METHOD AND APPARATUS FOR UPLINK TRANSMISSION TIMING ADJUSTMENT FOR LAYER 2 MOBILITY IN MOBILE WIRELESS COMMUNICATION SYSTEM
A method and apparatus for layer 2 mobility is provided. Method for lower layer mobility includes receiving a RRCReconfigruation from the base station, receiving a TAC MAC CE in a first cell and determining Timing advance between downlink and uplink (TTA). If the type1 TAC MAC CE is received, the terminal determining Timing advance between downlink and uplink (TTA) of a second TAG of a first mobility group based on the first field (TAC) and the second field (TAG ID) and a first subcarrier spacing. If the type2 TAC MAC CE is received, the terminal determining Timing advance between downlink and uplink (TTA) of a second TAG of a second mobility group based on the first field (TAC) and the second field (TAG ID) and a third field (CMG ID field) and a second subcarrier spacing.
1 . A method by a terminal, the method comprising:
receiving, by the terminal from a base station, a radio resource control (RRC) reconfiguration message, wherein the RRC reconfiguration message comprises one or more inner RRC reconfiguration messages and one or more first identifiers;
performing, by the terminal and based on an inner RRC reconfiguration message, a first set of operations for a candidate cell associated with the inner RRC reconfiguration message, wherein the first set of operations comprises downlink synchronization;
receiving, by the terminal from the base station, a first downlink (DL) Medium Access Control (MAC) message or a second DL MAC message; and
adjusting, by the terminal and based on a timing advance command, an uplink transmission timing of a cell,
wherein the cell is:
a specific candidate cell in case that the first DL MAC message is received; and
a specific serving cell in case that the second DL MAC message is received,
wherein the first DL MAC message comprises:
a timing advance command field; and
a first identifier field,
wherein the second DL MAC message comprises:
a timing advance command field; and
a second identifier field,
wherein the specific candidate cell is determined based on the first identifier indicated in the first identifier field, and
wherein the specific serving cell is determined based on a second identifier indicated in the second identifier field.
2 . The method of claim 1 ,
wherein each of the one or more inner RRC reconfiguration messages is associated with at least one candidate cell.
3 . The method of claim 1 ,
wherein each of the one or more first identifiers is associated with one of the one or more inner RRC reconfiguration messages.
4 . The method of claim 1 ,
wherein an amount of uplink transmission timing of the specific candidate cell is determined based on the timing advance command field in the first DL MAC message.
5 . The method of claim 4 ,
wherein the amount of uplink transmission timing of the specific candidate cell is further determined based on a specific timing advance command offset.
6 . The method of claim 5 ,
wherein the specific timing advance command offset is indicated in a specific inner RRC reconfiguration message.
7 . The method of claim 1 ,
wherein an amount of uplink transmission timing of the specific serving cell is determined based on the timing advance command field in the second DL MAC message.
8 . The method of claim 7 ,
wherein the amount of uplink transmission timing of the specific serving cell is further determined based on a specific timing advance command offset.
9 . The method of claim 8 ,
wherein the specific timing advance command offset is indicated in system information.
10 . The method of claim 1 ,
wherein the first set of operations further comprises measuring a Synchronization Signal/Physical Broadcast Channel (SSB) of the candidate cell based on a parameter indicating an absolute frequency of SSB comprised in the inner RRC reconfiguration message associated with the candidate cell.
11 . The method of claim 1 ,
wherein the first set of operations further comprises determining a pathloss of SSB of the candidate cell.
12 . The method of claim 1 ,
wherein the first set of operations further comprises receiving Mater Information Block of the candidate cell based on one or more parameters comprised in the inner RRC reconfiguration message associated with the candidate cell.
13 . The method of claim 12 ,
wherein the one or more parameters comprised in the inner RRC reconfiguration message associated with the candidate cell comprises:
a parameter indicating a Synchronization Signal/Physical Broadcast Channel (SSB) position in burst; and
a parameter indicating an absolute frequency of SSB.
14 . The method of claim 1 , further comprising:
after the receiving the RRC reconfiguration message in a serving cell, receiving, in the serving cell, by the terminal, a Physical Downlink Control Channel (PDCCH) order, wherein the PDCCH order comprises:
a random access preamble index field; and
a Synchronization Signal/Physical Broadcast Channel (SSB) field.
15 . The method of claim 14 , further comprising:
performing, by the terminal, a preamble transmission in a specific candidate cell that is different from the serving cell based on that:
the PDCCH order comprises a specific field; and
the specific field indicates a specific value.
16 . The method of claim 15 ,
wherein the candidate cell is indicated by a third identifier indicated in the PDCCH order.
17 . The method of claim 16 ,
wherein the third identifier is associated with the candidate cell.
18 . The method of claim 15 ,
wherein a Random Access Channel (RACH) occasion for the preamble transmission is determined based on:
the SSB field in the PDCCH order; and
a parameter about a number of SSB per RACH occasion comprised in the inner RRC reconfiguration message associated with the candidate cell.
19 . The method of claim 1 , wherein:
the first identifier is associated with one or more candidate cells; and
the second identifier is associated with one or more serving cells.
20 . A terminal comprising:
a transceiver,
a memory, and
a controller coupled to the transceiver and the memory, wherein the controller is configured to cause the terminal to:
receive, from a base station, a radio resource control (RRC) reconfiguration message, wherein the RRC reconfiguration message comprises one or more inner RRC reconfiguration messages and one or more first identifiers;
perform, based on an inner RRC reconfiguration message, a first set of operations for a candidate cell associated with the inner RRC reconfiguration message, wherein the first set of operations comprises downlink synchronization;
receive, from the base station, a first downlink (DL) Medium Access Control (MAC) message or a second DL MAC message; and
adjust, based on a timing advance command, an uplink transmission timing of a cell,
wherein the cell is:
a specific candidate cell in case that the first DL MAC message is received; and
a specific serving cell in case that the second DL MAC message is received,
wherein the first DL MAC message comprises:
a timing advance command field; and
a first identifier field,
wherein the second DL MAC message comprises:
a timing advance command field; and
a second identifier field,
wherein the specific candidate cell is determined based on a first identifier indicated in the first identifier field, and
wherein the specific serving cell is determined based on a second identifier indicated in the second identifier field.