John Cioffi, father of DSL technology

John Cioffi


John Cioffi's ascension to become the "father of DSL" is the culmination of a 30-plus year journey that began in the late 1970s when he was working as a modem designer at Bell Laboratories--a time when the former AT&T's (NYSE: T) Bell System was still well in place.

Simultaneously, Cioffi laid the foundation for his alternative academic/entreprenuerial career, attending Stanford University where he would earn his Ph.D in 1984.

During his tenure at Bell Labs, Cioffi's colleagues were working on ways to digitize the existing copper pair network via what was then called the Integrated Digital Services Network (ISDN) to support video over the copper network. However, the reality was that ISDN BRI could only support two voice channels or a single 128 Kbps data channel, hardly enough to support quality video.   

It was this dilemma to get higher data rates on existing copper pairs that drove him to begin conducting research on different modulation schemes to achieve that goal.

Following a brief stint at IBM (NYSE: IBM) where he was a hard disk drive read channel researcher, Cioffi joined Stanford University to begin an academic career as an assistant professor in 1986. Much of his work with his students at Stanford centered on multicarrier discrete multitone modulation (DMT), an approach that became the common modulation technique in DSL technology.

Cioffi said at that time when he was working on DMT "we achieved data rates for good video," or about 1.5 Mbps or higher from the network to the end-user.

Only five years into his teaching career at Stanford, Cioffi wanted to apply what he and his students uncovered in their research by founding Amati Communications.

One of the biggest achievements Amati made was the development of the Prelude DSL modem that could transmit over 6 Mbps over 9,000 feet of a copper telephone line. Interestingly, the Amati modem would beat out modems from AT&T and Bellcore that used single-carrier QAM and CAP modulation formats during the 1993 "Bellcore ADSL Olympics."

Once again in 1993 Cioffi returned to his teaching post at Stanford while remaining as involved at Amati as an officer and director until it was acquired by Texas Instruments (NYSE: TXN) in 1998.

It was during this second professor stint at Stanford where Cioffi and his students would begin research on how Dynamic Spectrum Management techniques could be applied to mitigate noise issues on a DSL line and increase data rates.

And just like initial Stanford research to develop DMT helped create Amati, his work on DMT drove him to found Adaptive Spectrum and Signal Alignment, Inc. (ASSIA) in 2003. Already, ASSIA's DSM products are being used by a number of US and European tier one service providers, including AT&T (NYSE: T), CenturyLink (NYSE: CTL) and Telefonica (NYSE: TEF).

Currently, Cioffi continues to live his dual life as an academic and business owner serving as the Chairman and CEO of ASSIA and as the as the Hitachi Professor Emeritus of Engineering at Stanford University.