Data query is one of the most important issues in wireless ad hoc networks, since the ultimate goal of these networks is to support efficient data sharing among wireless nodes. In this paper, we study the issue of data query for delay-sensitive applications in dense wireless ad hoc networks. We focus our attention on step-by-step expanding ring-based data query, which provides an upper bound on query delay to any expanding ring based query strategies. Two replication strategies including Index Replication (IR) and Data Replication (DR) are considered, to improve the delay performance of data query. We analyze the probabilistic behavior of query delay for both DR and IR by theoretical methods, and develop analytical models to approximate the minimum number of replicas required for both query strategies if an application-specified delay bound is imposed. Our work is validated through extensive simulations.

With the advances of micro-electronic and wireless communication technology, deploying a large number of low cost, small-sized sensor nodes over a vast area for environment monitoring is becoming more practical. Setting up gradients for delivering queries or data reports by flooding the sensor networks consumes a great deal of energy especially for large scale sensor networks. In this paper, we propose an energy conserving observer-initiated data dissemination protocol, called Grid Map Data Query Protocol (GMDQP), for multiple mobile sinks on a large scale sensor network. It conserves communication energy by employing a grid map data query technique to avoid full network events or queries flooding. A data source only announces the existence of data within a local area and a sink collects data by sending query message in a grid map. Nodes at cross point of grid check and query the data. It conserves energy by avoiding full network flooding in setting up data forwarding path. Simulations show that the proposed architecture is quite energy efficient.