/ˌdʒiː.fæst/
noun — "ultra-fast broadband over existing phone lines."
G.fast is a digital subscriber line (DSL) technology standard designed to deliver ultra-high-speed broadband over traditional copper telephone lines. It achieves downstream speeds up to 1 Gbps and upstream speeds up to 500 Mbps by leveraging higher frequency bands (up to 106 MHz or 212 MHz) and advanced signal processing techniques. G.fast is primarily intended for short loops, such as connections within buildings or from street cabinets to homes, bridging the gap between legacy DSL and fiber-optic deployments.
Technically, G.fast employs discrete multi-tone modulation (DMT), echo cancellation, and adaptive power control to maximize data throughput while minimizing crosstalk and interference. Its performance is highly dependent on loop length: shorter lines achieve higher speeds. G.fast can coexist with legacy DSL services on the same cable bundle, allowing operators to upgrade broadband without full fiber replacement.
Key characteristics of G.fast include:
- Ultra-high speed: supports gigabit-class broadband over copper lines.
- Short-loop optimization: ideal for last-meter or building distribution.
- Frequency division: uses higher frequencies than VDSL2 for increased throughput.
- Compatibility: interoperates with existing DSL infrastructure.
- Adaptive techniques: manages crosstalk, power, and noise dynamically for stable performance.
In practical workflows, telecom operators deploy G.fast to rapidly upgrade broadband in urban buildings or multi-dwelling units. Customer premises equipment (CPE) connects via copper lines to a distribution point unit (DPU), which interfaces with the fiber backhaul, providing high-speed Internet without full fiber deployment.
Conceptually, G.fast is like turbocharging an old car engine: it extracts maximum performance from existing infrastructure without replacing it entirely.
Intuition anchor: G.fast turns legacy copper lines into near-fiber gigabit connections for high-speed broadband access.