Patent ID: 8842585

Claim:
A wireless communication system comprising: a mobile station apparatus; and a base station apparatus configured to transmit, to the mobile station apparatus, a physical downlink control channel in either a first physical downlink control channel candidate in a common search space or a second physical downlink control channel candidate in a user equipment-specific search space, the mobile station apparatus configured to monitor the first physical downlink control channel candidate in the common search space and the second physical downlink control channel candidate in the user equipment-specific search space, for the first physical downlink control channel candidate in. the common search space and the second physical downlink control channel candidate in the user equipment-specific search space satisfying that (i) a first control information in the first physical downlink control channel candidate and a second control information in the second physical downlink control channel candidate being with cyclic redundancy check scrambled by C-RNTI (Cell Radio Network Temporary Identifier), (ii) the first control information and the second control information being with same payload size, (iii) the first physical downlink control channel candidate and the second physical downlink control channel candidate being comprised of control channel elements with same indices, and (iv) the first control information and the second control information being with different downlink control information fields in case that the mobile station apparatus is configured with a carrier indicator field associated with monitoring the physical downlink control channel, the base station apparatus being configured to transmit only the physical downlink control channel in the first physical downlink control channel candidate in the common search space, and the mobile station apparatus being configured to perform monitoring of physical downlink control channel assuming that only the physical downlink control channel in the first physical downlink control channel candidate in the common search space is transmitted.