US5742591A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interference cancellation system for CATV return transmissions
Assignee: GERNERAL INSTRUMENT Corp
•
Filing: 1995-06-07
•
Granted: 1998-04-21
•
Expires: 2015-06-07
Abstract
Abstract A CATV interference cancellation system reduces the presence of undesirable narrowband interference that corrupts return signal transmissions. The cancellation system first acquires a reference signal that contains components related to the interference present in the return signal. The reference signal is processed to derive estimates of the interference components appearing in the return signal and a cancellation signal is generated. The interference cancellation signal is then combined with the return signal, thereby reducing the interference components present in it. The interference cancellation system is deployed at a CATV headend and time division multiple access techniques (TDMA) are used for return transmission. The reference signal is derived from monitoring time slots within a TDMA frame that contain predetermined transmission data. Preferably the predetermined data is the absence of data resulting in an idle time slot. These time slots may be temporarily idle, or may deliberately be left unused to provide a window to a "noise-only" component of the return path signal. The signal thus obtained is passed through the same RF processing stage as the composite return signal and subsequently sampled and digitized. Thereafter, spectrum estimation techniques are applied to the samples of the signal to determine the frequencies of the interfering signals. Once an estimate of the interference frequencies is obtained from the spectrum, the reference signal comprising the same frequencies may be synthesized.
Inventors
- 👤 Nageen Himayat
- 👤 Charles A. Eldering
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 17:17
CPC Classifications
H; H04; H04N; H04N7/00; H04N7/10; H04N7/102; H04N7/16; H04N7/173; H04N7/17309
Claims Analysis
Total Claims: 68
Claim 1
Independent Claim
97 words
A method of canceling interference in a CATV return path signal that includes a time division multiple access data stream having a plurality of time slots within which frames of data are transmitted from subscriber units comprising the step: acquiring an interference reference signal from the CATV return path; selecting at least one time slot for use in evaluating interference; sampling said selected time slot when predetermined data is transmitted therein; processing said interference reference signal to produce an interference cancellation signal; and combining said interference cancellation signal with said CATV return path signal to cancel interference.
Claim 2
Independent Claim
97 words
A method of canceling interference in a CATV return path signal that includes a time division multiple access data stream having a plurality of time slots within which frames of data are transmitted from subscriber units comprising the step: acquiring an interference reference signal from the CATV return path; selecting at least one time slot for use in evaluating interference; sampling said selected time slot when predetermined data is transmitted therein; processing said interference reference signal to produce an interference cancellation signal; and combining said interference cancellation signal with said CATV return path signal to cancel interference.
Claim 3
Dependent Claim
32 words
The method of claim 1 wherein said predetermined data is the absence of data such that the selected time slot is idle, and said sampling is performed on said idle time slot.
Claim 4
Dependent Claim
76 words
The method of claim 2 wherein the step of processing said interference reference signal comprises: computing a discrete Fourier transform of the data resulting from said sampling of said idle time slot in each frame; applying a phase correction factor to said discrete Fourier transforms of the data; averaging said phase corrected discrete Fourier transforms; estimating the frequencies of the interferers based on said averaged transforms; and generating an interference cancellation signal of said estimated frequencies.
Claim 5
Dependent Claim
30 words
The method of claim 3 wherein said processing of said interference reference signal further includes utilizing a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 6
Dependent Claim
46 words
The method of claim 4 wherein the processing of said interference reference signal further comprises: using a finite impulse response filter to process said interference reference signal when related linearly with said return path signal; and training said finite impulse response filter with said feedback signal.
Claim 7
Dependent Claim
23 words
The method of claim 5 wherein the step of training said finite impulse response filter uses an adaptive least mean squares method algorithm.
Claim 8
Dependent Claim
24 words
The method of claim 5 wherein the step of training said finite impulse response filter uses a square root sum of the squares algorithm.
Claim 9
Dependent Claim
46 words
The method of claim 4 wherein the processing of said interference reference signal further comprises: using an infinite impulse response filter to process said interference reference signal when related linearly with said return path signal; and training said infinite impulse response filter with said feedback signal.
Claim 10
Dependent Claim
48 words
The method of claim 4 wherein the processing of said interference reference signal further comprises: using a feedforward neural network to process said interference reference signal when related nonlinearly with said return path signal; and training said neural network with said feedback signal using a back propagation algorithm.
