Mobile station assisted soft handoff in a CDMA cellular communications system
First Claim
1. 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 comprising the steps of:
- measuring at a mobile station signal strength of base station transmitted pilot signals;
communicating a signal strength message, from said mobile station via at least one base station said mobile station is in communication with, when at least one measured pilot signal each corresponding to a base station to which said mobile station is not currently in communication with, exceeds a first predetermined level;
communicating, from at least one of said base stations said mobile station is in communication with and each base station corresponding to said mobile station measured pilot signal exceeding said first predetermined level, a direction message; and
establishing, at said mobile station in response to said direction message, communications through each base station corresponding to said mobile station measured pilot signal exceeding said first predetermined level.
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Accused Products
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.
994 Citations
37 Claims
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1. 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 comprising the steps of:
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measuring at a mobile station signal strength of base station transmitted pilot signals; communicating a signal strength message, from said mobile station via at least one base station said mobile station is in communication with, when at least one measured pilot signal each corresponding to a base station to which said mobile station is not currently in communication with, exceeds a first predetermined level; communicating, from at least one of said base stations said mobile station is in communication with and each base station corresponding to said mobile station measured pilot signal exceeding said first predetermined level, a direction message; and establishing, at said mobile station in response to said direction message, communications through each base station corresponding to said mobile station measured pilot signal exceeding said first predetermined level. - View Dependent Claims (2, 3, 4, 5)
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6. In a 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 an identifying 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 by a system controller comprising the steps of:
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providing to said mobile station a first list identifying a first set of base stations; measuring at said mobile station signal strength of said pilot signals transmitted by of each base station of said first set of base stations; comparing said measured pilot signal strength to a first predetermined level; generating at said mobile station a second list identifying a second set of base stations by removing from said first list a base station listing having a pilot signal strength measurement of a corresponding base station which exceeds said first predetermined level and placing said base station listing in said second list; providing by said mobile station said second list to said system controller; providing to said system controller from said base station identified in said second list availability information about resources at each of said base stations identified in said second list; generating at said system controller a third list identifying a third set of base stations based on said first list, said second list and said base station availability information; providing to said mobile station by said system controller said third list; removing at said mobile station each base station listing of said third set of base stations from said first list and said second list; and communicating by said mobile station through said third set of base stations. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. In a cellular communication system in which a system controller directs communications between a mobile station and at least one base station, a method for mobile station assisted communications directing, comprising the steps of:
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storing in said mobile station an active list of base stations entries, wherein each entry in said active list corresponds to a base station in communication with said mobile station; storing in said mobile station a candidate list of base stations entries, wherein each entry in said candidate list corresponds to a base station having sufficient signal strength to establish communication with said mobile station; transmitting from each base station of said current system a signal identifying said base station; measuring at said mobile station a signal strength of said corresponding base station transmitted signal for each of said entries in said active list; measuring at said mobile station a signal strength of said corresponding base station transmitted signal for each of said entries in said candidate list; comparing said measurement of each of said candidate list entries to each of said measurements of said active list entries; and identifying by said mobile station to said system controller a particular base station having an entry on said candidate list and another base station having an entry on said active list, if a measurement of said particular base station exceeds a measurement of said another base station by a predetermined amount, T-- COMP. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. In a cellular communication system in which a system controller directs communications between a mobile station and at least one base station, a method for mobile station assisted communications directing, comprising the steps of:
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identifying by said system controller to said mobile station a first set of base stations which are in a predetermined proximity of said mobile station; measuring at said mobile station a signal strength of a signal transmitted by each base station in said first set of base stations; identifying to said system controller by said mobile station a second set of base stations from said first set of base stations having said measured signal strengths sufficient at said mobile station to establish communications therewith; identifying by said system controller to said mobile station a third set of base stations corresponding to at least one base station of said second set having available resources to establish communication with said mobile station; notifying by said system controller each base station of said third set of base stations not currently in communication with said mobile station to establish communication with said mobile station; and establishing communications by said mobile station and each base station of said third set of base stations not currently in communication therewith. - View Dependent Claims (35, 36)
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37. In a cellular communication system in which a system controller controls a handoff in communications between a mobile station and a plurality of base stations, a method for mobile station assisted handoff in said communications comprising the steps of:
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identifying by said system controller to said mobile station a first set of base stations which are in a predetermined proximity of said mobile station; measuring at said mobile station a signal strength of a signal transmitted by each base station in said first set of base stations; determining at said mobile station from said signal strength measurements a second set of base stations, wherein said signal strength measurement of each base station of said second set of base stations is indicative of signal level sufficient to establish communication with said mobile station; identifying by said mobile station to said system controller said second set of base stations; determining at said system controller from said second set of base stations a third set of base stations having resources available to establish communication with said mobile station; notifying by said system controller each base station of said third set of base stations and said mobile station to establish communications between each base station of said third set of base stations if communications therebetween are not currently present; establishing communication between each base station of said third set of base stations and said mobile station if communications therebetween are not currently present; and terminating existing communication between said mobile station and each base station absent from said third set of base stations.
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Specification