US 9,960,842 B2Granted

Network traffic-compatible time domain reflectometer

AssigneeArcom Digital, LLC

InventorVictor M. Zinevich

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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. The probe detector detects the impairment from the accumulated probe signals and estimates a time delay for the impairment. A distance to the impairment is estimated from the time delay.

Claims29

Dependent claims

A time domain reflectometer for locating an impairment in a coaxial cable portion of a hybrid fiber-coax (HFC) network, the coaxial cable portion being characterized by a velocity of propagation and carrying a plurality of burst signals in an upstream frequency band during a plurality of burst intervals, respectively, said time domain reflectometer comprising:

(a) a transmitter, to be coupled to the HFC network at a distance from the impairment, for transmitting over the distance to the impairment a plurality of low-level probe signals in the upstream frequency band during a plurality of receiving intervals, respectively, the impairment causing a reflection of the plurality of probe signals in the form of a plurality of reflected probe signals, which travel back over the distance towards said transmitter;
(b) a receiver, to be coupled to the HFC network, for receiving the plurality of reflected probe signals during the plurality of receiving intervals, respectively, and for receiving the plurality of burst signals during a number of the plurality of receiving intervals that overlap in time with the plurality of burst intervals;
(c) a level detector, coupled to said receiver, for measuring a level of the signal or signals received by said receiver during each of the receiving intervals, such that a plurality of level measurements are made for the plurality of receiving intervals, respectively;
(d) a controller, coupled to said level detector, for determining which of the plurality of receiving intervals are substantially free of the burst signals based on the plurality of level measurements;
(e) an accumulator, coupled to said receiver and to said controller, for accumulating substantially only the reflected probe signals received during the receiving intervals that have been determined to be substantially free of the burst signals;
and
(f) an impairment detector, coupled to said accumulator, for detecting the impairment from the accumulated reflected probe signals and estimating from the detection a time delay between the transmission of the probe signals by said transmitter and the reception of the reflected probe signals by said receiver,
whereby a value of the distance to the impairment is estimated from the time delay and the velocity of propagation of the coaxial cable portion of the HFC network.

5 more elements

A method of locating an impairment in a coaxial cable portion of a hybrid fiber-coax (HFC) network, the coaxial cable portion being characterized by a velocity of propagation and carrying a plurality of burst signals in an upstream frequency band during a plurality of burst intervals, respectively, said method comprising the steps of:

(a) transmitting in the coaxial cable portion of the HFC network, over a distance to the impairment, a plurality of low-level probe signals in the upstream frequency band during a plurality of receiving intervals, respectively, the impairment causing a reflection of the plurality of probe signals in the form of a plurality of reflected probe signals, which travel back over the distance;
(b) receiving the plurality of reflected probe signals during the plurality of receiving intervals, respectively, and receiving the plurality of burst signals during a number of the plurality of receiving intervals that overlap in time with the plurality of burst intervals;
(c) measuring a level of the signal or signals received in step (b) during each of the receiving intervals, such that a plurality of level measurements are made for the plurality of receiving intervals, respectively;
(d) determining which of the plurality of receiving intervals are substantially free of the burst signals based on the plurality of level measurements;
(e) accumulating substantially only the reflected probe signals received during the receiving intervals that have been determined to be substantially free of the burst signals;
(f) detecting the impairment from the accumulated reflected probe signals and estimating from the detection a time delay between the transmission of the probe signals in step (a) and the reception of the reflected probe signals in step (b);
and
(g) estimating a value of the distance to the impairment from the time delay and the velocity of propagation of the coaxial cable portion of the HFC network.

5 more elements

(a) generating a plurality of low-level probe pulses, each with a bandwidth that extends substantially over the entire upstream frequency band and that is substantially limited to the upstream frequency band;
(b) transmitting in the coaxial cable portion of the HFC network, over a distance to the impairment, the plurality of low-level probe pulses during a plurality of receiving intervals, respectively, the impairment causing a reflection of the plurality of probe pulses in the form of a plurality of reflected probe pulses, which travel back over the distance;
(c) receiving the plurality of reflected probe pulses during the plurality of receiving intervals, respectively, and receiving the plurality of burst signals during a number of the receiving intervals that overlap in time with the plurality of burst intervals;
(d) measuring a signal level of what is received in step (c) during each of the receiving intervals, such that a plurality of signal level measurements is made for the plurality of receiving intervals, respectively;
(e) determining which of the plurality of receiving intervals are substantially free of the burst signals based on the plurality of signal level measurements;
(f) accumulating substantially only the reflected probe pulses received during the receiving intervals that have been determined to be substantially free of the burst signals;
(g) detecting the impairment by processing the accumulated reflected probe pulses in a matched filter that is configured for the probe pulses;
(h) estimating, from the detection in step (g), a time delay between the transmission of the plurality of probe pulses and the reception of the plurality of reflected probe pulses, respectively;
and
(i) estimating a value of the distance to the impairment from the time delay and the velocity of propagation of the coaxial cable portion of the HFC network.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/283,510Filed 3 Oct 2016 · us provisional application
Priority: 12 Oct 2015
Published: US 2017/0104522 A113 Apr 2017
Granted: 1 May 2018
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

H04B 10/071
Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems: using a reflected signal,…
H04B 10/0771
Using a supervisory or additional signal: fault location on the transmission path
H04B 10/0793
Using measurements of the data signal: network aspects, e.g. central monitoring of transmission parameters
H04B 10/25751
Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier: optical arrangements for CATV or video distribution