Abstract: A communication network and method employing chained sequences of communications devices, to support synchronized relaying of data, thus forming duplex data buses. These data buses support both synchronous virtual circuits and a form of synchronized interrogate-respond data transfer. Off-bus communications devices are permitted to synchronously respond onto the bus without time contention.

Abstract: Communication devices and communication network techniques are employed to meet safety-critical, operational requirements for train location and control in railroad and public transit applications. On-board and trackside communication radios participate in a synchronous, time-slotted communication network, providing contentionless and highly responsive access to all participants. Encrypted, validated, and error protected communication links provide reliable and redundant transfer of information among the train, trackside, and control station radios. Spread spectrum communication techniques enable range measurements between all participants. These wireless communication links relay train range measurements to control or processing stations and relay control information (principally speed commands) from the processing stations to the trains. High resolution position location is determined along elevated, at-grade, and in-tunnel tracks using wireless methods and sparse device placement.