Cellular communication system, and mobile and base stations used in the same

Abstract

When a mobile station becomes a soft handover state, a reception quality monitor 104 measures reception quality of a pilot signal from each base station. Base station specifying means 105 generates a base-station select signal (BSse1) to specify base stations that have transmitted pilot channels of inferior reception quality. The base-station select signal is multiplexed with transmission data (r-txd), and the multiplexed signal is spread at a spreading circuit. The spread signal is transmitted to plural base stations through a transmitter 111 and a duplexer 102. Then the base stations specified by this base-station specify signal stops transmission of downward signals.

1. A cellular system using a direct spread code division multiple access system, in which a mobile station performs soft handover with plural base stations, said mobile station comprising:
 downward reception quality monitoring means for monitoring reception quality of downward signals from the plural base stations that are in the soft handover state;    base-station specifying means for comparing reception quality of downward signals from respective base stations monitored at said downward reception quality monitoring means, and for generating a base-station specify signal which specifies a base-station having the best reception quality monitoring result to maintain a signal transmission;    multiplexing means for multiplexing the base-station specify signal into an upward signal to be sent to said plural base stations; and    reception means for performing combined reception of receive signals from said plural base stations that are in the soft handover state, and    
       said base stations each comprising:
 demodulation means for demodulating the base-station specify signal multiplexed in the upward signal; and  
 transmission control means for receiving the base-station specifying signal demodulated by said demodulation means, for keeping a downward signal transmission when its own base station is specified in the base-station specify signal, and for stopping a downward signal transmission when its own base station is not specified in the base-station specify signal.  
 
     
     
       2. The cellular system according to  claim 1 , wherein said transmission control means ignores contents of said base-station specify signal and keeps a downward signal transmission when an error in the base-station specify signal is detected. 
     
     
       3. The cellular system according to  claim 1 , wherein said base station specifying means generates a base-station specify signal which specifies plural base stations each having a smaller difference of downward reception quality monitoring result than a predetermined value to maintain a signal transmission. 
     
     
       4. The cellular system according to  claim 1 , wherein said base station specifying means generates a base-station specify signal which specifies plural base stations each having smaller reception quality monitoring result than a predetermined value to maintain a signal transmission. 
     
     
       5. In a cellular system using a direct spread code division multiple access system, a mobile station used in the cellular system for performing soft handover with plural base stations, comprising:
 downward reception quality monitoring means for monitoring reception quality of downward signals from the plural base stations that are in the soft handover state;    base-station specifying means for comparing reception quality of downward signals from respective base stations monitored at said downward reception quality monitoring means, and for generating a base-station specify signal which specifies a base-station having the best reception quality monitoring result to maintain a signal transmission;    multiplexing means for multiplexing the base-station specify signal into an upward signal to be sent to said plural base stations; and    reception means for performing combined reception of receive signals from said plural base stations that are in the soft handover state.    
     
     
       6. The mobile station according to  claim 5 , wherein said base station specifying means generates a base-station specify signal which specifies plural base stations each having a smaller difference of reception quality monitoring result than a predetermined value to maintain a signal transmission. 
     
     
       7. The mobile station according to  claim 5 , wherein said base station specifying means generates a base-station specify signal which specifies plural base stations each having smaller reception quality monitoring result than a predetermined value to maintain a signal transmission. 
     
     
       8. A base station provided in a cellular system in which a plurality of mobile stations according to  claim 5  are utilized, said base station comprising:
 demodulation means for demodulating the base-station specify signal multiplexed in the upward signal; and    transmission control means for receiving the base-station specify signal demodulated by said demodulation means, for keeping a downward signal transmission when its own base station is specified in the base-station specify signal, and for stopping a downward signal transmission when its own base station is not specified in the base-station specify signal.    
     
     
       9. The base station according to  claim 8 , wherein said transmission control means ignores contents of the base-station specify signal and keeps a downward signal transmission when an error is detected in the base-station specify signal. 
     
