Radio communication device and radio communication method

A transmission method performed by a base station apparatus comprising:

• transmitting, via a plurality of antenna ports, a-first reference signals on a plurality of first resource elements and second reference signals different from the first reference signals on a plurality of a-second resource elements, a number of which in a resource block is less than a number of the plurality of first resource elements in the resource block, the first reference signals being associated with mobile stations supporting base station configurations of up to four antenna sorts and the second reference signals being associated with mobile stations supporting base station configurations of up to eight antenna ports, wherein the transmitting includes transmitting on one of the second resource elements of the plurality of second resource elements and via a pair of the plurality of antenna ports:
• a first one of the second reference signals, which is multiplied by “1”, via a first one of the pair of antenna ports among the plurality of antenna ports;
• and
• a second one of the second reference signals, which is multiplied by “−1”, via a second one of the pair of antenna ports among the plurality of antenna ports.

A base station apparatus, comprising:

• a plurality of antenna ports;
• and
• a transmitter configured to transmit, via the plurality of antenna ports, first reference signals on a plurality of first resource elements, and second reference signals different from the first reference signals on a plurality of second resource elements, wherein a number of the plurality of second resource elements in a resource block is less than a number of the plurality of first resource elements in the resource block, the first reference signals being associated with mobile stations of a first type and the second reference signals being associated with mobile stations of a second type, wherein the transmitter is configured to transmit on a second resource element and via a pair of antenna ports of the plurality of antenna ports:
• a first one of the second reference signals multiplied by “1”, via a first one of the pair of antenna ports;
• and
• a second one of the second reference signals multiplied by “−1”, via a second one of the pair of antenna ports.