# US 12,003,664 B2 · Automatic redirecting of enhanced 911 calls

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- Number: US 12,003,664 B2
- Document ID: US12003664B2
- Status: Granted
- Kind: B2
- Application number: 17/553,570
- Filed: 2021-12-16
- Published: 2023-06-22
- Granted: 2024-06-04
- Earliest claimed: 2021-12-16
- Assignees: T-Mobile USA, Inc.
- Applicants: T-Mobile USA, Inc.
- Inventors: Pei Zheng
- Web page: https://patentgrep.com/patent/US12003664B2

## CPC

- H04M 3/323: {for the arrangements providing the connection (test connection, test call, call simulation)}
- H04M 3/42382: {Text-based messaging services in telephone networks such as PSTN/ISDN, e.g. User-to-User Signalling or Short Message Service for fixed networks}
- H04M 3/5116: {for emergency applications}
- H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08)

## Abstract

To reduce the likelihood that test E911 calls will be improperly connected to a public safety access point (PSAP), while ensuring that mobile devices sold to consumers are correctly routed to a PSAP in an emergency, a system for automatically redirecting test E911 calls to an answering system is disclosed. An unstructured supplementary service data (USSD) node receives a first USSD message from a mobile device during E911 testing procedure at the mobile device. In response to identifying a first code in the first USSD message, the USSD node retrieves an identifier associated with the mobile device. The USSD node sends an instruction to a gateway mobile location center (GMLC) system to redirect E911 calls from the mobile device based on the retrieved identifier such that a subsequent E911 call placed by the mobile device is automatically rerouted by the GMLC to an answering line instead of a PSAP.

## Claims

### Claim 1

A system operating as an unstructured supplementary service data (USSD) node, the system comprising:
at least one hardware processor; and
at least one non-transitory memory storing instructions, which, when executed by the at least one hardware processor, cause the system to:
receive, from a mobile device, a first USSD message generated by the mobile device during an enhanced 911 (E911) testing procedure;
in response to identifying a first code in the first USSD message, retrieve an identifier associated with the mobile device; and
send an instruction to a gateway mobile location center (GMLC) system to redirect E911 calls from the mobile device based on the retrieved identifier such that a subsequent E911 call placed by the mobile device is automatically rerouted by the GMLC to an answering line instead of a public safety access point (PSAP).

### Claim 2 (depends on 1)

The system of claim 1, wherein the instructions when executed further cause the system to:
after sending the first instruction to the GMLC, transmit a confirmation to the mobile device to indicate that E911 calls from the mobile device are being redirected to the answering line.

### Claim 3 (depends on 2)

The system of claim 2, wherein the confirmation causes the mobile device to display a notification to indicate that E911 call from the mobile device are being redirected to the answering line.

### Claim 4 (depends on 1)

The system of claim 1, wherein the instructions when executed further cause the system to:
receive from the mobile device, a second USSD message; and
in response to identifying a second code in the second USSD message, send a second instruction to the GMLC system to stop redirecting E911 calls from the mobile device to the answering line, such that an E911 call placed by the mobile device is directed to the PSAP by the GMLC after the second instruction is sent.

### Claim 5 (depends on 4)

The system of claim 4, wherein the instructions when executed further cause the system to:
after sending the first instruction to the GMLC, transmit a first confirmation to the mobile device to indicate that E911 calls from the mobile device are being redirected to the answering line,
wherein the first confirmation causes the mobile device to display a persistent notification to indicate that E911 call from the mobile device are being redirected to the answering line; and
after sending the second instruction to the GMLC, transmit a second confirmation to the mobile device to indicate that E911 calls from the mobile device are no longer being redirected to the answering line,
wherein the second confirmation causes the mobile device to stop displaying the persistent notification.

### Claim 6 (depends on 1)

The system of claim 1, wherein the first instruction comprises a command to add the identifier of the mobile device to a redirect list maintained by the GMLC.

### Claim 7 (depends on 6)

The system of claim 6, wherein the instructions when executed further cause the system to:
in response to receiving, from the mobile device, a third USSD message containing a third USSD code, transmit the redirect list to the mobile device.

### Claim 8 (depends on 1)

The system of claim 1, wherein the instructions when executed further cause the system to:
in response to receiving, from the mobile device, a fourth USSD message that contains a fourth USSD code and specifies an identifier of user equipment, query the redirect list using the identifier of the user equipment; and
transmit, to the mobile device, an indication of whether the user equipment is listed on the redirect list based on the query.

