Method and apparatus for allocating resources of a control channel in a mobile communication system using orthogonal frequency division multiplexing

1. A method for transmitting a downlink control channel in mobile communication system using Orthogonal Frequency Division Multiplexing (OFDM), the method comprising the steps of:

mapping the downlink control channel to Resource Elements (REs), wherein the downlink control channel comprises a plurality of RE groups;

transmitting downlink control information via the mapped downlink control channel;

wherein each of the plurality of RE groups comprises four REs, and each RE group has a single time index; and

wherein the plurality of RE groups are allocated to available resources in the downlink control channel in a time first manner, wherein the available resources are divided into a two-dimensional frequency/time structure, and wherein, during allocation, a time index is increased from an initial value up to a predetermined value in a given frequency index, before increasing to a next frequency index and resetting the time index to the initial value.

2. The method of claim 1 , wherein at least one of the plurality of RE groups comprises an RE for transmission of a reference signal used for channel estimation.

3. The method of claim 2 , wherein the at least one of the plurality of RE groups that comprises the RE for transmission of the reference signal has a number of allocated REs that is greater than four.

4. The method of claim 1 , wherein the downlink control channel is a Packet Dedicated Control Channel (PDCCH) and the plurality of RE groups are not assigned a Physical Channel Format Indication Channel (PCFICH) or a Physical Hybrid Automatic Repeat reQuest (H-ARO) Indicator Channel (PHICH).

5. The method of claim 1 , further comprising transmitting information associated with the available resources.

6. The method of claim 1 , wherein the predetermined value is a number of OFDM symbols used for transmission of the downlink control channel.

7. The method of claim 1 , wherein a time index of a first RE in a given RE group is the single time index for the given RE group.

8. An apparatus for transmitting a downlink control channel in a mobile communication system using Orthogonal Frequency Division Multiplexing (OFDM), the apparatus comprising:

a controller for allocating a plurality of Resource Element (RE) groups to available resources in the downlink control channel in a time first manner, wherein the available resources are divided into a two-dimensional frequency/time structure, and wherein, during allocation, a time index is increased from an initial value up to a predetermined value in a given frequency index, before increasing to a next frequency index and resetting the time index to the initial value;

a mapper for mapping the downlink control channel to REs; and

a transmitter for transmitting downlink control information via the mapped downlink control channel;

wherein each of the plurality of RE groups comprises four REs, and each RE group has a single time index.

9. The apparatus of claim 8 , wherein at least one of the plurality of RE groups comprises an RE for transmission of a reference signal used for channel estimation.

10. The apparatus of claim 9 , wherein the at least one of the plurality of RE groups that comprises the RE for transmission of the reference signal has a number of allocated REs that is greater than four.

11. The apparatus of claim 8 , wherein the downlink control channel is a Packet Dedicated Control Channel (PDCCH) and the plurality of RE groups are not assigned a Physical Channel Format Indication Channel (PCFICH) or a Physical Hybrid Automatic Repeat reQuest (H-ARO) Indicator Channel (PHICH).

12. The apparatus of claim 8 , wherein the transmitter transmits information associated with the available resources.

13. The apparatus of claim 8 , wherein the predetermined value is a number of OFDM symbols used for transmission of the downlink control channel.

14. The apparatus of claim 8 , wherein a time index of a first RE in a given RE group is the single time index for the given RE group.

15. A method for receiving a downlink control channel in a mobile communication system using Orthogonal Frequency Division Multiplexing (OFDM), the method comprising the steps of:

receiving the downlink control channel comprising a plurality of Resource Element (RE) groups; and

demapping downlink control information from the received downlink control channel;

wherein each of the plurality of RE groups comprises four REs, and each RE group has a single time index; and

wherein the plurality of RE groups are allocated to available resources in the downlink control channel in a time first manner, wherein the available resources are divided into a two-dimensional frequency/time structure, and wherein, during allocation, a time index is increased from an initial value up to a predetermined value in a given frequency index, before increasing to a next frequency index and resetting the time index to the initial value.

16. The method of claim 15 , further comprising receiving information associated with the available resources.

17. The method of claim 15 , wherein the predetermined value is a number of OFDM symbols used for transmission of the downlink control channel.

18. The method of claim 15 , wherein the downlink control channel is a Packet Dedicated Control Channel (PDCCH) and the plurality of RE groups are not assigned a Physical Channel Format Indication Channel (PCFICH) or a Physical Hybrid Automatic Repeat reQuest (H-ARQ) Indicator Channel (PHICH).

19. The method of claim 15 , wherein a time index of a first RE in a given RE group is the single time index for the given RE group.

20. The method of claim 15 , wherein at least one of the plurality of RE groups comprises an RE for transmission of a reference signal used for channel estimation.

21. The method of claim 20 , wherein the at least one of the plurality of RE groups that comprises the RE for transmission of the reference signal has a number of allocated REs that is greater than four.

22. An apparatus for receiving a downlink control channel in a mobile communication system using Orthogonal Frequency Division Multiplexing (OFDM), the apparatus comprising:

a receiver for receiving the downlink control channel;

a demapper for demapping downlink control information from the received downlink control channel; and

a controller for identifying that the control channel comprises a plurality of Resource Element (RE) groups that are allocated to available resources in the downlink control channel in a time first manner, wherein the available resources are divided into a two-dimensional frequency/time structure, and wherein, during allocation, a time index is increased from an initial value up to a predetermined value in a given frequency index, before increasing to a next frequency index and resetting the time index to the initial value;

wherein each of the plurality of RE groups comprises four REs, and each RE group has a single time index.

23. The apparatus of claim 22 , wherein the receiver receives information associated with the available resources.

24. The apparatus of claim 22 , wherein the predetermined value is a number of OFDM symbols used for transmission of the downlink control channel.

25. The apparatus of claim 22 , wherein the downlink control channel is a Packet Dedicated Control Channel (PDCCH) and the plurality of RE groups are not assigned a Physical Channel Format Indication Channel (PCFICH) or a Physical Hybrid Automatic Repeat reQuest (H-ARQ) Indicator Channel (PHICH).

26. The apparatus of claim 22 , wherein a time index of a first RE in a given RE group is the single time index for the given RE group.

27. The apparatus of claim 22 , wherein at least one of the plurality of RE groups comprises an RE for transmission of a reference signal used for channel estimation.

28. The apparatus of claim 27 , wherein the at least one of the plurality of RE groups that comprises the RE for transmission of the reference signal has a number of allocated REs that is greater than four.