The Critical Neighbourhood Range for Asymptotic Overlay Connectivity in Ad Hoc Networks

We first motivate the use of ad hoc overlays. In particular, we argue that overlay routing could play a role in the spreading of ad hoc networks. We then define a simple criterion for neighbourhood: two overlay nodes are neighbours if and only if there exists a path between them of at most R hops, and R is called the (overlay) neighbourhood range. A small R may result in a disconnected overlay, while an unnecessarily large R would generate extra control traffic. We are interested in the minimum R ensuring overlay connectivity, the so-called critical R. We study conditions on R to achieve asymptotic connectivity of the overlay almost surely, i.e. connectivity with probability 1 when the number of nodes in the underlying ad hoc network tends to infinity (so-called dense networks) or when the size of the field tends to infinity (socalled sparse networks), under the hypothesis that the underlying ad hoc network is itself asymptotically almost surely connected. For dense networks, we derive a necessary and sufficient condition on R, and for sparse networks we derive distinct necessary and sufficient conditions that are however asymptotically tight. These conditions, though asymptotic, shed some light on the relation linking the critical R to the number of nodes n, the field size the radio transmission range r and the overlay density D (i.e., the proportion of overlay nodes). These conditions can be considered as approximations when the number of nodes (resp. the field) is large enough. Since r is considered as a function of n or l , we are able to study the impact of topology control mechanisms, by showing how the shape of this function impacts the critical R.PAI MOTIO

The Critical Neighbourhood Range for Asymptotic Overlay Connectivity in Dense Ad Hoc Networks

peer reviewedWe define, for an overlay built on top of an ad hoc network, a simple criterion for neighbourhood: two overlay nodes are neighbours if and only if there exists a path between them of at most R hops, and R is called the (overlay) neighbourhood range. A small R may result in a disconnected overlay, while an unnecessarily large R would generate extra control traffic. We are interested in the minimum R ensuring overlay connectivity, the so-called critical R. We derive a necessary and sufficient condition on R to achieve asymptotic connectivity of the overlay almost surely, i.e. connectivity with probability 1 when the number of overlay nodes tends to infinity, under the hypothesis that the underlying ad hoc network is itself asymptotically almost surely connected. This condition, though asymptotic, sheds some light on the relation linking the critical R to the number of nodes n, the normalized radio transmission range r and the overlay density D (i.e., the proportion of overlay nodes). This condition can be considered as an approximation when the number of nodes is large enough. Since r is considered as a function of n, we are able to study the impact of topology control mechanisms, by showing how the shape of this function impacts the critical R.PAI MOTIO

Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: vehicular ad-hoc networks, security and caching, TCP in ad-hoc networks and emerging applications. It is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks

Performance analysis of a hybrid topology CDD/TDD-CDMA network architecture

Student Number : 0006936H - MSc research report - School of Electrical and Information Engineering - Faculty of Engineering and the Built EnvironmentCode division duplexing (CDD) has steadily garnered attention in the telecommunication community. In this project report we propose a physical layer implementation of CDD that utilizes orthogonal Gold codes as the means of differentiating transmission directions, in order to implement an ad-hoc networking infrastructure that is overlaid on a standard mobile networking topology, and hence creating a hybrid networking topology. The performance of the CDD based system is then comparatively assessed in two ways: from the perspective of the physical layer using point-to-point simulations and from the perspective of the network layer using an iterative snapshot based simulation where node elements are able to setup connections based on predefined rules

Efficient Data Dissemination in Wireless Ad Hoc Networks

In this thesis, we study the problem of efficient data dissemination in wireless sensor and mobile ad hoc networks. In wireless sensor networks we study two problems: (1) construction of virtual backbones and clustering hierarchies to achieve efficient routing, and (2) placement of multiple sinks, where each sensor is at a bounded distance to several sinks, to analyze and process data before sending it to a central unit. Often connected dominating sets have been used for such purposes. However, a connected dominating set is often vulnerable due to frequent node failures in wireless sensor networks. Hence, to provide a degree of fault-tolerance we consider in problem (1) a 2-connected (k,r)-dominating set, denoted D(2,k,r), to act as a virtual backbone or a clustering hierarchy, and in problem (2) a total (k,r)-dominating set to act as sinks in wireless sensor networks. Ideally, the backbone or the number of sinks in the network should constitute the smallest percentage of nodes in the network. We model the wireless sensor network as a graph. The total (k,r)-dominating set and the 2-connected (k,r)-dominating set have not been studied in the literature. Thus, we propose two centralized approximation algorithms to construct a D(2,k,r) in unit disk graphs and in general graphs. We also derive upper bounds on the total (k,r)-domination number in graphs of girth at least 2k+1 as well as in random graphs with non-fixed probability p. In mobile ad hoc networks we propose a hexagonal based beacon-less flooding algorithm, HBLF, to efficiently flood the network. We give sufficient condition that even in the presence of holes in the network, HBLF achieves full delivery. Lower and upper bounds are given on the number of forwarding nodes returned by HBLF in a network with or without holes. When there are no holes in the network, we show that the ratio of the shortest path returned by HBLF to the shortest path in the network is constant. We also present upper bounds on the broadcast time of HBLF in a network with or without holes

From MANET to people-centric networking: Milestones and open research challenges

In this paper, we discuss the state of the art of (mobile) multi-hop ad hoc networking with the aim to present the current status of the research activities and identify the consolidated research areas, with limited research opportunities, and the hot and emerging research areas for which further research is required. We start by briefly discussing the MANET paradigm, and why the research on MANET protocols is now a cold research topic. Then we analyze the active research areas. Specifically, after discussing the wireless-network technologies, we analyze four successful ad hoc networking paradigms, mesh networks, opportunistic networks, vehicular networks, and sensor networks that emerged from the MANET world. We also present an emerging research direction in the multi-hop ad hoc networking field: people centric networking, triggered by the increasing penetration of the smartphones in everyday life, which is generating a people-centric revolution in computing and communications

Efficient, Reliable and Secure Distributed Protocols for MANETs

This thesis is divided into two parts. The first part explores the difficulties of bootstrapping and maintaining a security infrastructure for military Mobile Ad Hoc NETworks (MANETs). The assumed absence of dedicated infrastructural elements necessitates, that security services in ad hoc networks may be built from the ground up. We develop a cluster algorithm, incorporating a trust metric in the cluster head selection process to securely determine constituting nodes in a distributed Trust Authority (TA) for MANETs. Following this, we develop non-interactive key distribution protocols for the distribution of symmetric keys in MANETs. We explore the computational requirements of our protocols and simulate the key distribution process. The second part of this thesis builds upon the security infrastructure of the first part and examines two distributed protocols for MANETs. Firstly, we present a novel algorithm for enhancing the efficiency and robustness of distributed protocols for contacting TA nodes in MANETs. Our algorithm determines a quorum of trust authority nodes required for a distributed protocol run based upon a set of quality metrics, and establishes an efficient routing strategy to contact these nodes. Secondly, we present a probabilistic path authentication scheme based on message authentication codes (MACs). Our scheme minimises both communication and computation overhead in authenticating the path over which a stream of packets travels and facilitates the detection of adversarial nodes on the path

Radio Communications

In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks