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NR Architecture of 5G NSA Option 4 Variants Explained

As 5G networks progressed beyond the initial LTE-anchored setups, service providers looked for ways to utilize the 5G Core (5GC) without completely shifting away from LTE radio access. This led to the development of Non-Standalone (NSA) Option 4, an important intermediary architecture defined by 3GPP.

The uploaded image, titled “NR architecture of variants of option 4,” shows two closely related configurations:

Option 4

Option 4a

Both options combine LTE and NR under a 5G Core, which allows operators to smoothly transition to full Standalone (SA) networks while still taking advantage of their existing LTE coverage.

In this article, we’ll dive into the details of Option 4 and Option 4a, paying special attention to control plane anchoring, user plane routing, and interface usage, as highlighted in the image.

Understanding Option 4 in the 5G Architecture Landscape

Where Option 4 Fits

According to 3GPP deployment options:

Options 3/3a/3x → LTE core (EPC)

Options 4/4a → 5G Core (5GC)

Option 2 → Full 5G Standalone

Option 4 stands out because:

NR gNB serves as the Master Node (MN)

LTE ng-eNB is the Secondary Node (SN)

5GC replaces EPC

Dual connectivity is still supported

This approach represents a core-first migration strategy.

Key Network Elements in the Image

The architecture shown in the image features the following components:

5GC (5G Core)

Manages session handling, mobility, authentication, and policy enforcement.

Connects through:

NG-C (control plane)

NG-U (user plane)

gNB (NR gNodeB – Master Node)

Ends the control plane connection with 5GC

Manages dual connectivity

Acts as the main anchor for the UE

ng-eNB (LTE Secondary Node)

An LTE base station modified for 5GC connectivity

Supplies LTE radio resources

Links to gNB via the Xn interface

Highlighted Interfaces

NG-C: Control plane connection between gNB and 5GC

NG-U: User plane link between 5GC and gNB/ng-eNB

Xn-C: Control signaling between gNB and ng-eNB

Xn-U: User plane data forwarding between gNB and ng-eNB

Option 4: gNB-Anchored Control and User Plane

Architecture Overview

In Option 4, both the control plane and primary user plane are anchored at the NR gNB, as shown on the left side of the image.

Key features include:

gNB connects to 5GC using NG-C and NG-U

ng-eNB acts exclusively as a secondary node

User plane data for LTE is routed through Xn-U

How Data Flows

Control plane: UE → gNB → 5GC (via NG-C)

User plane (NR): UE → gNB → 5GC (via NG-U)

User plane (LTE): UE → ng-eNB → gNB → 5GC (via Xn-U + NG-U)

The gNB serves as the main anchoring point, making mobility and session management easier.

Advantages of Option 4

Strongly NR-focused architecture

Fully utilizes 5GC capabilities

Clear separation from EPC

Simpler mobility management

Limitations

LTE user plane relies on gNB for forwarding

A bit more latency for LTE traffic

Requires upgraded LTE nodes (ng-eNB)

Option 4 is a good fit when NR coverage is robust and LTE primarily adds capacity.

Option 4a: Direct User Plane from ng-eNB to 5GC

Architecture Overview

Option 4a improves on Option 4 by enabling direct NG-U connectivity between ng-eNB and 5GC, illustrated by the black user-plane path on the right side of the image.

The control plane remains the same:

Anchored at gNB via NG-C

How Data Flows

Control plane: UE → gNB → 5GC

User plane (NR): UE → gNB → 5GC

User plane (LTE): UE → ng-eNB → 5GC (direct NG-U)

Xn-C: Used for coordination between gNB and ng-eNB

Importance of Option 4a

This variant streamlines the user plane for LTE traffic, which leads to:

Lower latency

Reduced load on gNB

Improved throughput for LTE users

Trade-Offs

More complex integration

Needs NG-U support at ng-eNB

Requires tighter coordination between core and RAN

Option 4a is fine-tuned for performance and scalability, especially in environments with both LTE and NR.

Option 4 vs Option 4a: Key Differences

FeatureOption 4Option 4aCore network5GC5GCMaster NodegNBgNBLTE user plane anchoringgNBng-eNBXn-U usageYesNoUser plane efficiencyMediumHighArchitectural complexityMediumHighLTE latencyHigherLower

Why Operators Go for Option 4 Architectures

Option 4 variants hold strategic value because they:

Allow early use of the 5G Core

Enable LTE and NR to coexist

Get networks ready for full Standalone migration

Support advanced 5GC features like:

Network slicing

Service-based architecture

Cloud-native deployments

For many operators, Option 4 was a key step toward Option 2 (SA).

Operational and Deployment Considerations

When choosing between Options 4 and 4a, operators look at:

The maturity of NR coverage

The share of LTE traffic

Latency needs

Core network readiness

RAN upgrade potential

Urban networks with high capacity often prefer Option 4a, while initial 5GC deployments might start with Option 4.

Relevance in Modern 5G Networks

Even as Standalone 5G rolls out, Option 4 architectures stay relevant because:

Many networks are still mixing NSA/SA environments

LTE devices continue to represent a large portion of user bases

Gradual migration helps limit service interruptions

Understanding Option 4 is key for network planning, optimization, and troubleshooting.

Conclusion

The image “NR architecture of variants of option 4” clearly shows how Option 4 and Option 4a create a bridge between NSA and SA 5G deployments.

Option 4 centralizes both control and user planes at the gNB.

Option 4a enhances performance by allowing direct LTE user plane access to the 5GC.

These architectures illustrate how operators can embrace the 5G Core early, maximize NR advantages, and still leverage their LTE investments. Together, they mark an important step in the global shift toward fully Standalone 5G networks.

NR Architecture of 5G NSA Option 3 Variants Explained

In the early stages of rolling out 5G globally, the Non-Standalone (NSA) architecture took the lead. Here, 5G New Radio (NR) integrates closely with the existing LTE core network. Among the various NSA options established by 3GPP, Option 3 and its variants—Option 3, Option 3a, and Option 3x—were pivotal in speeding up the initial 5G rollouts.

The image titled “NR architecture of variants of option 3” clearly shows the differences between these variants in terms of control plane and user plane connectivity, while still relying on the Evolved Packet Core (EPC) and EN-DC (E-UTRA–NR Dual Connectivity).

This article breaks down each Option 3 variant to help you grasp how data flows, where signaling ends, and what led operators to prefer one variant over another.

Background: What Is 5G NSA Option 3?

In 5G NSA Option 3, LTE serves as the anchor network:

LTE eNB is the Master Node (MN)

NR gNB (en-gNB) is the Secondary Node (SN)

EPC stands as the core network

UE connects to both LTE and NR at the same time via EN-DC

The main goal of Option 3 is straightforward:

To introduce 5G NR for enhanced capacity and speeds while making the most of LTE core infrastructure.

Key Network Elements in the Image

The image consistently features these components across all variants:

EPC (Evolved Packet Core)

Manages mobility, session handling, and user data

Ends S1-C (control plane) and S1-U (user plane) connections

eNB (LTE eNodeB – Master Node)

Manages control-plane signaling with the EPC

Coordinates dual connectivity with NR

en-gNB (NR Secondary Node)

Supplies NR radio resources

Links to eNB through the X2 interface

Interfaces

S1-C: Control plane connection between eNB and EPC

S1-U: User plane connection between EPC and eNB or en-gNB

X2-C: Control signaling between eNB and en-gNB

X2-U: User plane data transfer between eNB and en-gNB

Option 3: LTE-Anchored User Plane via eNB

Architecture Overview

In Option 3, both the control plane and user plane terminate at the LTE eNB.