Claim 11
Dependent Claim
46 words
The method of claim 2 wherein the processing of said interference cancellation signal further comprises: using a radial basis function network to process said interference reference signal when related nonlinearly with said return path signal; and training said radial basis function network with said feedback signal.
Claim 12
Dependent Claim
15 words
The method of claim 2 wherein the step of sampling idle time slots is periodic.
Claim 13
Dependent Claim
15 words
The method of claim 2 wherein the step of sampling idle time slots is aperiodic.
Claim 14
Dependent Claim
34 words
The method of claim 2 wherein the step of sampling idle time slots is periodic with a higher sampling rate and reference signal generation is accomplished through reconstruction procedures suitable for non-uniform sampling schemes.
Claim 15
Dependent Claim
23 words
The method of claim 1 wherein the step of acquiring said interference reference signal is performed at a headend of a CATV system.
Claim 16
Dependent Claim
34 words
The method of claim 1 wherein the step of acquiring said interference reference signal is performed at a location remote from a CATV system headend and the method is also performed at said headend.
Claim 17
Independent Claim
80 words
A method of canceling interference in a CATV return path signal comprising the steps: acquiring an interference reference signal; processing said interference reference signal using a finite impulse response filter when related linearly with said return path signal to produce an interference cancellation signal; combining said interference cancellation signal with said CATV return path signal to cancel interference; and training said finite impulse response filter with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 18
Independent Claim
80 words
A method of canceling interference in a CATV return path signal comprising the steps: acquiring an interference reference signal; processing said interference reference signal using a finite impulse response filter when related linearly with said return path signal to produce an interference cancellation signal; combining said interference cancellation signal with said CATV return path signal to cancel interference; and training said finite impulse response filter with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 19
Dependent Claim
17 words
The method of claim 16 wherein the interference reference signal is acquired from the CATV return path.
Claim 20
Dependent Claim
20 words
The method of claim 16 wherein the steps of acquiring said interference reference signal is by means of an antenna.
Claim 21
Dependent Claim
23 words
The method of claim 16 wherein the step of acquiring said interference reference signal is performed at a headend of a CATV system.
Claim 22
Dependent Claim
34 words
The method of claim 16 wherein the step of acquiring said interference reference signal is performed at a location remote from a CATV system headend and the method is also performed at said headend.
Claim 23
Independent Claim
80 words
A method of canceling interference in a CATV return path signal comprising the steps: acquiring an interference reference signal; processing said interference reference signal using an infinite impulse response filter when related linearly with said return path signal to produce an interference cancellation signal; combining said interference cancellation signal with said CATV return path signal to cancel interference; and training said infinite impulse response filter with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 24
Independent Claim
80 words
A method of canceling interference in a CATV return path signal comprising the steps: acquiring an interference reference signal; processing said interference reference signal using an infinite impulse response filter when related linearly with said return path signal to produce an interference cancellation signal; combining said interference cancellation signal with said CATV return path signal to cancel interference; and training said infinite impulse response filter with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 25
Independent Claim
82 words
A method of canceling interference in a CATV return path signal comprising the steps: acquiring an interference reference signal; processing said interference reference signal using a feedforward neural network when related nonlinearly with said return path signal to produce an interference cancellation signal; combining said interference cancellation signal with said CATV return path signal to cancel interference; and training said neural network with a feedback signal acquired downstream of said combined cancellation signal and return path signal using a back propagation algorithm.
Claim 26
Independent Claim
82 words
A method of canceling interference in a CATV return path signal comprising the steps: acquiring an interference reference signal; processing said interference reference signal using a feedforward neural network when related nonlinearly with said return path signal to produce an interference cancellation signal; combining said interference cancellation signal with said CATV return path signal to cancel interference; and training said neural network with a feedback signal acquired downstream of said combined cancellation signal and return path signal using a back propagation algorithm.
