Understanding G.fast Technology: Features and Specifications

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This page explains the fundamental features of G.fast technology. It provides links comparing G.fast with VDSL and highlights the differences between the two. G.fast is a technology designed to coexist with VDSL2, adding enhanced capabilities for high-speed data communication over digital subscriber lines. It’s primarily intended for local loops shorter than 500 meters.

The specifications for G.fast are outlined in ITU-T G.9700 and ITU-T G.9701.

G.fast Technology Features

Here are some key features of G.fast technology:

  • Speed: Offers speeds ranging from 150 Mbps to 1 Gbps, depending on the loop length.
  • TDD Duplexing: Employs Time Division Duplexing (TDD), where both downstream (DS) and upstream (US) communications utilize the same frequency band but different time intervals for transmission. It supports low-power states, and the DS/US ratio can be easily adjusted.
  • Bandwidth: Supports a bandwidth of up to 100 MHz.
  • DMT Modulation: Uses Discrete Multi-Tone (DMT) modulation with 2048 subcarriers, a subcarrier spacing of 51.75 KHz, and allocates 12 bits per subcarrier.
  • PHY Layer Retransmission: The Physical (PHY) layer supports retransmission, improving resilience against impulse noise while maintaining low latency.
  • Vectoring: Supports vectoring, which helps to cancel far-end crosstalk.
  • Forward Error Correction (FEC): Supports FEC with trellis coding and Reed-Solomon (RS) coding, as defined in G.993.2 VDSL2, along with retransmission block interleaving as defined in G.998.4.
  • Network Time Transport: Provides transport of network time and time of the day.
  • Loop Length: Designed to operate over loop lengths of 250 meters using a 24 AWG (American Wire Gauge) pair of wires.
  • Broadband Forum Architectures: Supports TR-156 and TR-167 broadband forum architectures.

VDSL vs. G.fast: A Detailed Comparison

Explore the key differences between VDSL and G.fast, including frequency, data rates, distance, and duplexing methods, to understand their applications and limitations.

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g.fast
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2B1Q Line Coding: Advantages and Disadvantages

2B1Q Line Coding: Advantages and Disadvantages

Explore the benefits and drawbacks of 2B1Q line coding, including its applications, bandwidth efficiency, complexity, and synchronization challenges.

line coding
data communication
signal processing

ISDN, DSL, MMDS, LMDS: Technology Comparison

Explore the key differences between ISDN, DSL, MMDS, and LMDS technologies. Learn about data rates, capacity, cost, and installation time in this comparison.

data communication
broadband
dsl