Robert Lucky: Adaptive equalization


While the modem that carries our DSL, FTTH or cable broadband connection may have continued to morph into what we now know as the broadband gateway, it likely would not be part of our broadband language if it weren't for Robert Lucky.

Robert Lucky

Lucky (Image source:

With both cable MSOs and telcos offering speeds of 25 to 300 Mbps to homes, it's hard to imagine that in the early 1960s the highest modem speeds one could send over a telephone lines was 2400 bits per second.

One of the issues that limited modems to 2400 bps speeds was intersymbol interference. This phenomenon meant that every dialed connection would have a different distorting effect on the series of pulses sent to communicate information. The end result was pulses would be smeared and detection errors would occur.

To overcome this issue, Lucky developed a method to adaptively undo the smearing effects with automatic adjustment of a variable filter, which used a tapped delay line with adjustable gains at each tap. Standing at about five feet high, the first adaptive equalizer in 1964, which included 13 adjustable gains, each set by eight relays, enabled 9600 bps data transmission.

Like other technology advancements, the adaptive equalizer migrated into various forms. Not long after Lucky invented adaptive equalization, transistor switches replaced the relays and then the equalizer was done via a special purpose integrated circuit. In today's modems, manufacturers build adaptive equalization into their products as a subroutine in the instruction program for an embedded microprocessor.

After a 31-year career at Bell Labs, Lucky spent 10 years at Bellcore, the Bell Telephone companies' research lab, serving as corporate VP overseeing research. Later, Bellcore was purchased by SAIC and renamed Telcordia. Lucky retired from the company in 2002.

Outside of his work at Bell Labs and Telcordia, Lucky has served in consulting roles at various engineering consortiums, universities and government agencies with a focus on technology and science issues. He served as editor of the Proceedings of the IEEE, chairman of the United States Air Force Scientific Advisory Board, and chairman of the Federal Communications Commission Technological Advisory Council. In addition, he has played an active role in both the National Academy of Engineering and served on a number of university advisory boards.