A method for processing signals at a user equipment in a TDD (Time Division Duplex) wireless communication system, wherein a first subframe configuration is configured for a primary cell and a second subframe configuration is configured for a secondary cell, the method comprising:
- receiving, from a network, downlink data in a first subframe via the secondary cell;
- and
- transmitting, to the network in a second subframe, ACK (acknowledgement)/NACK (negative-ACK) information for the downlink data via the primary cell,
- wherein the first subframe configuration is a different configuration than the second subframe configuration,
- wherein a first subframe according to both the first subframe configuration and the second subframe configuration is a downlink subframe, and
- wherein the first subframe has an index n-k and the second subframe has an index n, and k is an integer determined based on the first subframe configuration.