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;   .Iadd.combining, in said mobile station, information transmitted by said first base station transmitter and information transmitted by said second base station transmitter to reconstruct said message information; .Iaddend.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;   .Iadd.combining, in said mobile station, information transmitted by said first base station transmitter and information transmitted by said second base station transmitter to reconstruct said message information; .Iaddend.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.!. .Iadd.a .Iaddend.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.!. .Iadd.a .Iaddend.mobile station;   .Iadd.combining, in said mobile station, information transmitted by said first base station transmitter and information transmitted by said second base station transmitter to reconstruct said message information; .Iaddend.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 transmitters 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.Iadd.; and   combining, in said mobile station, information transmitted by at least two of said first, second and third base station transmitters to reconstruct said message information.Iaddend..   
     
     
       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.!.   .Iadd.combining, in said mobile station, information transmitted by at least two of said first, second and third base station transmitters to reconstruct said message information; and .Iaddend.   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.!.   .Iadd.combining, in said mobile station, information transmitted by at least two of said first, second and third base station transmitters to reconstruct said message information; and .Iaddend.   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.!.   .Iadd.combining, in said mobile station, information transmitted by at least two of said first, second and third base station transmitters to reconstruct said message information; and .Iaddend.   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..Iadd.   
     
     
       22.  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;   receiving, at said mobile station, radio signals from both said first and said second base station;   performing, at said mobile station, a correlation between said received radio signals and a predetermined pattern;   combining, in said mobile station, information transmitted by said first base station transmitter and information transmitted by said second base station transmitter to reconstruct said 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..Iaddend..Iadd.   
     
     
       23.  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;   combining, in said mobile station, information transmitted by said first base station transmitter and information transmitted by said second base station transmitter using information received from a strongest signal path as well as other signal paths received within a reception window to reconstruct said 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..Iaddend..Iadd.   
     
     
       24.  The method of any one of claims 1, 4, 7, 11, 15, 18, and 21 wherein said step of combining further comprises the step of: using an adaptive equalizer to reconstruct said message information..Iaddend.