From the image:

EPC connects to eNB through S1-C and S1-U

eNB forwards NR user data to en-gNB using X2-U

en-gNB doesn’t connect directly to the EPC

Data Flow Characteristics

Control plane: EPC → eNB → UE

User plane: EPC → eNB → en-gNB → UE

The eNB works as a traffic aggregation and anchoring point.

Key Advantages

Minimal modifications to EPC

Quick and easy deployment

Strong LTE control stability

Key Limitations

Possible bottleneck at the eNB for the user plane

Increased latency due to traffic handoff

Limited scalability for NR performance

Option 3 was a great choice for very early 5G launches, where getting to market quickly was more critical than optimizing data-plane efficiency.

Option 3a: Direct NR User Plane from EPC

Architecture Overview

Option 3a enhances user plane efficiency by enabling direct S1-U connectivity between EPC and en-gNB, as illustrated by the black user-plane path in the image.

Key differences from Option 3:

Control plane remains anchored at the eNB

NR user plane flows around the eNB

Data Flow Characteristics

Control plane: EPC → eNB → UE

User plane (NR): EPC → en-gNB → UE

X2-C: Maintained for node coordination

Why Option 3a Matters

This variant bypasses the eNB in the NR data path, leading to:

Lower latency

Better throughput for NR users

Greater scalability for high-capacity services

Trade-Offs

Needs EPC support for S1-U termination at en-gNB

Slightly more complex integration

Option 3a caught the eye of operators wanting better NR performance while still staying with NSA.

Option 3x: Split User Plane with Dual Paths

Architecture Overview

Option 3x stands out as the most flexible—and complex—variant of Option 3.

From the image:

EPC keeps S1-U connections to both eNB and en-gNB

User plane can flow through: * eNB (LTE path) * en-gNB (NR path) * X2-U allows forwarding between nodes if needed

Data Flow Characteristics

Control plane: Always anchored at eNB

User plane: * LTE data through eNB * NR data directly through en-gNB * Optional forwarding via X2-U

Why Option 3x Is Powerful

Dynamic traffic management

Load balancing between LTE and NR

Enhanced resource usage

Challenges

Highest architectural complexity

Requires intricate coordination

More signaling overhead

Option 3x is ideal for densely populated urban areas, where traffic patterns can change quickly and performance is key.

Comparing Option 3 Variants

FeatureOption 3Option 3aOption 3xEPC to eNB S1-UYesYesYesEPC to en-gNB S1-UNoYesYesX2-U usageYesNoYesUser plane efficiencyLowMediumHighDeployment complexityLowMediumHighNR scalabilityLimitedImprovedMaximum

Why Operators Chose Option 3 Architectures

With the Option 3 family, operators could:

Launch 5G quickly using existing EPC

Gradually upgrade NR performance

Avoid a rushed switch to 5G Core (5GC)

Support dual connectivity with low risk

Most operators kicked off with Option 3, then moved to 3a or 3x, and eventually transitioned to Standalone (SA) architectures.

Relevance in Today’s Networks

Even as many networks shift to 5G SA, the Option 3 variants hold significance because:

NSA remains extensively deployed globally

Older devices still depend on EN-DC

EPC-based systems continue to function alongside 5GC

Grasping these variants is crucial for network optimization, troubleshooting, and migration planning.

Conclusion

The image “NR architecture of variants of option 3” effectively showcases the architectural evolution of 5G NSA Option 3. Each variant—Option 3, 3a, and 3x—strikes a different balance among simplicity, performance, and complexity.

Option 3 focuses on quick deployment and LTE stability

Option 3a boosts NR data efficiency

Option 3x provides maximum flexibility and performance

Together, these architectures established the foundation for early 5G success, enabling operators around the globe to roll out 5G services quickly while gearing up for the eventual move to Standalone 5G.

Understanding Low-Band Utilization in 5G NSA: DSS and Refarming Approaches

Even though high-band and mid-band spectrums offer incredible speeds, the low-band spectrum is vital for ensuring solid nationwide 5G coverage. Its ability to effectively penetrate buildings and maintain consistent connections over distances makes it indispensable. That said, many of the low-band frequencies were originally set aside for LTE.

In the uploaded image titled “Low Band Utilization based on DSS or Refarming,” we can see two practical methods to effectively use low-band spectrum in 5G Non-Standalone (NSA) setups:

(c) DSS + EN-DC based architecture

(d) Spectrum refarming + EN-DC based architecture

These strategies integrate LTE, NR FR1, NR FR2, Dual Connectivity (DC), and Carrier Aggregation (CA) to enhance spectrum efficiency while ensuring service continuity.

The Importance of Low-Band Spectrum for 5G

Low-band frequencies (generally below 1 GHz) offer:

Wide cell coverage

Great indoor penetration

Reliable uplink performance

Smooth mobility even at high speeds

But, the low-band spectrum’s availability is often limited and scattered. This situation compels operators to use smart sharing and migration tactics—precisely what DSS and refarming facilitate.

Key Technologies Displayed in the Diagram

Before diving into the two scenarios, let’s define the main technologies presented in the image.

EN-DC (E-UTRA–NR Dual Connectivity)

The LTE eNodeB serves as the Master Node (MN)

The NR gNodeB acts as the Secondary Node (SN)

Commonly used in early 5G NSA rollouts

NR-DC (NR–NR Dual Connectivity)

Both master and secondary nodes utilize NR

This allows for aggregation across NR layers (FR1 and FR2)

NR Carrier Aggregation (NR-CA)

Merges multiple NR carriers

Frequently used between low-band NR FR1 and high-band NR FR2

NR Frequency Ranges

FR1: Sub-6 GHz (includes low-band and mid-band)

FR2: mmWave (high capacity with limited range)

DSS + EN-DC Based Low-Band Utilization (Figure c)

The left side of the image showcases Dynamic Spectrum Sharing (DSS) combined with EN-DC.

What Is DSS?

DSS is a method that lets LTE and NR share the same frequency band dynamically by allocating resources on a subframe or symbol basis, without any fixed partitioning.

This lets operators roll out 5G services without needing upfront refarming of the LTE spectrum.

Architecture Breakdown

In Figure (c), starting from the bottom:

LTE layer featuring LTE Carrier Aggregation (LTE CA)

LTE + NR layer, where DSS allows both technologies to operate side by side

NR FR1 and NR FR2 layers

Multiple UE connections are established using: * EN-DC (LTE + NR) * NR-DC (NR FR1 + NR FR2)

NR-CA linking NR FR1 and NR FR2

How Low-Band DSS Functions

LTE stays as the anchor * Offers coverage and control-plane stability * Supports older LTE-only devices

NR is scheduled dynamically * NR taps into unused LTE resources as needed * No immediate need for dedicated low-band NR spectrum

EN-DC merges LTE and NR * LTE adds stability * NR enhances throughput and capacity

NR-DC and NR-CA boost performance * NR FR1 secures NR connectivity * NR FR2 provides additional high-band capacity when available

Benefits of DSS-Based Low-Band Utilization

Immediate spectrum refarming isn’t necessary

Quicker rollout of 5G

Coexistence of LTE and NR users

Minimal disruption to existing LTE services

DSS Drawbacks

Lower spectral efficiency compared to pure NR

LTE control signals can limit NR capacity

Performance is influenced by the LTE/NR traffic mix

Spectrum Refarming + EN-DC Based Low-Band Utilization (Figure d)

On the right side of the image, spectrum refarming combined with EN-DC illustrates a more developed phase of 5G deployment.

