Dynamic Spatial Aggregation Query Researches In Wireless Sensor Networks

Wireless sensor network, which is made by the convergence of sensor technology, embedded compute technology, distributed information processing and communication technology, is a novel technology about real-time monitoring, acquiring and processing information, such information is sent through wireless and multi-hop network transmission to these users in need. Sensor networks will enable people at any time and any place access to large number of detail and reliable information. Therefore, such a network system can be widely used in the military for national defense, national security, environmental monitoring, traffic management, health care, manufacturing, anti-terrorism disaster areas and so on.In this paper, we investigate how to process spatial aggregation query over dynamic geosensor networks where both the sink node and sensor nodes may move around. The existing static routing protocols and aggregation algorithms are not available directly to this case, because dynamic framework for the maintenance of a fixed network (tree structure, a cluster or leader) may lead to excessive energy consumption, message overloads, packet losses and transmission latency. So we present a novel location aware and pull-based routing aggregation strategies for window query processing in dynamic geosensor networks.First, routing a query toward the area specified by its query window. We improve the stateless of implicit geographic forwarding (IGF) protocol within the 60-degree sector as following candidates during forwarding the query message to target area, all candidate nodes compete for forward mission.Secondly, to reducing message collisions and reaction latency after the messages are sent to target area, we present a novel diameter-based window aggregation query (DWAQ) algorithm for query propagation and data aggregation at the same time in the query window.Finally, considering the location changing of sink node, we present two schemes to forward the result to the sink node: Agent Seek-based (AS) scheme and Tracking Prediction-based (TP) scheme. AS scheme determines the region where the sender originally located, before it moves out, it searches an agent node located in the same original region to monitor and forward result to the sender. TP scheme determines the predicted region where the sink node may be in according to moving parameters, and then forwards the result to the destination, the routing protocol is the same as forwarding query messages.The simulation results show that, the larger the target window is, the better the performance both the query accuracy and latency of our DWAQ aggregation algorithm presented in this paper is; in the return stage, with the enhanced dynamics, the proposed TP algorithm than AS algorithm has less energy, lower latency and more superior performance.