Abstract: A method and apparatus is disclosed for enabling synchronous capture of forward and return signals at a remote PHY device for detecting CPD. The remote PHY device provides the forward signal to and receives the return signal from a coaxial cable plant. The return signal contains an actual CPD signal generated by an interaction between the forward signal and a CPD source in the cable plant. The forward signal propagates from the remote PHY device to the CPD source and the actual CPD signal propagates from the CPD source to the remote PHY device all within a round-trip interval.

Abstract: A method of detecting CPD in an HFC network that includes a remote PHY device (RPD) is disclosed. The RPD includes a transmitter, receiver, and diplexer having forward and return legs. The receiver receives a return signal from a cable plant via the return leg. The transmitter provides a forward signal to the cable plant via the forward leg. A portion of the forward signal leaks through the return leg and travels to the receiver. The return signal contains a CPD signal generated by the forward signal and a CPD source in the cable plant. The forward signal propagates from RPD to CPD source and CPD signal propagates from CPD source to RPD within a round-trip interval. The method comprises: (a) adjusting the capturing bandwidth of the receiver to include return and leaked forward signals; (b) operating receiver to capture return and leaked forward signals over a limited duration of at least the round-trip interval; and (c) detecting CPD signal by processing captured leaked forward and return signals.

Abstract: A method of detecting CPD in an HFC network is disclosed, where the network includes a return receiver, a cable plant, and a node. The node includes an optical receiver, optical transmitter, a diplexer having forward and return legs, a forward path defined between optical receiver and forward leg, and a return path defined between the optical transmitter and return leg. The optical receiver provides a forward signal to the cable plant and a portion of the forward signal leaks through the return leg and travels to the return receiver. The cable plant contains a CPD source which generates a CPD signal from the forward signal. The CPD signal travels to the return receiver.

Abstract: A method of detecting CPD in an HFC network is disclosed, where the network includes a return receiver, a cable plant, and a node. The node includes an optical receiver, optical transmitter, a diplexer having forward and return legs, a forward path defined between optical receiver and forward leg, and a return path defined between the optical transmitter and return leg. The optical receiver provides a forward signal to the cable plant and a portion of the forward signal leaks through the return leg and travels to the return receiver. The cable plant contains a CPD source which generates a CPD signal from the forward signal. The CPD signal travels to the return receiver.

Abstract: A method and apparatus is disclosed for enabling synchronous capture of forward and return signals at a remote PHY device for detecting CPD. The remote PHY device provides the forward signal to and receives the return signal from a coaxial cable plant. The return signal contains an actual CPD signal generated by an interaction between the forward signal and a CPD source in the cable plant. The forward signal propagates from the remote PHY device to the CPD source and the actual CPD signal propagates from the CPD source to the remote PHY device all within a round-trip interval.

Abstract: A method of detecting CPD in an HFC network that includes a remote PHY device (RPD) is disclosed. The RPD includes a transmitter, receiver, and diplexer having forward and return legs. The receiver receives a return signal from a cable plant via the return leg. The transmitter provides a forward signal to the cable plant via the forward leg. A portion of the forward signal leaks through the return leg and travels to the receiver. The return signal contains a CPD signal generated by the forward signal and a CPD source in the cable plant. The forward signal propagates from RPD to CPD source and CPD signal propagates from CPD source to RPD within a round-trip interval. The method comprises: (a) adjusting the capturing bandwidth of the receiver to include return and leaked forward signals; (b) operating receiver to capture return and leaked forward signals over a limited duration of at least the round-trip interval; and (c) detecting CPD signal by processing captured leaked forward and return signals.

Abstract: Synchronous capture of a forward signal and a related CPD signal at a remote PHY device (RPD) for detecting and locating CPD is disclosed. The RPD delivers the forward signal to a coaxial cable plant. The forward signal propagates from the RPD to a CPD source and the CPD signal propagates from the source to the RPD within a round-trip interval. The steps include: (a) capturing the forward signal from the RPD during the round-trip interval; (b) generating a reference signal, substantially simulating the CPD signal, from the forward signal; (c) supplying the reference signal to the RPD; (d) receiving the reference signal in the RPD via a return channel; and (e) capturing the CPD signal at the RPD in the return channel during the round-trip interval. Reference and actual CPD signals are processed as a combined return signal for detecting CPD.

