Tuple Space Coordination Across Space & Time

CAST is a coordination model designed to support interactions among agents executing on hosts that make up a mobile ad hoc network (MANET). From an application programmer’s point of view, CAST makes it possible for operations to be executed at arbitrary locations in space, at prescribed times which may be in the future, and on remote hosts even when no end-to-end connected route exists between the initiator and target(s) of the operation. To accomplish this, CAST assumes that each host moves in space in accordance with a motion profile which is accurate but which at any given time extends into the future for a limited duration. These motion profiles are freely exchanged among hosts in the network through a gossiping protocol. Knowledge about the motion profiles of the other hosts in the network allows for source routing of operation requests and replies over disconnected routes. In this paper, we present the CAST model and its formalization. We also discuss the feasibility of realizing this mode

Accommodating Transient Connectivity in Ad Hoc and Mobile Settings

Much of the work on networking and communications is based on thepremise that components interact in one of two ways: either they are connected viaa stable wired or wireless network, or they make use of persistent storage repositoriesaccessible to the communicating parties. A new generation of networks raises seri-ous questions about the validity of these fundamental assumptions. In mobile ad hocwireless networks connections are transient and availability of persistent storage is rare.This paper is concerned with achieving communication among mobile devices that maynever find themselves in direct or indirect contact with each other at any point in time.A unique feature of our contribution is the idea of exploiting information associatedwith the motion and availability profiles of the devices making up the ad hoc network.This is the starting point for an investigation into a range of possible solutions whoseessential features are controlled by the manner in which motion profiles are acquiredand the extent to which such knowledge is available across an ad hoc networ

SOWER: Self-­Organizing Wireless Network for Messaging

Short Message Service (SMS) has become extremely popular in many countries, and represents a multi-billion dollars market. Yet many consumers consider that the price cellular network operators charge for it is too high. In this paper, we explain that there exist alternatives to cellular networks for the provision of SMS. In particular, we present the Self-Organizing Wireless messaging nEtwoRk (SOWER), an all-wireless network operable in cities. In SOWER, each user installs a wireless, power-plugged, device at home and communicates by means of a mobile device. Based on our experimental measurements of IEEE 802.11 equipped devices, we show the feasibility of the concept in various urban scenarios. We also show that city-wide connectivity can be achieved even with a limited market penetration. We propose an appropriate routing protocol, and we explain that the capacity of such networks is sufficient to support messaging communication

A mobile code bundle extension for application-defined routing in delay and disruption tolerant networking

Grup de recerca SENDA (Security of Network and Distributed Applications)In this paper, we introduce software code to improve Delay and Disruption Tolerant Networking (DTN) performance. DTN is extremely useful when source and destination nodes are intermittently connected. DTN implementations use application-specific routing algorithms to overcome those limitations. However, current implementations do not support the concurrent execution of several routing algorithms. In this paper, we contribute to this issue providing a solution that consists on extending the messages being communicated by incorporating software code for forwarding, lifetime control and prioritisation purposes. Our proposal stems from the idea of moving the routing algorithms from the host to the message. This solution is compatible with Bundle Protocol (BP) and facilitates the deployment of applications with new routing needs. A real case study based on an emergency scenario is presented to provide details of a real implementation. Several simulations are presented to prove the feasibility and usability of the system and to analyse its performance in comparison to state-of-the-art approaches

Routing in Delay Tolerant Networks Using Storage Domains

Affiliation: Padma Mundur is with the Institute for Advanced Computer Studies (UMIACS), University of Maryland, College Park, MD 20742 (e-mail: [email protected]). Sookyoung Lee is with the Department of Computer Science and Electrical Engineering, University of Maryland Baltimore County, MD 21250 (e-mail: [email protected]). Matthew Seligman is with the Laboratory for Telecommunication Sciences (LTS), 8080 Greenmead Road College Park, MD 20742 (e-mail: [email protected]).In this paper, we present a routing algorithm for a class of dynamic networks called the Delay Tolerant Networks (DTNs). The proposed algorithm takes into account the quintessential DTN characteristic namely, intermittent link connectivity. We modify the breadth first search (BFS) algorithm to take into account link state changes and find the quickest route between source and destination nodes. We adopt a message drop policy at intermediate nodes to incorporate storage constraint. We also introduce the idea of time-varying storage domains where all nodes connected for a length of time act as a single storage unit by sharing the aggregated storage capacity of the nodes. We evaluate the routing algorithm with and without storage domain in an extensive simulation. We analyze the performance using metrics such as delivery ratio, incomplete transfers with no routes and dropped messages. The DTN topology dynamics are analyzed by varying: number of nodes generating traffic, link probability, link availability through combinations of downtime/uptime values, storage per node, message size, and traffic. The delay performance of the proposed algorithms is conceptually the same as flooding-based algorithms but without the penalty of multiple copies. More significantly, we show that the Quickest Storage Domain (Quickest SD) algorithm distributes the storage demand across many nodes in the network topology, enabling balanced load and higher network utilization. In fact, we show that for the same level of performance, we can actually cut the storage requirement in half using the Quickest SD algorithm

