An apparatus, comprising: means for sending, by a network node and in a first subframe, data in a downlink shared channel and a timing indicator in a physical downlink control channel to a user equipment, the timing indicator indicating an offset relative to the first subframe the user equipment should use in order to determine a second subframe to use to send, in a physical uplink control channel, acknowledgement information for the data received in the downlink shared channel of the first subframe; and means for receiving by the network node the acknowledgement information from the user equipment in the physical uplink control channel of the second subframe, wherein a number of orthogonal frequency division multiplexing symbols carrying the physical uplink control channel varies dynamically from subframe to subframe, wherein the sending is performed for multiple first subframes and corresponding timing indicators are modified for the multiple first subframes so that the user equipment would calculate a same second subframe to use for acknowledgement information for the data received by the user equipment in the multiple first subframes, wherein the receiving further comprises receiving by the network node the acknowledgement information from the user equipment in the physical uplink control channel of the second subframe for the acknowledgement information for the data received by the user equipment in the multiple first subframes, wherein the receiving further comprises receiving by the network node the acknowledgement information from the user equipment in resources of the physical uplink control channel of the second subframe, and wherein locations of the resources in the physical uplink control channel of the second subframe are derived according to a subframe of the multiple first subframes with a smallest value of the timing indicator and a corresponding lowest physical downlink control channel resource unit. means for sending, by a network node and in a first subframe, data in a downlink shared channel and a timing indicator in a physical downlink control channel to a user equipment, the timing indicator indicating an offset relative to the first subframe the user equipment should use in order to determine a second subframe to use to send, in a physical uplink control channel, acknowledgement information for the data received in the downlink shared channel of the first subframe; and means for receiving by the network node the acknowledgement information from the user equipment in the physical uplink control channel of the second subframe, wherein a number of orthogonal frequency division multiplexing symbols carrying the physical uplink control channel varies dynamically from subframe to subframe, wherein the sending is performed for multiple first subframes and corresponding timing indicators are modified for the multiple first subframes so that the user equipment would calculate a same second subframe to use for acknowledgement information for the data received by the user equipment in the multiple first subframes, wherein the receiving further comprises receiving by the network node the acknowledgement information from the user equipment in the physical uplink control channel of the second subframe for the acknowledgement information for the data received by the user equipment in the multiple first subframes, wherein the receiving further comprises receiving by the network node the acknowledgement information from the user equipment in resources of the physical uplink control channel of the second subframe, and wherein locations of the resources in the physical uplink control channel of the second subframe are derived according to a subframe of the multiple first subframes with a smallest value of the timing indicator and a corresponding lowest physical downlink control channel resource unit.