Cable companies have always been stingy with upload speeds because it hasn’t really mattered to the public. Only a handful of customers who wanted to upload large data files ever cared much about upload speeds. But connecting to a school or work server or talking on Zoom requires dedicated upload connections – and when those functions suddenly became a part of daily life, people suddenly cared a lot about upload broadband speeds.
By now, most cable companies have upgraded their networks to DOCSIS 3.1. This allowed upgrades of download speeds from a maximum of perhaps 200 Mbps up to a gigabit. Unfortunately, as part of this upgrade, many cable providers did nothing to improve upload speed.
People may not realize that the signals inside of a cable company network use radio frequencies to transmit data, meaning a cable network is essentially a captive radio network kept inside of the copper coaxial wires. As such, the signals inside a coaxial system share the same characteristics as any wireless network. Higher frequencies carry more data bits than lower frequencies. All of the signals are subject to interference if external frequencies leak into the cable transmission path.
The DOCSIS specification for cable broadband sets aside the lowest frequencies in the system for upload bandwidth – the spectrum between 5 MHz and 42 MHz. This happens to be the noisiest part of cable TV frequency – it’s where outside sources like appliances or motors can cause interference with the signal inside the cable network.
The DOCSIS 3.0 specification, released in 2006 allowed for other parts of the spectrum to be used for upload data speeds, but very few cable companies took advantage of the expanded upload capability, so it’s laid dormant. This DOCSIS 3.0 standard allowed a mid-split option to increase the frequency for upload to 85 MHz. or a more-aggressive high-split option to assign all of the bandwidth up to 204 MHz to data upload. DOCSIS 4.0 is going to offer even a wider range of upload speeds, as high as 684 MHz of spectrum.
It’s been widely reported during the pandemic that millions of households have upgraded to faster broadband packages in hopes of solving the upload problem. But upgrading download speed from 100 Mbps to 200 Mbps won’t help a household if the upload path is the same with both products.
Cable companies are faced with a big cost dilemma. It’s costly to upgrade a cable network from today’s stingy upload speeds to the mid-spit or hi-split option. Rearranging how the bandwidth is used inside of a cable network means replacing many of the key components of the network including neighborhood nodes, amplifiers, and power taps. It could mean replacing all cable modems.
It’s hard to know what cable companies will do. They might be hoping that the issue blows over when people and students move back out of the home. And to some extent that could happen. We saw the average monthly download bandwidth used by homes drop this year from 404 gigabytes in March to 380 gigabytes in June after home-schooling ended for the spring school year. There is likely going to be some relief for upload bandwidth demand when the pandemic is finally over.
But there is a lot of evidence that the increased demand for upload bandwidth will never drop to pre-pandemic levels. It seems likely that millions of jobs are going to permanently migrate to the home. It seems likely that schools will more freely allow students with illnesses to keep up with schoolwork remotely. High school students are likely to see more options for advanced placement classes online. It looks like video conferencing is here to stay.
Will cable companies make a big investment just to improve upload speeds? Most of don’t plan to upgrade to DOCSIS 4.0 until near to the end of this decade and might decide to spend no other capital until then – since that future upgrade will mean replacing all components of the network again. The cable companies have the ability to greatly increase upload speeds today – but my bet is that almost none of them will do so.