A method comprising: using first information and second information to determine a code book size, said first information comprising information for at least one first subframe of at least one cell for which feedback information is to be provided, said at least one first subframe is no later than subframe n and second information for at least one second subframe of at least one cell for which feedback information is to be provided, said at least one second subframe being after said subframe n, wherein said first and second information comprises information from a plurality of different cells, and wherein said plurality of different cells use different uplink downlink time division duplex configurations, wherein the codebook on physical uplink shared channel is generated according to the maximum number of actually scheduled type 1 downlink subframes plus a maximum number of type 2 downlink subframes, wherein the type 1 downlink subframes comprise downlink subframes on all serving cells no later than the downlink subframe n and a corresponding positive / negative acknowledgement transmitted on a physical uplink shared channel scheduled in downlink subframe n, and wherein the type 2 downlink subframes comprise downlink subframes on all serving cells later than the downlink subframe n and the corresponding positive / negative acknowledgement transmitted on the physical uplink shared channel scheduled in downlink subframe n; using said code book size for providing feedback information; and causing said feedback information to be transmitted on a physical uplink shared channel scheduled in downlink subframe n, or causing feedback information to be transmitted in a subframe which is k subframes later than subframe n. using first information and second information to determine a code book size, said first information comprising information for at least one first subframe of at least one cell for which feedback information is to be provided, said at least one first subframe is no later than subframe n and second information for at least one second subframe of at least one cell for which feedback information is to be provided, said at least one second subframe being after said subframe n, wherein said first and second information comprises information from a plurality of different cells, and wherein said plurality of different cells use different uplink downlink time division duplex configurations, wherein the codebook on physical uplink shared channel is generated according to the maximum number of actually scheduled type 1 downlink subframes plus a maximum number of type 2 downlink subframes, wherein the type 1 downlink subframes comprise downlink subframes on all serving cells no later than the downlink subframe n and a corresponding positive / negative acknowledgement transmitted on a physical uplink shared channel scheduled in downlink subframe n, and wherein the type 2 downlink subframes comprise downlink subframes on all serving cells later than the downlink subframe n and the corresponding positive / negative acknowledgement transmitted on the physical uplink shared channel scheduled in downlink subframe n; using said code book size for providing feedback information; and causing said feedback information to be transmitted on a physical uplink shared channel scheduled in downlink subframe n, or causing feedback information to be transmitted in a subframe which is k subframes later than subframe n.