Method and apparatus for a User Equipment (UE) determining a resource for a transmission of a control signal in response to a detected control channel including Control Channel Elements (CCEs), where transmission of the control signal is with a first sequence or with a second sequence, if a first resource or a second resource is used, respectively. The first resource is determined from the CCE index while the second resource is determined from a group of consecutive CCE indexes. The UE is also signaled a bit-map associating the subframe of the control channel detection with the use of a first resource or of a second resource.