# US 12,010,552 B2 · Enhancements on 5G session management (5GSM) handling of network rejection not due to congestion control

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- Number: US 12,010,552 B2
- Document ID: US12010552B2
- Status: Granted
- Kind: B2
- Application number: 17/548,675
- Filed: 2021-12-13
- Published: 2022-08-11
- Granted: 2024-06-11
- Earliest claimed: 2021-02-08
- Assignees: Mediatek Inc.
- Applicants: Mediatek Inc.
- Inventors: Chien-Chun Huang-Fu; Bo-Hun Chen
- Web page: https://patentgrep.com/patent/US12010552B2

## CPC

- H04W 28/0908: {based on time, e.g. for a critical period only}
- H04W 76/18: Management of setup rejection or failure
- H04W 76/30: Connection release
- H04W 8/12: between location registers or mobility servers
- H04W 84/042: {Public Land Mobile systems, e.g. cellular systems}
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

A method for 5G Session Management (5GSM) handling of network rejection not due to congestion control is provided. A User Equipment (UE) receives a 5GSM reject message from a mobile communication network. The 5GSM reject message indicates a network rejection not due to congestion control. The UE associates a back-off timer with a Home Public Land Mobile Network (HPLMN) Single-Network Slice Selection Assistance Information (S-NSSAI). The UE prevents itself from sending a 5GSM request message for the same HPLMN S-NSSAI that is associated with the back-off timer.

## Claims

### Claim 1

A method, comprising:
receiving a 5G Session Management (5GSM) reject message from a mobile communication network by a User Equipment (UE), wherein the 5GSM reject message indicates a network rejection not due to congestion control;
associating a back-off timer with a serving Home Public Land Mobile Network (HPLMN) Single-Network Slice Selection Assistance Information (S-NSSAI) or a mapped HPLMN S-NSSAI based on a register of the UE, wherein the serving HPLMN S-NSSAI is a serving part of a complete S-NSSAI and the mapped HPLMN S-NSSAI is a mapped part of the complete S-NSSAI; and
preventing the UE from sending a 5GSM request message for the same HPLMN S-NSSAI that is associated with the back-off timer.

### Claim 2 (depends on 1)

The method as claimed in claim 1, wherein the 5GSM reject message is associated with a Protocol Data Unit (PDU) session, and the serving HPLMN S-NSSAI is obtained from the serving part of the complete S-NSSAI associated with the PDU session when the UE is registered in a HPLMN.

### Claim 3 (depends on 1)

The method as claimed in claim 1, wherein the 5GSM reject message is associated with a Protocol Data Unit (PDU) session, and the mapped HPLMN S-NSSAI is obtained from the mapped part of the complete S-NSSAI associated with the PDU session when the UE is registered in a Visited PLMN (VPLMN).

### Claim 4 (depends on 3)

The method as claimed in claim 3, wherein the serving part comprises a VPLMN S-NSSAI.

### Claim 5 (depends on 1)

The method as claimed in claim 1, wherein the 5GSM reject message is received when the UE is registered in a first PLMN, and the preventing of the UE from sending a 5GSM request message for the same HPLMN S-NSSAI is performed when the UE is registered in a second PLMN.

### Claim 6 (depends on 5)

The method as claimed in claim 5, wherein the first PLMN and the second PLMN are a HPLMN and one Visited PLMN (VPLMN) in an Equivalent PLMN (EPLMN) list, respectively, or are one VPLMN in the EPLMN list and the HPLMN, respectively, or are a first VPLMN and a second VPLMN which is in an EPLMN list of the first VPLMN, respectively.

### Claim 7 (depends on 6)

The method as claimed in claim 6, wherein the 5GSM reject message comprises a re-attempt indicator which indicates that re-attempt in an EPLMN is not allowed, or the 5GSM reject message does not comprise a re-attempt indicator.

### Claim 8 (depends on 1)

The method as claimed in claim 1, wherein the 5GSM reject message is a PDU SESSION ESTABLISHMENT REJECT message or a PDU SESSION MODIFICATION REJECT message, and the 5GSM request message is a PDU SESSION ESTABLISHMENT REQUEST message or a PDU SESSION MODIFICATION REQUEST message.

### Claim 9

A User Equipment (UE), comprising:
a wireless transceiver, configured to perform wireless transmission and reception to and from a mobile communication network; and
a controller, configured to receive a 5G Session Management (5GSM) reject message indicating a network rejection not due to congestion control from the mobile communication network via the wireless transceiver, associate a back-off timer with a serving Home Public Land Mobile Network (HPLMN) Single-Network Slice Selection Assistance Information (S-NSSAI) or a mapped HPLMN S-NSSAI based on a register of the UE, and prevent the UE from sending a 5GSM request message for the same HPLMN S-NSSAI that is associated with the back-off timer, wherein the serving HPLMN S-NSSAI is a serving part of a complete S-NSSAI and the mapped HPLMN S-NSSAI is a mapped part of the complete S-NSSAI.

### Claim 10 (depends on 9)

The UE as claimed in claim 9, wherein the 5GSM reject message is associated with a Protocol Data Unit (PDU) session, and the serving HPLMN S-NSSAI is obtained from the serving part of the complete S-NSSAI associated with the PDU session when the UE is registered with a HPLMN.

