Cable networks are helping flatten the curve

Coronavirus is upon us and has brought massive disruption to the way we conduct business. As governments around the world accepted the scientific consensus that social distancing and contact avoidance saves lives by both reducing and delaying the peak number of cases, they have introduced appropriate policies to help "flatten the curve":

As a result, working from home has become the norm over the last few weeks, and consequently many telcos have reported massive increases in bandwidth consumption (for an example, see this great article by Vodafone CTO Johan Wibergh).

One consistent message is that demand for downstream as well upstream bandwidth has spiked - by anywhere between 40-100% depending on operator, geography, how tight the lockdown rules are etc. Vodafone (upstream) example below:

The red line shows the upstream traffic on one of Vodafone’s European fixed broadband networks before the impact of working from home and social distancing measures. The other two lines are for the two subsequent weeks after that change. Source: Vodafone

The downstream side of the bandwidth growth is not in any way worrying for the following reasons:

• modern cable networks have about 950MHz-1.1GHz of spectrum to play with, which allows for up to 9-10 Gbps of aggregate downstream bandwidth. DOCSIS is only using a fraction of this spectrum today (200-400 MHz depending on operator). While the rest of the spectrum is mostly used for digital video broadcast, VOD, even analog TV in some countries, there are many tools that operators can use to harvest this spectrum and deploy more DOCSIS in their networks.
• the majority of downstream traffic is video related, most of it generated by a few dominant players (the Famous FAANG ... Facebook Amazon Apple Netflix Google). Since the advent of adaptive bit rate streaming years ago, video transmission can be tailored depending on available bandwidth between the streaming server and client device (this is why you sometimes get that "Back to the 90s" look on Youtube videos when in an area with poor wireless signal). With this capability in place, these massive content distribution platforms have been able to "downrate" the bitrate of video streams to reduce bandwidth consumption. This can be done by switching to a lower resolution (from 4K to HD/1080p or from 1080p to 480p) or by using a more heavily compressed version of the same resolution. Most of the content on these platforms is not live, so massive amounts of computing power can be applied to achieve very good quality even at high compression rates.
• The downstream bandwdith consumed by video conferencing is somewhat compensated by the fact that people who are video conferencing are - most of the time :) - not streaming HD YouTube at the same time.

Upstream however is another story:

• the majority of networks in Europe still operate upstream spectrum up to 65 or 85 MHz, with only a few having gone through the upgrade to 204 MHz (In the US, most networks are still using an even smaller 42 MHZ of US spectrum).
• Video conferencing, screen sharing and other online collaboration tools are now being used orders of magnitude more than pre-Coronavirus. The upstream bandwidth driven by Coronovirus social distancing policies is completely new and drives a lot of new capacity into a much smaller pipe.

By and large, cable access networks have behaved admirably with upstream bandwidth growth over the last few weeks, enabling a huge amount of people to work from home and keeping kids busy during the day. One little known "secret" is that DOCSIS networks are using an extremely advanced upstream scheduler, that started life many years ago when hundreds of cable modems were competing to transmit data on a single 10 Mbps upstream pipe. Over the years, operators have increased upstream capacity and decreased the number of subscribers sharing the same pipe, but DOCSIS schedulers always had to be very good at ensuring fair bandwidth allocation between multiple subscribers; managing multiple residential subscribers and even business customers sharing the same pipe, and even living up to very strict SLAs with the business customers.

Years and years of investment in growing capacity but also refined scheduler algorithms and advanced testing infrastructure are now showing their value and helping cable networks power through the Coronavirus disruption.