Why NR SFN least 4 bit is appended by PHY but not with MIB payload?

Question

Anyhow PHY is appending 4bits of SFN with MIB payload, but As per RRC MIB payload it is not part of it. Why is this two type of MIB payload?

Answer 1

Hi Jaganathan,

MIB is generated from RRC layer. If the last 4bit of SN also included in MIB payload then every time RRC should send it to physical layer whenever SFN changes.
Instead of this RRC gives MIB payload at one shot and least 4bit will be incremented and appended by PHY.
Once MSB bit changes then RRC can give updated payload.