A base station for aperiodic reporting channel state information, CSI, from a user equipment for use in a communication system in which a plurality of downlink component carriers and at least one uplink component carrier are configured for communication between the base station and the user equipment, comprising: a transmitter, which, in operation, transmits to the user equipment a trigger message that triggers the aperiodic reporting of CSI for at least one unlicensed downlink component carrier of the plurality of downlink component carriers, the trigger message being transmitted in a subframe n Trigger; and a receiver, which, in operation, receives from the user equipment, the triggered CSI for the at least one unlicensed downlink component carrier of the plurality of downlink component carriers based on reference signals present on the at least one unlicensed downlink component carrier of the plurality of downlink component carriers, in a subframe n Report later than n Trigger, wherein the reference signals, on the basis of which the CSI is to be reported, are present in a subframe n RS on the at least one unlicensed downlink component carrier of the plurality of downlink component carriers, where n RS is indicated by the base station, and wherein the unlicensed downlink component carrier is occupied for a period of time for a bursty downlink transmission between the base station and the user equipment, and a subframe to be evaluated for the reporting of CSI by the user equipment is limited to the indicated subframe n RS without evaluating a subframe in other bursty downlink transmission, characterized in that the triggered CSI for the aperiodic reporting for the unlicensed downlink component carrier is a wideband CSI based on reference signals present in a set of sub-bands, S, which spans, or is a subset of, the downlink system bandwidth of the at least one downlink component carrier, and includes: - a wideband channel quality indicator, CQI, value per codeword, which is calculated assuming use of a single precoding matrix in all sub-bands and downlink transmission on the set of sub-bands, S; and - a selected single precoding matrix indicator, PMI, or a first and second PMI corresponding to the selected single PMI, wherein the single PMI is selected from a codebook subset assuming downlink transmission on the set of sub-bands, S, and wherein the reported PMI and the reported CQI values are calculated conditioned on a reported rank indicator, Rl, or are calculated conditioned on RI = 1. a transmitter, which, in operation, transmits to the user equipment a trigger message that triggers the aperiodic reporting of CSI for at least one unlicensed downlink component carrier of the plurality of downlink component carriers, the trigger message being transmitted in a subframe n Trigger; and a receiver, which, in operation, receives from the user equipment, the triggered CSI for the at least one unlicensed downlink component carrier of the plurality of downlink component carriers based on reference signals present on the at least one unlicensed downlink component carrier of the plurality of downlink component carriers, in a subframe n Report later than n Trigger, wherein the reference signals, on the basis of which the CSI is to be reported, are present in a subframe n RS on the at least one unlicensed downlink component carrier of the plurality of downlink component carriers, where n RS is indicated by the base station, and wherein the unlicensed downlink component carrier is occupied for a period of time for a bursty downlink transmission between the base station and the user equipment, and a subframe to be evaluated for the reporting of CSI by the user equipment is limited to the indicated subframe n RS without evaluating a subframe in other bursty downlink transmission, characterized in that the triggered CSI for the aperiodic reporting for the unlicensed downlink component carrier is a wideband CSI based on reference signals present in a set of sub-bands, S, which spans, or is a subset of, the downlink system bandwidth of the at least one downlink component carrier, and includes: - a wideband channel quality indicator, CQI, value per codeword, which is calculated assuming use of a single precoding matrix in all sub-bands and downlink transmission on the set of sub-bands, S; and - a selected single precoding matrix indicator, PMI, or a first and second PMI corresponding to the selected single PMI, - a wideband channel quality indicator, CQI, value per codeword, which is calculated assuming use of a single precoding matrix in all sub-bands and downlink transmission on the set of sub-bands, S; and - a selected single precoding matrix indicator, PMI, or a first and second PMI corresponding to the selected single PMI, wherein the single PMI is selected from a codebook subset assuming downlink transmission on the set of sub-bands, S, and wherein the reported PMI and the reported CQI values are calculated conditioned on a reported rank indicator, Rl, or are calculated conditioned on RI = 1.