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The highly successful architecture and protocols of today΄s Internet may operate poorly in environments characterized by very long delay paths and frequent network partitions. Delay Tolerant Networks (DTNs) are emerging solutions to networks that experience frequent network partitions and large end-to-end delays. In this paper, we study how to provide high-performance routing technique in DTNs. We develop a multicasting mechanism based on requirement of path discovery and overall situation awareness of link availability to address the challenges of opportunistic link connectivity in DTNs. Simulation results show that this method can achieve a better message delivery ratio than existing approaches, e.g. DTBR (a dynamic tree-based routing), with similar delay performance. ERBR approach also achieves better efficiency performance when the probability of link unavailability is high and the duration of link downtime is large. [ABSTRACT FROM AUTHOR]

The existing Ad-Hoc On demand Routing Protocol (AODV) for MANETs is more suitable for highly dynamic networks, but in generally ad-hoc networks many of the situations topology changes slowly. In this scenario finding the shortest path using AODV making use of RREQ and RREP is quite over head and consumes much of the existing bandwidth. In this paper we have proposed neighbor matrix approach to find the shortest path in static Ad-hoc Networks. In the proposed approach whenever a node wants to find path to the destination it evaluate the neighbour matrix of the existing ad-hoc network which is helpful in finding the path to the destination using incremental neighbour searching till the destination has reached. This approach avoids the frequently sending Route Request Phase of existing AODV reactive routing protocol for MANETs. The Proposed algorithm uses the neighbour matrix more effectively and evaluates the path. [ABSTRACT FROM AUTHOR]

Ad-hoc networks, mobile devices communicate via wireless links without the aid of any fixed networking infrastructure. These devices must be able to discover services dynamically and share them safely, taking into account ad-hoc networks requirements such as limited processing and communication power, decentralized management, and dynamic network topology, among others. Legacy solutions fail in addressing these requirements. In this paper, we propose a service discovery protocol with security features, the Secure Pervasive Discovery Protocol. SPDP is a fully distributed protocol in which services offered by devices can be discovered by others, without a central server. It is based on an anarchy trust model, which provides location of trusted services, as well as protection of confidential information, secure communications, or access control. [ABSTRACT FROM AUTHOR]

In this paper, a topology-configurable method for forming a Bluetooth scatternet is proposed. The heuristic method describes two mechanisms, the const-hop algorithm and the variant-hop algorithm. With a constant k parameter, the const-hop algorithm propagates k in its downstream direction to determine roots and constructs their associated subnets. With a constant k, a counter variable v, and a return variable r as parameters, the variant-hop algorithm generates appropriate roots locally and evenly configures the subnet size.A computer simulation shows that the proposed method achieves good network scalability and generates an efficient scatternet configuration for a Bluetooth multihop network. [ABSTRACT FROM AUTHOR]

Social networks such as Facebook and Secondlife are popular. Wireless devices abound from affluent countries to developing countries. Social networks need wide area Internet support. Wireless interfaces offer ad hoc networking capability, without the need for infrastructure support. Web on Demand (WoD) aims to bridge the gap between ad hoc social networks (people in close proximity with shared interests) and ad hoc networking. A key requirement for WoD is transparent connection management. This paper makes three contributions: First, an abstraction called VirtualConnection for transparent connection creation and migration, with socket-like API; second, an implementation on iPAQs (Windows Mobile) as a user level library, and proof of efficacy of using this abstraction for realizing WoD; third, evaluations to establish the performance of this abstraction. In particular, we show the performance degradation due to virtualizing the connection is negligible. [ABSTRACT FROM AUTHOR]

Wireless Ad-hoc networks are distributed systems that often reside in error-prone environments. Self-stabilization lets the system recover autonomously from an arbitrary state, making the system recover from errors and temporarily broken assumptions. Clustering nodes within ad-hoc networks can help in many ways like forming backbones, facilitating routing, improving scaling, aggregating information and saving power. A (k,r)-clustering assigns cluster heads so that exists k cluster heads within r communication hops for all nodes in the network while trying to minimize the total number of cluster heads.We present the first self-stabilizing distributed (k,r)-clustering algorithm. The algorithm uses synchronous communication rounds and uses multiple paths to different cluster heads for providing improved security, availability and fault tolerance. From any starting configuration the algorithm quickly assigns enough cluster heads and stabilizes towards a local minimum using a randomized scheme. [ABSTRACT FROM AUTHOR]

Spectrum sensing is a distinct feature of cognitive ad-hoc nodes that have the ability to opportunistically use vacant spectrum bands for its own communication purposes. Possible cooperation among the nodes may prove vital for increasing network performance. It yields the cognitive ad-hoc nodes to exchange relevant environmental and context information in order to enhance its own networking experience. This paper overviews the approaches, techniques and strategies for cooperative spectrum sensing and gives a practical example of a realized testbed implementation in an ad-hoc environment. [ABSTRACT FROM AUTHOR]

