Terabit DSL could solve the last mile problem with far less cost

John Cioffi described Terabit DSL (TDSL). It include carrying 50-600 GHz 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 meters, 100 Gbits/s at 300 meters and 10 Gbits/s at 500 meters - 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 percent, 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 Inc. (ASSIA), a developer of DSL software.

Carriers charge as much as $4,000 to pull fiber to an individual home, a cost that could come down to as little as $200 for a shared fiber/TDSL link, Cioffi said. Others estimate it could cost 400 billion euros 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 Cioff.

"Fiber-like speeds of 10 - 1000's of gigabits/second (Gbps) are possible by using the previously unexploited waveguide modes of current copper infrastructure. Waveguide-mode use is similar to use of millimeter-wave transmissions in advanced wireless and 5G. Waveguides can enable use of frequencies above 100 GHz for extraordinary speeds.

The challenge was to develop practical ways to use higher frequencies over wires. Working with my ASSIA colleagues Dr. Chan Soo Hwang, Dr. Ken Kerpez, and Dr. Ioannis Kanellakopoulos, we found a solution."