Bell Labs boasts several pioneers in modulation, the process of varying one or more properties of a waveform in order to more efficiently transmit information.
Bell Labs research on modulation dates back to the work of Harry Nyquist on sampling theory in 1928 and later to Claude Shannon, resulting in the Nyquist-Shannon sampling theorem. In the mid-1940s, John Pierce, Claude Shannon and Bernard Oliver invented pulse code modulation. In 1965, John Tukey invented the Fast Fourier Transform (FFT), and in 1971, Steven Weinstein and Paul Ebert invented Orthogonal Frequency Division Multiplexing (OFDM) in its modern form.
In the early 1990s, James Mazo exploited modulation techniques to design the 56k modem, and in 1995, Gerard Foschini and I. Emre Telatar introduced multiple input multiple output (MIMO) communications. In the early 2000s, several Bell Labs researchers, including Andrew Chraplyvy, Xiang Liu, and Alan Gnauck introduced differential phase shift keying as an alternative to on-off keying for long-haul optical communication systems.
Today, researchers are exploring advanced MIMO modulation techniques with applications for wireless, optical and copper access systems. For example, Peter Winzer and several other Bell Labs colleagues are bringing MIMO techniques to bear in optical fiber communication through space-division multiplexing. This new technology exploits multiple spatial degrees of freedom in multi-mode and multi-core fiber and overcomes the Non-Linear Shannon Limit identified by a team led by Rene-Jean Essiambre.
Optical SDM promises efficient options for moving beyond the Non-Linear Shannon Limit rapidly being approached by current backbone modulation technologies.
Jochen Maes, Carl Nuzman, Mamoun Guenach, Adriaan van Wijngaarden and several other colleagues are devising MIMO beamforming techniques to suppress crosstalk interference in Digital Subscriber Line (DSL) systems. The goal is to achieve gigabit DSL communication over the existing copper loop plant by contriving non-linear precoding techniques that enhance spectral efficiency in high-crosstalk regimes.
Thomas Marzetta has been exploring the use of distributed processing over large antenna arrays to achieve extremely high spectral and energy efficiencies, and is currently leading research directed towards the practical realization of such Large Scale Antenna Systems (LSAS).