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An OFDM signal is made of subcarriers that are orthogonal to each other. This terminology makes me think that if one is only interested in information on a specific subcarrier, only that subcarrier needs to be received. However, if this is the case, won't the FFT stage in the receiver yield an incorrect result thus giving incorrect data?

Can someone explain if/how it is possible to just receive one subcarrier or if the whole signal does indeed need to be received?

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  • $\begingroup$ If you only want to demodulate a single subcarrier, you don't have to take a DFT at the receiver. You can just bandpass filter around the carrier as if it's a single carrier signal and demodulate it. $\endgroup$ Commented Feb 13 at 1:12

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It is certainly possible to receive one subcarrier with a customized receiver acting as a single carrier demodulator (however I can't think of any good reason to actually do this). If a known training pattern was sent first, it would be straightforward to remove the cyclic prefix and then piece together the resulting and equivalent continuous-time modulating waveform and pass that time domain signal through a traditional single-carrier demodulator that is centered on the sub-carrier frequency of interest.

This post explains further how an OFDM signal is multiple single-carrier signals in parallel (but does not get into the cyclic prefix):

https://dsp.stackexchange.com/a/90299/21048

This post details further what the cyclic prefix is about:

Can an OFDM signal be demodulated at a sample offset over the cyclic prefix?

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