Thomas L. Marzetta, Bell Labs Fellow
Nokia Bell Labs
Abstract: Edwin H. Armstrong invented wideband Frequency Modulation, arguably the first coded modulation scheme, in 1933 – fifteen years before the publication of Claude Shannon’s seminal paper, “A Mathematical Theory of Communication”. A purely analog wireless technology, wideband FM has been estimated to perform as little as 5 dB from the Shannon limit. Modern digital technology enables coded modulation that takes us almost all the way to the Shannon limit, and it has produced amazingly flexible wireless systems at low cost.
The ever increasing demand for greater spectral efficiency is being met by exploiting the spatial dimension through multiple antenna (MIMO: Multiple-Input, Multiple-Output) technology, and particularly in what is likely to be its ultimate embodiment, Massive MIMO. Massive MIMO utilizes a large number of individually controlled, physically small, low power antennas to create parallel virtual circuits between the base station and a multiplicity of single antenna users, with huge benefits in terms of spectral efficiency, uniformly great service to all users, and energy efficiency. While Massive MIMO owes a great debt to Shannon theory, in its simplest and most robust form it entails linear multiplexing and de-multiplexing based on direct measurements of the propagation channels. The earliest form of MIMO was proposed in 1919 by E. F. W. Alexanderson, a contemporary of Armstrong, to address the problem of scarce low-frequency (10 kilometer wavelength) spectrum, deemed at that time essential for transoceanic communication.