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US5574750A
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Methods and apparatus for detecting a cellular digital packet data (CDPD) carrier
Assignee: Cirrus Logic Inc
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Filing: 1993-09-14
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Granted: 1996-11-12
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Expires: 2013-09-14
Abstract
Abstract Disclosed herein are methods and apparatus for detecting the presence of a CDPD carrier in a channel of a cellular system (although the invention is broadly applicable to detecting a specific kind of carrier associated with an "overlay" system, wherein an "overlay" system is one that shares the frequency allocation of another system on a non-cooperating basis). This specification describes a spectral estimation technique for detection of a CDPD carrier. In addition, this specification describes an MMSE (minimum mean-squared error) method that improves on the spectral estimation method.
Inventors
- 👤 George Peponides
- 👤 Kumar Balachandran
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 11:07
CPC Classifications
H; H04; H04W; H04W48/00; H04W48/18; G; G10; G10L; G10L25/00; G10L25/78; H04L; H04L27/00; H04L27/0012; H04L27/18
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
181 words
A method for detecting an overlay signal in a channel of a primary system, wherein said overlay signal is associated with an overlay system that shares a frequency allocation with the primary system, wherein the primary system has a plurality of channels in which the overlay signal might be present at any given time, and wherein the overlay signal is characterized by a predetermined expected value, the method comprising the steps of: (a) sampling a received signal in at least one channel to obtain a predetermined number of samples for said at least one channel; (b) computing an error value for each sample, said error value based on a difference, if any, between a sample value and said predetermined expected value; (c) determining a minimum error value; (d) determining a reference value; (e) determining a ratio of said minimum error value to said reference value; and (f) making a decision as to whether the received signal is an overlay signal on the basis of at least said ratio, wherein said decision is made by comparing said ratio to a threshold value.
Claim 2
Independent Claim
181 words
A method for detecting an overlay signal in a channel of a primary system, wherein said overlay signal is associated with an overlay system that shares a frequency allocation with the primary system, wherein the primary system has a plurality of channels in which the overlay signal might be present at any given time, and wherein the overlay signal is characterized by a predetermined expected value, the method comprising the steps of: (a) sampling a received signal in at least one channel to obtain a predetermined number of samples for said at least one channel; (b) computing an error value for each sample, said error value based on a difference, if any, between a sample value and said predetermined expected value; (c) determining a minimum error value; (d) determining a reference value; (e) determining a ratio of said minimum error value to said reference value; and (f) making a decision as to whether the received signal is an overlay signal on the basis of at least said ratio, wherein said decision is made by comparing said ratio to a threshold value.
Claim 3
Dependent Claim
16 words
A method as recited in claim 1, wherein said error values are mean-squared error (mse) values.
Claim 4
Dependent Claim
19 words
A method as recited in claim 1, wherein said overlay signal is a Cellular Digital Packet Data (CDPD) signal.
Claim 5
Dependent Claim
16 words
A method as recited in claim 3, wherein said primary system is a cellular telephone system.
Claim 6
Dependent Claim
16 words
A method as recited in claim 1, wherein said primary system is a cellular telephone system.
Claim 7
Dependent Claim
20 words
A method as recited in claim 1, wherein said reference value comprises an average of at least two error values.
Claim 8
Independent Claim
194 words
A system for detecting an overlay signal in a channel of a primary system, wherein said overlay signal is associated with an overlay system that shares a frequency allocation with the primary system, wherein the primary system has a plurality of channels in which the overlay signal might be present at any given time, and wherein the overlay signal is characterized by a predetermined expected value, the system comprising: (a) means for sampling a received signal in at least one channel to obtain a predetermined number of samples for said at least one channel; (b) means for computing an error value for each sample, said error value based on a difference, if any, between the sample value and said predetermined expected value; (c) means for determining a minimum error value; (d) means for determining an average of at least two error values; (e) means for determining a ratio of said minimum error value to said average; and (f) means for making a decision as to whether the received signal is an overlay signal on the basis of at least said ratio, wherein said decision is made by comparing said ratio to a threshold value.
Claim 9
Independent Claim
194 words
A system for detecting an overlay signal in a channel of a primary system, wherein said overlay signal is associated with an overlay system that shares a frequency allocation with the primary system, wherein the primary system has a plurality of channels in which the overlay signal might be present at any given time, and wherein the overlay signal is characterized by a predetermined expected value, the system comprising: (a) means for sampling a received signal in at least one channel to obtain a predetermined number of samples for said at least one channel; (b) means for computing an error value for each sample, said error value based on a difference, if any, between the sample value and said predetermined expected value; (c) means for determining a minimum error value; (d) means for determining an average of at least two error values; (e) means for determining a ratio of said minimum error value to said average; and (f) means for making a decision as to whether the received signal is an overlay signal on the basis of at least said ratio, wherein said decision is made by comparing said ratio to a threshold value.
Claim 10
Dependent Claim
16 words
A system as recited in claim 7, wherein said error values are mean-squared error (mse) values.
Claim 11
Dependent Claim
19 words
A system as recited in claim 7, wherein said overlay signal is a Cellular Digital Packet Data (CDPD) signal.
Claim 12
Dependent Claim
16 words
A system as recited in claim 9, wherein said primary system is a cellular telephone system.
Claim 13
Dependent Claim
16 words
A system as recited in claim 7, wherein said primary system is a cellular telephone system.
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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) | 1999-11-12 | 2000-05-13 | 2000-11-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-11-12 | 2004-05-13 | 2004-11-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-11-12 | 2008-05-13 | 2008-11-12 | $7700.00 | Window Closed / Lapsed |