Topology Control Problem Research Articles

Dynamic Topology Control and Routing in Wireless Ad Hoc Networks

In this letter we consider topology control and routing problem in wireless networks where equipped with point-to-point wireless links such as directional antennas or free space optics. In point-to-point wireless networks, each node has a limited number of transceivers and hence can communicate with only a limited number of nodes within its transmission range. The selection of the limited number of neighbors is very critical for the network performance. In this letter, we propose a topology control algorithms which consider the topology control and routing of each demand is considered simultaneously. For this, we introduce the degree constraint shortest path problem for finding optimal (shortest) paths in wireless point-to-point networks. Also, we propose two topology control algorithms: minimum hop (MHA) and resource availability ratio (RAR) algorithm. The resource availability ratio algorithm considers not only the available link bandwidth but also the available interfaces between neighbors. By simulation experiments, we compare the performance of each algorithm.

Equilibria in Topology Control Games for Ad Hoc Networks

We study topology control problems in ad hoc networks where network nodes get to choose their power levels in order to ensure desired connectivity properties. Unlike most other work on this topic, we assume that the network nodes are owned by different entities, whose only goal is to maximize their own utility that they get out of the network without considering the overall performance of the network. Game theory is the appropriate tool to study such selfish nodes: we define several topology control games in which the nodes need to choose power levels in order to connect to other nodes in the network to reach their communication partners while at the same time minimizing their costs. We study Nash equilibria and show that-among the games we define-these can only be guaranteed to exist if each network node is required to be connected to all other nodes (we call this the STRONG CONNECTIVITY GAME). For a variation called CONNECTIVITY GAME, where each node is only required to be connected (possibly via intermediate nodes) to a given set of nodes, we show that Nash equilibria do not necessarily exist. We further study how to find Nash equilibria with incentive-compatible algorithms and compare the cost of Nash equilibria to the cost of a social optimum, which is a radius assignment that minimizes the total cost in a network where nodes cooperate. We also study variations of the games; one where nodes not only have to be connected, but k-connected, and one that we call the REACHABILITY GAME, where nodes have to reach as many other nodes as possible, while keeping costs low. We extend our study of the STRONG CONNECTIVITY GAME and the CONNECTIVITY GAME to wireless networks with directional antennas and wireline networks, where nodes need to choose neighbors to which they will pay a link. Our work is a first step towards game-theoretic analyses of topology control in wireless and wireline networks.

QoS Topology Control for Nonhomogenous Ad Hoc Wireless Networks

This paper discusses the energy-efficient QoS topology control problem for nonhomogenous ad hoc wireless networks. Given a set of nodes with different energy and bandwidth capacities in a plane, and given the end-to-end traffic demands and delay bounds between node-pairs, the problem is to find a network topology that can meet the QoS requirements and the maximum energy utilization of nodes is minimized. Achieving this objective is vital to the increase of network lifetime. We consider two cases of the problem: (1) the traffic demands are not splittable, and (2) the traffic demands are splittable. For the former case, the problem is formulated as an integer linear programming problem. For the latter case, the problem is formulated as a mixed integer programming problem, and an optimal algorithm has been proposed to solve the problem.

An SPT-based topology control algorithm for wireless ad hoc networks

In this paper, we present a localized Shortest-Path-Tree (SPT) based algorithm that copes with the topology control problem in wireless ad hoc networks. Each mobile node determines its own transmission power based only on its local information. The proposed algorithm first constructs local SPTs from the initial graph, after which the total power consumption is further reduced by allowing each mobile node to search the replaceable links individually. The constructed topology ensures network connectivity, and possesses the following desirable energy-efficient features: (i) the power stretch factor is bounded and can be predetermined, (ii) the power consumption is evenly distributed among the mobile nodes, and (iii) the total power consumption is lower than that obtained by the best known algorithms. The performance improvements of the proposed algorithm are demonstrated through extensive simulations. We conclude our work with a discussion of future research directions toward more integrated mobile network architectures.

MAC‐assisted topology control for ad hoc wireless networks

AbstractWe consider ad hoc wireless networks and the topology control problem defined as minimizing the amount of power needed to maintain connectivity. The issue boils down to selecting the optimum transmission power level at each node based on the position information of reachable nodes. Local decisions regarding the transmission power level induce a subgraph of the maximum powered graph Gmax in which edges represent direct reachability at maximum power. We propose a new algorithm for constructing minimum‐energy path‐preserving subgraphs of Gmax, i.e. ones minimizing the energy consumption between node pairs. Our algorithm involves a modification to the medium access control (MAC) layer. Its superiority over previous solutions, up to 60% improvement in sparse networks, demonstrates once again that strict protocol layering in wireless networks tends to be detrimental to performance. Copyright © 2005 John Wiley & Sons, Ltd.

Algorithmic Aspects of Topology Control Problems for Ad Hoc Networks

Topology control problems are concerned with the assignment of power values to the nodes of an ad hoc network so that the power assignment leads to a graph topology satisfying some specified properties. This paper considers such problems under several optimization objectives, including minimizing the maximum power and minimizing the total power. A general approach leading to a polynomial algorithm is presented for minimizing maximum power for a class of graph properties called monotone properties. The difficulty of generalizing the approach to properties that are not monotone is discussed. Problems involving the minimization of total power are known to be NP-complete even for simple graph properties. A general approach that leads to an approximation algorithm for minimizing the total power for some monotone properties is presented. Using this approach, a new approximation algorithm for the problem of minimizing the total power for obtaining a 2-node-connected graph is developed. It is shown that this algorithm provides a constant performance guarantee. Experimental results from an implementation of the approximation algorithm are also presented.