CDMA system having time-distributed transmission paths for multipath reception
First Claim
1. In a communications system providing wireless communications services to a plurality of subscriber stations in an urban serving area, the communications system comprising at least one base station outputting a spread spectrum signal generated in response to a subscriber information signal and an assigned code sequence having a predetermined chip interval, and a plurality of antennas spatially distributed around said urban serving area, a method for providing spread spectrum-processed information signals to said urban serving area comprising the steps of:
- supplying the subscriber information signal to the at least one base station;
supplying a synchronization signal to said at least one base station, said synchronization signal corresponding to a system clock;
providing to said antennas corresponding spread spectrum signals from said at least one base station, each of said spread spectrum signals received by said corresponding antenna having a corresponding transmission delay relative to the other spread spectrum signals, said corresponding transmission delay being greater than said chip interval and less than a search interval of said subscriber stations; and
transmitting the spread spectrum signals from the respective antennas into the urban serving area to form overlapping coverage regions that minimize shadowing effects.
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Accused Products
Abstract
An arrangement (apparatus and method) for providing a code division multiple access (CDMA) transmission system in an urban environment using spatially-diverse antennas and time-diversity devices and techniques to provide improved cell coverage without the detrimental effects of multipath (Rayleigh) fading. The spatially-diverse antennas output identical CDMA-modulated signals to a serving area at different times, whereby each CDMA-modulated signal output from a corresponding antenna has a sufficent delay to avoid mutual interference with the identical CDMA-modulated signals output from other antennas. The delay assigned to each antenna is within a range greater than a chip interval, and less than or equal to a base station sequence offset between base stations. As a result, a subscriber station is able to separately demodulate the received CDMA-modulated signals from the different antennas as CDMA signals having adequate multipath delay for demodulation using a rake receiver. The delays may be implemented as delay devices supplying delayed system clock signals from a GPS receiver to corresponding base stations having identical spreading sequences. Alternatively, the delays may be implemented as successively delaying a CDMA-modulated signal output by a single base station before transmission to the antennas along corresponding transmission paths.
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Citations
51 Claims
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1. In a communications system providing wireless communications services to a plurality of subscriber stations in an urban serving area, the communications system comprising at least one base station outputting a spread spectrum signal generated in response to a subscriber information signal and an assigned code sequence having a predetermined chip interval, and a plurality of antennas spatially distributed around said urban serving area, a method for providing spread spectrum-processed information signals to said urban serving area comprising the steps of:
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supplying the subscriber information signal to the at least one base station; supplying a synchronization signal to said at least one base station, said synchronization signal corresponding to a system clock; providing to said antennas corresponding spread spectrum signals from said at least one base station, each of said spread spectrum signals received by said corresponding antenna having a corresponding transmission delay relative to the other spread spectrum signals, said corresponding transmission delay being greater than said chip interval and less than a search interval of said subscriber stations; and transmitting the spread spectrum signals from the respective antennas into the urban serving area to form overlapping coverage regions that minimize shadowing effects. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. In a communications system providing wireless communications services to a plurality of subscriber stations in an urban serving area, the communications system comprising a plurality of base stations and a plurality of antennas spatially distributed around said urban serving area and coupled to a corresponding one of said base stations, a method for providing spread spectrum-processed information signals to said urban serving area comprising the steps of:
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assigning identical code sequences to each of said base stations, said assigned code sequences comprising a sequence of codes having a predetermined chip interval; supplying the subscriber information signal to the base stations; successively supplying a synchronization signal to said base stations at corresponding delay intervals greater than said chip interval and less than a search interval of said subscriber stations. - View Dependent Claims (19, 20, 21, 22)
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23. In a communications system providing wireless communications services to a plurality of subscriber stations in an urban serving area, the communications system comprising at least one base station and a plurality of antennas spatially distributed around said urban serving area, a method for providing spread spectrum-processed information signals to said urban serving area comprising the steps of:
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outputting a spread spectrum-processed information signal from said at least one base station; successively supplying said spread spectrum-processed information signal to said antennas at corresponding delay intervals greater than said chip interval and less than a search interval of said subscriber stations; and transmitting the successively delayed spread spectrum-processed information signals from the respective antennas into the urban serving area to form overlapping coverage regions that minimize shadowing effects. - View Dependent Claims (24, 25, 26, 27)
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28. A communications system providing code division multiple access (CDMA) wireless services to a plurality of subscriber stations in an urban serving area, comprising:
