Cable Plant Anomaly Detection with PNDA

Cable modems can deliver domestic broadband internet with speeds over 100Mbps, but poor signal quality can degrade performance significantly. The latest cable modems can now quantify signal interference, allowing the network operator to transmit a modified waveform that counteracts the interference.

We developed an application on PNDA which modelled the signal quality provided by cable modems, highlighting problem areas and with the potential to predict future service outages so they can be fixed before they occur.

The system used OpenDaylight to collect pre-equalization coefficients from a cable plant via the CMTS:


System architecture


Cisco has contributed an OpenDaylight plugin that forwards events from OpenDaylight to Kafka, with the AVRO encoding required by PNDA. You can get the plugin from Cisco DevNet.

A Spark application was written for PNDA which analysed the micro-reflection and frequency response of the pre-equalization coefficients to determine anomalies.


Visualising anomalies in Tableau


The output of the application can then be queried by a client application and trigger a policy change to ODL to mitigate the issue and rendered on an operator UI to show where the anomalies are and to aid in resolving any underlying problems.


Similar approaches can be applied to other media, including DSL and optical links.

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