Wurth Electronics Midcom Transformers in G.FAST Modems

G.FAST is the latest approved broadband DSL standard which is poised to bring fiber-like internet speeds to consumer residences at an affordable cost to the masses. To learn the ins and outs of this latest technology, we interviewed Swaroop Vaidyanath. Here is what Mr. Vaidyanath had to share.

Figure 1: Difference between FTTH, VPLUS, VDSL2 and G.FAST

What is G.FAST?

G.FAST is the latest broadband standard ratified by International Telecommunications Union (ITU), an agency of the United Nations. This technology can deliver fiber-like broadband speeds up to 1 Gbit/sec over existing twisted copper telephone wires to a residence.

Ok, could you briefly explain the G.FAST solution from the Central Office side (Telephone Company) and from the residence side?

Absolutely! As shown in Fig 1, fiber is used as the medium to send and receive signals from the Central Office to the Distribution Point Unit or DPU. The internet service provider ships a CPE (Customer Premises Equipment) box to the internet user at the residence. The user plugs this CPE box into the wall and connects to the internet using the telephone jack.

The other end of the telephone line is connected to a DPU sitting 200 – 300 meters outside the house. The DPU converts the fiber optic signals to phone wire signals and vice versa. The size of the DPU is usually about 18 inches wide and 9 inches tall. It can be placed on a pole or on the ground. The DPU is powered by the CPE.

This reverse powering technology approach is advantageous to Internet Service Providers as it saves them thousands of dollars in installation costs. The cost of powering the DPU from the consumer is about 8 cents per month with G.FAST’s low power consumption.

Great! How is G.FAST different from VDSL or VPLUS?

There are a number of differences:

  • A. The bandwidth spectrum of G.FAST ranges from 2 MHz to 106 MHz. The bandwidth of VDSL and VPLUS ranges from 2 MHz to 35 MHz. That is over 3X more bandwidth than VDSL and VPLUS. According to Shannon’s Law, the maximum achievable bit rate over a transmission medium is function of frequency and signal to noise ratio.

    C = B*log2(1+S/N)

    Let’s consider Bandwidth = 106Mhz, signal to noise ratio = 640 or 28dB.

    Then, C = 106M * Log2( 641) = 987Mbps. Even while considering the variations in signal-to-noise ratios of cables and cable lengths, the higher bandwidth of G.FAST technology plays a key role in achieving higher speeds.
  • G.FAST uses time-division duplexing (TDD), as opposed to ADSL2 and VDSL2, which use frequency-division duplexing. The advantage of using TDD is that the internet service providers can now use software to control the ratio of bandwidth between upstream and downstream that reaches the subscribers. Of course, signals cannot be 100% downstream as this would block the acknowledgement packets required for the internet. Nevertheless, this flexibility to switch the upstream / downstream ratios cannot be done with VDSL.
  • The CPE powers the DPU using a reverse power feeding mechanism. As G.FAST uses very little power, this is a win-win situation for both consumers and service providers.

Why is so much of bandwidth needed in the first place?

Has anybody complained about too much internet speed?

As you know, internet speeds have only been increasing for the past 15 years. This is evidenced by Moore’s Law, as computers have been doubling their processing power every 18 months, making UHDTV, 3DTV’s , video conferencing and virtual reality games possible. Homes are being filled with bandwidth-hungry applications in the name of home automation and these consume lot of data.

Nielson’s Law states that users’ internet bandwidth grows by 50% per year and this has been true until now. According to Cisco, global mobile data traffic will increase nearly eightfold between 2015 and 2020 (30.6 Exabytes per month). Ericsson predicts that there will be 28 billion devices connected to the internet in 2021. These are the numbers driving the Internet of Things industry and Telco industry, where every “thing” around the home has a sensor, connects to Wi-Fi and sends & receives data from mobile devices, tablets, smart watches etc. Hence, G.FAST has the potential to become an affordable ultra-broadband solution for the masses and deliver the promises of fiber-based solutions at a fraction of the cost.

When will G.FAST be available for customers?

The first chipsets were introduced in October 2014. The launch of commercial deployments and operations is expected in 2016 and 2017.

What can you tell us about the custom transformers that go into G.FAST modems?

The data isolation transformer is an important component for data transmission applications. A good data transformer improves the quality of the signal and maximum transmission distance, in addition to providing isolation. Wurth Electronics Midcom has customized tiny toroidal packages to be used with Sckipio’s G.FAST chipsets SCK1001 and SCK1002 to deliver ultra-broadband internet access to consumers. These toroidal packages have low leakage inductances (max of 300nH) and meet a dielectric of 1875VAC per sec. These toroidal packages have a low profile height and a small footprint (3.68 mm height x 9.02 mm width x 6.73mm length). We also have G.FAST transformers tailored for Broadcom chipsets: BCM63138, BCM659xx and BCM963138. These transformers are customized to provide very good longitudinal balance, excellent total harmonic distortion, meet supplementary insulation and comply with UL and IEC safety standards.

Wurth Electronics Midcom is a global leader in design and manufacturing of custom transformers used in the telecom industry. We actively partner with the major semiconductor companies (Sckipio, Broadcom, Qualcomm, Intel etc.) to develop xDSL transformers, with G.FAST transformers being the latest technology. For more information, please visit our website.

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