What Is Spectrum Refarming?

Refarming is the process of reallocating spectrum that was originally used solely by LTE to NR, usually as LTE traffic tapers off.

Architecture Breakdown

Key components in Figure (d):

Dedicated low-band NR FR1 layer

LTE layer remains as the anchor

NR FR2 layer dedicated to high capacity

UE connections through: * EN-DC (LTE + NR) * NR-DC (NR FR1 + NR FR2)

NR-CA linking low-band NR FR1 and FR2

How Refarmed Low-Band NR Operates

Low-band spectrum conducts pure NR * Boosted spectral efficiency * No LTE overhead

LTE functions as the EN-DC anchor * Smooth transition path * Backward compatibility maintained

NR FR1 acts as the coverage layer * Strong uplink and mobility * Reliable anchor for FR2

NR FR2 enhances peak data rates * Activated dynamically for users demanding high throughput

DSS vs Refarming: A Comparative Overview

Aspect DSS + EN-DC Refarming + EN-DCLTE coexistence Same band Separate band NR spectral efficiency Moderate High Deployment speed Very fast Gradual LTE impact Minimal Requires LTE traffic reduction NR performance Limited by LTE overhead Optimized NR performance Long-term strategy Transitional Strategic

The Role of NR-DC and NR-CA in Both Scenarios

In these architectures, NR-DC and NR-CA are both essential enablers:

NR-DC allows the simultaneous usage of NR FR1 and FR2

NR-CA aggregates low-band NR with high-band NR

This ensures:

Stability in coverage

Scaling capacity

Enhanced user experience

This layered strategy guarantees that mmWave (FR2) can operate in real networks despite its coverage challenges.

Operational and Deployment Considerations

Typically, operators follow this evolution path:

Starting rollout using DSS

Migrating traffic from LTE to NR

Partial or full spectrum refarming

Growing reliance on NR-DC and NR-CA

Transitioning toward NR Standalone (SA)

This phased approach minimizes risks while maximizing returns on spectrum assets.

Use Cases Enabled by Low-Band Utilization

Efficient use of low-band spectrum supports:

Nationwide 5G coverage

Deployments in rural and suburban areas

High-speed mobility (like on railways or highways)

Reliable uplink for IoT and enterprise services

Smooth indoor coverage

Conclusion

The uploaded image effectively demonstrates how low-band spectrum is crucial for 5G NSA deployments, utilizing both Dynamic Spectrum Sharing (DSS) and spectrum refarming strategies, anchored by EN-DC.

The DSS + EN-DC method allows for a quick introduction of 5G with minimal disruption to LTE.

The Refarming + EN-DC approach achieves superior NR performance and long-term efficiency.

Together, NR-DC and NR-CA merge low-band coverage with high-band capacity.

These combined methods give operators a flexible, evolving strategy toward achieving full 5G potential—balancing coverage, capacity, and cost while paving the way for Standalone 5G and beyond.

Exploring High-Band Utilization in 5G NSA: Architecture and Options

High-band spectrum, particularly mmWave (NR FR2), is crucial for reaching the ultra-fast data speeds that 5G promises. But these high-band signals come with challenges, such as limited range and increased path loss. To tackle these issues, 3GPP rolled out flexible Non-Standalone (NSA) deployment strategies that smartly mix LTE and NR resources using Dual Connectivity (DC) and Carrier Aggregation (CA).

The uploaded image titled “High-band Utilization based on NSA option” displays two main architectural options:

(a) EN-DC based architecture

(b) NE-DC based architecture

Both of these approaches aim to leverage the NR FR1 (sub-6 GHz) and NR FR2 (mmWave) spectrum efficiently while using LTE or an upgraded version of LTE as the anchor. Let’s delve into what the image illustrates and how these architectures work to utilize high-band in real networks.

Understanding the Fundamentals: NSA, DC, CA, FR1, and FR2

Before we get into EN-DC and NE-DC, it’s good to clarify some key terms shown in the diagram.

5G NSA (Non-Standalone)

In NSA mode, LTE serves as the control-plane anchor, while NR is added for faster user data. This setup lets operators kick off 5G services without needing a complete 5G core.

Dual Connectivity (DC)

DC enables a UE to connect to two nodes at the same time:

A Master Node (MN) for control signaling

A Secondary Node (SN) for extra user-plane capacity

Carrier Aggregation (CA)

CA combines multiple carriers (same RAT) to boost overall bandwidth. In the image, this appears as NR-CA between NR FR1 and NR FR2.

NR Frequency Ranges

FR1: Sub-6 GHz spectrum (better coverage, moderate capacity)

FR2: mmWave spectrum (very high capacity, limited coverage)

High-Band Utilization with EN-DC (Figure a)

The left side of the image showcases EN-DC (E-UTRA–NR Dual Connectivity) as the basis for high-band utilization.

What Is EN-DC?

In EN-DC:

LTE eNodeB works as the Master Node (MN)

NR gNodeB serves as the Secondary Node (SN)

This was the first widely adopted 5G NSA setup, speeding up 5G deployment.

Architecture in the Image

In Figure (a), moving from bottom to top:

The LTE + NR anchor at the base indicates LTE as the control-plane anchor.

Multiple UE connections marked EN-DC and NR-DC, showing that:

The UE keeps LTE connectivity.

NR is added as a secondary data path.

NR FR1 and NR FR2 blocks sit at the top.

NR-CA links NR FR1 and NR FR2.

How High-Band Utilization Works in EN-DC

LTE provides coverage and control

Reliable mobility

RRC signaling

Session continuity

NR FR1 adds mid-band capacity

Serves as a bridge for capacity and coverage

Strengthens the NR leg

NR FR2 delivers peak throughput

mmWave carriers kick in when radio conditions are suitable

Primarily used for downlink-heavy traffic

NR Carrier Aggregation

FR1 and FR2 are combined via NR-CA

Enables seamless usage of both sub-6 GHz and mmWave spectrum

Key Benefits of EN-DC High-Band Utilization

Quick 5G rollout

Utilizes existing LTE infrastructure

Effective mmWave offloading

Improved user experience in crowded areas

High-Band Utilization with NE-DC (Figure b)

The right side of the image features NE-DC (NR–E-UTRA Dual Connectivity), which is an advancement of the NSA concept.

What Is NE-DC?

In NE-DC:

NR gNodeB becomes the Master Node

eLTE (evolved LTE) acts as the Secondary Node

This reflects a more NR-focused NSA architecture that sets the stage for future Standalone (SA) network evolution.

Architecture in the Image

In Figure (b), you’ll see:

eLTE at the base, marked as the secondary system.

UE connections labeled NE-DC and NR-DC, indicating NR-anchored control.

