apparatus and methods for providing cellular mobile telecommunication service in accordance with the requirements of the global systems for mobile communications standard . a modular switching system is provided which performs the functions of the mobile switching center plus those of a home location register , authentication center , visitor location register , and equipment identity register . the latter functions are advantageously spread among the modules of the switching system , thus avoiding the getting started cost of expensive dedicated data bases . a wireless global switching module advantageously switches mobile communications control messages among the modules of the system and between the modules and the base station systems , and terminates signaling links between the mobile switching center and the base station systems .