LTE subcarriers calculations

[mr_byte31]

Hi All,

I was trying to make some simple calculations on LTE
**broken link removed**

lets take 1.4MHz as an example

1.4MHz cell uses FFT with size 128, we all know that the spacing between subcarriers are 15KHz

so if we want to calculate the BW from FFT ----> (128-1)*15K = 1.905 MHz which is much bigger than 1.4Mhz

i got confused now!

any help ?

 

[FvM]

Consider the simple fact that FFT size must be a power of two. Part of the result might be discarded.

 

[mr_byte31]

i know that FFT should be power of 2 , 128 = 2^7
(128-1) = number of spacings between FFT points

so lets return back to the calculations , (128-1)*15K = 1.905 MHz is larger than 1.4MHz, do i have probs in my calculations?