spacer 2Telebyte Gfast Testing Guide 320

gfast map nov

Dark Green: Firm commitments from incumbent: BT (10M), Belgacom, Australian NBN, Swisscom,  Austria, Bezeq Israel, Chunghwa Taiwan, Telus Canada, Telekom South Africa, SK Korea, (U.S.) AT&T, Century, Frontier, Windstream, Belgium, Omantel

Mid Pink: Smaller carriers in Germany, Norway, Finland, Japan

Light Green: Incumbent likely:  France, Germany, Italy uses 106 MHz compared to only 1 MHz for ADSL. More MHz means more capacity but only works over very short loops. The actual ITU standard is 300 pages with dozens (?hundreds) of features which have relatively little impact on the speed. Traditional VDSL used 17 MHz for speeds around 100 megabits. can use 106 MHz for speeds typically 400-700 down, 100 megabits up. (The "gigabit" is pr fluff today although upgrades to actually get a gigabit are in the works.)

The distance limit: High frequencies used by don't go very far in ordinary telco twisted pair cables. It was designed for 50-150 meters and speeds drop rapidly after that. British Telecom and AT&T engineers told the ITU standards group that short reach was fine and nodes would be 8-16 homes. That set the standard. 

G,halffast When British Telecom realized the cost of running fiber to 4M "distribution points/curbs" they sent the entire plan back to the drawing board. The maximum wire length was increased from 250 meters to 500 meters. Chip makers are scrambling to modify their chips to the new demand. Many English homes will get speeds of 100-400 down, not close to the promised gigabit but pretty darn good.

How many homes get 400-700 megabits down and how many don't get 100 megabits depends on how much money BT decides to spend on the network. The odds are BT will keep costs down, leaving many customers with far lower speeds than the pr is suggesting. AT&T customers will probably get the 400-700 megabits down. Most of their deployment will be fiber to the basement and to an apartment. That's often less than 100 meters and the high speeds are possible. From now to at least 2019, AT&T plans to "fiber" ~15% of their homes. Most will be apartments.

"The Brits love their gardens," I'm told. They have very few apartment buildings, so BT can't use AT&T's strategy. BT is also planning to do far more than AT&T's 15%, going quickly to "nearly all the country." They will mostly have to deal with private homes. 

Yes, the gigabit is possible in a few years. Rami Verbin of Sckipio is confident a gigabit is practical. Based on testing the current generation of chips, he can increase the "constellation," loading more bits per hertz. "Non-linear precoding" should add more bandwidth as well, making the system more efficient. It increases the complexity of the chip but Moore's Law is bringing down the cost. Paul Spruyt of Alcatel has a similar expectation and these changes are being actively considered in standards. 

There's lots more to know if you're building a network, but this should get the non-expert started.


The Site for gfast 230 News

I’m still working through remarkable presentations from the Broadband Forum events. Michael Weissman, Bernd Hesse and team did a remarkable job choosing the speakers.

Deutsche Telecom: 35b Supervectoring Delayed to 2019
Broadcom is now over 3 years late. DT briefed German reporters after their financial call and revealed 35b was now delayed until 2019. 35b should deliver 200+ meg downloads 500-600 meters, a crucial tool for DT, which is losing share to cable. Cable now covers about 70% of Germany and is expanding. DT now only offers 50-100 megabit DSL while cable is often 400 megabits, going to a gigabit. 

The problem is software; the hardware is shipping and supposedly will work. DT says 35b is not ready to turn on. Broadcom in 2015 said 35b was in "production" in the press release below. Alcatel in early 2016 said to expect complete systems very soon. "35g is very similar to 17a so there should be little delay."

Broadcom's problems are leading major telcos and vendors to have a plan B, using Sckipio DT itself is planning extensive deployments in 2019, mostly in apartment buildings.

Gigabit 100 Meters - Unless the Wires are Lousy
Speeds are fine, "Unless there's a line problem." I've been reporting for three years that ~10% of lines have problems. In the chart by Rami Verbin of Sckipio, he finds goes ~130 meters on good lines. Poor lines have about half the reach. 

His chart roughly matches the reports from Swisscom, Belgacom, and England for both & vectored DSL. The 10% with problems can cause the majority of the line-related complaints to support. The angry customers drive up cost.

Rami's solution to reach the gigabit is bonding, supported on the Sckipio chips. Verbin made some additional points:

  • 4 gigabits is possible by bonding two decent 2 gigabit lines.
  • Even in a service from remote cabinets, ~25% are close enough to get a full gigabit."
  • cDTA and iDTA are practical ways to deliver much higher upstream by switching some bandwidth from downstream to upstream only when needed.
  • 35B will probably be similar but Deutsche Telecom doesn't expect to deploy until 2019.

AT&T Wants Coax 2-5 Gigabit Very Soon.
AT&T faces intense competition from cable, talking about 10 gigabits in both directions. (Cable will only be 1 gig down, ~100 meg up, until ~2021.) AT&T wants something to brag about as well.

AT&T gained millions of lines of coax as part of the DirecTV deal. Alcatel and Huawei are leading the development of G.mgfast. That uses 424 MHz, full duplex, to achieve ~2.5 gigabits in both directions. The reach on telco twisted pair is only about 30 meters. On coax, those speeds can probably extend far enough to service most apartment buildings. Using 848 MHz, speeds can reach 5 gigabits. The ITU standards group has been aiming for 2019-2020 for G.mgfast, too slow for AT&T's marketers. David Titus wants a high-speed standard for coax "early in 2018." He believes that is "doable."

Read more ...