Abstract: A digital cellular handset capable of supporting voice communications over the Internet, in addition to the digital cellular handset's usual mode of voice communications over the digital cellular network/public telephony network is disclosed. Internet protocol software such as H.323, Session Initiation Protocol (SIP), and Media Gateway Control Protocol (MGCP) is stored within the digital cellular handset device run on an H.323 Digital Signal Processor (DSP) and H.323 microcontroller to packetize and unpacketize the digital data streams received by or transmitted from the handset. There is also disclosed the use of the Short Message Service (SMS) with PCS digital cellular communication systems to allow call alerting for digital cellular call set-up, initiation and establishment.

Abstract: In the occurrence of a multi-mode portable handset leaving the coverage area of a first operating network during an active telephone call on the first operating network, a method is disclosed for terminating the telephone call and re-initiating it within a second operating network. The signal strength and bit error rate corresponding to the first operating network are monitored during the telephone call. When it is determined that the handset is leaving the coverage area using these indicators, the handset warns both parties in the conversation. With use of the redial function or CLID (Calling Line Identification) the telephone number of the party other than the user of the portable handset is determined. The handset proceeds to terminate the call on the first operating network and dials the telephone number corresponding to the other party on the second operating network. The telephone conversation can then proceed on the second operating network with a minimum inconvenience to the user of the handset.