There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

A new approximation algorithm for maximum weighted matching in general edge-weighted graphs is presented. It calculates a matching with an edge weight of at least of the edge weight of a maximum weighted matching. Its time complexity is O(|E|), with |E| being the number of edges in the graph. This improves over the previously known -approximation algorithms for maximum weighted matching which require O(|E| log(|V|)) steps, where |V| is the number of vertices.

Linear Time 1/2-Approximation Algorithm for Maximum Weighted Matching in General Graphs

Energy-efficiency in target tracking applications has been extensively studied in the literature of Wireless Sensor Networks (WSN). However, there is little work which has been done to survey and summarize this effort. In this paper, we address the lack of these studies by giving an up-to-date State-of-the-Art of the most important energy-efficient target tracking schemes. We propose a novel classification of schemes that are based on the interaction between the communication subsystem and the sensing subsystem on a single sensor node. We are interested in collaborative target tracking instead of single-node tracking. In fact, WSNs are often of a dense nature, and redundant data that can be received from multiple sensors help at improving tracking accuracy and reducing energy consumption by using limited sensing and communication ranges. We show that energy-efficiency in a collaborative WSN-based target tracking scheme can be achieved via two classes of methods: sensing-related methods and communication-related methods. We illustrate both of them with several examples. We show also that these two classes can be related to each other via a prediction algorithm to optimize communication and sensing operations. By self-organizing the WSN in trees and/or clusters, and selecting for activation the most appropriate nodes that handle the tracking task, the tracking algorithm can reduce the energy consumption at the communication and the sensing layers. Thereby, network parameters (sampling rate, wakeup period, cluster size, tree depth, etc.) are adapted to the dynamic of the target (position, velocity, direction, etc.). In addition to this general classification, we discuss also a special classification of some protocols that put specific assumptions on the target nature and/or use a "non-standard" hardware to do sensing. At the end, we conduct a theoretic comparison between all these schemes in terms of objectives and mechanisms. Finally, we give some recommendations that help at designing a WSN-based energy efficient target tracking scheme.

https://hal.archives-ouvertes.fr/hal-00957917/document

On Energy Efficiency in Collaborative Target Tracking in Wireless Sensor Network: A Review

The possibility of controlling and directing a complex system's behavior at will is rooted in its interconnectivity and can lead to significant advances in disparate fields, ranging from nationwide energy saving to therapies that involve multiple targets. In this work, we address complex network controllability from the perspective of the minimum dominating set (MDS). Our theoretical calculations, simulations using artificially generated networks as well as real-world network analyses show that the more heterogeneous a network degree distribution is, the easier it is to control the entire system. We demonstrate that relatively few nodes are needed to control the entire network if the power-law degree exponent is smaller than 2, whereas many nodes are required if it is larger than 2.

/pdf/dominating-scale-free-networks-with-variable-scaling-5d0io0v5k7.pdf

Dominating scale-free networks with variable scaling exponent: heterogeneous networks are not difficult to control

Several routing schemes in ad hoc networks first establish a virtual backbone and then route messages via back-bone nodes. One common way of constructing such a backbone is based on the construction of a minimum connected dominating set (CDS). In this paper we present a very simple distributed algorithm for computing a small CDS. Our algorithm has an approximation factor of at most 6.91, improving upon the previous best known approximation factor of 8 due to Wan et al. [INFOCOM'02], The improvement relies on a refined analysis of the relationship between the size of a maximal independent set and a minimum CDS in a unit disk graph. This subresult also implies improved approximation factors for many existing algorithm.

A Simple Improved Distributed Algorithm for Minimum CDS in Unit Disk Graphs

In the last several years IEEE 802.15.4 has been accepted as a major MAC layer protocol for wireless sensor networks (WSNs) and has attracted the interest of there search community involved in security issues as the increased range of application scenarios bring out new possibilities for misuse and taking improper advantage of sensor nodes and their operation. As these nodes are very resource restrained such possible attacks and their early detection must be carefully considered. This paper surveys the known attacks on wireless sensor networks, identifies and investigates a new attack, guaranteed time slot (GTS) attack, taking as a basis the IEEE 802.15.4 MAC protocol for WSN. The GTS attack is simulated with different scenarios using ns-2 and the results are evaluated both from the point of view of the attacked and the attacker.

