5G NR Deployment Scenarios: NSA, SA, Homogeneous, Heterogeneous

This article outlines the different deployment scenarios or modes for 5G NR (New Radio), including NSA (Non-Standalone), SA (Standalone), Homogeneous, and Heterogeneous modes.

5G NR deployment scenarios are defined by the radio access technologies (RATs) used and the type of core network (EPC or 5G CN) handling signaling.

Introduction

5G NR will be deployed in stages, following 3GPP specifications released in December 2017. Given the existing global deployment of LTE (4G), 5G NR will initially be deployed alongside LTE to accelerate its introduction.

Eventually, as the technology matures and all 3GPP specifications are finalized, 5G NR will operate as a standalone RAT. It’s also likely that 5G NR smartphones will support both modes, switching based on the available RATs in different network locations.

To support both LTE and 5G NR, smartphones must be compatible with both RATs. LTE-only phones won’t work on 5G NR networks, and 5G NR phones (provided they also support LTE) won’t work on LTE networks.

Figure 1: 5G NR Overall Architecture (as defined in 3GPP TS 38.300)

• gNB: Provides NR user plane and control plane protocol termination towards the UE, connected to the 5GC via the NG interface.
• ng-eNB: Provides E-UTRA user plane and control plane protocol termination towards the UE, connected to the 5GC via the NG interface.

5G NR Non-Standalone (NSA) Mode vs. Standalone (SA) Mode

Figure 2: 5G NR deployment scenarios-1

The two primary deployment modes are Non-Standalone (NSA) and Standalone (SA), determined by whether the RATs operate individually or in combination. The following sections detail the differences.

5G NR Non-standalone (NSA) Mode

• Requires a connection to both LTE and 5G cells.
• LTE handles control plane (C-Plane) functions like call origination, termination, and location registration.
• 5G NR focuses solely on the user plane (U-Plane).
• 5G radio control parameters are exchanged via LTE. This requires modifications to the eNB.
• UE monitors paging channels on LTE.

5G NR Standalone (SA) Mode

• UE operates using only 5G NR; LTE is not required.
• 5G NR handles both C-Plane (Control Plane) and U-Plane (User Plane) for signaling and information transfer.
• 5G radio control parameters are exchanged via 5G NR.
• UE monitors paging channels on the 5G cell.

Figure 3: 5G NR deployment scenarios-2

As shown in Figure 3, a Non-standalone UE requires an LTE eNB cell and EPC for signaling, while information transfer occurs over the 5G NR cell. A Standalone UE requires a 5G NR cell and a 5G CN (Core Network) for both signaling and information transfer.

5G NR Homogeneous Mode vs. Heterogeneous Mode

The modes are Homogeneous and Heterogeneous, depending on coverage and capacity requirements in LTE and 5G RATs.

• Homogeneous Mode: LTE Base Station (ng-eNB) and 5G NR Base Station (gNB) provide the same coverage.
• Heterogeneous Mode: LTE and 5G NR base stations serve different coverage areas. Cells with smaller coverage areas support higher capacity, and vice versa. LTE and 5G NR cells function either as small cells or macro cells and vice versa.