Control Plane Protocol stack
User Plane Protocol Stack:
Protocol stack layers:
Function of RRC layer:
System Information related messages to AS and NAS
Paging, RRC connection establishment, maintenance and Release
It is also responsible for security function including key management.
In carrier aggregation, Scell addition, modification and release
Dual connectivity between EUTRA and NR
SRB, DRB establishment, configuration and release
Additional functions like Handover, Context Transfer, Cell selection, Re-selection, Inter RAT mobility.
QoS measurement, Measurement Reporting
Function of SDAP layer:
Service Data Adaption Protocol.
This protocol is used to handle QoS scenarios.
It is used for mapping between QoS flow and radio bearer.
SDAP will map a specific QOS flow within a PDU session to a corresponding Data Radio Bearer.
If the gNB is connected to EPC, then it is a Non Standalone Mode and SDAP will not be used.
Function of PDCP layer:
Header Compression: ROHC
Ciphering to protect user data
Control Plane Integrity protection.
Duplicate detection Removal.
In sequence ordering of SDU
Function of RLC layer:
Segmentation and re-segmentation
Error correction through ARQ
Reassembly of SDU
Function of MAC layer:
Mapping between logical channels and transport channels
Multiplexing and demultiplexing of MAC SDU’s
Scheduling information Reporting
Error correction through HARQ
Priority handling between UE’s by means of dynamic scheduling
Function of Physical layer:
Error detection on the transport channel and indication to higher layers
Hybrid ARQ soft-combining
Power weighting of physical channels
Modulation and demodulation