Abstract: Synchronous capture of a forward signal and a related CPD signal at a remote PHY device (RPD) for detecting and locating CPD is disclosed. The RPD delivers the forward signal to a coaxial cable plant. The forward signal propagates from the RPD to a CPD source and the CPD signal propagates from the source to the RPD within a round-trip interval. The steps include: (a) capturing the forward signal from the RPD during the round-trip interval; (b) generating a reference signal, substantially simulating the CPD signal, from the forward signal; (c) supplying the reference signal to the RPD; (d) receiving the reference signal in the RPD via a return channel; and (e) capturing the CPD signal at the RPD in the return channel during the round-trip interval. Reference and actual CPD signals are processed as a combined return signal for detecting CPD.

Abstract: Detecting PIM in a downstream signal, wherein the downstream signal is received from a cable plant via a subscriber network and an upstream signal is transmitted to the cable plant via the subscriber network. The upstream signal is transmitted in bursts during active intervals. PIM arises from an interaction between the upstream signal and a nonlinear component in the subscriber network and occurs in bursts corresponding to the upstream signal. The detection steps are: (a) identifying the potentially affected downstream signal from the upstream signal; (b) receiving the downstream signal during an active interval; (c) measuring a metric of the downstream signal to obtain an active value; (d) receiving the downstream signal during a quiet interval; (e) measuring the metric of the downstream signal to obtain a quiet value; (f) comparing active and quiet values; and (g) determining whether PIM distortion has been detected based on the comparison.

Abstract: Detecting PIM in a downstream signal, wherein the downstream signal is received from a cable plant via a subscriber network and an upstream signal is transmitted to the cable plant via the subscriber network. The upstream signal is transmitted in bursts during active intervals. PIM arises from an interaction between the upstream signal and a nonlinear component in the subscriber network and occurs in bursts corresponding to the upstream signal. The detection steps are: (a) identifying the potentially affected downstream signal from the upstream signal; (b) receiving the downstream signal during an active interval; (c) measuring a metric of the downstream signal to obtain an active value; (d) receiving the downstream signal during a quiet interval; (e) measuring the metric of the downstream signal to obtain a quiet value; (f) comparing active and quiet values; and (g) determining whether PIM distortion has been detected based on the comparison.

Abstract: A test equipment module and method of communicating maintenance data in a cable system is disclosed. The module comprises a receiver, a measurement system, a pilot generator, and a signal encoder. The receiver receives downstream signals from a host communication network. The measurement system determines a maintenance parameter value associated with the downstream signals. The pilot generator generates a pilot within the downstream frequency band, and a signal encoder encodes the pilot with the maintenance parameter value. The pilot generator adds the encoded pilot to the downstream signals in the communication network, such that a cable modem in the network can receive the encoded pilot and generate a spectrum that includes the encoded pilot. A PNM server receives the spectrum from the cable modem and determines the maintenance parameter value from the spectrum.

Abstract: A test equipment module and method of communicating maintenance data in a cable system is disclosed. The module comprises a receiver, a measurement system, a pilot generator, and a signal encoder. The receiver receives downstream signals from a host communication network. The measurement system determines a maintenance parameter value associated with the downstream signals. The pilot generator generates a pilot within the downstream frequency band, and a signal encoder encodes the pilot with the maintenance parameter value. The pilot generator adds the encoded pilot to the downstream signals in the communication network, such that a cable modem in the network can receive the encoded pilot and generate a spectrum that includes the encoded pilot. A PNM server receives the spectrum from the cable modem and determines the maintenance parameter value from the spectrum.

Abstract: A TDR for locating impairments in an HFC network is claimed. The network carries burst signals in an upstream band during burst intervals. The TDR comprises a transmitter, receiver, level detector, controller, accumulator, and probe detector. The transmitter transmits probe signals to the impairment, causing a reflection of the probe signals. Each probe signal is in the upstream band and has a bandwidth extending the width of the upstream band. The receiver receives the reflected probe signals during receiving intervals, and receives the burst signals during receiving intervals that overlap burst intervals. The level detector measures a level of the signals received during each receiving interval. The controller determines which of the receiving intervals are free of burst signals, based on the level measurement. The accumulator accumulates reflected probe signals received during intervals free of burst signals.

Abstract: The invention involves using Doppler shift to locate a leak of a signal from an HFC network. The leaked signal includes a component having a nominal frequency. The invention comprises: (a) moving along a drive route in the area of the network; (b) recording a speed at a number of drive-route points along the drive route; (c) at each point, receiving the component at a received frequency; (d) for each point, measuring the received frequency; (e) for each point, determining a measured Doppler shift from a difference between the received and nominal frequencies; (f) estimating a zero Doppler shift and a zero Doppler shift point based on the measured Doppler shifts; and (g) estimating the leak location based on the estimated zero Doppler shift point.

