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

Question

As i know two type of CQI in lte, sub band CQI and wide band CQI. I wide band CQI it sends channel quality for whole bandwidth but in case of sub band CQI how UE calculates CQI?

Answer 1

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.

Answer 2

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.