Claim 27
Independent Claim
80 words
A method of canceling interference in a CATV return path signal comprising the steps: acquiring an interference reference signal; processing said interference reference signal using a radial basis function network when related nonlinearly with said return path signal to produce an interference cancellation signal; combining said interference cancellation signal with said CATV return path signal to cancel interference; and training said radial basis function network with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 28
Independent Claim
80 words
A method of canceling interference in a CATV return path signal comprising the steps: acquiring an interference reference signal; processing said interference reference signal using a radial basis function network when related nonlinearly with said return path signal to produce an interference cancellation signal; combining said interference cancellation signal with said CATV return path signal to cancel interference; and training said radial basis function network with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 29
Dependent Claim
98 words
An interference cancellation system for a CATV return path signal having a time division multiple access data stream having a plurality of time slots within which frames of data are transmitted from subscriber units comprising: means for acquiring an interference reference signal; means for selecting at least one time slot for use in evaluating interference; means for sampling said selected time slot when predetermined data is transmitted therein; means for processing said interference reference signal to produce an interference cancellation signal; and means for combining said interference cancellation signal with said CATV return path signal to cancel interference.
Claim 30
Dependent Claim
98 words
An interference cancellation system for a CATV return path signal having a time division multiple access data stream having a plurality of time slots within which frames of data are transmitted from subscriber units comprising: means for acquiring an interference reference signal; means for selecting at least one time slot for use in evaluating interference; means for sampling said selected time slot when predetermined data is transmitted therein; means for processing said interference reference signal to produce an interference cancellation signal; and means for combining said interference cancellation signal with said CATV return path signal to cancel interference.
Claim 31
Dependent Claim
32 words
The system of claim 24 wherein said predetermined data is the absence of data such that the selected time slot is idle, and said sampling is performed on said idle time slot.
Claim 32
Dependent Claim
86 words
The system of claim 25 wherein said means for processing said interference reference signal comprises: means for computing a discrete Fourier transform of the data resulting from said sampling of said idle time slot in each frame; means for applying a phase correction factor to said discrete Fourier transforms of the data; means for averaging said phase corrected discrete Fourier transforms; means for estimating the frequencies of the interferers based on said averaged transforms; and means for generating an interference cancellation signal of said estimated frequencies.
Claim 33
Dependent Claim
31 words
The system of claim 26 wherein said means for processing said interference reference signal further includes utilizing a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 34
Dependent Claim
49 words
The system of claim 27 wherein said means for processing said interference reference signal further comprises: a finite impulse response filter to process said interference reference signal when related linearly with said return path signal; and means for training said finite impulse response FIR filter with said feedback signal.
Claim 35
Dependent Claim
23 words
The system of claim 28 wherein said means for training said finite impulse response filter uses an adaptive least mean squares method algorithm.
Claim 36
Dependent Claim
24 words
The system of claim 28 wherein said means for training said finite impulse response filter uses a square root sum of the squares algorithm.
Claim 37
Dependent Claim
48 words
The system of claim 27 wherein said means for processing said interference reference signal further comprises: an infinite impulse response filter to process said interference reference signal when related linearly with said return path signal; and means for training said infinite impulse response filter with said feedback signal.
Claim 38
Dependent Claim
50 words
The system of claim 27 wherein said means for processing said interference reference signal further comprises: a feedforward neural network to process said interference reference signal when related nonlinearly with said return path signal; and means for training said neural network with said feedback signal using a back propagation algorithm.
Claim 39
Dependent Claim
48 words
The system of claim 25 wherein said means for processing said interference cancellation signal further comprises: a radial basis function network to process said interference reference signal when related nonlinearly with said return path signal; and means for training said radial basis function network with said feedback signal.
Claim 40
Dependent Claim
15 words
The system of claim 25 wherein said means for sampling idle time slots is periodic.
Claim 41
Dependent Claim
15 words
The system of claim 25 wherein said means for sampling idle time slots is aperiodic.
Claim 42
Dependent Claim
34 words
The system of claim 25 wherein said means for sampling idle time slots is periodic with a higher sampling rate and reference signal generation is accomplished through reconstruction procedures suitable for non-uniform sampling schemes.
Claim 43
Dependent Claim
23 words
The system of claim 24 wherein said means for acquiring said interference reference signal is performed at a headend of a CATV system.
Claim 44
Dependent Claim
34 words
The system of claim 24 wherein said means for acquiring said interference reference signal is performed at a location remote from a CATV system headend and the method is also performed at said headend.