Communication in Disconnected Ad-hoc Networks Using Message Relay

this paper we explore the possibility of changing the host trajectories in order to facilitate communication. We show how information about the motion of the destination host can be used to determine how messages can be sent to this host by cooperating intermediate hosts. Given an ad-hoc network of mobile computers where the trajectory of each node is approximately known, we would like to develop an algorithm for computing a trajectory for sending a message from host A to host B by recruiting intermediate hosts to help. In our context, recruiting means asking intermediate hosts to change their trajectory in order to complete a routing path between hosts A and B. We would like to minimize the trajectory modifications while getting the message across as fast as possibl

Towards Trustworthy, Efficient and Scalable Distributed Wireless Systems

Advances in wireless technologies have enabled distributed mobile devices to connect with each other to form distributed wireless systems. Due to the absence of infrastructure, distributed wireless systems require node cooperation in multi-hop routing. However, the openness and decentralized nature of distributed wireless systems where each node labors under a resource constraint introduces three challenges: (1) cooperation incentives that effectively encourage nodes to offer services and thwart the intentions of selfish and malicious nodes, (2) cooperation incentives that are efficient to deploy, use and maintain, and (3) routing to efficiently deliver messages with less overhead and lower delay. While most previous cooperation incentive mechanisms rely on either a reputation system or a price system, neither provides sufficiently effective cooperation incentives nor efficient resource consumption. Also, previous routing algorithms are not sufficiently efficient in terms of routing overhead or delay. In this research, we propose mechanisms to improve the trustworthiness, scalability, and efficiency of the distributed wireless systems. Regarding trustworthiness, we study previous cooperation incentives based on game theory models. We then propose an integrated system that combines a reputation system and a price system to leverage the advantages of both methods to provide trustworthy services. Analytical and simulation results show higher performance for the integrated system compared to the other two systems in terms of the effectiveness of the cooperation incentives and detection of selfish nodes. Regarding scalability in a large-scale system, we propose a hierarchical Account-aided Reputation Management system (ARM) to efficiently and effectively provide cooperation incentives with small overhead. To globally collect all node reputation information to accurately calculate node reputation information and detect abnormal reputation information with low overhead, ARM builds a hierarchical locality-aware Distributed Hash Table (DHT) infrastructure for the efficient and integrated operation of both reputation systems and price systems. Based on the DHT infrastructure, ARM can reduce the reputation management overhead in reputation and price systems. We also design a distributed reputation manager auditing protocol to detect a malicious reputation manager. The experimental results show that ARM can detect the uncooperative nodes that gain fraudulent benefits while still being considered as trustworthy in previous reputation and price systems. Also, it can effectively identify misreported, falsified, and conspiratorial information, providing accurate node reputations that truly reflect node behaviors. Regarding an efficient distributed system, we propose a social network and duration utility-based distributed multi-copy routing protocol for delay tolerant networks based on the ARM system. The routing protocol fully exploits node movement patterns in the social network to increase delivery throughput and decrease delivery delay while generating low overhead. The simulation results show that the proposed routing protocol outperforms the epidemic routing and spray and wait routing in terms of higher message delivery throughput, lower message delivery delay, lower message delivery overhead, and higher packet delivery success rate. The three components proposed in this dissertation research improve the trustworthiness, scalability, and efficiency of distributed wireless systems to meet the requirements of diversified distributed wireless applications

Context Aware Service Oriented Computing in Mobile Ad Hoc Networks

These days we witness a major shift towards small, mobile devices, capable of wireless communication. Their communication capabilities enable them to form mobile ad hoc networks and share resources and capabilities. Service Oriented Computing (SOC) is a new emerging paradigm for distributed computing that has evolved from object-oriented and component-oriented computing to enable applications distributed within and across organizational boundaries. Services are autonomous computational elements that can be described, published, discovered, and orchestrated for the purpose of developing applications. The application of the SOC model to mobile devices provides a loosely coupled model for distributed processing in a resource-poor and highly dynamic environment. Cooperation in a mobile ad hoc environment depends on the fundamental capability of hosts to communicate with each other. Peer-to-peer interactions among hosts within communication range allow such interactions but limit the scope of interactions to a local region. Routing algorithms for mobile ad hoc networks extend the scope of interactions to cover all hosts transitively connected over multi-hop routes. Additional contextual information, e.g., knowledge about the movement of hosts in physical space, can help extend the boundaries of interactions beyond the limits of an island of connectivity. To help separate concerns specific to different layers, a coordination model between the routing layer and the SOC layer provides abstractions that mask the details characteristic to the network layer from the distributed computing semantics above. This thesis explores some of the opportunities and challenges raised by applying the SOC paradigm to mobile computing in ad hoc networks. It investigates the implications of disconnections on service advertising and discovery mechanisms. It addresses issues related to code migration in addition to physical host movement. It also investigates some of the security concerns in ad hoc networking service provision. It presents a novel routing algorithm for mobile ad hoc networks and a novel coordination model that addresses space and time explicitly