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 wrap up the HFC Advanced Upstream discussion, talk about what’s next for Cable, and discuss where the competition is headed.

How Cable Operators Increase Upstream Bandwidth

Even as HFC architectures and technologies continue to rapidly evolve, today there are still three primary methods for operators to turn to for increasing upstream capacity.  How these methods are applied is changing to keep up with the new technologies and competitive forces.  Distributed Access Architectures are enabling capacity growth through node splits, mid-split and high-split architectures allow growth in spectrum with active carriers, and OFDMA is getting us more Mbps per Hz of upstream spectrum.

What’s Next For Cable Upstream Capacity?

  • OFDMA adoption will continue to accelerate as 1 CPE deployments grow. It’s a no-brainer to get the most from the spectrum that you have today, and this includes maximizing SNR through disciplined ingress remediation and plant leakage management.  Tight plants simply pass more packets
  • Split changes will occur at a slower pace due to the level of planning and outside plant work required. 18 months ago the mid-split seemed to be the architecture of choice for operators pursuing a split change, but post-pandemic operators are realizing that the incremental work between 85 and 204MHz upstream conversions is not that large relative to the massive capacity gains possible with a high-split.
  • DAA is the method that will both directly and indirectly drive the biggest change in broadband services going forward. For HFC, DAA rollouts will continue to accelerate as R-PHY solutions continue to mature.  R-MACPHY will claim a larger share of the DAA mix as FMA specs take hold and interoperability between solutions becomes reality.  DAA will also continue to drive fiber, including 10G optical Ethernet links, deeper into the access network enabling Full-Duplex DOCSIS (FDX), PON deployments via Remote OLT’s, and fixed wireless xHaul.

What is Full-Duplex DOCSIS (FDX)?

The next major game-changer for HFC upstream capacity is Full-Duplex DOCSIS (FDX).  With FDX spectrum can be shared between upstream and downstream, removing the bottleneck on upstream spectrum allocation.  No longer would an operator need to “hardwire” their plant for a set upstream/downstream split, changes in spectrum utilization could be made dynamically to adjust to changing demand.  Specifications are complete for FDX and at least one silicon vendor is hard at work on chipset development, but adoption is generally considered to be at least a few years out.  The current N+0 requirement for full functionality will be a major barrier to overcome, for this reason and others the majority of MSO’s are holding off on FDX deployment planning.

How Does DAA Enable PON Services?

DAA will indirectly enable broadband services previously viewed as competitive to DOCSIS, with the first being PON.  With DAA, 10G optical Ethernet is now being deployed deep into the access network, often using DWDM fiber technologies.  Instead of having discrete point to point fiber connections between the hub and each fiber node, DWDM fibers carrying Ethernet traffic are routed into the access network to a DeMUX.  At this DeMUX a wavelength can be peeled off to connect each RPD to the CCAP or v-CCAP.  Similarly, other wavelengths can be used to support Remote OLT’s (R-OLT) for PON deployments.  The same Converged Interconnect Network (CIN) can support both services, with the only differences being CCAP/RPD or ONT/R-OLT endpoints.  North American cable operators are generally deploying EPON due to DPoE compatibility enabling reuse of existing provisioning systems, etc.


What is Fixed Wireless Access?

A similar concept applies for wireless xHaul, including fixed wireless access for residential broadband services.  Wavelengths can be peeled off for 10G (or possibly 25G in the near future) optical Ethernet links to provide small cell xHaul.  These access points can be part of an overall fixed wireless access service to complement DOCSIS for operators providing both wireless and wireline services, or to compete with DOCSIS for pure-play wireless operators.  Consensus exists amongst many analysts that this type of service only makes financial sense for niche use cases and is not a widescale threat to HFC broadband service providers at this time.

What Else is Out There?

The other emerging broadband competitor is satellite-based internet.  The old-school services like ViaSat were only viable as a last-resort internet provider due to high latency/low speed and price concerns.  New competitors like Starlink using huge constellations of low-earth-orbit (LEO) satellites are considerably more capable.  Starlink has ~1,600 satellites in orbit with plans for 3-4 times that many in the next few years.  Amazon has announced plans for a similar constellation, as have some European/Asian countries.  These services get even more interesting as they contemplate laser-based connections between satellites essentially creating a mesh network, but this is many years in the future.  While these LEO constellations pose a broader threat vs ViaSat, they will still face challenges serving massive bandwidth for large numbers of users, so will also likely be somewhat relegated to customers without a competitive wireline broadband option.


It is likely that much of the information in this blog series was not news to you, but hopefully framing the upstream capacity expansion options into the three primary buckets has helped you think through the opportunities, challenges, and tradeoffs between them differently.  There is clear path for HFC to remain the broadband medium of choice for many years to come using just these architectures and technologies available today, and if the past is any predictor of the future even more exciting innovations are yet to come.


Want to learn more?  Listen to the Broadband Lounge Podcast Series or visit the VIAVI Advanced Upstream Page for more information.


Be sure to follow VIAVI on LinkedIn to see the rest of this blog series

About The Author

Jim has over 25 years experience in telecommunications and semiconductor industries serving in primarily engineering, product line management, and marketing roles. He is currently a Solutions Marketing Manager at VIAVI Solutions focusing on HFC and fiber broadband service delivery with previous experience at Intel and Delphi. Jim received both undergraduate and MBA degrees from Purdue University, holds 7 US patents, and is a six-sigma black belt.

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