Multiple channel communications system

摘要

A multi-channel communications system for communications between a mobile units and dispatch agencies through tower sites under control of a multi-channel communication controller. The method of communications used is time division multiple access with provisions for alternate methods. The mobile units and dispatch agencies have forms of identifications to route messages between the mobile units and dispatch agencies according to the forms of identification. The forms of identification are resolved from one form to another to operate with the alternate methods of communications. The mobile units are handed off from one communications channel to another by the multi-channel controller as channel loading conditions exceed a predetermined limit. Mobile units change tower sites as the geographic coverage of a tower site changes. Mobile units determine distance to a tower site by computing distance to a tower site by using GPS position information of the mobile unit and the known locations of the tower sites to compute signal strength.