Signaling method of CSI-RS location indexes indicative of CSI-RS location positions in a resource block and base station apparatus

A base station apparatus comprising:

• a locating section that uses a processor to locate a CSI-RS (Channel State Information-Reference Signal) in any resource elements of CSI-RS resources defined to transmit the CSI-RS, the CSI-RS being a reference signal for downlink for which CSI-RS location indexes are defined associated with each number of CSI-RS ports of 2, 4, and 8;
• an index generating section that uses the processor to output a CSI-RS location index corresponding to the resource elements of the CSI-RS resources where the CSI-RS is located by the locating section;
• and
• a transmission section that transmits the CSI-RS location indexes output from the index generating section to a mobile terminal apparatus,
• wherein the CSI-RS location indexes are defined associated with the number of CSI-RS ports so that an index pattern of the number of CSI-RS ports of “4” is a subset of an index pattern of the number of CSI-RS ports of “8”, and an index pattern of the number of CSI-RS ports of “2” is a subset of the index pattern of the number of CSI-RS ports of “4”, and the index pattern comprised of two CSI-RS location indexes “n” and “n+N” associated with the number of CSI-RS ports of “4” is derived from one basic index “n” associated with the number of CSI-RS ports of “8”, and the index pattern comprised of four CSI-RS location indexes including the two CSI-RS location indexes “n” and “n+N” associated with the number of CSI-RS ports of “2” is derived from the CSI-RS location indexes “n” and “n+N”.