Method and apparatus for supporting handover of user equipment in mobile communication system

Abstract

Defined is a handover procedure of a User Equipment (UE) for which multiple UpLink (UL) carriers requiring different UL Timing Advances (TAs) are aggregated in a mobile communication system. The handover procedure includes admitting execution of handover to a target cell of the UE at the request of a source cell, setting radio resource information to be used by the UE in the target cell and transmitting the set radio resource information to the source cell, determining whether a random access procedure, which is executed, among the multiple UL carriers, with a reference UL carrier or with an UL carrier to which the same UL TA as that of the reference UL carrier is applied, has been completed, and determining that a handover procedure of the UE has been successfully completed if the random access procedure has been completed, and determining that the handover procedure of the UE has failed if the random access procedure fails.

1 . A method for supporting handover of a User Equipment (UE) for which multiple UpLink (UL) carriers are aggregated in a mobile communication system, the method comprising:
 admitting execution of handover to a target cell of the UE at the request of a source cell;   setting radio resource information to be used by the UE in the target cell and transmitting the set radio resource information to the source cell;   determining whether a random access procedure, which is executed, among the multiple UL carriers, with a reference UL carrier or with an UL carrier to which the same UL Timing Advance (TA) as that of the reference UL carrier is applied, has been completed; and   determining that a handover procedure of the UE has been successfully completed if the random access procedure has been completed, and determining that the handover procedure of the UE has failed if the random access procedure fails.   
     
     
         2 . The method of  claim 1 , further comprising, after completion of the handover procedure, receiving UL data from the UE through UL carriers for which UL TAs have been acquired by completion of the random access procedure. 
     
     
         3 . A method for performing handover by a User Equipment (UE) for which multiple UpLink (UL) carriers are aggregated in a mobile communication system, the method comprising:
 receiving a handover command message and executing multiple random access procedures for the multiple UL carriers;   determining whether a random access procedure, which is executed, among the multiple UL carriers, with a reference UL carrier or with an UL carrier to which the same UL Timing Advance (TA) as that of the reference UL carrier is applied, has been completed; and   determining that a handover procedure of the UE has been successfully completed and transmitting a handover confirm message to the target cell if the random access procedure has been completed, and determining that the handover procedure of the UE has failed and performing a connection reestablishment procedure to one of neighboring cells if the random access procedure fails.   
     
     
         4 . The method of  claim 1 , wherein the reference UL carrier is:
 set to a reference UL carrier in the source cell prior to handover;   set to an UL carrier linked with a reference DownLink (DL) carrier in the source cell prior to handover;   indicated by the handover command message;   set to an UL carrier linked with a DL carrier explicitly indicated by the handover command message; or   set to an UL carrier for which an UL TA has been first acquired according to the random access procedure.   
     
     
         5 . The method of  claim 3 , further comprising, after completion of the handover procedure, transmitting UL data to the target cell through UL carriers for which UL TAs have been acquired by completion of the random access procedures. 
     
     
         6 . The method of  claim 3 , wherein the multiple random access procedures are executed simultaneously or sequentially. 
     
     
         7 . The method of  claim 3 , further comprising releasing or deactivating UL carriers failing in the random access procedures from the multiple UL carriers. 
     
     
         8 . The method of  claim 1 , wherein the handover command message comprises at least one of frequency information of the multiple UL carriers, sync identifications (IDs) of the multiple UL carriers, an indicator indicating the reference UL carrier, and reserved Packet Random Access Channel (PRACH) resource and Random Access Channel (RACH) preamble for the random access procedures of the UE. 
     
     
         9 . An apparatus for supporting handover of a User Equipment (UE) for which multiple UpLink (UL) carriers are aggregated in a mobile communication system, the apparatus comprising:
 a handover controller for admitting execution of handover to a target cell of the UE at the request of a source cell;   a radio resource manager for setting radio resource information to be used by the UE in the target cell and transmitting the set radio resource information to the source cell; and   a message generator/interpreter for generating and interpreting a message transmitted and received with the source cell or the UE, and transmitting the corresponding result to the handover controller or the radio resource manager,   wherein the handover controller determines whether a random access procedure, which is executed, among the multiple UL carriers, with a reference UL carrier or with an UL carrier to which the same UL Timing Advance (TA) as that of the reference UL carrier is applied, has been completed, determines that a handover procedure of the UE has been successfully completed if the random access procedure has been completed, and determines that the handover procedure of the UE has failed if the random access procedure fails.   
     
