Distributed protocols for access arbitration in tree-structured communication channels

The problem of arbitrating access to a tree-structured communication channel, with large geographic extent, providing multipoint communication among a set of terminals, is considered. Terminals transmit information in bursts consisting of many packets and compete for the right to transmit bursts. In the simplest case, the channel allows only one terminal to transmit at a time; this can be extended to k concurrent transmitters. Two general approaches are identified. The first is based on the idea of transmit permits or tokens; that is, a terminal must have explicit permission to transmit before starting a burst. The second approach allows terminals to transmit whenever the number of bursts they can observe from their vantage point is less than the limiting number; the network then performs arbitration internally, possibly aborting some bursts in the process, to prevent too many bursts from being active on a link at one time. Several specific access arbitration algorithms based on these approaches are presented and assessed