Downstream OFDM Noise Power Ratio is a PNM Test described in [PHYv3.1] Downstream Noise Power Ratio (NPR) Measurement section. The CmtsDsOfdmNoisePwrRatioTable defines the management interface for the operator to configure and execute the Downstream OFDM Noise Power Ratio test. The purpose of downstream NPR measurement is to view the noise, interference and intermodulation products underlying a portion of the OFDM signal. As an out-of-service test, the CMTS can define an exclusion band of zero-valued subcarriers which forms a spectral notch in the downstream OFDM signal for all profiles of a given downstream channel. The CM provides its normal spectral capture measurements, or symbol capture, which permit analysis of the notch depth. A possible use case is to observe LTE interference occurring within an OFDM band; another is to observe intermodulation products resulting from signal-level alignment issues. Since the introduction and removal of a notch affects all profiles, causing possible link downtime, this feature is intended for infrequent maintenance. The CCAP creates a row in the CmtsDsOfdmNoisePwrRatioTable for each ifIndex of a downstream channel. The CCAP MAY support simultaneous Downstream NPR Measurement tests on more than one OFDM channel at a time.