     
         10 . The apparatus of  claim 9 , further comprising a radio transceiver for transmitting a message generated by the message generator/interpreter to the UE and receiving data from the UE,
 wherein the radio transceiver, after completion of the handover procedure, receives UL data from the UE through UL carriers for which UL TAs have been acquired according to the random access procedure.   
     
     
         11 . A User Equipment (UE) for which multiple UpLink (UL) carriers are aggregated in a mobile communication system, the UE comprising:
 a radio transceiver for transmitting and receiving a message for executing multiple random access procedures for the multiple UL carriers;   a message generator/analyzer for generating and analyzing the message transmitted and received by the radio transceiver; and   a random access procedure executor for executing the multiple random access procedures for the multiple UL carriers,   wherein the random access procedure executor determines whether a random access procedure, which is executed, among the multiple UL carriers, with a reference UL carrier or with an UL carrier to which the same UL Timing Advance (TA) as that of the reference UL carrier is applied, has been completed, determines that a handover procedure of the UE has been successfully completed and transmits a handover confirm message to the target cell if the random access procedure has been completed, and determines that the handover procedure of the UE has failed and performs a connection reestablishment procedure to one of neighboring cells if the random access procedure fails.   
     
     
         12 . The UE of  claim 11 , wherein the reference UL carrier is:
 set to a reference UL carrier in the source cell prior to handover;   set to an UL carrier linked with a reference DownLink (DL) carrier in the source cell prior to handover;   indicated by the handover command message;   set to an UL carrier linked with a DL carrier explicitly indicated by the handover command message; or   set to an UL carrier for which an UL TA has been first acquired according to the random access procedure.   
     
     
         13 . The UE of  claim 11 , wherein the radio transceiver, after completion of the handover procedure, transmits UL data to the target cell through UL carriers for which UL TAs have been acquired by completion of the random access procedures. 
     
     
         14 . The UE of  claim 11 , wherein the random access procedure executor executes the multiple random access procedures simultaneously or sequentially. 
     
     
         15 . The UE of  claim 11 , wherein the random access procedure executor releases or deactivates UL carriers failing in the random access procedures from the multiple UL carriers. 
     
     
         16 . The UE of  claim 11 , wherein the handover command message comprises at least one of frequency information of the multiple UL carriers, sync identifications (IDs) of the multiple UL carriers, an indicator indicating the reference UL carrier, and reserved Packet Random Access Channel (PRACH) resource and Random Access Channel (RACH) preamble for the random access procedures of the UE. 
     
     
         17 . A method for supporting handover of a User Equipment (UE) for which multiple UpLink (UL) carriers are aggregated in a mobile communication system, the method comprising:
 admitting execution of handover to a target cell of the UE at the request of a source cell;   setting radio resource information to be used by the UE in the target cell and transmitting the set radio resource information to the source cell;   determining whether all of multiple random access procedures for the multiple UL carriers have been completed;   determining that a handover procedure of the UE has been successfully completed if all of the multiple random access procedures have been completed, and determining that the handover procedure of the UE has failed if at least one of the multiple random access procedures fails.   
     
     
         18 . The method of  claim 17 , wherein further comprising receiving a handover failure message from the UE through an UL carrier for which a random access procedure among the multiple random access procedures has been completed, if it is determined that the handover procedure of the UE has failed. 
     
     
         19 . A method for performing handover by a User Equipment (UE) for which multiple UpLink (UL) carriers are aggregated in a mobile communication system, the method comprising:
 receiving a handover command message and executing multiple random access procedures for the multiple UL carriers;   determining whether all of multiple random access procedures for the multiple UL carriers have been completed;   determining that a handover procedure of the UE has been successfully completed and transmitting a handover confirm message to the target cell if all of the multiple random access procedures have been completed, and   determining that the handover procedure of the UE has failed and performing a connection reestablishment procedure to one of neighboring cells if at least one of the multiple random access procedures fails.   
     
     
         20 . The method of  claim 19 , further comprising transmitting a handover failure message to the target cell through an UL carrier for which a random access procedure among the multiple random access procedures has been completed, if determining that the handover procedure of the UE has failed. 
     
     
         21 . The method of  claim 17 , wherein the handover command message comprises at least one of frequency information of the multiple UL carriers, sync identifications (IDs) of the multiple UL carriers, an indicator indicating the reference UL carrier, and reserved Packet Random Access Channel (PRACH) resource and Random Access Channel (RACH) preamble for the random access procedures of the UE. 
     