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a system clock source; at least one base station outputting CDMA modulated information on a forward channel; a plurality of antennas transmitting said CDMA modulated information distributed around said urban serving areas to minimize shadowing effects; and means for supplying said CDMA modulated information to said antennas at successive delay intervals sufficient to minimize multipath fading between the transmitted CDMA modulated information; wherein said system comprises a plurality of said base stations performing CDMA processing using identical code sequences, said supplying means comprising a series of delay devices receiving said system clock from said system clock source, each of said delay devices outputting a delayed system clock to a corresponding one of said base stations at a unique synchronization delay interval. - View Dependent Claims (29)
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30. A communications system providing code division multiple access (CDMA) wireless services to a plurality of subscriber stations in an urban serving area, comprising:
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a system clock source; at least one base station outputting CDMA modulated information on a forward channel; a plurality of antennas transmitting said CDMA modulated information distributed around said urban serving areas to minimize shadowing effects; and means for supplying said CDMA modulated information to said antennas at successive delay intervals sufficient to minimize multipath fading between the transmitted CDMA modulated information; wherein said supplying means comprises a series of delay devices receiving said CDMA modulated information from said at least one base station, each of said delay devices outputting delayed CDMA modulated information to a corresponding one of said antennas at a unique synchronization delay interval. - View Dependent Claims (31)
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32. A communications system providing code division multiple access (CDMA) wireless services to a plurality of subscriber stations in an urban serving area, comprising:
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a system clock source; at least one base station outputting CDMA modulated information on a forward channel; a plurality of antennas transmitting said CDMA modulated information distributed around said urban serving areas to minimize shadowing effects; and means for supplying said CDMA modulated information to said antennas at successive delay intervals sufficient to minimize multipath fading between the transmitted CDMA modulated information, wherein each of said delay intervals is within a range greater than one microsecond and less than forty microseconds; and wherein each of said delay intervals is substantially equal to ten microseconds.
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33. In a communications system providing wireless communications services to a plurality of subscriber stations in an urban serving area, the communications system comprising at least one base station outputting a spread spectrum signal generated in response to a subscriber information signal and an assigned code sequence having a predetermined chip interval, and a plurality of antennas spatially distributed around said urban serving area, a method for providing spread spectrum-processed information signals to said urban serving area comprising the steps of:
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supplying the subscriber information signal to the at least one base station; supplying a synchronization signal to said at least one base station, said synchronization signal corresponding to a system clock; providing to said antennas corresponding spread spectrum signals from said at least one base station, each of said spread spectrum signals received by said corresponding antenna having a corresponding transmission delay relative to the other spread spectrum signals, said corresponding transmission delay being greater than said chip interval and less than a base station sequence offset of said at least one base station; and transmitting the spread spectrum signals from the respective antennas into the urban serving area to form overlapping coverage regions that minimize shadowing effects. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42)
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43. In a communications system providing wireless communications services to a plurality of subscriber stations in an urban serving area, the communications system comprising a plurality of base stations and a plurality of antennas spatially distributed around said urban serving area and coupled to a corresponding one of said base stations, a method for providing spread spectrum-processed information signals to said urban serving area comprising the steps of:
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assigning identical code sequences to each of said base stations, said assigned code sequences comprising a sequence of codes having a a predetermined chip interval; supplying the subscriber information signal to the base stations; successively supplying a synchronization signal to said base stations at corresponding delay intervals greater than said chip interval and less than a base station sequence offset of said base stations. - View Dependent Claims (44, 45)
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46. The method of claim further comprising:
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successively outputting identical pilot code sequences at said corresponding delay intervals from the respective base stations; and transmitting the output pilot code sequences at the corresponding delay intervals.
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47. In a communications system providing wireless communications services to a plurality of subscriber stations in an urban serving area, the communications system comprising at least one base station and a plurality of antennas spatially distributed around said urban serving area, a method for providing spread spectrum-processed information signals to said urban serving area comprising the steps of:
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outputting a spread spectrum-processed information signal from said at least one base station; successively supplying said spread spectrum-processed information signal to said antennas at corresponding delay intervals greater than said chip interval and less than a base station sequence offset of said at least one base station; and transmitting the spread spectrum signals from the respective antennas into the urban serving area to form overlapping coverage regions that minimize shadowing effects. - View Dependent Claims (48, 49, 50, 51)
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Specification