Method and apparatus for beacon discovery in a spread spectrum cellular radio communication system
First Claim
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1. An apparatus for discovering beacon signals communicated over a wireless forward link from transmitters to receivers in a spread spectrum radio communication system, wherein the beacon signals comprise a plurality of different code sequences having index values assigned thereto and having portions that overlap one another, the apparatus comprising:
- a radio subsystem that downconverts a received RF signal to a baseband signal and samples the baseband signal to derive baseband samples in digital form that represent at least one received beacon signal;
buffer means, operably coupled to said radio subsystem, for storing said baseband samples;
a timing signal generator for generating a reference timing signal; and
beacon discovery means, operably coupled to said buffer means and said timing signal generator, fori) correlating said baseband samples with said plurality of code sequences over an extended search window that has a length greater the characteristic length of said plurality of code sequences, and analyzing results therefrom to identify a set of correlation peaks that exceed a predetermined threshold;
ii) for each given correlation peak in the set identified in i), deriving and storing an index value assigned to a particular code sequence from which the given correlation peak is derived,iii) for each given correlation peak in the set identified in i), deriving and storing a power level metric indicative of the received signal power of the given correlation peak,iv) for each given correlation peak in the set identified in i), deriving and storing a time offset based upon said reference timing signal,v) identifying correlation peak pairs that correspond to code sequences with overlapping portions and that have time offsets that fall within a predetermined tolerance window, andvi) for each given correlation peak pair, identifying one of the correlation peaks of the given correlation peak pair that has a lower power level metric in relation to the other correlation peak of the given correlation peak pair, and discarding information pertaining to the one correlation peak from subsequent output and processing following therefrom.
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Abstract
An improved apparatus (and corresponding methodology) for discovering beacon signals in a spread spectrum radio communication system is provided, wherein the beacon signals comprise a plurality of different code sequences having index values assigned thereto and having portions that overlap one another. Correlation is performed over an extended search window. Ambiguities between correlation peaks are resolved by identifying correlation peak pairs corresponding to overlapping code sequences and having time offsets that fall within a predetermined tolerance window. Each pair is analyzed to identify the peak with a lower power level metric, and information pertaining to this lower power level peak is discarded from output and processing operations that follow therefrom.
26 Citations
18 Claims
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1. An apparatus for discovering beacon signals communicated over a wireless forward link from transmitters to receivers in a spread spectrum radio communication system, wherein the beacon signals comprise a plurality of different code sequences having index values assigned thereto and having portions that overlap one another, the apparatus comprising:
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a radio subsystem that downconverts a received RF signal to a baseband signal and samples the baseband signal to derive baseband samples in digital form that represent at least one received beacon signal; buffer means, operably coupled to said radio subsystem, for storing said baseband samples; a timing signal generator for generating a reference timing signal; and beacon discovery means, operably coupled to said buffer means and said timing signal generator, for i) correlating said baseband samples with said plurality of code sequences over an extended search window that has a length greater the characteristic length of said plurality of code sequences, and analyzing results therefrom to identify a set of correlation peaks that exceed a predetermined threshold; ii) for each given correlation peak in the set identified in i), deriving and storing an index value assigned to a particular code sequence from which the given correlation peak is derived, iii) for each given correlation peak in the set identified in i), deriving and storing a power level metric indicative of the received signal power of the given correlation peak, iv) for each given correlation peak in the set identified in i), deriving and storing a time offset based upon said reference timing signal, v) identifying correlation peak pairs that correspond to code sequences with overlapping portions and that have time offsets that fall within a predetermined tolerance window, and vi) for each given correlation peak pair, identifying one of the correlation peaks of the given correlation peak pair that has a lower power level metric in relation to the other correlation peak of the given correlation peak pair, and discarding information pertaining to the one correlation peak from subsequent output and processing following therefrom. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for discovering beacon signals communicated over a wireless forward link from transmitters to receivers in a spread spectrum radio communication system, wherein the beacon signals comprise a plurality of different code sequences having index values assigned thereto and having portions that overlap one another, the method comprising:
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downconverting a received RF signal to a baseband signal and sampling the baseband signal to derive baseband samples in digital form that represent at least one received beacon signal; storing said baseband samples; generating a reference timing signal; and discovering beacon signals by; i) correlating said baseband samples with said plurality of code sequences over an extended search window that has a length greater the characteristic length of said plurality of code sequences, and analyzing results therefrom to identify a set of correlation peaks that exceed a predetermined threshold; ii) for each given correlation peak in the set identified in i), deriving and storing an index value assigned to a particular code sequence from which the given correlation peak is derived, iii) for each given correlation peak in the set identified in i), deriving and storing a power level metric indicative of the received signal power of the given correlation peak, iv) for each given correlation peak in the set identified in i), deriving and storing a time offset based upon said reference timing signal, v) identifying correlation peak pairs that correspond to code sequences with overlapping portions and that have time offsets that fall within a predetermined tolerance window, and vi) for each given correlation peak pair, identifying one of the correlation peaks of the given correlation peak pair that has a lower power level metric in relation to the other correlation peak of the given correlation peak pair, and discards information pertaining to the one correlation peak from subsequent output and processing following therefrom. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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Specification
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Current AssigneePC-TEL Incorporated
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Original AssigneePCTEL, Inc.
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InventorsSoltanian, Amir, Peric, Mirjana
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Primary Examiner(s)Anderson; Matthew
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Assistant Examiner(s)Aminzay; Shaima Q.
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Application NumberUS11/101,340Publication NumberTime in Patent Office894 DaysField of Search370/335, 370/229, 370/252, 370/310, 370/320, 370/328, 370/338, 370/342, 370/350, 370/441, 370/468, 370/479, 375/130, 375/362, 375/141, 375/142, 342/357.12US Class Current370/335CPC Class CodesH04B 1/7075 with code phase acquisitionH04B 1/70754 Setting of search window, i...H04B 2201/70715 with application-specific f...