     
         22 . An apparatus for supporting handover of a User Equipment (UE) for which multiple UpLink (UL) carriers are aggregated in a mobile communication system, the apparatus comprising:
 a handover controller for admitting execution of handover to a target cell of the UE at the request of a source cell;   a radio resource manager for setting radio resource information to be used by the UE in the target cell;   a message generator/interpreter for generating and interpreting a message transmitted and received with the source cell or the UE, and transmitting the corresponding result to the handover controller or the radio resource manager,   wherein the handover controller determines that a handover procedure of the UE has been successfully completed if all of the multiple random access procedures have been completed, and determines that the handover procedure of the UE has failed if at least one of the multiple random access procedures fails.   
     
     
         23 . The apparatus of  claim 22 , further comprising a radio transceiver for transmitting a message generated by the message generator/interpreter to the UE and receiving data from the UE,
 wherein the radio transceiver receives a handover failure message from the UE through an UL carrier for which a random access procedure among the multiple random access procedures has been completed, if the handover procedure has failed.   
     
     
         24 . A User Equipment (UE) for which multiple UpLink (UL) carriers are aggregated in a mobile communication system, the UE comprising:
 a radio transceiver for transmitting and receiving a message for executing multiple random access procedures for the multiple UL carriers;   a message generator/analyzer for generating and analyzing the message transmitted and received by the radio transceiver; and   a random access procedure executor for executing the multiple random access procedures for the multiple UL carriers,   wherein the random access procedure executor determines that a handover procedure of the UE has been successfully completed and transmits a handover confirm message to the target cell if all of the multiple random access procedures have been completed, and determines that the handover procedure of the UE has failed and performs a connection reestablishment procedure to one of neighboring cells if at least one of the multiple random access procedure fails.   
     
     
         25 . The UE of  claim 24 , wherein the message generator/analyzer generates and transmits the handover failure message to the target cell through an UL carrier for which a random access procedure among the multiple random access procedures has been completed, if it is determined that the handover procedure of the UE has failed. 
     
     
         26 . The UE of  claim 24 , wherein the handover command message comprises at least one of frequency information of the multiple UL carriers, sync identifications (IDs) of the multiple UL carriers, an indicator indicating the reference UL carrier, and reserved Packet Random Access Channel (PRACH) resource and Random Access Channel (RACH) preamble for the random access procedures of the UE. 
     
     
         27 . The method of  claim 3 , wherein the reference UL carrier is:
 set to a reference UL carrier in the source cell prior to handover;   set to an UL carrier linked with a reference DownLink (DL) carrier in the source cell prior to handover;   indicated by the handover command message;   set to an UL carrier linked with a DL carrier explicitly indicated by the handover command message; or   set to an UL carrier for which an UL TA has been first acquired according to the random access procedure.   
     
     
         28 . The method of  claim 3 , wherein the handover command message comprises at least one of frequency information of the multiple UL carriers, sync identifications (IDs) of the multiple UL carriers, an indicator indicating the reference UL carrier, and reserved Packet Random Access Channel (PRACH) resource and Random Access Channel (RACH) preamble for the random access procedures of the UE. 
     
     
         29 . The apparatus of  claim 9 , wherein the reference UL carrier is:
 set to a reference UL carrier in the source cell prior to handover;   set to an UL carrier linked with a reference DownLink (DL) carrier in the source cell prior to handover;   indicated by the handover command message;   set to an UL carrier linked with a DL carrier explicitly indicated by the handover command message; or   set to an UL carrier for which an UL TA has been first acquired according to the random access procedure.   
     
     
         30 . The apparatus of  claim 9 , wherein the handover command message comprises at least one of frequency information of the multiple UL carriers, sync identifications (IDs) of the multiple UL carriers, an indicator indicating the reference UL carrier, and reserved Packet Random Access Channel (PRACH) resource and Random Access Channel (RACH) preamble for the random access procedures of the UE. 
     
     
         31 . The method of  claim 19 , wherein the handover command message comprises at least one of frequency information of the multiple UL carriers, sync identifications (IDs) of the multiple UL carriers, an indicator indicating the reference UL carrier, and reserved Packet Random Access Channel (PRACH) resource and Random Access Channel (RACH) preamble for the random access procedures of the UE. 
     
     
         32 . The apparatus of  claim 22 , wherein the handover command message comprises at least one of frequency information of the multiple UL carriers, sync identifications (IDs) of the multiple UL carriers, an indicator indicating the reference UL carrier, and reserved Packet Random Access Channel (PRACH) resource and Random Access Channel (RACH) preamble for the random access procedures of the UE.