Anand Rangarajan

Exploiting heterogeneity in sensor networks

The presence of heterogeneous nodes (i.e., nodes with an enhanced energy capacity or communication capability) in a sensor network is known to increase network reliability and lifetime. However, questions of where how many, and what types of heterogeneous resources to deploy remain largely unexplored. We focus on energy and link heterogeneity in ad hoc sensor networks and consider resource-aware MAC and routing protocols to utilize those resources. Using analysis, simulation, and real testbed measurements, we evaluate the impact of number and placement of heterogeneous resources on performance in networks of different sizes and densities. While we prove that optimal deployment is very hard in general, we also show that only a modest number of reliable, long-range backhaul links and line-powered nodes are required to have a significant impact. Properly deployed, heterogeneity can triple the average delivery rate and provide a 5-fold increase in the lifetime (respectively) of a large batten-powered network of simple sensors.

Designing and deploying a rural ad-hoc community mesh network testbed

Rural communities suffer from a lack of infrastructure for inexpensive high-speed access to the Internet. One approach to providing high-speed access in these environments is to share a small number of more expensive high-speed connections across the community. A wireless mesh network can provide a low-cost backbone to enable this sharing. Existing solutions to building community mesh networks use proprietary technology or typically require rooftop or other outdoor antenna deployment. We examine the feasibility of constructing a community mesh network in a rural neighborhood at Dartmouth College using off-the-shelf hardware and software components and without using an outdoor antenna. We identify several challenges to construction of such networks including network density, hardware limitations, and US electrical code. In this paper, we outline some of the key challenges we faced during our deployment and suggest solutions