An efficient protocol for geographically addressed streaming

Scalable wireless geographically addressed messaging has been shown to enable applications critical to the core missions of field operation teams. In particular, the Scalable Ad hoc Geocast Protocol (SAGP) has been used to implement a scalable field common operating picture among smartphone class devices, as well as reliable multimedia messaging and distributed collaboration under challenging field conditions. In this paper, we study a third category: streaming applications. In geographically addressed streaming, one wishes to distribute a data feed to all devices in a geographic area. Example uses include voice calls (both 1-1 and group), distribution of video to operators in an area, and speeding up the distribution of large files. While SAGP itself may be used to implement robust streaming, this paper describes a novel enhancement to SAGP, termed Follow cast, that exploits the properties of streaming applications to obtain efficient and scalable bandwidth use while maintaining acceptable reliability. This paper describes Follow cast and two applications of it. It then evaluates its efficiency and reliability through measurements of a smartphone prototype, simulations, and analysis.