Soft handoff in a cellular telecommunications system
First Claim
1. In a cellular telecommunications system in which a user mobile station relays user communication radio signals via at least one of a plurality of base stations and in which said base stations further relay said user communication signals to and from a controlling mobile exchange connected to another system user, said further relay of user communication signals being performed by using digital frames carried on digital transmission connections in the uplink and downlink directions, a method for soft handoff comprising the steps ofinitiating a soft handoff with diversity combining so as to cause said controlling mobile exchange communicate concurrently with said mobile station via a first base station and a second base station,transmitting a first transmission of said user communication frames in the uplink and downlink directions between the controlling mobile exchange and said first base station on a first digital transmission connection,first buffering of said downlink user communication frames in said first base station prior to a radio transmission from said first base station to said mobile station,first sending of time alignment requests with regard to said user communication frames, from said first base station to said controlling mobile exchange, said time alignment requests being intended for a first controlling of the delay of said first buffering at said first base station,transmitting a second transmission of said user communication frames in the uplink and downlink directions between the controlling mobile exchange and said second base station on a second digital transmission connection,second buffering of said downlink user communication frames in said second base station prior to a radio transmission from said second base station to said mobile station,second sending of time alignment requests with regard to said user communication frames, from said second base station to said controlling mobile exchange, said time alignment requests being intended for a second controlling of the delay of said second buffering at said second base station,third buffering of downlink communication signals from said other system user at said controlling mobile exchange,processing of said buffered downlink communication signals from said other system user at said controlling mobile exchange, said processing resulting in said downlink user communication frames,fourth buffering of said processed downlink user communication frames in said controlling mobile exchange prior to said first downlink transmission from said controlling mobile exchange to said first base station, the frame time alignment of said first downlink transmission being responsive to said first time alignment requests,fifth buffering of said processed downlink user communication frames in said controlling mobile exchange prior to said second downlink transmission from said controlling mobile exchange to said second base station, the frame time alignment of said second downlink transmission being responsive to said second time alignment requests.
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Accused Products
Abstract
A soft handoff in a cellular telecommunications system in which a user mobile station relays user communication radio signals via at least two base stations to and from a controlling mobile exchange connected to another system user. The relay of user information signals is performed by using digital frames carried on digital transmission connections in the uplink and downlink directions. The differential delay of the two or more terrestial routes between the base stations and the exchange is compensated by a novel time alignment procedure. Each of the base stations sends time alignment request to the mobile exchange which performs the frame time alignment of the downlink transmissions by taking into account TA requests from all base stations.
121 Citations
16 Claims
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1. In a cellular telecommunications system in which a user mobile station relays user communication radio signals via at least one of a plurality of base stations and in which said base stations further relay said user communication signals to and from a controlling mobile exchange connected to another system user, said further relay of user communication signals being performed by using digital frames carried on digital transmission connections in the uplink and downlink directions, a method for soft handoff comprising the steps of
initiating a soft handoff with diversity combining so as to cause said controlling mobile exchange communicate concurrently with said mobile station via a first base station and a second base station, transmitting a first transmission of said user communication frames in the uplink and downlink directions between the controlling mobile exchange and said first base station on a first digital transmission connection, first buffering of said downlink user communication frames in said first base station prior to a radio transmission from said first base station to said mobile station, first sending of time alignment requests with regard to said user communication frames, from said first base station to said controlling mobile exchange, said time alignment requests being intended for a first controlling of the delay of said first buffering at said first base station, transmitting a second transmission of said user communication frames in the uplink and downlink directions between the controlling mobile exchange and said second base station on a second digital transmission connection, second buffering of said downlink user communication frames in said second base station prior to a radio transmission from said second base station to said mobile station, second sending of time alignment requests with regard to said user communication frames, from said second base station to said controlling mobile exchange, said time alignment requests being intended for a second controlling of the delay of said second buffering at said second base station, third buffering of downlink communication signals from said other system user at said controlling mobile exchange, processing of said buffered downlink communication signals from said other system user at said controlling mobile exchange, said processing resulting in said downlink user communication frames, fourth buffering of said processed downlink user communication frames in said controlling mobile exchange prior to said first downlink transmission from said controlling mobile exchange to said first base station, the frame time alignment of said first downlink transmission being responsive to said first time alignment requests, fifth buffering of said processed downlink user communication frames in said controlling mobile exchange prior to said second downlink transmission from said controlling mobile exchange to said second base station, the frame time alignment of said second downlink transmission being responsive to said second time alignment requests.
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9. A cellular telecommunications system comprising
a plurality of mobile exchanges, a plurality of base stations, and a user mobile station relaying user communication radio signals via at least one of said base stations, said one of the base stations further relaying said user communication signals to and from a controlling mobile exchange connected to another system user, and said relay of user communication signals being performed by using digital frames carried on digital transmission connections in uplink and downlink directions, means for initiating a soft handoff with diversity combining so as to cause said controlling mobile exchange communicate concurrently with said mobile station via a first base station and a second base station, first transmission means for transmitting said user communication frames in the uplink and downlink directions between the controlling mobile exchange and said first base station on a first digital transmission connection, first buffering means for buffering said downlink user communication frames in said first base station prior to a radio transmission from said first base station to said mobile station, first sending means for sending time alignment requests with regard to said user communication frames, from said first base station to said controlling mobile exchange, said time alignment requests being intended for a first controlling of the delay of said first buffering means at said first base station, second transmitting means for transmitting user communication frames in the uplink and downlink direction between the controlling mobile exchange and said second base station on a second digital transmission connection, second buffering means for buffering said downlink user communication frames in said second base station prior to a radio transmission from said second base station to said mobile station, second sending means for sending time alignment requests with regard to said user communication frames, from said second base station to said controlling mobile exchange, said time alignment requests being intended for a second controlling of the delay of said second buffering means at said second base station, third buffering means for buffering downlink communication signals from said other system user at said controlling mobile exchange, processing means for processing said buffered downlink communication signals from said other system user at said controlling mobile exchange, said processing resulting in said downlink user communication frames, fourth buffering means for buffering said processed downlink user communication frames in said controlling mobile exchange prior to said first downlink transmission from said controlling mobile exchange to said first base station, the frame time alignment of said first downlink transmission being responsive to said first time alignment requests, fifth buffering means for buffering said processed downlink user communication frames in said controlling mobile exchange prior to said second downlink transmission from said controlling mobile exchange to said second base station, the frame time alignment of said second downlink transmission being responsive to said second time alignment requests.
Specification