Radio communication system, communication terminal apparatus, base station apparatus, and transmission power control method

Abstract

The present invention relates to a radio communication system comprising base stations and mobile stations and a method for controlling transmission power in the system where the base station is able to perform multi-point transmission for transmitting the same signal to a plurality of the mobile stations. In the present invention, the mobile station targeted for the multi-point transmission provides the base station of an increase request or a decrease request of the transmission power by respectively transmitting or not transmitting a predetermined signal to the base station.

1 . A method for controlling transmission power in a radio communication system comprising a base station and a mobile station where the base station is able to perform multi-point transmission for transmitting the same signal to a plurality of the mobile stations, wherein: 
 the mobile station targeted for the multi-point transmission provides the base station of an increase request or a decrease request of the transmission power by respectively spreading or not spreading a transmission power control signal to the base station with a predetermined code sequence.    
   
   
       2 . The method for controlling the transmission power as claimed in  claim 1 , wherein: 
 the multi-point transmission target mobile station determines contents of the transmission power control to be requested to the base station on the basis of receiving quality of received signal from the base station, and transmits the transmission power control signal to the base station after spreading that signal with a predetermined code sequence when the contents of the transmission power control is determined to be the increase request of the transmission power to the base station; and    the base station calculates correlation between the signal received from the multi-point transmission target mobile station and the predetermined code sequence pre-stored, and increases the transmission power to the multi-point transmission target mobile station if the correlation value exceeds a predetermined threshold and decreases the transmission power if the correlation value does not exceed the predetermined threshold.    
   
   
       3 . The method for controlling the transmission power as claimed in  claim 1 , wherein: 
 a set of the mobile stations consisting of the multi-point transmission target mobile stations to which the base station transmits the same signal is referred to as a multi-point transmission group; and    the predetermined code sequence is different for each multi-point transmission group.    
   
   
       4 . A radio communication system comprising a base station and a mobile station where the base station is able to perform multi-point transmission for transmitting the same signal to a plurality of the mobile stations, wherein: 
 the mobile station targeted for the multi-point transmission provides the base station of an increase request or a decrease request of the transmission power by respectively spreading or not spreading a transmission power control signal to the base station with a predetermined code sequence.    
   
   
       5 . A communication terminal device acting as a mobile station communicating with a base station in a radio communication system and comprising a transmission power control requesting part for requesting the base station to increase or decrease the transmission power on the basis of receiving quality of received signal from the base station, wherein: 
 the transmission power control requesting part provides the base station of an increase request or a decrease request of the transmission power by respectively spreading or not spreading a transmission power control signal to the base station with a predetermined code sequence.    
   
   
       6 . The communication terminal device as claimed in  claim 5 , wherein: upon being targeted for the multi-point transmission where the same signal is transmitted from the base station, the transmission power control requesting part uses, in code sequences provided to be different for each multi-point transmission group, a code sequence assigned for the multi-point transmission group as the predetermined code sequence.