DSL pioneer shoots for terabit future

Article By : Rick Merritt

Terabit DSL may be used to mitigate the need for running fibre to the home as well as to carry traffic from 5G cellular base stations, says John Cioffi.

A pioneer of digital subscriber lines has unveiled a novel upgrade that could deliver terabit data rates in the future.

In a keynote at the G.fast Summit in Paris, John Cioffi described the ideas behind what he calls Terabit DSL (TDSL). They include carrying 50-600GHz wireless signals through the tiny spaces between individual twisted pairs or the cables that bundle a hundred of them.

“We are shooting for a terabit/second over 100 metres, 100Gbits/s at 300 metres and 10Gbits/s at 500 metres—all those are 200 to 1,000 times better than traditional DSLs,” said Cioffi, whose research at Stanford in the 1980s led phone companies to embrace DSL for broadband.

“Those numbers could be off 10-25%, but even if they are off by 10x, it’s still a substantial improvement—there’s a lot of opportunity here,” said Cioffi who is now a professor emeritus at Stanford and chairman of Adaptive Spectrum and Signal Alignment (ASSIA), a developer of DSL software.

The technology could be used to mitigate the need for running fibre to the home as well as to carry traffic from 5G cellular base stations. Cioffi has created computer models he and others believe prove the concept that could take at least two to three years to commercialise, he estimated.

Carriers charge as much as ₹2.72 lakh ($4,000) to pull fibre to an individual home, a cost that could come down to as little as ₹13,598.97 ($200) for a shared fibre/TDSL link, Cioffi said. Others estimate it could cost ₹28.57 lakh crore (€400 billion) to deploy 5G cellular throughout Europe, a price tag that could be reduced to tens of billions using TDSL backhaul, he added.

“The largest cost in 5G is not the wireless part, it’s the wires behind it,” said Cioffi, who posted online slides from his TDSL talk.

TDSL_antenna_01 (cr)
Figure 1: TDSL sends 50-600GHz wireless signals in gaps between copper pairs. (Source: John Cioffi)

The concepts in TDSL had their start two years ago when Cioffi was reviewing 60GHz MIMO work at a wireless lab at NYU led by Ted Rappaport. “I started thinking whether there was an analog for this work in cables, I talked to Ted and he encouraged me,” Cioffi said.

That talk led to discussions with other academics and transmission specialists at Apple and Huawei. About a dozen colleagues have reviewed Cioffi’s work so far.

"TDSL is a breakthrough in the pursuit of ultra high speed over copper. The combination of millimetre waveguides and vectoring signal processing puts new regimes of physics together with advances in mathematics—the business implications of this technological breakthrough will be tremendous,” said Mung Chiang, a professor of electrical engineering at Princeton.

"Surface wave propagation is an exciting new transmission mode that could be harnessed for massively broadband communication. I wouldn't bet against John Cioffi, he's the pioneer who brought us DSL,” said Ted Rappaport.

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