Transmission of reference signals

1. A method comprising:

determining resources for reference signalling on at least one component carrier of a plurality of aggregated component carriers;

sending information indicative of the at least one component carrier and associated resources for configuration of a station for reference signalling;

sending a trigger for reference signalling; and

in response to the trigger, receiving at least one reference signal from the station on the indicated at least one component carrier, wherein the indicated at least one component carrier is determined by analyzing predefined bits of the information according to a pre-established protocol,

wherein indication of the at least one component carrier and the trigger are communicated in the same message,

and further comprising:

determining that the message is only for assigning resources for signalling of aperiodic channel state information;

checking the state of the trigger for reference signaling;

determining, based on the message, that only reference signalling is to be transmitted; and

determining at least one component carrier for reference signalling based on analysis of a predefined field of the message.

2. A method comprising:

receiving at a station information indicative of at least one component carrier of aggregated component carriers and associated resources for use in reference signalling; and

in response to a trigger, sending from the station at least one reference signal using the indicated at least one component carrier and resources, wherein the indicated at least one component carrier is determined by analyzing predefined bits of the information according to a pre-established protocol,

wherein indication of the at least one component carrier and the trigger are communicated in the same message,

and further comprising:

determining that the message is only for assigning resources for signalling of aperiodic channel state information;

checking the state of the trigger for reference signalling;

determining, based on the message, that only reference signalling is to be transmitted; and

determining at least one component carrier for reference signalling based on analysis of a predefined field of the message.

3. The method as claimed in claim 2 , wherein the reference signal comprises an aperiodic sounding reference signal.

4. The method as claimed in claim 2 , wherein the information of resources associated with a component carrier comprises an indication of at least one time instance on which reference signalling can be sent on the given component carrier.

5. The method as claimed in claim 2 , wherein the associated resources comprise transmission parameters for the at least one component carrier, the transmission parameters defining at least one of a set of cell specific and/or user equipment specific reference signal subframes, reference signal starting position, reference signal bandwidth, reference signal comb, reference signal hopping configuration, and reference signal sequence.

6. The method as claimed in claim 2 , comprising providing the station with a time pattern indicative of possible subframes for sending of reference signalling.

7. The method as claimed in claim 2 , comprising receiving or sending a reference signal in the first available subframe following a subframe carrying the trigger.

8. The method as claimed in claim 2 , comprising analysing the information and the trigger by a user equipment to determine component carrier, timing and other resources for the triggered reference signalling.

9. The method as claimed in claim 2 , wherein said information and the trigger are communicated in separate messages.

10. The method as claimed in claim 2 , wherein indication of the at least one component carrier to be used is carried by a resource assignment message.

11. The method as claimed in claim 10 , wherein the resource assignment message comprises an uplink grant or a downlink grant signalled on a physical control channel.

12. The method as claimed in claim 2 , comprising determining at least one component carrier for use in reference signalling based on analysis of predefined bits of the message.

13. The method as claimed in claim 2 , comprising signalling the information on a signalling layer that is higher than the layer used for signalling of the at least one reference signal.

14. The method as claimed in claim 2 , comprising using a single component carrier for reference signalling at a time.

15. The method as claimed in claim 2 , comprising using at least two component carriers for reference signalling at a time.

16. The method as claimed in claim 2 , comprising prioritizing component carriers.

17. The method as claimed in claim 2 , comprising determining the at least one component carrier based on a linked component carrier.

18. The method as claimed in claim 17 , wherein linkage between a resource allocation grant and an uplink component carrier carrying aperiodic sounding reference signal is made based on system information.

19. 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 being configured, with the at least one processor, to:

determine resources for reference signalling on at least one component carrier of a plurality of aggregated component carriers;

send information to a second station indicative of the at least one component carrier of a plurality of aggregated component carriers and associated resources to be used for reference signalling by the second station;

send a trigger for reference signalling; and

in response to the trigger, receive at least one reference signal from the station on the indicated at least one component carrier, wherein the indicated at least one component carrier is determined by analyzing predefined bits of the information according to a pre-established protocol,

wherein indication of the at least one component carrier and the trigger are communicated in the same message,

and further comprising:

determining that the message is only for assigning resources for signalling of aperiodic channel state information;

checking the state of the trigger for reference signaling;

determining, based on the message, that only reference signalling is to be transmitted; and

determining at least one component carrier for reference signalling based on analysis of a predefined field of the message.

20. A base station apparatus comprising the apparatus in accordance with claim 19 .

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 2 .

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 being configured, with the at least one processor, to:

determine, from signalling received from a first station, information indicative of at least one component carrier of aggregated component carriers and associated resources for use in reference signalling by a second station; and

in response to a trigger, send from the second station at least one reference signal using the indicated at least one component carrier and resources, wherein the indicated at least one component carrier is determined by analyzing predefined bits of the information according to a pre-established protocol,

wherein indication of the at least one component carrier and the trigger are communicated in the same message,

and further comprising:

determining that the message is only for assigning resources for signalling of aperiodic channel state information;

checking the state of the trigger for reference signaling;

determining, based on the message, that only reference signalling is to be transmitted; and

determining at least one component carrier for reference signalling based on analysis of a predefined field of the message.

23. The apparatus as claimed in claim 22 , wherein the reference signal comprises an aperiodic sounding reference signal.

24. The apparatus as claimed in claim 22 , wherein the information of resources associated with a component carrier comprise an indication of at least one time instance on which reference signalling can be sent on the given component carrier.

25. The apparatus as claimed in claim 22 , configured to provide the second station with resource information comprising at least one of a set of cell specific and/or user equipment specific reference signal subframes, reference signal starting position, reference signal bandwidth, reference signal comb, reference signal hopping configuration, and reference signal sequence.

26. The apparatus as claimed in claim 22 , configured to provide the second station with a time pattern indicative of possible subframes for sending of reference signalling.

27. The apparatus as claimed in claim 22 , configured to cause sending of a reference signal in the first available subframe in response to the trigger.

28. The apparatus as claimed in claim 22 , configured to communicate indication of the at least one component carrier and the trigger in a single message.

29. The apparatus as claimed in claim 28 , configured to determine at least one component carrier for use in reference signalling based on analysis of predefined parts of the message.

30. The apparatus as claimed in claim 28 , configured to determine that the message is only for assigning resources for signalling of aperiodic channel state information, to check the state of the trigger for reference signalling, and to determine that only reference signalling is to be transmitted.

31. The apparatus as claimed in claim 22 , configured to communicate indication of the at least one component carrier for reference signalling by means of a resource assignment message.

32. A communication device comprising the apparatus in accordance with claim 22 .

33. The communication device as claimed in claim 32 , comprising a mobile user equipment.

34. A communication system comprising the apparatus, a communication device and/or base station in accordance with claim 22 .