Reception and configuration of downlink control channel

1. A method of receiving a downlink control channel located in a data region, in user equipment (UE), the method comprising:

receiving an enhanced physical downlink control channel (EPDCCH) from a transmission/reception point, wherein the EPDCCH includes a data region of an N number of physical resource-block (PRB) pairs forming each of a K number of EPDCCH sets in a subframe, and wherein (i) the K and N are natural numbers which are greater than or equal to “1”, (ii) each of the N number of PRB pairs includes 16 enhanced resource element groups (EREGs), and (iii) an enhanced control channel element (ECCE) corresponding to a basic unit of an EPDCCH transmission includes 4 or 8 EREGs; and

decoding the EPDCCH in a corresponding EPDCCH set according to a downlink control information (DCI) format in an EPDCCH UE-specific search space, wherein ECCEs associated with the decoding of the EPDCCH are defined by a function of a radio network temporary identifier (RNTI) of the user equipment, an index of the subframe, an aggregation level, and a total number of ECCEs of the corresponding EPDCCH set.

2. The method of claim 1 , wherein the decoding the EPDCCH includes:

monitoring non-contiguous ECCEs in a unit of the number of ECCEs corresponding to the aggregation level.

3. The method of claim 2 , wherein the decoding the EPDCCH includes:

determining an ECCE hopping value of the non-contiguous ECCEs, using a function of a total number of ECCEs of the corresponding EPDCCH set, the aggregation level, and the number of EPDCCH candidates monitored by the user equipment based on the aggregation level.

4. The method of claim 1 , wherein in the case that the user equipment is configured with a carrier indicator field, a value of the carrier indicator field is applied to a function defining the ECCEs.

5. The method of claim 1 , wherein each EPDCCH set is formed for one of a localized EPDCCH transmission and a distributed EPDCCH transmission.

6. The method of claim 5 , wherein the aggregation level is selected as one of 1, 2, 4, 8, 16, and 32.

7. The method of claim 6 , wherein:

(i) for normal subframes and normal cyclic prefix (CP) when the number of REs for possible EPDCCH transmission is less than a threshold value (X thresh ),and for special subframes with special subframe configuration 3 , 4 , or 8 and normal CP when the number of REs for possible EPDCCH transmission is less than a threshold value (X thresh ), the aggregation level of the localized EPDCCH transmission is selected as one of 2, 4, 8, and 16, and the aggregation level of the distributed EPDCCH transmission is selected as one of 2, 4, 8, 16 and 32, and

(ii) otherwise, the aggregation level of the localized EPDCCH transmission is selected as one of 1, 2, 4, and 8, and the aggregation level of the distributed EPDCCH transmission is selected as one of 1, 2, 4, 8, and 16.

8. A method of configuring a downlink control channel located in a data region, in a user equipment (UE)-specific search space, in a transmission/reception point, the method comprising:

forming an enhanced physical downlink control channel (EPDCCH), wherein the forming the EPDCCH includes defining enhanced control channel elements (ECCEs) corresponding to a basic unit of an EPDCCH transmission in an EPDCCH UE-specific search space, and wherein (i) the EPDCCH includes a data region of an N number of physical resource-block (PRB) pairs forming each of a K number of EPDCCH sets in a subframe, (ii) the K and N are natural numbers which are greater than or equal to “1”, (iii) each of the N number of PRB pairs includes 16 enhanced resource element groups (EREGs), (iv) each of the ECCEs includes 4 or 8 EREGs, and (v) the ECCEs are defined by a function of a radio network temporary identifier (RNTI) of user equipment, an index of the subframe, an aggregation level, and a total number of ECCEs of a corresponding EPDCCH set; and

transmitting the ECCEs defined in the EPDCCH UE-specific search space, through the EPDCCH to the user equipment.

9. The method of claim 8 , wherein the defining the ECCEs includes:

defining the ECCEs such that the ECCEs are to be non-contiguous in a unit of the number of ECCEs corresponding to the aggregation level.

10. The method of claim 9 , wherein an ECCE hopping value of the ECCEs defined to be non-contiguous is determined by a function of a total number of ECCEs of the corresponding EPDCCH set, the aggregation level, and the number of EPDCCH candidates monitored by the user equipment based on the aggregation level.

11. The method of claim 8 , wherein:

in the case that the user equipment is configured with a carrier indicator field, a value of the carrier indicator field is applied to a function defining the ECCEs.

12. The method of claim 8 , wherein each EPDCCH set is formed for one of a localized EPDCCH transmission and a distributed EPDCCH transmission.

13. The method of claim 12 , wherein the aggregation level is selected as one of 1, 2, 4, 8, 16, and 32.

14. The method of claim 13 , wherein:

(i) for normal subframes and normal cyclic prefix (CP) when the number of REs for possible EPDCCH transmission is less than a threshold value (X thresh ), and for special subframes with special subframe configuration 3 , 4 , or 8 and normal CP when the number of REs for possible EPDCCH transmission is less than a threshold value (X thresh ), the aggregation level of the localized EPDCCH transmission is selected as one of 2, 4, 8, and 16, and the aggregation level of the distributed EPDCCH transmission is selected as one of 2, 4, 8, 16 and 32, and

(ii) otherwise, the aggregation level of the localized EPDCCH transmission is selected as one of 1, 2, 4, and 8, and the aggregation level of the distributed EPDCCH transmission is selected as one of 1, 2, 4, 8, and 16.

15. User equipment (UE) for receiving a downlink control channel located in a data region, the user equipment comprising:

a receiver configured to receive an enhanced physical downlink control channel (EPDCCH) from a transmission/reception point, wherein the EPDCCH includes a data region of an N number of physical resource-block (PRB) pairs forming each of a K number of EPDCCH sets in a subframe, and wherein (i) the K and N are natural numbers which are greater than or equal to “1”, (ii) each of the N number of PRB pairs includes 16 enhanced resource element groups (EREGs), and (iii) an enhanced control channel element (ECCE) corresponding to a basic unit of an EPDCCH transmission includes 4 or 8 EREGs; and

a control processor configured to decode the EPDCCH in a corresponding EPDCCH set according to a downlink control information (DCI) format in an EPDCCH UE-specific search space, wherein ECCEs associated with the decoding of the EPDCCH is defined by a function of a radio network temporary identifier (RNTI) of the user equipment, an index of the subframe, an aggregation level, and a total number of ECCEs of the corresponding EPDCCH set.

16. A transmission/reception point for configuring a downlink control channel located in a data region, in an EPDCCH user equipment (UE)-specific search space, the transmission/reception point comprising:

a control processor to configured to form an enhanced physical downlink control channel (EPDCCH), wherein the forming the EPDCCH includes defining enhanced control channel elements (ECCEs) corresponding to a basic unit of an EPDCCH transmission, in the EPDCCH UE-specific search space, and wherein (i) the EPDCCH includes a data region of an N number of physical resource-block (PRB) pairs forming each of a K number of EPDCCH sets in a subframe, (ii) the K and N are natural numbers which are greater than or equal to “1”, (iii) each of the N number of PRB pairs includes 16 enhanced resource element groups (EREGs), (iv) each of the ECCEs includes 4 or 8 EREGs, and (v) the ECCEs are defined by a function of a radio network temporary identifier (RNTI) of user equipment, an index of the subframe, an aggregation level, and a total number of ECCEs of a corresponding EPDCCH set; and

a transmitter configured to transmit the ECCEs defined in the EPDCCH UE-specific search space, through the EPDCCH to the user equipment.