# US 12,225,417 B2 · Coordinated change of protocol data unit session anchors

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- Number: US 12,225,417 B2
- Document ID: US12225417B2
- Status: Granted
- Kind: B2
- Application number: 17/769,498
- Filed: 2019-10-22
- Published: 2023-05-18
- Granted: 2025-02-11
- Earliest claimed: 2019-10-22
- Assignees: Telefonaktiebolaget LM Ericsson (publ)
- Applicants: Telefonaktiebolaget LM Ericsson (publ)
- Inventors: György Miklós; Balázs Varga; János Farkas; János Harmatos
- Web page: https://patentgrep.com/patent/US12225417B2

## CPC

- H04W 36/0027: {for a plurality of data sessions of end-to-end connections, e.g. multi-call or multi-bearer end-to-end data connections}
- H04W 36/0011: {for data sessions of end-to-end connection}
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

Methods and systems for coordinated change of Protocol Data Unit (PDU) Session Anchors (PSAs) are provided. According to one embodiment, a method for coordinated change of PSAs comprises, at a node for maintaining PSA change status for PDU sessions, receiving a request for a PSA change or handover for a first PDU session having a first PSA, where the first PDU session and a second PDU session having a second PSA different from the first PSA are redundant PDU sessions with each other. If the second PDU session is undergoing a PSA change or handover, the request to change the first PDU session is denied; otherwise, the request to change the first PDU session is granted, and the second PDU session will not be allowed to be changed until the PSA change or handover for the first PDU session is complete.

## Claims

### Claim 1

A method for coordinated change of Protocol Data Unit (PDU) Session Anchors (PSAs) the method comprising:
at a node for maintaining PSA change status for PDU sessions:
receiving, from a requesting entity, a request for a PSA change for a first PDU session having a first PSA, where the first PDU session and a second PDU session are redundant PDU sessions with each other;
determining whether the PSA change for the first PDU session is temporarily prohibited;
upon determining that the PSA change for the first PDU session is temporarily prohibited,
denying the request for the PSA change for the first PDU session; and
upon determining that the PSA change for the first PDU session is not temporarily prohibited:
granting the request for the PSA change for the first PDU session;
setting a PSA change status associated with the first PDU session to indicate that the PSA change for the first PDU session is temporarily prohibited;
subsequently receiving an indication that the PSA change for the first PDU session is completed; and
setting the PSA change status associated with the first PDU session to indicate that the PSA change for the first PDU session is allowed,
wherein determining that the PSA change for the first PDU session is temporarily prohibited comprises at least one of: determining that the first PDU session is currently undergoing a handover; determining that the second PDU session is currently undergoing a handover; and/or determining that the second PDU session is currently undergoing a PSA change.

### Claim 2 (depends on 1)

The method of claim 1, wherein the PSA change status associated with the first PDU session is also associated with the second PDU session.

### Claim 3 (depends on 1)

The method of claim 1, wherein:
setting the PSA change status associated with the first PDU session to indicate that the PSA change for the first PDU session is temporarily prohibited further comprises setting a PSA change status associated with the second PDU session to indicate that a PSA change for the second PDU session is temporarily prohibited, and
setting the PSA change status associated with the first PDU session to indicate that the PSA change for the first PDU session is allowed further comprises setting the PSA change status associated with the second PDU session to indicate that the PSA change for the second PDU session is allowed.

### Claim 4 (depends on 1)

The method of claim 1, wherein the node for maintaining PSA change status for PDU sessions comprises a synchronization database function for maintaining PSA change status variables that indicate PSA change status for PDU sessions.

### Claim 5 (depends on 1)

The method of claim 1, further comprising, subsequent to denying the request for the PSA change for the first PDU session:
determining that the PSA change for the first PDU session is allowed; and
setting the PSA change status associated with the first PDU session to indicate that the PSA change is allowed; and/or
notifying the requesting entity that the PSA change for the first PDU session is now allowed.

### Claim 6 (depends on 1)

The method of claim 1, wherein a requesting entity comprises a Session Management Function (SMF) that is associated with the PSA that is being changed; and/or wherein the first node being associated with the first PDU session comprises a Radio Access Network (RAN) node; wherein optionally the RAN node comprises a New Radio Base Station (gNB).

### Claim 7 (depends on 1)

The method of claim 1, wherein the second node being associated with the second PDU session comprises a RAN node; wherein optionally the RAN node comprises a gNB.

### Claim 8

A method for coordinated change of Protocol Data Unit (PDU) Session Anchors (PSAs), the method comprising:
at a Session Management Function (SMF), node:
determining that a PSA change is needed for a first PDU session having a first PSA, where the first PDU session and a second PDU session are redundant PDU sessions with each other;
sending, to a node for maintaining PSA change status for PDU sessions, a request for the PSA change for the first PDU session;
receiving, from the node for maintaining PSA change status for PDU sessions, a response to the request for the PSA change for the first PDU session, and:
if the response to the request for the PSA change for the first PDU session indicates that the PSA change is allowed, initiating the PSA change for the first PDU session; and
if the response to the request for the PSA change for the first PDU session indicates that the PSA change is temporarily prohibited, not initiating the PSA change for the first PDU session.

