Multiplex communications – Diagnostic testing – Using oam cells
Patent
1996-07-31
1998-08-04
Patel, Ajit
Multiplex communications
Diagnostic testing
Using oam cells
370487, 455 31, H04J 116
Patent
active
057905231
ABSTRACT:
A test system for evaluating the operating state of a headend of a broadband communications network for communicating telephony signals between a telephony system and subscribers of communications services. Modulators at the headend transmit telephony signals in the forward band of the broadband communications network. The forward telephony channels are demodulated and demultiplexed by a plurality of subscriber terminals into individual telephony signals directed to an addressed subscriber. Signals returning from subscribers are digitized into standard telephony signals onto the reverse band of the broadband communications network, and demodulated by demodulators of the headend into a standard telephony signal that is interfaced to the telephony network. The test system evaluates the operating state of a selected demodulator of the headend by modulating a carrier with a predetermined data pattern to generate a upstream test signal. The upstream test signal is transmitted to the selected demodulator, which responds by outputting a detected upstream test signal. The test system compares the detected upstream test signal to the data pattern to generate error measurements that support an evaluation of the operating state of the selected demodulator. For an ingress test, the upstream signals present on the selected upstream channel are combined with the upstream test signal, and this signal combination is analyzed to determine the status of the selected upstream channel and the selected demodulator. The test system evaluates the operating state of a selected modulator of the headend in response to receiving a downstream test signal generated by the selected modulator. The test system outputs a detected downstream test signal in response to the downstream test signal. In turn, the test system conducts error measurements in response to the detected downstream test signal that support an evaluation of the operating state of the selected modulator.
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Dubberly Gregory T.
Idler Steve
Ritchie, Jr. John A.
Barnhardt III Hubert J.
Gardner Kelly A.
Massaroni Kenneth M.
Patel Ajit
Scientific-Atlanta, Inc.
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