Early online internet access was slow and inefficient through plain-old telephone lines. That is, until Digital Subscriber Line, or DSL, the first broadband data-transmission technology. Forms of DSL now connect nearly 75 percent of global internet homes at faster per-customer speeds than cable broadband, thanks to Dr. John Cioffi, founder of DSL modem maker ASSIA and known as the "father of DSL."
Cioffi was born on November 7, 1956, in Park Forest, just south of Chicago. Cioffi's father, John, worked in insurance, while his mother, Lorraine, was a stay-at-home mom. Cioffi got a taste of his future on a family trip to 1964's New York World's Fair, where a demonstration of AT&T's videophone fascinated him.
After graduating in 1978 as the valedictorian of University of Illinois’ engineering school, Bell Labs hired him and paid for his graduate work at Stanford University.
Cioffi spent six years shuttling cross country between Bell Labs' Holmdel, NJ, facilities and Stanford, where he earned both his master's and PhD in electrical engineering. Motivated to improve on AT&T's videophone, Cioffi worked at both institutions to help quadruple the speed of 2400 bits per second (bps) early voice-band modems to the then adaptive echo-cancelled full-duplex modems at speeds of 9600 bps and later higher. He also helped Bell Labs solve echo-cancelation problems for the then-contemplated Integrated Services Digital Network (ISDN) – the beginnings of DSL.
In 1984, Cioffi joined IBM's San Jose lab to work to increase hard drive bit density using AI algorithms. In early 1986, Stanford made Cioffi an electrical engineering assistant professor, where he continued working on DSL.
The independent companies that were created after Bell Systems broke up – also known as Baby Bells – also continued work on DSL. Cioffi proposed a significant architecture change: they pursed a “single-carrier” method, which was limited by the lack of AI. Cioffi's proposed smarter system learned each phone line's specific disturbances, and then applied machine learning accordingly to adjust the transmission format.
Cioffi and PhD candidate Peter Chow's proposed method was called Discrete Multi-Tone (DMT) modulation and the specific machine-learning algorithm used "bit-swapping." DMT divides the phone line channel into separate subcarriers that use bit-swapping to dynamically tune to optimize speed. DMT pushed data speeds to 1.5 megabits per second (Mbps) – "good enough" for video. In 1991, Cioffi correspondingly co-founded Amati Communications.
In January 1993, a DSL "Olympics" was held in Miami to determine a DSL standard. Amati's DMT-enabled Prelude ADSL modem was able to transmit faster than 6 Mbps, four times the speeds of other proposed designs from AT&T/Lucent, Bellcore and Broadcom, and was unanimously agreed to by the 200-plus voters. On March 10, 1993, Cioffi's DSL technology was officially declared the U.S. standard by the American National Standards Institute (ANSI), followed by the European Telecommunications Standards Institute (ETSI) a few months later, and International Telecommunication Union (ITU) two years later. A form of bit-swapping developed by Cioffi and former student (and future ASSIA employee) Haleema Mehmood also is used in DOCSIS 3.1 cable modems.
DMT technology also led to the development of Coded-OFDM transmission technology used in 4G LTE, 5G NR, and nearly all forms of digital FM broadcast, digital video broadcasting and Wi-Fi.
In 1995, Amati successfully went public and was bought by Texas Instruments in 1997. Cioffi, who had returned to Stanford, and a new group of PhD students including future-ASSIA employees Dr. Medhi Mohseni and Dr. Chan Soo Hwang, developed Dynamic Spectrum Management (DSM) and "vectored DSLs," which increased DSL speeds to 150 Mbps. These vectored methods form the basis for Massive MIMO LTE and Multi-User MIMO (MU-MIMO) Wi-Fi systems. In 2017, Cioffi proposed the world's first Terabit DSL systems with Drs. Ken Kerpez and Ioannis Kanellakopoulos.
From 2003 to 2004, Cioffi, his wife Assia and former students Dr. Wonjong Rhee and Iker Almandoz founded ASSIA (Adaptive-Spectrum-and-SIgnal-Alignment), later joined by former students Drs. Philip Bednarz and Mohseni, which serves 40 telcos globally with 150+ million DSL/wireless subscribers.
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