Fast and reliable data carrier detection by a cable modem in a cable television plant
First Claim
1. An apparatus of detecting a data carrier in a downstream band in a cable plant, the apparatus comprising:
- (a) means for selecting a potential data carrier from within the downstream band;
(b) means for determining whether the potential data carrier contains a signal modulated according to a first modulation scheme wherein the first modulation scheme is not a default modulation scheme used on signals in the downstream band;
(c) means for determining whether the potential data carrier contains a signal that is apparently not modulated according to the first modulation scheme; and
(d) means for determining whether the potential data carrier contains a signal modulated according to a second modulation scheme wherein the second modulation scheme is the default modulation scheme used on signals in the downstream band.
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Accused Products
Abstract
Apparatus, methods, and computer program products for detecting or locating a viable data carrier in a downstream channel by a cable modem. Potential channels for data carriers can be eliminated quickly by going through a “screening” process, i.e., the first constellation diagram match, thereby preventing those potential channels from going through a significantly more time-consuming second constellation match. The determination of whether the signal in the potential channel is modulated according to the first particular modulation scheme is done rapidly and only potential channels containing a signal likely to be modulated according to the second particular modulation scheme are examined for the second determination step.
18 Citations
54 Claims
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1. An apparatus of detecting a data carrier in a downstream band in a cable plant, the apparatus comprising:
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(a) means for selecting a potential data carrier from within the downstream band; (b) means for determining whether the potential data carrier contains a signal modulated according to a first modulation scheme wherein the first modulation scheme is not a default modulation scheme used on signals in the downstream band; (c) means for determining whether the potential data carrier contains a signal that is apparently not modulated according to the first modulation scheme; and (d) means for determining whether the potential data carrier contains a signal modulated according to a second modulation scheme wherein the second modulation scheme is the default modulation scheme used on signals in the downstream band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus of locating a correct downstream channel for use by a cable modem in a cable plant, the apparatus comprising:
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(a) means for, from a plurality of unexamined downstream frequency channels, selecting an unexamined downstream frequency channel; (b) means for determining whether the unexamined downstream frequency channel does not have a first modulation-type signal and a signal-to-noise ratio higher than a first predetermined threshold signal-to-noise ratio; (c) means for determining whether the unexamined downstream frequency channel has a signal-to-noise ratio higher than the first predetermined threshold signal-to-noise ratio; (d) means for returning to step (a); (e) means for determining whether the unexamined downstream frequency channel has a second modulation-type signal and a signal-to-noise ratio less than a second threshold signal-to-noise ratio; (f) means for determining whether the unexamined downstream frequency channel has a signal-to-noise ratio less than the second threshold signal-to-noise ratio; (g) means for returning to step (a); and (h) means for repeating steps (a) to (g) until an unexamined downstream frequency channel is selected that has a second modulation-type signal and signal-to-noise ratio at least as high as the second threshold signal-to-noise ratio. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. An apparatus of detecting a data carrier in a downstream channel in a cable plant, the apparatus comprising:
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(a) means for selecting a potential data carrier; (b) means for attempting to analyze the potential data carrier for a particular modulation scheme, wherein the modulation scheme is not a default modulation scheme used on signals in the downstream band; (c) means for determining whether a signal-to-noise ratio in the potential data carrier when analyzed for the particular modulation scheme is greater than a defined threshold signal-to-noise ratio; (d) means for determining whether the signal-to-noise ratio is greater than the defined threshold signal-to-noise ratio; and (e) means for abandoning the potential data carrier from further consideration and selecting a different data carrier for further analysis. - View Dependent Claims (18, 19, 20)
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21. An apparatus of detecting a data carrier in a downstream band in a cable plant, the apparatus comprising:
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(a) means for selecting a potential data carrier from within the downstream band; (b) means for determining that the potential data carrier does not contain a signal modulated according to a first modulation scheme wherein the first modulation scheme is not a default modulation scheme used on signals in the downstream band; and (c) means for determining that the potential data carrier contains a signal modulated according to a second modulation scheme wherein the second modulation scheme is the default modulation scheme used on signals in the downstream band by concluding that the potential data carrier contains a signal that is apparently not modulated according to the first modulation scheme.