     
       10. A cellular system using a direct spread code division multiple access system, in which a mobile station performs soft handover with plural base stations, 
       said mobile station comprising:
 reception quality monitoring means for monitoring reception quality of downward signals from the plural base stations that are in the soft handover state and outputting a sub-signal composed of the monitoring results and signals indicative of base stations corresponding to the respective results;  
 multiplexing means for multiplexing the sub-signal into an upward signal to be sent to said plural base stations; and  
 reception means for performing combined reception of receive signals from said plural base stations that are in the soft handover state, and  
 
       said base stations each comprising:
 demodulation means for demodulating the sub-signal multiplexed in the upward signal;  
 transmission halt signal generating means for receiving the sub-signal demodulated by said demodulation means, comparing reception quality of downward signals from respective base stations monitored at the mobile station indicated in the sub-signal, and for generating a transmission halt signal which indicates a signal transmission instruction whether transmission should be allowed or halted at its own base station in accordance with the reception quality monitoring result indicated in the sub-signal; and  
 transmission control means for receiving the transmission halt signal from said transmission halt signal generating means, and for setting a signal transmission state of a downward signal from its own base station, whether a signal transmitting or a signal stopping, in accordance with the instruction indicated in the transmission halt signal.  
 
     
     
       11. The cellular system according to  claim 10 , wherein said transmission halt signal generating means generates the transmission halt signal with an instruction of signal transmission stopped when the best reception quality monitoring result is not indicated for its own base station in the sub-signal, and said transmission control means sets the signal transmitting state of its own base station to a signal stopping condition when the transmission halt signal indicates the instruction of signal transmission stopped. 
     
     
       12. The cellular system according to  claim 10 , wherein said transmission halt signal generating means generates the transmission halt signal with an instruction of signal transmission allowed when an error is detected in the sub-signal, and said transmission control means sets the signal transmitting state of own base station to a signal transmitting condition when the transmission halt signal indicates the instruction of signal transmission allowed. 
     
     
       13. The cellular system according to  claim 10 , wherein said transmission halt signal generating means generates the transmission halt signal with an instruction of signal transmission allowed when reception quality monitoring results of plural base stations in the sub-signal each having smaller difference than a predetermined value, and said transmission control means sets the signal transmitting state of own base station to a signal transmitting when the transmission halt signal indicates the instruction of signal transmission allowed. 
     
     
       14. The cellular system according to  claim 10 , wherein said transmission halt signal generating means generates the transmission halt signal with an instruction of signal transmission allowed when reception quality monitoring results of plural base stations in the sub-signal are smaller than a predetermined value, and said transmission control means sets the signal transmitting state of its own base station to a signal transmitting condition when the transmission halt signal indicates the instruction of signal transmission allowed. 
     
     
       15. A base station provided in a cellular system in which a plurality mobile stations, each equipped with means for monitoring reception quality of downward signals from plural base stations with soft handover state and transmitting a sub-signal composed of the monitoring results for each base station, are utilized, said base station comprising:
 demodulation means for demodulating the sub-signal;    transmission halt signal generating means for receiving the sub-signal demodulated by said demodulation means, comparing reception quality of downward signals from respective base stations monitored at the mobile station indicated in the sub-signal, and for generating a transmission halt signal which indicates a signal transmission instruction whether allowed or halted at its own base station in accordance with the reception quality monitoring result indicated in the sub-signal; and    transmission control means for receiving the transmission halt signal from said transmission halt signal generating means, and for setting a signal transmission state of a downward signal from its own base station, whether a signal transmitting or a signal stopping, in accordance with the instruction indicated in the transmission halt signal.    
     
     
       16. The base station according to  claim 15 , wherein said transmission halt signal generating means generates the transmission halt signal with an instruction of signal transmission allowed when an error is detected in the sub-signal, and said transmission control means sets the signal transmitting state of its own base station to a signal transmitting condition when the transmission halt signal indicates the instruction of signal transmission allowed. 
     
     
       17. The base station according to  claim 15 , wherein said transmission halt signal generating means generates the transmission halt signal with an instruction of signal transmission allowed when reception quality monitoring results of plural base stations in the sub-signal each having a smaller difference each other than a predetermined value, and said transmission control means put the signal transmitting when the transmission halt signal indicates the instruction of signal transmission allowed. 
     
     
       18. The base station according to  claim 15 , wherein said transmission halt signal generating means generates the transmission hall signal with an instruction of signal transmission allowed when reception quality monitoring results of plural base stations in the sub-signal are smaller than a predetermined value, and said transmission control means sets the signal transmitting sate of its own base station to a signal transmitting condition when the transmission halt signal indicates the instruction of signal transmission allowed. 
     
