CableLabs recently put the finishing touches on the new DOCSIS 4.0 standard – the latest standard for delivering broadband across hybrid fiber-coaxial networks. The changes are intended to make cable networks more competitive with fiber networks – although it’s unlikely that we’ll see anybody use the full capacity of the new standard.
Following are the benefits promised by CableLabs in the DOCSIS 4.0 press release:
Speeds up to 10 Gbps. This capability isn’t quite what it seems. The current DOCSIS 3.1 standard already allows speeds up to 5 Gbps and no cable company is delivering superfast speeds because it’s not practical. The only way to achieve 5 – 10 Gbps broadband would be to remove most or all of the channels of TV signal from the system.
Cable systems could consider upgrading to speeds faster than 1 Gbps if they make another costly upgrade of migrating to IP video. Today a cable company sends all TV channels to every customer and blocks the channels that are not subscribed. An IP video system, which is used on DSL and fiber networks only sends a customer the channel they are watching. Such a migration would free tremendous bandwidth within the network but would mean replacing the cable headend and all settop boxes.
Faster Upload Speeds. DOCSIS 4.0 will be able to deliver as much as 6 Gbps upload speeds to go along with the 10 Gbps download speeds. This would allow a cable company to offer a symmetrical 1 Gbps bandwidth product – something that is not possible today and that puts cable networks at a marketing disadvantage compared to fiber. The current DOCSIS 3.1 technology provides for one-tenth of the download speed to be provided as upload – meaning a 100 Mbps download product typically has a 10 Mbps upload speed. Interestingly, many cable products today don’t even use the full 10% upload allotment and assign more bandwidth instead to download.
Improved Reliability. CableLabs is pushing higher reliability as part of the DOCSIS 4.0 upgrade. This will be done using new software they’ve labeled as Proactive Network Maintenance (PNM) that will use increased monitoring and machine learning to identify network problems earlier. However, this technology will become available with DOCSIS 3.1 as well and doesn’t require an upgrade.
Better Security. CableLabs is also touting increased security through a software suite labeled as Micronets. This will allow the cable operator to isolate different parts of the network into separate trust domains so that a problem in one part of the network doesn’t infect the rest of the network. That’s an interesting concept that would also benefit fiber networks.
Low Latency. The last touted benefit of DOCSIS 4.0 is lower latency. There is no way to improve the native latency across a coaxial cable network, so the improved latency comes as a result of a bit of smoke and mirrors. A given customer, such as a small cell site in a residential neighborhood could be given the best possible latency by giving it traffic a priority over all other traffic. This was exactly what net neutrality was supposed to protect against and residential customers in that neighborhood would likely be highly dismayed to know that connection problems are due to the cable company selling priority bandwidth to AT&T in the neighborhood.
Expanded Use of Spectrum. The extra bandwidth for DOCSIS 4.0 comes from the expansion of the frequencies used inside the coaxial cable. Coaxial networks function like a captive radio system inside of the coax and DOCSIS 4.0 expands the usable spectrum on the cable to 1.8 GHz – most cable networks today use 1 to 1.2 GHz of spectrum.
What’s not mentioned in the press releases is the cost. Expanding the spectrum likely means replacing amplifiers and possibly even power taps in the cable network. Using the new spectrum and standard means a swap-out of cable modems. It’s possible in some networks that moving to the increased spectrum will also mean replacing older or frail coaxial cable in the network.
So far, no major cable company has said that they are interested in this upgrade. However, cable companies are under increased pressure to improve upload speeds. They don’t necessarily need to move to symmetrical speeds. However, the weakness of upload bandwidth in cable networks have been highlighted as millions of people try to connect to work and school servers from home during the COVID-19 crisis – I’ve seen more demand for faster upload speeds in the last few weeks than I can ever remember in the past.