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.

服务发现机制的设计与实现

随着网络的普及和各类设备的智能化、移动化，普遍互联和动态移动构成了当前计算环境的主要特征。服务发现协议帮助用户在各类分布式环境下找到所需的服务，即，存在于网络中，可以被发布、发现和使用的任何软件或硬件资源。服务发现是网络分布式环境下进行信息共享、数据集成、流程协作的前提，更是普适计算环境的基础设施。 学术界和工业界在服务发现方面已经进行了不少的探索和研究，但是目前Internet/Intranet、MANET的规模越来越大，网络中的服务种类与数量剧增，适用于上述网络环境的服务发现系统应该具备高效、准确、低通信量和规模可伸缩的特性，另外，由于网络的动态性，系统需要具有一定的容错能力。针对于上述网络环境的服务发现研究相对较少且不成熟，还存在较多问题需要解决。 本文以服务描述模型SDMDHD为基础，针对于稠密部署的大规模MANET环境，设计了相应的服务发现机制，并在SCN4M（Service CatalogNet for MANET）系统中实现了该发现机制；针对于服务种类丰富、数量很大的大规模Internet/Intranet环境，设计了相应的服务发现机制，并将该机制实现在SCN4I（Service CatalogNet for Internet/Intranet）系统中。两个系统均对服务信息进行了摘要，并以服务信息的摘要为基础构建了分布式后缀树索引机制，它确保了高效、准确、低通信量的服务发现过程，从而使得系统具备规模可伸缩性。以索引机制为基础，两个系统提供了基于协作的选播/多播服务发现策略。针对网络动态性，两个系统均采用分布式信息冗余存储策略，一定程度上解决了节点失效引发的信息丢失问题。另外，SCN4M实现了基于内容寻址的应用层路由方案，SCN4I实现了虚拟环状空间中基于内容的消息转发机制，为解决节点动态加入和离开问题奠定了基础。

移动自组网中基于AODV的节能路由协议研究

作为一种无需预设设备支持的无线移动网络，移动自组网的研究越来越多地得到人们的关注，特别是对网络性能有重要影响的路由协议的研究。由于移动自组网中的节点采用电池一类的可耗尽能源来提供电源，而且每个节点既是主机又是路由器，很容易因某个节点能量耗完而导致网络分裂。同时由于移动自组网中的节点可以任意的运动，导致网络中传输路径的频繁断裂，大量的重路由操作降低了网络的运行性能。本文在AODV路由算法的基础上，综合考虑节点的运动特性和能量受限特性，提出了三种新的节能路由策略。本文首先总结了目前移动自组网中网络层的一些节能路由协议，并比较分析了它们的优缺点。接着本文在AODV路由算法的基础上，综合考虑节点剩余电池能量和跳数，提出了一种新的节能路由策略。仿真结果显示该策略改善了网络性能，延长了网络的生存时间。然后本文基于按需路由协议AODV，通过预测链路保持连接的时间和节点的生存时间，提出了一种在路由发现和路由维护两个阶段都带移动预测的路由策略。并通过模拟结果说明了该策略能有效的提高数据传送率，减少链路断裂个数。最后针对第二种改进中的不足之处，本文对其进行了进一步的改进与优化，设计了一种基于路径稳定度预测的AODV路由协议。该协议首先基于链路保持连接时间的预测，然后通过路径稳定度的预测，选择一条在t0时刻存在并可保持至t0+ 时刻的最稳定路径进行数据传输。我们也通过模拟结果论证了该算法的有效性。

Application-based workload model for wireless sensor node computing platforms

Wireless sensor node platforms are very diversified and very constrained, particularly in power consumption. When choosing or sizing a platform for a given application, it is necessary to be able to evaluate in an early design stage the impact of those choices. Applied to the computing platform implemented on the sensor node, it requires a good understanding of the workload it must perform. Nevertheless, this workload is highly application-dependent. It depends on the data sampling frequency together with application-specific data processing and management. It is thus necessary to have a model that can represent the workload of applications with various needs and characteristics. In this paper, we propose a workload model for wireless sensor node computing platforms. This model is based on a synthetic application that models the different computational tasks that the computing platform will perform to process sensor data. It allows to model the workload of various different applications by tuning data sampling rate and processing. A case study is performed by modeling different applications and by showing how it can be used for workload characterization. © 2011 IEEE.

