Best Practices DOCSIS

A Technical Guide to DOCSIS 3.1 – Part 1: Increasing Capacity

By Incognito on September, 30 2015

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Updated August 27, 2019

Originally published in September 2015, this technical guide is designed to equip network professionals with the information they need to fully understand DOCSIS 3.1, and to leverage the standard’s capabilities to provision next-generation cable services.

Fast forward to 2019! Incognito is pleased to provide a number of updates on our DOCSIS 3.1 technical guide. We hope you enjoy our blog Part 1 of 3 on DOCSIS 3.1.

Happy reading!

Sonya Goodanetz
Solutions Marketing - Incognito Software

The majority of global cable providers are planning to or are currently upgrading to DOCSIS 3.1. Below is an at-a-glance view of DOCSIS 3.1 deployments in North America (source: June 2019 Light Reading webinar):


As DOCSIS 3.1 adoption and rollouts continue to gain traction, let’s inspect what the 3.1 standard provides and the factors to consider in a network upgrade.

At the most basic level, DOCSIS 3.1 boosts bandwidth capacities to 10Gbps downstream and raises upstream to 1Gbps. The DOCSIS 3.1 standard is backward compatible with DOCSIS 3.0, easing your network migration efforts. Although DOCSIS 3.1 delivers significant capacity improvement over DOCSIS 3.0, the bandwidth growth rate is roughly half of the Butter’s Law prediction.

Now at DOCSIS 3.1 4096-QAM modulation, we end up just north of 64.32Mbps while the previously capped modulation of 256-QAM achieves a theoretical rate of 42.88Mbps, presenting a 50% theoretical data capacity increase using the same 6Mhz channel. In reality, the two numbers translate to 54Mbps and 38.81Mbps respectively (due to DOCSIS overhead and spectral efficiencies).

How is this all achieved? The answer is spectral efficiencies of higher-order modulations. By employing 256-QAM, the highest modulation available in DOCSIS 3.0 as a benchmark, let’s compare at a basic level what the spectral efficiencies are using this formula:

bandwidth = rate* x log2(modulation)
(*where 256-QAM rate as defined by the ITU-T standard J.83 (12/07) at 5.361 Msym/s)

So what does this mean for service providers?

Numerous technical advantages will be explored in part 2 of this guide, but the biggest selling point is the additional bandwidth capacity for your subscribers. As detailed above, driving a 50% data capacity increase is no minor feat for service providers. Who wouldn’t want faster, more reliable service speed and increasing capacity to add additional users?

While many operators still employ DOCSIS 3.0 equipment, now is the time to extend the life of your copper plant with DOCSIS 3.1. Check out part 2 of the blog series for a list of the technical advantages enabled by DOCSIS 3.1.

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