Maintaining stable virtual circuit data connections with spare protocol handler

Abstract

This invention relates to apparatus and methods for providing cellular mobile telecommunication service in accordance with the requirements of the Global Systems for Mobile Communications (GSM) 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. Arrangements are provided for maintaining stable virtual circuit connections in this module even in the presence of protocol handler failures. The state of each virtual circuit is kept in a protocol handler (PH) controlling the circuit and, whenever a stable state is reached, notifying an adjacent PH; if the controlling PH fails, the adjacent PH takes over control of that virtual circuit for immediate purposes, and a spare PH serves any new requests that would normally be served by the failed PH. The spare PH transmits messages, originally destined to the failed PH, to the adjacent PH for those virtual circuits already in use at the time of the failure and being served by the adjacent PH.

Dependencies are inferred from the claim text.