Impact of Mobility on Last Encounter Routing Protocols

In this study, we analyze last encounter based routing protocol (eg., FResher Encounter SearcH, or FRESH) that utilizes encounter history to create time (or age) gradients for information diffusion in wireless networks. FRESH protocols can be used for resource discovery, routing or node location, and hold great promise for future wireless networks. We provide the first study on sensitivity of this class of protocols to a rich set of mobility models (manhattan, group, random walk and random waypoint models). We find that FRESH is sensitive to the mobility pattern. However, somewhat to our surprise, FRESH´s performance after warm-up is insensitive to velocity for all the mobility models examined. To expose the fundamental reason behind these observations, we develop analytical models to analyze FRESH´s performance and validate these models via extensive simulations. Finally, our analysis concludes that the characteristics of the age gradient tree is the key factor to explain this interplay between mobility and the performance of FRESH protocols.