Gfast map

gfast map copy

 

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

Light Blue: Incumbent likely:  France, Germany, Italy

english garden80+% of Brits live in single family houses, far fewer than several other European countries. BT and AT&T have natural small nodes, making 8-16 port boxes appropriate. G.fast has a profound problem in other territories, where far more people live in apartment buildings which cannot today be served with G.fast.

    I first thought apartment buildings could be served by simply using multiple boxes At BBWF several told me the interference issues are insurmountable without vectoring. Vectoring 48 lines is impractical with today's chips. They don't have enough processing power and if they did there would be a heat problem.

    BT has about ~4M "distribution points" on poles and underground. There's an average of ~8 customers connected, and only a few have more than 16 drops.

The typical distance from the drop to the customer is ~35 meters. Like any DSL deployment in the real world, some customers will be screwed because they happen to be far from the box. 

    Trevor Linney of BT, working with Huawei, achieved speeds of 500-700 megabits in a test with Huawei. That's combined upstream and downstream. Distances were 19 metres to 66 metres.Trevor Linney has been a leader in G.fast development, making BT a pioneer. 

    Sckipio and Huawei/HiSilicon told me their design can be extended to 48 ports but gave no indication that will happen soon. Ikanos for two years has worked toward "full-node vectoring" so may have larger capacities. Ikanos chips aren't out the door yet. 

    BT speaks of 1 gigabit from G.fast. So does the ITU, Sckipio and U.S. FCC Chairman Wheeler. That's mostly marketing hype. They combine upstream and downstream speeds for a total. For two decades, nearly everyone has characterized systems by the downstream speed alone. Nearly all real deployments share binders with VDSL or other services. The spectrum they use, typically 23 MHz, is blocked from the G.fast DSLAM ("noted".) Other services, including radio, also require notching to prevent interference.

    Alcatel's Paul Spruyt and others are more realistic, speaking of speeds of 600-800 megabits (combined.)

     

     

    

 

     

 BT results

BT test