Apparatus and method for performing random access in a wireless communication system

1. A method of performing random access in a wireless communication system, the method comprising:

configuring a uplink (UL) timing group including at least one of CCs having a difference in center frequencies within a threshold range, CCs having the same beamforming scheme, CCs having the same timing advance (TA) value, and CCs having the same reference downlink (DL) CC for obtaining a TA value, from among a plurality of CCs;

setting a CC satisfying at least one of a CC having a lowest center frequency value, a CC having a center frequency value that is closest to a mean value, a CC having a highest center frequency value, a CC having a broadest frequency band, and a CC in which a radio link monitoring (RLM) is defined, in the configured UL timing group as a delegate CC;

obtaining a TA value to be used for obtaining a UL timing through the delegate CC; and

updating a TA value of the corresponding UL timing group based on the obtained TA value.

2. The method as claimed in claim 1 , further comprising:

determining whether a CC that is added or removed exists; and

reconfiguring the UL timing group based on the determined CC.

3. The method as claimed in claim 1 , wherein obtaining of the time alignment timer value comprises:

obtaining the time alignment timer value by receiving, from an evolved NodeB (eNB), a random access response message including the TA value to be used for the UL timing.

4. The method as claimed in claim 1 , further comprising:

sensing occurrence of a condition for updating the TA value,

wherein the condition for updating the TA value corresponds to at least one of:

a case in which re-establishment of synchronization with respect to DL CCs is required;

a case in which transmission of UL data is initialized;

a case in which a UE-specific time alignment timer expires; and

a case in which a time alignment timer set for each UL timing group expires.

5. The method as claimed in claim 1 , wherein obtaining of the time alignment timer value further comprises:

transmitting a random access preamble (RAP) through CCs that are ungrouped from a UL timing group by a user equipment (UE); or

transmitting an RAP through a predetermined CC that fails to secure the validity in a predetermined UL timing group.

6. The method as claimed in claim 2 , wherein reconfiguring of the UL timing group is performed when a response is not obtained through UL CCs in response to UL transmission data, when DL synchronization reconfiguration with respect to a few CCs is required, when a CC time alignment timer set for each CC expires, or when a DL/UL linkage is changed.

7. The method as claimed in claim 1 , wherein setting of the delegate CC comprises:

setting a CC corresponding to a primary cell (PCell) in the UL timing group to be the delegate CC.

8. An apparatus for performing random access in a wireless communication system, the apparatus comprising:

a uplink timing group configuring unit to configure a uplink (UL) timing group including at least one of component carriers (CCs) having a difference in center frequencies within a threshold range, CCs having the same beamforming scheme, CCs having the same timing advance (TA) value, and CCs having the same reference downlink (DL) CC to be used for obtaining a TA value, from among a plurality of CCs;

a delegate CC setting unit to set a CC satisfying at least one of a CC having a lowest center frequency value, a CC having a center frequency value that is closest to a mean value, a CC having a highest center frequency, a CC having a broadest frequency band, a CC in which a radio link monitoring (RLM) is defined, in the configured UL timing group as a delegate CC;

a TA value obtaining unit to obtain a TA value to be used for obtaining a UL timing through the delegate CC; and

a TA value updating unit to update a TA value of the corresponding UL timing group based on the obtained TA value.

9. The apparatus as claimed in claim 8 , further comprising:

a determining unit to determine whether a CC that is added or removed exists; and

a timing group reconfiguring unit to reconfigure the UL timing group based on the determined CC.

10. The apparatus as claimed in claim 8 , wherein the TA value obtaining unit receives a random access response message including the TA value to be used for obtaining the UL timing, from an evolved NodeB (eNB).

11. The apparatus as claimed in claim 8 , further comprising:

a condition sensing unit to sense occurrence of a condition for updating the TA value,

wherein the condition for updating the TA value corresponds to at least one of:

a case in which re-establishment of synchronization with respect to DL CCs is required;

a case in which transmission of UL data is initialized;

a case in which a UE-specific time alignment timer expires; and

a case in which a time alignment timer set for each UL timing group expires.

12. The apparatus as claimed in claim 8 , wherein the TA value obtaining unit transmits a random access preamble (RAP) through CCs that are ungrouped from a UL timing group by a user equipment (UE), or transmits an RAP through a predetermined CC that fails to secure the validity in a predetermined UL timing group.

13. The apparatus as claimed in claim 9 , wherein the timing group reconfiguring unit performs reconfiguration of the UL timing group when a response is not obtained through UL CCs in response to UL transmission data, when DL synchronization reconfiguration with respect to a few CCs is required, when a CC time alignment timer set for each CC expires, or when a DL/UL linkage is changed.

14. The apparatus as claimed in claim 8 , wherein the delegate CC setting unit sets a CC corresponding to a primary service cell (PCell) in the UL timing group to be the delegate CC.

15. A method of performing random access in a wireless communication system, the method comprising:

receiving UL timing group configuration information of a UL timing group that is configured with at least one of CCs having a difference in center frequencies within a threshold range, component carriers (CCs) having the same beamforming scheme, CCs having the same timing advance (TA) value, and CCs having the same reference downlink (DL) CC to be used for obtaining a TA value, from among a plurality of CCs;

receiving delegate CC information of a delegate CC which corresponding a CC satisfying at least one of a CC having a lowest center frequency value, a CC having a center frequency value that is closest to a mean value, a CC having a highest center frequency value, a CC having a broadest frequency band, and a CC in which a radio link monitoring (RLM) is defined, in the configured UL timing group; and

calculating a timing advance (TA) value based on the received UL timing group configuration information and the delegate CC information, and transmitting the calculated TA value.

16. An apparatus for performing random access in a wireless communication system, the apparatus comprising:

a receiving unit to receive UL timing group configuration information of a UL timing group that is configured with at least one of component carriers (CCs) having a difference in center frequencies within a threshold range, CCs having the same beamforming scheme, CCs having the same timing advance (TA) value, and CCs having the same reference downlink (DL) CC to be used for obtaining a TA value, from among a plurality of CCs, and to receive delegate CC information of a delegate CC which corresponding a CC satisfying at least one of a CC having a lowest center frequency value, a CC having a center frequency value that is closest to a mean value, a CC having a highest center frequency value, a CC having a broadest frequency band, and a CC in which a radio link monitoring (RLM) is defined, in the configured UL timing group;

a timing advance (TA) value generating unit to calculate a TA value based on the received UL timing group configuration information and the delegate CC information; and

a transceiving unit to transmit the calculated TA value.