Non-intrusive cable connection monitoring for use in HFC networks
First Claim
1. A method for individually monitoring the connectivity status of a plurality cables, each cable connected at a respective port on a cable modem termination system (CMTS) having switching interfaces between primary and secondary routers, the cables conducting upstream and downstream RF communication signals on parallel paths having a nominal system impedance, whereby the monitoring is self-contained within the CMTS, comprising the steps:
- a) producing a sinusoidal reference signal having a frequency outside the frequency range of the RF communication signals;
b) injecting the reference signal onto the parallel RF communication signal paths;
c) individually detecting on each path, the power level of the reference signal, whereby the power level correlates with an expected cable load impedance and the detecting occurs within the CMTS boundary;
d) producing a DC control voltage for each path based on the detected power level of the reference signal on each path;
e) determining the connectivity statuses of the connected cables based on the DC voltages of step d); and
f) generating a cable status indicator for each RF port cable.
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Accused Products
Abstract
A method and an apparatus are employed for individually monitoring the connectivity status of cables connected at a cable modem termination system (CMTS), where the cables conduct upstream and downstream RF communication signals. The monitoring is self-contained within the CMTS. The monitoring is achieved by producing a reference signal having a frequency outside the frequency range of the RF communication signals. The reference signal is injected onto the RF communication signal. The power level of the reference signal is detected within the CMTS, whereby the power level correlates with an expected cable load impedance. A DC control voltage based on the detected power level of the reference signal is generated, which allows a controller to determine the connectivity statuses of the connected cables.
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Citations
13 Claims
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1. A method for individually monitoring the connectivity status of a plurality cables, each cable connected at a respective port on a cable modem termination system (CMTS) having switching interfaces between primary and secondary routers, the cables conducting upstream and downstream RF communication signals on parallel paths having a nominal system impedance, whereby the monitoring is self-contained within the CMTS, comprising the steps:
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a) producing a sinusoidal reference signal having a frequency outside the frequency range of the RF communication signals;
b) injecting the reference signal onto the parallel RF communication signal paths;
c) individually detecting on each path, the power level of the reference signal, whereby the power level correlates with an expected cable load impedance and the detecting occurs within the CMTS boundary;
d) producing a DC control voltage for each path based on the detected power level of the reference signal on each path;
e) determining the connectivity statuses of the connected cables based on the DC voltages of step d); and
f) generating a cable status indicator for each RF port cable. - View Dependent Claims (2, 3, 4, 5)
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6. A method for individually monitoring the connectivity status of a plurality cables, each cable connected at a respective port on a cable modem termination system (CMTS) having switching interfaces between primary and secondary routers, the cables conducting upstream and downstream RF communication signals on parallel paths having a nominal system impedance, comprising the steps:
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a) producing a sinusoidal reference signal having a frequency outside the frequency range of the RF communication signals;
b) injecting the reference signal onto the parallel RF communication signal paths;
c) individually detecting on each path, the reference signal power level whereby the detecting occurs within CMTS boundary;
d) comparing the power level of the detected reference signal to the power level of the injected reference signal to produce a resultant difference value;
e) determining the connectivity status of the connected cables based on the difference value of step d); and
f) generating a cable status indicator for each RF port cable.
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7. An apparatus having a plurality of parallel cable connectivity monitoring circuits, for detecting the status of a plurality cables, each cable at a cable modem termination system (CMTS) having switching interfaces between primary and secondary routers, the cables conducting upstream and downstream RF communication signals on parallel paths having a nominal system impedance, each parallel circuit comprising:
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an RF backplane for carrying the communication signals and a reference signal with a frequency outside the frequency range of the communication signals;
at least one RF port for connecting at least one cable to a monitored RF signal path of the CMTS;
a sinusoidal signal generator coupled to the RF backplane for producing the reference signal for injection onto a monitored RF signal path;
a power detector coupled to the RF backplane for detecting the injected reference signal power level within the CMTS boundary, and for sending a cable connectivity status indicator signal to the RF backplane based on the detected reference signal power level; and
a controller for monitoring the reference signal and the status indicator signals and controlling switching of primary and secondary routers of the CMTS accordingly. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A non-intrusive cable connection monitoring apparatus having a plurality of parallel detection circuits for detecting the status of a plurality cables, each cable connected at a respective port on a cable modem termination system (CMTS), the CMTS used for switching interface between primary and secondary routers, where the routers send RF communication signals delivered to a hybrid fiber coaxial (HFC) cable network connected to the CMTS, and the CMTS conducts both upstream and downstream communication signals on parallel paths having a nominal system impedance, each parallel circuit comprising:
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an RF backplane for carrying the communication signals and a reference signal with a frequency outside the frequency range of the communication signals;
a plurality of HFC ports for connecting at least one cable between the HFC network and the CMTS via the RF backplane;
a plurality of router ports for connecting at least one cable between the primary and secondary routers via the RF backplane;
a sinusoidal signal generator coupled to the RF backplane for producing the reference signal for injection onto a monitored RF signal path;
a power detector coupled to the RF backplane for detecting the injected reference signal power level within the CMTS boundary, and for sending a first connectivity status indicator signal pertaining to downstream communication cable to the RF backplane based on the detected reference signal power level;
a transmitter modem with an impedance greater than the nominal system impedance for converting the reference signal and injecting the converted reference signal onto the signal path;
a receiver modem with an impedance greater than the nominal system impedance coupled to the communication path for detecting the converted reference signal and sending a second connectivity status indicator signal pertaining to upstream communication signals; and
a controller for monitoring the reference signal and the status indicator signals and controlling switching of primary and secondary routers of the CMTS accordingly.
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Specification