Topology Control (TC) is one of the most important techniques used in wireless ad hoc and sensor networks to reduce energy consumption (which is essential to extend the network operational time) and radio interference (with a positive effect on the network traffic carrying capacity). The goal of this technique is to control the topology of the graph representing the communication links between network nodes with the purpose of maintaining some global graph property (e.g., connectivity), while reducing energy consumption and/or interference that are strictly related to the nodes' transmitting range. In this article, we state several problems related to topology control in wireless ad hoc and sensor networks, and we survey state-of-the-art solutions which have been proposed to tackle them. We also outline several directions for further research which we hope will motivate researchers to undertake additional studies in this field.

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Topology Control in Wireless Ad Hoc and Sensor Networks

The application of mathematical analysis to the study of wireless ad hoc networks has met with limited success due to the complexity of mobility and traffic models, the dynamic topology, and the unpredictability of link quality that characterize such networks. The ability to model individual, independent decision makers whose actions potentially affect all other decision makers renders game theory particularly attractive to analyze the performance of ad hoc networks. In this article we describe how various interactions in wireless ad hoc networks can be modeled as a game. This allows the analysis of existing protocols and resource management schemes, as well as the design of equilibrium-inducing mechanisms that provide incentives for individual users to behave in socially-constructive ways. We survey the recent literature on game theoretic analysis of ad hoc networks, highlighting its applicability to power control and waveform adaptation, medium access control, routing, and node participation, among others.

/pdf/using-game-theory-to-analyze-wireless-ad-hoc-networks-m43me4ctqz.pdf

Using game theory to analyze wireless ad hoc networks

Vehicular ad hoc networks (VANETs) have the potential to transform the way people travel through the creation of a safe interoperable wireless communications network that includes cars, buses, traffic signals, cell phones, and other devices. However, VANETs are vulnerable to security threats due to increasing reliance on communication, computing, and control technologies. The unique security and privacy challenges posed by VANETs include integrity (data trust), confidentiality, nonrepudiation, access control, real-time operational constraints/demands, availability, and privacy protection. The trustworthiness of VANETs could be improved by addressing holistically both data trust, which is defined as the assessment of whether or not and to what extent the reported traffic data are trustworthy, and node trust, which is defined as how trustworthy the nodes in VANETs are. In this paper, an attack-resistant trust management scheme (ART) is proposed for VANETs that is able to detect and cope with malicious attacks and also evaluate the trustworthiness of both data and mobile nodes in VANETs. Specially, data trust is evaluated based on the data sensed and collected from multiple vehicles; node trust is assessed in two dimensions, i.e., functional trust and recommendation trust, which indicate how likely a node can fulfill its functionality and how trustworthy the recommendations from a node for other nodes will be, respectively. The effectiveness and efficiency of the proposed ART scheme is validated through extensive experiments. The proposed trust management theme is applicable to a wide range of VANET applications to improve traffic safety, mobility, and environmental protection with enhanced trustworthiness.

ART: An Attack-Resistant Trust Management Scheme for Securing Vehicular Ad Hoc Networks

Delay tolerant networks (DTNs) may lack continuous network connectivity. Routing in DTNs is thus challenging since it must handle network partitioning, long delays, and dynamic topology in such networks. In recent years, social-based approaches, which attempt to exploit social behaviors of DTN nodes to make better routing decision, have drawn tremendous interests in DTN routing design. In this article, we summarize the social properties in DTNs, and provide a survey of recent social-based DTN routing approaches. To improve routing performance, these methods either take advantages of positive social characteristics such as community and friendship to assist packet forwarding or consider negative social characteristics such as selfishness. We conclude by discussing some open issues and challenges in social-based approaches regarding the design of DTN routing protocols.

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A Survey of Social-Based Routing in Delay Tolerant Networks: Positive and Negative Social Effects

Consider a set of $n>2$ identical mobile computational entities in the plane, called robots, operating in Look-Compute-Move cycles, without any means of direct communication. The Gathering Problem is the primitive task of all entities gathering in finite time at a point not fixed in advance, without any external control. The problem has been extensively studied in the literature under a variety of strong assumptions (e.g., synchronicity of the cycles, instantaneous movements, complete memory of the past, common coordinate system, etc.). In this paper we consider the setting without those assumptions, that is, when the entities are oblivious (i.e., they do not remember results and observations from previous cycles), disoriented (i.e., have no common coordinate system), and fully asynchronous (i.e., no assumptions exist on timing of cycles and activities within a cycle). The existing algorithmic contributions for such robots are limited to solutions for $n \leq 4$ or for restricted sets of initial configura...

