Swimming Upstream – How Cable Operators Are Growing Their Upstream Bandwidth
Advanced Upstream Blog Series Introduction
In the Advanced Upstream blog series we will explore how cable operators have traditionally managed upstream bandwidth capacity planning, how market dynamics and technical innovation are driving changes, and where things are likely headed in the coming years. In this entry we will lay the groundwork for discussion of the Advanced Upstream, and future installments will drill down on details of specific aspects.
How Cable Operators Increase Upstream Bandwidth
Upstream broadband demand exploded during the pandemic and is showing no signs of slowing down. Lockdown orders forced a seemingly overnight transition to work from home for parents and e-learning for students. The rapid adoption of videoconferencing and it’s nearly symmetrical broadband usage model proportionally hit the upstream much harder than the downstream, creating challenges for service providers to keep up. Global upstream consumption is up ~30-50% overall but varies even within a given country. In the US, the coasts and other specific geographical areas where there tend to be more jobs that can be performed remotely saw higher increases, while the south and central US generally saw lower increases.
Surveys have shown that even when the pandemic is in our rear view mirror there will be a significant lasting increase in remote work, and upstream usage numbers from New Zealand and Australia as they emerge are confirming this theory.
Three Main Levers To Increase Upstream Capacity
Keeping up with increasing bandwidth demand is nothing new for Cable operators, they have been masterful at planning and executing to stay ahead of the Moore’s Law curve for decades. They have traditionally relied on the same three knobs to increase upstream bandwidth.
- Mode Nodes – Reducing service group sizes via node segmentation or node splits
- More Hz – Using more upstream spectrum by adding carriers
- More Bits/Hz – Passing more data through available spectrum by increasing modulation orders
But the world is changing – these tried-and-true methods must evolve to overcome some of the challenges to their continued applicability.
- More Nodes – Hubs/Headends are simply running out of rack space and power/cooling budget to allow business-as-usual (BAU) node splits. Distributed Access Architectures (DAA) like Remote PHY are needed to enable continued node splits.
- More Hz – Much of the world is already utilizing every Hz of usable spectrum, especially in 42MHz upstream systems. Mid-split (85MHz) and High Split (204MHz) architectures are needed to create more empty upstream spectrum for expanding carrier counts.
- More Bits/Hz – 64QAM is already heavily deployed in many systems, the only way to further increase modulation orders and spectral efficiency is to implement OFDMA.
Which Approach is Best?
These three levers are seldom used in isolation – there are many synergies with combining them.
- High-Split + OFDMA – DOCSIS only specifies the use of OFDMA above 85MHz, so there is no benefit to implementing a high split without OFDMA.
- DAA + OFDMA – DAA rollouts replace analog fiber links with digital versions, generally increasing SNR by a few dB. We’ll cover the details of how these few dB’s can save a lot of dollar Bills, but in short the higher modulation orders enabled by higher SNR’s can allow delay in investment in CCAP ports/licenses.
- On the flip side – some operators are looking at rolling out 204MHz as a tactic to delay the need to adopt DAA. By increasing usable spectrum by ~5x vs a 42MHz system, adequate upstream bandwidth can be gained to buy time for DAA solutions to further mature and costs drop before they are deployed.
Hopefully this has piqued your intertest in learning more about what’s new with each of the upstream capacity expansion options. In the next few installments we will discuss how each of these three primary methods are being used, often in combination with others, to keep up with exploding upstream bandwidth demand. We will discuss the benefits that each offer, the challenges that they present, and how operators are continuing to find success with them. Stay tuned for more insightful information about the Advanced Upstream!