Mobility Support for Diffusion-based Ad-Hoc Sensor Networks

In this work we investigate the application of four simple enhancements to directed diffusion to support mobile users. The first is a small change to diffusion which restarts path discovery when a node moves. The second is a simple handoff scheme similar to those used in cellular networks. The third introduces special proxy nodes as path anchors, and the fourth scheme provides hints to the diffusion layer to pre-create routes in an anticipated direction of motion. We compared the behavior of the various schemes for a mobile user tracking an object in a sensor network under four mobility scenarios. Our simulation results show that a combination of these simple enhancements to diffusion permit sink speeds of up 7 meters per second without generating excessive overhead. Increasing the transmit power was also an effective method of reducing the impact of mobility. Finally, we found that random motion is the most difficult mobility scenario, so approaches shown to work under random motion should also work well under more realistic mobility conditions.