A terminal includes a decoder to decode a downlink control channel transmitted on one or more control channel element(s) (CCE(s)) in a search space including a plurality of CCEs. Processing circuitry in the terminal determines an uplink channel resource index based on the one or more CCEs, the uplink channel resource index having an association with a first uplink channel transmission spreading sequence and a second different uplink channel transmission spreading sequence. A transmitter transmits a response signal on an uplink channel using the first and second uplink channel transmission spreading sequences.