Patent ID: 8406800

Claim:
A method for establishing an inter-radio frequency subsystem interface (ISSI) unit-to-unit call between a calling unit of a calling home radio frequency subsystem (RFSS) and a called unit of a called home RFSS through a hosted ISSI function (HIF) device, the method comprising: processing, at the HIF device, a first invite message received from the calling home RFSS, wherein the first invite message includes a first request uniform resource identifier (URI) that designates an alias system unit identification (SU-ID); and in response to the first invite message, transmitting, from the HIF device to the called home RFSS, a second invite message, including a second request URI that designates a real SU-ID, wherein the HIF device acts as the calling home RFSS; whereby the unit-to-unit call is established between the calling unit and the called unit through the calling home RFSS, the HIF device, and the called home RFSS.