Method for performing re-establishing RRC connection procedure and device supporting the same

1. A method performed by a wireless device in a wireless communication system, the method comprising:

configuring a master cell group (MCG) cell and a secondary cell group (SCG) cell;

detecting an MCG failure on the MCG cell,

wherein the MCG failure corresponds to one of a radio link failure on the MCG cell or handover failure;

suspending MCG bearer and MCG transmission of one or more split bearers;

maintaining SCG bearer and SCG transmission of at least one of the one or more split bearers;

constructing a message indicating a cause of the failure;

encrypting the message based on a configuration of MCG;

transmitting the message to the SCG cell via the maintained SCG transmission of the at least one of the one or more split bearers that is one type of Signaling Radio Bearers (SRB);

receiving information informing that the wireless device is allowed to select the SCG cell as a new primary cell (PCell); and

selecting the SCG cell as the new PCell of a new MCG based on the received information,

wherein the MCG cell and the SCG cell belong to different radio technologies.

2. The method of claim 1 , wherein the wireless device is configured to support dual connectivity (DC) for the MCG and the SCG.

3. The method of claim 1 , wherein the information is transmitted from the MCG.

4. The method of claim 1 , further comprising:

skipping random access channel (RACH) procedure for a new cell other than the SCG cell.

5. The method of claim 1 , wherein the wireless device communicates with at least one of a mobile terminal, a network or autonomous vehicles other than the wireless device.

6. A wireless device in a wireless communication system, the wireless device comprising:

a transceiver for transmitting or receiving a radio signal; and

a processor coupled to the transceiver,

the processor configured to:

configure a master cell group (MCG) cell and a secondary cell group (SCG) cell;

detect an MCG failure on the MCG cell,

wherein the MCG failure corresponds to one of a radio link failure on the MCG cell or handover failure;

suspend MCG bearer and MCG transmission of one or more split bearers;

maintain SCG bearer and SCG transmission of at least one of the one or more split bearers;

construct a message indicating a cause of the failure;

encrypt the message based on a configuration of MCG;

control the transceiver to transmit the message to the SCG cell via the maintained SCG transmission of the at least one of the one or more split bearers that is one type of Signaling Radio Bearers (SRB);

control the transceiver to receive information informing that the wireless device is allowed to select the SCG cell as a new primary cell (PCell); and

select the SCG cell as the new PCell of a new MCG based on the received information,

wherein the MCG cell and the SCG cell belong to different radio technologies.

7. The wireless device of claim 6 , wherein the wireless device is configured to support dual connectivity (DC) for the MCG and the SCG.

8. A processor for a wireless communication device in a wireless communication system,

wherein the processor is configured to control the wireless communication device to:

configure a master cell group (MCG) cell and a secondary cell group (SCG) cell;

detect an MCG failure on the MCG cell,

wherein the MCG failure corresponds to one of a radio link failure on the MCG cell or handover failure;

suspend MCG bearer and MCG transmission of one or more split bearers;

maintain SCG bearer and SCG transmission of at least one of the one or more split bearers;

construct a message indicating a cause of the failure;

encrypt the message based on a configuration of MCG;

transmit the message to the SCG cell via the maintained SCG transmission of the at least one of the one or more split bearers that is one type of Signaling Radio Bearers (SRB);

receive information informing that the wireless device is allowed to select the SCG cell as a new primary cell (PCell); and

select the SCG cell as the new PCell of a new MCG based on the received information,

wherein the MCG cell and the SCG cell belong to different radio technologies.