Pilot signal searching technique for a cellular communications system
First Claim
1. In a cellular communication system in which a mobile user communicates through a mobile station with other users via at least one base station included in an active list of one or more base station entries, wherein each of a plurality of base stations within said system transmit a unique pilot signal, a method for identifying ones of said base stations from which received signal strength is sufficient to establish communication with said mobile station, said method comprising the steps of:
- maintaining in said mobile station a candidate list of base station entries, wherein each entry in said candidate list corresponds to a base station capable of providing sufficient signal strength to establish communication with said mobile station wherein said active list of one or more base station entries is maintained within said mobile station and is derived from said candidate list of base station entries;
maintaining in said mobile station a neighbor list of base station entries, wherein each entry in said neighbor list corresponds to a base station in a predetermined proximity of said mobile station;
measuring at said mobile station signal strength of each said pilot signal transmitted by each of said base stations in said neighbor list;
comparing at said mobile station said base station signal strength measurements of each of said neighbor list entries to a first predetermined level; and
removing by said mobile station a particular entry from said neighbor list having said base station signal strength measurement greater than said first predetermined level and placing said particular entry in a pre-candidate list maintained in said mobile station, wherein said entries in said pre-candidate list correspond to a set of base stations from which are derived said candidate list of base station entries.
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Accused Products
Abstract
An improved method and system for performing a pilot signal searching operation in anticipation of handoff in mobile station communication between base stations is disclosed herein. The searching operation is described herein as being implemented within a cellular communication system which uses code division multiple access (CDMA) modulation techniques. The mobile station maintains a list of an Active Set of pilot signals transmitted from base stations with which the mobile station is to communicate through, and a Neighbor Set of pilots from base stations within a predetermined proximity of the mobile station. In addition to the Neighbor and Active Sets of pilots, the mobile station maintains a list of Candidate and Pre-Candidate Sets of pilots. Based on analysis of the signal strength of the pilot signals received at the mobile station, base station entries from the Neighbor Set may be assigned to the Pre-Candidate and Candidate Sets, and eventually to the Active set. The searching operation contemplates comparing pilot signal strength measurements corresponding to each base station entry within the Neighbor Set to a first predetermined level. One or more entries from the Neighbor Set having a base station signal strength measurement greater than the first predetermined level may be placed in the Pre-Candidate Set. The strength of the pilot signals associated with entries in the Pre-Candidate Set are then further evaluated to determine eligibility within the Candidate Set, from which are selected the entries comprising the Active Set.
227 Citations
36 Claims
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1. In a cellular communication system in which a mobile user communicates through a mobile station with other users via at least one base station included in an active list of one or more base station entries, wherein each of a plurality of base stations within said system transmit a unique pilot signal, a method for identifying ones of said base stations from which received signal strength is sufficient to establish communication with said mobile station, said method comprising the steps of:
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maintaining in said mobile station a candidate list of base station entries, wherein each entry in said candidate list corresponds to a base station capable of providing sufficient signal strength to establish communication with said mobile station wherein said active list of one or more base station entries is maintained within said mobile station and is derived from said candidate list of base station entries; maintaining in said mobile station a neighbor list of base station entries, wherein each entry in said neighbor list corresponds to a base station in a predetermined proximity of said mobile station; measuring at said mobile station signal strength of each said pilot signal transmitted by each of said base stations in said neighbor list; comparing at said mobile station said base station signal strength measurements of each of said neighbor list entries to a first predetermined level; and removing by said mobile station a particular entry from said neighbor list having said base station signal strength measurement greater than said first predetermined level and placing said particular entry in a pre-candidate list maintained in said mobile station, wherein said entries in said pre-candidate list correspond to a set of base stations from which are derived said candidate list of base station entries. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In a code division multiple access (CDMA) spread spectrum cellular communication system in which a mobile user communicates through a mobile station with other users via at least one base station included in an active list of one more base station entries, wherein each of a plurality of base stations within said system transmit a pilot PN code signal of a unique phase, each of said PN code signals including a predefined sequence of PN chips, a method for identifying ones of said base stations from which received signal strength is sufficient to establish communication with said mobile station, said method comprising the steps of:
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maintaining in said mobile station a candidate list of base station entries, wherein each entry in said candidate list corresponds to a base station capable of providing sufficient signal strength to establish communication with said mobile station wherein said active list of one or more base station entries is maintained within said mobile station and is derived from said candidate list of base station entries; maintaining in said mobile station a neighbor list of base station entries, wherein each entry in said neighbor list corresponds to a base station in a predetermined proximity of said mobile station; measuring at said mobile station signal strength of each said pilot PN code signal transmitted by each of said base stations in said neighbor list; comparing at said mobile station said base station signal strength measurements of each of said neighbor list entries to a first predetermined level; and removing by said mobile station a particular entry from said neighbor list having said base station signal strength measurement greater than said first predetermined level and placing said particular entry in a pre-candidate list maintained in said mobile station, wherein said entries in said precandidate list correspond to a set of base stations from which are derived said candidate list of base station entries. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
