A method in a base station for reference signalling, comprising: determining transmission parameters for reference signalling for use by a user equipment on at least one component carrier of a plurality of aggregated component carriers; sending a message containing information indicative of the transmission parameters for configuration of the user equipment for reference signalling; sending in the same message a trigger to the user equipment for reference signalling; and in response to sending of the message containing the information and the trigger, receiving at least one reference signal from the user equipment characterized in that the message further contains information indicative of at least one component carrier to be used by the user equipment for the reference signalling and is an UL aperiodic Channel State Information-on-PUSCH-only grant, said sending of the message is only for assigning parameters for signalling of aperiodic channel state information, indicating the at least one component carrier, and triggering the reference signalling on the indicated at least one component carrier, the information indicative the at least one component carrier is included in a predefined field of the message for enabling the user equipment to determine the at least one component carrier for reference signalling based on analysis of information in the predefined field, and the base station receives only reference signalling from the user equipment on the indicated at least one component carrier in time instances for transmission of reference signalling on the indicated at least one component carrier according to said information in the message. determining transmission parameters for reference signalling for use by a user equipment on at least one component carrier of a plurality of aggregated component carriers; sending a message containing information indicative of the transmission parameters for configuration of the user equipment for reference signalling; sending in the same message a trigger to the user equipment for reference signalling; and in response to sending of the message containing the information and the trigger, receiving at least one reference signal from the user equipment characterized in that the message further contains information indicative of at least one component carrier to be used by the user equipment for the reference signalling and is an UL aperiodic Channel State Information-on-PUSCH-only grant, said sending of the message is only for assigning parameters for signalling of aperiodic channel state information, indicating the at least one component carrier, and triggering the reference signalling on the indicated at least one component carrier, the information indicative the at least one component carrier is included in a predefined field of the message for enabling the user equipment to determine the at least one component carrier for reference signalling based on analysis of information in the predefined field, and the base station receives only reference signalling from the user equipment on the indicated at least one component carrier in time instances for transmission of reference signalling on the indicated at least one component carrier according to said information in the message.