Base station device, terminal device, transmission method, and reception method
A base station device causing no decrease in system throughput and guaranteeing the reception quality at a terminal when a DCI directed toward the terminal is mapped to a PDCCH region and an R-PDCCH region. A search space setting unit ( 103 ) sets a search space having a plurality of allocation candidates, in both regions. An allocation unit ( 106 ) allocates control information to a resource in one allocation candidate in the search space. The ratio of the number of allocation candidates in the R-PDCCH region to the number of allocation candidates in the PDCCH region in the search space for a terminal using DM-RS in the R-PDCCH region is equal to or greater than the ratio of the number of allocation candidates in the R-PDCCH region to the number of allocation candidates in the PDCCH region in the search space for a terminal using CRS in the R-PDCCH region.
1. A base station apparatus that transmits control information using a first control channel and a second control channel, the first control channel using a common reference signal that is receivable by all terminal apparatuses, the second control channel using the common reference signal or a specific reference signal for each terminal apparatus, the base station apparatus comprising:
a search space configuring section of a first integrated circuit configured to configure a search space having a plurality of allocation candidates, in a first resource region to which the first control channel is mapped and a second resource region to which the second control channel is mapped; and
an allocating section of the first integrated circuit or a second integrated circuit configured to allocate the control information to a resource in one allocation candidate from among the plurality of allocation candidates in the search space, wherein:
a ratio of a number of the allocation candidates in the second resource region to a number of the allocation candidates in the first resource region in the search space configured in the terminal apparatus using the specific reference signal in the second control channel is equal to or greater than a ratio of a number of the allocation candidates in the second resource region to a number of the allocation candidates in the first resource region in the search space configured in the terminal apparatus using the common reference signal in the second control channel.
2. The base station apparatus according to claim 1 , further comprising a generating section of the first integrated circuit, the second integrated circuit, or a third integrated circuit configured to generate the control information in a first format or a second format, the first format being a format common to all the terminals, the second format being a format corresponding to a transmission mode configured for a terminal, wherein:
the allocating section is configured to allocate the control information in the first format to the search space configured in the first resource region and allocates the control information in the second format to the search space configured in the second resource region.
3. A terminal apparatus comprising:
a first receiving section of a first integrated circuit configured to blind-decode a search space having a plurality of allocation candidates configured in a first resource region to which a first control channel is mapped and a second resource region to which a second control channel is mapped, the first control channel using a common reference signal that is receivable by all terminal apparatuses, the second control channel using the common reference signal or a specific reference signal for each terminal apparatus, and obtains control information transmitted using the first control channel or the second control channel; and
a second receiving section of the first integrated circuit or a second integrated circuit configured to receive a downlink data signal based on the control information for the terminal apparatus allocated to one of the plurality of allocation candidates, wherein:
a ratio of a number of the allocation candidates in the second resource region to a number of the allocation candidates in the first resource region in the search space configured in the terminal apparatus using the specific reference signal in the second control channel is equal to or greater than a ratio of a number of the allocation candidates in the second resource region to a number of the allocation candidates in the first resource region in the search space configured in the terminal apparatus using the common reference signal in the second control channel.
4. A transmission method performed by a base station apparatus that transmits control information using a first control channel and a second control channel, the first control channel using a common reference signal that receivable by all terminal apparatuses, the second control channel using the common reference signal or a specific reference signal for each terminal apparatus, the transmission method comprising:
configuring a search space having a plurality of allocation candidates, in a first resource region to which the first control channel is mapped and a second resource region to which the second control channel is mapped; and
allocating the control information to a resource in one allocation candidate from among the plurality of allocation candidates in the search space, wherein:
a ratio of a number of the allocation candidates in the second resource region to a number of the allocation candidates in the first resource region in the search space configured in the terminal apparatus using the specific reference signal in the second control channel is equal to or greater than a ratio of a number of the allocation candidates in the second resource region to a number of the allocation candidates in the first resource region in the search space configured in the terminal apparatus using the common reference signal in the second control channel.
5. A reception method comprising:
blind-decoding a search space having a plurality of allocation candidates configured in a first resource region to which a first control channel is mapped and a second resource region to which a second control channel is mapped, the first control channel using a common reference signal that is receivable by all terminal apparatuses, the second control channel using the common reference signal or a specific reference signal for each terminal apparatus, and obtaining control information transmitted using the first control channel or the second control channel; and
receiving a downlink data signal based on the control information for the terminal apparatus allocated to one of the plurality of allocation candidates, wherein:
a ratio of a number of the allocation candidates in the second resource region to a number of the allocation candidates in the first resource region in the search space configured in the terminal apparatus using the specific reference signal in the second control channel is equal to or greater than a ratio of a number of the allocation candidates in the second resource region to a number of the allocation candidates in the first resource region in the search space configured in the terminal apparatus using the common reference signal in the second control channel.