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16. In a cellular communication system in which a mobile user communicates through a mobile station with other users via at least one base station included in an active list of one or more base station entries, wherein each of a plurality of base stations within said system transmit a unique pilot signal, a searcher apparatus disposed within said mobile station for identifying ones of said base stations from which received signal strength is sufficient to establish communication with said mobile station, said searcher apparatus comprising:
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a mobile station controller for maintaining a candidate list of base station entries, wherein each entry in said candidate list corresponds to a base station capable of providing sufficient signal strength to establish communication with said mobile station wherein said active list of one or more base station entries is stored within said mobile station and is derived from said candidate list of base station entries;
said mobile station controller further maintaining a neighbor list of base station entries, wherein each entry in said neighbor list corresponds to a base station in a predetermined proximity of said mobile station;a pilot signal measurement circuit for measuring signal strength of each said pilot signal transmitted by each of said base stations in said neighbor list; a comparison circuit for comparing said base station signal strength measurements of each of said neighbor list entries to a first predetermined level; wherein said mobile station controller removes a particular entry from said neighbor list having said base station signal strength measurement greater than said first predetermined level and places said particular entry in a pre-candidate list maintained within said mobile station, said entries in said pre-candidate list corresponding to a set of base stations from which are derived said candidate list of base station entries. - View Dependent Claims (17, 18, 19, 20, 21)
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22. In a code division multiple access (CDMA) spread spectrum cellular communication system in which a mobile user communicates through a mobile station with other users via at least one base station included in an active list of one or more base station entries, wherein each of a plurality of base stations within said system transmit a pilot PN code signal of a unique phase, each of said PN code signals including a predefined sequence of PN chips, a mobile station searcher apparatus for identifying ones of said base stations from which received signal strength is sufficient to establish communication with said mobile station, said apparatus comprising:
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a mobile station controller for maintaining a candidate list of base station entries, wherein each entry in said candidate list corresponds to a base station capable of providing sufficient signal strength to establish communication with said mobile station wherein said active list of one or more base station entries is stored within said mobile station and is derived from said candidate list of base station entries said mobile station controller further maintaining a neighbor list of base station entries, wherein each entry in said candidate list corresponds to a base station in a predetermined proximity of said mobile station; a pilot signal measurement circuit for measuring at said mobile station signal strength of each said pilot PN code signal transmitted by each of said base stations in said neighbor list; a comparison circuit for comparing at said mobile station said base station signal strength measurements of each of said neighbor list entries to a first predetermined level; wherein said mobile station controller for removes a particular entry from said neighbor list having said base station signal strength measurement greater than said first predetermined level and places said particular entry in a pre-candidate list maintained within said mobile station, said entries in said pre-candidate list corresponding to a set of base stations from which are derived said candidate list of base station entries. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. In a cellular communication system in which a mobile user communicates through a mobile station with other users via at least one base station included in an active list of one or more base station entries, wherein each of a plurality of base stations within said system transmit a unique pilot signal, a method for identifying ones of said base stations from which received signal strength is sufficient to establish communication with said mobile station, said method comprising the steps of:
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maintaining in said mobile station a candidate list of base station entries, wherein each entry in said candidate list corresponds to a base station capable of providing sufficient signal strength to establish communication with said mobile station wherein said active list of one or more base station entries is maintained within said mobile station and is derived from said candidate list of base station entries; maintaining in said mobile station a neighbor list of base station entries, wherein each entry in said neighbor list corresponds to a base station in a predetermined proximity of said mobile station; measuring at said mobile station signal strength of each said pilot signal transmitted by each of said base stations in said neighbor list; comparing at said mobile station said base station signal strength measurements of each of said neighbor list entries to a first predetermined level; and placing a particular entry from said neighbor list having said base station signal strength measurement greater than said first predetermined level in a pre-candidate list maintained in said mobile station, wherein said entries in said pre-candidate list correspond to a set of base stations from which are derived said candidate list of base station entries. - View Dependent Claims (33, 34, 35, 36)
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Specification