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5G Protocol Stack | 5G Layer 1, 5G Layer 2, 5G Layer 3

This page covers 5G Protocol Stack i.e. layer 1,layer 2 and layer 3. The 5G layer-1 is PHYSICAL Layer. The 5G layer-2 include MAC, RLC and PDCP.The 5G layer-3 is RRC layer as shown in 5G protocol stack.

The Figure-1 depicts 5G Protocol Stack consisting of both User Plane and Control Plane protocol layers.


5G Protocol Stack- User Plane and Control Plane

5G Layer 1 | 5G PHYSICAL Layer

Following are the functions of 5G layer 1 i.e. PHYSICAL (PHY) Layer.
•  Error detection on the transport channel and indication to higher layers
•  FEC encoding/decoding of the transport channel
•  Hybrid ARQ soft-combining
•  Rate matching of the coded transport channel to physical channels
•  Mapping of the coded transport channel onto physical channels
•  Power weighting of physical channels
•  Modulation and demodulation of physical channels
•  Frequency and time synchronisation
•  Radio characteristics measurements and indication to higher layers
•  Multiple Input Multiple Output (MIMO) antenna processing
•  Transmit Diversity (TX diversity)
•  Digital and Analog Beamforming
•  RF processing

5G NR Physical layer processing for PDSCH channel

Refer 5G NR PHY layer >> which describes processing of PDSCH and PUSCH channel through PHYSICAL layer modules as defined in 38.200 series documents.

5G Layer 2 | 5G MAC, RLC, PDCP Layer

Following are the functions of 5G layer 2 i.e. MAC sublayer.
•  Beam management
•  Random access procedure
•  Mapping between logical channels and transport channels
•  Concatenation of multiple MAC SDUs belonging to one logical channel into transport block (TB)
•  Multiplexing/demultiplexing of 5G-MAC SDUs belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels
•  Scheduling information reporting
•  Error correction through HARQ
•  Priority handling between logical channels of one UE
•  Priority handling between UEs by means of dynamic scheduling
•  Transport format selection
•  Padding


5G RLC PDU structure

Following are the functions of 5G layer 2 i.e. RLC sublayer.
•  Transfer of upper layer PDUs
•  Error Correction through ARQ (only for AM data transfer)
•  Reordering of 5G-RLC data PDUs (only for UM and AM data transfer)
•  Duplicate detection (only for UM and AM data transfer)
•  Protocol error detection (only for AM data transfer)
•  5G-RLC SDU discard (only for UM and AM data transfer)
•  Segmentation (only for UM and AM data transfer)
•  Resegmentation (only for AM data transfer)
•  5G-RLC re-establishment


5G PDCP PDU structure

Following are the functions of 5G layer 2 i.e. PDCP sublayer in user plane.
•  Transfer of user data
•  In-sequence delivery of upper layer PDUs at 5G-PDCP re-establishment procedure for 5G-RLC AM
•  Duplicate detection of lower layer SDUs at 5G-PDCP re-establishment procedure for 5G-RLC AM
•  Retransmission of 5G-PDCP SDUs at mobility in connected mode for 5G-RLC AM
•  Ciphering and deciphering (Note: Only AES shall be mandatory)
•  Timer-based SDU discard in uplink

Following are the functions of 5G layer 2 i.e. PDCP sublayer in user plane.
•  Ciphering and Integrity Protection (Note: Only AES shall be mandatory)
•  Transfer of control plane data

5G NR MAC structure overview,MCG

Refer 5G NR MAC layer overview >> for more information on 5G NR MAC functions, 5G NR MAC architecture, 5G NR MAC channel mapping, 5G NR MAC procedures and format of 5G NR MAC header and subheaders.

Transparent mode peers

Refer 5G NR RLC layer overview >> for more information on 5G NR RLC modes (TM mode, UM mode, AM mode), data structures (TMD, UMD, AMD), RLC PDUs (TMD PDU, UMD PDU, AMD PDU), data transfers (TM, UM and AM) and RRC parameters which defines RLC layer.

5G Layer 3 | 5G RRC Layer

Following are the functions of 5G layer 3 i.e. RRC Layer.
• Broadcasting of system informations to NAS and AS.
• Establishment, maintenance and release of RRC connection.
• Security including key management
• Establishment, configuration, maintenance and release of point-point radio bearers.
• Mobility functions along wth cell addition and cell release
• UE measurement reporting, control of UE reporting, UE based mobility
• NAS direct message transfer to/from NAS from/to UE
• Refer 5G NR UE RRC states >> and their functions and RRC IEs >> (Information Elements) used in 5G NR UE/gNB and 5G NR system for various purposes.

Reference:
• TS V5G.300
• TS V5G.201
• 3GPP TS 38.212 (Multiplexing and channel coding), TS 38.321 (MAC specifications), TS 38.322 (RLC specifications)
• Website: http://5gtf.net


5G NR Numerology | 5G NR Terminology


5G NR Control channels | 5G NR Traffic Channels | 5G NR Reference Signals and sequences



5G TECHNOLOGY RELATED LINKS

This 5G tutorial also covers following sub topics on the 5G technology:
5G basic tutorial
5G Frequency Bands
5G millimeter wave tutorial
5G mm wave frame
5G millimeter wave channel sounding
Difference between 4G and 5G
5G testing and test equipments
5G network architecture
5G NR Physical layer
5G NR MAC layer
5G NR RLC layer
5G NR PDCP layer

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