- Theoretically, you're right. When all subcarriers are modulated the (baseband) bandwidth of an OFDM signal is approximately $f_\mathrm{s}/2$. An ideal rectangular filter before A/D conversion would be needed at the receiver to avoid anti-aliasing. As such a filter cannot be implemented in practice, some subcarriers remain unmodulated to make the OFDM spectrum narrower. This zero padding in frequency domain corresponds to oversampling in time domain.
- An OFDM symbol including guard interval consists of $N_\mathrm{c} + N_\mathrm{G}$ samples each of which has duration $1/f_\mathrm{s}$. The "oversamplingrate" parameter in your formula is not clear to me. As a rate usually has the unit 1/second your formula's result is without unit which is a contradiction to the left hand side of your equation. Any reference for this formula?
Deve
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