Base station, user terminal and radio communication method

Abstract

The present invention is designed so that adequate radio communication is carried out even when discovery signals for existing user terminals and small cell discovery/measurement signals coexist. A base station forms a macro cell having a coverage area to include a small cell, and communicates with a user terminal that can connect with the small cell, and this base station has a commanding section that commands, with respect to a predetermined frequency, one or both of a first discovery process to use a synchronization signal transmitted from the small cell, and a second discovery process to use a discovery/measurement signal transmitted from the small cell, to the user terminal, and a transmitting section that, when the commanding section commands the second discovery process, transmits information about the parameters of the discovery/measurement signal to the user terminal.

1 . A base station that forms a macro cell having a coverage area to include a small cell, and that communicates with a user terminal that can connect with the small cell, the base station comprising:
 a commanding section that commands, with respect to a predetermined frequency, one or both of a first discovery process to use a synchronization signal transmitted from the small cell, and a second discovery process to use a discovery/measurement signal transmitted from the small cell, to the user terminal; and   a transmitting section that, when the commanding section commands the second discovery process, transmits information about parameters of the discovery/measurement signal to the user terminal.   
     
     
         2 . The base station according to  claim 1 , wherein the transmitting section includes and transmits the information about the parameters of the discovery/measurement signal in a same information element with a command for the second discovery process. 
     
     
         3 . The base station according to  claim 1 , wherein the transmitting section includes and transmits the information about the parameters of the discovery/measurement signal in a different information element from a command for the second discovery process. 
     
     
         4 . The base station according to  claim 1 , wherein, when the commanding section commands the first discovery process and the second discovery process, the transmitting section transmits information about resources that are not subject to the second discovery, to the user terminal. 
     
     
         5 . The base station according to  claim 1 , wherein the transmitting section includes the information about the parameters of the discovery/measurement signal in broadcast information and transmits the broadcast information to a user terminal in idle mode. 
     
     
         6 . The base station according to  claim 5 , wherein the transmitting section includes a frequency and transmission timing of the discovery/measurement signal in an SIB and transmits the SIB. 
     
     
         7 . The base station according to  claim 1 , further comprising a receiving section that receives at least part of a result of the first discovery process and a result of the second discovery process as a measurement report each,
 wherein connection of the user terminal with the small cell is controlled based on the measurement reports.   
     
     
         8 . A user terminal that communicates with a base station that forms a small cell and a base station that forms a macro cell having a coverage area to include the small cell, the user terminal comprising:
 a discovery process section that executes a first discovery process to use a synchronization signal and a reference signal transmitted from the small cell, and a second discovery process to use a discovery/measurement signal transmitted from the small cell; and   a receiving section that receives information about parameters of the discovery/measurement signal,   wherein, when a command for the second discovery process for a predetermined frequency is reported from the macro cell, the discovery process section performs the second discovery process based on the information about the parameters of the discovery/measurement signal.   
     
     
         9 . The user terminal according to  claim 8 , further comprising a transmitting section that transmits at least part of a result of the first discovery process and a result of the second discovery process as a measurement report each,
 wherein the transmitting section controls whether or not to transmit the measurement reports based on event triggers that are configured separately for the result of the first discovery/measurement process and the result of the second discovery/measurement process.   
     
     
         10 . A radio communication method for a base station that forms a small cell, a base station that forms a macro cell having a coverage area to include the small cell, and a user terminal, the radio communication method comprising the steps of:
 commanding, with respect to a predetermined frequency, one or both of a first discovery process to use a synchronization signal transmitted from the small cell, and a second discovery process to use a discovery/measurement signal transmitted from the small cell, from the base station forming the macro cell to the user terminal; and   when the second discovery process is commanded, transmitting information about parameters of the discovery/measurement signal to the user terminal.