/pdf/on-the-ieee-802-15-4-mac-layer-attacks-gts-attack-5alui5r2k4.pdf

On the IEEE 802.15.4 MAC Layer Attacks: GTS Attack

We propose a new Connected Dominating Set (CDS) based algorithm for clustering in Mobile Ad hoc Networks (MANETs). Our algorithm is based on Wu and Li’s [14] algorithm, however we provide significant modifications by considering the degrees of the nodes during marking process and also provide further heuristics to determine the color of a node in the initial phase. We describe, analyze and measure performance of this new algorithm by simulation and show that it performs better than Wu and Li’s [14] algorithm especially in the case of dense networks.

/pdf/a-dominating-set-based-clustering-algorithm-for-mobile-ad-1ermpnwd0h.pdf

A dominating set based clustering algorithm for mobile ad hoc networks

Leader Election is an important problem in mobile ad hoc networks and in distributed computing systems. In this study, we propose a hierarchical, cluster based protocol to elect a leader in a mobile ad hoc network. The initial phase of the protocol employs a clustering algorithm to group nodes of the network after which a leader for a cluster(clusterhead) is elected. The second phase is performed by forming a connected ring of these leaders using the Ring Formation Algorithm. Finally, Chang Roberts Leader Election Algorithmfor rings is employed in the final phase to elect the super-leader among the clusterheads. We provide performance results of this protocol for various mobility parameters and analyze its time and message complexities.

/pdf/a-hierarchical-leader-election-protocol-for-mobile-ad-hoc-14f5boal2j.pdf

A Hierarchical Leader Election Protocol for Mobile Ad Hoc Networks

IEEE 802.15.4 has been established as a dominant MAC layer protocol for wireless sensor networks (WSNs). Recently the security concepts of sensor networks have quickly gained more significance because of two major factors: widening the range and variety of possible applications and increased implementation rate. Because the nodes are very resource-constrained, the attacks on these networks and detection of the attacks must carefully be considered. This paper dissects the known attacks on wireless sensor networks and also identifies two new attacks: PANId conflict attack, and Guaranteed Time Slot (GTS) attack taking as a basis the IEEE 802.15.4 MAC protocol for WSN. The attack evaluations are analyzed from the perspectives of the attacker and the network. A detection mechanism for PANId conflict attack is presented, and the simulation results for this attack implementation on ns2 are given. Keywords— IEEE 802.15.4 MAC, attack, wireless sensor networks, PANId conflict attack, GTS attack.

An Investigation on IEEE 802.15.4 MAC Layer Attacks

Wireless sensor networks (WSNs) do not have a fixed infrastructure and consist of sensor nodes that perform sensing and communicating tasks. The WSNs have large application spectrum such as habitat monitoring, military surveillance, and target tracking, where sensor nodes may operate distributed in highly dynamic environments. Battery-constrained sensor nodes may aggregate the sensed data, localize themselves, and route the packets in an energy-efficient and decentralized manner to enable running the applications. Agents are capable of independent and autonomous action, so that they can successfully carry out tasks that have been delegated to them, thus agent-based approaches are very suitable to apply as the solution of the problems occurring in WSNs. So far many agent-based approaches were proposed for WSNs. This paper surveys the agent technologies for sensor networks by providing a classification, objectives and costs of these approaches with the open research problems. To the best of our knowledge, this is the first study that covers the intersection of the agent technology and sensor networks from a wide perspective.

/pdf/a-survey-of-agent-technologies-for-wireless-sensor-networks-mzvsoz7bfb.pdf

Orhan Dagdeviren

Papers

On the IEEE 802.15.4 MAC Layer Attacks: GTS Attack

A dominating set based clustering algorithm for mobile ad hoc networks

A Hierarchical Leader Election Protocol for Mobile Ad Hoc Networks

An Investigation on IEEE 802.15.4 MAC Layer Attacks

A Survey of Agent Technologies for Wireless Sensor Networks