NR FR1 and NR FR2 again at the top.

NR-CA between FR1 and FR2, similar to EN-DC.

How High-Band Utilization Works in NE-DC

NR leads the control-plane management

NR oversees mobility and session control

Better alignment with future SA networks

FR1 ensures coverage stability

Serves as the anchor layer within NR

Guarantees continuity when FR2 isn’t available

FR2 enhances capacity

mmWave is added dynamically for extreme throughput

Great for densely populated urban areas and enterprises

eLTE complements NR

Offers extra spectrum and coverage

Ensures backward compatibility

Comparing EN-DC and NE-DC

Aspect EN-DC Base NE-DC Base Master Node LTE e Node BNR g Node B Control Plane LTE-anchored NR-anchored Role of LTE Primary anchor Secondary support NR Position Secondary Node Master Node Migration Path LTE → NR NSANSA → NR SA High-band usage NR FR2 via LTE anchor NR FR2 via NR anchor Network maturity Early 5G NSA Advanced NSA

Why FR1 + FR2 + NR-CA Matters

The image highlights NR-CA across FR1 and FR2, which is vital for practical mmWave deployments.

Why This Combination Is Important

FR2 alone is unreliable due to obstruction and limited range.

FR1 stabilizes the connection, serving as an anchor for FR2.

NR-CA allows for seamless bandwidth scaling without interrupting sessions.

Improved quality of experience for applications like:

4K/8K video streaming

AR/VR

Cloud gaming

Fixed Wireless Access (FWA)

Real-World Deployment Scenarios

High-band utilization through EN-DC or NE-DC shines in:

Highly populated urban areas

Stadiums and event venues

Airports and train stations

Industrial sites

Private enterprise networks

Operators can turn on FR2 only when conditions are right, keeping power use and signaling overhead low.

Final Thoughts

The diagram does a great job of showing how 5G NSA facilitates efficient high-band utilization via a mix of Dual Connectivity, NR Carrier Aggregation, and multi-frequency NR setups.

EN-DC represents the initial, LTE-based NSA phase, perfect for quick 5G rollout.

NE-DC hands control over to NR, providing better performance and a smoother transition to Standalone 5G.

NR-CA between FR1 and FR2 is the key factor that makes mmWave not just a concept, but a reality in today’s networks.

All these architectures help operators strike a balance between coverage, capacity, and complexity, ensuring high-band spectrum delivers on its potential. As networks advance, NE-DC and refined NR-CA setups are set to play a huge role in unlocking what 5G—and beyond—can truly offer.

Disaggregated Architecture for Integrated Access & Backhaul in 5G Networks

With 5G networks growing fast to deliver higher data speeds, super low latency, and massive numbers of connections, mmWave deployments have become crucial. Still, mmWave’s limited range and need for lots of small cells pose a big problem: how do we ensure reliable backhaul without laying down a ton of fiber?

That’s where Integrated Access and Backhaul (IAB) comes into play. IAB enables the same 5G radio spectrum to handle both access traffic (from end devices) and backhaul traffic (between base stations), cutting down the need for extra fiber. The image you uploaded shows a disaggregated IAB architecture, illustrating how IAB donors and IAB nodes connect to improve mmWave coverage.

Here’s a straightforward and detailed explanation of this architecture.

Introduction to 5G IAB Architecture

5G IAB is based on RAN disaggregation, which essentially means breaking up functions like the Central Unit (CU), Distributed Unit (DU), and Mobile Termination (MT) to give more flexibility in deployment.

In a typical network, each small cell would need its own fiber backhaul connection. But with IAB:

A parent node (IAB Donor) provides wireless backhaul.

Child nodes (IAB Nodes) take the backhaul and keep serving users or send it on to more downstream nodes.

This creates a multi-hop wireless topology, which is perfect for busy urban areas, stadiums, campuses, and places where using fiber is too costly or not practical.

IAB Donor Components Explained

The left side of the image highlights the functional split within an IAB Donor—the node that connects straight to the 5G Core Network.

Key Components of an IAB Donor

1. Central Unit – Control Plane (CU-CP)

Takes care of important control-plane functions, including mobility management, RRC signaling, and resource coordination.

Oversees flow control and organizes downstream IAB nodes.

2. Central Unit – User Plane (CU-UP)

Deals with user data traffic.

Routes data to and from the core network for users on both access and backhaul.

3. Distributed Unit (DU)

Handles radio-specific tasks like MAC scheduling, HARQ, and lower-layer functions.

The DU in the IAB donor not only supports access devices but also schedules radio resources for wireless backhaul links.

4. Other Functions (OF)

Covers management tasks, QoS, and network orchestration jobs.

Role of the IAB Donor

The IAB donor serves a few key purposes:

Connects to the 5G Core Network

Provides wireless backhaul for downstream IAB nodes

Offers access services for local 5G mmWave gadgets

Basically, it’s the foundation of the multi-hop IAB network.

IAB Node Components Explained

The IAB Node broadens coverage by functioning both as a small cell for UEs and as a child backhaul node.

Two Main Functional Blocks in an IAB Node

1. Mobile Termination (MT)

Acts like a “UE” towards the parent IAB donor.

Looks after RRC, PDCP, and backhaul link control.

Ends the wireless backhaul connection.

This is pretty unique: the IAB node actually has a UE-like entity inside, which allows it to connect upstream without needing fiber.

2. Distributed Unit (DU)

Functions as a gNodeB for its downstream child nodes or end-user devices.

Handles resource scheduling (MAC), RLC, and PHY-related tasks.

Allocates and manages spectrum for both access and wireless backhaul.

This design lets every IAB node be:

A user of resources from the parent node (via MT), and

A provider of access/backhaul for child nodes (via DU).

How IAB Enables mmWave Deployments

The right side of the diagram illustrates a typical IAB deployment scenario:

The IAB donor is linked to the 5G core.

One or more IAB nodes connect downstream via mmWave backhaul.

End-user devices, like smartphones, laptops, and AR/VR headsets, connect to mmWave access links provided by the nodes.

Key Benefits for mmWave Deployments

1. Reduced Fiber Dependency

Just one fiber-connected donor can serve multiple wireless hops.

2. Rapid Deployment

Great for temporary or high-traffic situations (events, trade shows, hotspots).

3. Flexible Topology

Supports multi-hop chains and mesh-like setups.

4. Efficient Spectrum Use

The same spectrum gets reused for access and backhaul with smart timeslot allocation from the DU scheduler.

Disaggregated IAB RAN Architecture: Why It Matters

5G RAN disaggregation allows operators to mix and match functional blocks across various hardware or locations.

Benefits of Disaggregated Architecture

Scalability: CU functions can be centralized for numerous nodes.

Reduced Latency: DU stays closer to the RAN edge for quicker scheduling.

Resource Optimization: Backhaul scheduling is efficiently coordinated.

Vendor Flexibility: Operators can embrace Open RAN principles with support for multiple vendors.

Workflow: How IAB Traffic Moves

Here’s a simplified version of how traffic flows through the disaggregated architecture:

1. UE → IAB Node (Access Link)

A device links up with the IAB node’s DU.

The DU manages lower-layer protocols.

2. IAB Node DU → MT (Internal Handover)

Access traffic gets routed internally from DU to MT.

