A base station transmits a message configuring first radio resources of a control channel. The first radio resources comprise one or more sets of resource blocks in a subset of subframes in a plurality of subframes. The base station transmits scheduling information on the control channel for a packet transmitted on an uplink data channel. The base station transmits a positive or negative acknowledgement on second radio resources of a feedback channel for receiving the packet. The second radio resources start from the first OFDM symbol of the second subframe.