Brady Volpe and John Downey discuss what you can expect to get out of DOCSIS 3.1 cable modem today. How many modems can transmit in a 6.4 MHz OFDMA channel? How much life is in the DOCSIS 3.1 modem for your network. Also a SCTE EXPO overview and wrap.

What is Possible with a DOCSIS 3.1 Modem Today?

This is episode 85 of Get Your Tech On, our show on All Things DOCSIS. Our topic for today is What is Possible with a DOCSIS 3.1 Modem, an Expo update, OFDMA and more. Brady Volpe, Founder of The Volpe Firm and Nimble This. With us today is John Downey, CMTS Technical Leader at Cisco Systems, welcome back John.

In our Power Hour of Cable on All Things DOCSIS join us and drop your comments into the chat or in the comment window below and be sure to subscribe and give us a thumbs up.

So we were at SCTE Cable Tec Expo. It was awesome. So great to be back amongst all of our friends again. The show went by so fast. If you missed it, Mia put together a short video, let’s take a look.

How many modems can transmit in a 6.4 MHz wide OFDMA channel?

Okay John, so I was giving an SCTE presentation to the Dakota Territory Chapter yesterday – Big shout out to the SCTE Dakota Chapter, hello folks and thank you for having me speak on OFDMA – and I was asked the question “How many modems can transmit at the same time on an a 6.4 MHz wide OFDMA channel”. I did not have a good answer – they stumped the chump. So I thought we would discuss it today. I wasn’t sure which would be a limiting factor, bandwidth, mini-slots, grants. What is your take on this and have you done the math?

What is Possible with a DOCSIS 3.1 Modem Today?

So John moving into the main part of today’s discussion, a topic that was discussed at SCTE expo was the fact that DOCSIS 4.0 hardware was still out in the future but DOCSIS 3.1 hardware is available now and deployed in many cable operator networks. Let’s remind our viewers just how far we can push DOCSIS 3.1 in the upstream and downstream.

● Max downstream: 5 Gbps (subscriber tier: >1 Gbps)
○ Assuming 2 x 192 MHz OFDM + 32 SC-QAM
● Max upstream: 1.5 Gbps (subscriber tier: 1 Gbps)
○ Assuming 2 x 96 MHz OFDMA blocks at 1024-QAM
● How traffic per service flow?
○ Need to explain what a service flow is the audience
● Two modems – 5 G / modem
○ Don’t we saturate the downstream?
○ How does this impact other subscribers on the same node if one subscriber over-utilizes?
● New Chipset that supports more than two OFDM channels
○ 4 OFDM blocks would enable 10Gbps on a single modem

Thank you for your time today. This was a great episode.  Our next Episode 86.

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