We present a novel distributed range-free technique called ExPLoIT for estimating geographical location of sensor nodes in mobile sensor networks. ExPLoIT is the first positioning technique that exploits location information at regular nodes in addition to using seeds. The key idea is the notion of confidence that a node has in its location estimate which can be used by other nodes for localization. Using Monte Carlo integration, a node estimates its current location and confidence based on its past location and the location information it receives from its neighbors. Node mobility is exploited to transitively localize the network. Our extensive simulation study shows that our proposal outperforms three other state-of-the-art range-free localization techniques under a wide range of conditions. The strength of ExPLoIT is that it is robust to irregular radio propagation, arbitrary seed and node density, and stochastic seed and node mobility; no special hardware is necessary at sensor nodes.

Delay tolerant networking (DTN), and more specifically the subset known as intermittently connected networking, is emerging as a solution for supporting asynchronous data transfers in challenging environments where a fully connected end-to-end path between a source and destination may never exist. Message delivery in such networks is enabled via scheduled or opportunistic communication based on transitive local connectivity among nodes influenced by factors such as node mobility. Given the inherently store-and-forward and opportunistic nature of the DTN architecture, the choice of buffer management policies and message forwarding strategies can have a major impact on system

performance. In this paper, we propose and evaluate different

combinations of queueing policies and forwarding strategies for

intermittently connected networks. We show that a probabilistic

routing approach along with the correct choice of buffer management policy and forwarding strategy can result in much performance improvements in terms of message delivery, overhead

and end-to-end delay.

The ability to dynamically configure mobile ad-hoc network (MANET) devices is critical for supporting complex services such as quality of service (QoS), security and access control in these networks. In our work, we address the problem of policy distribution and provisioning in MANETs. Previously, we have proposed solutions that enable the operator, e.g., a military command and control center, to maintain a logically centralized control of the network as a whole, while allowing a physically decentralized, automated and self-managing implementation essential for a MANET environment. Our policy provisioning architecture consists of: a new service discovery mechanism for allowing MANET nodes to discover policy servers in the network; k-hop clustering for efficient, localized management; Dynamic Service Redundancy (DynaSeR) technique for improving policy service availability in the face of node mobility; and policy negotiation for seamlessly managing network nodes moving across MANET subnetworks owned by different organizations. In this paper, we present an analytical model of the availability of the policy distribution service in a MANET and analyze the performance using stochastic Petri nets (SPNs). We develop the model at two levels of complexity: as a simple Markovian model with Poisson assumptions and as a more accurate non-Markovian model with general distributions obtained using statistical parameterization. We compare and cross-validate the analytical results with simulation and experimental results. Finally, we illustrate the effectiveness of the architecture for managing QoS for soft real-time applications, using an emulated mobile ad-hoc network testbed.

Today, intermittent connectivity is common in wireless access networks and it seems like mobile users will have to deal with discontinuous network access in the future. But existing network protocol architectures are not resilient to disruption of communication links and often communication fails when faced with sporadic connectivity. We discuss a new paradigm for wireless access called opportunistic collaborative networking, where communication is disruption-tolerant and wireless devices exploit any opportunity of communication, albeit temporary, to forward messages towards the destination. For developing protocols for these innovative networks requires understanding of their structure and dynamics. We present some results from analysis of real-life traces representing two such mobile network environments with ad-hoc, intermittent connectivity.

IEEE 802.11 technologies are expected to remain the popular wireless local area networking solution for home and office environments. With growing interest within the process and manufacturing industry to go wireless, these technologies are a natural choice for enabling tetherless control and maintenance. However, the use of IEEE 802.11 suite of protocols for wireless access in unconventional, harsh environments is limited and their behavior and performance in these settings is not yet well understood. A prime example of such a setting is the LKAB underground iron-ore mine in Kiruna, Sweden. LKAB envisions an economical and effective wireless access solution in the mines for increasing automation, e.g., remotely control mining equipment such as mobile loading machines and drilling equipment. In this paper, we present our experiences of operating an IEEE 802.11g based wireless network in the LKAB underground iron-ore mine. Using measurements, we characterize and model the environment and its effect on the performance of higher layer protocols. We derive the theoretical limits of IEEE 802.11g and compare them with our experimental results. We observe a highly reflective environment in the mine, which causes multipath fading and in turn, considerably degrades the maximum achievable throughput in practice.