This paper proposes a vehicle-to-vehicle (V2V) communication protocol which makes it possible to discover and share traffic status information in a novel, efficient and comprehensive way. The protocol is specifically designed to work in an environment without infrastructure where all the vehicles (nodes) can talk to each other (ad-hoc network) and collaboratively generate new knowledge relevant to the traffic conditions existing at that moment in an urban environment. The nature of such a network demands self-configuration and autonomous behaviour. The protocol adheres to these principles and makes it possible for the nodes to initiate discovery and determine the location of areas where specific traffic conditions apply. The proposed ˵Single Ripple″ algorithm determines these areas by only involving vehicles with the desired conditions and their neighbours. The algorithm imposes only a minimal load onto the wireless network. [ABSTRACT FROM AUTHOR]

In this paper, a novel dynamic contention window control scheme is presented to improve the performance and energy efficiency of IEEE 802.11-based CSMA/CA DCF wireless networks operating in ad-hoc mode. The number of competing nodes in physical carrier sense systems has a major influence on the probability of collisions and a subsequent impact on DCF performance and on the energy consumed. A new cross-layer approach to alleviating this problem is developed, which attempts to improve the performance and energy efficiency by controlling the contention window size in the MAC layer according to the number of competing nodes, and the length of the MPDU (MAC Protocol Data Unit) payload according to the physical channel condition in the PHY layer. [ABSTRACT FROM AUTHOR]

In wireless ad-hoc networks, all nodes need to have functions able to authenticate each other and so it is critical to know the trustworthiness of each node in such environments. This paper proposes an authentication system for ad-hoc networks, based on a clustering and trust model. Firstly, methods of solving authentication problems, which occur in ad-hoc networks, are discussed. Next, fuzzy logic inference is introduced, which is used as a trust evaluation method for each node and provides both local and global trust values. The reputation is used in the calculation of the trust value. Using the trust value of a trustor, a more sophisticated trust value can be computed. If a node moves from one cluster to another, the trust level of the node is determined by the certificate issued by the previous introducers. In addition, it is demonstrated that the proposed model can monitor and isolate malicious nodes in order to provide enhancements to the network΄s overall authentication rate. [ABSTRACT FROM AUTHOR]

In concept-addressable messaging, network nodes are both described and addressed by concepts derived from an ontology domain model. The paper presents a routing protocol for the concept-addressable messaging in mobile ad-hoc networks. The domain model is a taxonomy, and the address is any concept from the taxonomy. The protocol uses restricted flooding (narrowcasting) to deliver concept-addressed messages. To that end, nodes΄ conceptual descriptions are proactively spread with Hello messages. If there is not enough room in the Hello message, selected descriptions are moved to a higher abstraction level and merged. The protocol is a single layer solution (not an overlay). Preliminary ns2-based performance results are provided. [ABSTRACT FROM AUTHOR]

In this paper, we propose a secure spontaneous ad-hoc network to grant the access of the users to surf the Web. The paper shows the description of our proposal, the procedure of the nodes involved in the system and the designed messages. We also validate the success of our proposal through several simulations and comparisons with a regular architecture. The proposal has been developed with the main objective of improving the communication and integration between different study centers of low resource communities. [ABSTRACT FROM AUTHOR]

We present our contribution in projects related to ad-hoc networking using different routing protocols and hardware platforms, showing our results and new solutions regarding topology control and routing protocols. We mainly focus on our work in the GUARDIANS EU-project, where as a main disaster scenario a large industrial warehouse on fire is assumed. The paper presents the simulation results for the routing protocols ACR, DSR and EDSR, as well as the implementation of down-scaled demos for supporting the autonomous team of robots as well as the human squad team with robust communication coverage. Various hardware platforms were used in the demos for distance measurement, based on laser range finder and radio communication with time of flight analysis. [ABSTRACT FROM AUTHOR]

This paper presents a work in progress which deals with the problem of node misbehaviour in ad-hoc networks. A realistic approach is used to determine the impact of contention window manipulation and RTS/CTS cheating. It is explained why IEEE 802.11e ad-hoc networks are more prone to misbehaviour. The paper presents simulation results related to the mentioned types of misbehaviour. The analysis is performed for several distinct scenarios, which yields novel results. It is shown under which conditions a misbehaving node can gain a significant advantage over well-behaving nodes. The limitations of the IEEE 802.11e standard in providing QoS in the presence of misbehaving nodes is also presented. [ABSTRACT FROM AUTHOR]

Consider a group of m stations with fixed positions in the plane and a group of n mobile robots, called relays, aiming at building a communication network between the stations consisting of as few relays as possible. We present two strategies for dimensionless, identical (anonymous), oblivious and disoriented relays with limited viewing radius for constructing such a network. These strategies resemble natural strategies of swarms for maintaining formations. A relay does not communicate with others, its decision – whether to remove itself from the system, or where to move – consists only of the relative positions of its neighbors within its viewing radius. We provide a theoretical analysis of worst-case scenarios and upper and lower bounds for the number of relays used by the strategies. In addition, we show some preliminary experimental results. [ABSTRACT FROM AUTHOR]

