Allocation of communication resources

1. An apparatus comprising:

at least one processor; and

at least one memory including computer program code, the at least one memory and the computer program code configured, with the at least one processor, to:

receive, from a network element, a downlink assignment allocated by the network element on a downlink control channel;

determine from the downlink assignment an index for an uplink control resource using a mapping rule known to the network element to derive said index from an index associated with a physical downlink resource and the amount of downlink resources to be mapped on the uplink control resource; and

transmit, to the network element, a control message associated with the downlink assignment on the determined uplink control resource known to the network element.

2. The apparatus according to claim 1 , wherein the at least one memory and the computer program code are further configured, with the at least one processor, to:

take into account the lowest index of the physical downlink resource block.

3. The apparatus according to claim 1 , wherein the index associated with the physical downlink resource comprises the index of at least one of an enhanced control channel element, an enhanced physical downlink control channel and a physical downlink shared channel scheduled by means of an enhanced physical downlink control channel.

4. The apparatus according to claim 1 , wherein the at least one memory and the computer program code are further configured, with the at least one processor, to:

use an offset in determining the index for the uplink control resource.

5. The apparatus according to claim 4 , wherein the at least one memory and the computer program code are further configured, with the at least one processor, to:

use at least one of an antenna port indicator and a scrambling identity in defining the offset.

6. The apparatus according to claim 4 , wherein the at least one memory and the computer program code are further configured, with the at least one processor, to:

use the offset for dynamic switching between at least two physical uplink control channel (PUCCH) format 1/1a/1b resources.

7. The apparatus according to claim 1 , wherein the amount of downlink resources is indicative of a number of downlink physical resource blocks that map to a physical uplink control channel resource.

8. The apparatus according to claim 1 , wherein the at least one memory and the computer program code are further configured, with the at least one processor, to:

process indications of the amount of downlink resources based on a configurable parameter.

9. The apparatus according to claim 1 , wherein the downlink resource comprises a physical downlink shared channel, and wherein the at least one memory and the computer program code are further configured, with the at least one processor, to:

communicate scheduling information for the physical downlink shared channel by means of an enhanced physical downlink control channel and for determining an index for a physical uplink control channel associated with the physical downlink shared channel.

10. The apparatus according to claim 1 , wherein the at least one memory and the computer program code are further configured, with the at least one processor, to:

determine at least one index for signalling of automatic repeat request messages.

11. The apparatus according to claim 1 , wherein the at least one memory and the computer program code are further configured, with the at least one processor, to:

define a final index for the uplink control resource by applying at least one further operation to the index determined based on the index associated with a physical downlink resource and the amount of downlink resources to be mapped on the uplink control resource.

12. A method comprising:

receiving, from a network element, a downlink assignment allocated by the network element on a downlink control channel;

determining from the downlink assignment an index for an uplink control resource using a mapping rule known to the network element to derive said index from an index associated with a physical downlink resource and the amount of downlink resources to be mapped on the uplink control resource; and

transmitting, to the network element, a control message associated with the downlink assignment on the determined uplink control resource known to the network element.

13. The method according to claim 12 , further comprising:

taking into account the lowest index of the physical downlink resource block.

14. The method according to claim 12 , wherein the index associated with the physical downlink resource comprises the index of at least one of an enhanced control channel element, an enhanced physical downlink control channel and a physical downlink shared channel scheduled by means of an enhanced physical downlink control channel.

15. The method according to claim 12 , further comprising:

applying an offset in determining the index of the uplink control resource.

16. The method according to claim 15 , further comprising:

dynamically switching between at least two PUCCH format 1/1a/1b resources by means of the offset.

17. The method according to claim 12 , wherein the amount of downlink resources is indicative of the number of downlink physical resource blocks that map to a physical uplink control channel resource.

18. The method according to claim 12 , further comprising:

configuring the amount of downlink resources by means of a parameter.

19. The method according to claim 12 , wherein the downlink resource comprises a physical downlink shared channel, comprising signalling scheduling information for the physical downlink shared channel by means of an enhanced physical downlink control channel for determining an index for a physical uplink control channel that associates with the physical downlink shared channel.

20. The method according to claim 12 , configured to determine at least one index for signalling of automatic repeat request messages.

21. A computer program product comprising a non-transitory computer-readable storage medium bearing computer program code embodied therein for use with a computer, the computer program code comprising code for performing the method according to claim 12 .

22. An apparatus comprising:

at least one processor; and

at least one memory including computer program code, the at least one memory and the computer program code configured, with the at least one processor, to:

allocate downlink resources for communication to a user equipment;

determine an index for an uplink control resource using a mapping rule known to the user equipment to derive said index from an index associated with a physical downlink resource and the amount of downlink resources to be mapped on the uplink control resource;

send a downlink assignment on a downlink control channel to the user equipment; and

receive a control message associated with the downlink assignment on the determined uplink control resource from the user equipment.

23. The apparatus according to claim 22 , wherein the at least one memory and the computer program code are further configured, with the at least one processor, to:

use an offset in determining the index for the uplink control resource and configured for signalling of an offset parameter in the downlink.

24. The apparatus according to claim 22 , wherein the at least one memory and the computer program code are further configured, with the at least one processor, to:

signal information about the amount of downlink resources in a user equipment specific or cell specific manner.

25. A method comprising:

allocating downlink resources for communication to a user equipment;

determining an index for an uplink control resource using a mapping rule known to the user equipment to derive said index from an index associated with a physical downlink resource and the amount of downlink resources to be mapped on the uplink control resource;

sending a downlink assignment on a downlink control channel to the user equipment; and

receiving a control message associated with the downlink assignment on the determined uplink control resource from the user equipment.

26. A computer program product comprising a non-transitory computer-readable storage medium bearing computer program code embodied therein for use with a computer, the computer program code comprising code for performing the method according to claim 25 .