本論文對IEEE 802.16 協調分散式之網狀網路提出一允入控制之演算法。在此類網路中，控制子訊框交換各站台之排程訊息，並預留資料子訊框之時槽作為實際資料傳輸之用。我們利用令牌桶機制來控制網路訊流之流量特徵，如此可簡單的估計各訊流所需之頻寬。我們使用了所提出的頻寬估計方法，並一起考慮各訊流之跳接數與延遲時間之需求，提出的允入控制演算法能夠保證即時性串流之延遲時間需求，且可避免低等級訊流發生飢餓情形。模擬結果顯示，所提出的允入控制方法可以有效的把超過延遲時間需求之即時性訊流封包數目降低，並且低等級訊流在網路負載大時仍然可以存取頻道。 / We propose a routing metric (SWEB: Shortest-Widest Efficient Bandwidth) and an admission control (TAC: Token bucket-based Admission Control) algorithm under IEEE 802.16 coordinated, distributed mesh networks. In such network architectures, all scheduling messages are exchanged in the control subframes to reserve the timeslots in data subframes for the actual data transmissions. The token bucket mechanism is utilized to control the traffic pattern for easily estimating the bandwidth of a connection. We apply the bandwidth estimation and take the hop count and delay requirements into consideration. TAC is designed to guarantee the delay requirements of the real-time traffic flows, and avoid the starvation of the low priority ones. Simulation results show that TAC algorithm can effectively reduce the number of real-time packets that exceed the delay requirements and low priority flows still can access the channel when the network is heavily-loaded.

Due to its ability to deliver scalable and fault-tolerant solutions, applications based on the peer-to-peer (P2P) paradigm are used by millions of users on the internet. Recently, wireless mesh networks (WMNs) have attracted a lot of interest from both academia and industry, because of their potential to provide flexible and alternative broadband wireless internet connectivity. However, due to various reasons such as unstable wireless link characteristics and multi-hop forwarding operation, the performance of current P2P systems is rather low in WMNs. This dissertation studies the technological challenges involved while deploying P2P systems over WMNs. We study the benefits of location-awareness and resource replication to the P2P overlay while targeting efficient resource lookup in WMNs. We further propose a cross-layer information exchange between the P2P overlay and the WMN in order to reduce resource lookup delay by augmenting the overlay routing table with physical neighborhood and resource lookup history information. Aiming to achieve throughput maximization and fairness in P2P systems, we model the peer selection problem as a mathematical optimization problem by using a set of mixed integer linear equations. A study of the model reveals the relationship between peer selection, resource replication and channel assignment on the performance of P2P systems over WMNs. We extend the model by formulating the P2P download problem as chunk scheduling problem. As a novelty, we introduce constraints to model the capacity limitations of the network due to the given routing and channel assignment strategy. Based on the analysis of the model, we propose a new peer selection algorithm which incorporates network load information and multi-path routing capability. By conducting testbed experiments, we evaluate the achievable throughput in multi-channel multi-radio WMNs. We show that the adjacent channel interference (ACI) problem in multi-radio systems can be mitigated, making better use of the available spectrum. Important lessons learned are also outlined in order to design practical channel and channel bandwidth assignment algorithms in multi-channel multi-radio WMNs.

Drastic growth and chaotic deployment of Wireless Local Area Networks (WLANs) in dense urban areas are some of the common issues of many Internet Service Providers (ISPs) and Wi-Fi users. These issues result in a substantial reduction of the throughput and impede the balanced distribution of bandwidth among the users. Most of these networks are using unmanaged consumer-grade Access Points (APs) and there is no cooperation among them. Moreover, the conventional association mechanism that selects APs with the strongest Received Signal Strength Indicator (RSSI) aggravates this situation. In spite of all these challenges, there is a great opportunity to build cooperative overlay networks among the APs that are owned by different ISPs, companies or individuals in dense urban areas. In fact, ISPs can distribute the resources among their customers in a cooperative fashion using a shared overlay platform which is constructed on top of the existing infrastructures. This approach helps the ISPs with efficient utilization of their resources and promoting the Quality of their Services (QoS). For instance, cooperative association control among the APs of different ISPs enables them to alleviate the drastic impact of interference in populated areas and improves the network throughput. Indeed, all Wi-Fi customers can associate to the APs from different ISPs and it leads to the construction of a large unified WLAN that expands the network coverage, significantly. Moreover, it results in a notable reduction of deployment costs and enhancement of customer satisfaction. Hence, as one of the key contributions of this dissertation, a cooperative framework for fine-grained AP association in dense WLANs is presented. On top of this framework, a thorough formulation and a heuristic solution to solve the aforementioned problems are introduced. The key enabler of the proposed solution is Software Defined Networking (SDN) which not only gives us an exceptional level of granularity but also empowers us to utilize high-performance computing resources and more sophisticated algorithms. Also, over the past few years, some of the largest cellular operators restricted their unlimited data plans and proposed tiered charging plans enforced by either strict throttling or large overage fees. While cellular operators are trying to guarantee the QoS of their services in a cost-effective and profitable manner, WLANs and Wi-Fi Mesh Networks (WMNs) as viable complements can be used to form a multihop backhaul connection between the access and the core networks. Indeed, the utilization of WMNs provides an opportunity to achieve a high network capacity and wide coverage by the employment of inexpensive commercial off-the-shelf products. Moreover, by bridging the WMNs and cellular networks, and the fine-grained traffic engineering of network flows, it is possible to provide a cost-effective Internet access solution for people who cannot afford the high cost of data plans. However, there are certain requirements in terms of QoS for different services over multi-hop backhaul networks. In addition, the process of service provisioning in WMNs incorporates tightly correlated steps, including AP association, gateway selection, and backhaul routing. In most of the prior studies, these steps were investigated as independent NP-hard problems and no unified formulation that considers all these steps (at different tiers of WMNs) has been presented. Hence, as another contribution of this dissertation, a structured and thorough scheme to address the demands of end-users over SDN-aware WMNs is introduced. In contrast to most of the former work, this scheme takes the key characteristics of wireless networks into account, especially for Multi-Channel Multi-Radio WMNs. The proposed solution can be applied to the large-scale scenarios and finds a near-optimal solution in polynomial time. Furthermore, since the presented solution may split the packets of a single flow among multiple paths for routing and there are non-trivial drawbacks for its implementation, a randomized single-path flow routing for SDN-aware WMNs is introduced. The randomized nature of the introduced solution avoids the complexities of implementing a multi-path flow routing and it presents a viable routing scheme that guarantees certain performance bounds. The functionality and performance of all the presented solutions have been assessed through extensive numerical results and real testbed experimentations as a proof of concept. It is important to note that the solutions presented in this dissertation can be utilized to provide a large variety of services for Wi-Fi users, while they guarantee different QoS metrics. / Graduate

