<Channel Quality Indicator (CQI)>
Described below is the channel quality indicator CQI in EUTRA (Evolved Universal Terrestrial Radio Access; hereinafter, referred to as “EUTRA”). The channel quality indicator CQI is a measurement result of channel quality measured by a mobile station apparatus using a downlink reference signal of a downlink pilot channel received from a base station apparatus, and is information indicative of channel quality of a downlink system band for each mobile station apparatus. For example, information, which is indicative of modulation scheme-coding rate considered suitable for the downlink shared channel based on the measured quality information, is configured as the channel quality indicator CQI. More specifically, on the condition that the error rate of information data arranged on the downlink shared channel does not exceed 0.1, information indicative of a combination of modulation scheme and coding rate with the highest communication efficiency is configured as the channel quality indicator CQI.
The mobile station apparatus periodically transmits the channel quality indictor CQI to the base station apparatus, using an uplink control channel beforehand assigned from the base station apparatus. In addition, in starting communication connection with a mobile station apparatus, the base station apparatus allocates periodical radio resources (hereinafter, CQI arrangement-capable control channels) for the mobile station apparatus to arrange the channel quality indicator CQI. In addition, herein, the radio resources indicate radio resources comprised of a predetermined frequency band and time band. In addition, code multiplexing is also applied to the uplink control channel for arranging the channel quality indicator CQI in EUTRA, but is omitted herein, for convenience in description.
Using the channel quality indicator CQI received from the mobile station apparatus, the base station apparatus performs radio resource allocation (frequency scheduling) of a downlink shared channel to the mobile station apparatus, and selection of the modulation scheme and coding rate (adaptive modulation and coding) of the downlink shared channel. For example, the base station apparatus assigns the downlink shared channel to a downlink resource block of good channel quality indicator CQI for the mobile station apparatus. Further, the base station apparatus sets the modulation scheme of the downlink shared channel from among QPSK (Quadrature Phase Shift Keying), 16 QAM (16 Quadrature Amplitude Modulation), and 64 QAM (64 Quadrature Amplitude Modulation), corresponding to the channel quality indicator CQI.
<Component Frequency Band>
Meanwhile, 3GPP (3rd Generation Partnership Project) has started studies of the 4th Generation (hereinafter, referred to as “4G”) radio access scheme (Advanced EUTRA; hereinafter, referred to as “A-EUTRA”) and 4G network (Advanced EUTRAN) of cellular mobile communications.
In A-EUTRA, it is studied supporting wider frequency bands than EUTRA, and ensuring compatibility with EUTRA. Therefore, in A-EUTRA, studied are techniques (referred to as Spectrum aggregation or Carrier aggregation) that the base station apparatus performs communications using a system band comprised of a plurality of component frequency bands with a frequency band of EUTRA regarded as a single unit (component frequency band) (in addition, the component frequency band is sometimes referred to as a carrier component or component carrier.) (Non-patent Document 1) In the techniques, the base station apparatus performs communications with a mobile station apparatus supporting EUTRA using any one of component frequency bands in each of uplink and downlink, while performing communications with a mobile station apparatus supporting A-EUTRA using one or more component frequency bands in each of uplink and downlink.