For some reason, the other day I remembered a presentation by Rajiv Laroia about 2 years ago. Rajiv is know to be very successful in applying DSP technology to solve tough communications problems. The presentation was about one of his inventions: Fhash-OFDM, one of the preeminent OFDMA technologies. The presentation covered the many advantages of this technology when applied to broadband wireless communication. Towards the end, I was convinced of the advantages of OFDM but I was wondering why an apparently simple technology hadn’t made it to the market earlier. The answer was that although the theory behind the system was known for a while, the technology to implement it hasn’t be ready until recently.

This got me thinking on how DSP has historically evolved over time and, specifically, the history of the FFT, the technology at the core of OFDM. It turns out that a little search on the web resulted in some interesting sites, such as the expected Wikipedia entry, another Wikipedia entry for the Cooley-Tukey FFT algorithm, one in the CS department at Dartmouth College, and one in the department of mechanical engineering at Oregon State University. All of them resulted in some interesting reading that helps to realize how a mathematical and engineering problem evolve over time into becoming an important tool of countless products. Also, for my personal train of thought, I was surprised to learn that the FFT can be traced back to Carl Friedrich Gauss some 180 years before the first DSPs appeared on the market. Nevertheless, Gauss’ contribution went almost unnoticed (not surprisingly , since it was published posthumously and in neo-Latin…) and was rediscovered in 1965 by Cooley and Tukey, about 15 years before the first DSPs appeared on the market. So, the timeline for the OFDM goes by the development of the FFT in 1865, following by the first DSPs in the late 70’s and early 80’s. After this, it took around 20 more years for the DSPs to be powerful enough and for other techniques (such as frequency synchronization ) to develop enough so OFDM becomes a reality. But this is a topic for another posting…