Mobility-assisted resolution of queries in large-scale mobile sensor networks (MARQ)

• Authors: Ahmed Helmy
• Venue: Computer Networks: The International Journal of Computer and Telecommunications Networking - Special issue: Wireless sensor networks
• Year: 2003

One of the most crucial aspects of the design of sensor networks is provisioning of efficient query resolution and resource discovery. In many cases sensor networks are expected to be large-scale, and in some cases these sensors may be installed on moving objects, rendering the query resolution problem even more challenging. Flooding techniques, including global flooding or expanding ring search techniques, may be very inefficient in large-scale networks, especially in wireless (spatial) networks where the diameter of the network tends to be quite high. More so is the case when queries are one-shot and frequent.In this study, a novel architecture is presented for query resolution in large-scale mobile sensor networks. A salient feature of our architecture is that it takes advantage of mobility to increase the efficiency of query resolution. The architecture borrows from the concept of small worlds and introduces the concept of contacts that act as short cuts to reduce the degrees of separation between the sources of the query and the targeted objects. Contacts are initially chosen from nearby neighbors, as they move away they discover new neighbors and hence become more effective in query resolution. Unlike conventional approaches for routing protocols, our primary design goal is not to optimize routes or response delays, but to reduce communication overhead. This is particularly important in energy-constraint environments, as are many sensor networks, particularly for one-shot queries, where the communication is short lived. We design our protocols to be scalable, self-configuring, and highly adaptive to mobility. In fact, it utilizes mobility.We evaluate our protocols through extensive simulations and present a detailed analysis of its performance. We further compare our approach to other query resolution protocols. Our results clearly indicate the drastic improvement obtained by using contacts, especially in high mobility scenarios. For non-replicated objects, we obtain 60-70% improvement over zone routing approaches, 80-90% improvement in communication overhead over flooding, and even greater improvements over expanding ring search approaches. Our protocols respond extremely well to replication, as the number of transmitted packets per query drops significantly.