Cross-layer Design of Optimal Resource Allocation in Multihop Wireless Networks
Date Issued
2007
Date
2007
Author(s)
Wu, Kun-Da
DOI
en-US
Abstract
Multi-hop wireless networks are a promising solution for last mile access to the Internet due to their characteristics of easy deployment, low maintenance cost, and robust connectivity. In such a network, each node plays both roles of a host and a router, and packets are forwarded in a hop-by-hop manner without the assistance of a pre-deployed infrastructure. Each flow, in addition to contending for local resources at each intermediate node on its routing path, i.e., local interference, must compete for the shared wireless medium with those flows located within its interference range, i.e., location-dependent interference. These unique characteristics spawn many research challenges on providing end-to-end resource or bandwidth allocation in multi-hop wireless networks.
In this dissertation, we first define and formulate a new interference model, referred to as Node-based Interference Model, to better capture the behavior of medium access control protocols and physical layer interference issue. This model characterizes the relationship among the interference, data rate at the physical layer and the contentions at medium access layer and enables each node to locally identify the interference at the physical layer and contentions at the medium access layer through signal power measurement.
Next, we address the flow allocation problem in multihop wireless networks. Based on Node-based Interference Model, we formulate the problem as a cross-layer network utility maximization problem that considers the interaction of transport, MAC, and physical layers. The objective of this problem is to maximize the aggregate network throughput while maintaining the fairness among concurrent end-to-end sessions. We then propose a gradient-based flow allocation algorithm and analyze the convergence to the optimum for the proposed algorithm. The simulation results show that the proposed algorithm can rapidly converge to the optimum, and also rapidly adapt to the changes of the network topology and routing paths in different flow scenarios.
Then, we address the service differentiation with interference consideration for traffic of different priorities in multi-hop wireless networks. Specifically, we propose a cross-layer framework which supports different service levels in terms of throughput and queuing delays for concurrent sessions of different priorities. The system architecture is composed of two major components: a priority-based flow scheduler and an interference-aware bandwidth allocation unit. The priority-based flow scheduler differentiates the queueing delay for data packets being relayed to the next hop. As a result, the sessions of higher priority are guaranteed to have lower queueing delay at each intermediate node on the path to the receiver while the starvation of the lower priority session can be avoided. To utilize wireless resources optimally, we formulate the bandwidth allocation problem with interference consideration as a convex optimization problem. The problem can be solved by a sub-gradient algorithm in a distributed fashion. We then develop a distributed protocol for our proposed algorithm. The simulation results show that the proposed algorithm can achieve different levels of bandwidth allocation efficiently with a limited number of iterations. In addition, our algorithm scales well when the number of sessions and the size of the session increase. Moreover, together with the priority-based flow scheduler, the end-to-end throughput and delay can be effectively differentiated based on different levels of bandwidth allocation.
Subjects
無線網路
跨階層式設計
最佳化資源管理
Multihop wireless networks
Corss-layer design
Optimal resource allocation
Type
thesis
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