Earticle

It is important to have continuous connectivity in a wireless sensor network after it is deployed in a hostile environment. However, such networks are constrained by the low userto-node ratio, limited energy and bandwidth resources, entities that are usually mobile, networks without fixed infrastructure and frequent failure due to problems of energy, vulnerability to attack, etc. To address these difficulties, there is a need for wireless sensor networks to be self-organizing and self-configuring so as to improve performance, increase energy efficiency, save resources and reduce data transmission. In this paper, we present a method for monitoring, maintaining and repairing the communication network of a dynamic mobile wireless sensor network, so that network connectivity is continuously available and provides fault tolerance. Specifically, we propose an algorithm for the detection and surveillance of articulation points in graph connectivity, including an algorithm for -network auto-organization in the event that this occurs.

The Hierarchical Mobile IPv6 (HMIPv6) has been proposed by IETF to reduce registration control signaling. It separates micro-mobility from macro-mobility with the help of an intermediate mobility agent, called the mobility anchor point (MAP), and exploits a Mobile Node’s (MN’s) spatial locality. However, in HMIPv6, the handover process reveals numerous problems manifested by the latency in configuring a new care of address and confirmation scheme called duplicate address detection. In this paper, we proposes an Efficient Scheme Fast Handover over HMIPv6 networks. The MIPv6 mobility could be more enhanced by combining FMIPv6 with HMIPv6, in which MIPv6 is benefited from all the advantages of the respective schemes. In previous work an additional benefit by combining FMIPv6 with HMIPv6 is that the overall handover latency in HMIPv6 will be more reduced since in HMIPv6 the MN sends a location update with the with NAP, rather than the HA and CN that are typically further way. An analytical study compares the handover latency of different IP mobility management Schemes, considering the different approaches of HMIPv6 and ES-FHMIPv6. This document describes the enhanced scheme of FHMIPv6 than can reduce the latency handover of message from a certain access router to another router. The ESF-HMIPv6 is designed to be efficient with the data transport feature; we include a dual buffer in Access Point (AP) which stores the received message from Previous Access Router (PAR), the main purpose of the design scheme is to minimize the handover latency time of message transmission.

In the present paper, we have investigated two characteristics of three different waveguides employed in arrayed waveguide grating (AWG) in passive optical networks (PON) where rates of variations are processed. Both the thermal and the spectral effects are taken into account. The waveguides are made of Lithium Niobate, germaniadoped silica, and Polymethyl metha acrylate (PMMA) polymer. The thermal and spectral sensitivities of optical devices are also analyzed. In general, both qualitative and quantitative analysis of the temporal and spectral responses of AWG and sensitivity are parametrically processed over wide ranges of the set of affecting parameters.

We consider a single server queue in which multi-class customers arrive ac-cording to Poisson process and service times are exponentially distributed. The server works following a gate mechanism in which arriving customers do not en-ter service immediately and wait to form a batch. This batch of customers get service after the completion of service to the previous batch. We also assume that after the service time of all customers, a customer of one class may join the next batch to get the service of another or the same class. The number of customers in a batch, duration of service time to a batch and the probability for the busy period to end in ¯nite time are obtained. Elegant expressions are obtained when there are only two classes. These results are extended to multi-class customers in a varying environment. The connections between queues and branching processes is exploited to obtain these results. Numerical illustrations are presented.

A Mobile Ad hoc Network (MANET) is an autonomous system of mobile nodes with routing capabilities connected by wireless links, the union of which forms a communication network modeled in the form of an arbitrary graph. The vision of Mobile Ad Hoc Network (MANET) is wireless internet, where users can move anywhere anytime and still remaining connected with the rest of the world. The main challenges in MANET are reliability, bandwidth and battery power. The network has unpredictable characteristics such as its topology, signal strengths fluctuates with environment and time, communication routes breaks and new ones are formed dynamically. In this context, communication algorithms and protocols should have very light in computational and storage needs in order to conserve energy and bandwidth. Broadcasting is the process in which a source node sends a message to all other nodes in MANET. Network wide broadcasting in Mobile Ad Hoc Network provides important control and route establishment functionality for a number of unicast and multicast protocols. Broadcasting in MANET poses more challenges than in wired networks due to node mobility and scarce system resources. Broadcasting a packet to the entire network is a basic operation and has extensive applications in mobile ad hoc networks (MANETs). This paper presents an overview of the broadcasting techniques in mobile ad hoc networks, and simulating the simple Flooding algorithm and Probability based flooding algorithm using NS2 simulation.

The access control system is a very important step in the implementation of the security policy of an information system. Access control checks what a user can do directly, as well as what programs executing on behalf of the users are allowed to do. In this way the access control seeks to prevent the activities which will be able to endanger the safety of the system. The aim of this paper is to try to model the access control system in the operating systems of the type UNIX. The modeling will be based on a combining of the UNIX access control system, namely Super-User model, and RBAC1 model [1, 11, 12]. In order to get a model nearest possible at reality, we will use the notion of roles and the privileges graph to build our graph. The properties of graph theory well are used in order to evaluate the stability and the robustness of our model.