Method and apparatus for supporting layer-2 mobility

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

receiving, from a base station, at least one Radio Resource Control (RRC) message, wherein the at least one RRC message comprises at least one mobility configuration information;

performing a random access associated with at least one cell based on first mobility configuration information among the at least one mobility configuration information;

receiving, from the base station, a first Medium Access Control (MAC) Control Element (CE), wherein the first MAC CE comprises an identifier indicating second mobility configuration information among the at least one mobility configuration information and a field related to uplink timing advance;

in case that the field is set to a specific value, performing a random access associated with at least one cell based on the second mobility configuration information; and

in case that the field is not set to the specific value, applying an uplink timing advance based on the first MAC CE.

2 . The method of claim 1 , wherein in case that the field is not set to the specific value the field indicates that the wireless device can skip a random access associated with the second mobility configuration information.

3 . The method of claim 1 , wherein the first MAC CE is received:

while the first mobility configuration information and the second mobility configuration information are configured for the wireless device.

4 . The method of claim 3 , further comprising:

applying, based on the first MAC CE, at least one parameter of the second mobility configuration information,

wherein applying the uplink timing advance comprises applying the uplink timing advance for uplink transmission associated with at least one cell related to the second mobility configuration information.

5 . The method of claim 1 , wherein the at least one cell related to the first mobility configuration information and the second mobility configuration information is associated with a first layer-2 mobility group and a second layer-2 mobility group, respectively.

6 . The method of claim 5 , wherein receiving the first MAC CE comprises:

while the first mobility configuration information and the second mobility configuration information are configured for the wireless device:

receiving the first MAC CE; and

switching, based on the first MAC CE, from the first layer-2 mobility group to the second layer-2 mobility group.

7 . The method of claim 6 , further comprising:

while the first mobility configuration information and the second mobility configuration information are configured for the wireless device:

receiving a second MAC CE, wherein the second MAC CE comprises an identifier indicating the first mobility configuration information; and

switching, based on the second MAC CE, from the second layer-2 mobility group to the first layer-2 mobility group.

8 . The method of claim 1 , wherein receiving at least one RRC message comprises:

receiving, from the base station, a first RRC message, wherein the first RRC message comprises the first mobility configuration information; and

receiving, from the base station, a second RRC message, wherein the second RRC message comprises the second mobility configuration information.

9 . A method performed by a wireless device, the method comprising:

receiving, from a base station, at least one Radio Resource Control (RRC) message, wherein the at least one RRC message comprises at least one mobility configuration information;

while first mobility configuration information and second mobility configuration information among the at least one mobility configuration information are configured for the wireless device:

performing wireless communication via at least one cell based on the first mobility configuration information;

receiving a first Medium Access Control (MAC) Control Element (CE), wherein the first MAC CE comprises an identifier indicating the second mobility configuration information and a field related to uplink timing advance;

in case that the field is set to a specific value, performing wireless communication via at least one cell based on the second mobility configuration information, and

in case that the field is not set to the specific value, applying an uplink timing advance based on the first MAC CE.

10 . The method of claim 9 , further comprising:

skipping, based on the field not being set to the specific value in the first MAC CE, a random access associated with at least one cell related to the second mobility configuration information.

11 . The method of claim 9 , further comprising:

switching, based on the identifier comprised in the first MAC CE, from at least one cell related to the first mobility configuration information to at least one cell related to the second mobility configuration information.

12 . The method of claim 9 , wherein at least one cell related to the first mobility configuration information and the second mobility configuration information is associated with a first layer-2 mobility group and a second layer-2 mobility group, respectively.

13 . The method of claim 9 , wherein receiving the at least one RRC message comprises:

receiving, from the base station, a first RRC message, wherein the first RRC message comprises the first mobility configuration information; and

receiving, from the base station, a second RRC message, wherein the second RRC message comprises the second mobility configuration information.

14 . The method of claim 9 , further comprising:

receiving a second MAC CE, wherein the second MAC CE comprises an identifier indicating the first mobility configuration information; and

switching, based on the second MAC CE, from at least one cell related to the second mobility configuration information to at least one cell related to the first mobility configuration information.