     
       19. A mobile station in a communication system, comprising:
   a monitor which monitors, in a soft handover state, reception qualities of pilot signals from a plurality of base stations;        a base station selector which compares the reception qualities monitored by said monitor and generates a base station select signal specifying a base station on the basis of the reception qualities compared; and        a transmitter which transmits the base station select signal to a first base station that transmits a downward communication channel to said mobile station if the first base station is specified by the base station select signal and to a second base station, among the plurality of base stations, that stops a downward communication channel to said mobile station if the second base station is not specified by the base station select signal.      
     
     
       20. A mobile station according to  claim 19 , further comprising
   a multiplexer which multiplexes the base station select signal and upward data into an upward signal, wherein said transmitter transmits the upward signal.      
     
     
       21. A mobile station according to  claim 19 , wherein
   the base station select signal specifies a base station that is transmitting a pilot signal of the best reception quality.      
     
     
       22. A mobile station in a communication system, comprising:
   a monitor which monitors, in a soft handover state, reception qualities of pilot signals from a plurality of base stations;        a base station selector which compares the reception qualities monitored by said monitor and generates a base station select signal specifying a base station on the basis of the reception qualities compared; and        a transmitter which transmits the base station select signal to all of the plurality of base stations including a base station that is to stop transmission of a downward communication channel to said mobile station if the base station is not specified by the base station select signal.      
     
     
       23. A mobile station in a communication system, comprising:
   a monitoring means for monitoring, in a soft handover state, reception qualities of pilot signals from a plurality of base stations;        a base station selecting means for comparing the reception qualities monitored by said monitor and generating a base station select signal specifying a base station on the basis of the reception qualities compared; and        a transmitting means for transmitting the base station select signal to a first base station that transmits a downward communication channel to said mobile station if the first base station is specified by the base station select signal and to a second base station, among the plurality of base stations, that stops a downward communication channel to said mobile station if the second base station is not specified by the base station select signal.      
     
     
       24. A mobile station in a communication system, comprising:
   a monitoring means for monitoring, in a soft handover state, reception qualities of pilot signals from a plurality of base stations;        a base station selecting means for comparing the reception qualities monitored by said monitor and generating a base station select signal specifying a base station on the basis of the reception qualities compared; and        a transmitting means for transmitting the base station select signal to all of the plurality of base stations including a base station that is to stop transmission of a downward communication channel to said mobile station if the base station is not specified by the base station select signal.      
     
     
       25. A base station among a plurality of base stations in a communication system comprising:
   a receiver which receives, from a mobile station, a base station select signal specifying a base station that is to perform transmission of a downward communication channel to said mobile station, wherein said receiver receives the base station select signal that specifies said base station comprising said receiver or, alternatively, the base station select signal that does not specify said base station comprising said receiver, in a soft handover state with respect to the mobile station; and        a transmitter which transmits a downward communication channel to the mobile station when said base station comprising said transmitter is specified by the base station select signal received, and stops the transmission of the downward communication channel to the mobile station when said base station comprising said transmitter is not specified by the base station select signal received.      
     
     
       26. A base station according to  claim 25 , wherein
   the base station select signal and upward data are multiplexed into an upward signal, and said receiver receives the upward signal.      
     
     
       27. A base station according to  claim 25 , wherein
   the base station select signal specifies the base station that is transmitting a pilot signal of the best receiving quality at the mobile station.      
     
     
       28. A base station among a plurality of base stations in a communication system, comprising:
   a receiver which receives, from a mobile station, a base station select signal that is transmitted to all base stations, among the plurality of base stations, including a base station that is to stop transmission of a downward communication channel to said mobile station if the base station is not specified by the base station select signal; and        a transmitter which transmits the downward communication channel to the mobile station when said base station comprising said transmitter is specified by the base station select signal received.      
     
     
       29. A base station among a plurality of base stations in a communication system comprising:
   a receiver which receives, from a mobile station, a base station select signal specifying a base station that is to perform transmission of a downward communication channel to said mobile station, wherein said receiver receives the base station select signal that specifies its own base station or, alternatively, the base station select signal that does not specify its own base station, in a soft handover state with respect to the mobile station; and        a transmitter which transmits a downward communication channel to the mobile station when said base station comprising said transmitter is specified by the base station select signal received, and stops the transmission of the downward communication channel to the mobile station when said base station comprising said transmitter is not specified by the base station select signal received.      
     
