Multiple Location Retrieval Function (LRF) Network Having Location Continuity

Abstract

An IMS emergency call is reliably handed off within the PS domain or from the PS domain to the CS domain, by providing continuous support of location of a user device on behalf of a PSAP. The invention provides for handover of an IMS emergency call with EPS/GPRS access in a multi-LRF environment. Emergency location services for CS based emergency and/or IMS based emergency location services are often provided by multiple emergency location service providers. The information element that is critical for supporting Location Continuity in Multi-LRF environment can be either the assigned ESQK or the Serving LRF address. ESQK is assigned by the Serving LRF during IMS emergency call setup, and is used to uniquely identify the emergency service provider that operates the serving LRF. A simpler implementation uses the Serving LRF's address to identify the Serving LRF during and after the handover (PS-PS or PS-CS).

1 . A retrieval function network device in multiple location retrieval function network to ensure voice call continuity (VCC) during handover of an emergency call from a user wireless device, comprising:
 receiving control of an initialed IP Multimedia Subsystem (IMS) emergency user call from a user wireless device;   participating in a handover of said IMS emergency call from a first emergency services network to a second emergency services network; and   routing an emergency services routing key (ESRK) of an emergency services query key (ESQK) from a source server in said first emergency services network to a target server in said second emergency services network.   
     
     
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