Method and apparatus for handling synchronization in wireless communication system
A method performed by a wireless device includes: receiving configurations for a master cell group (MCG) and a secondary cell group (SCG); applying a first timing alignment (TA) for cells in the SCG and skipping physical downlink control channel (PDCCH) monitoring for the cells in a first state while a TA timer is running, wherein the TA timer is started upon receiving a TA command including the first TA; performing state switching to a second state at a time determined based on information related to state switching time received from a network, wherein PDCCH monitoring is performed for the cells in the second state; transmitting, to the network, switching information informing the state switching; and afterwards receiving, in the second state, a TA command including a second TA upon which the TA timer is restarted; and applying the second TA for the cells while the restarted TA timer is running.
1 . A method performed by a wireless device in a wireless communication system, the method comprising:
entering a first state for one or more serving cells,
wherein the first state is a state in which the wireless device skips monitoring a control channel for the one or more serving cells;
applying a first timing advance value for the one or more serving cells in the first state while a time alignment timer is running,
wherein the time alignment timer is related to a duration during which the one or more serving cells are considered to be uplink time aligned, and
wherein the time alignment timer is started upon the wireless device receiving a timing advance command including the first timing advance value;
performing a state switching to a second state from the first state at a state switching time which is before an expiry time of the time alignment timer, based on information for the state switching time received from a network,
wherein second state is a state in which the wireless device monitors a control channel for the one or more serving cells;
transmitting, to the network in the second state, switching information informing the state switching;
receiving, from the network in the second state, a timing advance command including a second timing advance value upon which the time alignment timer is restarted, after transmitting the switching information; and
applying the second timing advance value for the one or more serving cells while the restarted time alignment timer is running.
2 . The method of claim 1 , wherein the one or more serving cells include at least one of a primary secondary cell (PSCell) or a physical uplink control channel (PUCCH) secondary cell (SCell).
3 . The method of claim 1 , wherein the one or more serving cells are included in a secondary cell group (SCG),
wherein the SCG is deactivated for the one or more serving cells in the first state, and
wherein the SCG is activated for the one or more serving cells in the second state.
4 . The method of claim 1 , wherein a periodic channel status information (CSI) reporting is skipped in the first state, and
wherein a periodic CSI reporting is performed in the second state.
5 . The method of claim 1 , wherein the wireless device stays on a dormant bandwidth part (BWP) for the one or more serving cells in the first state, and
wherein the wireless device stays on a PDCCH-configured BWP for the one or more serving cells in the second state.
6 . The method of claim 5 , further comprising:
receiving, from the network, a dormant BWP configuration comprising information informing the dormant BWP.
7 . The method of claim 5 , wherein the dormant BWP comprises at least one of:
a BWP informed by a BWP indicator in downlink control information (DCI) received from the network;
a default BWP to be switched to upon an expiry of a BWP inactivity timer;
a BWP configured to the wireless device via an RRC signalling from the network; or
a BWP determined by a media access control (MAC) entity upon an initiation of a random access procedure.
8 . The method of claim 5 , wherein the PDCCH-configured BWP comprises at least one of:
an initial BWP used for initial access before radio resource control (RRC) connection is established;
a default BWP to be switched to upon an expiry of a BWP inactivity timer;
a BWP selected by the wireless device; or
a predetermined BWP configured to the wireless device via an RRC signalling from the network.
9 . The method of claim 1 , wherein the information for the state switching time comprises an offset value which is non-negative value, and
wherein the state switching time is determined as the expiry time of the time alignment timer minus the offset value.
10 . The method of claim 1 , wherein the information for the state switching time comprises information for a switching timer value,
wherein a switching timer is started to run during the switching timer value upon the wireless device receiving the information for the state switching time, and
wherein the state switching time is an expiry time of the switching timer.
11 . The method of claim 1 , further comprising:
after restarting the time alignment timer and applying the second timing advance value for the one or more serving cells, performing a state switching to the first state from the second state.
12 . The method of claim 1 , wherein the wireless device is in communication with at least one of a user equipment, a network, or autonomous vehicles other than the wireless device.
13 . A wireless device in a wireless communication system comprising:
a transceiver;
a memory; and
at least one processor operatively coupled to the transceiver and the memory,
wherein the memory stores instructions that, based on being executed by the at least one processor, perform operations comprising:
entering a first state for one or more serving cells,
wherein the first state is a state in which the wireless device skips monitoring a control channel for the one or more serving cells;
applying a first timing advance value for the one or more serving cells in the first state while a time alignment timer is running,
wherein the time alignment timer is related to a duration during which the one or more serving cells are considered to be uplink time aligned, and
wherein the time alignment timer is started upon the wireless device receiving a timing advance command including the first timing advance value;
performing a state switching to a second state from the first state at a state switching time which is before an expiry time of the time alignment timer, based on information for the state switching time received from a network,
wherein the second state is a state in which the wireless device monitors a control channel for the one or more serving cells;
transmitting, to the network in the second state, switching information informing the state switching;
receiving, from the network in the second state, a timing advance command including a second timing advance value upon which the time alignment timer is restarted, after transmitting the switching information; and
applying the second timing advance value for the one or more serving cells while the restarted time alignment timer is running.