# US 12,225,380 B2 · Method and apparatus of supporting lossless PDCP version change in next-generation mobile communication system

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- Number: US 12,225,380 B2
- Document ID: US12225380B2
- Status: Granted
- Kind: B2
- Application number: 18/449,292
- Filed: 2023-08-14
- Published: 2023-12-14
- Granted: 2025-02-11
- Earliest claimed: 2018-08-08
- Assignees: Samsung Electronics Co., Ltd.
- Applicants: Samsung Electronics Co., Ltd.
- Inventors: Donggun Kim
- Web page: https://patentgrep.com/patent/US12225380B2

## CPC

- H04L 1/1835: {Buffer management}
- H04W 12/106: Packet or message integrity
- H04L 1/1671: {the supervisory signal being transmitted together with control information}
- H04L 5/0055: {Physical resource allocation for ACK/NACK (for physical mapping arrangements in ARQ protocols H04L1/1861)}
- H04L 47/32: by discarding or delaying data units, e.g. packets or frames
- H04L 69/22: Parsing or analysis of headers
- H04W 12/037: of the control plane, e.g. signalling traffic
- H04W 12/0433: Key management protocols
- H04W 36/00698: {using different RATs}
- H04W 36/06: Reselecting a communication resource in the serving access point
- H04W 76/30: Connection release
- H04W 76/22: Manipulation of transport tunnels
- H04W 76/34: Selective release of ongoing connections
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- 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 and terminal are provided in which a radio resource control (RRC) message is received which includes information indicating a change from a first packet data convergence protocol (PDCP) to a second PDCP entity. It is identified whether the first PDCP entity is changed based on the information indicating the change. Data with a PDCP sequence number for the first PDCP entity is processed as new data for the second PDCP entity, in case that the first PDCP entity is changed. The first PDCP entity is released. A new PDCP header associated with the data is configured. The data is encrypted with a new security key. The PDCP sequence number of the first PDCP entity is greater than or equal to the PDCP sequency number of data for which successful transmission is not acknowledged from a radio link control (RLC) entity.

## Claims

### Claim 1

A method performed by a terminal in a wireless communication system, the method comprising:
receiving, from a base station, a radio resource control (RRC) message including information indicating a change from a first packet data convergence protocol (PDCP) entity for a bearer to a second PDCP entity for the bearer, the first PDCP entity and the second PDCP entity being in the terminal;
identifying whether the first PDCP entity for the bearer is changed to the second PDCP entity for the bearer based on the information indicating the change;
processing data with a PDCP sequence number for the first PDCP entity as new data for the second PDCP entity, in case that the first PDCP entity for the bearer is changed to the second PDCP entity for the bearer;
releasing the first PDCP entity;
configuring a new PDCP header associated with the data; and
encrypting the data with a new security key,
wherein the PDCP sequence number for the first PDCP entity is greater than or equal to the PDCP sequence number of data for which successful transmission is not acknowledged from a radio link control (RLC) entity.

### Claim 2 (depends on 1)

The method of claim 1, wherein the data includes at least one PDCP service data unit (SDU).

### Claim 3 (depends on 1)

The method of claim 1, further comprising:
delivering the data to a lower layer entity.

### Claim 4 (depends on 3)

The method of claim 3, wherein:
the lower layer entity corresponds to an LTE RLC entity, and
the second PDCP entity corresponding to the NR PDCP entity and the LTE RLC entity are associated with the bearer.

### Claim 5 (depends on 3)

The method of claim 3, wherein, in case that the first PDCP entity corresponds to a NR PDCP entity and the second PDCP entity corresponds to a LTE PDCP entity:
the lower layer entity corresponds to an LTE RLC entity, and
the second PDCP entity corresponding to the LTE PDCP entity and the LTE RLC entity are associated with the bearer.

### Claim 6 (depends on 1)

The method of claim 1, further comprising:
discarding an RLC packet data unit (PDU) being stored in an RLC entity associated with the first PDCP entity.

### Claim 7 (depends on 1)

The method of claim 1, wherein the RRC message includes information for releasing the first PDCP entity for the bearer and information for establishing the second PDCP entity for the bearer.

### Claim 8 (depends on 1)

The method of claim 1, wherein a PDCP reordering time value is set to infinity in case that an acknowledge mode (AM) RLC bearer is configured for the terminal.

### Claim 9 (depends on 1)

The method of claim 1, further comprising:
performing at least one of an integrity protection, a ciphering, or a PDCP header generation for the data.

### Claim 10 (depends on 1)

The method of claim 1, wherein:
the first PDCP entity corresponds to a long term evolution (LTE) PDCP entity,
the second PDCP entity corresponds to a new radio (NR) PDCP entity, and
the bearer includes signaling radio bearer (SRB) and data radio bearer (DRB).

### Claim 11

A terminal in a wireless communication system, the terminal comprising:
a transceiver; and
a controller coupled with the transceiver and configured to:
receive, from a base station, a radio resource control (RRC) message including information indicating a change from a first packet data convergence protocol (PDCP) entity for a bearer to a second PDCP entity for the bearer, the first PDCP entity and the second PDCP entity being in the terminal,
identify whether the first PDCP entity for the bearer is changed to the second PDCP entity for the bearer based on the information indicating the change,
process data with a PDCP sequence number for the first PDCP entity as new data for the second PDCP entity in case that the first PDCP entity for the bearer is changed to the second PDCP entity for the bearer,
release the first PDCP entity,
configure a new PDCP header associated with the data, and
encrypt the data with a new security key,
wherein the PDCP sequence number for the first PDCP entity is greater than or equal the PDCP sequence number of data for which successful transmission is not acknowledged from a radio link control (RLC) entity.

### Claim 12 (depends on 11)

The terminal of claim 11, wherein the data includes at least one PDCP service data unit (SDU).

### Claim 13 (depends on 11)

The terminal of claim 11, wherein the controller is further configured to deliver the data to a lower layer entity.

### Claim 14 (depends on 13)

The terminal of claim 13, wherein:
the lower layer entity corresponds to an LTE RLC entity, and
the second PDCP entity corresponding to the NR PDCP entity and the LTE RLC entity are associated with the bearer.

### Claim 15 (depends on 13)

The terminal of claim 13, wherein, in case that the first PDCP entity corresponds to an NR PDCP entity and the second PDCP entity corresponds to an LTE PDCP entity:
the lower layer entity corresponds to an LTE RLC entity, and
the second PDCP entity corresponding to the LTE PDCP entity and the LTE RLC entity are associated with the bearer.

### Claim 16 (depends on 11)

The terminal of claim 11, wherein the controller is further configured to discard an RLC packet data unit (PDU) being stored in an RLC entity associated with the first PDCP entity.

### Claim 17 (depends on 11)

The terminal of claim 11, wherein the RRC message includes information for releasing the first PDCP entity for the bearer and information for establishing the second PDCP entity for the bearer.

### Claim 18 (depends on 11)

The terminal of claim 11, wherein a PDCP reordering time value is set to infinity in case that an acknowledge mode (AM) RLC bearer is configured for the terminal.

### Claim 19 (depends on 11)

The terminal of claim 11, wherein the controller is further configured to perform at least one of an integrity protection, a ciphering, or a PDCP header generation for the data.

### Claim 20 (depends on 11)

The terminal of claim 11, wherein:
the first PDCP entity corresponds to a long term evolution (LTE) PDCP entity,
the second PDCP entity corresponds to a new radio (NR) PDCP entity, and
the bearer includes signaling radio bearer (SRB) and data radio bearer (DRB).