# US 11,122,477 B2 · User plane function (UPF) duplication based make before break handover

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- Number: US 11,122,477 B2
- Document ID: US11122477B2
- Status: Granted
- Kind: B2
- Application number: 16/284,701
- Filed: 2019-02-25
- Published: 2019-08-29
- Granted: 2021-09-14
- Earliest claimed: 2018-02-26
- Assignees: QUALCOMM Incorporated
- Applicants: QUALCOMM Incorporated
- Inventors: Xipeng Zhu; Luis Fernando Brisson Lopes; Gavin Bernard Horn; Karthika Paladugu
- Web page: https://patentgrep.com/patent/US11122477B2

## CPC

- H04W 36/026: {Multicasting of data during hand-off}
- H04L 47/34: ensuring sequence integrity, e.g. using sequence numbers
- H04W 36/0016: {Hand-off preparation specially adapted for end-to-end data sessions}
- H04W 36/0033: {with transfer of context information}
- H04W 36/0066: {of control information between different types of networks in order to establish a new radio link in the target network}
- H04W 36/0077: {of access information of target access point}
- H04W 76/12: Setup of transport tunnels
- H04W 80/08: Upper layer protocols {(network arrangements or communication protocols for networked applications H04L67/00)}
- H04W 36/0235: {by transmitting sequence numbers, e.g. SN status transfer}
- 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

Methods for performing a handover in wireless communications for a user plane function (UPF) are disclosed. In an aspect, the method includes establishing a tunnel between the UPF and a target base station based on information in a path switch preparation request for a make before break handover of a user equipment (UE) from a source base station to the target base station, the path switch preparation request being received in response to a request originating by the target base station. The method further includes bi-casting a downlink data packet unit (PDU) to a source base station and to the target base station with a same sequence number (SN) in a tunnel protocol, receiving PDUs from the source base station and the target base station with corresponding PDUs having the same SNs in the tunnel protocol and discarding received duplicate PDUs based on the SNs in the tunnel protocol.

## Claims

### Claim 1

A method of handover in wireless communication for a user equipment (UE) comprising:
transmitting, via a first radio or a second radio of the UE, a connection reconfiguration complete message to a target base station for completing a make before break handover of a user equipment (UE) from a source base station to a target base station; and
for uplink transmissions, subsequent to transmitting the connection reconfiguration complete message,
transmitting, via the first radio, a first packet data unit (PDU) to the source base station;
transmitting, via the second radio, a second PDU to the target base station,
wherein the first PDU and the second PDU have a same sequence number (SN); and
for downlink transmissions, subsequent to transmitting the connection reconfiguration complete message,
receiving, via the first radio, one or more PDUs from the source base station, each received PDU having at least one corresponding SN;
receiving, via the second radio, one or more PDUs from the target base station, each received PDU having at least one corresponding SN;
deciphering the received one or more PDUs from the source base station and the target base station respectively and storing the received one or more PDUs in a buffer;
discarding duplicative PDUs in the buffer based on the at least one corresponding SN for each received PDU; and
re-ordering remaining PDUs based on the at least one corresponding SN.

### Claim 2 (depends on 1)

The method of claim 1, wherein the at least one corresponding SN for each PDU is a packet data convergence protocol (PDCP) SN.

### Claim 3 (depends on 1)

The method of claim 1, further comprising delivering a payload of the re-ordered remaining PDUs to upper layer.

### Claim 4 (depends on 1)

The method of claim 1, wherein the first PDU includes a source base station identifier and the second PDU includes a target base station identifier.

### Claim 5 (depends on 1)

The method of claim 1, wherein each of the first PDU and the second PDU includes a target base station identifier and a source base station identifier.

### Claim 6

A method of handover in wireless communication for a target base station comprising:
receiving, from a source base station, a sequence number (SN) transfer message including a delta between a SN in a first protocol and a SN in a second protocol;
transmitting, to an access and mobility function/session management function (AMF/SMF) entity, a path switch preparation request for a make before break handover for a user equipment (UE) from the source base station to the target base station, the path switch preparation request including target base station tunnel information and configured to trigger a user plane function (UPF) to transmit packet data units (PDUs) for the UE to both the target base station and the source base station during the handover;
receiving, from the AMF/SMF entity, a path switch preparation response including UPF tunnel information; and
establishing a tunnel between the target base station and the UPF using the UPF tunnel information.

### Claim 7 (depends on 6)

The method of claim 6, further comprising:
receiving, from the UPF, one or more packet data units (PDUs) via the tunnel, each PDU having at least one corresponding sequence number (SN) in the second protocol;
receiving, from the source base station, one or more PDUs, each PDU having at least one corresponding SN in the second protocol;
deciphering the received one or more PDUs from the UPF and the source base station respectively and storing the received one or more PDUs in a buffer;
discarding duplicative PDUs in the buffer based on the at least one corresponding SN in the second protocol;
converting, for each of the remaining PDUs, the at least one corresponding SN in the second protocol to a SN in the first protocol;
re-ordering the converted PDUs based on the at least one corresponding SN in the first protocol; and
transmitting, to the UE, the re-ordered PDUs.

### Claim 8 (depends on 7)

The method of claim 7, wherein the at least one corresponding SN is at least one of a packet data convergence protocol (PDCP) SN, a GTP-U PDU SN, or a flow specific SN, and wherein the corresponding SN is generated by the source base station and the UPF based on the PDCP SN.

### Claim 9 (depends on 6)

The method of claim 6, further comprising:
receiving, from the source base station, one or more PDUs, each PDU having at least one corresponding SN in the first protocol;
receiving, from the UE, one or more PDUS, each PDU having at least one corresponding SN in the first protocol;
deciphering the received one or more PDUs from the source base station and the UE respectively and storing the received one or more PDUs in a buffer;
discarding duplicative PDUs in the buffer based on the at least one corresponding SN in the first protocol;
converting, for each of the remaining PDUs having at least one corresponding SN in the first protocol to a SN in the second protocol;
re-ordering the converted PDUs based on the at least one corresponding SN in the second protocol; and
transmitting, to the UPF, the re-ordered PDUs.

### Claim 10 (depends on 6)

The method of claim 6, wherein the corresponding SN is a packet data convergence protocol (PDCP) SN.