ofdm subcarriers plot
Actually if you look at the frequency domain plot, the peak of one carrier is on the point where the the two carriers; one on its right and one on its left have their zero crossing. And you know at zero crossing they would contribute to zero energy to the center carrier, And this is how, even after 'overlapping' they dont mix.
In fact if you look at this statement carefully, you'd also understand why we say that OFDM signals are extremely sensitive to Doppler shifts, as it violates the idea of non-overlapping carriers
I hope that helped you
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