A first control signal can be transmitted in a short PDCCH belonging to a first subset of a set of configured short PDCCH candidates associated with a first set of aggregation levels in a first TTI of a subframe. A second control signal can be transmitted in a short PDCCH belonging to a second subset of the set of short PDCCH candidates associated with a second set of aggregation levels in a second TTI of the subframe. The first subset of the set of short PDCCH candidates and the second subset of the short PDCCH candidates can be different. The first subset of the set of short PDCCH candidates can be based on a first index associated with the first TTI. The second subset of the set of short PDCCH candidates can be based on a second index associated with the second TTI. The subframe can comprise at least the first and the second TTIs.