Results 11  20
of
203
Algorithmic Aspects of Topology Control Problems for Ad hoc Networks
, 2002
"... 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 th ..."
Abstract

Cited by 120 (6 self)
 Add to MetaCart
(Show Context)
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 NPcomplete 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 2nodeconnected graph is obtained. It is shown that this algorithm provides a constant performance guarantee. Experimental results from an implementation of the approximation algorithm are also presented.
Boundary Recognition in Sensor Networks by Topological Me ods
 in Proc. of MOBICOM
, 2006
"... Wireless sensor networks are tightly associated with the underlying environment in which the sensors are deployed. The global topology of the network is of great importance to both sensor network applications and the implementation of networking functionalities. In this paper we study the problem ..."
Abstract

Cited by 105 (17 self)
 Add to MetaCart
(Show Context)
Wireless sensor networks are tightly associated with the underlying environment in which the sensors are deployed. The global topology of the network is of great importance to both sensor network applications and the implementation of networking functionalities. In this paper we study the problem of topology discovery, in particular, identifying boundaries in a sensor network. Suppose a large number of sensor nodes are scattered in a geometric region, with nearby nodes communicating with each other directly. Our goal is to find the boundary nodes by using only connectivity information. We do not assume any knowledge of the node locations or interdistances, nor do we enforce that the communication graph follows the unit disk graph model. We propose a simple, distributed algorithm that correctly detects nodes on the boundaries and connects them into meaningful boundary cycles. We obtain as a byproduct the medial axis of the sensor field, which has applications in creating virtual coordinates for routing. We show by extensive simulation that the algorithm gives good results even for networks with low density. We also prove rigorously the correctness of the algorithm for continuous geometric domains.
Evaluating Mobility Models Within An Ad Hoc Network
, 2000
"... 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 computing services. However, wireless networks require the existence of a wired base station (BS) in ord ..."
Abstract

Cited by 96 (1 self)
 Add to MetaCart
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 computing services. However, wireless networks require the existence of a wired base station (BS) in order for the wireless user to send/receive messages. Ad hoc networks, a subset of wireless networks, allow the formation of a wireless network without the need for a BS. All participating users in an ad hoc network agree to accept and forward messages, to and from each other. With this flexibility, wireless networks have the ability to form anywhere, at any time, as long as two or more wireless users are willing to communicate. In an ad hoc network, the ability to send a message to a group of users, based solely on their geographic location, is desirable. A geocast protocol serves this purpose. Rescue missions, military scenarios, and even advertising schemes benefit from this type of message delivery service. However, before implementation occurs, an ad hoc network protocol such as a geocast protocol must be tested under realistic conditions including, but not limited to, a sensible transmission range, limited buffer for storage of messages, and realistic movements of the wireless users (i.e., a mobility model). The results presented in this thesis focus on several mobility models in an attempt to compare iv the effects that different mobility models have on an ad hoc network protocol. It is obvious that wireless users will travel from one location to another. However, representing their exact movements is not so simple. The results presented in this thesis illustrate the importance in carefully evaluating and implementing multiple mobility models when evaluating an ad hoc net...
Crossing Over the Bounded Domain: From Exponential to Powerlaw Intermeeting Time in MANET
, 2007
"... Intermeeting time between mobile nodes is one of the key metrics in a Mobile Adhoc Network (MANET) and central to the endtoend delay and forwarding algorithms. It is typically assumed to be exponentially distributed in many performance studies of MANET or numerically shown to be exponentially di ..."
Abstract

Cited by 77 (5 self)
 Add to MetaCart
(Show Context)
Intermeeting time between mobile nodes is one of the key metrics in a Mobile Adhoc Network (MANET) and central to the endtoend delay and forwarding algorithms. It is typically assumed to be exponentially distributed in many performance studies of MANET or numerically shown to be exponentially distributed under most existing mobility models in the literature. However, recent empirical results show otherwise: the intermeeting time distribution in fact follows a powerlaw. This outright discrepancy potentially undermines our understanding of the performance tradeoffs in MANET obtained under the exponential distribution of the intermeeting time, and thus calls for further study on the powerlaw intermeeting time including its fundamental cause, mobility modeling, and its effect. In this paper, we rigorously prove that a finite domain, on which most of the current mobility models are defined, plays an important role in creating the exponential tail of the intermeeting time. We also prove that by simply removing the boundary in a simple twodimensional isotropic random walk model, we are able to obtain the empirically observed powerlaw decay of the intermeeting time. We then discuss the relationship between the size of the boundary and the relevant timescale of the network scenario under consideration. Our results thus provide guidelines on the design of new mobility models with powerlaw intermeeting time distribution, new protocols including packet forwarding algorithms, as well as their performance analysis.
Mobility Models for Ad hoc Network Simulation
, 2004
"... In this paper, we propose a novel general technique, based on renewal theory, for analyzing mobility models in ad hoc networks. Our technique enables an accurate derivation of the steady state distribution functions for node movement parameters such as distance and speed. We first apply our techniqu ..."
Abstract