Mutations in the H, F, or M proteins can facilitate resistance of measles virus to neutralizing human anti-MV sera

Although there is currently no evidence of emerging strains of measles virus (MV) that can resist neutralization by the anti-MV antibodies present in vaccinees, certain mutations in circulating wt MV strains appear to reduce the efficacy of these antibodies. Moreover, it has been hypothesized that resistance to neutralization by such antibodies could allow MV to persist. In this study, we use a novel in vitro system to determine the molecular basis of MV's resistance to neutralization. We find that both wild-type and laboratory strain MV variants that escape neutralization by anti-MV polyclonal sera possess multiple mutations in their H, F, and M proteins. Cytometric analysis of cells expressing viral escape mutants possessing minimal mutations and their plasmid-expressed H, F, and M proteins indicates that immune resistance is due to particular mutations that can occur in any of these three proteins that affect at distance, rather than directly, the native conformation of the MV-H globular head and hence its epitopes. A high percentage of the escape mutants contain mutations found in cases of Subacute Sclerosing Panencephalitis (SSPE) and our results could potentially shed light on the pathogenesis of this rare fatal disease.

Novel multicast protocols in ad-hoc networks

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

CACHE REPLACEMENT STRATEGIES FOR MOBILE DATA CACHING.

Data caching is an important technique in mobile computing environments for improving data availability and access latencies particularly because these computing environments are characterized by narrow bandwidth wireless links and frequent disconnections. Cache replacement policy plays a vital role to improve the performance in a cached mobile environment, since the amount of data stored in a client cache is small. In this paper we reviewed some of the well known cache replacement policies proposed for mobile data caches. We made a comparison between these policies after classifying them based on the criteria used for evicting documents. In addition, this paper suggests some alternative techniques for cache replacement

Cooperative caching techniques for mobile ad hoc networks

Data caching can remarkably improve the efficiency of information access in a wireless ad hoc network by reducing the access latency and bandwidth usage. The cache placement problem minimizes total data access cost in ad hoc networks with multiple data items. The ad hoc networks are multi hop networks without a central base station and are resource constrained in terms of channel bandwidth and battery power. By data caching the communication cost can be reduced in terms of bandwidth as well as battery energy. As the network node has limited memory the problem of cache placement is a vital issue. This paper attempts to study the existing cooperative caching techniques and their suitability in mobile ad hoc networks.

A Novel Cache Resolution Technique For Cooperative Caching In Wireless Mobile Networks

Cooperative caching is used in mobile ad hoc networks to reduce the latency perceived by the mobile clients while retrieving data and to reduce the traffic load in the network. Caching also increases the availability of data due to server disconnections. The implementation of a cooperative caching technique essentially involves four major design considerations (i) cache placement and resolution, which decides where to place and how to locate the cached data (ii) Cache admission control which decides the data to be cached (iii) Cache replacement which makes the replacement decision when the cache is full and (iv) consistency maintenance, i.e. maintaining consistency between the data in server and cache. In this paper we propose an effective cache resolution technique, which reduces the number of messages flooded in to the network to find the requested data. The experimental results gives a promising result based on the metrics of studies.

Performance improvement of multiple Connections in AODV with the concern of Node bandwidth

Mobile Ad-hoc Networks (MANETS) consists of a collection of mobile nodes without having a central coordination. In MANET, node mobility and dynamic topology play an important role in the performance. MANET provide a solution for network connection at anywhere and at any time. The major features of MANET are quick set up, self organization and self maintenance. Routing is a major challenge in MANET due to it’s dynamic topology and high mobility. Several routing algorithms have been developed for routing. This paper studies the AODV protocol and how AODV is performed under multiple connections in the network. Several issues have been identified. The bandwidth is recognized as the prominent factor reducing the performance of the network. This paper gives an improvement of normal AODV for simultaneous multiple connections under the consideration of bandwidth of node.

PEER TO PEER CACHE RESOLUTION MECHANISM FOR MOBILE AD HOC NETWORKS

In this paper we investigate the problem of cache resolution in a mobile peer to peer ad hoc network. In our vision cache resolution should satisfy the following requirements: (i) it should result in low message overhead and (ii) the information should be retrieved with minimum delay. In this paper, we show that these goals can be achieved by splitting the one hop neighbours in to two sets based on the transmission range. The proposed approach reduces the number of messages flooded in to the network to find the requested data. This scheme is fully distributed and comes at very low cost in terms of cache overhead. The experimental results gives a promising result based on the metrics of studies.

Mobile P2Ping: A Super-Peer based Structured P2P System Using a Fleet of City Buses

Recently, researchers have introduced the notion of super-peers to improve signaling efficiency as well as lookup performance of peer-to-peer (P2P) systems. In a separate development, recent works on applications of mobile ad hoc networks (MANET) have seen several proposals on utilizing mobile fleets such as city buses to deploy a mobile backbone infrastructure for communication and Internet access in a metropolitan environment. This paper further explores the possibility of deploying P2P applications such as content sharing and distributed computing, over this mobile backbone infrastructure. Specifically, we study how city buses may be deployed as a mobile system of super-peers. We discuss the main motivations behind our proposal, and outline in detail the design of a super-peer based structured P2P system using a fleet of city buses.