Apparatus and method for performing uplink synchronization in wireless communication system
View Patent ↗This specification relates to an apparatus and method for performing random access in a wireless communication system. This specification discloses a mobile station, including a reception unit for receiving TAG configuration information on which at least one serving cell configured in the mobile station is classified as a Timing Alignment Group (TAG) from a base station and a transmission unit for transmitting a random access preamble to the base station on one representative serving cell within the TAG. In accordance with this specification, a procedure of obtaining a TAV for a serving cell in order to secure and maintain uplink timing synchronization becomes clear, the time taken to obtain uplink synchronization for a serving cell may be reduced, and overhead due to excessive random access attempts may be reduced by obtaining a TAV for a plurality of serving cells through one random access procedure.
1. A method of performing an uplink synchronization by a base station (BS) in a wireless communication system, the method comprising:
transmitting configuration information to a user equipment (UE), the configuration information including timing advanced group (TAG) information indicating serving cells in which a timing advanced value (TAV) is applied;
transmitting random access preamble (RAP) allocation information to the UE, the RAP allocation information including a RAP index that indicates one preamble sequence selected from at least one dedicated RAP for a non-contention based random access procedure;
receiving a message including the preamble sequence; and
transmitting a random access response (RAR) to the UE, the RAR including a medium access control (MAC) protocol data unit (PDU),
wherein the MAC PDU comprises a header and a MAC control element (CE),
wherein the header includes a logical channel identifier (LCID) that indicates whether the MAC CE includes a timing advanced command (TAC) field, and
wherein the MAC CE includes a TAC field indicating a TAV and a TAG index field identifying a TAG to control uplink timing adjustment identically with the TAV, the TAC field being a 6-bit value, and the TAG index field being a 2-bit value.
2. The method of claim 1 , wherein the message is received through a first serving cell, and the first serving cell is an activated serving cell among the serving cells in the TAG.
3. The method of claim 1 , further comprising transmitting a Physical Downlink Control Channel (PDCCH) order to initiate a random access procedure for a secondary serving cell.
4. The method of claim 1 , wherein the at least one dedicated RAP is dedicated to the UE for the non-contention based random access procedure.
5. A method of performing an uplink synchronization by a User Equipment (UE) in a wireless communication system, the method comprising:
receiving configuration information, the configuration information including timing advanced group (TAG) information indicating serving cells in which a timing advanced value (TAV) is applied;
receiving random access preamble (RAP) allocation information, the RAP allocation information including a RAP index that indicates one preamble sequence selected from at least one dedicated RAP for a non-contention based random access procedure;
transmitting a message including the preamble sequence to a base station (BS); and
receiving a random access response (RAR), the RAR including a medium access control (MAC) protocol data unit (PDU),
wherein the MAC PDU comprises a header and a MAC control element (CE),
wherein the header includes a logical channel identifier (LCID) that indicates whether the MAC CE includes a timing advanced command (TAC) field, and
wherein the MAC CE includes a TAC field indicating a TAV and a TAG index field identifying a TAG to control uplink timing adjustment identically with the TAV, the TAC field being a 6-bit value, and the TAG index field being a 2-bit value.
6. The method of claim 5 , wherein the message is transmitted through a first serving cell, and the first serving cell is an activated serving cell among the serving cells in the TAG.
7. The method of claim 5 , further comprising receiving a Physical Downlink Control Channel (PDCCH) order to initiate a random access procedure for a secondary serving cell.
8. The method of claim 5 , wherein the at least one dedicated RAP is dedicated to the UE for the non-contention based random access procedure.