# How may samples per symbol in ieee 802.11 g

I am doing a baseband simulation for IEEE 802.11 g. The standard uses 64 IFFT length ($3.2 \mu s$) and 20 Msamples per second. This result in one sample per symbol. I am wondering what the structure will be if I use 40 Msample per second, i.e will the IFFT size change, or interpolation will be used?

Thanks

## 1 Answer

If you oversample the signal by a factor of 2 as you've suggested, then you will have a bunch of empty subcarriers that are outside the specified signal bandwidth. When you modulate the OFDM frame to a time-domain signal, therefore, you'll have to use an IFFT that is twice as long. The result will be a discrete-time signal that is interpolated by a factor of 2 compared to using the nominal sample rate.

• Thanks Jason R for reply :). I thought that according to the specifications the IFFT length should be fixed to 64 , so it is not and can be changed according to the sampling frequency? – guest Jun 30 '14 at 10:09
• Yes, there's no reason that it can't be larger than 64 if the sampling rate is higher, but all of the extra subcarriers that come with the larger FFT size will be empty. So, there's no real reason to do so. – Jason R Jun 30 '14 at 14:21