Free-space optical communications (FSOC) has the potential to offer significant capacity advantages for future military communication networks. Due to link fragility, it is likely that FSOC networks will suffer from intermittent connectivity. Delay Tolerant Networking (DTN) has been proposed as a potential solution for this technical challenge as it is designed to offer a solution for routing in a network which is not always connected. This paper examines DTN-based FSOC networks in a variety of mobility models and examines the performance of the network.

Performance of DTN-Based Free-Space Optical Networks with Mobility

With the growth in demand for capacity from users in wireless networks and the scarcity of available RF spectrum, directional networks are expected to provide effective solutions. Directional RF antennas offer increased capacity over omni-directional antenna networks and some emerging highly-directional networks like free-space optical communication (FSOC) systems will be an important part of future networking infrastructures. The ability to construct and manage an optical network has challenges such as topology control involving the scheduling of pointing, acquisition and tracking events. In many of these directional systems, especially in FSOC where links may be fragile, this will result in an intermittently-connected network, though of tremendous capacity on a per-link basis. This paper establishes delay (or disruption) tolerant networking (DTN) algorithms for such networks and evaluates these new algorithms with mobility, communications constraints, network traffic loads and quality of service (QoS) provisions.

DTN-based free-space optical and directional RF networks

Due to high traffic demands, networks are increasingly required to implement techniques which support prioritization. Internet Quality of Service (QoS) approaches such as Differentiated Services (Diffserv) and Integrated Services (Intserv) can function in a traditional provider network. However, in some domains these techniques are not straightforward to implement. Wireless networks are increasingly using directional networking capabilities to handle increased traffic demands. However, prioritization techniques for such networks are in the research phase. In this paper we propose an approach to prioritize traffic in these types of networks using the principles of Quality of Information (QoI). We build on previous work which established topology control and routing approaches for directional networks using Delay/Disruption-Tolerant Networking (DTN). We extend this framework to support varied information quality.

QoI in DTN-based directional networks

The hierarchical influence mobility model that can take care of many heterogeneous classes of mobile nodes is described. We have explained how the HIMM can be used to model the simultaneous presence and movement of these classes those influence the mobility pattern of their members in a variety of random and deterministic manner s. Moreover, it is also explained that the HIMM framework can be used for wider applications in addition to the MANET .

Hierarchical Influence Mobility

The new class of hierarchical goal-oriented mobility models is introduced for the study of mobile ad hoc networks. The new models introduce role-based actors whose mobility behavior can vary in many different ways. The new models provide a flexible framework with aspects of both group (spatially correlated) and entity (spatially uncorrected) mobility models. The hierarchical rendezvous models in particular provide an abstract representation of civilian and military operations involving dynamic tasking of small teams that form, separate, and reform over time on an ad-hoc basis. The models were motivated by the authors' research into protocols for highly directional delay tolerant MANETs for which the mobility model has significant performance implications. These are illustrated through simulation results of the authors' Transient Information Level (TIL) protocol.

A.R. Hammons

Papers

Hierarchical Goal-Oriented Mobility Models with Applications to Mobile Ad-Hoc Networks