The main idea is that an OFDM transmitter first creates many modulated subcarriers digitally at baseband, combines them into one complex signal using an IFFT, and then converts that complex baseband signal into a real RF waveform using I/Q upconversion. 1. The overall OFDM transmitter Input bits 0s and 1s QAM / QPSK mapping Bits → complex symbols X [ k ] X[k] IFFT Frequency-domain symbols → time-domain samples x [ n ] x[n] Cyclic prefix + DAC Prepare the discrete signal for transmission I branch I ( t ) cos ⁡ ( 2 π f c t ) I(t)\cos(2\pi f_ct) Q branch − Q ( t ) sin ⁡ ( 2 π f c t ) -Q(t)\sin(2\pi f_ct) RF output s ( t ) = I ( t ) cos ⁡ ( 2 π f c t ) − Q ( t ) sin ⁡ ( 2 π f c t ) s(t)=I(t)\cos(2\pi f_ct)-Q(t)\sin(2\pi f_ct) The transmitter has two conceptually different stages: OFDM generation: construct a complex baseband signal containing many orthogonal subcarriers. I/Q upconversion: shift t...