/pdf/distributed-computing-by-mobile-robots-gathering-2au7jx1t48.pdf

Distributed Computing by Mobile Robots: Gathering

We introduce a game-theoretic setting for routing in a mobile ad hoc network that consists of greedy, selfish agents who accept payments for forwarding data for other agents if the payments cover their individual costs incurred by forwarding data. In this setting, we propose Ad hoc-VCG, a reactive routing protocol that achieves the design objectives of truthfulness (i.e., it is in the agents' best interest to reveal their true costs for forwarding data) and cost-efficiency (i.e., it guarantees that routing is done along the most cost-efficient path) in a game-theoretic sense by paying to the intermediate nodes a premium over their actual costs for forwarding data packets. We show that the total overpayment (i.e., the sum of all premiums paid) is relatively small by giving a theoretical upper bound and by providing experimental evidence. Our routing protocol implements a variation of the well-known mechanism by Vickrey, Clarke, and Groves in a mobile network setting. Finally, we analyze a very natural routing protocol that is an adaptation of the Packet Purse Model [8] with auctions in our setting and show that, unfortunately, it does not achieve cost-efficiency or truthfulness.

https://web2.utc.edu/~djy471/CNS-reading/anderegg03.pdf

Ad hoc-VCG: a truthful and cost-efficient routing protocol for mobile ad hoc networks with selfish agents

Routing cars of trains for a given schedule is a problem that has been studied for a long time. The minimum number of cars to run a schedule can be found eÆciently by means of ow algorithms. Realistic objectives are more complex, with many cost components such as shunting or coupling/decoupling of trains, and also with a variety of constraints such as requirements for regular maintenance. These versions of the problem tend to be NP-hard, and thus the standard powerful tools (e.g. branch-and-bound, branch-and-cut, Lagrangian relaxation, gradient descent) have been used. These methods may guarantee good solutions, but not quick runtimes. In practice, two major railway companies, German Railway and Swiss Federal Railway, do not use either approach. Instead, their schedulers create solutions manually, modifying solutions from the previous year. In this paper, we advocate an intermediate, semiautomatic approach. In reality, not all constraints or objectives can be easily formulated mathematically. To allow for interactive human modi cation of solutions, the system must work rapidly, allowing a user to save desired subsolutions, and modify (or just start over on) the rest. After careful examination to nd which constraints and costs we can easily integrate into a ow model approach, we heuristically modify network ow based solutions to account for remaining constraints. We present experimental results from this approach on real data from the German Railway and Swiss Federal Railway. Work partially supported by the Swiss Federal OÆce for Education and Science under the Human Potential Programme of the European Union under contact no. HPRN-CT-1999-00104 (AMORE) yInstitute of Theoretical Computer Science, ETH Zentrum, Z urich, Switzerland flastnameg@inf.ethz.ch zLos Alamos National Laboratory, eidenben@lanl.gov LA-UR:02-7640 xDepartment of Computer Science, San Jose State University, taylor@cs.sjsu.edu Based on work performed while at ETH Zurich

Train Routing Algorithms: Concepts, Design Choises, and Practical Considerations.

Online Train Disposition: To Wait or Not To Wait?

We deal with an online problem arising from bus/tram/train disposition problems. In particular, we look at the case in which the delay is unknown and the vehicle can only wait in a station so as to minimize the passengers' waiting time.

We present deterministic polynomial-time optimal algorithms and matching lower bounds for several problem versions. In addition, all lower bounds also apply to randomized algorithms, thus implying that using randomization does not help.

Online Train Disposition: To Wait or Not to Wait?

A set of n points in the plane is in equiangular configuration if there exist a center and an ordering of the points such that the angle of each two adjacent points w.r.t. the center is $\frac{360^{\circ}}{n}$, i.e., if all angles between adjacent points are equal. We show that there is at most one center of equiangularity, and we give a linear time algorithm that decides whether a given point set is in equiangular configuration, and if so, the algorithm outputs the center. A generalization of equiangularity is σ-angularity, where we are given a string σ of n angles and we ask for a center such that the sequence of angles between adjacent points is σ. We show that σ-angular configurations can be detected in time O(n4 log n).

Luzi Anderegg

Papers

Ad hoc-VCG: a truthful and cost-efficient routing protocol for mobile ad hoc networks with selfish agents

Train Routing Algorithms: Concepts, Design Choises, and Practical Considerations.

Online Train Disposition: To Wait or Not To Wait?

Online Train Disposition: To Wait or Not to Wait?

Efficient algorithms for detecting regular point configurations