What is G.fast | G.fast technology features
This page explains basic features of G.fast technology. It mentions links which compares G.fast with VDSL and mentions difference between G.fast and VDSL.
G.fast is the technology which co-exists with VDSL2 and also adds more features for high speed data communication over digital subscriber lines. It is mainly targetted for local loops shorter than 500 meters. The specifications have been defined in ITU-T G.9700 and ITU-T G.9701.
Following are the features of G.fast technology:
➨Offers speed of 150Mbps to 1Gbps based on loop length.
➨It uses TDD duplexing method, in which both downstream (DS) and upstream (US) use same frequency but different time intervals for transmission. It supports low power states. It is easy to vary DS/US ratio. Refer TDD vs FDD➤.
➨ Supports bandwidth of 100 MHz.
➨ Supports DMT, 2048 subcarriers with subcarrier spacing of 51.75 KHz, 12 bits are allocated per subcarrier.
➨PHY layer supports re-transmission. Hence it improves robustness against impulsive noise while maintaining low latency.
➨ It supports vectoring which helps in far end cross talk cancellation.
➨ It supports FEC with trellis coding and RS coding as defined in G.993.2 VDSL2, along with retransmision block interleaving as defined in G.998.4.
➨It provides transport of network time and time of the day.
➨It is developed to operate over loop length of 250 meters on 24 AWG pair of wires.
➨Supports TR-156 and TR-167 broadband forum architectures.
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