5G NEW RADIO

5G NR explained from architecture to procedures

A practical starting point for understanding how 5G NR radio access and the 5G Core work together.

System architecture

5G separates the radio access network from the service-based 5G Core. The gNB provides NR radio connectivity while core functions handle access and mobility, session management and user-plane connectivity.

Important interfaces

Common interfaces include the air interface between UE and gNB, Xn between gNB nodes and NG between the RAN and 5G Core. Understanding which network function owns a message is often the first step in troubleshooting.

Frame structure

NR uses flexible time structures built from slots and OFDM symbols. The exact timing depends on the configured numerology and subcarrier spacing.

Numerology

Numerology changes subcarrier spacing and therefore the duration of OFDM symbols and slots. This flexibility allows NR to serve different deployment and latency requirements.

Resource grid

The NR resource grid is organized in time and frequency. Resource elements form the basic unit, while resource blocks group frequency resources for scheduling.

RRC and procedures

RRC controls important UE and radio configuration procedures including connection establishment, reconfiguration, measurements and mobility-related signalling.

Network slicing

Network slicing allows logical services with different requirements to share common infrastructure. The engineering challenge is connecting slice selection, policy, QoS and the actual end-to-end user experience.

QoS and 5QI

5G QoS uses standardized QoS characteristics to describe service behaviour. For troubleshooting, follow the path from application expectations to QoS flow, policy and radio scheduling.

PDU sessions

A PDU session provides UE connectivity to a data network. Registration and session establishment should be understood as separate but connected procedures.