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t) ISDN: innovation subscribers didn't need

t) ISDN: innovation subscribers didn't need

25.03.2019

 

In 1979, Bell Labs was designing 4.8-kbit/s modems and discussing progress towards an all-digital network (termed ISDN) delivering about 160 kbit/s to the subscribers. A junior team member named John Cioffi calculated, using Shannon's capacity formula, that speeds of 1.5 Mbits/s should be possible on a 4-mile twisted-pair line. In a contentious meeting, he audaciously made such a proposition. He was laughed at and embarrassed, and recalls being told:

"We're shooting for 144 to 192 kbit/s for ISDN. Your calculations are off; stop dreaming".

Even his own boss told him to

"Shut up and sit down".

160-kbit/s ISDN became a reality, and a commercial failure, earning the substitute acronym "Innovation Subscribers Didn't Need". Too slow to excite the consumers, ISDN did trigger the interest in really fast Digital Subscriber Lines (DSL). Meanwhile, by 1986, Cioffi had become a professor at Stanford University and was researching adaptive OFDM transmission, implemented using FFTs, for Asymmetric DSL (ADSL). Funded by a soon-to-be-bankrupt capital firm, he founded Amati Communications. In 1993, Bellcore organized an ADSL competition, the so-called Bellcore Olympics. Amati's OFDM system faced single-carrier designs from Bellcore, GTE and British Telecom. With 1/10th the budget, Amati's system ran four times faster (6 Mbits/s) and was selected as the US standard for ADSL. In 1998, Texas Instruments bought Amati for $395 Million. A Bellcore Olympic rerun took place in 2003 and was again won by OFDM, which became the standard for Very high-speed DSL (VDSL). DSL is featured in over 1/3 of the twisted pair lines worldwide. More details here.

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