Quality of service (QoS) provisioning and management in ad hoc networks remains a challenging task. Policy-Based Network Management (PBNM) is one approach for QoS provisioning and management that has met with considerable interest in the networking community. However, its application has so far been limited mainly to fixed high-bandwidth networks. We extend and apply the policy-approach for QoS management in ad hoc networks. In this paper, we present our proposed policy-based management framework for wireless ad hoc networks, and briefly describe our proposed characteristics-based taxonomy that provides a platform to analyze and compare different architectural choices. We propose a solution suite that helps achieve our goal of a self-organizing, robust and efficient management system. One of the main contributions of this work is the prototype implementation and testing of the mechanisms and protocols comprising our framework in a multi-hop ad hoc network environment. Experiments are conducted using both an emulated ad hoc network testbed and a true wireless testbed. Degradation in management system performance is observed with an increase in the number of hops between a policy server and client. Our proposed k-hop clustering algorithm alleviates this problem by controlling the number of hops between a server and client. We demonstrate the operation of our prototype implementation, illustrating QoS management in a multi-domain ad hoc network environment using the proposed cluster management, redirection, and policy negotiation mechanisms.

Large-scale real-time distributed applications for real-time control are emerging in many domains including defense, space, financial markets, telecommunication, and industrial automation. To guarantee the performance of these applications operating in large IP internetworks, a scalable quality of service (QoS) architecture is needed. While considerable work has been done in real-time scheduling and bandwidth reservation schemes, the issues of scalability and feasibility of these schemes in actual networks remain largely unexplored. We propose a scalable QoS architecture in support of real-time systems, and focus on the implementation and testing of our proposed architecture using a network testbed. The key modules of our implementation are a real-time middleware, a graphical performance-monitoring tool, and a policy-based management software. We have integrated these applications with an existing Linux Traffic Control (TC) tool to deploy a scalable DiffServ-like QoS architecture. Our evaluation shows that the proposed architecture considerably improves performance of real-time applications as compared to the "best-effort" case.

The integration of various network-level functions, including routing, management and security, is critical to the efficient operation of a mobile ad hoc network (MANET). In this paper, we discuss the design and implementation of a new ad hoc routing protocol, a suite of solutions for policy-based network management, and approaches for key management and deployment of IPsec in a MANET. These solutions, in turn, were integrated with real-time middleware, a secure radio link and a topology monitoring tool. We briefly describe each component of the solution and focus on the challenges and approaches to integrate these components in a cohesive system to support network mobility. We evaluated the effectiveness of the system through experiments conducted in a wireless ad hoc testbed.

Management of mobile ad hoc networks (MANETs) is a challenging task. Previous works in this field have focused largely on the monitoring and data collection aspects of network management; literature on the provisioning of devices and protocol support for MANET configuration is scarce. In this paper, we present a solution suite to extend policy-based management, for the first time, to MANETs. The solution suite consists of four schemes – k-hop clustering, Dynamic Service Redundancy (DynaSeR), policy negotiation, and automated service discovery – each addressing different challenges in managing ad hoc networks. We propose extensions to the standard Common Open Policy Service (COPS) protocol for use in MANETs, and evaluate the system performance using simulations.

Quality of service (QoS) provisioning and management in ad hoc networks remains a challenging task. Existing research focuses either on providing QoS or on network management, in ad hoc networks. However, a comprehensive approach to QoS management in ad hoc networks, i.e., network management in support of service differentiation, QoS robustness, and network survivability is still lacking. In this paper, we survey the existing literature on ad hoc network management from a QoS perspective. We identify policy-based management as a promising approach for QoS provisioning and management in ad hoc networks, and describe the components that we believe are crucial for effective functioning of such a policy-based framework. Our initial experimental results in assessing signaling overhead and response time for network management in ad hoc networks support the choice of a hybrid policy architecture that combines outsourcing and provisioning policy distribution models.