### Claim 11 (depends on 9)

The UE as claimed in claim 9, wherein the 5GSM reject message is associated with a Protocol Data Unit (PDU) session, and the mapped HPLMN S-NSSAI is obtained from the mapped part of the complete S-NSSAI associated with the PDU session when the UE is registered with a Visited PLMN (VPLMN).

### Claim 12 (depends on 11)

The UE as claimed in claim 11, wherein the serving part comprises a VPLMN S-NSSAI.

### Claim 13 (depends on 9)

The UE as claimed in claim 9, wherein the 5GSM reject message is received when the UE is registered in a first PLMN, and the preventing of the UE from sending a 5GSM request message for the same HPLMN S-NSSAI is performed when the UE is registered in a second PLMN.

### Claim 14 (depends on 13)

The UE as claimed in claim 13, wherein the first PLMN and the second PLMN are a HPLMN and one Visited PLMN (VPLMN) in an Equivalent PLMN (EPLMN) list, respectively, or are one VPLMN in the EPLMN list and the HPLMN, respectively, or are a first VPLMN and a second VPLMN which is in an EPLMN list of the first VPLMN, respectively.

### Claim 15 (depends on 14)

The UE as claimed in claim 14, wherein the 5GSM reject message comprises a re-attempt indicator which indicates that re-attempt in an EPLMN is not allowed, or the 5GSM reject message does not comprise a re-attempt indicator.

### Claim 16 (depends on 9)

The UE as claimed in claim 9, wherein the 5GSM reject message is a PDU SESSION ESTABLISHMENT REJECT message or a PDU SESSION MODIFICATION REJECT message, and the 5GSM request message is a PDU SESSION ESTABLISHMENT REQUEST message or a PDU SESSION MODIFICATION REQUEST message.

### Claim 17

A method, comprising:
sending a 5G Session Management (5GSM) request message to a mobile communication network by a User Equipment (UE), wherein the 5GSM request message is associated with a serving Home Public Land Mobile Network (HPLMN) Single-Network Slice Selection Assistance Information (S-NSSAI) or a mapped HPLMN S-NSSAI based on a register of the UE, wherein the serving HPLMN S-NSSAI is a serving part of a complete S-NSSAI, the mapped HPLMN S-NSSAI is a mapped part of the complete S-NSSAI, and the serving HPLMN S-NSSAI or the mapped HPLMN S-NSSAI is associated with a back-off timer;
receiving a 5GSM reject message from the mobile communication network, wherein the 5GSM reject message indicates a network rejection not due to congestion control; and
preventing the UE from sending another 5GSM request message for the same HPLMN S-NSSAI in response to the 5GSM reject message.

### Claim 18 (depends on 17)

The method as claimed in claim 17, further comprising:
in response to the 5GSM reject message comprising a 5GSM cause value of #50 “PDU session type IPv4 only allowed”, #51 “PDU session type IPv6 only allowed”, #57 “PDU session type IPv4v6 only allowed”, #58 “PDU session type Unstructured only allowed”, or #61 “PDU session type Ethernet only allowed”, preventing the UE from sending another 5GSM request message for the same HPLMN S-NSSAI until any of the following conditions is fulfilled:
the UE is registered to a new PLMN which was not in a list of equivalent PLMNs at the time when the 5GSM reject message was received;
the UE is registered to a new PLMN which was in a list of equivalent PLMNs at the time when the 5GSM reject message was received, and either the 5GSM reject message does not include a re-attempt indicator or the re-attempt indicator included in the 5GSM reject message indicates that re-attempt in an equivalent PLMN is allowed;
a PDU session type which is used to access to the HPLMN S-NSSAI is changed by the UE which subsequently requests a new PDU session type;
the UE is switched off; and
a Universal Subscriber Identity Module (USIM) is removed or an entry in a list of subscriber data for a current Stand-alone Non-Public Network (SNPN) is updated.

### Claim 19 (depends on 17)

The method as claimed in claim 17, further comprising:
in response to the 5GSM reject message comprising a 5GSM cause value of #68 “not supported SSC mode”, preventing the UE from sending another 5GSM request message for the same HPLMN S-NSSAI until any of the following conditions is fulfilled:
the UE is registered to a new PLMN which was not in a list of equivalent PLMNs at the time when the 5GSM reject message was received;
a Session and Service Continuity (SSC) mode which is used to access to the DNN and the HPLMN S-NSSAI is changed by the UE which subsequently requests a new SSC mode or no SSC mode;
the UE is switched off; and
a Universal Subscriber Identity Module (USIM) is removed or an entry in a list of subscriber data for a current Stand-alone Non-Public Network (SNPN) is updated.

### Claim 20 (depends on 17)

The method as claimed in claim 17, wherein the 5GSM request message is a PDU SESSION ESTABLISHMENT REQUEST message or a PDU SESSION MODIFICATION REQUEST message, and the 5GSM reject message is a PDU SESSION ESTABLISHMENT REJECT message or a PDU SESSION MODIFICATION REJECT message.