The dream of Full Duplex DOCSIS 3.1 technology, which could in the next few years’ enable Hybrid Fibre Coax (HFC) cable networks (e.g. Virgin Media) to deliver symmetrical broadband speeds of 10Gbps (Gigabits per second), has moved a step closer thanks to Cisco’s new silicon reference design.
At present the existing Data Over Cable Service Interface Specification (DOCSIS 3.0 / EuroDOCSIS) standard for HFC cable networks can deliver download speeds of several hundred Megabits per second to residential consumers, although upload speeds are often significantly slower (e.g. Virgin’s current top consumer speed is 300Mbps and its uploads are only 20Mbps).
The forthcoming upgrade to DOCSIS 3.1 technology, which is expected to surface over the next year or two, could in theory deliver peak network speeds of 10Gbps download and 1Gbps upload. However the holy grail of HFC is to achieve a Full Duplex symmetrical transmission of 10Gbps (i.e. the same performance for both uploads and downloads).
So far the progress has been good. Earlier this year CableLabs proposed a “viable” model for delivering such performance (here) and a few months later Nokia claimed a “world first” by demonstrating a prototype of their new XG-CABLE technology that could produce 10Gbps in both directions (here). Mind you the proposed point-to-point network and limited distance (i.e. the demo worked at under 200 metres from a distribution point) could be issues, at least in terms of making the upgrade more expensive.
This week saw Cisco add to the fun by unveiling a new silicon reference design for Full Duplex DOCSIS technology, which they say would enable cable operators to “prioritize their capital investments to deliver new services such as faster Internet [and without needing to replace] the existing HFC plant with Fibre-to-the-Premise (FTTP).”
John Chapman, Cisco’s CTO of Cable Access Business, said:
“By making this royalty-free design available to the industry, we can help our cable customers evolve to more rapidly deploy virtualized, fiber-deep, and all-IP infrastructures. We hope to accelerate the transformation of the cable industry to deliver multi-gigabit speeds and new high bandwidth services and products, and in the near future, customers can begin to enjoy the benefits of Full Duplex DOCSIS technology.”
Apparently the new design has been under development for two years by a team of more than 20 Cisco engineers. During that time the team were able to develop a validated reference design for a digital echo canceller that maximizes the use of HFC capacity (i.e. they defined a multi-slice scalable echo canceller (EC) for the Full Duplex DOCSIS specification that seamlessly integrates with the Cable Modem Termination System (CMTS) architecture). Nokia did something similar in their demo.
The technology is scalable for a return path from 200MHz (1.7 Gbps) to 1.2GHz (10 Gbps) and is being demonstrated at the CableLabs Summer Conference in Keystone, Colorado (USA). Further enhancements, such as Fast data – Input/Output (FD.io) and OpenRPD, are due to follow. However a recent roadmap from Arris, which makes a lot of DOCSIS hardware and routers, suggests that the first commercial kit probably won’t be ready until 2018/19.
Of course all this talk about Full Duplex performance is good, but we’ve yet to even see a clear timetable for the introduction of DOCSIS 3.1 into the UK network. Liberty Global (Virgin Media’s parent) initially mooted a 2016/17 introduction for its European operators, but so far there’s been no sign of any customer trials and nobody seems willing to talk about their plans.
Virgin Media are currently laser focused on committing their resources to the Project Lightning network expansion, which is due to complete in 2019 and by then it should have boosted their coverage to 60-65% of the UK (up from around 50% now). A lot of that roll-out also includes DOCSIS 3.1 supporting infrastructure, as well as around 1 million FTTP premises.
On top of that Virgin still have some capacity problems with delivering the full speed to those on their fastest packages at peak times, as demonstrated by their own speedtest data for July 2016. Mind you it’s not uncommon for ISPs to suffer slower speeds during busy peak periods, but they might wish to improve this before offering something even faster.
In any case we probably won’t be talking about Full Duplex performance on Virgin Media’s network for a very long time and what homes need Gigabit uploads today? Ordinary DOCSIS 3.1 should be fine for a long time to come.
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