Wednesday, 17 July 2013

NBN: The UK DSL/FTTN experience

Data from Turnbull's exemplar of FTTN networks (though they call it "FTTC", C is Curb).
This underlines that the data I've previously quoted is consistent across countries.

Note that DSL (ADSL & VDSL) speeds in the UK are consistently better than in Australia.
The maximum exchange distance is 6km and they consistently use 0.60mm wire, not our 0.40mm.
The "skin effect" in conductors affects the propagation of high-frequency signals.
Current only flows in the thin area, measured in micro-meters, on the outside of the conductor.
Hence, the effective resistance at high-frequency is related to the coating (like tin, worse than copper and much worse than gold or silver), the insulation and the surface area - set by the diameter.

For Australia, reduce these distances by at least one-third.

What Speed will I get over VDSL and FTTN?

The only guarantee is there's no guarantee. Achieved VDSL speeds are completely unpredictable.
You might luck-out, you might not. If you are one of the 10% of high-volume consumers, you won't be at all happy with the arrangement.

The 4th-order decay of speed over distance. A Law of Physics.

Over longer distance, ADSL2 beats VDSL2.

From 2010, pre-80Mbps service

Measured speeds. Note they're NOT consistent
The Line Access Rate (headline speed) is NOT what you get in Peak-Time

DSL/FTTN is particularly prone to congestion problems, see the decade long Gungahlin Experiment, and they are very expensive to fix, meaning Network Operators are slow to correct.

Different ISP's will provide different sized 'pipes' back to their facility ("backhaul") and may have slower connections out to the Internet. Often,  not always, you get what you pay for... Expect cheaper ISP's to perform badly during Peak-Time. Some ISP's, e.g. Exetel, reduce costs elsewhere.

Peak-Time Congestion

Most of the Network Traffic is from just a few people: Telcos make their money from high-end, not the majority of users

The graph below shows 10% of customers using 50% of Download data volumes. With caveats, and volume is probably Upload + Download.

High-End consumers use, and pay for, most of the traffic

Volume used distribution for Mobile

"FTTC Speed Graph" from Original Ofcom source not located.

Original Ofcom PDF's:

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