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DOCSIS 3.1 has been with us for several years now and is performing better than most had expected. It allows for increases in overall data throughput (Mbps and yes, Gbps) to happen often within the same RF frequency bandwidth (MHz). It all happens with a few protocol elements that differ from previous versions and make this the most Efficient version of DOCSIS to date. Let’s take a look at some of the building blocks of D3.1 and how they work at a high level.

Runs On Your Existing HFC Plant

Many operators thought that massive changes had to happen to their existing plant to get D3.1 to work. Completely False! While DOCSIS 3.1 was built to take advantage of RF spectrum upgrades to both the forward and return path, it can run on the architectures that may have been built decades ago and still provides beneficial results. You do NOT need to have an 85 MHz upstream (but you can). You do NOT need to have a 1.2 GHz downstream (But you can). You do NOT have to be Node + 0 (but you can). A vast amount of deployments have been done on 20+-year-old plants with Node + 6 and higher. Being able to use what you already have means maximum efficiency.

Backwards Compatibility

Like all previous versions, DOCSIS 3.1 leverages backward compatibility in the products. DOCSIS 3.1 modems can listen to and transmit DOCSIS 3.0 carriers. They can also bond both the D3.0 and D3.1 carriers together to form a massive amount of bandwidth. Why is this important? Yet again, you do not have to wholesale get rid of all of the modems bought and paid for and currently making you money in your plant, especially on subscribers paying for lower speed packages. This allows an operator to drive D3.1 modems into the network slowly. You may start with your highest bandwidth package subscribers or the ones that consume the most bandwidth consistently. Why? By separating those super users from the others, everyone perceives a better experience. You can also purposely send D3.1 modems to your end-of-line subscribers since they have built-in full-spectrum analyzers and Proactive Network Maintenance (PNM) tools to help you take care of your plant. Overall, DOCSIS 3.1 offers excellent flexibility for operators to make it work for them and fit their network instead of fitting your network to it. With all of these great benefits, operators need to look at how the deployment of DOCSIS 3.1 can help evolve their network, offer massive speed packages to subscribers and make things run more efficiently. It is already successfully deployed by hundreds of operators across various architectures and vintages of networks.


OFDM (Orthogonal Frequency Division Multiplexing)

This multiplexing method uses non-interfering or “orthogonal” sub-carriers that eliminate cross-talk between channels and remove the need for complicated and expensive filters like in most frequency multiplexing types. By doing this, we can basically “pack” the carriers more tightly together, thus allowing more data throughput in the same amount of RF space.


LDPC (Low Density Parity Check)

LDPC is a revolutionary error correction method developed in the 1960s that was forgotten about until the mid-1990s when computers became fast enough to handle it. This provides error correction so great that it allows communication protocols to run in noisier environments or run even better and faster in a clean environment.

Modulation Profiles

Since the beginning of DOCSIS, all modems in a service group have always run at the same modulation rate. Most recently, 256 QAM for downstream was what we were stuck with using DOCSIS 3.0. With DOCSIS 3.1, not only do we get the ability to move up to the likes of 4096 QAM downstream, but every modem gets to select the profile that will work the best for it. In short, these profiles are chosen by using a table of SNR values that are paired with the different modulation profiles.

By using OFDM and LDPC, we can now achieve these new, higher modulation rates. Not only can each modem use the most optimum profile, thus giving it more speed potential, but the profiles can also have different modulations in use per subcarrier in each profile. Therefore, getting too correctly optimized to the plant it is on as it can. So, pair this optimal profile with the fact that 4096 QAM offers 50% more data throughput than 256 QAM, and you essentially have a bandwidth upgrade without doing a plant upgrade.


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