Radio station, radio terminal, and synchronization timer control method in radio comunication system

Abstract

A radio station, a radio terminal, and a method for synchronization timer control are provided that can reduce a delay as much as possible until uplink signal resynchronization is done in a case where a plurality of cell groups exist. In a radio communication system having a function of using a plurality of radio resources corresponding to a plurality of cells, respectively, for communication between a radio station (10) and a radio terminal (20), the radio terminal is provided with a plurality of synchronization timers for determining whether or not uplink signals in individual cell groups are in synchronization, wherein the synchronization timers are provided respectively for the plurality of cell groups each including at least one cell, and at the radio terminal (20), uplink-signal transmission on the cells included in a second cell group is controlled depending on a state of a first synchronization timer provided correspondingly for a first cell group including a specific cell and on a state of a second synchronization timer provided correspondingly for the second cell group other than the first cell group, wherein the first synchronization timer and the second synchronization timer are controlled independently.

1 - 27 . (canceled) 
     
     
         28 . A radio terminal comprising:
 at least one processor configured to aggregate a first cell group with a second cell group, wherein the first cell group includes a first cell on which a first Physical Uplink Control Channel (PUCCH) is transmitted and the second cell group includes a second cell on which a second PUCCH is transmitted;   a first timer associated with the first cell group, wherein the first timer is used to control whether uplink transmission of the radio terminal in at least one of serving cells of the first cell group is synchronized; and   a second timer associated with the second cell group, wherein the second timer is used to control whether uplink transmission of the radio terminal in at least one of serving cells of the second cell group is synchronized, wherein   the radio terminal does not perform the uplink transmission except for a random access preamble transmission by the radio terminal in at least one of serving cells of the first cell group when the first timer expires, and   the radio terminal does not perform the uplink transmission except for a random access preamble transmission by the radio terminal in at least one of serving cells of the second cell group when the first timer expires.   
     
     
         29 . The radio terminal according to  claim 28 , wherein expiry of the first timer associated with the first cell group does not affect an operation for the second timer associated with the second cell group. 
     
     
         30 . The radio terminal according to  claim 29 , wherein the radio terminal further comprises:
 a receiver configured to receive at least one of a first timing advance command and a second timing advance command, wherein   the at least one processor is further configured to:
 start or restart the first timer when the first timing advance command is received, and 
 start or restart the second timer when the second timing advance command is received. 
   
     
     
         31 . A control method in a radio terminal configured to aggregate a first cell group with a second cell group, wherein the first cell group includes a first cell on which a first Physical Uplink Control Channel (PUCCH) is transmitted and the second cell group includes a second cell on which a second PUCCH is transmitted, the control method comprising:
 controlling whether uplink transmission of the radio terminal in at least one of serving cells of the first cell group is synchronized, by using a first timer associated with the first cell group;   controlling whether uplink transmission of the radio terminal in at least one of serving cells of the second cell group is synchronized, by using a second timer associated with the second cell group, wherein   the radio terminal does not perform the uplink transmission except for a random access preamble transmission by the radio terminal in at least one of serving cells of the first cell group when the first timer expires, and   the radio terminal does not perform the uplink transmission except for a random access preamble transmission by the radio terminal in at least one of serving cells of the second cell group when the first timer expires.   
     
     
         32 . The method according to  claim 31 , wherein expiry of the first timer associated with the first cell group does not affect an operation for the second timer associated with the second cell group. 
     
     
         33 . The method according to  claim 31 , the method further comprises:
 receiving at least one of a first timing advance command and a second timing advance command;   starting or restarting the first timer when the first timing advance command is received; and   starting or restarting the second timer when the second timing advance command is received.