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<p>Wireless mesh networks are widely used for various communication purposes and are often deployed in a broad range of outdoor applications. In cases where the deployment area is outside the reach of fixed infrastructure, energy efficient operation of the mesh nodes is very important. Many approaches have been explored to find energy efficient network solutions for these types of scenarios. This thesisproposes power saving mechanisms where the mesh network nodes opportunistically access coexistent vehicular networks. This is referred to as Opportunistic Vehicle Assisted Ferrying (OVAF). The history of using moving particles for message carrying can be found in research on intermittently connected networks. However, this approachhas never been considered with fully connected networks. Two different models are presented to model the OVAFmechanism: \textbf{a}. \emph{A flow based model}, and \textbf{b}. \emph{Apacket based model}. For each model an analytic lower bound isobtained by formulating a linear integer optimization with differentcost functions. Heuristics, which simplify the complexity of theproblem, are then developed for eachmodel. Arriving vehicles and generated packets are also modeled asrandom processes under various scenarios using different parameters.Results are presented which demonstrate the superiority of the OVAFrouting method compared to conventional multihop forwarding (Up to $60\%$increase in energy saving).</p> / Master of Applied Science (MASc)

No / Wireless local area networks (WLANs) have risen in popularity for in-car networking systems that are designed to make driving safer. Wireless mesh networks (WMNs) are widely deployed to expand the coverage of high-speed WLANs and to support last-mile connectivity for mobile users anytime and anywhere at low cost. Many recent measurement studies have shown that the traffic arrival process in wireless networks exhibits the bursty and correlated nature. A new analytical model is developed in this paper as a cost-effective performance tool to investigate the quality-of-service (QoS) of the WMN that interconnects multiple WLANs in the presence of bursty and correlated traffic. After validating its accuracy via extensive simulation experiments, the analytical model is then used to investigate the performance of the hybrid wireless networks.

In this dissertation research, we design and analyze integrated mobility and service management for network cost minimization in Wireless Mesh Networks (WMNs). We first investigate the problem of mobility management in WMNs for which we propose two efficient per-user mobility management schemes based on pointer forwarding, and then a third one that integrates routing-based location update and pointer forwarding for further performance improvement. We further study integrated mobility and service management for which we propose protocols that support efficient mobile data access services with cache consistency management, and mobile multicast services. We also investigate reliable and secure integrated mobility and service man agement in WMNs, and apply the idea to the design of a protocol for secure and reliable mobile multicast. The most salient feature of our protocols is that they are optimal on a per-user basis (or on a per-group basis for mobile multicast), that is, the overall network communication cost incurred is minimized for each individual user (or group). Per-user based optimization is critical because mobile users normally have vastly different mobility and service characteristics. Thus, the overall cost saving due to per-user based optimization is cumulatively significant with an increasing mobile user population. To evaluate the performance of our proposed protocols, we develop mathematical models and computational procedures used to compute the network communication cost incurred and build simulation systems for validating the results obtained from analytical modeling. We identify optimal design settings under which the network cost is minimized for our mobility and service management protocols in WMNs. Intensive comparative performance studies are carried out to compare our protocols with existing work in the literature. The results show that our protocols significantly outperform existing protocols under identical environmental and operational settings. We extend the design notion of integrated mobility and service management for cost minimization to MANETs and propose a scalable dual-region mobility management scheme for location-based routing. The basic design concept is to use local regions to complement home regions and have mobile nodes in the home region of a mobile node serve as location servers for that node. We develop a mathematical model to derive the optimal home region size and local region size under which overall network cost incurred is minimized. Through a comparative performance study, we show that dual-region mobility management outperforms existing mobility management schemes based on static home regions. / Ph. D.

This thesis presents an exploratory study into the development of digital societies and it examines public sector modernization and innovation from a technology management perspective. The study presents reasons why most city-wide or council-wide development of wireless broadband access networks currently end in failure or are unsustainable. It also suggests its links with wider problems of innovation management and the commercial failure of otherwise technically competent solutions It explores the modernisation of society, government, the underlying theories that influence it as well as the innovations triggered by its wake. The exercise reveals a myriad of innovations; firstly in the modernisation of the infrastructure of government and secondly in the development of societal infrastructure in the form of broadband networks.