a new promising wireless technology which uses already available hardware and software components. This thesis proposes a routing algorithm for military applications. More specifically, a specialized scenario consisting of a network of flying Unmanned Aerial Vehicles (UAVs) executing reconnaissance missions is investigated. The proposed routing algorithm is hybrid in nature and uses both reactive and proactive routing characteristics to transmit information. Through simulations run on a specially built stand alone simulator, based on Java, packet overhead, delivery ratio and latency metrics were monitored with respect to varying number of nodes, node density and mobility. The results showed that the high overhead leads to high delivery ratio while latency tends to increase as the network grows larger. All the metrics revealed sensitivity in high mobility conditions.

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A tecnologia de comunicação em redes sem fio em malha, com base no padrão IEEE 802.11, tem sido uma solução tecnológica relevante no cenário atual das redes sem fio. Entretanto, com a eliminação dos cabos para comunicação de dados, as redes sem fio em malha dependem de fonte de energia para energizar os pontos de acesso da rede, que nem sempre está disponível na forma cabeada no local da instalação. Neste cenário, sendo o Brasil um país situado em uma zona tropical com alta incidência anual de radiação solar, a possibilidade da utilização da conversão da energia solar em elétrica é uma alternativa para eliminar a dependência de fonte de energia cabeada dos pontos de acesso da rede sem fio em malha. Este trabalho apresenta considerações sobre o desenvolvimento de sistemas autônomos de comunicação sem fio em malha, alimentados por energia solar fotovoltaica, compactos e de fácil instalação em área urbana e rural. Apresenta também, informações sobre o protótipo implementado denominado SAM Solar e respectiva avaliação quanto a autonomia, área de cobertura, número de usuários, altura mínima de instalação e taxa de transferência. / The wireless mesh network communication technology, based on the IEEE802.11 standard, has been a relevant technology solution for wireless networking in the recent years. However, even with the elimination of cables for data communication, the wireless mesh networks have to be connected to a voltage source using an electrical cable that may not be available at the local installation. In this scenario, being Brazil a country located in a tropical zone that receives large annual solar irradiation, the conversion of photons to electricity an be an alternative to eliminate the needs of wiring to the mesh access points. This work contributes to the development of autonomous wireless mesh communication systems powered by solar energy, with easy installation in urban or rural areas. This work also describes its evaluations in aspects such as autonomy, wireless coverage, number of users supported, installation height and throughput.

A tecnologia de comunicação em redes sem fio em malha, com base no padrão IEEE 802.11, tem sido uma solução tecnológica relevante no cenário atual das redes sem fio. Entretanto, com a eliminação dos cabos para comunicação de dados, as redes sem fio em malha dependem de fonte de energia para energizar os pontos de acesso da rede, que nem sempre está disponível na forma cabeada no local da instalação. Neste cenário, sendo o Brasil um país situado em uma zona tropical com alta incidência anual de radiação solar, a possibilidade da utilização da conversão da energia solar em elétrica é uma alternativa para eliminar a dependência de fonte de energia cabeada dos pontos de acesso da rede sem fio em malha. Este trabalho apresenta considerações sobre o desenvolvimento de sistemas autônomos de comunicação sem fio em malha, alimentados por energia solar fotovoltaica, compactos e de fácil instalação em área urbana e rural. Apresenta também, informações sobre o protótipo implementado denominado SAM Solar e respectiva avaliação quanto a autonomia, área de cobertura, número de usuários, altura mínima de instalação e taxa de transferência. / The wireless mesh network communication technology, based on the IEEE802.11 standard, has been a relevant technology solution for wireless networking in the recent years. However, even with the elimination of cables for data communication, the wireless mesh networks have to be connected to a voltage source using an electrical cable that may not be available at the local installation. In this scenario, being Brazil a country located in a tropical zone that receives large annual solar irradiation, the conversion of photons to electricity an be an alternative to eliminate the needs of wiring to the mesh access points. This work contributes to the development of autonomous wireless mesh communication systems powered by solar energy, with easy installation in urban or rural areas. This work also describes its evaluations in aspects such as autonomy, wireless coverage, number of users supported, installation height and throughput.

Les réseaux sans fil maillés offrent une infrastructure pour interconnecter les stations d’accès de réseaux de différentes technologies. Ils disposent d’une topologie maillée où tous les routeurs sont connectés de proche en proche sans hiérarchie centrale. Le routage des données, dans ce type de réseaux, doit être réalisé tout en optimisant les ressources du réseau et en respectant au mieux les exigences de QoS des utilisateurs. Dans cette thèse, nous proposons un routage orienté qualité de service dans un réseau sans fil métropolitain grâce à une approche de type cross-layer. Nous avons commencé par étudier l’impact des couches PHY et MAC sur le routage afin d’en déduire la meilleure combinaison protocolaire pour un réseau sans fil maillé. Nous avons, par la suite, orienté notre travail sur l’étude du comportement du protocole de routage OLSR sous différentes métriques de routage. Les résultats de cette étude ont confirmé les limites des métriques existantes à reproduire la qualité réelle des liens et ont soulevé plusieurs points d’optimisation sur lesquels nous avons focalisé. Nous avons donc proposé de nouvelles métriques qui renseignent sur la qualité des liens, en se basant sur les caractéristiques PHY et MAC des liens réseaux, notamment la disponibilité du lien, le taux de perte, la bande passante résiduelle, etc. L’acquisition de ces paramètres des couches basses se fait à l’aide d’un mécanisme de cross-layer. Ces métriques permettent d’appréhender les interférences inter-flux et d’éviter de créer des goulots d’étranglement en équilibrant les charges sur les différents liens. En se basant sur le modèle de graphe de conflit et le calcul des cliques maximales, nous avons proposé une méthode d’estimation de la bande passante résiduelle qui permet de considérer, en plus, les interférences intra-flux. Finalement, nous avons proposé un protocole de routage qui supporte cette métrique et nous avons étudié ses performances par simulation en comparaison avec d’autres métriques et protocoles de routage existants. Les résultats obtenus ont révélé l’aptitude de notre protocole à supporter le passage à l’échelle du réseau ainsi que sa capacité à choisir les routes offrant le plus de débit et le moins de délai, permettant ainsi, une meilleure livraison du trafic de données. / Wireless Mesh Networks provide infrastructure to interconnect access stations in networks of different technologies. They have a mesh topology where all the routers are connected with no central hierarchy. Routing in WMNs must be carried out while optimizing network resources and respecting the best user QoS requirements. In this thesis, we propose a QoS-oriented routing in a metropolitan wireless network using a cross-layer approach. We first studied the impact of the PHY and MAC layers on routing to deduce the best combination protocol for a wireless mesh network. We have subsequently focused our work on studying the behavior of the OLSR routing protocol with different routing metrics. The results of this study confirmed the limits of existing metrics to reproduce the real link quality and raised a number of optimization points on which we focused. We have, therefore, proposed new metrics that provide information about link quality, based on PHY and MAC characteristics, including the link availability, the loss rate, the available bandwidth, etc. These low layers parameters are acquired using a cross-layer mechanism. These metrics allow to apprehend inter-flow interferences and avoid bottleneck formation by balancing traffic load on the links. Based on the conflict graph model and calculation of maximal cliques, we proposed a method to estimate the available bandwidth of a path which considers, in addition, intra-flow interferences. Finally, we proposed a routing protocol that supports this metric and we studied by simulation its performances compared to different existing routing metrics and protocols. The results revealed the ability of our protocol to support the network scalability as well as its ability to choose routes with high throughput and limited delay, thus, better delivery of data traffic.