Methods and system for determining a dominant impairment of an impaired communication channel
First Claim
1. A method for determining whether distortion or noise is the dominant impairment on an impaired communication channel, comprising the steps of:
- establishing a sample size (N), a test duration, and a query rate for developing a complementary cumulative density function (CCDF) statistical measure of test signal measurements on a test channel;
selecting and remotely instructing a network element to transmit test signals on the test channel;
monitoring test signals at a headend of the test channel and recording measurements of signal-to-noise ratio (SNR) and Receive Power Level (Pr) on the test channel for samples 1 to N at the established query rate for the established duration;
developing a CCDF for Receive Noise Power Level (Nr) from samples 1 to N, where Nr=Pr−
SNR for each sample;
obtaining a theoretically expected CCDF of Receive Noise Power Level for an Additive White Gaussian Noise (AWGN) dominated impairment on the test channel; and
comparing the CCDF for Receive Noise Power Level developed from samples 1 to N relative to the theoretically expected CCDF of Receive Noise Power Level for an AWGN-dominated impairment and concluding therefrom whether the dominant impairment is distortion or noise.
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Abstract
Methods are described for identifying a dominant impairment on a communication channel impaired by an interference issue. The methods include systematic examination of total power loading, systematic examination of signal power reduction, statistical examination of communication channel noise power, and systematic examination of interleaver effectiveness. Each relates to automatically diagnosing and characterizing distortion-based interference issues by monitoring the performance of a communication channel during a testing procedure. These methods enable a technician or engineer to remotely diagnose distortion-based interference issues relatively quickly without having to use external test equipment and without having to deploy technicians to various locations within the cable plant. A system by which these methods can be implemented is also disclosed.
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Citations
20 Claims
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1. A method for determining whether distortion or noise is the dominant impairment on an impaired communication channel, comprising the steps of:
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establishing a sample size (N), a test duration, and a query rate for developing a complementary cumulative density function (CCDF) statistical measure of test signal measurements on a test channel; selecting and remotely instructing a network element to transmit test signals on the test channel; monitoring test signals at a headend of the test channel and recording measurements of signal-to-noise ratio (SNR) and Receive Power Level (Pr) on the test channel for samples 1 to N at the established query rate for the established duration; developing a CCDF for Receive Noise Power Level (Nr) from samples 1 to N, where Nr=Pr−
SNR for each sample;obtaining a theoretically expected CCDF of Receive Noise Power Level for an Additive White Gaussian Noise (AWGN) dominated impairment on the test channel; and comparing the CCDF for Receive Noise Power Level developed from samples 1 to N relative to the theoretically expected CCDF of Receive Noise Power Level for an AWGN-dominated impairment and concluding therefrom whether the dominant impairment is distortion or noise. - View Dependent Claims (2, 3, 4)
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5. A method for determining a burst duration nature of a dominant impairment on an impaired communication channel, comprising the steps of:
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obtaining a minimum acceptance performance value for at least one of modulation error ratio (MERMIN), signal-to-noise ratio (SNRMIN), packet error rate (PERMIN), and bit error rate (BERMIN) for a test signal on a test channel; setting a current interleaver setting of the test channel to a lowest available setting and remotely instructing a network element to receive a test signal on the test channel; monitoring the test signal at a headend of the test channel and measuring at least one of modulation error ratio (MER), signal-to-noise ratio (SNR), packet error rate (PER), and bit error rate (BER); and comparing the measurement taken for the test signal to the corresponding minimum acceptance performance value and determining therefrom whether the current interleaver setting represents an upper bound of the dominant impairment of the test channel. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. A system for characterizing a dominant impairment on an impaired communication channel, comprising:
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a cable modem termination system (CMTS) unit configured to remotely instruct a network element to receive test signals on a forward path of a test channel; said CMTS unit having a transmitter configured to transmit the test signals from the network element and a processing unit configured to measure and record signal-to-noise ratio (SNR) measurements for said test signals and configured to make comparisons relating to said measurements; and said processing unit of said CMTS configured to automatically determine from said comparisons whether distortion or noise is the dominant impairment, and to automatically determine a burst protection setting that represents an upper bound of the dominant impairment on the test channel. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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Specification