Radio Frame on which UE will receive the SIB can be calculated as:
SFN mod T = FLOOR(x/10)
Subframe on which SI window will start for the corresponding radio frame is
a = x mod 10
value of x = (n -1) * w
n - number which represents the order of entry in scheduling info list.
For SIB2, n = 1
For SIB3, n = 2 and so on
w - SI window length ( 20 ms in our case)
T - SI periodicity of the corresponding SI message
Now lets calculate for SIB3:
Subframe from which SI window will start for SIB3
x = (2 - 1) * 20 = 20
a = 20 mod 10 = 0
so, the SI window will start from subframe 0 for the corresponding radio frame.
Radio Frame on which SIB3 will come
SFN mod T = FLOOR ( x /10 )
T = rf64 = 640 ms
SFN mod 640 = FLOOR ( 20 / 10 )
SFN mod 640 = 2
So, SIB3 will come on the radio frame for which SFN mod 640 = 2. UE will start looking for SIB3 from subframe number 0 of radio frame till the end of window length.