Abstract not found

bahl~microsoft, corn ymwang~microsoft, corn rogerwa~microsoft, corn The topology of a wireless multi-hop network can be con-trolled by varying the transmission power at each node. In this paper, we give a detailed analysis of a cone-based dis-tributed topology control algorithm. This algorithm, intro-duced in [16], does not assume that nodes have GPS in-formation available; rather it depends only on directional information. Roughly speaking, the basic idea of the algo-rithm is that a node u transmits with the minimum power P~,,a required to ensure that in every cone of degree a around u, there is some node that u can reach with power Pma- We show that taking a = 57r/6 is a necessary and sufficient con-dition to guarantee that network connectivity is preserved. More precisely, if there is a path from a to t when every node communicates at maximum power then, if a < _ 5~r/6, there is still a path in the smallest symmetric graph Ga con-taining all edges (u, v) such that u can communicate with v using power p~,a. On the other hand, if ~> 51r/6, connec-tivity is not necessarily preserved. We also propose a set of optimizations that further reduce power consumption and prove that they retain network connectivity. Dynamic re-configuration in the presence of failures and mobility is also discussed. Simulation results are presented to demonstrate the effectiveness of the algorithm and the optimizations. 1.

this article, we review some of the characteristic features of ad hoc networks, formulate problems and survey research work done in the area. We focus on two basic problem domains: topology control, the problem of computing and maintaining a connected topology among the network nodes, and routing. This article is not intended to be a comprehensive survey on ad hoc networking. The choice of the problems discussed in this article are somewhat biased by the research interests of the author

In this paper we study a model for ad-hoc networks close enough to reality as to represent existing networks, being at the same time concise enough to promote strong theoretical results. The Quasi Unit Disk Graph model contains all edges shorter than a parameter d between 0 and 1 and no edges longer than 1. We show that -- in comparison to the cost known on Unit Disk Graphs -- the complexity results in this model contain the additional factor 1/d&sup2;. We prove that in Quasi Unit Disk Graphs flooding is an asymptotically message-optimal routing technique, provide a geometric routing algorithm being more efficient above all in dense networks, and show that classic geometric routing is possible with the same performance guarantees as for Unit Disk Graphs if d 1/ # 2.

The efficiency of a communication network depends not only on its control protocols, but also on its topology. We propose a distributed topology management algorithm that constructs and maintains a backbone topology based on a minimal dominating set (MDS) of the network. According to this algorithm, each node determines the membership in the MDS for itself and its one-hop neighbors based on two-hop neighbor information that is disseminated among neighboring nodes. The algorithm then ensures that the members of the MDS are connected into a connected dominating set (CDS), which can be used to form the backbone infrastructure of the communication network for such purposes as routing. The correctness of the algorithm is proven, and the efficiency is compared with other topology management heuristics using simulations. Our algorithm shows better behavior and higher stability in ad hoc networks than prior algorithms.

We present two protocols for ad hoc wireless networks, one for the media access control problem, and the other for the power control problem. For the media access control problem we...

In mobile ad hoc networks, it is often more important to optimize for energy efficiency than throughput. In this paper, we investigate the effect of transmit range on energy efficiency of packet transmissions. We determine a common range for all nodes such that the average energy expenditure per received packet is minimized. In the first part of this paper, we consider stationary networks. We show that energy efficiency depends on various system parameters that includes path loss exponent of the channel, energy dissipation model and network offered load. In particular, when the path loss exponent is large, energy efficiency decreases when the transmit range increases. Hence, the network should be operated at the critical range that just maintains network connectivity. However, when the path loss exponent is small, operating at the critical range yields inferior throughput and energy efficiency. Our results show that energy efficiency is intimately connected to network connectivity. Three network connectivity regimes are identified as the transmit range of all nodes increases. In the second part, we examine the effect of node mobility on energy efficiency. We show that at normal offered load, an optimal transmit range exists such that energy efficiency is maximized. The optimal range turns out to be insensitive to node mobility, and is much larger than the critical range. We show that the energy expenditure can be reduced by 15% to 73% in different mobility scenarios, if the network is operated at the optimal range.

We describe the design and implementation of a power-saving protocol for ad hoc wireless networks. We present the Span power-saving protocol and discuss its implementation in the context of the Linux operating system. We address the issues of ad hoc routing, link layer design, and integration with the Linux networking stack using the 802.11b wireless link technology. From this thesis, we conclude that Span can be implemented on an 802.11b network with reasonable performance for most networking applications. Furthermore, our implementation of Span yields a lifetime improvement of between 12% and 29% at each node in an ad hoc network. We argue that with additional hardware, Span can outperform conventional 802.11 ad hoc networks in terms of capacity, latency, and power savings.

A mobile ad hoc network (MANET) is one consisting of a set of mobile hosts which can operate independently without infrastructure base stations. Power saving is a critical issue for MANET since most mobile hosts will be operated by battery powers. In this paper, we address the power-saving issue for IEEE 802.11-based MANETs from several protocol layers, including physical, MAC, and network layers. Our solution is fully power-aware and locationaware in the sense that it exploits location information of mobile hosts to achieve energy conservation on all these protocol layers. In comparison, existing protocols only exploit location information in limited layers (e.g., power control is covered in [9, 18, 27], power mode management in [3, 15, 30], power-aware MAC in [2, 19, 29], and poweraware routing in [5, 20, 23]). Similar to cellular networks, our approach is based on partitioning the network area into squares/hexagons, thus leading to a powerful energy and mobility management capability.

A new protocol is presented for power control in ad hoc networks. The issues in conceptualizing the power control problem are discussed, and an architecturally simple as well as theoretically well founded solution is provided. The solution is shown to simultaneously satisfy the objectives of maximizing the traffic carrying capacity of the entire network, extending battery life through providing low power routes, and reducing the contention at the MAC (media access control) layer. Further, the protocol has the plug-and-play feature that it can be employed in conjunction with any routing protocol that pro-actively maintains a routing table. The protocol called COMPOW (Common Power), is completely distributed, asynchronous and modular, and can dynamically adapt to mobility. The protocol has been implemented in the Linux kernel. The software architecture and implementation are described in detail.