Multiple location retrieval function (LRF) network having location continuity

• US 20100284366A1
• Filed: 09/11/2009
• Published: 11/11/2010
• Est. Priority Date: 05/05/2009
• Status: Active Grant

• Current Assignee: TeleCommunication Systems Inc (Comtech Telecommunications Corporation)
• Original Assignee: TeleCommunication Systems Inc (Comtech Telecommunications Corporation)
• Inventors: Zhu, Yinjun
• Granted Patent: US 8,867,485 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04W 36/0022 for transferring data sessions between adjacent core network technologies
• CPC Class Codes: H04W 36/00226 wherein the core network technologies comprise IP multimedia system [IMS], e.g. single radio voice call continuity [SRVCC]
• CPC Class Codes: H04W 36/0033 with transfer of context information
• CPC Class Codes: H04W 4/023 using mutual or relative location information between multiple location based services [LBS] targets or of distance thresholds
• CPC Class Codes: H04W 4/90 Services for handling of emergency or hazardous situations, e.g. earthquake and tsunami warning systems [ETWS]
• CPC Class Codes: H04W 76/50 for emergency connections

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).

Claims

1. A location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device, comprising:

receiving control of an initiated IP Multimedia Subsystem (IMS) emergency 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) or 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.

2. The location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device according to claim 1, further comprising:

passing a routing address of a location retrieval function (LRF) server in said first emergency services network to said target server in said second emergency services network.

3. The location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device according to claim 1, further comprising:

passing a handover location report from said source server in said first emergency services network to said target server in said second emergency services network.

4. The location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device according to claim 3, wherein:

said handover location report includes a routing address of a LRF server in said first emergency services network.

5. The location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device according to claim 1, wherein:

said ESRK or ESQK is passed from a 4G network to a 3G network.

6. The location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device according to claim 1, wherein:

said ESRK or ESQK is passed from a 4G network to a 2G network.

7. The location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device according to claim 6, wherein:

said user device is a GSM wireless phone.

8. The location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device according to claim 1, wherein:

said user wireless device is a GSM wireless phone.

9. The location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device according to claim 1, wherein:

said ESRK or ESQK is passed from a server in a 4G network to a server in a 3G network.

10. The location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device according to claim 9, wherein:

said user device is a GSM wireless phone.

11. The location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device according to claim 1, wherein:

said first emergency services network is a packet switched (PS) network.

12. The location retrieval function network device in a multiple location retrieval function network to ensure voice call continuity (VCC) during a handover of an emergency call from a user wireless device according to claim 11, wherein:

said second emergency services network is a circuit switched (PS) network.