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22. A cable modem comprising:
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a CPU (central processing unit); a memory; and instructions for detecting a data carrier in a downstream band in a cable plant, the instructions comprising; (a) instructions for selecting a potential data carrier from within the downstream band; (b) instructions for determining whether the potential data carrier contains a signal modulated according to a first modulation scheme wherein the first modulation scheme is not a default modulation scheme used on signals in the downstream band; (c) instructions for determining whether the potential data carrier contains a signal that is apparently not modulated according to the first modulation scheme; and (d) instructions for determining whether the potential data carrier contains a signal modulated according to a second modulation scheme wherein the second modulation scheme is the default modulation scheme used on signals in the downstream band. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29)
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30. A cable modem comprising:
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a CPU (central processing unit); a memory; and instructions for detecting a data carrier in a downstream channel for use by a cable modem in a cable plant, the instructions comprising; (a) instructions for, from a plurality of unexamined downstream frequency channels, selecting an unexamined downstream frequency channel; (b) instructions for determining whether the unexamined downstream frequency channel does not have a first modulation-type signal and a signal-to-noise ratio higher than a first predetermined threshold signal-to-noise ratio; (c) instructions for determining whether the unexamined downstream frequency channel does have a signal-to-noise ratio higher than the first predetermined threshold signal-to-noise ratio; (d) instructions for returning to step (a); (e) instructions for determining whether the unexamined downstream frequency channel has a second modulation-type signal and a signal-to-noise ratio less than a second threshold signal-to-noise ratio; (f) instructions for determining whether the unexamined downstream frequency channel has a signal-to-noise ratio less than the second threshold signal-to-noise ratio; (g) instructions for returning to step (a); and (f) instructions for repeating steps (a) to (g) until an unexamined downstream frequency channel is selected that has a second modulation-type signal and signal-to-noise ratio at least as high as the second threshold signal-to-noise ratio. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37)
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38. A cable modem comprising:
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a CPU (central processing unit); a memory; and instructions for detecting a data carrier in a downstream channel in a cable plant, the instructions comprising; (a) instructions for selecting a potential data carrier; (b) instructions for attempting to analyze the potential data carrier for a particular modulation scheme, wherein the modulation scheme is not a default modulation scheme used on signals in the downstream band; (c) instructions for determining whether a signal-to-noise ratio in the potential data carrier when analyzed for the particular modulation scheme is greater than a defined threshold signal-to-noise ratio; (d) instructions for determining whether the signal-to-noise ratio is greater than the defined threshold signal-to-noise ratio; and (e) instructions for abandoning the potential data carrier from further consideration and selecting a different data carrier for further analysis. - View Dependent Claims (39, 40, 41)
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42. A cable modem comprising:
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a CPU (central processing unit); a memory; and instructions for detecting a data carrier in a downstream band in a cable plant, the instructions comprising; (a) instructions for selecting a potential data carrier from within the downstream band; (b) instructions for determining that the potential data carrier does not contain a signal modulated according to a first modulation scheme wherein the first modulation scheme is not a default modulation scheme used on signals in the downstream band; and (c) instructions for determining that the potential data carrier contains a signal modulated according to a second modulation scheme wherein the second modulation scheme is the default modulation scheme used on signals in the downstream band by concluding that the potential data carrier contains a signal that is apparently not modulated according to the first modulation scheme.
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43. A method for handling a plurality of modulation schemes for a downstream channel in a cable plant, comprising:
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(a) determining whether the downstream channel employs a modulation scheme that is not default for the downstream channel; and (b) if the downstream channel is found to employ the modulation scheme that is not default, moving to a second downstream channel for analysis. - View Dependent Claims (44, 45, 46, 47, 48)
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49. A system for handling a plurality of modulation schemes for a downstream channel in a cable plant, comprising:
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(a) means for determining whether the downstream channel employs a modulation scheme that is not default for the downstream channel; and (b) means for moving to a second downstream channel for analysis. - View Dependent Claims (50, 51, 52)
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53. A cable modem comprising:
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a CPU (central processing unit); a memory; and instructions for handling a plurality of modulation schemes for a downstream channel in a cable plant, the instructions comprising; (a) instructions for determining whether the downstream channel employs a modulation scheme that is not default for the downstream channel; and (b) instructions for moving to a second downstream channel for analysis. - View Dependent Claims (54)
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Specification