Cited by 70 (1 self)
 Add to MetaCart
In this paper, we propose a novel general technique, based on renewal theory, for analyzing mobility models in ad hoc networks. Our technique enables an accurate derivation of the steady state distribution functions for node movement parameters such as distance and speed. We first apply our technique to the random waypoint model and provide alternative proofs for previous claims about the discrepancy between the steady state average speed and the average speed associated with the simulated distribution [1]. Our main contribution is a new methodology for simulating mobility which guarantees steady state for node movement distributions from the start of the simulation. Our methodology enables the correct and efficient simulation of a desired steady state distribution, and can be implemented in a manner transparent to the user. We support our claims through both formal proofs as well as extensive simulations.
Perkins “Scalability Study of the Ad Hoc OnDemand Distance Vector Routing Protocol
 In ACM/Wiley International Journal of Network Management
, 2003
"... Abstract — As mobile networking continues to experience increasing popularity, the need to connect large numbers of wireless devices will become more prevalent. Many recent proposals for ad hoc routing have certain characteristics which may limit their scalability to large networks. This paper exa ..."
Abstract

Cited by 61 (1 self)
 Add to MetaCart
(Show Context)
Abstract — As mobile networking continues to experience increasing popularity, the need to connect large numbers of wireless devices will become more prevalent. Many recent proposals for ad hoc routing have certain characteristics which may limit their scalability to large networks. This paper examines five different combinations of modifications which may be incorporated into virtually any ondemand protocol in order to improve its scalability. The scalability of current ondemand routing protocols is evaluated through the selection of a representative from this class of protocols. The performance of the unmodified ondemand protocol is compared against that of it combined with each of the scalability modifications. Each scheme’s behavior is analyzed in networks as large as 10,000 nodes through detailed simulation. Based on the observations, conclusions are drawn as to the expected scalability improvement which can be achieved by each modification. I.
Group and swarm mobility models for ad hoc network scenarios using virtual tracks
 In Proceedings of MILCOM
, 2004
"... The mobility model is one of the most important factors in the performance evaluation of a mobile ad hoc network (MANET). Traditionally, the random waypoint mobility model has been used to model the node mobility, where the movement of one node is modeled as independent from all others. However, in ..."
Abstract

Cited by 57 (10 self)
 Add to MetaCart
(Show Context)
The mobility model is one of the most important factors in the performance evaluation of a mobile ad hoc network (MANET). Traditionally, the random waypoint mobility model has been used to model the node mobility, where the movement of one node is modeled as independent from all others. However, in reality, especially in large scale military scenarios, mobility coherence among nodes is quite common. One typical mobility behavior is group mobility. Thus, to investigate military MANET scenarios, an underlying realistic mobility model is highly desired. In this paper, we propose a “virtual track ” based group mobility model (VT model) which closely approximates the mobility patterns in military MANET scenarios. It models various types of node mobility such as group moving nodes, individually moving nodes as well as static nodes. Moreover, the VT model not only models the group mobility, it also models the dynamics of group mobility such as group merge and split. Simulation experiments show that the choice of mobility model has significant impact on network performance. I.
An epidemic model for information diffusion in manets
 In Proceedings of the 5th ACM international workshop on
, 2002
"... ..."
(Show Context)
Building realistic mobility models from coarsegrained traces
 in Proc. MobiSys
, 2006
"... In this paper we present a tracedriven framework capable of building realistic mobility models for the simulation studies of mobile systems. With the goal of realism, this framework combines coarsegrained wireless traces, i.e., association data between WiFi users and access points, with an actual ..."
Abstract

Cited by 51 (5 self)
 Add to MetaCart
(Show Context)
In this paper we present a tracedriven framework capable of building realistic mobility models for the simulation studies of mobile systems. With the goal of realism, this framework combines coarsegrained wireless traces, i.e., association data between WiFi users and access points, with an actual map of the space over which the traces were collected. Through a sequence of data processing steps, including filtering the data trace and converting the map to a graph representation, this framework generates a probabilistic mobility model that produces user movement patterns that are representative of real movement. This is done by adopting a set of heuristics that help us infer the paths users take between access points. We describe our experience applying this approach to a college campus, and study a number of properties of the trace data using our framework.
The critical transmitting range for connectivity in mobile ad hoc networks
 IEEE Transactions on Mobile Computing
, 2005
"... this paper, we study the critical transmitting range (CTR) for connectivity in mobile ad hoc networks. We prove that ln n rM c n for some constant c 1, where rM is the CTR in the presence of Mlike node mobility and n is the number of network nodes. Our result holds for an arbitrary mobility model ..."
Abstract

Cited by 48 (3 self)
 Add to MetaCart
(Show Context)
this paper, we study the critical transmitting range (CTR) for connectivity in mobile ad hoc networks. We prove that ln n rM c n for some constant c 1, where rM is the CTR in the presence of Mlike node mobility and n is the number of network nodes. Our result holds for an arbitrary mobility model M such that: 1) M is obstacle free and 2) nodes are allowed to move only within a certain bounded area. We also investigate in detail the case of random waypoint mobility, which is the most common mobility model used in the simulation of ad hoc networks. Denoting with rw p the CTR with random waypoint mobility when the pause time is set to p and node velocity is set to v, we prove that rw qffiffiffiffiffi pþ0:521405 v ln n p p n if p>0 and that rw qffiffiffiffiffi ln n 0 n. The results of our simulations also suggest that if n is large enough (n 50), rw r 0 is well approximated by 4 ln n, where r is the critical range in case of uniformly distributed nodes. The results presented in this paper provide a better understanding of the behavior of a fundamental network parameter in the presence of mobility and can be used to improve the accuracy of mobile ad hoc network simulations. Index Terms—Critical transmitting range, connectivity, random waypoint model, mobility modeling, ad hoc networks. æ 1