### Claim 9

At least one computer-readable storage medium, excluding transitory signals and carrying instructions, which, when executed by at least one data processor of a system, cause the system to:
receive from user equipment, a first unstructured supplementary service data (USSD) message;
in response to identifying a first code in the first USSD message, retrieve an identifier associated with the user equipment; and
send a first instruction to a gateway mobile location center (GMLC) system to redirect enhanced 911 (E911) calls from the user equipment based on the retrieved identifier such that a subsequent E911 call placed by the user equipment is automatically rerouted by the GMLC to an answering line instead of a public safety access point (PSAP).

### Claim 10 (depends on 9)

The at least one computer-readable storage medium of claim 9, wherein the instructions when executed further cause the system to:
after sending the first instruction to the GMLC, transmit a confirmation to the user equipment to indicate that E911 calls from the user equipment are being redirected to the answering line.

### Claim 11 (depends on 10)

The at least one computer-readable storage medium of claim 10, wherein the confirmation causes the user equipment to display a notification to indicate that E911 call from the user equipment are being redirected to the answering line.

### Claim 12 (depends on 9)

The at least one computer-readable storage medium of claim 9, wherein the instructions when executed further cause the system to:
receive from the user equipment, a second USSD message; and
in response to identifying a second code in the second USSD message, transmit a second instruction to the GMLC system to stop redirecting E911 calls from the user equipment to the answering line, such that an E911 call placed by the user equipment is directed to the PSAP by the GMLC after the second instruction is sent.

### Claim 13 (depends on 12)

The at least one computer-readable storage medium of claim 12, wherein the instructions when executed further cause the system to:
after sending the first instruction to the GMLC, transmit a first confirmation to the user equipment to indicate that E911 calls from the user equipment are being redirected to the answering line, wherein the first confirmation causes the user equipment to display a persistent notification to indicate that E911 call from the user equipment are being redirected to the answering line; and
after sending the second instruction to the GMLC, transmit a second confirmation to the user equipment to indicate that E911 calls from the user equipment are no longer being redirected to the answering line, wherein the second confirmation causes the user equipment to stop displaying the persistent notification.

### Claim 14 (depends on 9)

The at least one computer-readable storage medium of claim 9, wherein the first instruction comprises a command to add the identifier of the user equipment to a redirect list maintained by the GMLC.

### Claim 15 (depends on 14)

The at least one computer-readable storage medium of claim 14, wherein the instructions when executed further cause the system to:
in response to receiving, from the user equipment, a third USSD message containing a third USSD code, transmit the redirect list to the user equipment.

### Claim 16 (depends on 9)

The at least one computer-readable storage medium of claim 9, wherein the instructions when executed further cause the system to:
in response to receiving, from the user equipment, a fourth USSD message that contains a fourth USSD code and specifies an identifier of a mobile device, query the redirect list using the identifier of the mobile device; and
transmit, to the user equipment, an indication of whether the mobile device is listed on the redirect list based on the query.

### Claim 17

A gateway mobile location center (GMLC) system operating within a telecommunications network, the GMLC system comprising:
at least one hardware processor; and
at least one non-transitory memory storing instructions, which, when executed by the at least one hardware processor, cause the GMLC system to:
maintain a redirect list including identifiers of user equipment that are undergoing enhanced 911 (E911) testing,
wherein an identifier of selected user equipment is automatically added to the redirect list or automatically removed from the redirect list based on unstructured supplementary service data (USSD) messages originating from the selected user equipment that contain corresponding USSD codes defined within the telecommunications network; and
selectively route E911 calls placed by user equipment to a public safety access point (PSAP) or an answering line based on the redirect list.

### Claim 18 (depends on 17)

The GMLC system of claim 17, wherein the instructions when executed further cause the GMLC system to:
receive notification that identified user equipment has initiated an E911 call;
query the redirect list for an identifier of the identified user equipment;
in response to determining the redirect list does not include the identifier of the identified user equipment, determine a geographic location of the identified user equipment; and
direct the E911 call from the identified user equipment to a PSAP selected based on its proximity to the determined geographic location of the identified user equipment.

### Claim 19 (depends on 17)

The GMLC system of claim 17, wherein the instructions when executed further cause the GMLC system to:
output the redirect list to a wireless device in response to a USSD message containing a corresponding code defined within the telecommunications network to cause the GMLC system to output the redirect list.

### Claim 20 (depends on 17)

The GMLC system of claim 17, wherein the instructions when executed further cause the GMLC system to:
query the redirect list for an identifier of specified user equipment in response to a USSD message, received from a wireless device, that contains a corresponding code defined within the telecommunications network to cause the GMLC system to return a redirect status of the specified user equipment; and
transmit the redirect status to the wireless device, the transmitted redirect status indicating whether the specified user equipment is identified on the redirect list based on the query.