# US 2020/0396335 A1 · IMS Emergency Call Routing Techniques

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- Number: US 2020/0396335 A1
- Document ID: US20200396335A1
- Status: Published application
- Kind: A1
- Application number: 16/792,558
- Filed: 2020-02-17
- Published: 2020-12-17
- Earliest claimed: 2015-08-07
- Assignees: Apple Inc.
- Applicants: Apple Inc.
- Inventors: Alexandre Saso Stojanovski; Frederick Joly; Jerome Parron
- Web page: https://patentgrep.com/patent/US20200396335A1

## CPC

- H04M 3/5116: {for emergency applications}
- H04L 65/1016: IP multimedia subsystem [IMS]
- H04L 65/1045: Proxies, e.g. for session initiation protocol [SIP]
- H04L 65/1069: Session establishment or de-establishment
- H04L 65/1104: Session initiation protocol [SIP]
- H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

IMS emergency call routing techniques are described. In one embodiment, for example, an apparatus may comprise at least one memory and logic for a P-CSCF node, at least a portion of the logic comprised in circuitry coupled to the at least one memory, the logic to cause the P-CSCF node to receive an SIP INVITE message from a roaming UE, the SIP INVITE message associated with an attempt to place an emergency call via an unauthenticated IMS session, the logic to cause the P-CSCF node to obtain a PSAP callback number for the UE from a PCRF node via an Rx interface, identify a PSAP callback parameter for the UE based on the PSAP callback number, insert the PSAP callback parameter into the SIP INVITE message, and forward the SIP INVITE message to a PSAP. Other embodiments are described and claimed.

## Claims

### Claim at position 1

1-25. (canceled)

### Claim 26

A non-transitory computer readable medium, comprising instructions, wherein the instructions, when executed by a processor, cause a mobility management entity (MME) to:
receive, at the MME, an emergency packet data network (PDN) connection request message from a user equipment (UE), identifying a public safety answering point (PSAP) callback number for the UE, and
direct a session creation request message to a PDN gateway (PGW) in a visited public land mobile network (VPLMN) of the UE, the session creation request message comprising the PSAP callback number for the UE.

### Claim 27 (depends on 26)

The non-transitory computer readable medium of claim 26, the session creation request message comprising an emergency indicator to indicate that the session creation request message comprises an emergency request.

### Claim 28 (depends on 26)

The non-transitory computer readable medium of claim 26, further comprising obtaining the PSAP callback number from a home subscriber services (HSS) node of a home public land mobile network (HPLMN) of the UE.

### Claim 29 (depends on 28)

The non-transitory computer readable medium of claim 28, further comprising obtaining the PSAP callback number from the HSS node via an S6a interface.

### Claim 30 (depends on 28)

The non-transitory computer readable medium of claim 28, the emergency PDN connection request message comprising an S1 ATTACH REQUEST message.

### Claim 31 (depends on 30)

The non-transitory computer readable medium of claim 30, further comprising:
send an authentication request message to the HSS node; and
receive an authentication response message comprising the PSAP callback number in response to the authentication request message.

### Claim 32 (depends on 28)

The non-transitory computer readable medium of claim 28, the emergency PDN connection request message comprising an S1 PDN CONNECTIVITY REQUEST message.

### Claim 33 (depends on 32)

The non-transitory computer readable medium of claim 32, further comprising:
sending a PSAP callback number request message to the HSS node; and
receiving a response message comprising the PSAP callback number in response to the PSAP callback number request message.

### Claim 34 (depends on 32)

The non-transitory computer readable medium of claim 32, the PSAP callback number obtained from the HSS node prior to receipt of the emergency PDN connection request message.

### Claim 35 (depends on 26)

The non-transitory computer readable medium of claim 26, the session creation request message comprising a Create Session Request message.

### Claim 36 (depends on 26)

The non-transitory computer readable medium of claim 26, the PSAP callback number comprising a mobile station international subscriber directory number (MSISDN) associated with the UE.

### Claim 37

A mobility management entity (MME), comprising:
at least one memory; and
logic, at least a portion of which is implemented in circuitry coupled to the at least one memory, the logic configured to:
receive, at the MME, an emergency packet data network (PDN) connection request message from a user equipment (UE), identifying a public safety answering point (PSAP) callback number for the UE, and
direct a session creation request message to a PDN gateway (PGW) in a visited public land mobile network (VPLMN) of the UE, the session creation request message comprising the PSAP callback number for the UE.

### Claim 38 (depends on 37)

The MME of claim 37, the session creation request message comprising an emergency indicator to indicate that the session creation request message comprises an emergency request.

### Claim 39 (depends on 37)

The MME of claim 37, the logic further configured to: obtain the PSAP callback number from a home subscriber services (HSS) node of a home public land mobile network (HPLMN) of the UE.

### Claim 40 (depends on 39)

The MME of claim 39, comprising obtaining the PSAP callback number from the HSS node via an S6a interface.

### Claim 41

A method, comprising:
receiving, at a mobility management entity (MME), an emergency packet data network (PDN) connection request message from a user equipment (UE), identifying a public safety answering point (PSAP) callback number for the UE, and
directing a session creation request message to a PDN gateway (PGW) in a visited public land mobile network (VPLMN) of the UE, the session creation request message comprising the PSAP callback number for the UE.

### Claim 42 (depends on 41)

The method of claim 41, the session creation request message comprising an emergency indicator to indicate that the session creation request message comprises an emergency request.

### Claim 43 (depends on 41)

The method of claim 41, further comprising obtaining the PSAP callback number from a home subscriber services (HSS) node of a home public land mobile network (HPLMN) of the UE.

### Claim 44 (depends on 43)

The method of claim 43, further comprising obtaining the PSAP callback number from the HSS node via an S6a interface.

### Claim 45 (depends on 43)

The method of claim 43, the emergency PDN connection request message comprising an S1 ATTACH REQUEST message.