     
       30. A base station among a plurality of base stations in a communication system comprising:
   a receiving means for receiving, from a mobile station, a base station select signal specifying a base station that is to perform transmission of a downward communication channel to said mobile station; and        a transmitting means for transmitting a downward communication channel to the mobile station when said base station comprising said transmitting means is specified by the base station select signal received, and stopping the transmission of the downward communication channel to the mobile station when said base station comprising said transmitting means is not specified by the base station select signal received, wherein        said receiving means receives the base station select signal that specifies said base station comprising said receiving means or, alternatively, the base station select signal that does not specify said base station comprising said receiving means in a soft handover state with respect to the mobile station.      
     
     
       31. A base station among a plurality of base stations in a communication system, comprising:
   a receiving means for receiving, from a mobile station, a base station select signal being transmitted to all base stations, among the plurality of base stations, including a base station that is to stop transmission of a downward communication channel to said mobile station if the base station is not specified by the base station select signal; and        a transmitting means for transmitting the downward communication channel to the mobile station when said base station comprising said transmitting means is specified by the base station select signal received.      
     
     
       32. A base station among a plurality of base stations in a communication system comprising:
   a receiving means for receiving, from a mobile station, a base station select signal specifying a base station that is to perform transmission of a downward communication channel to said mobile station; and        a transmitting means for transmitting a downward communication channel to the mobile station when said base station comprising said transmitting means is specified by the base station select signal received, and stopping the transmission of the downward communication channel to the mobile station when said base station comprising said transmitting means is not specified by the base station select signal received, wherein        said receiving means receives the base station select signal that specifies its own base station or, alternatively, the base station select signal that does not specify its own base station, in a soft handover state with respect to the mobile station.      
     
     
       33. A communication method in a mobile station, comprising:
   monitoring, in a soft handover state, reception qualities of pilot signals from a plurality of base stations;        comparing the reception qualities monitored;        generating a base station select signal specifying a base station on the basis of the reception qualities compared; and        transmitting the base station select signal to a first base station that transmits a downward communication channel to said mobile station if the first base station is specified by the base station select signal and to a second base station, among the plurality of base stations, that stops a downward communication channel to said mobile station if the second base station is not specified by the base station select signal.      
     
     
       34. A communication method in a mobile station, comprising:
   monitoring, in a soft handover state, reception qualities of pilot signals from a plurality of base stations;        comparing the reception qualities monitored;        generating a base station select signal specifying a base station on the basis of the reception qualities compared; and        transmitting the base station select signal to all of the plurality of base stations including a base station that is to stop transmission of a downward communication channel to a mobile station if the base station is not specified by the base station select signal.      
     
     
       35. A communication method, comprising:
   at a base station, receiving, from a mobile station, a base station select signal specifying a base station that is to perform transmission of a downward communication channel to said mobile station, comprising        receiving the base station select signal that specifies said base station receiving the base station select signal or, alternatively, the base station select signal that does not specify said base station receiving the base station select signal, in a soft handover state with respect to the mobile station; and        transmitting, from a transmitter, a downward communication channel to the mobile station when said base station comprising the transmitter is specified by the base station select signal received, and stopping the transmission of the downward communication channel to the mobile station when the base station comprising the transmitter is not specified by the base station select signal received.      
     
     
       36. A communication method in communication system which comprises a plurality of base stations, comprising:
   at a base station, receiving, from a mobile station, a base station select signal that is transmitted to all base stations, among the plurality of base stations, including a base station that is to stop transmission of a downward communication channel to said mobile station if the base station is not specified by the base station select signal; and        transmitting the downward communication channel to the mobile station when said base station receiving the base station select signal is specified by the base station select station receiving the signal received.      
     
     
       37. A communication system comprising a mobile station and a plurality of base stations, wherein
   said mobile station comprises:      a monitor which monitors, in a soft handover state, reception qualities of pilot signals from the plurality of base stations;        a base station selector which compares the reception qualities monitored by said monitor and generates a base station select signal on the basis of the reception qualities compared; and        a transmitter which transmits the base station select signal to a first base station that transmits a downward communication channel to said mobile station if the first base station is specified by the base station select signal and to a second base station, among the plurality of base stations, that stops a downward communication channel to said mobile station if the second base station is not specified by the base station select signal, and          each of the plurality of base stations comprises      a receiver which receives, from said mobile station, the base station select signal that specifics said base station comprising said receiver or, alternatively, the base station select signal that does not specify said base station comprising said receiver in a soft handover state with respect to the mobile station.