3. MT → IAB Donor (Wireless Backhaul Link)

Backhaul traffic flows via a mmWave wireless link.

MT acts as a UE tied to the IAB donor’s DU.

4. IAB Donor → 5G Core Network

CU-CP handles signaling.

CU-UP directs user plane data to/from the core.

This process repeats for multi-hop setups.

Use Cases of Disaggregated IAB in 5G Networks

1. Dense Urban Networks

Quickly roll out small cells without having to wait for fiber installations.

2. Event Venues and Stadiums

Swift, high-capacity coverage for large groups of users.

3. Remote or Hard-to-Reach Areas

Offer coverage where digging trenches for fiber is way too costly.

4. Campus Networks

Businesses can scale private 5G networks using IAB nodes.

Comparison Table: IAB Donor vs. IAB Node

FeatureIAB DonorIAB NodeCore Network ConnectivityDirectIndirect (via Parent Node)Contains CU?YesNoDU RoleAccess + Backhaul managementAccess + Downstream BackhaulMT RoleNo MTContains MT for upstream connectivityFiber RequirementTypically YesNot RequiredActs as Parent Node?YesYes (for downstream nodes)

Conclusion

The disaggregated architecture for 5G Integrated Access and Backhaul (IAB) marks a significant step towards flexible and scalable mmWave deployments. By breaking RAN functions into CU-CP, CU-UP, DU, and MT components, operators gain unprecedented control over resource allocation for access and backhaul.

IAB donors connect to the 5G core, while IAB nodes expand coverage without needing fiber, creating a cost-effective, quickly deployable network perfect for busy urban areas, events, and enterprise sites.

As 5G keeps spreading, IAB’s disaggregated model will be key in building the next generation of high-capacity, low-latency networks.

Carrier Aggregation vs. Dual Connectivity: A Technical Overview

Today’s mobile networks leverage advanced radio technologies to boost capacity, enhance reliability, and improve user experience. Among the key players in this transformation are Carrier Aggregation (CA) and Dual Connectivity (DC). Both methods aim to enhance data rates by utilizing multiple links, but they have notable differences in terms of architecture, protocol handling, network interaction, and their specific use cases.

The accompanying image contrasts CA (on the left) and DC (on the right), detailing aspects like protocol stack placement, the connection of user equipment (UE), signaling flow, and the functional split between carriers or nodes. This article breaks down that diagram into a more digestible, engineering-friendly explanation.

What Is Carrier Aggregation?

Carrier Aggregation enables a single base station to simultaneously allocate multiple carriers to a single UE. This technique is all about expanding effective bandwidth by combining component carriers (CCs) from various bands.

Referring to the image:

The CA illustration depicts one base station with a unified protocol stack (SDAP, PDCP, RLC, MAC).

Two carriers—Carrier 1 and Carrier 2—connect to the UE via separate physical layers, yet share the same higher-layer processing.

Key Features of Carrier Aggregation

1. Single Node Architecture

All CA activities occur through one base station (either eNodeB or gNodeB). One MAC scheduler manages all the aggregated carriers in this setup.

2. Primary and Secondary Component Carriers

The image categorizes:

PCC (Primary Component Carrier) – in green

SCC (Secondary Component Carrier) – in blue

The PCC oversees RRC signaling, mobility decisions, and main uplink/downlink traffic, while SCCs help boost overall throughput.

3. Layer Structure

From the diagram:

SDAP, PDCP, RLC, and MAC layers work together to process the aggregated data.

The physical layers split at the bottom for each carrier but then come together again at the MAC layer.

4. UE Requirement

A device labeled as “CA capable UE” must be able to handle multi-carrier radio chains to receive data across multiple physical channels at once.

Benefits of Carrier Aggregation

Increased throughput by summing bandwidth (e.g., 20 MHz + 20 MHz + 20 MHz).

Enhanced spectral efficiency using fragmented spectrum.

Easier deployment since it operates within a single node.

Less signaling complexity compared to solutions involving multiple nodes.

Carrier Aggregation is commonly used in LTE-Advanced and remains a core component of 5G NR.

What Is Dual Connectivity?

Dual Connectivity enables the UE to connect to two different base stations at the same time — typically one Master Node (MN) and one Secondary Node (SN). These can include:

LTE eNodeB + 5G gNodeB (EN-DC),

5G gNodeB + 5G gNodeB (NR-DC), or

LTE eNodeB + LTE eNodeB (LTE-DC).

The image uploaded illustrates this dual-node structure clearly.

Key Insights from the Image

The UE connects to both nodes through Link 1 (Master Cell Group – MCG) and Link 2 (Secondary Cell Group – SCG).

There are two separate protocol stacks:

MN stack has SDAP, PDCP, RLC, and MAC.

SN stack contains RLC, MAC, and SDAP.

A Forwarding Tunnel connects MN and SN for data splitting, labeled “4”.

Master Cell Group (MCG) vs. Secondary Cell Group (SCG)

MCG (blue path): The MN is responsible for managing mobility control, RRC signaling, security, and sometimes PDCP.

SCG (green path): The SN adds extra radio resources to enhance throughput or reliability.

Control Plane and User Plane Dynamics

The UE communicates control signals only with the MN.

User data may flow through MCG, SCG, or both, depending on the bearer setup.

Types of Bearers in Dual Connectivity

The image suggests that bearer splitting happens through a forwarding tunnel. This corresponds to:

1. MCG Bearer

Data travels solely through the Master Node.

2. SCG Bearer

Data travels exclusively through the Secondary Node.

3. Split Bearer

PDCP at the MN divides data between MN and SN.

The green and blue arrows in the diagram represent these split paths converging at the UE.

Benefits of Dual Connectivity

Multi-node diversity, enhancing reliability.

Improved mobility performance, especially when switching between different RATs (like LTE + NR).

Boosted throughput by pooling resources from two base stations.

Supports inter-frequency and inter-RAT aggregation, which CA doesn’t.

DC plays a crucial role in early 5G deployments (EN-DC) where LTE anchors mobility while NR supplies high-speed data.

Carrier Aggregation vs. Dual Connectivity: Key Differences

The image emphasizes the architectural differences:

CA = one node, DC = two nodes.

Here’s a concise comparison:

Feature Carrier Aggregation Dual Connectivity Nodes involved One base station Two base stations (MN + SN)Control signaling Via PCC Through MN only User plane paths Single PDCP/RLC/MAC stack Split across two nodes Spectrum flexibility Intra-node, multi-band Inter-node, inter-RAT, inter-frequency Deployment complexity Lower Higher (X2/Xn tunneling, sync)Main benefit Higher bandwidth Greater reliability + through put UE requirement CA capable UEDC capable UE Forwarding tunnel Not required Necessary for split bearer

This table highlights the differences shown in the uploaded graphic.

When to Use Carrier Aggregation vs. Dual Connectivity

Carrier Aggregation is preferable when:

There’s available contiguous or non-contiguous spectrum.

The network aims for low-complexity capacity boosts.

An operator relies on a single RAT (either LTE or NR).

RAN vendors support a broad range of CA combinations.

Dual Connectivity is preferable when:

You need to combine two different RATs (like LTE + NR).

The RAN nodes aren’t co-located.

The network demands redundancy and multi-connectivity.

Early 5G rollout requires LTE as a mobility anchor.

