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HFC Network

Managing Network Quality and Capacity With Proactive Network Maintenance

Jason Rupe
Principal Architect

Aug 28, 2020

You probably know that Proactive Network Maintenance (PNM) is about finding and fixing problems before they impact the customer to ensure highly reliable and available cable broadband services. But the other side of PNM is about managing the capacity or bandwidth available in the network. PNM may have started with the former concept in mind, but the latter is becoming more important as we rely on higher amounts of capacity at the edge. As the world adjusts to life during the COVID-19 pandemic, access network capacity is becoming even more critical. PNM is an important toolset for network capacity management, and CableLabs is helping operators manage network quality and capacity together.

Network condition impacts network capacity. Network impairments, a broad class of failures and flaws in the ability of a network to carry data, have to be addressed before they lead to service failure. The DOCSIS® protocol is a method for sending data over multiple radio frequencies in hybrid fiber-coax networks, and comes with several resiliency mechanisms, like profile management, that help service continue in spite of impairments, to a point. These impairments in the cable plant may impact a few or all frequencies. Impairments that impact specific frequencies may or may not be able to be compensated for, on those frequencies. If severe, the impairment may impact the data carried on those frequencies entirely, leading to correctable or even uncorrectable data errors. If not severe, profiles may be able to adjust to lower modulation orders to allow less data to be reliably carried than otherwise. Impairments that impact a larger amount of frequencies of course have a greater impact on the bandwidth the network can carry. In any case, impairments impact the capacity that the operator can get from the access network.

For example, consider that operators often place upstream bandwidth into lower frequencies, near where radio and electrical interference can enter the network through damaged cable or loose connectors. Upstream profiles can help make these frequencies useful when otherwise impaired; PNM can help operators find, work around, and fix ingress issues before they impact service. If the cable is damaged in multiple places (or say water gets into the cable due to wind causing it to move and get lose or damaged) then multiple frequencies can be impacted. But DOCSIS mechanisms help services be robust to these problems, and PNM can alert the operator to the problem, allowing a proactive fix.

PNM is a practical set of tools for network operators to manage network conditions, which becomes even more important as we move toward higher utilization of the access network capacity. As demand for bandwidth increases at the edge, PNM becomes an important network capacity management tool for network providers. The difference between a perfect network and one with flaws felt by customers begins to shrink. PNM begins to be an imperative; it is “table stakes” for maintaining communications services and managing the capacity of the network.

For almost all of us, we share our connection to the internet and our communication services whether fiber or coaxial cable is the final connection to the home. Over the years, DOCSIS has grown to provide much higher data rates over a shared medium, in addition to adding resiliency. Cable Modem Termination Systems (CMTSs) enable the network resources to be shared efficiently, so that we all have access to better communications through economies of scale, allowing us all to take advantage of the capacity available. Service providers can manage the network capacity with a number of methods to make sure service needs are met, PNM being one of those mechanisms.

CableLabs has been working with these issues in mind for some time. In July of 2019, I wrote on the subject of 10G and reliability, pointing out that higher bandwidth solutions closer to the customer will be required for 10G. Then, in August, I wrote on the subject of reliability from a cable perspective and pointed out that the impairments addressed through PNM impact capacity. So, we see that reliability and network capacity are closely coupled. As we move toward higher bandwidth services, expand the utilization of frequencies and further push the limits of technology, reliable and sufficient bandwidth become highly coupled. Therefore, so do the tools that network providers use to manage these service qualities. CableLabs is working on solutions to help operators succeed in this reality.

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