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Published on is the hot new ultra-broadband standard from the Broadband Forum and the ITU. How does it compare with the previous standard, VDSL? Check out the technical details here.

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  1. 1. VDSL vs. G.FAST Technology comparison Parameter VDSL G.FAST Frequency Range Up to 30MHz (30a) 2-106MHz, 2-212MHz (future) Max Rate Up to 250Mbps (30a) and 150Mbps (17a) for short loops, real-world is 30-80Mbps 1Gbps over short loops, exceeding 500 Mbps over real 100m lines Modulation OFDM OFDM Number of carriers 4K 2K (for 106MHz profile) Multiplexing scheme FDD TDD, synchronized among the different copper pairs Symbol time ~250 μsec (17MHz profile) ~20 μsec Vectoring Via G.993.5 Supported, with adaptations needed for higher frequency Tx power Varies by profile, 14.5dBm 4dBm FEC RS + Trellis code RS + Trellis code Confidential | Sckipio Dec 12, 2014 1
  2. 2. VDSL vs. G.FAST System comparison Parameter VDSL G.FAST Downstream/Upstream ratio Fixed Configurable: 90:10 to 30:70 Customer self-install Questionable. i.e. rates become marginally low Yes xDSL Spectral compatibility Issues with 17M/30M mix Issues with CAB/DP Mix Yes, fresh start with new frequency band Retrain time Very long (30-90 second range) Very short – few seconds Rate adaptation Very slow, 128 carriers at a time, SOS not robust Very fast, quick and robust adaptation – within few msec Low power mechanisms Under definition, expected savings up to 50%, very slow wake up time Specified from day one, discontinuous operation, scales with traffic rate Confidential | Sckipio Dec 12, 2014 2