Multiple Control Stations in Packet Radio Networks

This paper presents a design recently implemented by the Packet Radio project for control of large networks. The network is built on a carrier sense, multiple access broadcast channel and is populated with mobile store and forward nodes known as packet radio units, or PRs. Until recently, the packet radio network operated with centralized routing controlled by one node, the station. To increase the size of the network and to provide redundant control a multiple station design, "multistation", was necessary. The PRs gather local connectivity information which is then forwarded to the controlling nodes (stations). Each station is responsible for up to 40 PRs located near it in connectivity and uses these PRs to communicate with other stations. Questions important to the development of multistation include: How are packet radios matched with controlling stations? How do stations find and communicate with each other? How are long routes crossing the borders of many stations determined, and how is their successful setup insured? How is control traffic minimized?