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

Abstract

The present invention is designed to provide a radio base station, a user terminal, a radio communication method and a radio communication system of novel structures that can achieve improved throughput and system capacity. A radio base station transmits downlink reference signals that are specific to a plurality of transmission beams, a plurality of user terminals feed back channel state information acquired by channel estimation using the downlink reference signals, to the radio base station, the radio base station determines a plurality of user terminals to non-orthogonal-multiplex, per transmission beam, based on the channel state information that is fed back, and non-orthogonal-multiplexes downlink signals for the plurality of user terminals that are determined, in each of the plurality of transmission beams, and a plurality of user terminals that are determined, after having canceled interference between the transmission beams by means of a linear filter, demodulates downlink signals for the subject terminal, from the downlink signals that are non-orthogonal-multiplexed in each transmission beam.

1 . A radio base station comprising:
 a beam generating section that generates a plurality of transmission beams;   a downlink reference signal generating section that generates downlink reference signals that are specific to each transmission beam;   a downlink control information generating section that generates downlink control information to request a feedback of channel state information to a user terminal;   a scheduling section that determines a plurality of user terminals to non-orthogonal-multiplex, per transmission beam, based on the channel state information that is fed back; and   a downlink channel multiplexing section that non-orthogonal-multiplexes downlink signals for the plurality of user terminals that are determined, in each of the plurality of transmission beams, in accordance with results determined in the scheduling section.   
     
     
         2 . The radio base station according to  claim 1 , wherein the downlink channel multiplexing section multiplexes the downlink signals for the plurality of user terminals that are determined so that the downlink signals are transmitted with different transmission power in a same transmission beam. 
     
     
         3 . The radio base station according to  claim 1 , wherein the scheduling section determines the plurality of user terminals to non-orthogonal-multiplex, per transmission beam, so that minimum downlink throughput is maximized. 
     
     
         4 . The radio base station according to  claim 1 , wherein the channel state information is channel quality information. 
     
     
         5 . The radio base station according to  claim 1 , wherein the beam generating section generates the plurality of transmission beams based on a predetermined precoding matrix. 
     
     
         6 . A user terminal comprising:
 a channel estimation section that performs channel estimation by using downlink reference signals that are specific to a plurality of transmission beams;   a feedback section that feeds back channel state information acquired by the channel estimation, to a radio base station; and   an interference cancelation section that cancels interference between the transmission beams, from downlink signals for a plurality of user terminals that are non-orthogonal-multiplexed, per transmission beam, based on the channel state information that is fed back, by means of a linear filter, and then cancels downlink signals for other terminals that are non-orthogonal-multiplexed in a same transmission beam.   
     
     
         7 . A radio communication method, in which:
 a radio base station transmits downlink reference signals that are specific to a plurality of transmission beams;   a plurality of user terminals feed back channel state information acquired by channel estimation using the downlink reference signals, per transmission beam, to the radio base station;   the radio base station determines a plurality of user terminals to non-orthogonal-multiplex, per transmission beam, based on the channel state information that is fed back, and non-orthogonal-multiplexes downlink signals for the plurality of user terminals that are determined, in each of the plurality of transmission beams; and the plurality of user terminals that are determined, after having canceled interference between the transmission beams by means of a linear filter, cancels downlink signals for other terminals, from the downlink signals that are non-orthogonal-multiplexed in each transmission beam.   
     
     
         8 . (canceled)