A TDMA-based Energy Aware MAC (TEA-MAC) Protocol for Reliable Multicast in WSNs

Multicast in wireless sensor networks (WSNs) is an efficient way to spread the same data to multiple sensor nodes. It becomes more effective due to the broadcast nature of wireless link, where a message transmitted from one source is inherently received by all one-hop receivers, and therefore, there is no need to transmit the message one by one. Reliable multicast in WSNs is desirable for critical tasks like code updation and query based data collection. The erroneous nature of wireless medium coupled with limited resource of sensor nodes, makes the design of reliable multicast protocol a challenging task. In this work, we propose a time division multiple access (TDMA) based energy aware media access and control (TEA-MAC) protocol for reliable multicast in WSNs. The TDMA eliminates collisions, overhearing and idle listening, which are the main sources of reliability degradation and energy consumption. Furthermore, the proposed protocol is parametric in the sense that it can be used to trade-off reliability with energy and delay as per the requirement of the underlying applications. The performance of TEA-MAC has been evaluated by simulating it using Castalia network simulator. Simulation results show that TEA-MAC is able to considerably improve the performance of multicast communication in WSNs.

A Design for Performance Improvement of Clock Synchronization in WSNs using a TDMA-based MAC Protocol

Clock synchronization in a wireless sensor network (WSN) is quite essential as it provides a consistent and a coherent time frame for all the nodes across the network. Typically, clock synchronization is achieved by message passing using a contention-based scheme for media access, like carrier sense multiple access (CSMA). The nodes try to synchronize with each other, by sending synchronization request messages. If many nodes try to send messages simultaneously, contention-based schemes cannot efficiently avoid collisions. In such a situation, there are chances of collisions, and hence, message losses, which, in turn, affects the convergence of the synchronization algorithms. However, the number of collisions can be reduced with a frame based approach like time division multiple access (TDMA) for message passing. In this paper, we propose a design to utilize TDMA-based media access and control (MAC) protocol for the performance improvement of clock synchronization protocols. The basic idea is to use TDMA-based transmissions when the degree of synchronization improves among the sensor nodes during the execution of the clock synchronization algorithm. The design significantly reduces the collisions among the synchronization protocol messages. We have simulated the proposed protocol in Castalia network simulator. The simulation results show that the proposed protocol significantly reduces the time required for synchronization and also improves the accuracy of the synchronization algorithm.

Efficient Protocol for Authenticated Email Search

Executing authenticated computation on outsourced data is currently an area of major interest in cryptology. Large databases are being outsourced to untrusted servers without appreciable verification mechanisms. As adversarial server could produce erroneous output, clients should not trust the server's response blindly. Primitive set operations like union, set difference, intersection etc. can be invoked on outsourced data in different concrete settings and should be verifiable by the client. One such interesting adaptation is to authenticate email search result where the untrusted mail server has to provide a proof along with the search result. Recently Ohrimenko et al. proposed a scheme for authenticating email search. We suggest significant improvements over their proposal in terms of client computation and communication resources by properly recasting it in two-party settings. In contrast to Ohrimenko et al. we are able to make the number of bilinear pairing evaluation, the costliest operation in verification procedure, independent of the result set cardinality for union operation. We also provide an analytical comparison of our scheme with their proposal which is further corroborated through experiments.

Performance evaluation of mobile agent based resource management protocol for MANETs

The nodes with dynamicity, and management without administrator are key features of mobile ad hoc networks (1VIANETs). Increasing resource requirements of nodes running different applications, scarcity of resources, and node mobility in MANETs are the important issues to be considered in allocation of resources. Moreover, management of limited resources for optimal allocation is a crucial task. In our proposed work we discuss a design of resource allocation protocol and its performance evaluation. The proposed protocol uses both static and mobile agents. The protocol does the distribution and parallelization of message propagation (mobile agent with information) in an efficient way to achieve scalability and speed up message delivery to the nodes in the sectors of the zones of a MANET. The protocol functionality has been simulated using Java Agent Development Environment (JADE) Framework for agent generation, migration and communication. A mobile agent migrates from central resource rich node with message and navigate autonomously in the zone of network until the boundary node. With the performance evaluation, it has been concluded that the proposed protocol consumes much less time to allocate the required resources to the nodes under requirement, utilize less network resources and increase the network scalability. (C) 2015 Elsevier B.V. All rights reserved.

Hacia una ética de la responsabilidad: Derrida y el otro “por venir” en Lévinas

Resumen: La tesis del trabajo es que la deconstrucción entraña en sí misma una actitud ética, y que ésta radica intrínsecamente en su apertura al otro y en la responsabilidad frente a ese otro. Para ello, se intenta en primer lugar una elucidación del concepto, caracterizándola como un protocolo de lectura compuesto de dos fases: des-sedimentación y reinscripción, siendo este último momento el que la identifica como una lectura singular y no universalizable. Posteriormente, a través de las nociones de “sujeto” y “alteridad del texto”, se muestra cómo las bases de la ética deconstructiva giran en torno a las nociones de “yo” y “otro”, conceptos que Derrida, como se demuestra, toma de Lévinas. La instancia ética es la apertura al otro, que se verifica por la responsabilidad que supone concebir al otro como aquello incapaz de apropiación. Dicha responsabilidad configura la aporía ética de lo general-particular, al concebirse como la posibilidad imposible de una opción general que es al mismo tiempo una decisión personal o singular, o, en otros términos, la indecidibilidad entre la norma general y la decisión concreta, que es a su vez la tensión entre “justicia”, “hospitalidad” y “negociación”. Lo anterior demuestra que el acto ético (o acto deconstructivo) tiene la misma estructura de la différance, imbricada siempre en la iteración del significante.

Biological surveys of five southern artificial reefs: Oceanside #1, Oceanside #2, Carlsbad, Pacific Beach, and Mission Bay

(Document pdf contains 19 pages)

A report of biological observations at Oceanside #1 and #2 artificial reefs, Carlsbad artificial reef, Pacific Beach artificial reef, and Mission Bay Park artificial reef

(Document pdf contains 22 pages)

Développement des méthodes de stabilisation pour la conception des circuits hyperfréquences : application à l'optimisation d'un amplificateur de puissance spatial

209 p. : graf.