# US 2019/0174371 A1 · Method for establishing/releasing a mac (medium access control) entity in a wireless communication system and a device therefor

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- Number: US 2019/0174371 A1
- Document ID: US20190174371A1
- Status: Published application
- Kind: A1
- Application number: 16/255,532
- Filed: 2019-01-23
- Published: 2019-06-06
- Earliest claimed: 2013-04-05
- Assignees: LG Electronics Inc.
- Applicants: LG Electronics Inc.
- Inventors: Sunyoung Lee; Sungjun Park; Seungjune Yi
- Web page: https://patentgrep.com/patent/US20190174371A1

## CPC

- H04W 36/0072: {of resource information of target access point}
- H04W 36/04: Reselecting a cell layer in multi-layered cells
- H04W 76/34: Selective release of ongoing connections
- H04W 16/32: Hierarchical cell structures
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

In a wireless communication system, a user equipment, already configured with a first medium access control (MAC) entity for a master cell group (MCG) associated with a master base station, capable of configuring a secondary cell group (SCG) associated with a secondary base station based on a radio resource control (RRC) message received from the master base station. The user equipment can configure a second MAC entity for the newly configured SCG. Through a second RRC message from the master base station, the user equipment can then add a new SCG cell to the SCG, where the second MAC entity is commonly configured for one or more secondary SCG cells belonging to the SCG.

## Claims

### Claim at position 1

1-16. (canceled)

### Claim 17

A method for a user equipment (UE) operating in a wireless communication system comprising a master base station (BS) and a secondary BS, the UE configured with a first MAC entity for a master cell group (MCG) associated with the master BS, the method comprising:
receiving, from the master BS, a first Radio Resource Control (RRC) message via a serving cell of the MCG for configuration of a new secondary cell group (SCG) associated with the secondary BS,
configuring, by the UE, a second MAC entity for the new SCG, according to the first RRC message, in addition to the previously configured first MAC entity, when a second MAC entity is not already configured for the UE,
receiving, from the master BS, a second RRC message for addition of a new SCG cell to the SCG; and
adding, by the UE, the new SCG cell to the SCG according to the second RRC message,
wherein the second MAC entity is commonly configured for one or more secondary cells, including the new SCG cell, belonging to the SCG.

### Claim 18 (depends on 17)

The method according to claim 17 further comprising:
receiving, by the UE from the master BS, a third RRC message for removal of the SCG; and
releasing, by the UE, the second MAC entity for the SCG according to the third RRC message.

### Claim 19 (depends on 18)

The method according to claim 18 further comprising:
remapping a bearer to the first MAC entity, previously mapped to the second MAC entity, when releasing the second MAC entity.

### Claim 20

A user equipment (UE) in a wireless communication system comprising a master base station (BS) and a secondary BS, the UE configured with a first MAC entity for a master cell group (MCG) associated with the master BS, the UE comprising:
a transmitter and a receiver; and
a processor, operatively coupled to the transmitter and the receiver, configured to:
control the receiver to receive, from the master BS, a first Radio Resource Control (RRC) message via a serving cell of the MCG,
configure a new secondary cell group (SCG), associated with the secondary BS, according to the RRC message,
configure a second MAC entity for the new SCG, according to the first RRC message, in addition to the previously established first MAC entity, when a second MAC entity is not already configured for the UE,
control the receiver to receive, from the master BS, a second RRC message for addition of a new SCG cell to the SCG; and
add the new SCG cell to the SCG according to the second RRC message,
wherein the second MAC entity is commonly configured for one or more secondary cells, including the new SCG cell, belonging to the SCG.

### Claim 21 (depends on 20)

The UE according to claim 20, wherein the processor is further configured to:
control the receiver to receive, from the master BS, a third RRC message, and
remove the SCG and release the second MAC entity based on the third RRC message.

### Claim 22 (depends on 21)

The UE according to claim 21, wherein the processor is further configured to:
remap a bearer to the first MAC entity, previously mapped to the second MAC entity, when the processor releases the second MAC entity.