In reply to a post by XGS_Is_On:

Most 3.1 modems can only lock to 2 OFDM downstream blocks and no modem locks more than 8 SC-QAM 3.0 upstream channels.

The downstream OFDM blocks go from 24 to 192 MHz wide. At 14 bits per Hz 2 of those will be just fine for 2 Gbit to a single customer even without the 32 3.0 downstream QAMs the modems lock to.

3.1 upstream is way more efficient: it'll go up to 2k QAM if the plant is clean enough and can drop individual carriers if there's narrowband noise instead of the entire channel. It comes in channel sizes between 6.4 MHz, the current SC-QAM size, and 96 MHz - equivalent to 15 3.0 channels but with modulation orders way higher.

One OFDMA block upstream should be good for the foreseeable. The plan will be, in coaxial areas, to turn off the 3.0 carriers and enlarge the 3.1 block as customers move off 3.0.

There isn't enough spectrum to have 12 * 3.0 channels regardless. Would need 76.8 MHz of clean upstream which isn't there. The spectrum is flaky below 20 MHz and ends at 85. 5 or 6 SC-QAM and the 3.1 OFDMA should be fine for new speeds. Usage hasn't gone up much with folks going to Gig1 it's mostly the same stuff faster.

The RFoG areas are a different story. They can't have 3.1 upstream so will have to be packed with 3.0. 8 of them ideally.

out of curiosity why cant us RFoG customers get it

I *think* its a limitation on the upstream RF bandwidth the Boostral RFOG ONU's can pass.

In reply to a post by Pheasant:

I *think* its a limitation on the upstream RF bandwidth the Boostral RFOG ONU's can pass.

Kinda. OFDMA multiple modems will want to burst at the same time with very little wavelength separation as they can each take some OFDMA carriers from the same block simultaneously. This doesn't impact the hybrid network, they just transmit at the different frequencies and the RF is aggregated by the network, however RFoG two lasers bursting at the same time at such close wavelengths causes Optical Beat Interference - lasers drift a touch in wavelength as they warm up.

https://www.commscope.com/globalassets/digizuite/165... explains this along with suggestions to mitigate it in excruciating detail. I'm not going to claim to understand this very much: it's way beyond me.

VM could use these mitigations, or they could just use more 3.0 upstreams until it's not enough then introduce XGSPON.

Thanks squire. That's more than enough technical depth for me at least. Very interesting.

Roll on XGS-PON for them I say!

In reply to a post by Pheasant:

Thanks squire. That's more than enough technical depth for me at least. Very interesting.

Mashed my brain as well mate. I was happy to take in the executive summary and accept it on that one!

I know my niche and that degree of detail on optics definitely isn't it.

DS still seems ok, US at peak falls below 20mbit now, given what you reported with a 3.1 channel appearing and then vanishing not to be seen again I will be pushing VM to provide me an answer before my 14 day period ends.

Edited by Chrysalis (Sat 05-Nov-22 20:11:38)

In reply to a post by Chrysalis:

I will be pushing VM to provide me an answer before my 14 day period ends.

Good luck, even executive complains couldn’t fix my summer time fault, I’m avoiding paying VM any more money until either a) they fix this insanity, or b) OR or an altnet appear. I’m probably going to be waiting 5+ years 😂

Did a few more tests randomly at peak, US now ok, also now set a fq_codel for it to keep latency down during uploads, seems no need to shape downstream though with this capacity, every single peak test has been perfect for downstream, no issues streaming, youtube, netflix etc.

Ok got a response from VM.

The hub site is 50mhz spec and the spectrum isnt available in my area for a 3.1 channel, it wont be coming in 2023, of course given at some point a stop will be put on DOCSIS, I am assuming at this point it means no.

So this I guess confirms the 3.1 US is not going to be universal around the country.

I will be keeping the package though as everything downstream related has been perfect, I am not even seeing flickers of visible contention at 9pm in the evening.

In reply to a post by Chrysalis:

I will be keeping the package though as everything downstream related has been perfect, I am not even seeing flickers of visible contention at 9pm in the evening.

Good to hear. Guess no IPv6 or static IP options that you had with AAISP but otherwise a good fast service.