How UE will calculate the SFN and SF in which it will receive the SIB's.

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How UE will calculate the SFN and SF in which it will receive the SIB's.
posted Apr 21, 2014

+1 vote

Once the UE synchronized with eNodeB, it come to know SFN from MIB, after that UE uses the received SFN number for the calculation of subsequent SFN and SF.

+1 vote

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 Example:-
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.