Monitoring Exact Top-K Values in Wireless Sensor Networks Using Dominating Set Trees

Top-k queries form an important class of aggregation queries in wireless sensor networks. Unlike previous proposals we consider the exact top-k values query problem, i.e., where one seeks to find exactly all k highest unique values in the network regardless of how many nodes report it. Previous proposals also did not pay due attention to the underlying logical tree topology used for data aggregation and forwarding. In this context, this paper presents two main contributions: (1) we propose the use of a particular tree topology, based on Dominating Sets, which is well suited to explore the network’s physical topology for processing top-k queries efficiently; and (2) we propose EXTOK, a filtering-based algorithm for processing the exact top-k values query, we also prove its correctness and investigate its performance with respect to a number of parameters, including network link failures. In all examined cases, EXTOK performs consistently well while effectively exploiting the proposed logical tree topology and it is also resilient to link failures.