OFDM demodulation, how to set the sampling rate?
Your receiver will consist of, apart from synchronization blocks, an FFT. You want that FFT to generate one output bin for each of the subcarriers. Therefore, you should make use of the relationship between the input sample rate of a DFT to its output bin spacing:

$$
\Delta f = \frac{f_s}{N_{FFT}}
$$

where $\Delta f$ is the subcarrier spacing and $f_s$ is the sample rate (both in Hz). Assuming you know the subcarrier spacing and the FFT size, then it's straightforward to choose the sample rate:

$$
f_s = N_{FFT} \Delta f
$$