The deployment of 5G networks brings both similarities and differences compared to LTE, particularly in the 5G NR (New Radio) protocols. While the typical OSI layers and 5G NR protocols on the air interface are primarily relevant for Stand-alone Architecture, there are notable changes in the User Plane stack with the addition of the Service Data Adaptation Protocol (SDAP) layer. This layer, on top of the Packet Data Convergence Protocol (PDCP), is crucial for Quality of Service (QoS) Flow and Bearer mapping, marking QoS Flow ID for downlink and uplink packets. PDCP has evolved from its initial specification by 3GPP for UMTS, to LTE, and now to 5G NR. So, now let us see Are 5G NR Protocols Are Changing Connectivity along with User-friendly LTE RF drive test tools in telecom & RF drive test software in telecom and User-friendly Best wireless site survey software, site survey tools for wireless networks & Indoor cellular coverage walk testing tool in detail.

5G NR Protocols and Layer 2 Data Flow

In 5G NR, Layer 2 data flow allows multiple IP flows within a single Radio Bearer, a departure from LTE’s limitations. The new MAC PDU format in NR supports MAC/PHY parallel processing, which is not facilitated in LTE’s MAC PDU format. Unlike LTE, where MAC sub-headers precede MAC SDUs, MAC CEs, or padding, NR maintains this structure to optimize processing. The introduction of the SDAP layer and changes in Carrier Aggregation enhance NR’s efficiency. Channel Access control and System information requirements remain essential for the Stand-alone option.

NR Principles for Access

NG-RAN (Next Generation Radio Access Network) incorporates sophisticated overload and access control functions like RACH back-off, RRC Connection Reject, and RRC Connection Release. A unified access-barring mechanism in NR addresses all use cases previously managed by specialized E-UTRA tools. Each access attempt is classified into Access Categories as defined in 3GPP TS 22.261. In the RRC_IDLE state, the UE (User Equipment) informs the RRC of its access category, and the Connection Request provides data for the gNB (next-generation NodeB) to decide on request rejection.

Enhanced System Information Delivery in NR

In NR, the broadcasted SIB (System Information Block) information is minimal, akin to MIB/SIB1. On-demand broadcast or dedicated SIB signaling can be requested by the UE, providing flexibility and efficiency in system information delivery.

Mobility States and Characteristics

RRC_IDLE State: 5G NR employs the 3GPP PLMN Selection principle, mirroring LTE for initial and stored cell selection. Cell reselection is speed-dependent and service-based, with intra-frequency reselection based on cell ranking and inter-frequency on absolute priorities. NCL/Blacklist can be provided by the serving cell.

RRC_INACTIVE State: In this state, the UE remains in CM-CONNECTED, using cell reselection. The last serving gNB retains the UE context, allowing the UE to move within the RNA without updating the gNB. The gNB pages the UE in the RNA, and the UE initiates the RNA update upon RNA change.

RRC_CONNECTED State: Network-controlled mobility applies with cell-level mobility using RRC signaling (e.g., handover) and beam-level mobility managed at lower layers. Intra-NR handovers are “make-before-break” without 5G core involvement, with UE measurements and reporting including beam measurements.

Random Access Principles

Random access procedures in NR are triggered by events like initial access from RRC_IDLE, RRC Connection Re-establishment, handover, transition from RRC_INACTIVE, SI requests, and data arrival in RRC_CONNECTED with non-synchronized UL. Contention-based random access involves the UE sending a preamble, the gNB responding, followed by scheduled UE transmission and contention resolution. In contention-free access, the gNB assigns the RA preamble, the UE responds, and the gNB replies with the access response.

NG-RAN QoS Concept

The 5G core establishes PDU Sessions for each UE, while the NG-RAN sets up Data Radio Bearers (DRB) per PDU Session, mapping packets from different PDU sessions to DRBs. The NG-RAN ensures at least one default DRB per PDU Session, with NAS-level packet filters in the UE and 5G core associating packets with corresponding QoS Flows. The NG-RAN is responsible for mapping multiple QoS flows to a DRB, supporting Uplink QoS flow to DRB mapping through reflective QoS or RAN explicit configuration.

Voice Support in NR

Voice support becomes significant in 5G SA mode, with IMS voice/VoLTE performed on LTE radio in NSA architecture, requiring no changes from LTE-only operations. As operators transition to option 2 for commercial 5G deployments, end-to-end IMS voice support over 5G core and NR is essential, inheriting LTE functions like SPS.

Public Warning Services (PWS)

Different SIBs are defined for ETWS primary and secondary notifications and CMAS notifications, with paging used to inform UEs about indications. The UE monitors ETWS/CMAS indications in its paging occasions across different RRC states.

Emergency Calls

Starting from 3GPP Rel-15, NR supports emergency calls due to regulatory requirements like FCC in the USA and cell ID in the EU. Enhanced positioning capabilities in Rel-16 support precise positioning via RTK correction information and network-based positioning using smaller cells and massive MIMO with beamforming.

New Principles on UE Capabilities

UE capabilities no longer rely on categories, with the network calculating the maximum supported data rate based on capabilities and related formulas. A default mechanism reduces capability signaling, incorporating LTE optimizations for band combination information. The separation between baseband and RF capabilities is maximized, and UEs can signal temporary capability restrictions for network control.

NR URLLC Support

NR URLLC (Ultra-Reliable Low Latency Communications) minimizes delays while maintaining high service reliability. RLC retransmission (ARQ) is not used in NR to meet strict latency requirements, with packet duplication at the PDCP level used in multi-connectivity and carrier aggregation scenarios. Duplication, configured via RRC, applies to both SRB and DRBs.

Conclusion:

In conclusion, the deployment of 5G NR protocols, with enhancements like SDAP and advanced QoS management, significantly improves connectivity and user experience. Ensuring robust network coverage, especially in high-profile events, is crucial for customer satisfaction and retention, highlighting the importance of continuous network performance testing and optimization.

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