This document describes the Optimized Link State Routing (OLSR) protocol for mobile ad hoc networks. The protocol is an optimization of the classical link state algorithm tailored to the requirements of a mobile wireless LAN. The key concept used in the protocol is that of multipoint relays (MPRs). MPRs are selected nodes which forward broadcast messages during the flooding process. This technique substantially reduces the message overhead as compared to a classical flooding mechanism, where every node retransmits each message when it receives the first copy of the message. In OLSR, link state information is generated only by nodes elected as MPRs. Thus, a second optimization is achieved by minimizing the number of control messages flooded in the network. As a third optimization, an MPR node may chose to report only links between itself and its MPR selectors. Hence, as contrary to the classic link state algorithm, partial link state information is distributed in the network. This information is then used for route calculation. OLSR provides optimal routes (in terms of number of hops). The protocol is particularly suitable for large and dense networks as the technique of MPRs works well in this context.

https://hal.inria.fr/inria-00471712/document

Optimized Link State Routing Protocol (OLSR)

Networked sensors-those that coordinate amongst themselves to achieve a larger sensing task-will revolutionize information gathering and processing both in urban environments and in inhospitable terrain. The sheer numbers of these sensors and the expected dynamics in these environments present unique challenges in the design of unattended autonomous sensor networks. These challenges lead us to hypothesize that sensor network coordination applications may need to be structured differently from traditional network applications. In particular, we believe that localized algorithms (in which simple local node behavior achieves a desired global objective) may be necessary for sensor network coordination. In this paper, we describe localized algorithms, and then discuss directed diffusion, a simple communication model for describing localized algorithms.

https://www.cs.jhu.edu/~cs647/class-papers/Sensor%20Nets/estrin.pdf

Next century challenges: scalable coordination in sensor networks

Underwater sensor nodes will find applications in oceanographic data collection, pollution monitoring, offshore exploration, disaster prevention, assisted navigation and tactical surveillance applications. Moreover, unmanned or autonomous underwater vehicles (UUVs, AUVs), equipped with sensors, will enable the exploration of natural undersea resources and gathering of scientific data in collaborative monitoring missions. Underwater acoustic networking is the enabling technology for these applications. Underwater networks consist of a variable number of sensors and vehicles that are deployed to perform collaborative monitoring tasks over a given area. In this paper, several fundamental key aspects of underwater acoustic communications are investigated. Different architectures for two-dimensional and three-dimensional underwater sensor networks are discussed, and the characteristics of the underwater channel are detailed. The main challenges for the development of efficient networking solutions posed by the underwater environment are detailed and a cross-layer approach to the integration of all communication functionalities is suggested. Furthermore, open research issues are discussed and possible solution approaches are outlined. � 2005 Published by Elsevier B.V.

/pdf/underwater-acoustic-sensor-networks-research-challenges-15fjl1gvhc.pdf

Underwater acoustic sensor networks: research challenges

Ad hoc networks are a new wireless networking paradigm for mobile hosts. Unlike traditional mobile wireless networks, ad hoc networks do not rely on any fixed infrastructure. Instead, hosts rely on each other to keep the network connected. Military tactical and other security-sensitive operations are still the main applications of ad hoc networks, although there is a trend to adopt ad hoc networks for commercial uses due to their unique properties. One main challenge in the design of these networks is their vulnerability to security attacks. In this article, we study the threats on ad hoc network faces and the security goals to be achieved. We identify the new challenges and opportunities posed by this new networking environment and explore new approaches to secure its communication. In particular, we take advantage of the inherent redundancy in ad hoc networks-multiple routes between nodes-to defend routing against denial-of-service attacks. We also use replication and new cryptographic schemes, such as threshold cryptography, to build a highly secure and highly available key management service, which terms the core of our security framework.

/pdf/securing-ad-hoc-networks-3hudjv4io2.pdf

Securing ad hoc networks

The theory of directed graphs has developed enormously over recent decades, yet this book (first published in 2000) remains the only book to cover more than a small fraction of the results. New research in the field has made a second edition a necessity. Substantially revised, reorganised and updated, the book now comprises eighteen chapters, carefully arranged in a straightforward and logical manner, with many new results and open problems. As well as covering the theoretical aspects of the subject, with detailed proofs of many important results, the authors present a number of algorithms, and whole chapters are devoted to topics such as branchings, feedback arc and vertex sets, connectivity augmentations, sparse subdigraphs with prescribed connectivity, and also packing, covering and decompositions of digraphs. Throughout the book, there is a strong focus on applications which include quantum mechanics, bioinformatics, embedded computing, and the travelling salesman problem. Detailed indices and topic-oriented chapters ease navigation, and more than 650 exercises, 170 figures and 150 open problems are included to help immerse the reader in all aspects of the subject. Digraphs is an essential, comprehensive reference for undergraduate and graduate students, and researchers in mathematics, operations research and computer science. It will also prove invaluable to specialists in related areas, such as meteorology, physics and computational biology.

