Rev2 Networks

RiskView® MSO case study

Rev2 recently worked with a leading Multi System Operator (MSO) to roll out RiskView, our outage risk analysis framework and visualization engine. In addition to correlating the usual network tickets and calls into the call center, we agreed to include data from a sophisticated modem‐polling engine.

RiskView instantly determined that a large number of system‐wide CMs were reporting errors related to a single metric: Microreflections. In fact, this one metric accounted for nearly 45% of all CM events.

Microreflections generally indicate an impedance mismatch. So seeing them systemically suggested that there likely was a significant issue with terminations. Interestingly, as we looked for correlations between these issues and subscriber complaints, we saw many examples.

We correlated subscriber calls at the node:street level with microreflection issues and found chronic failures that were affecting subs. The issue wasn’t just theory – it was actually affecting performance. This wouldn’t have mattered much if the MSO were running QPSK, but with 16 or 64 QAM (as was the case here) the effect was substantial.

The only problem was that there were potentially too many targets to go after. Fortunately, systemic issues have systemic fixes. A deeper RiskView analysis showed that few microreflection events were near the threshold of 45 dBc. A normal, Gaussian distribution of failures would have put most errors close to 45 dBc and then tapered down. We saw the expected curve, but with a massive spike up between 86 and 100 dBc.

In fact, 80% of the microreflection events were in this range. Why the discontinuity?

We have a theory: adaptive pre‐equalization. Starting with DOCSIS 1.1, the modems can actually compensate for termination issues … to a point. It seems as if the modems are doing their job by managing termination issues, up to 86 dBc. If this is true, the noise at 86 dBc overwhelms their ability and the spike emerges. Further testing is needed to validate this, but if correct it points to a potential solution: modem upgrades.

Why? DOCSIS 2 and later have a greater ability to compensate. It’s possible that by encouraging modem upgrades we can improve performance and drive down costs (subscriber calls, etc.).

It’s certainly cheaper than trying to fix termination issues due to, for example, cheap splitters that subscribers have installed! RiskView correlation, isolation, and analysis can help lead to lower costs and increased performance.

For more information, please contact Rev2 at inforev2com.

Copyright © 2011, Rev2. All rights reserved. The RiskView® application is a registered trademark of Rev2. The Rev2 Managing Risks That Matter™ logo design and the Risk Concentration Analysis™ (RCA) methodology are trademarks of Rev2. All other trademarks in this document are the properties of their respective owners.