Emerging pervasive computing technologies such as sensor networks and RFID tags can be embedded in our everyday environment to digitally store and elaborate a variety of information. By having application agents access in a dynamic and wireless way such distributed information, it is possible to enforce a notable degree of context-awareness in applications, and increase the capabilities of interacting with the physical world. In particular, biologically inspired field-based data structures such as gradients and pheromones are suitable to represent information in a variety of pervasive computing applications. This paper discusses how both sensor networks and RFID tags can be used to that purpose, outlining the respective advantages and drawbacks of these technologies. [ABSTRACT FROM AUTHOR]

The integration of mobile ad hoc networks into IP-based access networks demands the presence of a gateway which is responsible for propagating some configuration parameters by means of Modified Router Advertisement (MRA) messages. This function may be accomplished on demand by the mobile nodes (reactively), periodically activated by the gateway (proactively) or by combining the two approaches. In the proactive mechanisms, the interval of emission of the MRA messages (T) may significantly affect the network performance. The optimum value for T depends on the network conditions such as the position of the sources, the mobility of nodes, etc. Therefore, an autonomous and adaptive technique to dynamically configure T is strongly recommended. In this sense, a new adaptive gateway discovery mechanism is proposed in this paper. The adaptation is achieved by a control system which has been conveniently configured by means of an analytical model. Simulation results show that the proposed adaptive mechanism improves the conventional proactive schemes. [ABSTRACT FROM AUTHOR]

The existence of selfish nodes, who do not cooperate in routing and forwarding, is one of the most critical problems for the applicability of Mobile Ad-hoc NETworks (MANETs). In this paper we propose several novel currency-based methods for stimulating cooperation among nodes of a MANET. In particular, the proposed protocols allow improving different aspects of previous schemes based on virtual currency thanks to the incorporation of the concept of credit that will allow broke nodes to use the network while they have not a selfish behaviour. A complete analysis of simulations leads to several conclusions that establish the improvement of the proposal with respect to previous schemes. [ABSTRACT FROM AUTHOR]

An ad hoc network is composed by autonomous, potentially mobile, wireless nodes that operate without the benefit of any existing infrastructure. Each node is can move arbitrary and carries out self-administration and self-organization. For this reason, there are cases in which non-planned route΄s construction may lead to a decline of the network performance. In this paper, we present a new routing protocol that uses the load balancing and multi-path solution to send data with a probabilistic dispersion. In this research, the total load on a route is evaluated based on the relay node΄s queue size. Simulation experiments have been made to compare some of the existing protocols with the proposed routing protocol. We have shown by simulations results that our proposed solution efficiently disperses the load and improves the network performance. [ABSTRACT FROM AUTHOR]

The authors have proposed a music delivery system JAMS (JAMais vu System), which uses ad-hoc networks with mobile devices for the localization services. In this paper, they focus on a cache management scheme for JAMS to deliver music files efficiently. The proposed scheme makes it possible to manage cache files robustly by using adaptive cache delivery according to each node request. In addition, the authors conduct a simulation experiment and obtain access failure ratio of music files under various system conditions. The simulation results indicate that the proposed scheme is suitable for the system using localization services. [ABSTRACT FROM AUTHOR]

This paper proposes a Media Access Control protocol,called CT-MAC, for ad-hoc wireless sensor networks. It is a contention-based TDMA scheme, which assimilates the valuable design philosophies of CSMA and TDMA while offsetting their weaknesses. Inspired by S-MAC[1], CT-MAC proposes a novel conception of contention/doze and communication/dormancy duty cycle. Unlike S-MAC where the durations of each cycle are fixed, CT-MAC makes these durations self-adaptive for energy efficiency. More importantly, CT-MAC originally adopts the protocol interference model to contend the noninterference channels for each time-slot, and extends the conventional IEEE 801.11 RTS-CTS scheme with stronger functions to successfully solve the exposed terminal problem, which is not well addressed before. We believe that the initial high overhead in the contention period would be eventually compensated by the improved throughput and energy efficiency subsequently. Simulations are performed among CT-MAC, S-MAC and simplified 802.11 DCF to demonstrate the efficiency and effectiveness of the proposed CT-MAC. [ABSTRACT FROM AUTHOR]

A random geometric graph ]> is obtained by spreading n points uniformly at random in a unit square, and by associating a vertex to each point and an edge to each pair of points at Euclidian distance at most r. Such graphs are extensively used to model wireless ad-hoc networks, and in particular sensor networks. It is well known that, over a critical value of r, the graph is connected with high probability. In this paper we study the robustness of the connectivity of random geometric graphs in the supercritical phase, under deletion of edges. In particular, we show that, for a sufficiently large r, any cut which separates two components of Θ(n) vertices each contains Ώ(n2r3) edges with high probability. We also present a simple algorithm that, again with high probability, computes one such cut of size O(n2r3). From these two results we derive a constant expected approximation algorithm for the β-balanced cut problem on random geometric graphs: find an edge cut of minimum size whose two sides contain at least βn vertices each. [ABSTRACT FROM AUTHOR]