OFDM: an introduction - Notes

Goal OFDM stands for 'Orthogonal Frequencies Division Multiplexing'. Instead of modulating a single carrier as is the case with FM or AM, the idea to utilize a number of carriers, spread regularly over a frequency band, in such a way that each of them is modulated with just a small portion of the available energy. This can be done in a flexible way so that the available bandwidth is utilized to maximal efficiency. It is also a 'broadband' technique in that the modulated signal fills out a large bandwidth almost by definition. There are other broadband techniques, one of the most popular is called 'CDMA' for 'Code Division Multiple Access'. It is a direct competitor for OFDM and very interesting in its own right. Here we concentrate on OFDM as an example of the application of the FFT. Later on, or in other courses, other techniques are considered and even combinations of them. OFDM as a generic technique has become very popular as it is used in such major applications as DSL (known as 'MT' or multitone) and digital broadcasting (DAB).