Why Both Technologies Work Together in 5G Networks

5G is crafted for maximum flexibility. Operators might utilize both CA and DC:

CA within each node (aggregating various NR carriers)

DC between nodes (LTE anchor + NR secondary)

This combination allows for very high throughput while ensuring robust mobility.

The diagram illustrates how CA focuses on multi-carrier PHY consolidation, whereas DC emphasizes multi-node radio resource integration.

Conclusion

Carrier Aggregation and Dual Connectivity are crucial technologies that transform how mobile networks deliver bandwidth and reliability. The uploaded image captures the core architectural differences:

CA aggregates multiple carriers within one base station, sharing a single protocol stack.

DC connects the UE to two different nodes, enabling split bearers and multi-RAT support.

For professionals in telecommunications, grasping these differences is key to designing modern LTE-Advanced Pro and 5G NR networks. While CA is the go-to method for efficiently increasing bandwidth, DC becomes essential for incorporating new radio technologies, bridging coverage gaps, and enhancing reliability.

Together, CA and DC enable 5G networks to meet the growing demand for speed, capacity, and seamless mobility, making sure users enjoy consistent, high-performance connectivity across a variety of radio environments.

CU and DU Placement Options in 5G RAN:

A Practical Technical Guide The development of 5G Radio Access Network (RAN) architecture is all about giving operators more choices in their deployments by breaking down RAN functions into Central Units (CU), Distributed Units (DU), and Radio Units (RU). With this more flexible setup, operators can fine-tune their network performance, costs, scalability, and deployment methods based on what they need in terms of spectrum, transport, and services.

The image provided illustrates a comparison of various CU/DU placement architectures, ranging from centralized setups to more distributed hub-site configurations. For those working in telecom or network engineering, picking the right placement strategy is key to managing latency, fronthaul capacity, pooling efficiency, and overall network costs.

This article goes through each deployment variant shown, discussing the pros and cons, and highlighting when each option might work best.

Understanding CU, DU, and RU in 5G RAN

Before we get into placement strategies, it’s important to grasp the roles of the three main components in Open RAN:

Central Unit (CU) – Handles high-layer protocols like PDCP, SDAP, and RRC. – Manages mobility, session control, and higher scheduling. – Can tolerate higher latency (up to about 20 ms, depending on the split). – Best suited for centralization and pooling.

Distributed Unit (DU) – Takes care of lower-layer functions (MAC, RLC, parts of PHY). – More sensitive to latency; usually needs link constraints between 250 μs and 1 ms. – Gains from being close to the RU.

Radio Unit (RU) – Manages RF functions and lower PHY. – Located at or near the antenna site.

With these roles clearly defined, operators can precisely decide where to place CU and DU components.

CU and DU Placement Landscape: Insights from the Image The image shows four general placement models:

Core sites

Aggregation sites

Hub sites

Cell sites (where the RU is located)

Each of these placements comes with its own set of advantages and challenges, influenced by things like:

Latency limits

Transport capabilities

OPEX and CAPEX considerations

Pooling benefits

Support for CoMP and inter-cell communication

The choice between centralization and distribution

The illustration also includes callouts that point out cost and performance impacts like “Less cost,” “Better pooling,” “Higher cost,” and “High link requirement.”

Now, let’s take a closer look at each architecture.

1. Centralized CU Placement In this model, CUs are placed in centralized locations, generally near the core network.

Advantages (as shown in the image):

Lower cost: Fewer CU instances, smaller site footprint.

Better pooling and CoMP: It’s easier to coordinate between cells when CUs are located together.

Streamlined software maintenance and lifecycle management.

Highly scalable—this setup works well in urban or dense markets.

Network Requirements:

Adequate backhaul capacity to handle the combined CU traffic.

DUs still need to be located nearer to RUs to meet fronthaul requirements.

Best For:

Operators with robust backhaul networks

High-density areas that need advanced coordination

Cloud RAN and vRAN setups

This architecture really takes advantage of virtualization and multi-cell collaboration.

2. CU in Aggregation Sites (Distributed Centralization) The image depicts CUs placed at aggregation-layer locations, which are a step closer to the radio network.

Advantages:

Eases transport bandwidth demands compared to core-based CUs.

Lowers latency compared to full centralization.

Still provides pooling benefits for localized clusters.

Trade-Offs:

Pooling efficiency isn’t as high as with core centralization.

More CU instances needed than in a centralized setup.

Best For:

Medium-density networks

Areas with varying backhaul quality

Operators juggling costs with latency performance

This model strikes a balance—centralized enough for efficiency, but distributed enough for latency-sensitive services.

3. DU at Hub Sites (Common Approach) The third part of the image illustrates DUs deployed at hub sites, with RUs situated separately at the cell edge.

Key Benefits:

Provides a balanced approach between centralization and feasible fronthaul links.

Supports low-latency fronthaul connections over shorter distances.

Maximizes DU resource use across a cluster.

Technical Considerations:

Requires a decent fronthaul capacity.

DUs must stay within strict latency limits relative to RUs.

Suitable for mid-band and low-band 5G networks.

Best For:

Suburban deployments

Open RAN with a 7-2x split

Areas with fiber-fed hubs available

Hub-site DU placements are currently the most commonly used commercial model for vRAN and O-RAN projects.

4. Non-Collocated DU (Displayed on Right Side) The note “Non collocated DU – High link requirement” points out the challenges:

Challenges:

When the DU is placed too far from the RU, the fronthaul needs to support very high capacity, low jitter, and extremely low latency.

Requires fiber with strict timing (under 250 μs one-way).

Use Cases:

Very few, typically for specialized setups

Dense fiber-connected urban small cells

Operators using microwave fronthaul advancements

While this setup can work, it’s often costly and performance-sensitive.

5. Remote CU (Right Side) The note “Remote CU” outlines:

Higher cost

No centralization benefits

A remote CU is situated close to or at the same site as the DU or RU.

Advantages:

Keeps CU-DU latency minimal.

Useful for extremely latency-sensitive private networks.

Drawbacks:

Loses pooling and CoMP advantages.

Needs multiple CU instances.

Drives up costs and site complexity.

Best For:

Highly distributed private 5G industrial networks

Scenarios where ultra-low latency processing is needed nearby

Most public networks steer clear of this architecture due to scalability issues.

Table: Comparing CU/DU Placement Options

Model Latency

Advantage Cost Transport

Requirement Pooling/Co MP Best Use Case Centralized CU Medium Low Strong backhaul Excellent Dense urban, C-RANCU at Aggregation Sites Better Medium Moderate Good Regional areas DU at Hub Sites Strong Medium Medium fronthaul Fair Suburban, O-RAN Non-Collocated DU Weak High Very high Limited Fiber-rich urban Remote CU Strongest Highest Low Poor Private 5G, local edge

Conclusion

The image summarizes the different placement strategies for CUs and DUs in a modern 5G RAN architecture. As operators weigh their options, they need to consider latency budgets, fronthaul capabilities, pooling benefits, readiness for the cloud, and service needs. There isn’t a universal solution; the ideal model really depends on geography, transport infrastructure, spectrum, and business goals.

Centralized CU architectures offer significant savings and pooling benefits, while hub-site DUs provide a practical compromise for commercial networks. Specialized setups like remote CUs or non-collocated DUs cater to niche scenarios where low latency or local control is more important than sheer efficiency.

