Base station device, terminal device, and closed loop control method
View Patent ↗Provided is a base station device capable of reducing a DL-CSI feedback amount in a TDD type radio communication system in which a DL bandwidth is different from a UL bandwidth. In this device, a demultiplexing unit ( 133 ) separates an UL pilot, a DL-CQI, and a DL-CSI fed back from a plurality of UEs as communication partners; a channel estimation unit ( 134 ) performs channel sounding by using a UL pilot from a UE in which a DL channel and a UL channel are allocated by overlapping a part of the bandwidth so as to obtain UL-CSI; a control DL-CSI acquisition unit ( 135 ) performs interpolation of DL-CSI by using the DL-CSI of some RB contained in the bandwidth where the DL channel and the UL channel fed back from the UE are not overlapped; and a DL close loop control unit ( 104 ) combines the estimated UL-CSI and the interpolated DL-CSI so as to use them as DL-CSI for controlling the DL close loop.
1. A base station apparatus that communicates with a plurality of terminal apparatuses using a time division duplex scheme in which a downlink bandwidth and an uplink bandwidth are different, the base station apparatus comprising:
an allocation section that allocates a downlink band and an uplink band to a specific terminal apparatus in the plurality of terminal apparatuses, such that a frequency of the allocated uplink band is the same as a frequency of a first part of the allocated downlink band;
a reception section that receives downlink channel state information (DL-CSI) of a second part of the downlink band other than the first part of the downlink band from the specific terminal apparatus, the received DL-CSI being used as a second DL-CSI for closed loop control processing;
a request section that transmits, to the specific terminal apparatus, request information for requesting feedback of the DL-CSI of the second part of the allocated downlink band;
a channel estimation section that performs channel estimation using a pilot signal transmitted on the allocated uplink band from the specific terminal apparatus, to estimate uplink channel state information (UL-CSI), the estimated UL-CSI being used as a first DL-CSI for the closed loop control processing; and
a control section that performs the closed loop control processing in the allocation section using the first DL-CSI and the second DL-CSI,
wherein:
the reception section receives a downlink channel quality indicator (DL-CQI) from the specific terminal apparatus, the DL-CQI being equal to or more than a first threshold value of channel quality.
2. The base station apparatus according to claim 1 , further comprising:
a determination section that calculates cross correlation between the DL-CSI in a first frequency band and the UL-CSI in the first frequency band in the estimated UL-CSI, to determine channel reciprocity, the first frequency band being included in the frequency of the first part of the allocated downlink band, and the DL-CSI in the first frequency band being fed back from the specific terminal,
wherein, when the cross correlation is equal to or more than a threshold value, the control section performs the closed loop control processing using the first DL-CSI and the second DL-CSI, and, when the cross correlation is less than the threshold value, the control section performs the closed loop control processing using the second DL-CSI only.
3. A base station apparatus that communicates with a plurality of terminal apparatuses using a time division duplex scheme in which a downlink bandwidth and an uplink bandwidth are different, the base station apparatus comprising:
a measurement section that derives delay spread using a delay profile of a channel, to measure channel fluctuation;
an allocation section that allocates a downlink band and an uplink band to a specific terminal apparatus in the plurality of terminal apparatuses, such that a frequency of the allocated uplink band is the same as a frequency of a first part of the allocated downlink band;
a reception section that receives downlink channel state information (DL-CSI) of a second part of the downlink band other than the first part of the downlink band from the specific terminal apparatus, the received DL-CSI being used as a second DL-CSI for closed loop control processing;
a request section that transmits, to the specific terminal apparatus, request information for requesting feedback of the DL-CSI in the second part of the allocated downlink band, the second part of the downlink band being a band in which the channel fluctuation is smaller than a second threshold value,
a channel estimation section that performs channel estimation using a pilot signal transmitted on the allocated uplink band from the specific terminal apparatus, to estimate uplink channel state information (UL-CSI), the estimated UL-CSI being used as a first DL-CSI for the closed loop control processing; and
a control section that performs the closed loop control processing in the allocation section using the first DL-CSI and the second DL-CSI,
wherein:
the allocation section allocates the uplink band and the downlink band to one of the bands in which the channel fluctuation is equal to or more than the second threshold value, such that the frequency of the allocated uplink band is the same as the frequency of the first part of the downlink band.
4. A terminal apparatus that communicates with a base station apparatus using a time division duplex scheme in which a downlink bandwidth and an uplink bandwidth are different, the terminal apparatus comprising:
a channel estimation section that performs channel estimation using a pilot signal transmitted from the base station to obtain downlink channel state information (DL-CSI); and
a transmission section that feeds back a downlink channel quality indicator (DL-CQI) to the base station apparatus and feeds back the DL-CSI of a partial band to the base station apparatus, when a downlink band and an uplink band are allocated to the terminal apparatus by the base station such that a frequency of the allocated uplink band is the same as a frequency of a first part of the allocated downlink band, and when request information on feeding back the DL-CSI is received from the base station apparatus, the partial band being a second part of the allocated downlink band other than the first part of the allocated downlink band, the request information requesting feedback of the DL-CSI of the second part of the allocated downlink band, and the DL-CQI being equal to or more than a first threshold value of channel quality.
5. A closed loop control method performed by a base station apparatus that communicates with a plurality of terminal apparatuses used in a time division duplex scheme in which a downlink bandwidth and an uplink bandwidth are different, the method comprising:
allocating a downlink band and an uplink band to a specific terminal apparatus in the plurality of terminal apparatuses, such that a frequency band of the allocated uplink band is the same as a frequency of a first part of the allocated downlink band;
receiving a downlink channel quality indicator (DL-CQI) from the specific terminal apparatus, the DL-CQI being equal to or more than a first threshold value of channel quality;
transmitting, to the specific terminal apparatus, request information for requesting feedback of downlink channel state information (DL-CSI) of a second part of the allocated downlink band other than the first part of the downlink band;
receiving DL-CSI of the second part of the downlink band, from the specific terminal apparatuses, the received DL-CSI being used as a second DL-CSI for closed loop control processing;
performing channel estimation using a pilot signal transmitted on the allocated uplink band from the specific terminal apparatus, to estimate uplink channel state information (UL-CSI), the estimated UL-CSI being used as a first DL-CSI for the closed loop control processing; and
performing the closed loop control processing for a downlink band allocation using the first DL-CSI and the second DL-CSI.