Virgin Media Network Quality
 

Why does the network (which can deliver a lot) lack quality? Why does the network have limitation on upload? In simple terms please. Theres so many whys as to why! the network isn't running as well as it could, may be?

Re: Virgin Media Network Quality
 

TH

I think you need to define the term "quality" as you see it for the purpose of the question.

I can certainly answer the question as regards upload limitations. In simple terms (I can explain it in much greater depth), the upstream operates in a noisy-ish (susceptible to noise) part of the frequency spectrum. Accordingly the packing density of upstream data is lower than downstream so that the potholes created by noise can be corrected at the CMTS. The frequency range is prescribed by international bodies.

The only way of increasing upload speed within these limitations is to bond upstream channels.

Re: Virgin Media Network Quality
 

The sort of quality on openreach fibre. would DOCSIS 3.1, on a new spectrum be the only answer? or can DOCSIS 3 be worked on. Bonding aside, could VM do other things?

Re: Virgin Media Network Quality
 

There's also a lot less of it.

---------- Post added at 12:04 ---------- Previous post was at 12:02 ----------

1) It's a shared, CSMA-TDMA network. Openreach fibre is not. Every modem has to guess and randomly try to send data requests on VM. On Openreach fibre anyone or any step wanting to send data can always just send immediately.

2) It's a RF hack over a coaxial network. You're basically shoving a ton of wifi signals down a copper cable instead of an antenna. Fibre is, well, fibre using purpose-made Ethernet protocols.

Re: Virgin Media Network Quality
 

The width of the spectrum is small?

Re: Virgin Media Network Quality
 

Akin to the house<>cabinet link in FTTC, albeit with a reduced bandwidth, except the copper pair is less suitable for this application than coax...

I think the differences are more to do with the fundamental architecture rather than the technology used for the 'last mile'.

Re: Virgin Media Network Quality
 

Just to help me understand too, all these limitations are with VM's actual fibre structure and nothing to do with the coax part? Does the Coax part also add issues on top in a similar way as a copper line to the property?

Re: Virgin Media Network Quality
 

Openreach's solution for the upstream uses a totally different frequency plan. Someone can correct me but the upstream and downstream are in the same frequency zone somewhere like DOCSIS downstream. So upstream isn't as susceptible to RF noise.

For VM to improve upstream/downstream symmetry, and given that they cannot leave the specturm they're using on DOCSIS 3.0, bonding is the only uplift solution.

I'm not privy to VM's DOCSIS 3.1 plans. But a layman's description of what needs to be done fore the upstream can be found here:
http://www.lightreading.com/blog.asp...27176&site=cdn

This would put the upstream into half the space currently occupied by downstream, which would move further up the frequency spectrum. However, this would still not provide the same number of total channels for the upstream as there are for downstream. So bonding would be lower; QAM would be higher than at present and upstream speeds will remain asymmetric with downstream but will be higher than at present.

Re: Virgin Media Network Quality
 

Looks like you partly answered my question as I was typing it ferretuk :)

Re: Virgin Media Network Quality
 

The coax part, to my mind, is where the RF noise ingress occurs. Of course that does include the RF/Optical conversion node.

Re: Virgin Media Network Quality
 

Hi one question maybe out of all these
To my cabinet is going fibre cable, then from cabinet going to the property coax cable at the SH
Will SH operate normal (and give better quality to line) if this coax will replaced with fibre going to the property & so to SH?
Thanks

Re: Virgin Media Network Quality
 

Kind of both. VM's network uses the same protocols (with the same limitations) over both the fibre and copper part to the CMTS.

Openreach FTTC uses different protocols, both specific to each interface. In other words DOCSIS cable uses the same (RF) protocols over fibre whereas FTTC uses Ethernet on the fibre part.

---------- Post added at 13:03 ---------- Previous post was at 13:01 ----------

Agreed. Though technology used is inextricably linked to the architecture and vice versa.

Re: Virgin Media Network Quality
 

so to my query at post 11 will not make difference pure fibre instead of coax from cabinet to home unless it will be faster transmitted due to the advance of the fibre

Re: Virgin Media Network Quality
 

To your cabinet is going coax from another cabinet which has the coax to fibre conversion.

So VM FTTH in coax areas is prolly not in prospect owing to the infrasytructure costs involved. They are piloting FTTH but I believe that it is pole strung fibre.

Re: Virgin Media Network Quality
 

thank you

Re: Virgin Media Network Quality
 

cable can do more than what VM achieve, the issue is they have too many customers per node and as such performance is poor.

eg. VM could bond 4 QAM64 US channels instead of 1 QAM16 US channel and halve the modems connected to that service group at the same time and you would probably see even with say 20mbit upload much lower network jitter/congestion. It still would have the issue Qas said of modems not able to send data at the same time as each other but with less modems per node it becomes less of an issue.

Part of the problem is the tech but I think the biggest part of the problem is how VM have chose to sell the service.

The openreach FTTC infrastructure could have potentially had much higher contention ratio than it has now but openreach chose to build it the way they did so the chance of congestion on the local access network is remote, but there is still contention on the dsl signal on openreach FTTC services so crosstalk drops attainable speeds as well as contention on backhaul and peering/transit etc. so both technologies have their own downsides.

Re: Virgin Media Network Quality
 

In addition, the cable based systems have to share the bandwidth available with TV and with the increase in HD channels this leaves little room for broadband.

In my view, it is just too easy to add new punters to the HFC network. In addition, the ability to increase a customer’s speed by a simple configuration change makes it all too easy to have the contention ratio increase on a cable segment to the detriment of all.

As already mentioned, the shared nature of the HFC and the requirement for multiple access onto the same cable by many modems leads to problems with packet jitter.

Re: Virgin Media Network Quality
 

Well VM could use QoS and assured timeslot scheduling but they don't

Re: Virgin Media Network Quality
 

yes there is that too.

Re: Virgin Media Network Quality
 

One thing I'd like to know about is why cable companies don't ditch the TV service then use the available bandwidth from that for their broadband service then offer the same channels over IPTV for those that want it and for those that don't want TV they could benefit from having faster broadband from the extra capacity. I would hazard a guess at it costing a lot to implement in such a manner or does the technology just not allow for it? Probably a silly question but it interests me :P

Re: Virgin Media Network Quality
 

Possibly your homework over XMAS could start here > DOCSIS 3.0 Tutorial - The eQAM

Not forgetting CM-SP-MULPIv3.0-I16 or I15 if more publically available (euroDOCSIS/CableLabs) standard and possibly DOCSIS DRFI specs….
Noise robustness facilitated by interleave (at expense of increased latency) is also a factor in why MPEG transport overhead likely to still be retained..mixed in with DOCSIS QOS (not the same as IP/TCP QOS!) etc….

Have fun digesting that lot! - will look forward to your review… ;)

Re: Virgin Media Network Quality
 

You little (!) divil, Horse!

Re: Virgin Media Network Quality
 

Probably because very few networks have got multicast IPTV to work properly