### Claim 9 (depends on 8)

The method of claim 8 wherein, if the response to the request for the PSA change for the first PDU session indicates that the PSA change is temporarily prohibited, the process further comprises:
receiving a notification that the temporarily prohibited PSA change is now allowed; and
resending the request for the PSA change for the first PDU session to the node for maintaining PSA change status for PDU sessions.

### Claim 10 (depends on 8)

The method of claim 8, wherein sending the request for the PSA change for the first PDU session to the node for maintaining PSA change status for PDU sessions comprises sending the request to a core network node; or wherein sending the request for the PSA change for the first PDU session to the node for maintaining PSA change status for PDU sessions comprises sending the request to a Radio Access Network (RAN) node; wherein optionally said sending the request to the RAN node comprises sending the request to a New Radio Base Station (gNB).

### Claim 11 (depends on 8)

The method of claim 8, further comprising:
at a Session Management Function (SMF) node:
performing a PSA change for a PDU session having a first PSA; and
sending, to a node for maintaining PSA change status for PDU sessions, an indication that the PSA change for the first PDU session has completed.

### Claim 12 (depends on 11)

The method of claim 11, wherein performing the PSA change for the first PDU session having the first PSA comprises creating a new PDU session having a second PSA that is different from the first PSA; and/or
wherein the node for maintaining PSA change status for PDU sessions comprises a core network node; or
wherein the node for maintaining PSA change status for PDU sessions comprises a Radio Access Network, RAN, node; wherein optionally the RAN node comprises a New Radio Base Station, gNB.

### Claim 13

A method for coordinated change of Protocol Data Unit (PDU) Session Anchors (PSAs), the method comprising:
at a node for maintaining PSA change and handover status for PDU sessions:
receiving a request for a handover for a first PDU session having a first PSA, where the first PDU session and a second PDU session are redundant PDU sessions with each other;
determining whether the handover for the first PDU session is temporarily prohibited;
upon determining that the handover for the first PDU session is temporarily prohibited, denying the request for the handover for the first PDU session; and
upon determining that the handover for the first PDU session is not temporarily prohibited:
allowing the handover for the first PDU session;
setting a change status associated with the first PDU session to indicate that a PSA change or handover for the first PDU session is temporarily prohibited;
subsequently receiving an indication that the PSA change for the first PDU session is completed; and
setting the change status associated with the first PDU session to indicate that a PSA change for the first PDU session is allowed,
wherein determining that the handover for the first PDU session is temporarily prohibited comprises at least one of: determining that the first PDU session is currently undergoing a PSA change; determining that the second PDU session is currently undergoing a handover; and/or determining that the second PDU session is currently undergoing a PSA change.

### Claim 14 (depends on 13)

The method of claim 13, wherein the change status associated with the first PDU session is also associated with the second PDU session.

### Claim 15 (depends on 14)

The method of claim 14, wherein:
setting a change status associated with the first PDU session to indicate that a PSA change or handover for the first PDU session is temporarily prohibited further comprises setting a change status associated with the second PDU session to indicate that a PSA change or handover for the second PDU session is temporarily prohibited, and
setting a change status associated with the first PDU session to indicate that a PSA change or handover for the first PDU session is allowed further comprises setting a change status associated with the second PDU session to indicate that a PSA change or handover for the second PDU session is allowed.

### Claim 16 (depends on 13)

The method of claim 13, wherein the node for maintaining PSA change or handover status for PDU sessions comprises a synchronization database function for maintaining change status variables that indicate PSA change or handover status for PDU sessions.

### Claim 17

A method for coordinated change of Protocol Data Unit (PDU) Session Anchors (PSAs), the method comprising:
at a first node being associated with a first PDU session:
determining that a handover is needed for the first PDU session having a first PSA, where the first PDU session and a second PDU session are redundant PDU sessions with each other;
determining whether the handover for the first PDU session is temporarily prohibited;
upon a determination that the handover for the first PDU session is temporarily prohibited, postponing the handover for the first PDU session; and
upon a determination that the handover for the first PDU session is not temporarily prohibited:
setting the change status associated with the first PDU session to indicate that a PSA change or handover for the first PDU session is temporarily prohibited;
performing the handover for the second PDU session; and
setting the change status associated with the first PDU session to indicate that a PSA change or handover is allowed,
wherein determining that a PSA change or handover for the first PDU session is temporarily prohibited comprises at least one of: determining that the first PDU session is currently undergoing a PSA change; determining that the second PDU session is currently undergoing a PSA change; and determining that the second PDU session is currently undergoing a handover.

### Claim 18 (depends on 17)

The method of claim 17, wherein the first node being associated with the first PDU session comprises a Radio Access Network (RAN) node; wherein optionally the RAN node comprises a New Radio Base Station (gNB).

### Claim 19 (depends on 17)

The method of claim 17, wherein a second node being associated with the second PDU session comprises a RAN node; wherein optionally the RAN node comprises a gNB.

### Claim 20 (depends on 1)

A network node for coordinated change of Protocol Data Unit (PDU) Session Anchors (PSAs), the network node comprising processing circuitry that performs method of claim 1; wherein the network node comprises a core network node or Radio Access network (RAN) node; wherein the core network node comprises a Session Management Function (SMF); and wherein the RAN node comprises a New Radio Base station (gNB).