Power Stretch Factor Research Articles

Self-organizing fault-tolerant topology control in large-scale three-dimensional wireless networks

Topology control protocol aims to efficiently adjust the network topology of wireless networks in a self-adaptive fashion to improve the performance and scalability of networks. This is especially essential to large-scale multihop wireless networks (e.g., wireless sensor networks). Fault-tolerant topology control has been studied recently. In order to achieve both sparseness (i.e., the number of links is linear with the number of nodes) and fault tolerance (i.e., can survive certain level of node/link failures), different geometric topologies were proposed and used as the underlying network topologies for wireless networks. However, most of the existing topology control algorithms can only be applied to two-dimensional (2D) networks where all nodes are distributed in a 2D plane. In practice, wireless networks may be deployed in three-dimensional (3D) space, such as under water wireless sensor networks in ocean or mobile ad hoc networks among space shuttles in space. This article seeks to investigate self-organizing fault-tolerant topology control protocols for large-scale 3D wireless networks. Our new protocols not only guarantee k -connectivity of the network, but also ensure the bounded node degree and constant power stretch factor even under k −1 node failures. All of our proposed protocols are localized algorithms, which only use one-hop neighbor information and constant messages with small time complexity. Thus, it is easy to update the topology efficiently and self-adaptively for large-scale dynamic networks. Our simulation confirms our theoretical proofs for all proposed 3D topologies.

Distributed topology control algorithm based on one- and two-hop neighbors’ information for ad hoc networks

In this paper, we present a topology control algorithm for ad hoc networks. By considering the weight of the links, each node orders its one-hop neighbors in an ordered list and then the ordered lists are exchanged between the neighbors. This information enables the nodes to compute their transmission radius on the basis of its one- and two-hop neighbors’ information. We demonstrate that compared to the best known algorithms, the degree and transmission radius of the nodes in the topology produced by the proposed algorithm are smaller. In addition to Euclidean graphs, the algorithm works correctly on general weighted graphs. Also an extension of our algorithm is proposed which adapts its topology to network changes. Finally, we use the four metrics, node degree, transmission radius, the power stretch factor and, packet loss ratio to measure the performance improvements of the presented algorithms through simulations.

Energy-efficient topology control for three-dimensional sensor networks

Topology control in sensor networks has been heavily studied recently. Different geometric topologies were proposed to be the underlying network topologies to achieve the sparseness of the communication networks or to guarantee the package delivery of specific routing methods. However, most of the proposed topology control algorithms were only applied to Two-Dimensional (2D) networks where all sensor nodes are distributed in a 2D plane. In practice, the sensor networks are often deployed in 3D space, such as sensor nodes in a forest. This paper seeks to investigate efficient topology control protocols for 3D sensor networks. In our new protocols, we extend several 2D geometric topologies to 3D case, and propose some new 3D Yao-based topologies for sensor networks. We also prove several properties (e.g. bounded degree and constant power stretch factor) for them in 3D space. The simulation results confirm our theoretical proofs for these proposed 3D topologies.

The r-Neighborhood Graph: An Adjustable Structure for Topology Control in Wireless Ad Hoc Networks

In wireless ad hoc networks, constructing and maintaining a topology with lower node degrees is usually intended to mitigate excessive traffic load on wireless nodes. However, keeping lower node degrees often prevents nodes from choosing better routes that consume less energy. Therefore, the trade-off is between the node degree and the energy efficiency. In this paper, an adjustable structure, named the r-neighborhood graph, is proposed to control the topology. This structure has the flexibility to be adjusted between the two objectives through a parameter r, 0lesrles1. More explicitly, for any set of n nodes, the maximum node degree and power stretch factor can be bounded from above by some decreasing and increasing functions of r, respectively. Specifically, the bounds can be constants in some ranges of r. Even more, the r-neighborhood graph is a general structure of both RNG and GG, two well-known structures in topology control. Compared with YG <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> , another famous adjustable structure, our method always results in a connected planar with symmetric edges. To construct this structure, we investigate a localized algorithm, named PLA, which consumes less transmitting power during construction and executes efficiently in O(n logn) time

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.

