Data is converted from serial to parallel, mapped to some complex symbols using constellation mapping, then, using the inverse fast fourier transform, is converted to what seems one complex number with a real and imaginary part, which is then converted to some continuous signal using DAC.
On some other diagrams, the output of the IFFT is the same size as the input, and all of the outputs are multiplied by some (orthogonal) carriers before being transmitted, e.g. on this diagram (in French, but it should be clear what is what):
I'm having trouble understanding how these two diagrams relate with each other: are they different systems ?
As the FFT takes as an input a sampled continuous signal (so, let's say $N$ complex numbers), the IFFT should output $N$ complex numbers, but this does not appear on the Wikipedia diagram. Am I missing something?