Browsing by Subject "topology design"

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Open Access
Joint topology design with routing and power control in ad hoc networks
(2003) Önal, Aydoğan
We discuss the problem of designing an ad hoc network topology by jointly using power control and routing. A well-designed topology in ad hoc networks provides several advantages: increasing the capacity, decreasing the complexity and reducing the power consumption. We formulate the topology design problem as an Integer Linear Programming (ILP) model. An optimal topology is designed subject to interference and connectivity constraints with three different objective functions and two power control approaches. Common transmit power (COMPOW) and the adaptive power (ADPOW) are the two different power control techniques used in this thesis. The objectives of the models that are used in the topology design are maximizing the number of established links, using shortest path routing strategy and minimizing the maximum traffic load over the most congested link by load balancing. Performance comparisons between two power control approaches with three different objectives in the topology design are achieved using numerical results on a sample network. Minimum end-to-end throughput, total throughput, total power consumption and the number of established links are used as the performance metrics. The numerical results show that selecting the optimal power for both power control approaches provides similar performance results. Therefore, simplicity of the COMPOW makes it more attractive than ADPOW in the topology design.
Open Access
Topology design and scheduling in STDMA based wireless ad hoc networks
(2003) Ergin, Sadettin Alp
With current advances in technology, wireless networks are increasing in popularity. Wireless networks allow users the freedom to travel from one location to another without interruption of their communication activities. Ad hoc networks, a subset of wireless networks, allow the formation of a wireless network without the need for a base station. Since no fixed infrastructure is involved in the communication, the nodes of ad hoc networks can communicate with each other or can relay data to other nodes. With this flexibility, wireless ad hoc networks have the ability to form a network anywhere, at any time, as long as two or more wireless users are willing to communicate. Managing ad hoc networks is a significantly more difficult task than managing wireline networks. The network requirements should be met by combined efforts of all the mobile nodes themselves. The nodes of ad hoc networks often operate under severe constraints, such as limited battery power, variable link quality and limited shared bandwidth. In this study, the topology design issue in ad hoc wireless networks is investigated. We employ hierarchical routing where the network topology is composed of clusters interconnected via a root node. Cluster-based topologies are suitable for military services, an important application area for ad hoc networks. The common power control technique (COMPOW) is used in this thesis where all nodes transmit at the same power level. Nodes employ the spatial TDMA (STDMA) scheme in order to access the channel. An important task is how to produce a minimum STDMA frame length, and this problem is known to be NP complete. We develop a heuristic algorithm for generating the minimum STDMA frame length. A new interference model for ad hoc networks is proposed which utilizes a hypergraph model. The relationship between the frame length, number of clusters and the transmit power level are investigated through numerical examples using a 15- node network.