HFC - When will we get better upload speed?

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DonGould

3892 posts

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#115702 3-Apr-2013 22:15

10mbits of upload speed is just pathetic given what this technology can do.

UFB is doing 100/50

I don't see why HFC can't have 100/100 given that it's a DOCSIS3 network.

Why is the speed so poor?

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DoomlordVekk

129 posts

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#793325 4-Apr-2013 16:40

Don, the problem you may be experiencing is "Unrealistic expectation". The HFC/Cable networking technology is by it's nature and the most common deployment scenario, asymmetric and very residentially focused.

The downstream traffic is pumped by box technology that cost hundreds of thousands of $$.

The upstream traffic is pumped by your cable modem that costs less than US$150 each.

The modulation depths downstream and symbol density is often 8 times more in the downstream compared to the upstream.

HFC/DOCSIS is heavily used as residential systems because it cost effectively delivers the higher downstream speeds that 85% of the market looks for, not the symmetrical traffic options that something like Metro Ethernet or the Private IP services that are business class services.

So, you may be trying to apply symmetrical thinking to what is inherently asymmetric.

All I can suggest is if your data needs upstream have grown to a point where you've outgrown the Cable network, you may need step up to a more correctly dimensioned business service.

"Customers don’t expect you to be perfect. They do expect you to fix things when they go wrong." Donald Porter – British Airways

The views expressed here are my own and are not reflective of other organisms or organisations.

DoomlordVekk

129 posts

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#793507 4-Apr-2013 21:28

sbiddle:

DOCSIS3 is technically capable of "infinite" speeds in both directions as speed is only limited by capabilities of channel bonding. Right now there is no mass market DOCSIS3 kit that can utilise more than 4 bonded upstream channels (which is ~100Mbps)

As to why TCL didn't operate bonded upstream channels - that's only something they can answer publically.

Regretably, thats all not quite true. The DOCSIS3 standard is build on a frequency range of approx 600MHz of downstream spectrum and (if you're lucky), 80MHz of upstream spectrum. That effectively limits the (A) number of channels and (B) bandwidth of channels.

Upstream is the rarest of comodities in the cable world. To increase available upstream channel capacities to customers, you basically have to take your existing fibre nodes(suburbs serviced by a ONT and it's coaxial runs), cut them in half and build 2 new nodes, with all the fibre, coaxial and equipment costs that go with that.

To get Don's 108Mb in the Upstream would mean dedicating 4 entire channels to each customer, maybe with some stat muxing gains, that would let you share those channels amongst 20-30 customers.
Cards for CMTSs that provide ~20 upstream channels are listed on eBay for between US$22,000 and US$91,000! You do the maths...

Likewise the silicon processing engines in the cable modems have bonding/multiplexing limitations that have to be taken into account (how vastly clever a piece of radio technology are you normally able to buy for under US$150?).

If you have a sleepless night or 2 thousand, you could have a read of the CableLabs standards.

DOCSIS3.1 is in the process of being rationalised right now, it looks really interesting and will promise that next step in throughput and technology but it's still 15-18 monthe before we see the first leading and bleeding equipment being released by the likes of Motorola, Arris and Cisco.

Fibre is always going to win over copper, very few countries would be looking to deploy HFC networks vs *PON, given the more greater bandwidths available and far lower cost of maintenance just to pick 2 points out.

Channels bonding is alive and well and delivering excellent results in the Vodafone HFC networks, anyone on cable, with a Warpspeed plan can confirm it themselves with a bit of googling.

Enjoy! :)