TECHNICAL FIELD

The present invention relates to a base station apparatus, a terminal apparatus, and a communication method.

This application claims priority to JP 2017-187871 filed on Sep. 28, 2017, the contents of which are incorporated herein by reference.

BACKGROUND ART

Research and development activities related to 5th generation mobile radio communication systems (5G system) have been actively carried out, aiming to start commercial services around the year 2020. A vision recommendation on the standard system of the 5G system (International mobile telecommunication-2020 and beyond: IMT-2020) was recently reported (see NPL 1) by the International Telecommunication Union Radio communications Sector (ITU-R), which is an international standardization body.

Providing sufficient frequency resources is an important challenge for a communication system to handle a surge in data traffic. Thus, a target of 5G is to achieve ultra-high capacity communication using a frequency band higher than the frequency band used in LTE (Long term evolution).

However, in radio communication using high frequency bands, path loss is a problem. For compensation for path loss, beamforming based on a multiplicity of antennas has been a promising technique (see NPL 2).

CITATION LIST

Non Patent Literature

NPL 1: “IMT Vision—Framework and overall objectives of the future development of IMT for 2020 and beyond,” Recommendation ITU-R M. 2083-0, September 2015.NPL 2: “E. G. Larsson, O. Edfors, F. Tufvesson, and T. L. Marzetta, “Massive MIMO for next generation wireless system,” IEEE Commun. Mag., vol. 52, no. 2, pp. 186-195, February 2014.

SUMMARY OF INVENTION

Technical Problem

However, in a communication system including multiple base station apparatuses, especially in a cellular system, beamforming based on multiple antennas results stochastically in strong received signals due to beamforming from the multiple base station apparatuses.

In view of these circumstances, an object of the present invention is to provide a base station apparatus, a terminal apparatus, and a communication method that can improve frequency efficiency or throughput in a case that multiple base station apparatuses perform transmission based on beamforming.

Solution to Problem

To achieve the above-mentioned object, a base station apparatus, a terminal apparatus, and a communication method according to an aspect of the present invention are configured as follows.

A base station apparatus according to an aspect of the present invention is a base station apparatus for communicating with a terminal apparatus, the base station apparatus including: a higher layer processing unit configured to configure multiple channel state information reference signal (CSI-RS) resources and assistance information; a transmitter configured to transmit CSI-RSs by using the multiple CSI-RS resources; and a receiver configured to receive, from the terminal apparatus, information (CRI) indicating one CSI-RS resource of the multiple CSI-RS resources, wherein the assistance information is information for assisting the terminal apparatus in cancelling or suppressing neighbor cell interference, the assistance information includes at least one of a cell ID, a subcarrier spacing, a demodulation reference signal (DMRS) configuration, the number of DMRS antenna ports, power offset between a reference signal and PDSCH, or the number of layers, and one or more of the assistance information is configured for the CRI.

In the base station apparatus according to an aspect of the present invention, the multiple CSI-RS resources are divided into multiple groups, and the CRI is received for each of the groups.

A terminal apparatus according to an aspect of the present invention is a terminal apparatus for communicating with a base station apparatus, the terminal apparatus including: a higher layer processing unit for which multiple channel state information reference signal (CSI-RS) resources and assistance information are configured; a receiver configured to receive CSI-RSs by using the multiple CSI-RS resources; a measuring unit configured to generate channel state information (CSI) from the CSI-RSs; and a transmitter configured to transmit the CSI to the base station apparatus, wherein the CSI includes information (CRI) indicating one CSI-RS resource of the multiple CSI-RS resources, the assistance information is information for assisting the terminal apparatus in canceling or suppressing neighbor cell interference, the assistance information includes at least one of a cell ID, a subcarrier spacing, a demodulation reference signal (DMRS) configuration, the number of DMRS antenna ports, power offset between a reference signal and PDSCH, or the number of layers, and one or more of the assistance information is configured for the CRI.

In the terminal apparatus according to an aspect of the present invention, the multiple CSI-RS resources are divided into multiple groups, and the CRI is determined for each of the groups.

The transmitter transmits a downlink shared channel and CRI associated with demodulation of the downlink shared channel, and cancels or suppresses an interference signal by using the assistance information associated with the CRI.

A communication method according to an aspect of the present invention is a communication method for a base station apparatus for communicating with a terminal apparatus, the communication method including the steps of: configuring multiple channel state information reference signal (CSI-RS) resources and assistance information; transmitting CSI-RSs by using the multiple CSI-RS resources; and receiving, from the terminal apparatus, information (CRI) indicating one CSI-RS resource of the multiple CSI-RS resources, wherein the assistance information is information for assisting the terminal apparatus in cancelling or suppressing neighbor cell interference, the assistance information includes at least one of a cell ID, a subcarrier spacing, a demodulation reference signal (DMRS) configuration, the number of DMRS antenna ports, power offset between a reference signal and PDSCH, or the number of layers, and one or more of the assistance information is configured for the CRI.

A communication method according to an aspect of the present invention is a communication method for a terminal apparatus for communicating with a base station apparatus, the communication method including the steps of: configuring, for the terminal apparatus, multiple channel state information reference signal (CSI-RS) resources and assistance information; receiving CSI-RSs by using the multiple CSI-RS resources; generating channel state information (CSI) from the CSI-RSs; and transmitting the CSI to the base station apparatus, wherein the CSI includes information (CRI) indicating one CSI-RS resource of the multiple CSI-RS resources, the assistance information is information for assisting the terminal apparatus in cancelling or suppressing neighbor cell interference, the assistance information includes at least one of a cell ID, a subcarrier spacing, a demodulation reference signal (DMRS) configuration, the number of DMRS antenna ports, power offset between a reference signal and PDSCH, or the number of layers, and one or more of the assistance information is configured for the CRI.

Advantageous Effects of Invention

According to an aspect of the present invention, the base station apparatus or the terminal apparatus can efficiently control, cancel, or suppress interference to improve frequency efficiency or throughput.

