Handover method for mobile radio system

Abstract

The invention relates to a method in mobile radio systems in which the responsibility for transmitting message information to a mobile station (MS 1 , MS 2 ) is handed over from at least a first base station transmitter (B ma , B mb ) to at least a second base station transmitter (B na , B nb ). In accordance with the invention, the same radio channel is used, if possible, before and after the handover for transmitting message information to the mobile station. If the same radio channel can be utilized, the handover takes place without the mobile station being informed beforehand of the handover by a special signal or order or the like. In digital mobile radio systems with digital transmission of message information by digital modulation of the radio signals, the transmission is preferably started from a second base station transmitter before the transmission is terminated from a first base station transmitter. During a transmission time substantially the same message information is transmitted to the mobile station from both at least one first and one second base station transmitter.

I claim:  
     
       1. A method of communication in a cellular mobile radio system having a plurality of base station transmitters and mobile stations comprising the steps of: 
       transmitting, from a first base station transmitter, radio signals digitally modulated with message information to a mobile station;  
       while transmitting the radio signals from the first base station transmitter to the mobile station, beginning to transmit from a second base station transmitter to the mobile station radio signals digitally modulated with substantially the same message information; and  
       terminating the transmission from the first base station transmitter to the mobile station while continuing to transmit from the second base station transmitter radio signals digitally modulated with message information to the mobile station.  
     
     
       2. A method according to  claim 1  comprising the step of: 
       transmitting, from a third base station transmitter to the mobile station, radio signals digitally modulated with substantially the same message information as the signals transmitted by the first or second base station transmitters.  
     
     
       3. A method according to  claim 1  further comprising the step of: 
       transmitting, from a fourth base station transmitter to the mobile station, radio signals digitally modulated with substantially the same message information as the signals from the second base station transmitter.  
     
     
       4. A method of communication in a cellular mobile radio system having a plurality of base station transmitters and mobile stations comprising the steps of: 
       transmitting, from a first base station transmitter for a first cell, radio signals digitally modulated with message information to a mobile station;  
       while transmitting the radio signals from the first base station transmitter to the mobile station, beginning to transmit, from a second base station transmitter for a second cell to the mobile station, radio signals digitally modulated with substantially the same message information; and  
       terminating the transmission from the first base station transmitter to the mobile station while continuing to transmit from the second base station transmitter.  
     
     
       5. A method according to  claim 4  further comprising the step of: 
       transmitting, from a third base station transmitter to the mobile station, radio signals digitally modulated with substantially the same message information to as the signals transmitted by the first or second base station transmitters.  
     
     
       6. A method according to  claim 4  comprising the step of: 
       transmitting, from a fourth base station transmitter to the mobile station, radio signals digitally modulated with substantially the same message information as the signals from the second base station transmitter.  
     
     
       7. A method of communication in a cellular mobile radio system having a plurality of base station transmitters and mobile stations comprising the steps of: 
       transmitting, from a first base station transmitter to a mobile station, radio signals digitally modulated with message information to the mobile station;  
       transmitting, from a second base station transmitter to the mobile station, radio signals digitally modulated with substantially the same message information to the mobile station; and  
       before terminating the transmission from the first or second base station transmitter of the digitally modulated radio signals to the mobile station, beginning to transmit from a third base station transmitter radio signals digitally modulated with substantially the same message information as the signals from the first and second base station transmitters.  
     
     
       8. A method according to  claim 7  further comprising the step of: 
       terminating the transmission from the first base station transmitter to the mobile station while continuing to transmit from the second and third base station transmitters radio signals digitally modulated with substantially the same message information to the mobile station.  
     
     
       9. A method according to  claim 7  further comprising the step of: 
       terminating the transmission from the second base station transmitter while continuing to transmit from the third base station transmitter radio signals digitally modulated with message information to the mobile station.  
     
     
       10. A method according to  claim 7  further comprising the steps of: 
       before terminating the transmission of the digitally modulated signals from the second base station transmitter, beginning to transmit from a fourth base station transmitter to the mobile station radio signals digitally modulated with substantially the same message information as the signals from the second and third base station transmitters; and  
       terminating the transmission from the second base station transmitter while continuing to transmit from the third and fourth base station transmitters radio signals digitally modulated with substantially the same message information to the mobile station.  
     