Digraphs Theory Algorithms And Applications

We investigate broadcasting in mobile ad-hoc networks (MANETs). We define broadcasting as being the process of delivering one packet, originated at one node, to (ideally) all other nodes in the MANET. We present specific problems related to broadcasting in MANETs, as well as four broadcast protocols aimed at providing MANET-wide broadcast. Further, three protocol-independent modifications are presented. One aimed at ensuring that a broadcast packet traverses at least the "shortest path" to its destinations, and two aimed at increasing the fraction of nodes which receive a broadcast packet. Through simulation studies, we evaluate the performance characteristics of the broadcast protocols and generic modifications under different conditions.

/pdf/investigating-data-broadcast-performance-in-mobile-ad-hoc-13m7p2okt9.pdf

Investigating data broadcast performance in mobile ad-hoc networks

In this paper, we evaluate the performance of two MANET routing protocols under varying traffic, density and mobility conditions. We observe, that a rather large fraction of the traffic being carried on the Internet today carries TCP. Thus, Internet traffic has inheritly different characteristics than that of CBR traffic, which is the commonly used traffic type for evaluating MANET routing protocol performance. Hence, in this paper, we extend our evaluations of the two protocols to include the performance of both TCP and CBR traffic. We find, that testing a protocol using CBR traffic is not a good indicator for the same protocols performance when subject to TCP traffic.

https://hal.inria.fr/inria-00471707/document

Comparative Study of CBR and TCP Performance of MANET Routing Protocols

New technologies and the deployment of mobile and nomadic services are driving the emergence of complex communications networks, that have a highly dynamic behavior. Modeling such dynamics, and designing algorithms that take it into account, received considerable attention recently. In this note, we discuss a formal generalization of dynamic graphs, the evolving graphs, which aims at harnessing the complexity of an evolving setting as yielded by dynamic communication networks. We argue that evolving graphs are of great help when dealing with fixed-schedule networks. Moreover, we show how to exploit our model with networks where short time prediction is available.

https://hal.inria.fr/inria-00072185/document

A Note on Models, Algorithms, and Data Structures for Dynamic Communication Networks

This paper proposes a general, parameterized model for analyzing protocol control overheads in mobile ad-hoc networks. A probabilistic model for the network topology and the data traffic is proposed in order to estimate overhead due to c ontrol packets of routing protocols. Our analytical model is validated by comparisons with simulations, both taken from litterature and made specifically for this paper. We identify the model parameters for protocols like AODV, DSR and OLSR, and confirm that our model corresponds with the simulation results Our model permits accurate predictions of which protocol will yield the lowest overhead depending on the node mobility and traffic pattern.

Analyzing control Traffic Overhead in Mobile Ad-hoc Network Protocols versus Mobility and Data Traffic Activity

Motivated by the fact that neighbors are generally known in practical routing algorithms, we introduce the notion of remote-spanner. Given an unweighted graph G, a sub-graph H with vertex set V (H) = V (G) is an (α, β)-remote-spanner if for each pair of points u and v the distance between u and v in Hu, the graph H augmented by all the edges between u and its neighbors in G, is at most α times the distance between u and v in G plus β. We extend this definition to k-connected graphs by considering the minimum length sum over k disjoint paths as a distance. We then say that an (α, β)-remote-spanner is k-connecting. In this paper, we give distributed algorithms for computing (1 + e, 1 − 2e)-remote-spanners for any e ≫ 0, k-connecting (1, 0)-remote-spanners for any k ≥ 1 (yielding (1, 0)-remote-spanners for k = 1) and 2-connecting (2,−1)-remote-spanners. All these algorithms run in constant time for any unweighted input graph. The number of edges obtained for k-connecting (1, 0)-remote-spanner is within a logarithmic factor from optimal (compared to the best k-connecting (1, 0)-remote-spanner of the input graph). Interestingly, sparse (1, 0)-remote-spanners (i.e. preserving exact distances) with O(n4/3) edges exist in random unit disk graphs. The number of edges obtained for (1+e, 1−2e)-remote-spanners and 2-connecting (2,−1)-remote-spanners is linear if the input graph is the unit ball graph of a doubling metric (even if distances between nodes are unknown). Our methodology consists in characterizing remote-spanners as sub-graphs containing the union of small depth tree sub-graphs dominating nearby nodes. This leads to simple local distributed algorithms.

/pdf/remote-spanners-what-to-know-beyond-neighbors-2p10qo78n3.pdf

Laurent Viennot

Papers

Investigating data broadcast performance in mobile ad-hoc networks

Comparative Study of CBR and TCP Performance of MANET Routing Protocols

A Note on Models, Algorithms, and Data Structures for Dynamic Communication Networks

Analyzing control Traffic Overhead in Mobile Ad-hoc Network Protocols versus Mobility and Data Traffic Activity

Remote-spanners: What to know beyond neighbors