This article will give you a brief introduction to 5G Architecture and 5G protocol stack.
It is not the end-to-end architecture, but an overview. In the up-coming chapters we shall see the end to end architecture and protocol stack functionality.
5G overall architecture:
gNB and ng-eNB.
gNB is 5G RAN
ng-eNB is Next Generation eNB. If eNB is connected to gNB then it will be ng-eNB.
Now NG-RAN is connected to 5GC or 5G Core.
5G core Network:
5GC on a high level has AMF and UPF.
AMF: Access and Mobility Management Function. It is similar to MME in 4G.
UPF: User Plane Function
gNB and ng-eNB are connected with each other with Xn interface. In 4G it is X2 interface.
gNB and ng-eNB are connected to AMF and UPF using NG interface. In 4G it is S1 interface.
5G Protocol Stack:
5G protocol stack is very much similar to 4G protocol stack, with addition to the “SDAP” layer in 5G.
5G User Plane Protocol Stack
As you can see from the above image, an additional layer “SDAP” has been introduced.
SDAP stands for Service Data Adaptation Protocol.
SDAP layer is used to handle QoS flow handling across the 5G air interface.
It will map the specific QoS flow with in a PDU session to a corresponding DRB (Data Radio Bearer).
5G Control Plane Protocol Stack
As you can see from the image above, MME functionality has been replaced by AMF.
And instead of eNB it is gNB.
Similar to LTE, here also the NAS message will be embedded in RRC message and sent it to gNB. gNB will forward the NAS message to AMF.
5G Protocol stack layers
From the above image we can see that:
In layer 3 we have: NAS, RRC
In layer 2 we have: SDAP, PDCP, RLC, MAC.
In layer 1 we have: PHY.