Radio communication system, radio base station apparatus, and user equipment

Abstract

A radio communication system includes a radio base station having multiple antenna elements arranged two-dimensionally, and a user equipment configured to perform radio communication with the radio base station. The radio base station is configured to transmit a reference signal used for channel estimation in two or more different configurations using a part or all of the antenna elements, and wherein the user equipment is configured to feed back at least one of horizontal channel information, vertical channel information, and inter-polarization channel information to the radio base station.

What is claimed is: 
     
         1 . A radio communication system comprising:
 a radio base station having multiple antenna elements arranged two-dimensionally; and   a user equipment configured to perform radio communication with the radio base station,   wherein the radio base station is configured to transmit a reference signal used for channel estimation in two or more different configurations using a part or all of the antenna elements, and   wherein the user equipment is configured to feedback at least one of horizontal channel information, vertical channel information, and inter-polarization channel information to the radio base station.   
     
     
         2 . The radio communication system according to  claim 1 ,
 wherein the radio base station transmits the reference signal in configurations for channel estimation in a horizontal direction, in a vertical direction, and between polarizations using a part of the antenna elements including a reference antenna element, and   wherein the user equipment is configured to feedback the horizontal channel information, the vertical channel information, and the inter-polarization channel information relative to the reference antenna element.   
     
     
         3 . The radio communication system according to  claim 1 ,
 wherein the radio base station is configured to change over a group of the antenna elements used to transmit the reference signal in terms of time or frequency, based upon the different configurations.   
     
     
         4 . The radio communication system according to  claim 3 ,
 wherein the radio base station is configured to prioritize a less frequent transmit configuration over other configurations when transmission timings of the two or more different configurations come into collision.   
     
     
         5 . The radio communication system according to  claim 1 ,
 wherein the user equipment is configured to feedback the horizontal channel information and the vertical channel information using different methods according to the referenced signal transmitted in the different configurations.   
     
     
         6 . The radio communication system according to  claim 1 ,
 wherein the user equipment is configured to create the horizontal channel information and the inter-polarization channel information based upon the reference signal transmitted in the different configurations, then create a matrix in which the horizontal channel information and the inter-polarization channel information are incorporated in the vertical channel information, and feed back the matrix to the radio base station.   
     
     
         7 . The radio communication system according to  claim 1 ,
 wherein the user equipment is configured to select existing channel information designed for a one-dimensional antenna array based upon the reference signal transmitted in the different configurations, create a matrix in which the existing channel information is incorporated in the vertical channel information, and feed back the matrix to the radio base station.   
     
     
         8 . The radio communication system according to  claim 1 ,
 wherein the user equipment is configured to select existing channel information designed for a one-dimensional antenna array based upon the reference signal transmitted in the different configurations, and feed back the selected existing channel information to the radio base station.   
     
     
         9 . A radio base station apparatus comprising:
 a plurality of antenna elements arranged two-dimensionally;   a signal generator configured to generate a reference signal used for channel estimation;   a controller configured to select a part or all of the antenna elements to cause the reference signal to be transmitted in two or more different configurations including at least one of a horizontal relationship, a vertical relationship, and an inter-polarization relationship; and   a transmitter configured to transmit the reference signal in the different configurations based upon an output from the controller.   
     
     
         10 . The radio base station apparatus according to  claim 9 ,
 wherein the controller is configured to set up configurations for channel estimation in a horizontal direction, in a vertical direction, and between polarizations using a part of the antenna elements including a reference antenna element, and   the transmitter is configured to transmit the reference signal in the configurations set up by the controller.   
     
     
         11 . The radio base station apparatus according to  claim 9 ,
 wherein the controller is configured to change over a group of the antenna elements used to transmit the reference signal in terms of time or frequency, based upon the different configurations.   
     
     
         12 . The radio base station apparatus according to  claim 11 ,
 wherein the controller is configured to prioritize a less frequent transmit configuration over other configurations when transmission timings of the two or more different configurations come into collision.   
     
     
         13 . A user equipment comprising:
 a receiver configured to receive a reference signal transmitted from a radio base station in two or more different configurations;   a feedback information generator configured to generate feedback information including at least one of horizontal channel information, vertical channel information, and inter-polarization channel information, based upon the received reference signal; and   a transmitter configured to transmit the feedback information to the radio base station.   
     
     
         14 . The user equipment according to  claim 13 ,
 wherein the feedback information generator is configured to generate the horizontal channel information and the vertical channel information as different types of feedback information according to the different configurations.   
     
     
         15 . The user equipment according to  claim 13 ,
 wherein the feedback information generator is configured to create the horizontal channel information and the inter-polarization channel information based upon the reference signal transmitted in the different configurations, and create a matrix in which the horizontal channel information and the inter-polarization channel information are incorporated in the vertical channel information, and   wherein the transmitter is configured to transmit the matrix or information representing the matrix to the radio base station.   
     
     
         16 . The user equipment according to  claim 13 ,
 wherein the feedback information generator is configured to select existing channel information designed for a one-dimensional antenna array based upon the reference signal transmitted in the different configurations, and create a matrix in which the existing channel information is incorporated in the vertical channel information,   and wherein the transmitter is configured to feed back the matrix or information representing the matrix to the radio base station.   
     
     
         17 . The user equipment according to  claim 13 ,
 wherein the feedback information generator is configured to select existing channel information designed for a one-dimensional antenna array based upon the reference signal transmitted in the different configurations, and   wherein the transmitter is configured to feed back the selected existing channel information to the radio base station.