Method and apparatus for performing search acquisition in a CDMA communications system
First Claim
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1. In a direct sequence spread spectrum receiver, a method for for processing a received signal, comprising the steps of;
- calculating a first set of signal correlation energy values for said received signal despread according to a first set of PN sequences;
comparing said first set of signal correlation energy values against a first threshold value;
selecting a second set of PN sequences in accordance with said first set of signal correlation energy values;
calculating a second set of signal correlation energy values for said received signal despread according to said second set of PN sequences, wherein said second set of PN sequences is a subset of said first set of PN sequences; and
selecting a synchronized PN sequence from said second set of PN sequences in accordance with said second set of signal correlation energy values; and
demodulating said received signal in accordance with said selected synchronized PN sequence.
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Abstract
A novel an improved method of acquisition in a spread spectrum communication system is presented. In the present invention, a large window of PN chip offset hypotheses are searched and if an energy signal is found that might indicate the presence of the pilot signal having one of the chip offsets of the large search window, then a search of a subset of offset hypotheses, or small window, is searched.
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27 Claims
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1. In a direct sequence spread spectrum receiver, a method for for processing a received signal, comprising the steps of;
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calculating a first set of signal correlation energy values for said received signal despread according to a first set of PN sequences; comparing said first set of signal correlation energy values against a first threshold value; selecting a second set of PN sequences in accordance with said first set of signal correlation energy values; calculating a second set of signal correlation energy values for said received signal despread according to said second set of PN sequences, wherein said second set of PN sequences is a subset of said first set of PN sequences; and selecting a synchronized PN sequence from said second set of PN sequences in accordance with said second set of signal correlation energy values; and demodulating said received signal in accordance with said selected synchronized PN sequence. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An apparatus for selecting a synchronized demodulation sequence comprising:
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sequence generator means for receiving a first control signal for providing a plurality of demodulation sequences in response to said first control signal; demodulator means for receiving a received signal and demodulating a received signal in accordance with said plurality of demodulation sequences to provide a plurality of despread signals; correlator means for receiving said plurality of despread signals and calculating signal correlation energy values for said plurality of despread signals; searcher controller means for receiving said signal correlation energy values and for providing said first control signal and for providing a second control signal in accordance with said signal correlation energy values; and wherein said sequence generator means is further for receiving said second control signal and for providing a second plurality of demodulation sequences in response to said second control signal and wherein said second plurality of demodulation sequences are a subset of said first plurality of demodulation sequences. - View Dependent Claims (18, 19, 20, 21, 22)
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23. A system for selecting a synchronized demodulation sequence comprising:
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a sequence generator having an input for receiving a first control signal and having an output; a demodulator having an input coupled to said sequence generator output and having an output; an energy calculator having an input coupled to said demodulator output and having an output; and a searcher controller having an input coupled to said energy calculator output. - View Dependent Claims (24, 25, 26, 27)
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Specification