LightReading recently reported on a showcase at CableLabs where Charter and Comcast demonstrated the companies’ progress in testing the concepts behind DOCSIS 4.0. This is the big cable upgrade that will allow the cable companies to deploy fast upload speeds – the one area where they have a major disadvantage compared to fiber.

Both companies demonstrated hardware and software that could deliver a lot of speed. But the demos also showed that the cable industry is probably still four to five years away from having a commercially viable product that cable companies can use to upgrade networks. That’s a long time to wait to get better upload speeds.

Charter’s demonstration was able to use frequencies within the coaxial cables up to 1.8 GHz. That’s a big leap up from today’s maximum frequency utilization of 1.2 GHz. As a reminder, a cable network operates as a giant radio system that is captive inside of the coaxial copper wires. Increasing the range of spectrums used means opening up a big range of additional bandwidth capacity inside of the transmission. These new breakthroughs are akin to the creation of G.Fast which harnesses higher frequencies inside the telephone copper wires. While engineers can theoretically guess how the higher frequencies will behave, the reason for these early tests is to find all of the unexpected quirks of how the various frequencies interact inside of the coaxial network in real-life conditions. A coaxial cable is not a sealed environment and allows interference from the outside world that can interfere unexpectedly with parts of the transmission path.

Charter used equipment supplied by Vicma for the node, Teleste for amplifiers, and ATX Networks for taps. The node is the electronics that sit in a neighborhood and converts the signal from fiber onto the coaxial network. Amplifiers are needed because the signals in a coaxial system don’t travel very far without having to be amplified and refreshed. Taps are the devices that peel signals from the coaxial distribution network to feed into homes. A cable company will have to replace all of these components, plus install new modems, to upgrade to a higher frequency network – which means the DOCSIS 4.0 upgrade will be expensive.

One of the impressive changes from the Charter demo was that the company said it could overlay the new DOCSIS system over top of an existing cable network without respacing. That’s a big deal because respacing would mean moving existing channels to make room for the new bandwidth allocation.

Charter was able to achieve a download speed of 8.9 Gbps download and 6.2 Gbps upload. They feel confident they will be able to get this over 10 Gbps. Comcast achieved speeds on its test of 8.2 Gbps download and 5.1 Gbps upload. In addition to researching DOCSIS 4.0, Comcast is also looking for ways to use the new technology to beef up existing DOCSIS 3.1 networks to provide faster upload speeds earlier.

Both companies face a market dilemma. They are both under pressure to provide faster upload speeds today. If they don’t find ways to do that soon, they will lose customers to fiber overbuilders and even the FWA wireless ISPs. It’s going to be devastating news for cable stock prices in the first quarter after Charter or Comcast loses broadband customers – but the current market trajectory shows that’s likely to happen.

Both companies are still working on lab demos and are using a breadboard chip designed specifically for this test. The normal lab development process means fiddling with the chip and trying new versions until the scientists are satisfied. That process always takes a lot longer than executives want but is necessary to roll out a product that works right. But I have to wonder if cable executives are in a big hurry to make an expensive upgrade to DOCSIS 4.0 so soon after upgrading to DOCSIS 3.1.