G.fast

G.fast is an ITU-T standard of DSL technology and is considered the successor standard to VDSL2 . The transfer process is based, like VDSL2 vectoring and Supervectoring on vectoring . G.fast promises data transmission rates of up to 1 Gbit / s (in total in the send and receive direction) over existing telephony copper cables and is only suitable for short cable distances of up to 250 m due to the high frequencies. G.fast is therefore, at least currently, still an alternative to FTTH and is designed for FTTB and FTTdp networks. The ITU-T specifications G.9700 and G.9701 describe G.fast.

G. almost is an acronym for " f ast a ccess to s ubscriber t erminals " (German: Fast access to customer premises).

Spectral ranges of G.fast and VDSL2 plotted against the bandwidth efficiency

General

Alcatel Lucent announced in mid-2013 that it had achieved 1.1 Gbit / s under laboratory conditions on a single, 70 m long copper pair . 800 Mbit / s was still achieved over 100 m. Huawei states that it has been able to transmit data rates in the same framework since the end of 2011.

Since G.fast is very susceptible to crosstalk , vectoring must be used for efficient use under real conditions in order to compensate for interference.

In a first step, frequencies up to 106 MHz and later 212 MHz are used for transmission, but in contrast to VDSL2, the number of bits per sub-channel (carrier) is limited to 12 (with VDSL 15 bits). Due to the high frequencies and the resulting signal attenuation , G.fast can only be used for short cable distances of up to 250 m. It is therefore assumed today that mixed operation, together with other xDSL technologies such as VDSL2, will be sought in the future.

ITU standardized G.fast on December 5, 2014. Permanently operated installations were expected around the end of 2015.

Based on ATU-R (ADSL Transceiver Unit-Remote), VTU-R and STU-R as a designation for a modem on the ADSL, VDSL or SHDSL connection, G.fast uses the term FTU-R. The DSLAM, also known as xTU-C (Transceiver Unit-Central Office), is referred to as DPU (Distribution Point Unit) at G.fast. Unlike ADSL or VDSL (ATU-C or VTU-C), it is often much smaller and is not necessarily located in the central office, but rather distributed in the street or in the house .

application

In Switzerland, Swisscom has been operating G.fast-capable equipment in an FTTdp pilot test since June 2012 .

G.fast-capable hardware has been expanded in selected regions of Switzerland since the end of 2013. Also, A1 Telekom Austria is testing the new technology in its network, reaching in tests 1 Gbit / s over 100 meters of copper cable, as they were installed in the telephone network.

Since October 2014 A1 has had its first commercial customer G.fast in Austria. In Germany, Deutsche Telekom wants to test the technology in a field trial in 2014 and thus also achieve up to 500 Mbit / s over the nationwide copper cable network.

Chunghwa Telecom will launch the first commercial G.fast network in mass rollout in Taiwan from October 2015. Tests have been carried out at Swisscom end customers under real conditions since May 2015.

In 2016, Swisscom was the first European telecommunications provider to launch G.fast in general for end customers in new development areas.

In May 2017, M-net Telekommunikations GmbH and NetCologne Gesellschaft für Telekommunikation mbH were the first German network operators to start their G.fast network in Munich and Cologne, respectively.

technology

Modulation and duplex method

OFDM is used as the type of modulation. The transmission and reception channels (upstream and downstream) are separated using the TDD method. This means that it is only sent alternately in one direction at short intervals. In contrast to VDSL or ADSL, which work with FDD and thus the transmission and reception channels each have their own frequency band, it is possible to individually adapt the ratio of the upstream / downstream data rates.

Supportive procedures

By using much higher frequencies than z. B. With VDSL, the crosstalk also increases massively. This can be largely compensated for by means of vectoring, but new, better algorithms are required for this. In addition, higher frequencies also mean more calculations per second for the vectoring calculations in the DSLAM . Its computing power must also increase exponentially as the number of DSL lines on the DSLAM increases.

As with VDSL2, Forward Error Correction and Impulse Noise Protection are also used for error correction.

Technical challenges

G.fast uses frequencies up to 212 MHz. The VHF radio range (87.5 ... 108 MHz) lies in the middle of this G.fast spectrum. So that the subscriber connection lines do not act like antennas for a long time and thus interfere with a radio device, start and stop frequencies as well as the power distribution in the transmission spectrum can be configured with G.fast (PSD shaping and notching ).

As with vectoring, which is fundamentally important for the operation of G.fast, there are some challenging problems for telecommunications companies. So z. For example, the CPE on the end customer side also supports this standard and, ideally, a DSLAM should serve all connections in the same cable bundle so that it has control over the crosstalk in the entire network.

Individual evidence

1. ↑ ITU Readies New 1Gbit / s Broadband Standard , ITU-T Newsroom
2. ↑ ITU-T Work item , ITU-T Work programs
3. ↑ The Numbers are in: Vectoring 2.0 Makes G.fast Faster ( Memento of the original from August 2, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , Alcatel Lucent TECHzine 
4. ↑ G.fast: Moving Copper Access into the Gigabit Era , Huawei Carrier Network (Solutions)
5. ↑ itu.int
6. ↑ DSL successor with 1 GBit / s is standardized , golem.de
7. ↑ G.fast for FTTdp , p. 24
8. ↑ G.fast , Assia-Inc.com
9. ↑ Huawei delivers Giga DSL prototypes to Swisscom , it-markt.ch
10. ↑ Swisscom selects Huawei as the supplier for the FTTS expansion ( Memento of the original from October 24, 2017 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , Swisscom media releases 
11. ↑ G.fast at A1: For the first time in the world, data rates above 1 Gbit / s in the existing copper line network . In: a1.net . a1.net A1 Telekom Austria AG. July 2, 2013. Retrieved February 15, 2014.
12. ↑ telekomaustria.com G.fast from Alcatel-Lucent enables A1 unimagined bandwidths
13. ↑ More speed in copper lines: Telekom wants to test G.fast technology this year - teltarif.de News . In: teltarif.de . teltarif.de Onlineverlag GmbH. February 15, 2014. Archived from the original on February 15, 2014. Retrieved on February 15, 2014.
14. ↑ telecomstechnews.com Alcatel-Lucent helps Chunghwa Telecom with ultra- broadband expansion.
15. ↑ Swisscom offers bandwidths of up to 500 Mbit / s , internetoffer.de
16. ↑ swisscom.ch press release Swisscom.
17. ↑ M-net and Huawei cooperate in the construction of the first FTTB / G.fast network in Germany. August 1, 2017. Retrieved August 17, 2017 . 
18. ↑ NetCologne Gesellschaft für Telekommunikation mbH: G.fast technology: NetCologne and ZTE break new speed record at Anga Com! Retrieved February 16, 2018 . 
19. ↑ Frank van der Putten: Overview of G.fast: Summary overview and timeline. (PDF) (No longer available online.) May 20, 2014, p. 19 , archived from the original on October 15, 2014 ; Retrieved October 9, 2014 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.