Communication apparatus and communication method
Overhead related to precoding (beamforming weight) information to be notified over a backhaul may be reduced while maintaining an ICI reduction effect by coordinated CoMP among a plurality of nodes. A communication apparatus of the invention includes a reception unit that receives precoding information from user equipment, a selection unit that variably controls an amount of the precoding information, which is to be notified to another communication apparatus via a backhaul, in response to positions of frequency resources, and a transmission unit that transmits the precoding information to the other communication apparatus in accordance with the amount of the precoding information controlled by the selection unit.
1. A communication apparatus, comprising:
a reception unit that receives precoding information from user equipment;
a selection unit that variably controls an amount of the precoding information, which is to be notified to another communication apparatus via a backhaul, in response to positions of frequency resources; and
a transmission unit that transmits the precoding information to the other communication apparatus in accordance with the amount of the precoding information controlled by the selection unit,
wherein the selection unit correlates information of future transmission signal power, information of future transmission signal power density, information of normalized transmission signal energy, information of normalized transmission signal energy density, and information representing a communication quality for each of the frequency resources in a serving cell, with the amount of the precoding information at a position of the corresponding frequency resource.
2. The communication apparatus according to claim 1 , wherein
the larger the information of the future transmission signal power, the information of the future transmission signal power density, the information of the normalized transmission signal energy or the information of the normalized transmission signal energy density for each of the frequency resources in the serving cell, or the better the information representing the communication quality for each of the frequency resources in the serving cell, the further the selection unit increases the amount of the precoding information at the position of the corresponding frequency resource, and
the smaller the information of the future transmission signal power, the information of the future transmission signal power density, the information of the normalized transmission signal energy or the information of the normalized transmission signal energy density for each of the frequency resources in the serving cell, or the worse the information representing the communication quality for each of the frequency resources in the serving cell, the further the selection unit decreases the amount of the precoding information at a position of the corresponding frequency resource.
3. The communication apparatus according to claim 2 , wherein
the selection unit correlates a binary indicator, which represents the information of the future transmission signal power, of RNTP for each physical resource block, with the amount of the precoding information at the corresponding physical resource block.
4. The communication apparatus according to claim 3 , wherein
in regard to a physical resource block in which a value of the binary indicator of the RNTP is 1, the transmission unit transmits the precoding information to the other communication apparatus via the backhaul, and
in regard to a physical resource block in which a value of the binary indicator of the RNTP is 0, the transmission unit does not transmit the precoding information to the other communication apparatus via the backhaul.
5. The communication apparatus according to claim 3 , wherein
the selection unit controls the amount of the precoding information in band units of a sub-band in response to the number of 1's of the binary indicator of the RNTP or the number of 0's of the binary indicator of the RNTP in the sub-band including at least a plurality of resource elements, a plurality of sub-carriers, and a plurality of physical resource blocks.
6. The communication apparatus according to claim 5 , wherein
the larger the number of 1's of the binary indicator of the RNTP in the band of the sub-band, the further the selection unit increases the amount of the precoding information, and
the larger the number of 0's of the binary indicator of the RNTP in the band of the sub-band, the further the selection unit decreases the amount of the precoding information.
7. The communication apparatus according to claim 3 , wherein
the selection unit controls the amount of the precoding information in band units of a sub-band in response to the number of 1's of the indicator of three values or more of the RNTP or the number of 0's of the indicator of three values or more of the RNTP in the sub-band including at least a plurality of resource elements, a plurality of sub-carriers, and a plurality of physical resource blocks.
8. The communication apparatus according to claim 7 , wherein
where the indicator of the RNTP for each of the frequency resource is expressed by three values or more, the larger the indicator of three values or more of the RNTP, the further the selection unit increases the amount of the precoding information of a band corresponding to the frequency resource block, and
the smaller the indicator of three values or more of the RNTP, the further the selection unit decreases the amount of the precoding information of a band corresponding to the frequency resource block.
9. The communication apparatus according to claim 2 , wherein
the selection unit correlates a plurality of threshold values for each cell which are used when determining a binary indicator, which represents information of the future transmission signal power, of RNTP for each frequency resource block, with the amount of the precoding information.
10. The communication apparatus according to claim 9 , wherein
the larger the threshold value of the RNTP, the further the selection unit increases the amount of the precoding information, and
the smaller the threshold value of the RNTP, the further the selection unit decreases the amount of the precoding information.
11. The communication apparatus according to claim 3 , wherein
the transmission unit notifies the other communication apparatus of the threshold value of the RNTP that is used for each cell together with the precoding information.
12. The communication apparatus according to claim 2 , wherein
the transmission unit makes a first notification cycle differ from a second notification cycle, the first notification cycle being defined to notify a plurality of other communication apparatuses of the information of the future transmission signal power, the information of the future transmission signal power density, the information of the normalized transmission signal energy, the information of the normalized transmission signal energy density, or the information representing the communication quality, which is correlated with the amount of the precoding information at the frequency resource positions, for each frequency resource in the serving cell, and the second notification cycle being defined to notify a plurality of other communication apparatuses of the precoding information.
13. The communication apparatus according to claim 12 , wherein
the transmission unit makes the second notification cycle longer than the first notification cycle, and
the transmission unit adjusts the second notification cycle to be shorter than the first notification cycle when the communication apparatus uses a transmission power control method in which transmission is performed with a constant power.
14. The communication apparatus according to claim 1 , wherein
the transmission unit transmits the precoding information together with physical resource position information representing position information of the frequency resources.
15. The communication apparatus according to claim 1 , wherein
the selection unit changes precoding information to be notified to the other communication apparatus to precoding information whose use in neighbor cells is suppressed, or precoding information whose use in the neighbor cells is encouraged.
16. A communication method in a communication apparatus, comprising:
receiving precoding information from user equipment;
variably controlling an amount of the precoding information, which is to be notified to another communication apparatus via a backhaul, in response to a position of a frequency resource;
correlating information of future transmission signal power, information of future transmission signal power density, information of normalized transmission signal energy, information of normalized transmission signal energy density, and information representing a communication quality for each of the frequency resources in a serving cell, with the amount of the precoding information at a position of the corresponding frequency resource; and
transmitting the precoding information to the other communication apparatus in accordance with the controlled amount of the precoding information.