针对现有基于数据挖掘的文件关联性复制算法无法有效提取文件关联性的问题,提出了基于极大频繁关联模式挖掘的分散群复制算法(Decentralized Replication strategy based on Maximal Frequent Correlated Patterns,DRMFCP)。DRMFCP算法通过二进制历史文件转换、极大频繁关联模式挖掘和复制,以实现极大减少复制模式数量、消除冗余以及优化复制的目的。数据分析与仿真结果表明,在不同存取模式下相较于无复制、DR2、PRA和PDDRA算法,DRMFCP算法提取文件关联性的效率更高,并能同时降低作业执行平均时间,为降低网格数据传输延迟提供新的解决方案。
A critical challenge for mobile ad hoc networks is the design of efficient routing protocols which are able to provide high bandwidth utilization and desired fairness in mobile wireless environment without any fixed communication establishments. Although extensive efforts have already been devoted to providing optimization based distributed congestion elusion strategy for efficient bandwidth utilization and fair allocation in both wired and wireless networks,a common assumption therein is the fixed link capacities,which will unfortunately limit the application scope in mobile ad hoc networks where channels keep changing. In this paper,an effective congestion elusion strategy is presented explicitly based on ant colony algorithm for mobile ad hoc networks, which will explore the optimal route between two nodes promptly,meanwhile forecast congestion state of the link. Accordingly,a new path will be found rapidly to have the flow spread around to relieve the congestion degree. Compared with OLSR,the strategy proposed will greatly reduce the packet loss ratio and the average end-to-end delay at the same time,which illustrate that it will make use of networking resource effectively.
针对网络的安全性与稳定性较差问题,提出了以高效节能为前提,基于树的路由协议的安全模型(security model for tree-based routing protocols,SMTR),通过使用报文鉴别码和数字签名技术,为提高网络的安全性能提供了可靠保证。所构造模型还可以对常用报文鉴别码和数字签名技术在树的路由协议中的执行效果与能耗情况进行对比和评价,为提高无线网络的安全性提供新的解决方案。对安全模型评估与仿真结果表明,在安全模型中使用安全技术,能有效提高网络生存时间和安全性能,从而保证了数据的正确传输。
The negative impact on communication performance in wireless multi-hop communication network caused by limited bandwidth,high bit error rate(BER),fading,noise and interference is alleviated by an adaptive filtering game based on frequency subbands selection and predetermined threshold.Such threshold is being obtained in Gaussian and multipath fading channel according to the frequency-matching principle and BER performance.The dynamic selection of subbands will obtain high use efficiency without the help of frequency hopping,and propound a new thought to improve band limited communication for wireless multi-hop communication network.The effectiveness of the adaptive filtering method has been verified by interleaving spread spectrum orthogonal frequency division multiplexing(ISS-OFDM) in different interference conditions,and the simulating results based on network simulator 2(NS2) indicate that system BER can be improved greatly.
Data aggregation technology reduces traffic overhead of wireless sensor network and extends effective working time of the network,yet continued operation of wireless sensor networks increases the probability of aggregation nodes being captured and probability of aggregated data being tampered.Thus it will seriously affect the security performance of the network. For network security issues,a stateful public key based SDAM( secure data aggregation model) is proposed for wireless sensor networks( WSNs),which employs a new stateful public key encryption to provide efficient end-to-end security. Moreover,the security aggregation model will not impose any bound on the aggregation function property,so as to realize the low cost and high security level at the same time.
