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