WHAT ARE THE USER PLANE PROTOCOL STACK AND FUNCTIONALITY OF THOSE PROTOCOL LAYERS?

LTE user plane is shown in the figure below.

LTE radio interface architecture consists of UE and eNodeB.

The resulting user plane protocol stack and the protocols involved in the LTE radio interface are shown in figure below.

In LTE user plane, the four radio protocol layers are terminated in the eNodeB.

The brief functionalities of each protocol stack are abbreviated in the diagram above.

The functionalities of Physical and MAC layer are typical to what a MAC and Physical layer does in other network domains.