# US 12,016,070 B2 · Efficient evolved packet system (EPS) fallback

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- Number: US 12,016,070 B2
- Document ID: US12016070B2
- Status: Granted
- Kind: B2
- Application number: 17/986,750
- Filed: 2022-11-14
- Published: 2023-03-09
- Granted: 2024-06-18
- Earliest claimed: 2019-04-05
- Assignees: T-Mobile USA, Inc.
- Applicants: T-Mobile USA, Inc.
- Inventors: Rahul Pal; Suresh Thanneeru; Salvador Mendoza; Karunakalage Viraj Rakitha Silva
- Web page: https://patentgrep.com/patent/US12016070B2

## CPC

- H04W 76/12: Setup of transport tunnels
- H04W 76/18: Management of setup rejection or failure
- H04L 12/66: Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
- H04L 47/20: Traffic policing
- H04L 65/1033: Signalling gateways
- H04L 65/1069: Session establishment or de-establishment
- H04L 65/65: Network streaming protocols, e.g. real-time transport protocol [RTP] or real-time control protocol [RTCP]
- H04L 65/80: Responding to QoS
- H04W 8/02: Processing of mobility data, e.g. registration information at HLR [Home Location Register] or VLR [Visitor Location Register]; Transfer of mobility data, e.g. between HLR, VLR or external networks
- H04W 36/0022: {for transferring data sessions between adjacent core network technologies}
- H04L 65/1016: IP multimedia subsystem [IMS]
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Systems, devices, and techniques described herein relate to efficient Evolved Packet System (EPS) fallback. A method may include receiving a rejection message that indicates a rejection to set up a call through a 5th Generation (5G) network by a 5G Radio Access Network (RAN). In response to receiving the rejection message, the method may include transmitting a request to establish a dedicated bearer through a 4th Generation (4G) network. A confirmation that the second dedicated bearer has been established through the 4G network may be received within a predetermined time after transmitting the request.

## Claims

### Claim 1

A session management system, comprising:
at least one processor; and
at least one memory storing instructions, the instructions being executable by the at least one processor to perform operations comprising:
transmitting, to an Access and Mobility Management Function (AMF) in a 5th Generation (5G) network, a first request to set up a call in the 5G network;
receiving, from the AMF, a first rejection message that indicates a rejection of the first request by a 5G Radio Access Network (RAN) connected to the AMF;
in response to receiving the first rejection message, transmitting, to a Mobility Management Entity (MME), a second request to establish a first dedicated bearer through a 4th Generation (4G) network; and
after a predetermined time after transmitting the second request, transmitting an indication of a call failure to a policy control function (PCF) or a policy and charging rules function (PCRF).

### Claim 2 (depends on 1)

The session management system of claim 1, wherein the first dedicated bearer is configured to carry voice services between a User Equipment (UE) connected to a 4G RAN in the 4G network and an Internet Protocol (IP) Multimedia Subsystem (IMS) network connected to a policy control system.

### Claim 3 (depends on 1)

The session management system of claim 1, wherein the operations further comprise:
transmitting, to the AMF, a third request to set up a call in the 5G network;
receiving, from the AMF, a second rejection message that indicates a rejection of the third request by the 5G RAN;
in response to receiving the second rejection message, transmitting, to the MME, a fourth request to establish a second dedicated bearer through the 4G network; and
upon expiration of the predetermined time after transmitting the fourth request and without receiving a confirmation that the second dedicated bearer has been established, initiating call failure by transmitting an indication of the second rejection message to a policy control system.

### Claim 4 (depends on 1)

The session management system of claim 1, wherein the session management system comprises a Session Management Function (SMF) of the 5G network and a Packet Data Network (PDN) Gateway Control plane function (PGW-C) of the 4G network, and
wherein the PCF is associated with the 5G network and the PCRF is associated with the 4G network.

### Claim 5

A method performed by a session management system, the method comprising:
receiving a rejection message that indicates a rejection to set up a call in a 5th Generation (5G) network by a 5G Radio Access Network (RAN);
in response to receiving the rejection message, transmitting a request to establish a dedicated bearer through a 4th Generation (4G) network; and
after a predetermined time of transmitting the request, transmitting an indication of a call failure to a policy control function (PCF) or a policy and charging rules function (PCRF).

### Claim 6 (depends on 5)

The method of claim 5, wherein the rejection message indicates that the 5G RAN has rejected a request to set up the call.

### Claim 7 (depends on 5)

The method of claim 5, wherein the rejection message is received from an Application Management Function (AMF) in the 5G network.

### Claim 8 (depends on 5)

The method of claim 5, wherein the request to establish the dedicated bearer through the 4G network is transmitted to a Mobility Management Entity (MME).

### Claim 9 (depends on 5)

The method of claim 5, wherein the predetermined time is between 1 millisecond and 1 second.

### Claim 10 (depends on 5)

The method of claim 5, wherein the dedicated bearer is configured to carry data traffic between a User Equipment (UE) and a Data Network (DN) and comprises a 4G RAN.

### Claim 11 (depends on 10)

The method of claim 10, wherein the data traffic comprises voice services and the DN includes an Internet Protocol (IP) Multimedia Subsystem (IMS) network.

### Claim 12 (depends on 5)

The method of claim 5, wherein the session management system comprises a Session Management Function (SMF) of the 5G network and a Packet Data Network (PDN) Gateway Control plane function (PGW-C) of the 4G network.

### Claim 13

A system comprising:
at least one processor; and
at least one memory storing instructions, the instructions being executable by the at least one processor to perform operations comprising:
receiving a rejection message that indicates a rejection to set up a call in a 5th Generation (5G) network by a 5G Radio Access Network (RAN);
in response to receiving the rejection message, transmitting a request to establish a dedicated bearer through a 4th Generation (4G) network; and
after a predetermined time of transmitting the request, transmitting an indication of a call failure to a policy control function (PCF) or a policy and charging rules function (PCRF).

### Claim 14 (depends on 13)

The system of claim 13, wherein the rejection indicates that the 5G RAN has rejected a request to set up the call.

### Claim 15 (depends on 13)

The system of claim 13, wherein the rejection is received from an Application Management Function (AMF) in the 5G network.

### Claim 16 (depends on 13)

The system of claim 13, wherein the request to establish the dedicated bearer through the 4G network is transmitted to a Mobility Management Entity (MME).

### Claim 17 (depends on 13)

The system of claim 13, wherein the predetermined time is between 1 millisecond and 1 second.

### Claim 18 (depends on 13)

The system of claim 13, wherein the dedicated bearer is configured to carry data traffic between a User Equipment (UE) and a Data Network (DN) and is through a 4G RAN.

### Claim 19 (depends on 18)

The system of claim 18, wherein the data traffic comprises voice services and the DN includes an Internet Protocol (IP) Multimedia Subsystem (IMS) network.

### Claim 20 (depends on 13)

The system of claim 13, further comprising:
a Session Management Function (SMF) of the 5G network; and
a Packet Data Network (PDN) Gateway Control plane function (PGW-C) of the 4G network.