Orthogonal Frequency Division Multiplexing model continued [Under Modulation >> Digital modulation >> OFDM]
Below is a simplified OFDM transmitter model.
1) Original (serial) bit steram is converted to parallet bit stream (one each for orthogonal subcarrier)
2) Modulation block applies individual modulation techniques to produce symbol stream. Symbol would mean points on constellations digram. This is a frequency presentation of input bits.
3) IFFT block converts this to time domain signal (it may add guard carriers) and sums them in such a way that it can be recovered by FFT process at receiving side. Result is discrete (complex) time domain samples. Due to relative low rate, sampled values when conncted would look like OFDM signal that need to be sent over carrier signal.
4) These samples then goes through process of coversion to sine/cosine waves (DAC - digital to analog conversion), providing smooth OFDM baseband signal. RF modulator raises it to carrier frequency level for trasmission over air.
OFDM References: Check Wikipedia page on OFDM, Thesis from Lawrey, and Complex2Real site OFDM Tutrorial.
© Copyright Samir Amberkar 2010
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