Patent US6567480B1 successfully refreshed from Google Patents.
US6567480B1
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Method and apparatus for sampling timing adjustment and frequency offset compensation
Assignee: Nokia of America Corp
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Filing: 1999-08-10
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Granted: 2003-05-20
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Expires: 2019-08-10
Abstract
Abstract A simplified method for sampling timing adjustment and frequency offset estimation in a TDMA cellular PCS environment using π/4 - shifted DQPSK comprises the steps of oversampling a received signal resulting from transmission of sequences of complex-valued symbols at a rate N times the symbol rate thereof so as to produce N sets of samples, comparing for each set of samples the differential phase angle between successively received complex-valued symbols, and determining which set of the N sets of samples has differential phase angles closest to ideal values to thereby obtain an optimal sampling timing. The differential phase angles are measured by multiplying a complex conjugate of a received complex-valued symbol and a succeeding symbol to produce a comparison vector having an angle equal to the differential phase angle between the received complex-valued symbol and the succeeding symbol. The differential phase angles are optionally rotated so that the angle thereof is between 0° and 90°. Frequency offset is estimated by determining a constant deviation of the differential phase angles from an ideal differential phase angle value for a plurality of successive comparison vectors by correlating the rotated comparison vectors against a bank of unit vectors to determine a maximum correlation.
Inventors
- 👤 Nima Brardjanian
- 👤 Yong J. Lee
- 👤 Alex Matusevich
- 👤 Mohsen Sarraf
- 👤 Sheng-Jen Tsai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 16:36
CPC Classifications
H; H04; H04L; H04L7/00; H04L7/0054; H04L27/00; H04L27/18; H04L27/22; H04L27/227; H04L27/2275; H04L27/0014; H04L2027/0024; H04L2027/0026; H04L2027/003; H04L2027/0036; H04L2027/0044; H04L2027/0046; H04L2027/0063; H04L2027/0065; H04L7/0066
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
123 words
A radio receiver comprising: receiver means for receiving input signals resulting from transmission of sequences of complex-valued symbols; sampling means for oversampling a received input signal at a rate N times the symbol rate thereof so as to produce N sets of samples; comparison means for comparing successively received, sampled complex-valued symbols to determine a differential phase angle therebetween; sampling timing adjustment means for determining an optimum sampling time as corresponding to the sampling timing of one set of the N sets of samples having differential phase angles closest to ideal value; and frequency offset estimating means for determining a constant deviation of the differential phase angles from an ideal phase angle value and estimating a frequency offset based upon the constant deviation.
Claim 2
Dependent Claim
123 words
A radio receiver comprising: receiver means for receiving input signals resulting from transmission of sequences of complex-valued symbols; sampling means for oversampling a received input signal at a rate N times the symbol rate thereof so as to produce N sets of samples; comparison means for comparing successively received, sampled complex-valued symbols to determine a differential phase angle therebetween; sampling timing adjustment means for determining an optimum sampling time as corresponding to the sampling timing of one set of the N sets of samples having differential phase angles closest to ideal value; and frequency offset estimating means for determining a constant deviation of the differential phase angles from an ideal phase angle value and estimating a frequency offset based upon the constant deviation.
Claim 3
Dependent Claim
51 words
A radio receiver according to claim 1 ; wherein the comparison means comprises multiplying means for multiplying a complex conjugate of a received complex-valued symbol and a succeeding symbol to output a comparison vector having an angle equal to the phase angle between the received complex-valued symbol and the succeeding symbol.
Claim 4
Dependent Claim
32 words
A radio receiver according to claim 2 ; wherein the comparison means further comprises phase rotating means for rotating the comparison vector so that the angle thereof is between 0° and 90°.
Claim 5
Dependent Claim
44 words
A radio receiver according to claim 3 ; wherein the frequency offset estimating means includes means for determining a constant deviation of the phase angle from an ideal phase angle value by calculating an average phase angle for a plurality of successive comparison vectors.
Claim 6
Dependent Claim
38 words
A radio receiver according to claim 1 ; further comprising frequency offset correction means for correcting for a frequency offset between the receiver means and a carrier frequency of an input signal based upon the estimated frequency offset.
Claim 7
Dependent Claim
54 words
A radio receiver according to claim 5 ; wherein the receiver means comprises an analog receiver having a fixed-frequency local oscillator, and the frequency offset correction means includes means for correcting for a frequency offset between the fixed-frequency local oscillator and a carrier frequency of an input signal based upon the estimated frequency offset.
Claim 8
Dependent Claim
18 words
A radio receiver according to claim 1 ; wherein the input signals are symbols modulated by π/4-shifted DQPSK.
Claim 9
Independent Claim
131 words
A method for receiving a signal comprising the steps of: oversampling a received signal resulting from transmission of sequences of complex-valued symbols at a rate N times the symbol rate thereof so as to produce N sets of samples; comparing for each set of samples a phase angle of successively received complex-valued symbols to determine a differential phase angle between successive symbols; determining which set of the N sets of samples has differential phase angles closest to ideal values to thereby obtain an optimal sampling timing; determining the value of a constant deviation of the differential phase angles of the set of N sets of samples having the differential phase angles closest to ideal values from an ideal phase angle value; and estimating a frequency offset based upon the constant deviation.
Claim 10
Independent Claim
131 words
A method for receiving a signal comprising the steps of: oversampling a received signal resulting from transmission of sequences of complex-valued symbols at a rate N times the symbol rate thereof so as to produce N sets of samples; comparing for each set of samples a phase angle of successively received complex-valued symbols to determine a differential phase angle between successive symbols; determining which set of the N sets of samples has differential phase angles closest to ideal values to thereby obtain an optimal sampling timing; determining the value of a constant deviation of the differential phase angles of the set of N sets of samples having the differential phase angles closest to ideal values from an ideal phase angle value; and estimating a frequency offset based upon the constant deviation.
Claim 11
Dependent Claim
38 words
A method for receiving a signal according to claim 8 ; further comprising the step of correcting for a frequency offset between a receiver and a carrier frequency of an input signal based upon an estimated frequency offset.
Claim 12
Dependent Claim
51 words
A method for receiving a signal according to claim 9 ; wherein the step of correcting for a frequency offset includes the step of correcting for a frequency offset between the local oscillator of a receiver and a carrier frequency of a signal received thereby based upon the estimated frequency offset.
Claim 13
Dependent Claim
59 words
A method for receiving a signal according to claim 8 ; wherein the step of comparing successively received symbols comprises the step of multiplying a complex conjugate of a received complex-valued symbol and a succeeding symbol to produce a comparison vector having an angle equal to the differential phase angle between the received complex-valued symbol and the succeeding symbol.
Claim 14
Dependent Claim
38 words
A method for receiving a signal according to claim 11 ; wherein the step of comparing successively received symbols further comprises the step of rotating the comparison vector so that the angle thereof is between 0° and 90°.
Claim 15
Dependent Claim
84 words
A method for receiving a signal according to claim 12 ; wherein the step of determining which set of the N sets of samples has differential phase angles closest to ideal values to thereby obtain an optimal sampling timing comprises the steps of determining a deviation of the differential phase angles from an ideal phase angle value by correlating the differential phase angles with a set of predetermined phase angles and determining which set of samples has the greatest correlation with ideal phase angles.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2006-05-19 | 2006-11-18 | 2007-05-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2010-05-19 | 2010-11-18 | 2011-05-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2014-05-19 | 2014-11-18 | 2015-05-20 | $7700.00 | Window Closed / Lapsed |