FFT – Fast Fourier Transform
OFDM systems utilize a mathematical function called FFT (Fast Fourier Transform)to generate parallel data streams. This process relies on a concept termed Discrete Fourier Transform which provides a way of analyzing the components of a complex waveform. Therefore, the data stream is first converted from a serial stream into a number of parallel virtual branches, the number being equal to the number of virtual sub-carriers in operation in the channel. The appropriate modulation scheme to be employed on each sub-carrier is selected and the Inverse FFT system will calculate the characteristics of the combined waveform which in turn is transmitted across the air interface. At the receiver side, this signal is passed to the FFT entity which generates the composite virtual data streams which can be combined to form a copy of the original data stream.
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