Catálogo de publicaciones - libros

Broadcasting is a basic network communication task, where a message initially held by a source node has to be disseminated to all other nodes in the network. Fast algorithms for broadcasting in radio networks have been studied in a wide variety of different models and under different requirements. Some of the main parameters giving rise to the different variants of the problem are the accessibility of knowledge about the network topology, the availability of collision detection mechanisms, the wake-up mode, the topology classes considered, and the use of randomness. The paper reviews the literature on time-efficient broadcasting algorithms for radio networks under a variety of models and assumptions.

Bluetooth is an emerging standard in short range, low cost and low power wireless networks. MAC is a generic polling based protocol, where a central Bluetooth unit (master) determines channel access to all other nodes (slaves) in the network (piconet). An important problem in Bluetooth is the design of efficient scheduling protocols. This paper proposes a polling policy that aims to achieve increased system throughput and reduced packet delays while providing reasonably good fairness among all traffic flows in a Bluetooth Piconet. We present an extensive set of simulation results and performance comparisons with two important existing algorithms. Our results indicate that our proposed scheduling algorithm outperforms the Round Robin scheduling algorithm by more than 40% in all cases tried. Our study also confirms that our proposed policy achieves higher throughput and lower packet delays with reasonable fairness among all the connections.

A large number of sensors are usually deployed around some discrete targets in wireless sensor networks for target surveillance purpose. In such networks, clustering is beneficial not only to network management and data aggregation, but also to the target coverage issues. This paper builds a target coverage relation model for target surveillance networks. Based on this model, we abstract the clustering as finding the minimum K-hop dominating set which is proved to be NP complete. Then, we propose a distributed energy-efficient target-oriented clustering protocol (EETO). EETO partitions the network into multiple connected sub-branches based on the corresponding target-oriented relation graph. Each sub-branch is a cluster, where the cluster members are all the K-hop coverage neighbors of the cluster head. EETO groups the sensors which cover the same target set into one cluster. Therefore, related data can be aggregated timely and completely at the cluster head. The message overhead of EETO is only (1), which is scalable. Detailed simulation results show that EETO reduces energy consumption, improves load balancing and prolongs the coverage lifetime of the network.

Several media access control (MAC) protocols proposed for wireless sensor networks assume nodes to be stationary. This can lead to poor network performance, as well as fast depletion of energy in systems where nodes are mobile. This paper presents several results for TDMA-based MAC protocol for mobile sensor networks, and also introduces a novel mobility-aware TDMA-based MAC protocol for mobile sensor networks. The protocol works by first splitting a given round into a control part, and a data part. The control part is used to manage mobility, whereas nodes transmit messages in the data part. In the data part, some slots are reserved for mobile nodes. We show that the protocol ensures collision-freedom in the data part of a schedule.

This paper considers the problem of unicasting in wireless ad hoc networks. Unicasting is the problem of finding a route between a source and a destination and forwarding the message from the source to the destination. In theory, models that have been used oversimplify the problem of route discovery in ad hoc networks. The achievement of this paper is threefold. First we use a more general model in which nodes can have different transmission and interference ranges and we present a new routing algorithm for wireless ad hoc networks that has several nice features. We then combine our algorithm with that of known greedy algorithms to arrive at an average case efficient routing algorithm in the situation that GPS information is available. Finally we show how to schedule unicast traffic between a set of source-destination pairs by providing a proper vertex coloring of the nodes in the wireless ad hoc network. Our coloring algorithm achieves a ()–coloring that is locally distinct within the 2-hop neighborhood of any node.

In this paper, we describe a Structured Mesh Overlay Network (SMON) based on a Distributed Hash Table (DHT) technique on top of a proactive routing protocol, Optimized Link State Routing (OLSR). SMON is a P2P cross-layer overlay network based on concept of CrossROAD. CrossROAD uses a pure flooding technique to form and maintain an overlay network. The broadcast mechanism has a negative effect on bandwidth usage of the network. On the other hand, we introduce a new algorithm for overlay formation and maintenance in order to reduce a number of overlay broadcast messages. The simulation results show that SMON reduces the number of overlay control overhead around 95% as compared to CrossROAD, while it maintains high query success ratio and low query delay.

Clustering has evolved as an important research topic in MANETs as it improves the system performance of large MANETs. Most existing schemes have large overhead associated with cluster formation and cluster maintenance. They also trigger reclustering periodically. This renders these schemes non-scalable. In this paper, we present a clustering scheme that minimizes message overhead for cluster formation and maintenance. We do not require reclustering as clusters in our scheme do not degenerate into single node clusters over time. We simulated our clustering scheme in . The results show that the number of clusters formed are in proportion to the number of nodes in the MANET. We also show that our scheme is resilient to variations in mobility. This shows that our scheme is scalable as well as adaptable.

In this paper, we propose a key establishment scheme suitable for mobile sensor networks for establishing keys between sensor nodes in an environment where the sensor nodes are highly mobile. Our analysis and simulation results show that our scheme has high network connectivity as well as higher security against sensor node captures compared to those for the existing schemes. Moreover, our scheme supports efficiently addition of new nodes after initial deployment and also works for any deployment topology.

Data sharing and information exchange have grown exponentially with the information explosion in the last few years. More and more data are being shared among different types of users residing in different places, performing different kinds of tasks for different kinds of applications. Privacy control is a major issue for today’s data managers. In this research, we presented two models to solve the information leakage problem occurring during query aggregation. The first model is the base model that uses a single inference dispersion value for each user where as the second model uses multiple inference dispersion values for each user with a view to provide more accessibility.

The attractiveness of the wireless ad hoc networks lies in the fact that these networks are self-organized: the hosts constituting the networks can communicate with each other without reliance on any centralized or specified entities such as base stations or access points. With these networks finding more applications, the need for adequate security mechanism is increasingly becoming important. Key management is an essential cryptographic primitive upon which other security protocols are built. However, most of the existing key management schemes are not feasible in ad hoc networks because public key infrastructures with a centralized certification authority are hard to deploy there. In this paper, we propose and evaluate a mechanism of distributed certification authority based on threshold cryptography that is suited for wireless ad hoc networks. In the proposed scheme, a collection of nodes acts as the certificate authority and provides the certification service. The feasibility of the proposed scheme is verified by simulation. The results show the effectiveness of the scheme.