Extending physical downlink control channels

An apparatus for receipt of downlink control information (DCI) in a communication system, the apparatus comprising:

• a receiver configured to receive information representative of presence of carrier indicator on higher layer signaling from a Node B, and to receive information representative of at least one cell index on higher layer signaling from the Node B;
• and
• a controller configured to define a UE specific search space based on an aggregation level, a UE ID, and at least one carrier indicator value, where the UE specific search space comprises a set of physical downlink control channel (PDCCH) candidates based on the aggregation level, and to decode at least one PDCCH including at least one DCI respectively based on the UE ID;
• wherein the at least one carrier indicator value is based on the at least one cell index, and
• wherein the UE specific search space is identified by parameters of the UE specific search space for a single cell.

A method for transmission of downlink control information (DCI) in a communication system, the method comprising:

• transmitting information representative of presence of carrier indicator on higher layer signaling to a user equipment (UE);
• and
• transmitting information representative of at least one cell index on higher layer signaling to the UE,
• wherein a UE specific search space is defined based on an aggregation level, a UE ID, and at least one carrier indicator value, where the UE specific search space comprises a set of physical downlink control channel (PDCCH) candidates based on the aggregation level,
• wherein at least one PDCCH comprises at least one DCI respectively based on the UE ID,
• wherein the at least one carrier indicator value is based on the at least one cell index, and
• wherein the UE specific search space is identified by parameters of the UE specific search space for a single cell.

An apparatus for transmission of downlink control information (DCI) in a communication system, the apparatus comprising:

• a transmitter configured to transmit information representative of presence of carrier indicator on higher layer signaling to a user equipment (UE), and to transmit information representative of at least one cell index on higher layer signaling to the UE;
• and
• a controller configured to control the transmitter to transmit, to the UE, at least one DCI to the UE within a UE specific search space that is defined based on an aggregation level, a UE ID, and at least one carrier indicator value, where the UE specific search space comprises a set of Physical Downlink Control Channel (PDCCH) candidates based on the aggregation level,
• wherein at least one PDCCH comprises the at least one DCI respectively based on the UE ID,
• wherein the at least one carrier indicator value is based on the at least one cell index, and
• wherein the UE specific search space is identified by parameters of the UE specific search space for a single cell.