Why we need MAC to PHY interface in LTE? Why we dont have standard interface between other layers ?

Question

How LTE MAC treats MBMS differently compare to the normal user data. What different actions are taken for the MBMS specific data in the MAC layer ?

Answer 1

Hi,

LTE PHY is manufactured by different vendor's, so to communicate with 3rd party component we need an standard interface so they have come up with FAPI. L2 and L3 is developed by same vendors so there is no use of standard interface they can their own way of communication.

Answer 2

Just to add on, technical specifications talk about protocol messages for example RRC layer between UE and eNodeB but specification does not cover how RRC and lower layers (PDCP/RLC) will communicate. Each vendor has its own implementation for communication between its own layers.