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Fault tolerance is an essential requirement in the design of protocols and applications for Wireless Sensor Networks (WSNs) since communication and hardware failures are frequent. In this paper we studied the resilience of routing protocols for continuous data dissemination WSNs in face of faults. The main causes of silent failure are presented and classified, including security attacks. An evaluation of routing protocols shows that failures under a large region of the network are the most damaging. We also show how routing protocols may save energy by temporarily turning off disconnected nodes.

This paper proposes a service discovery protocol for discovering and advertising services in a proactive ad hoc network. The protocol we have defined is piggybacked into the OLSR protocol. We define a new message type into OLSR called Service Discovery Message (SDM) for both advertisement and discovery of services. The advertisement frequency and advertisement lifetime are user-controlled parameters, so that they can be modified depending on the user requirements. Each node maintains a service cache to store information about its own services, and the services each device discovers in the network. We also present simulation results of our protocol and show that the service discovery protocol defined here achieves much efficiency in discovering services, while it introduces practically no packet overhead compared to the basic OLSR protocol.

The spatially and temporally diverse nature of ad hoc networks strongly suggests the development of a sophisticated multi protocol network-layer that should enable the ad hoc network’s nodes to dynamically change the routing protocol as networking scenarios demand. In short, the routing protocol is to be considered a system variable. However, the autonomous reconfiguration of such a dependent variable is a non trivial task in the challenging environment of a realistically modelled open, mobile, wireless ad hoc network. We present a novel framework that builds on the social science theory of diffusion of innovations, a theory which describes a flexible decision-making model. This concept enables the development of an autonomous reconfiguration protocol which addresses the constraints imposed by the mobile ad hoc networking system model.

Ad hoc networks are formed by the spontaneous collaboration of wireless nodes when no networking infrastructure is available. When communication to the Internet is desired, one or more nodes must act as gateways for the ad hoc network. In this case, global addressing of ad hoc nodes is required. This article presents a protocol which can be used by an ad hoc node to dynamically select a gateway and create an associated IPv6 global address. The core of our proposal is the concept of . By building and maintaining a forest of logical spanning trees, our proposal ensures that there exists, between a node A and its gateway G, a path of nodes such that each node on this path uses the same prefix P as the node A and its gateway G. This concept results in an organized ad hoc network, in the sense that sub-networks (with respect to prefixes) are automatically created and dynamically maintained when multiple gateways are available. Moreover, the concept of prefix continuity ensures that each sub-network forms a connected graph of nodes which all use an identical prefix. In contrast to traditional wired networks, this feature is not trivial in ad hoc networks.

This paper proposes a new real-time video traffic predictor to meet increasing consumer demand for a high speed high performance wireless broadband network. It analyzes the behaviors and the problems of previous adaptive LMS-type predictors using fixed step size in detail and then proposes an adaptive predictor using variable step size for predicting bandwidth requirement of real-time VBR videos. The proposed adaptive predictor has better ability for handling scene changes and needs not change its parameters for different VBR videos. The simulation shows that the performance of the proposed adaptive predictor is better or near the optimal performance of previous adaptive LMS-type predictors using fixed step size.

In this paper, we present an efficient proactive threshold RSA signature scheme for large-scale ad hoc networks. Our scheme has two advantages. Firstly, the building blocks of the whole scheme are proven secure. Secondly, the whole scheme is efficient.

Many public key infrastructure (PKI) approaches have been proposed in the recent years to secure mobile ad hoc networks (MANETs). We present a new hybrid key management infrastructure, which combines the concepts of PKIs for MANET with trusted-third-party based infrastructures. In our hybrid approach, the underlying PKI is merely used to set-up initial trust of nodes in a MANET, and, thus, generate a random trust graph connecting all the nodes of the MANET. Then, MANET nodes cooperate to securely distribute trust information and symmetric keys to other nodes through the shortest trust path. The hybrid key management infrastructure enables the same security services as a normal PKI yet key establishment and node-to-node authentication, as demonstrated by our performance analysis, is substantially improved in terms of computational and communication efficiency. We also discuss the security level of the hybrid approach.

In this paper, we present and analyze a reputation scheme aiming at reinforcing node cooperation in clustered Mobile Ad hoc Networks with centralized control. The main goal of this scheme is to differentiate between intentional misbehavior and apparent failure to cooperate due to wireless channel conditions or mobility. To this end, a statistical decision method based on the notion of a random walk is employed. Selecting the optimal parameters for this random walk is investigated in the context of time dependent events. Special care has been given to issues such as probability of detection of a misbehaving mobile node, probability of falsely accusing a legitimate node due to nonintentional failures to cooperate and fast detection of misbehaving nodes in the light of time varying behavior of such nodes.

In this paper, we present a novel packet forwarding scheme for wireless ad hoc networks --- “Direction” Forwarding (DFR). Popular routing protocols such as DSDV and AODV use “predecessor” based forwarding, namely, the packet is forwarded to the predecessor on the shortest path from the destination, as advertised during the last update. Predecessor forwarding may fail in large scale networks where the routing update rate must be reduced by the need to maintain link O/H below reasonable levels. However, if nodes are mobile, routing table entries may become “stale” very rapidly. DFR is designed to overcome the “stale” routing table entry problem. When the routing update arrives, the node remembers not only the predecessor delivering the update, but also the update “direction” of arrival. When a packet must be forwarded to destination, it is first forwarded to the node ID found in the routing table. If the node has moved and ID forwarding fails, the packet is “direction” forwarded to the “most promising” node in the indicated direction. At first glance, DFR seems to combine the features of table based routing and geo-routing. However, direction forwarding differs from geo-routing in that the direction is learned from the routing updates, instead of being computed from the destination coordinates. Thus, DFR does not require destination coordinates, a global coordinate system, or a Geo Location Server. In the paper we show the application of DFR to a scalable routing scheme, LANMAR. Through simulation experiments we show that DFR substantially enhances LANMAR performance in large, mobile network scenarios.

Ad-hoc networks that are connected with the infrastructure Internet are named hybrid ad-hoc networks. In 4G communications scenarios, hybrid ad-hoc networks seem to be valuable since they may increase the coverage of wireless networks with minor costs. Using them, terminals out of range of an access point or a base station, or not having adequate network interfaces, may reach the operator’s infrastructure via other terminals. This paper presents a hybrid ad-hoc network solution and a testbed implementation.