G.fast
G.fast is an industry standard that was standardized by the ITU-T working group G.9700. It is about the fast connection of the Internet via copper twisted pairs, as offered by xDSL technologies. In terms of data rate, which is 500 Mbit/s, G.fast ranks between VDSL2 and passive optical networks( PON).
VDSL2 achieves 100 Mbit/s, PON technology 1 Gbit/s and more, depending on the version. G.fast can bridge distances of up to 250 meters and is a high-bit-rate connection technology to the digital subscriber line access multiplexers( DSLAM) of FTTx technologies such as FTTH (Home) or FTTB (Building). To ensure that the optical fiber ends as close as possible to the end user, G.fast uses FTTdp or FTTB. With both technologies, the distribution frame is closer to the end user.
With G.fast, bidirectional data rates of 500 Mbit/s can be achieved. G.fast uses a transmission frequency of 106 MHz in the first development phase, and 212 MHz in the second. In contrast to VDSL2, 12 bits per subchannel are transmitted instead of the 15 bits in VDSL. Since the process is extremely sensitive to crosstalk, vectoring is mandatory with G.fast to compensate for interference. During transmission, the signals are multiplexed in OFDM multiplex and transmitted in time division duplex( TDD) one after the other in the transmit and receive directions.
With XG-FAST, there is already a further development of G.fast, with which data rates of 1 Gbit/s in bidirectional operation and 10 Gbit/s over two copper pairs can be achieved.