Updated April, 2018
Dark Blue: 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 Blue: Smaller carriers in Germany, Norway, Finland, Japan
- Published: 15 August 2015 15 August 2015
Gigabit required to keep up with cable. It's in the standard, but until recently everyone assumed it would be delayed for lack of customer demand. But with gigabit cable coming close, AT&T is pressing for a gigabit over DSL. Adtran, a major supplier to AT&T and Deutsche Telekom, has proven that G.fast can easily exceed a gigabit downstream by bonding two lines. It's just a lab demonstration for now without a timetable for field trials.
G.fast vectoring and pre-coding require serious processing power to keep up with the high speeds. Bonding for even higher speeds is a challenge, but Adtran CTO Kevin Schneider doesn't see any obstacles that will prevent practical deployment.
- Published: 14 July 2015 14 July 2015
BT cuts back on G.fast speeds, deployment. 150-400 down is still a big improvement over BT's current network but it will typically be half the speed originally planned. BT was going to deliver 500-800 megabit G.fast to most of 4,000,000 distribution points on light poles, in basements and in very small dug in enclosures.
Instead, they would deploy to existing cabinets (10,000's of thousands,) avoiding the cost of running fiber so many places. That saves billions but reduces typical download speed from 400-700 megabits to 150-400 megabits. In either case, 5-15% or so of homes will run even slower.
- Published: 14 July 2015 14 July 2015
Not a gigabit but pretty darn good. AT&T, assured the DirecTV merger is going through, is about to go public with the long-planned upgrade of ~5M U-Verse homes to hundreds of megabits. They will take four years and reach about 15% of their homes. Gigabit gear won't be available for several years.
Randall Stephenson in 2004 told Wall Street AT&T was using fiber, not copper, for all “new builds,” although I believe it took a few more years. “New builds” are 1-2% of the network each year. That suggests four million to eight million homes are ready with FTTB.
With most of the construction already done, the upgrade will easily fit in AT&T reduced capital budget. I estimate G.fast will cost $75-250 per home passed. The cost over four years is is only a few % of annual capex and will be recovered in months from customer charges. It would be stupid not to upgrade and AT&T's top management isn't stupid.
The 400-700 megabit down speed of today's G.fast is confirmed by the early field trials. I previously reported that Swisscom, "Gets between 285 and 402 Mbps downstream and between 85 and 109 Mbps upstream. Results depend on copper cable length: on short copper cables (ca 24 meters) we were even able to reach 624 Mbps Downstream / 151 Mbps Upstream in field but without connected customers." Telekom Austria measured 536 megabits down and 116 up.
The chart below, from Alcatel, shows combined upstream and downstream speeds in early testing. Combined, the speeds up to 150 meters are 500-800 megabits. Subtracting 100 megabits for the upstream yields 400-700 megabits downstream, what I had estimated from a different data set.
- Published: 13 July 2015 13 July 2015
G.fast 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. G.fast 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 G.fast 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 G.fast 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.
- Published: 08 July 2015 08 July 2015
AT&T leading the efforts for an updated standard. Field tests of current G.fast gear have seen speeds of 400-700 megabits downstream, not the gigabit promised in early pr. 400-700 is plenty for almost everyone but the marketing department is worried. Cable is going to one and two gig (shared.) Google is just one of hundreds around the world offering a symmetric gig. The engineers have marching orders: get our G.fast speeds to a true gigabit ASAP!
Fortunately, the engineers are confident they can reach a gigabit.The ITU group already is working on a second appendix to the G.fast standard, aiming for 2016. A chip CTO tells me it will be easy to do more efficient coding (non-linear precoding) and transmit more bits for a given frequency (constellation.) Those two changes he believes enough to do the trick.
Trevor Linney of BT is running the most advanced tests of G.fast, connecting 4,000 homes. He reports "Our research shows that even more capacity can come from copper."
- Published: 01 July 2015 01 July 2015
Hoping to upgrade six million homes of NTT and KT of fiber to the basement. Details are scarce, but NTT, KT and their supplier Sumitomo are testing chips that offer the gigabit performance of G.fast (release below). They haven't said whether these are G.fast, vectored VDSL using G.fast high frequencies or a proprietary hybrid. They have engineers far along on all three possibilities. Their engineering is strong, headed by CTO Debu Pal, who studied under legendary Stanford Professor Tom Kailath. (pictured, with wife economist Anuradha Luther Maitra)
Japan and Korea's fiber deployments have been putting the West to shame for a decade. Since around 2005, NTT has been delivering 100 megabits from fiber to the basement. At the same time, Randall Stephenson of AT&T looked at me as if I were joking when I asked whether AT&T would do 100 megabits to Chicago highrises. "Why would anyone want more than 24 megabits," he asked me.
To Randall's credit, when he learned he was wrong he backed his technical people looking for the highest speeds practical within the budget. It hasn't been publicized, but the U-Verse team has done a remarkable job getting three HD channels in a network no one thought could handle the load. There are unsung heroes at AT&T.