How to determine the FFT size from Subcarrier spacing and channel bandwidth?

5G NR
1

Hello pros,
The maximum FFT size in 5G NR is 4096, but how do we calculate the size from the channel bandwidth and the required subcarrier spacing??

2

I don’t think that the FFT size is specified whatsoever.

3

FR1 cell bandwidth max 100Mhz.
For example, 100Mhz scs 30khz, 273RB.
No of sub carriers = 273*12 = 3276
FFT 2048 is not enough for sampling 3276 subcarriers, must be at least fft 4096.

1 Like
4

But for 60mhz, the number of subcarriers is 1944, that means 2048 fft size is suitable but we use 4096 fft size, why

5

Nothing prevents to use higher FFT.