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
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/10488 |
| Date | 07 January 2019 |
| Creators | Sajjadi Torshizi, Seyed Dawood |
| Contributors | Pan, Jianping |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | Available to the World Wide Web |
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