As 5G infrastructure continues to evolve and Open RAN grows, having these flexible CU/DU placement options will be key to building scalable, efficient, and future-ready RAN architectures.

5G Wireless–Wireline Convergence Architecture: A Detailed Look

5G is much more than just a radio-based mobile tech. As providers shift toward delivering fully unified services, the industry is quickly adopting 5G Wireless–Wireline Convergence (5G WWC). This setup combines wireless access (5G NR) with various wireline access technologies (like FTTP, xDSL, DOCSIS, and fiber-based residential gateways), allowing all types of services—both fixed and mobile—to operate off the same 5G Core (5GC).

The image provided shows how fixed network elements (defined by BBF) relate to 5G core/control functions (defined by 3GPP). This article simplifies the architecture, demonstrating how Fixed Network Residential Gateways (FN-RGs), 5G Residential Gateways (5G-RGs), Access Gateways (AGFs), UPFs, and ATSSS collaborate to enable converged broadband.

What’s 5G Wireless–Wireline Convergence?

So, what exactly is 5G WWC? It’s a framework designed together by:

3GPP (which defines the 5G core, its N-interfaces, and protocols)

BBF (Broadband Forum) (which focuses on integrating fixed access, U/Y interfaces, and the roles of BNG/AGF)

The main aim is straightforward:

→ To let both fixed broadband subscribers and wireless users connect through one unified 5G Core (5GC).

This gives operators a shared platform for:

Authentication

Policy control

QoS enforcement

Network slicing

ATSSS (Access Traffic Steering, Switching, Splitting)

Billing integration

From the image, it’s clear that both wireless and wireline access feed into the same 5GC, paving the way for a truly converged network.

Key Parts of the 5G WWC Architecture

The image highlights certain regulated areas in red (for BBF) and blue (for 3GPP). Let’s unpack these components.

1. Residential Gateways (RGs)

5G-RG (5G Residential Gateway)

This is a customer premises equipment (CPE) device that natively supports 5G protocols, including:

NAS signaling (to AMF)

ATSSS functions

5G authentication

Essentially, the 5G-RG operates like any standard 5G User Equipment (UE).

FN-RG (Fixed Network Residential Gateway)

This gateway represents a more traditional broadband CPE that doesn’t support 5G signaling. Instead, it relies on the AGF, as defined by BBF, to handle 5G control-plane signaling on its behalf.

2. AGF – Access Gateway Function (BBF-defined)

The AGF is crucial for linking wireline access to the 5G core. It:

Translates fixed-access protocols into 5G interfaces

Proxies NAS signaling from FN-RGs

Enforces policies from the 5G core

Forwards data towards UPF

In the image, AGF sits between FN-RG/BNG and the 5GC via the N2/N3 interfaces.

3. UPF – User Plane Function (3GPP)

UPF is key for converged data forwarding. It manages:

QoS flow enforcement

ATSSS session traffic splitting

Routing to the Data Network (DN)

Flow-based forwarding from fixed and mobile routes

The UPF connects with ATSSS logic and links to the DN via N6.

4. ATSSS – Access Traffic Steering, Switching, Splitting

ATSSS makes it possible for multi-access convergence across:

Wi-Fi

Fixed broadband

5G NR (wireless)

Any combination of these

ATSSS decides how traffic moves by:

Steering: Selecting the best access per session

Switching: Transitioning a session between accesses

Splitting: Utilizing multiple accesses at once

That’s why ATSSS is referenced in both the 5G-RG and the UPF.

5. AMF, SMF, N3IWF, TNGF (3GPP)

These functions support the entire control plane for both mobile and fixed users.

AMF (Access and Mobility Management Function) takes care of registration, authentication, and access management.

SMF (Session Management Function) sets up PDU sessions from wireless and wireline access.

N3IWF (Non-3GPP Interworking Function) facilitates untrusted Wi-Fi integration.

TNGF (Trusted Non-3GPP Gateway Function) supports trusted Wi-Fi or wired access flows.

These components are linked via N2/N3 interfaces, all in line with 3GPP standards.

6. Interfaces: Blue = 3GPP, Red = BBF

The image uses colors to show which organization governs each interface:

Blue (3GPP) → Defined interfaces like N2, N3, N4, N6, Ta, Nwu

Red (BBF) → Defined interfaces like Y4, Y5, A10

Here’s a quick summary of key interfaces:

Interface Org Function N1/N23GPPNAS/control signaling between RG/AGF and AMFN33GPPUser plane from AGF/BNG to UPFN43GPPSMF–UPF control N63GPP Connectivity to Data Network Y4BBF Connection between 5G-RG and AGFY5BBFFN-RG to BNG/AGF connection A10BBFBNG to AGF interface Nwu3GPP Wireless untrusted access (Wi-Fi)

This breakdown emphasizes the teamwork between BBF and 3GPP.

Traffic Flows in the Converged Architecture

The image illustrates three main scenarios:

1. 5G-RG Access (Native 5G)

Steps:

The 5G-RG establishes NAS signaling directly with AMF via Y4 → N2.

User traffic heads to UPF via Y4 → N3.

ATSSS can function at both the RG and UPF levels.

Finally, UPF sends data to the DN via N6.

This is the most “native” converged scenario.

2. FN-RG via BNG + AGF (Proxy Mode)

FN-RG does not support 5G NAS directly; AGF plays the role of translator.

Steps:

FN-RG sends packets through Y5 to BNG.

The BNG then forwards the right flows to AGF via A10.

AGF converts signaling/user-plane to N2/N3 aimed at AMF/UPF.

This way, it accommodates legacy broadband setups.

3. Wi-Fi (Trusted/Untrusted)

N3IWF manages untrusted access (like home Wi-Fi not controlled by the provider).

TNGF deals with trusted Wi-Fi access.

These pathways also utilize ATSSS when multi-access is permissible.

Why 5G Wireless–Wireline Convergence Matters

1. Unified Core for All Services

Providers can operate one core for:

Mobile 5G users

Fixed broadband subscribers

Enterprise broadband

Wi-Fi access

2. Seamless Multi-Access Integration

ATSSS enables smooth traffic merging from mobile, fiber, and Wi-Fi.

3. Simplified Network Architecture

Using 5GC cuts down on the need for various legacy cores (like PPPoE, IMS-only setups).

4. Enhanced QoS and Slicing

Both fixed and mobile users stand to gain from:

Network slicing

QoS enforcement

PDU Session-based policy control

5. Faster Service Innovation

A unified architecture speeds up:

Smart home services

Fixed Wireless Access (FWA)

Edge computing rollout

Integrated billing and policy management

Conclusion

The image depicts a thorough model of the 5G Wireless–Wireline Convergence Architecture, illustrating how the frameworks from BBF and 3GPP collaborate to unify fixed and wireless broadband through the 5G core. By bringing together FN-RGs, 5G-RGs, AGFs, UPFs, AMF/SMF, and advanced features like ATSSS, providers can deliver reliable, scalable broadband services across all access technologies.

Ultimately, 5G WWC builds a single converged ecosystem—one that can support next-gen multi-access experiences, network slicing, and unified broadband services for everything from homes to businesses.

