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

Abstract

The present invention is designed to establish synchronization between transmission points when downlink signals are transmitted from a plurality of transmission points to a user terminal. A radio communication system has a first radio base station that forms a first cell, a second radio base station that forms a second cell, which is placed on the area of the first cell in an overlapping manner, and a user terminal that is capable of carrying out radio communication with the first radio base station and the second radio base station, and the second radio base station has a receiving section that receives synchronization correction information, which is for establishing synchronization with a synchronization target, from the user terminal, and a synchronization correction section that corrects synchronization based on the synchronization correction information.

1 . A radio communication system comprising a first radio base station that forms a first cell, a second radio base station that forms a second cell, which is placed on an area of the first cell in an overlapping manner, and a user terminal that is capable of carrying out radio communication with the first radio base station and the second radio base station, wherein the second radio base station comprises:
 a receiving section that receives synchronization correction information, which is for establishing synchronization with a synchronization target, from the user terminal; and   a synchronization correction section that corrects synchronization based on the synchronization correction information.   
     
     
         2 . The radio communication system according to  claim 1 , wherein:
 the second radio base station further comprises:   a generating section that generates a synchronization signal, which is used to estimate information about desynchronization as the synchronization correction information in the user terminal; and   a transmitting section that transmits the synchronization signal to the user terminal; and   the user terminal comprises:   a receiving section that receives the synchronization signal; and   an estimation section that estimates desynchronization between the second cell and the synchronization target based on the synchronization signal received.   
     
     
         3 . The radio communication system according to  claim 1 , wherein:
 the user terminal comprises a generating section that generates the synchronization correction information; and   the second radio base station further comprises an estimation section that estimates information about desynchronization with the synchronization target in accordance with the synchronization correction information.   
     
     
         4 . The radio communication system according to  claim 3 , wherein the synchronization correction information is a RACH (Random Access Channel) signal. 
     
     
         5 . The radio communication system according to  claim 2 , wherein the synchronization target is the first cell or a GPS (Global Positioning System) clock. 
     
     
         6 . The radio communication system according to  claim 3 , wherein the synchronization target is the first cell or a GPS (Global Positioning System) clock. 
     
     
         7 . The radio communication system according to  claim 2 , wherein the synchronization target is another second cell that is placed near the second cell where the second radio base station is placed. 
     
     
         8 . (canceled) 
     
     
         9 . A radio base station in a radio communication system comprising a first radio base station that forms a first cell, a second radio base station that forms a second cell, which is placed on an area of the first cell in an overlapping manner, and a user terminal that is capable of carrying out radio communication with the first radio base station and the second radio base station, the radio base station comprising:
 a receiving section that receives synchronization correction information, which is for establishing synchronization with a synchronization target, from the user terminal;   a synchronization correction section that corrects synchronization based on the synchronization correction information;   a generating section that generates a synchronization signal, which is used to estimate information about desynchronization as the synchronization correction information in the user terminal; and   a transmitting section that transmits the synchronization signal to the user terminal.   
     
     
         10 . A user terminal in a radio communication system comprising a first radio base station that forms a first cell, a second radio base station that forms a second cell, which is placed on an area of the first cell in an overlapping manner, and the user terminal that is capable of carrying out radio communication with the first radio base station and the second radio base station, the user terminal comprising:
 a receiving section that receives a synchronization signal; and   an estimation section that estimates desynchronization between the second cell and a synchronization target based on the synchronization signal received.