动态无线传感网中低延迟高可靠的数据查询机制

查询处理作为大规模无线传感器网络中智能服务的一个重要操作,可以根据用户需求对网络中的感知数据进行检索和回传.然而,部署在恶劣环境中的无线传感网络,节点容易遭受外力破坏,或者自身资源(能量、存储等)有限,可能会导致节点发生位移和故障,从而造成网络拓扑不断改变以及部分节点的感知数据失效.同时,由于节点感知数据容量大、传输带宽有限以及网络链路不可靠等情况,可能会造成网络通信时延大大增加.这些因素使得快速、可靠的数据查询处理成为无线传感网中一个难题.为了解决这个难题,提出一种动态网络中低延迟高可靠的数据查询机制.该机制是一种非聚合随机查询方式,通过将传感节点划分为源节点和查询节点来实现数据查询.首先,根据监测事件将网络划分为若干个子区域,每个子区域中的源节点相互协作,并按照时间顺序依次轮流监听该区域的事件信息;接着,源节点根据预估的平均节点故障概率,计算出一个合理的备份数量,并将源数据按照该数量存储到邻居节点中,以降低源数据的失效概率;然后,为了加快数据查询速度,源节点定期对源数据块进行编码压缩,并选取剩余能量和存储空间较小的多个邻居节点作为下一跳接收节点.这些接收节点基于局部区域中节点个数大小,决定是否接收存储该报文.重复上述过程,直至压缩数据均匀地分布在网络中.另一方面,查询节点接收到查询请求时,也使用负载均衡多路分发方式将查询请求传输到部分节点上.为了避免目标数据的冗余回传,当查询请求成功查询到目标数据时,目标节点先修改访问位,再选取与查询节点距离最近的邻居节点作为下一跳接收节点,迭代执行上述操作,直到用户获得所需要的事件信息.在以上过程中,为了节省节点能量,在保证高成功查询率的条件下,建立通信能耗最小化的优化模型,计算出最优的压缩数据副本数和查询消息副本数,之后,源节点和查询节点分别按照该数量进行副本数据分发.最后,理论分析和实验结果表明,与其它四种查询算法相比,提出的查询机制具有更高的查询成功率、更低的通信能耗和通信时延.

Low Latency and High Reliable Data Query Mechanism in Dynamic Wireless Sensor Networks

As an important operation of intelligent services in large-scale wireless sensor networks,query processing can retrieve and return perceived data in the network according to user requirements.However,when wireless sensor networks are deployed in harsh environments,nodes are vulnerable to external forces,or its self-resources(energy,storage,etc.)are limited,which may lead to nodes displacement and failure,resulting in constant changes in the network topology and the failure of perceived data of some nodes.At the same time,due to the large capacity of sensor data,limited transmission bandwidth and unreliable network links,the network communication delay may be greatly increased.These factors make fast and reliable data query processing a difficult problem in wireless sensor networks.In order to solve this problem,a low latency and high reliability data query mechanism in dynamic networks is proposed.The mechanism is a non-aggregated random query method,which can realize data query by dividing sensor nodes into source nodes and query nodes.Firstly,the network is divided into several sub-regions according to the monitoring events.The source nodes in each sub-region cooperate with each other,and listen to the event information of the region in turn according to the time sequence;then,according to the estimated average node failure probability,the source nodes calculate a reasonable number of backups,and stores the source data in the neighbor nodes according to the number,so as to reduce the failure probability of the source data;secondly,in order to speed up the data query speed,the source nodes periodically encode and compress the source data block,and select multiple neighbor nodes with less residual energy and storage space as the next hop receiving nodes.These receiving nodes decide whether to receive and store the message based on the number of nodes in the local area.The above process is repeated until the compressed data is uniformly distributed in the network.On the other hand,when the query node receives query request,it also uses the method of load balancing multi-path dissemination to transmit the query request to some nodes.In order to avoid the redundant return of the target data,when the query request succeeds in querying the target data,the target node first modifies the access bit,then selects a node with the smallest distance between its neighbor nodes and the query node as the next hop receiving node,and performs the above operation iteratively until the user obtains the required event information.In the above process,in order to save the energy of the nodes,under the condition of ensuring high successful query rate,an optimization model of minimizing communication energy consumption is established,and the optimal number copies of the compressed data and the query request are calculated,then the source nodes and query nodes disseminate its replica data according to the number respectively.Finally,theoretical analysis and experimental results show that compared with other four query algorithms,the proposed query mechanism has higher successful query rate,lower communication energy consumption and communication delay.