Abstract: Detection of OFDM signals leaking from an HFC network with CCAP architecture is presented. Leak detection includes creating signatures of the OFDM signals and using them in an adaptive coherent cross-correlation processing method. The signature is created at a server and then transmitted to a field leakage detector via a wireless network. The server constructs signatures based on modulation and other parameters of the OFDM signal. The detector adaptively selects valid signatures depending on the location of the detector. A cross-correlation receiver samples the OFDM leakage signal in synchronism with a GPS clock and an OFDM master clock at a CMTS. Capture of the OFDM leakage signal in the detector is synchronized with the symbol rate and timestamp of the OFMD signal to achieve time delay measurements of the leak signal at different locations of the detector. Then, the leak is located using known TDOA or network database methods.

Abstract: Detecting a leak of an OFDM signal from an HFC network, where the HFC network extends over a network area. The OFDM signal includes a first continuous pilot subcarrier having a first harmonic. The first harmonic is defined by a pre-determined first frequency. The method or apparatus comprises the steps of or means for: (a) moving a leakage detector through the network area; (b) tuning the leakage detector to receive the first harmonic of the OFDM signal, based on the pre-determined first frequency of the first harmonic; (c) with the leakage detector, receiving over-the-air, at a received first frequency, the first harmonic of the OFDM signal leaked from the HFC network; and (d) with the leakage detector, detecting the first harmonic received in step (c), whereby the leak of the OFDM signal is detected based on the detection of the first harmonic.

Abstract: A apparatus or method for detecting CPD in an HFC network, comprising: (a) acquiring digital RF downstream signals from a CMTS or CM; (b) emulating even and odd order IM distortion products from the downstream signals; (c) acquiring RF upstream signals from the CMTS during a quiet period; (d) cross-correlating the RF upstream signals with the emulated even and odd order IM products to produce even and odd order cross-correlation functions, respectively; (e) accumulating, separately, a multiplicity of even and odd order cross-correlation functions; (f) calculating even and odd order cross-correlation envelopes from the accumulated even and odd order cross-correlation functions, respectively; and (g) detecting a CPD source from either or both of the even and odd order cross-correlation envelopes by the presence of a peak in either or both of the envelopes.

Abstract: The invention involves using Doppler shift to locate a leak of a signal from an HFC network. The leaked signal includes a component having a nominal frequency. The invention comprises: (a) moving along a drive route in the area of the network; (b) recording a speed at a number of drive-route points along the drive route; (c) at each point, receiving the component at a received frequency; (d) for each point, measuring the received frequency; (e) for each point, determining a measured Doppler shift from a difference between the received and nominal frequencies; (f) estimating a zero Doppler shift and a zero Doppler shift point based on the measured Doppler shifts; and (g) estimating the leak location based on the estimated zero Doppler shift point.

Abstract: A method of detecting a digital leakage signal originating from a leak in a coaxial cable portion of an HFC network. The network has a transmission end from which a digital signal is transmitted to the coaxial cable portion. The digital signal is emitted into free space from the leak to produce the leakage signal. The method comprises: (a) producing a first set of samples representing the digital signal; (b) transmitting the first set of samples to a leakage detector; (c) moving the leakage detector to a detection point in the vicinity of the network; (d) receiving the leakage signal from the leak; (e) sampling the leakage signal to produce a second set of samples; and (f) performing a cross-correlation of the first set of samples with the second set of samples, to produce a cross-correlation function having a peak, whereby the leakage signal is detected from the peak.

Abstract: A method of detecting a digital leakage signal originating from a leak in a coaxial cable portion of an HFC network. The network has a transmission end from which a digital signal is transmitted to the coaxial cable portion. The digital signal is emitted into free space from the leak to produce the leakage signal. The method comprises: (a) producing a first set of samples representing the digital signal; (b) transmitting the first set of samples to a leakage detector; (c) moving the leakage detector to a detection point in the vicinity of the network; (d) receiving the leakage signal from the leak; (e) sampling the leakage signal to produce a second set of samples; and (f) performing a cross-correlation of the first set of samples with the second set of samples, to produce a cross-correlation function having a peak, whereby the leakage signal is detected from the peak.