Claim 45
Dependent Claim
102 words
A CATV return path interference cancellation system comprising: means for acquiring an interference reference signal by means of an antenna; means for processing said interference reference signal to produce an interference cancellation signal; means for combining said interference cancellation signal with said CATV return path signal to cancel interference; means for acquiring a second interference reference signal from said combined cancellation signal and return path signal; means for processing said second interference reference signal to produce a second interference cancellation signal; and means for combining said second interference cancellation signal with said combined cancellation signal and return path signal to cancel interference.
Claim 46
Dependent Claim
102 words
A CATV return path interference cancellation system comprising: means for acquiring an interference reference signal by means of an antenna; means for processing said interference reference signal to produce an interference cancellation signal; means for combining said interference cancellation signal with said CATV return path signal to cancel interference; means for acquiring a second interference reference signal from said combined cancellation signal and return path signal; means for processing said second interference reference signal to produce a second interference cancellation signal; and means for combining said second interference cancellation signal with said combined cancellation signal and return path signal to cancel interference.
Claim 47
Dependent Claim
71 words
The system of claim 39 wherein the CATV return path includes a time division multiple access data stream having a plurality of time slots within which frames of data are transmitted from subscriber units and the means for acquiring a second reference signal includes: means for selecting at least one time slot for use in evaluating interference; and means for sampling said selected time slot when predetermined date is transmitted therein.
Claim 48
Dependent Claim
23 words
The system of claim 39 wherein said means for acquiring said interference reference signal is performed at a headend of a CATV system.
Claim 49
Dependent Claim
23 words
The system of claim 39 wherein said means for acquiring said interference reference signal is performed at a headend of a CATV system.
Claim 50
Dependent Claim
34 words
The system of claim 39 wherein said means for acquiring said interference reference signal is performed at a location remote from a CATV system headend and the method is also performed at said headend.
Claim 51
Dependent Claim
82 words
A CATV return path interference cancellation system comprising: means for acquiring an interference reference signal; means for processing said interference reference signal using a finite impulse response filter when related linearly with said return path signal to produce an interference cancellation signal; means for combining said interference cancellation signal with said CATV return path signal to cancel interference; and means for training said finite impulse response filter with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 52
Dependent Claim
82 words
A CATV return path interference cancellation system comprising: means for acquiring an interference reference signal; means for processing said interference reference signal using a finite impulse response filter when related linearly with said return path signal to produce an interference cancellation signal; means for combining said interference cancellation signal with said CATV return path signal to cancel interference; and means for training said finite impulse response filter with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 53
Dependent Claim
17 words
The system of claim 44 wherein the interference reference signal is acquired from the CATV return path.
Claim 54
Dependent Claim
20 words
The system of claim 44 wherein said means for acquiring said interference reference signal is by means of an antenna.
Claim 55
Dependent Claim
23 words
The system of claim 44 wherein said means for acquiring said interference reference signal is performed at a headend of a CATV system.
Claim 56
Dependent Claim
34 words
The system of claim 44 wherein said means for acquiring said interference reference signal is performed at a location remote from a CATV system headend and the method is also performed at said headend.
Claim 57
Dependent Claim
82 words
A CATV return path interference cancellation system comprising: means for acquiring an interference reference signal; means for processing said interference reference signal using an infinite impulse response filter when related linearly with said return path signal to produce an inteference cancellation signal; means for combining said interference cancellation signal with said CATV return path signal to cancel interference; and means for training said infinite impulse response filter with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 58
Dependent Claim
82 words
A CATV return path interference cancellation system comprising: means for acquiring an interference reference signal; means for processing said interference reference signal using an infinite impulse response filter when related linearly with said return path signal to produce an inteference cancellation signal; means for combining said interference cancellation signal with said CATV return path signal to cancel interference; and means for training said infinite impulse response filter with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 59
Dependent Claim
84 words
A CATV return path interference cancellation system comprising: means for acquiring an interference reference signal; means for processing said interference reference signal using a feedforward neural network when related nonlinearly with said return path signal to produce an interference cancellation signal; means for combining said interference cancellation signal with said CATV return path signal to cancel interference; and means for training said neural network with a feedback signal acquired downstream of said combined cancellation signal and return path signal using a back propagation algorithm.
