Mobile station assisted soft handoff in a CDMA cellular communications system
First Claim
1. In a cellular communication system in which a mobile user communicates with other users via at least one base station, wherein each of a plurality of base stations within said system transmits a unique pilot signal, a mobile station transceiver comprising:
- a pilot signal strength measurement circuit for measuring strength of base station transmitted pilot signals and for generating a first signal strength message when one or more of said measured pilot signals, from base stations not currently in communication with said mobile station transceiver, exceed a first predetermined level;
a mobile station transmitter for transmitting said first signal strength message to at least one of said base stations with which said mobile user is currently in communication; and
a mobile station receiver for receiving a first direction signal from at least one of said base stations with which said mobile user is currently in communication;
wherein in response to said first received direction signal communication is established between said mobile station transceiver and at least one of said base stations from which were received said measured pilot signals exceeding said first predetermined level.
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Abstract
In a code division multiple access (CDMA) spread spectrum cellular communication system in which a mobile station user communicates with another system user via at least one base station, wherein each base station transmits a common pilot signal of a different code phase with respect to other base stations in said system, a method for directing communications between said mobile station user and said base stations. The mobile station monitors the signal strength of pilots and reports the measured signal strength to a system controller via the base station through which it is communicating. Command messages from the system controller to a new base station and the mobiles station establishes communication through the new base station in addition to the communication through the current base station. When the mobile station detects the falling below a predetermined level of the signal strength of a pilot corresponding to at least one of the base stations through which the mobile station is communicating, the mobile station reports the measured signal strength indicative of the corresponding base station to the system controller via the base stations through which it is communicating. Command messages from the system controller to the identified base station and the mobiles station terminates communication through the corresponding base station while communications through the other base station or base stations continue.
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Citations
15 Claims
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1. In a cellular communication system in which a mobile user communicates with other users via at least one base station, wherein each of a plurality of base stations within said system transmits a unique pilot signal, a mobile station transceiver comprising:
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a pilot signal strength measurement circuit for measuring strength of base station transmitted pilot signals and for generating a first signal strength message when one or more of said measured pilot signals, from base stations not currently in communication with said mobile station transceiver, exceed a first predetermined level; a mobile station transmitter for transmitting said first signal strength message to at least one of said base stations with which said mobile user is currently in communication; and a mobile station receiver for receiving a first direction signal from at least one of said base stations with which said mobile user is currently in communication; wherein in response to said first received direction signal communication is established between said mobile station transceiver and at least one of said base stations from which were received said measured pilot signals exceeding said first predetermined level. - View Dependent Claims (2, 3)
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4. In a cellular communication system in which a mobile user communicates through a mobile station transceiver with other users via at least one base station, wherein each base station in said system transmits a unique pilot signal and wherein each base station is in communication with a system controller, said mobile station transceiver comprising:
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a pilot signal strength measurement circuit for measuring signal strength of base station transmitted pilot signals from base stations included in a first list identifying a first set of said base stations; a comparator for comparing said measured pilot signal strengths to a first predetermined level; means for generating a second list identifying a second set of base stations by including within said second list those of said base stations on said first list for which said measured pilot signal strengths exceeded said first predetermined level; a mobile station transmitter for transmitting said second list to at least a first of said base stations with which said mobile station transceiver is currently in communication; a mobile station receiver for receiving, from at least one of said base stations with which said mobile unit transceiver is currently in communication, a third list identifying a third set of base stations available for communication with said mobile station transceiver, said third list being generated by said system controller in accordance with said second list of base stations and on the basis of base station availability information; and a mobile station controller for directing said mobile station transceiver to establish communication with said third set of base stations. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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11. In a cellular telephone system in which a mobile system user and another system user communicate user information signals therebetween via at least one of a plurality of geographically separated cell-sites each defining a respective geographic service area, said cellular telephone system including a system controller for directing communications between system users of said cellular telephone system, a mobile station transceiver utilized by said mobile system user for communicating with said another system user via said at least one of said plurality of cell-sites, said mobile station transceiver comprising:
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a mobile station controller for determining, while said mobile system user is in a service area of one cell-site and communicating user information signals with said another system user via said one cell-site, a transition of said mobile system user from said one cell-site service area to a service area of another cell-site, said system controller being operative to generate a handoff request in response to said determination of said transition into said service area of said another cell-site; a mobile station transmitter for transmitting said handoff request to said one cell-site identifying said another cell-site; and means for concurrently communicating said user information signals between said mobile station transceiver and said one and another cell-sites, said concurrent communication being established by said system controller in accordance with said handoff request. - View Dependent Claims (12)
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13. In a cellular communication system in which a user at a mobile station communicates with another system user via at least one base station, wherein each base station in said system transmits a unique pilot signal, a method for directing communications between said mobile station user and said base stations comprising the steps of:
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measuring at said mobile station signal strength of base station transmitted pilot signals and generating a signal strength message when one or more of said measured pilot signals, from base stations not currently in communication with said mobile station, exceed a first predetermined level; establishing, upon generation of said signal strength message, communication between said mobile station and at least one of the one or more base stations from which were transmitted said one or more measured pilot signals exceeding said first predetermined level. - View Dependent Claims (14, 15)
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Specification