Localized Algorithms for Energy Efficient Topology in Wireless Ad Hoc Networks

Topology control in wireless ad hoc networks is to select a subgraph of the communication graph (when all nodes use their maximum transmission range) with some properties for energy conservation. In this paper, we propose two novel localized topology control methods for homogeneous wireless ad hoc networks.Our first method constructs a structure with the following attractive properties: power efficient, bounded node degree, and planar. Its power stretch factor is at most ρ=1/1-(2sin π/k)β, and each node only has to maintain at most k + 5 neighbors where the integer k > 6 is an adjustable parameter, and β is a real constant between 2 and 5 depending on the wireless transmission environment. It can be constructed and maintained locally and dynamically. Moreover, by assuming that the node ID and its position can be represented in O(log n) bits each for a wireless network of n nodes, we show that the structure can be constructed using at most 24n messages, where each message is O(log n) bits.Our second method improves the degree bound to k, relaxes the theoretical power spanning ratio to ρ = √2β/1-(2√2sin π/k)β, where k > 8 is an adjustable parameter, and keeps all other properties. We show that the second structure can be constructed using at most 3n messages, where each message has size of O (log n) bits.We also experimentally evaluate the performance of these new energy efficient network topologies. The theoretical results are corroborated by the simulations: these structures are more efficient in practice, compared with other known structures used in wireless ad hoc networks and are easier to construct. In addition, the power assignment based on our new structures shows low energy cost and small interference at each wireless node.

Efficient Topology Control for Ad-Hoc Wireless Networks with Non-Uniform Transmission Ranges

Wireless network topology control has drawn considerable attention recently. Priori arts assumed that the wireless ad hoc networks are modeled by unit disk graphs (UDG), i.e., two mobile hosts can communicate as long as their Euclidean distance is no more than a threshold. However, practically, the networks are never so perfect as unit disk graphs: the transmission ranges may vary due to various reasons such as the device differences, the network control necessity, and the perturbation of the transmission ranges even the transmission ranges are set as the same originally. Thus, we assume that each mobile host has its own transmission range. The networks are modeled by mutual inclusion graphs (MG), where two nodes are connected iff they are within the transmission range of each other. Previously, no method is known for topology control when the networks are modeled as mutual inclusion graphs.The paper proposes the first distributed mechanism to build a sparse power efficient network topology for ad hoc wireless networks with non-uniform transmission ranges. We first extend the Yao structure to build a spanner with a constant length and power stretch factor for mutual inclusion graph. We then propose two efficient localized algorithms to construct connected sparse network topologies. The first structure, called extended Yao-Yao, has node degree at most O(log γ), where γ = maxu maxuv∈MG ru/rv. The second structure, called extended Yao and Sink, has node degree bounded by O(log γ), and is a length and power spanner. The methods are based on a novel partition strategy of the space surrounded each mobile host. Both algorithms have communication cost O(n) under a local broadcasting communication model, where each message has O(log n) bits.

DISTRIBUTED SPANNERS WITH BOUNDED DEGREE FOR WIRELESS AD HOC NETWORKS

In this paper, we review some new distributed algorithms that construct sparse subgraphs with bounded degree of the unit disk graph efficiently for wireless ad hoc networks. They maintain a linear number of links while still preserving power-efficient routes for any pair of nodes. It was open whether the Yao plus reverse Yao graph and the symmetric Yao graph are spanners. We show that the Yao plus reverse Yao graph has a bounded power stretch factor 2 in civilized unit disk graph. In addition, we review a recent example by M. Grünewald et al. [6] to show that the symmetric Yao graph does not have a constant bounded stretch factor. Finally, we conduct simulations to study the practical performances of these structures. All structures have small power stretch factors for randomly generated unit disk graphs in our experiments.