Claim 60
Dependent Claim
84 words
A CATV return path interference cancellation system comprising: means for acquiring an interference reference signal; means for processing said interference reference signal using a feedforward neural network when related nonlinearly with said return path signal to produce an interference cancellation signal; means for combining said interference cancellation signal with said CATV return path signal to cancel interference; and means for training said neural network with a feedback signal acquired downstream of said combined cancellation signal and return path signal using a back propagation algorithm.
Claim 61
Dependent Claim
82 words
A CATV return path interference cancellation system comprising: means for acquiring an interference reference signal; means for processing said interference reference signal using a radial basis function network when related nonlinearly with said return path signal to produce an interference cancellation signal; means for combining said interference cancellation signal with said CATV return path signal to cancel interference; and means for training said radial basis function network with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 62
Dependent Claim
82 words
A CATV return path interference cancellation system comprising: means for acquiring an interference reference signal; means for processing said interference reference signal using a radial basis function network when related nonlinearly with said return path signal to produce an interference cancellation signal; means for combining said interference cancellation signal with said CATV return path signal to cancel interference; and means for training said radial basis function network with a feedback signal acquired downstream of said combined cancellation signal and return path signal.
Claim 63
Independent Claim
96 words
A method of canceling interference in a CATV return path signal comprising the steps: acquiring an interference reference signal by means of an antenna; processing said interference reference signal to produce an interference cancellation signal; combining said interference cancellation signal with said CATV return path signal to cancel interference; acquiring a second interference reference signal from said combined cancellation signal and return path signal; processing said second interference reference signal to produce a second interference cancellation signal; and combining said second interference cancellation signal with said combined cancellation signal and return path signal to cancel interference.
Claim 64
Independent Claim
96 words
A method of canceling interference in a CATV return path signal comprising the steps: acquiring an interference reference signal by means of an antenna; processing said interference reference signal to produce an interference cancellation signal; combining said interference cancellation signal with said CATV return path signal to cancel interference; acquiring a second interference reference signal from said combined cancellation signal and return path signal; processing said second interference reference signal to produce a second interference cancellation signal; and combining said second interference cancellation signal with said combined cancellation signal and return path signal to cancel interference.
Claim 65
Dependent Claim
66 words
The method of claim 52 wherein the CATV return path includes a time division multiple access data stream having a plurality of time slots within which frames of data are transmitted from subscriber units and the step of acquiring a second reference signal includes: selecting at least one time slot for use in evaluating interference; sampling said selected time slot when predetermined date is transmitted therein.
Claim 66
Dependent Claim
23 words
The method of claim 52 wherein the step of acquiring said interference reference signal is performed at a headend of a CATV system.
Claim 67
Dependent Claim
23 words
The method of claim 52 wherein the step of acquiring said interference reference signal is performed at a headend of a CATV system.
Claim 68
Dependent Claim
34 words
The method of claim 52 wherein the step of acquiring said interference reference signal is performed at a location remote from a CATV system headend and the method is also performed at said headend.
References Cited (Backward Citations)
US4689628A
Cited
US5049890A
Cited
US4439770A
Cited
US4435618A
Cited
US4408615A
Cited
US4412341A
Cited
US4435841A
Cited
US4549183A
Cited
US4472814A
Cited
US4472815A
Cited
US4475214A
Cited
US4633315A
Cited
US4608569A
Cited
US4612549A
Cited
US4660042A
Cited
US4701935A
Cited
US4812851A
Cited
US4736455A
Cited
US4893350A
Cited
US4748667A
Cited
US5115454A
Cited
US4996488A
Cited
US5046133A
Cited
WO1989010663A1
Cited
US4991165A
Cited
US5109533A
Cited
US5260707A
Cited
US5117505A
Cited
US5125108A
Cited
WO1991015064A1
Cited
US5225902A
Cited
US5199048A
Cited
US5133017A
Cited
US5208837A
Cited
US5140699A
Cited
US5319636A
Cited
US5148117A
Cited
US5383224A
Cited
US5349609A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-04-20 | 2001-10-20 | 2002-04-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-04-20 | 2005-10-20 | 2006-04-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-04-20 | 2009-10-20 | 2010-04-21 | $7700.00 | Window Closed / Lapsed |