     
       11. A method of communication in a cellular mobile radio system having a plurality of base station transmitters and mobile stations comprising the steps of: 
       transmitting, from a first base station transmitter, for a first cell radio signals digitally modulated with message information to a mobile station;  
       transmitting from a second base station transmitter radio signals digitally modulated with substantially the same message information to the mobile station; and  
       before terminating the transmission from the first or second base station transmitter to the mobile station, beginning to transmit from a third base station transmitter for a second cell radio signals digitally modulated with substantially the same message information as the signals from the first and second base station transmitters.  
     
     
       12. A method according to  claim 11  further comprising the step of: 
       terminating the transmission from the first base station transmitter while continuing to transmit from the second and third base station transmitters radio signals digitally modulated with substantially the same message information to the mobile station.  
     
     
       13. A method according to  claim 11  further comprising the step of: 
       terminating the transmission from the second base station transmitter while continuing to transmit from the third base station transmitter radio signals digitally modulated with message information to the mobile station.  
     
     
       14. A method according to  claim 11  further comprising the step of: 
       before terminating the transmission from the second base station transmitter, beginning to transmit from a fourth base station transmitter to the mobile station radio signals digitally modulated with substantially the same message information as the signals from the second and third base station transmitters; and  
       terminating the transmission from the second base station transmitter while continuing to transmit from the third and fourth base station transmitters radio signals digitally modulated with substantially the same message information to the mobile station.  
     
     
       15. A method of communication in a cellular mobile radio system having a plurality of base station transmitters and mobile stations comprising the steps of: 
       transmitting, from a first base station transmitter, radio signals digitally modulated with message information to a mobile station;  
       transmitting, from a second base station transmitter, radio signals digitally modulated with substantially the same message information to the mobile station;  
       before terminating the transmission from the first or second base station transmitter to the mobile station, beginning to transmit from a third base station transmitter radio signals digitally modulated with substantially the same message information as the signals from the first and second base station transmitters; and  
       terminating the transmission from the first base station transmitter while continuing to transmit from the second and third base station transmitters radio signals digitally modulated with substantially the same message information to the mobile station.  
     
     
       16. A method according to  claim 15  further comprising the step of: 
       terminating the transmission from the second base station transmitter while continuing to transmit from the third base station transmitter radio signals digitally modulated with message information to the mobile station.  
     
     
       17. A method according to  claim 15  further comprising the steps of: 
       before terminating the transmission from the second base station transmitter, beginning to transmit from a fourth base station transmitter to the mobile station radio signals digitally modulated with substantially the same message information as the signals from the second and third base station transmitters; and  
       terminating the transmission from the second base station transmitter while continuing to transmit from the third and fourth base station transmitters radio signals digitally modulated with substantially the same message information to the mobile station.  
     
     
       18. A method of communication in a cellular mobile radio system having a plurality of base station transmitters and mobile stations comprising the steps of: 
       transmitting, from a first base station transmitter for a first cell, radio signals digitally modulated with message information to a mobile station;  
       transmitting, from a second base station transmitter, radio signals digitally modulated with substantially the same message information to the mobile station;  
       before terminating the transmission from the first or second base station transmitter to the mobile station, beginning to transmit from a third base station transmitter for a second cell radio signals digitally modulated with substantially the same message information as the signals from the first and second base station transmitters; and  
       terminating the transmission from the first base station transmitter while continuing to transmit from the second and third base station transmitters radio signals digitally modulated with substantially the same message information to the mobile station.  
     
     
       19. A method according to  claim 18  further comprising the step of: 
       terminating the transmission from the second base station transmitter while continuing to transmit from the third base station transmitter radio signals digitally modulated with message information to the mobile station.  
     
     
       20. A method according to  claim 18  further comprising the steps of: 
       before terminating the transmission from the second base station transmitter, beginning to transmit from a fourth base station transmitter to the mobile station radio signals digitally modulated with substantially the same message information as the signals from the second and third base station transmitters; and  
       terminating the transmission from the second base station transmitter while continuing to transmit from the third and fourth base station transmitters radio signals digitally modulated with substantially the same message information to the mobile station.  
     
     
       21. A method of communication in a cellular mobile radio system having a plurality of base station transmitters and mobile stations comprising the steps of: 
       transmitting to a mobile station, from each of a first base station transmitter, a second base station transmitter and a third base station transmitter, radio signals digitally modulated with substantially the same message information; and  
       terminating the transmission of the digitally modulated signals from the first base station transmitter to the mobile station while continuing to transmit from the second and third base station transmitters.