Doesn't really matter in the grand scheme. The extra upload will be useful for those tied to VM, the extra download in very rare cases, but it's nothing transformative.
I'm not actually entirely clear what the point of moving from 350 to 500 is. PR I guess.
Well as they said they are keen to keep at the top of the speed tree. So yes seems pure PR and nothing more. Will see what the price is - As I said a few days ago 2 FTTC come to £41 a month and so if the price is too high it's worth getting that and keeping the higher upload than just getting 500/35 if say it's £55-£60 a month
Re: How soon can we upgrade to Gigabit/Gigabit speeds over DOCSIS 3.1? #Gigaworld #ProjectLightning
Anyway - EuroDOCSIS 1/1.1/2 covered return path of 5-65 MHz. DOCSIS 3, whether US or Euro variety, requires that the modem support either 5-42 MHz edge to edge upstream band or 5-85 MHz. The lower band is to allow support for legacy cable systems where the forward / downstream path starts at 50 MHz, this was this way to accommodate analogue TV and out of band communication. It starts at 108 MHz on other systems.
I'll try and keep this short and to the point but will fail.
The restriction is the same one that forced VM to rebuild a bunch of networks when they moved, briefly, to the 10:1 upstream ratio. Obviously as the upstream and downstream travel on the same cable they are frequency divided and there needs to be the capability in the coaxial amplifiers, along with the optical nodes that convert the RF into light for travel down fibre, to know what's upstream and what's down and hence what to amplify then feed to the upstream transmitter and what to feed to the downstream transmitter. This is done via diplex filters - these are pluggable modules in newer kit but older HFC networks aren't quite the same story.
There is also the issue of laser loading. All the collected noise, ingress, and of course wanted upstream data on a network segment gets collected together, amplified, and drives the return path laser in the optical node. If that laser can't handle the input it will clip - what is going along the lasers is an analogue signal and if the laser is overdriven you lose the higher amplitudes as they're outside of its capabilities. Same actually happens on the coaxial amplifiers too, much as with a guitar amplifier if the input it too strong you get distortion.
VM have the very odd network area left with a return path edge that's stuck at 42 MHz - these have 3 bonded upstream channels at most. They are being rebuilt with the constraining components being replaced with more capable kit.
Some other kit stops at 50 MHz on the return path. This is being overbuilt too. These can handle 4 upstream channels however maybe not at 64QAM, as 64QAM means higher power hitting the return path laser which can cause those nodes to clip.
There's some EuroDOCSIS ready kit that goes up to 65 MHz. You can actually see this stuff in use where areas have 5 or 6 upstream channels in use. VM only bond 4 but you see a channel in the mid-50s usually at 53.7 MHz central and another in the low-60s at I think 60.3 MHz. Note that there are plenty of areas that only have 4 channels present on the segment so these extra higher channels aren't required.
Areas that go to 50 MHz look exactly the same as other areas with 4 channels - highest channel is at 46.2 MHz. Remember this is the middle of a 6.4 MHz wide channel, 46.2 + 3.2 = 49.4 MHz.
Lastly there're the newer build HFC networks and, I presume, the newly overbuilt networks. These have the full mid-split 5-85 MHz upstream range, and are field upgradeable by replacing the diplex filters to 5-204 MHz upstream range.
Aside from policy decisions there is no reason why VM couldn't bond 8 x 64QAM 3.0 upstream channels in these newer build areas, and indeed the FTTP areas for DOCSIS 3.0, and run DOCSIS 3.1 in hybrid mode on the upstream too - the 3.1 upstream block can co-habit the same spectrum as the 3.0 upstreams on a time-share basis so they could happily shove a 64 MHz wide OFDMA block alongside the 51.2 MHz of DOCSIS 3.0 upstream.
VM do not like taking account of different conditions of local networks, however. The equipment serving me here in this Project Lightning area is in 5-85 MHz upstream mode, has a 108 - 1218 MHz downstream spectrum, and VM are using 25.6 MHz of the upstream capacity, with the downstream signals going as far as 750 MHz.... as that's a common value where older network tops out. I'm on the same frequency plan on this 5-85 MHz or 5-204 MHz up and 108-1218 MHz or 258 - 1218 MHz downstream network as a dude running on HFC built in the mid 90s topping out at 5-50 MHz up, 88-750 MHz down.
The FTTP / RFoG Lightning guys are on much the same story.
Things are changing. Slowly. VM's techs are banned from installing forward path attenuators now - they attenuate some of the spectrum that'll be wanted for upstream. The newer v6 STB has no DOCSIS modem in it - this is intentional to try and ensure the return path ends at the DOCSIS gateway and the feed to the set top boxes can have return path filters put in place to reduce in-home interference flowing onto the network.
I've a document detailing how another operator went full 3.1 including the high-split 204 MHz return path. Interesting stuff.