Now suppose if original MIB transmitted on 1st SFN and copies of MIB transmitted on 2, 3, 4 and UE came to network on 2nd SFN and started decoding MIB from SFN:3.
So which 2 bits UE will use to decode SFN info, how UE figure that out?
It will ignore SFN 3 and 4 and gets synchronized with eNodeB from SFN 5.
This is the only point of doubt, is it mentioned somewhere?
I am unable to find this explanation anywhere.
Since all RVâs are independent of each other containing complete info of 24 bits, looking at that UE should be capable of reading those SFNâs.
SFN size is 8 bit that we have discussed but how UE figure out exactly which SFN UE is reading is still unclear.
How UE figure out exactly which SFN UE is reading MIB, from all RVâs?
Because MIB periodicity is 40 ms or 4 frame.
System frame length is 1024 frame.
So 8bit value = 256, can indicate the frame of MIB.
I read all the responses but couldnât find how 2 LSB bits are extracted.
Please try to understand this way.
Suppose 8 bits are as follows: xxxx xxxx
Assume UE read PSS and SSS and have frame sync. Assume random 8 bits being transmitted by NW. But last 2 bits are unknown to UE.
Nth Frame: 1011 0010 xx
N+1 : 1011 0010 xx
N+ 2: 1011 0010 xx
N+3: 1011 0010 xx
Now definitely 8th bit will toggle.
N+4: 1011 0011 00 Here UE will get 10 bits of SFN. 8th bit toggles means LSBs are 00 definitely.
So the logic is donât matter what frame number UE sync, it will check when the 8th get toggles, and mark 2 LSB bits as 00 and extract full SFN info.
Now take example UE1 get sync at N+2 it will detect the toggle of 8th bit and get full SFN 10 bits after 20ms.
UE2 sync at N+3, it will see the toggle on next frame itself and get full SFN on next frame onwards.
Hope this is clear. Thanks