Impact of Obstacles on the Degree of Mobile Ad Hoc Connection Graphs

What is the impact of obstacles on the graphs of connections between stations in Mobile Ad hoc Networks? In order to answer, at least partially, this question, the first step is to define both an environment with obstacles and a mobility model for the stations in such an environment. The present paper focuses on a new way of considering the mobility within environments with obstacles, while keeping the core ideas of the well-known Random WayPoint mobility model (a.k.a RWP). Based on a mesh-partitioning of the space, we propose a new model called RSP-O-G for which we compute the spatial distribution of stations and analyse how the presence of obstacles impacts this distribution compared to the distribution when no obstacles are present. Coupled with a simple model of radio propagation, and according to the density of stations in the environment, we study the mean degree of the connection graphs corresponding to such mobile ad hoc networks

Spatial networks with wireless applications

Many networks have nodes located in physical space, with links more common between closely spaced pairs of nodes. For example, the nodes could be wireless devices and links communication channels in a wireless mesh network. We describe recent work involving such networks, considering effects due to the geometry (convex,non-convex, and fractal), node distribution, distance-dependent link probability, mobility, directivity and interference.Comment: Review article- an amended version with a new title from the origina

Connectivity of Soft Random Geometric Graphs Over Annuli

Nodes are randomly distributed within an annulus (and then a shell) to form a point pattern of communication terminals which are linked stochastically according to the Rayleigh fading of radio-frequency data signals. We then present analytic formulas for the connection probability of these spatially embedded graphs, describing the connectivity behaviour as a dense-network limit is approached. This extends recent work modelling ad hoc networks in non-convex domains.Comment: 12 pages, 6 figure

Message and time efficient multi-broadcast schemes

We consider message and time efficient broadcasting and multi-broadcasting in wireless ad-hoc networks, where a subset of nodes, each with a unique rumor, wish to broadcast their rumors to all destinations while minimizing the total number of transmissions and total time until all rumors arrive to their destination. Under centralized settings, we introduce a novel approximation algorithm that provides almost optimal results with respect to the number of transmissions and total time, separately. Later on, we show how to efficiently implement this algorithm under distributed settings, where the nodes have only local information about their surroundings. In addition, we show multiple approximation techniques based on the network collision detection capabilities and explain how to calibrate the algorithms' parameters to produce optimal results for time and messages.Comment: In Proceedings FOMC 2013, arXiv:1310.459

Betweenness centrality in dense random geometric networks

Random geometric networks consist of 1) a set of nodes embedded randomly in a bounded domain $\mathcal{V} \subseteq \mathbb{R}^d$ and 2) links formed probabilistically according to a function of mutual Euclidean separation. We quantify how often all paths in the network characterisable as topologically `shortest' contain a given node (betweenness centrality), deriving an expression in terms of a known integral whenever 1) the network boundary is the perimeter of a disk and 2) the network is extremely dense. Our method shows how similar formulas can be obtained for any convex geometry. Numerical corroboration is provided, as well as a discussion of our formula's potential use for cluster head election and boundary detection in densely deployed wireless ad hoc networks.Comment: 6 pages, 3 figure

Meta-Routing: Synergistic Merging of Message Routing and Link Maintenance

The maintenance of network connectivity is essential for effective and efficient mobile team operations. Achieving robust mobile ad hoc networks (MANETs) connectivity requires a capable link maintenance mechanism especially if the network experiences expected intermittent connectivity due to a hostile environment. One applicable example of such network scenarios is multi-robot exploration for urban search and rescue (USAR). With the proliferation of these robotic networks, communication problems such as the link maintenance problem are subject to be raised quickly. Although various routing protocols for wireless ad hoc networks have been proposed, they solve the problems of message routing and link maintenance separately, resulting in additional overhead costs and long latency in network communication. Traditional routing protocols discover existing links, connect these links, find the best path and minimize the path cost. The limitation of previous routing protocols motivates us to develop a new concept of routing mechanism for a robotic network. This routing mechanism is named Meta-Routing. Meta-Routing expands current routing protocols to include not only the normal routing of packets, but also the maintenance of links in mobile agent scenarios. Thus, Meta-Routing minimizes the communication path cost and the overhead cost, the latter of which results from discovering a route, repairing a link or establishing a new communication path between nodes. This dissertation presents a method to achieve Meta-Routing by controlling robot motion based on the radio frequency (RF) environment recognition method and gradient descent method. Mobile robot controlled motion can effectively improve network performance by driving robots to favorable locations with strong links. Moreover, the gradient descent method is used in driving the robots into the direction of favorable positions for maximizing broken or failing links and maintaining network connectivity. The main accomplished goals of this thesis are summarized as follows: firstly, the Meta-Routing protocol, which integrates link maintenance into the normal message routing protocol cost function; secondly, the dissertation examines the unification of the syntax of message routing protocol and the link maintenance process through physical configuration of mobile network nodes by controlling their movement in the field; finally, the dissertation demonstrates that the utilization of the RF environment recognition and classification method improves route repair estimation for achieving link maintenance in the presented Meta-Routing protocol. The numerical experimental results demonstrate promising RF environment recognition and node controlled motion results, as well as confirm their abilities in robot movement control for link maintenance and reduction of the total path cost