Reading this article on Wireless USB, prompted me to think about just how pervasive the RF modulation known as OFDM is becoming.

I'm someone who pretty much has to know how something works, once it enters my consciousness. So, in mid-2000, while researching Australia's chosen form of digital TV, Digital Video Broadcasting - Terrestrial (DVB-T), I discovered a fascinating form of RF modulation, known as Orthogonal Frequency Division Multiplexing (OFDM).

The Technology

Traditional forms of modulation send one stream of information over one channel. OFDM sends many streams of information at once, over multiple, slower, channels (sometimes thousands of channels), simultaneously. By doing so, it increases the robustness of the individual channels to effects like multipath distortion (reflections from buildings, hills, trees, etc. that manifest as ghosting in analogue TV). By using appropriate levels of error correction, it can also be relatively immune to effects like selective channel-fading.