Radio base station, user terminal, radio communication system and radio communication method

A radio communication method for a user terminal receiving downlink control information from a radio base station by an enhanced downlink control channel which is frequency-division-multiplexed with a downlink shared data channel, the radio communication method comprising:

• receiving allocation information of a plurality of frequency resource sets each including a plurality of physical resource block (PRB) pairs placed for the enhanced downlink control channel;
• and
• decoding search space candidates for a given frequency resource set based on the allocation information to acquire the downlink control information,
• wherein a number of search space candidates per frequency resource set is configured such that a total number of search space candidates for the plurality of frequency resource sets as a whole is equal to or less than a given value,
• wherein the plurality of frequency resource sets are two frequency resource sets, and
• wherein the downlink control information is mapped in a distributed manner to PRB pairs that constitute one of the two frequency resource sets, and the downlink control information is mapped in a localized manner to PRB pairs that constitute another frequency resource set.

A radio base station that transmits downlink control information to a user terminal by an enhanced downlink control channel which is frequency-division-multiplexed with a downlink shared data channel, the radio base station comprising:

• an allocation section configured to control allocation to the user terminal of a plurality of frequency resource sets each including a plurality of physical resource block (PRB) pairs placed for the enhanced downlink control channel;
• a transmitting section configured to transmit, to the user terminal, allocation information of the plurality of frequency resources sets;
• and
• a mapping section configured to map the downlink control information to a plurality of PRB pairs that constitute a given frequency resource set allocated to the user terminal,
• wherein a number of search space candidates per frequency resource set is configured such that a total number of search space candidates for the plurality of frequency resource sets as a whole is equal to or less than a given value,
• wherein the plurality of frequency resource sets are two frequency resource sets, and
• wherein the downlink control information is mapped in a distributed manner to PRB pairs that constitute one of the two frequency resource sets, and the downlink control information is mapped in a localized manner to PRB pairs that constitute another frequency resource set.

A radio communication system comprising:

• a radio base station that transmits downlink control information by an enhanced downlink control channel which is frequency-division-multiplexed with a downlink shared data channel;
• and
• a user terminal that receives the downlink control information from the radio base station, wherein
• the radio base station comprises a transmitting section configured to transmit, to the user terminal, allocation information of a plurality of frequency resources sets each including a plurality of physical resource block (PRB) pairs placed for the enhanced downlink control channel,
• the user terminal comprises a receiving section configured to receive the allocation information and an acquisition section configured to decode search space candidates for a given frequency resource set based on the allocation information to acquire the downlink control information, and
• a number of search space candidates per frequency resource set is configured such that a total number of search space candidates for the plurality of frequency resource sets as a whole is equal to or less than a given value,
• wherein the plurality of frequency resource sets are two frequency resource sets, and
• wherein the downlink control information is mapped in a distributed manner to PRB pairs that constitute one of the two frequency resource sets, and the downlink control information is mapped in a localized manner to PRB pairs that constitute another frequency resource set.