Research On Network Calculus Based QoS Performance For Wireless Mesh Networks

Wireless Mesh Networks (WMNs) is a high capacity and transmission rates distributed network organized in a mesh topology. The difference from conventional wireless networks are WMNs combine WLAN and Ad Hoc networks and possess the advantages of both with reliability, self-organizing and self-healing characteristics. Along with the increasing demand of network communications, more and more reliable WMNs are required. WMNs Quality of Service (QoS) enhancement research, therefore, is important. However, the characteristics of multi-hop routing and bandwidth fairness bring many challenging problems in QoS research. In order to enhance the quality of networks, the research on how to efficiently implement QoS control for WMNs and how to prevent network congestion collapse, has profound impacts.In this dissertation, we focus on the QoS performance concerns in WMNs, and carry out our in-depth study the characteristics of traffic in WMNs. Aimming at the WMNs characteristics of instability wireless link, high probability wrong code channel and statistical traffic, this thesis employs Network Calculus theory to elaborate a WMNs QoS performance evaluation model. The research contributes to the development of the body of knowledge surrounding WMNs QoS. Its contributions include the following:A new proposed WMNs traffic model WgSBB based on stochastic/statistical network calculus.Having reviewed the literature on network traffic modeling, a new traffic model WgSBB is proposed for WMNs based on stochastic/statistical network calculus. It adopts backlog bound as descriptive statistics to represent a single and multiple node(s) traffic model for WMNs. The busty function of the model is constrained under a min-plus algebra, which indicates the model has a rigorous boundary function, then it illustrates the possession of summation and in/outbound traffic characteristics, and the relationship of inbound and outbound traffic. It has been theoretically proved that the model is able to properly depict WMNs traffic characteristics.A new proposed greedy fractal leaky bucket shaper GFLB and its performance parameters for WMNs gateway traffic based on stochastic/statistical network calculus.In this thesis, a mathematical model of the greedy fractal leaky bucket shaper(GFLB) is proposed for WMNs to optimize or guarantee performance, and a number of corollaries of the greedy fractal leaky bucket shaper are derived, such as input/output, queue length and latency characteristics. Also, a thorough arid sound discussion of the impact of integrating the greedy fractal leaky bucket shaper into network edges on communication latency and the total packets losing is conducted, and it concludes that the migrated greedy fractal leaky bucket shaper has no negative impact on the WMNs. The discussion significantly contributes to other researchers on how to evaluate the greedy fractal leaky bucket shaper traffic control solution and how to effectively adjust and control Mesh gateway traffic.A new proposed QoS performance stochastic/statistical upper bound model for GFLB WMNs gateway nodes.In WMNs, Mesh gateways are the performance drawback. Upper bound on cache backlog bound, delay and jitter of Mesh gateway node, therefore, play important roles in WMNs planning, designing and deploying. According to the art of the state in WMNs, in this thesis, greedy fractal leaky bucket shaper and strategy for bandwidth distribute fairly are applied at the network edges to analyze the QoS performance statistics upper bound model to assess the upper bound of cache backlog bound, delay and jitter. The experimental data indicates that applied greedy fractal leaky bucket shaper in WMNs gateways can fairly allocate network bandwidth to all network sessions without interfering. With the proposed model, the WMNs traffic QoS performance upper bound can be guaranteed, and it is simple and applicable.A new proposed end-to-end QoS stochastic/statistical upper bound model for WMNs gateways and Mesh routers.The end-to-end QoS performances between Mesh routers and Mesh gateways are determined in the mean of whether upper bound can be guaranteed. It can directly affect the network control algorithms of network congestion collapse. Therefore, in this thesis, the employment of network calculus to calculate the Mesh routers end-to-end QoS performances upper bound can conclude the stochastic/statistical upper bounds of WMNs single node backlog bound, delay, idealized delay, approximate delay and jitter. The conclusion proves WMNs traffic delay statistics upper bound on service curve has better compactness. The experimental data indicates that the effective service curve and statistics (stochastic) network calculus are suitable for WMNs, and it contributes the development of WMNs traffic control, plan and manage for stochastic/statistical services.