There is provided an apparatus. The apparatus comprises: means for obtaining information of one or more non-active periods of a cell that is in discontinuous transmission; means for receiving at least one resource allocation for the apparatus; means for determining one or more resources of the at least one resource allocation that overlap fully or in part with the one or more non-active periods of the cell; and means for configuring a hybrid automatic repeat request acknowledgement codebook based at least in part on the determining one or more resources of the at least one resource allocation that overlap fully or in part with the one or more non-active periods of the cell.