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

Abstract

The present invention is designed to make it possible to apply power scaling to a period where the upper limit value is exceeded, while maintaining uplink transmission quality. In a radio communication system 1 in which multiple cells (C 1 and C 2 ) are formed, a base station apparatus ( 20 ) forms a first cell C 1 , which is one of the multiple cells, and has a control section ( 234 ) that controls uplink transmission times per timing group, which includes one component carrier or a plurality of component carriers, and a transmission section ( 106 ) that signals a timing group or a component carrier determined as a target of power scaling, as power scaling target information, in which the timing group or the component carrier, to which power scaling is applied, is expressly determined, to a the user terminal ( 10 ).

1 . A radio communication system, in which multiple cells are formed, and which comprises a plurality of base station apparatuses that each form a cell included in the multiple cells, and a user terminal that can connect to at least a first cell and a second cell included in the multiple cells, wherein:
 the base station apparatuses comprises:
 a control section that controls uplink transmission times per timing group including one component carrier or a plurality of component carriers; and 
 a transmission section that signals a timing group or a component carrier determined as a target of power scaling, as power scaling target information, in which the timing group or the component carrier, to which power scaling is applied, is expressly determined, to the user terminal; and 
   the user terminal comprises:
 a receiving section that receives the power scaling target information signaled from the base station apparatus; 
 a transmission section that transmits uplink signals at different transmission times per timing group; and 
 a power control section that, when a total of uplink signal transmission power over the first cell and the second cell exceeds a predetermined value, applies power scaling to the timing group or the component carrier determined in the power scaling target information. 
   
     
     
         2 . The radio communication system according to  claim 1 , wherein the base station apparatus signals the timing group or the component carrier determined as the target of power scaling to the user terminal through higher layer signaling. 
     
     
         3 . The radio communication system according to  claim 1 , wherein the base station apparatus expressly determines the timing group or the component carrier, to which power scaling is applied, by using, as an indicator, at least one of transmission quality and traffic of the multiple cells, to which the user terminal is connected at the same time. 
     
     
         4 . The radio communication system according to  claim 1 , wherein:
 when component carriers included in each cell, to which the user terminal is connected at the same time, are classified into a plurality of timing groups, the base station apparatus expressly determines a specific physical uplink channel in each timing group as a physical channel, to which power scaling is applied, and signals the target of power scaling per physical channel; and   when the total of uplink signal transmission power over multiple cells, to which the user terminal is connected at the same time, exceeds the predetermined value, the user terminal applies power scaling to the physical channels reported as the target of power scaling.   
     
     
         5 . The radio communication system according to  claim 1 , wherein, when the user terminal is connected to the first cell and the second cell at the same time, the first cell is managed for control signals, the second cell is managed for data transmission, a component carrier included in the first cell is classified as a first timing group, and a component carrier included in the second cell is classified as a second timing group, the base station apparatus expressly determines a physical uplink control channel (PUCCH) of the first timing group, a physical uplink shared channel (PUSCH) of the second timing group, and/or a reference signal (SRS) for channel quality measurement, as physical channels, to which power scaling is applied. 
     
     
         6 . The radio communication system according to  claim 1 , wherein, when the total of uplink signal transmission power over multiple cells, to which the user terminal is connected at the same time, exceeds the predetermined value, the user terminal allocates power to a specific physical uplink channel preferentially, and, excluding the specific physical uplink channel, applies power scaling to the timing group or the component carrier determined as the target of power scaling. 
     
     
         7 . A base station apparatus that forms a cell in a radio communication system where multiple cells are formed, the base station apparatus comprising:
 a control section that controls uplink transmission times per timing group including one component carrier or a plurality of component carriers; and   a transmission section that signals a timing group or a component carrier determined as a target of power scaling, as power scaling target information, in which the timing group or the component carrier, to which power scaling is applied, is expressly determined, to the a user terminal,   wherein the user terminal is connected to multiple cells and controlled to different transmission times per timing group.   
     
     
         8 . A user terminal that connects to multiple cells in a radio communication system where a plurality of base station apparatuses form multiple cells, the user terminal comprising:
 a receiving section that receives power scaling target information signaled from the base station apparatus;   a transmission section that transmits uplink signals at different transmission times per timing group; and   a power control section that, when a total of uplink signal transmission power over connecting cells exceeds a predetermined value, applies power scaling to the timing group or the component carrier determined in the power scaling target information.   
     
     
         9 . A radio communication method in a radio communication system where multiple cells are formed, wherein:
 the radio communication system comprises a plurality of base station apparatuses that each form a cell included in the multiple cells, and a user terminal that can connect to at least a first cell and a second cell included in the multiple cells; and   the radio communication method comprises the steps of:
 controlling uplink transmission times per timing group including one component carrier or a plurality of component carriers; 
 signaling a timing group or a component carrier determined as a target of power scaling, as power scaling target information, in which the timing group or the component carrier, to which power scaling is applied, is expressly determined, to the user terminal; 
 in the user terminal, receiving the power scaling target information signaled from the base station apparatus; 
 transmitting uplink signals at different transmission times per timing group; and 
 when a total of uplink signal transmission power over multiple cells, to which the user terminal is connected at the same time, exceeds a predetermined value, applying power scaling to the timing group or the component carrier determined in the power scaling target information.