5G System Integration as a TSN Bridge: A Closer Look for Telecom Experts

As 5G moves beyond just traditional broadband uses, it’s quickly becoming essential in areas like industrial automation, robotics, and real-time control systems. One of the standout features of 5G in the context of Industry 4.0 is how it works with Time-Sensitive Networking (TSN)—a series of IEEE standards meant to ensure reliable, low-latency communication over Ethernet.

The image provided gives a simple depiction of 5G serving as a “bridge” within a TSN environment, illustrating how the 5G System (5GS) fits into the overall TSN framework. This setup enables 5G networks to handle time-sensitive data while ensuring the kind of synchronization and reliability you’d expect in industrial settings.

In this piece, we’ll dive into the architecture shown in that image and break down how 5G meets TSN standards, from translators to control-plane functions and user-plane forwarding.

Getting to Grips with TSN and Its Importance in 5G

TSN (Time-Sensitive Networking) finds its place in various sectors, including manufacturing, process control, energy, and robotics. Here’s what it brings to the table:

Predictable latency

Limited jitter

High reliability and redundancy

Synchronized timing across devices

Controlled traffic shaping

Regular Ethernet doesn’t offer these guarantees, but TSN enhancements pave the way for predictable data transmission—something crucial for industrial control systems.

5G amplifies TSN by extending these promises wirelessly, which is a game changer for mobile robots, automated guided vehicles (AGVs), remote I/Os, and adaptable production lines.

The Mechanics of 5G as a Logical TSN Bridge

The image illustrates how the 5G system integrates into a larger Logical (TSN) Bridge. Within this setup:

A typical TSN bridge consists of several ports that direct deterministic traffic based on TSN schedules.

The 5G system functions like a bridge segment, ensuring that TSN traffic flows seamlessly over wireless connections.

This integration is split into two key areas:

Device Side of the Bridge – where industrial I/O units connect via User Equipment (UE)

Network Side of the Bridge – where the 5G system connects with centralized TSN controllers.

Device Side of the Bridge: How Industrial Devices Connect to 5G

On the left side of the picture, industrial endpoints link to the 5G system through TSN Translators (DS-TT) and UEs.

Essential Components:

1. I/O Devices

These include industrial endpoints such as:

Sensors

Actuators

PLC interfaces

Industrial switches

They generate deterministic traffic that needs strict timing guarantees.

2. TSN Translator (DS-TT – Device-Side TSN Translator)

This component translates TSN traffic from the industrial device into 5G-compatible flows.

It handles:

Mapping Ethernet/TSN frames to 5G QoS flows

Meeting traffic scheduling needs

Keeping synchronization info intact.

3. UE (User Equipment)

The UE serves as the interface connecting the device-side translator to the 5G radio network.

It supports:

5G QoS flows

Timing synchronization mechanisms (like gPTP over 5G)

URLLC profiles for low latency.

Together, this translation process ensures reliable entry of TSN traffic into the 5G system.

User Plane Flow: How TSN Traffic Moves Through 5G

In the center of the diagram, the User Plane manages the transport of deterministic traffic.

Key Features Include:

(R)AN – Radio Access Network

The 5G RAN allocates wireless resources based on TSN needs:

Low-latency uplink grants

Deterministic scheduling

Prioritized traffic for URLLC.

UPF – User Plane Function

The UPF directs packets while adhering to:

QoS Flow Identifiers

Packet Detection Rules

TSN timing requirements.

The UPF acts as the main switching hub in the logical TSN bridge.

This user-plane route guarantees that TSN frames traverse the 5G network with limited latency and jitter.

Control and Management Plane: Upholding TSN Policies

The right side of the image outlines the control and management components in the 5G Core that engage with TSN controllers.

Control Plane Elements:

NEF – Network Exposure Function

Provides APIs for TSN controllers to:

Request QoS monitoring

Set up traffic flows

Access network analytics.

PCF – Policy Control Function

Implements policies regarding:

QoS allocations

Priority mapping

Slice assignment.

These elements ensure that TSN traffic is allocated the appropriate resources within the 5G system.

Network Side of the Bridge: TSN Translation and Coordination

The network side oversees the interaction between 5G and external TSN controllers.

Key Components:

1. AF as TSN Translator (nw-tt-cp)

This Application Function manages control-plane translation between TSN and 5G.

It is responsible for:

Mapping TSN traffic schedules to 5G QoS profiles

Coordinating time synchronization

Facilitating deterministic service provisioning.

2. TSN Translator (DS-TT) on Network Side

Like its device-side counterpart, this handles:

TSN frame reconstruction

Forwarding to TSN-compatible Ethernet networks

Clock synchronization capabilities.

3. TSN CUC – Centralized User Configuration

The CUC configures endpoints and bridges with:

Traffic schedules

Time synchronization settings

Stream reservation details.

The TSN CUC collaborates with the 5G AF and NEF to make sure the 5G system adheres to TSN scheduling needs.

End-to-End Overview: How the 5G–TSN Bridge Operates

Putting everything together, here’s how the flow works:

1. Industrial I/O device produces TSN frames

These require careful handling.

2. DS-TT translates traffic and sends it to UE

TSN requirements are kept intact.

3. UE forwards traffic into the 5G RAN

Wireless scheduling aligns with TSN requirements.

4. UPF transports user-plane traffic

Traffic is prioritized and time-aware during forwarding.

5. Network-side DS-TT reconstructs TSN traffic

Frames are converted back to Ethernet TSN format.

6. TSN CUC configures the 5G system

The CUC and AF work together on timing and scheduling.

This setup enables 5G to serve as a wireless TSN bridge segment, making mobile TSN applications viable.

Why the 5G–TSN Integration is Crucial for Industry 4.0

Key Advantages Include:

Wireless deterministic communication perfect for mobile robots, AGVs, and flexible production lines.

Smooth integration with existing TSN networks so businesses can build on their current TSN setups using 5G.

Centralized configuration via TSN CUC which simplifies network management.

High reliability and minimal latency thanks to URLLC, precise scheduling, and synchronization.

Adaptable deployment allowing factories to change layouts without needing to rewire Ethernet connections.

The combination of 5G and TSN sets the stage for next-gen industrial automation systems.

Conclusion

The uploaded image gives a clear overview of how 5G can fit as a logical TSN bridge, enabling wireless segments to engage effectively in deterministic industrial Ethernet networks. With the help of TSN translators, UEs, UPF forwarding, and tight coordination among AF, NEF, and PCF, the 5G system can support time-sensitive industrial communication.

This architecture is key to Industry 4.0, fostering mobile, synchronized, and ultra-reliable wireless connectivity for advanced manufacturing, robotics, and real-time control settings. As 5G networks continue to develop towards 5G-Advanced, their integration with TSN will be crucial in reshaping industrial operations on a global scale.

Overview of 5G Use Cases: A Comprehensive Guide for Telecom Professionals

5G isn’t just about faster speeds; it’s a whole new approach to connectivity that can handle a wide variety of communication needs—from immersive entertainment and fixed wireless access to industrial automation and smart transportation.

The included image organizes 5G use cases into three primary service categories as defined by 3GPP: Enhanced Mobile Broadband (eMBB), Massive Machine-Type Communications (mMTC), and Ultra-Reliable Low-Latency Communications (URLLC). These categories align with three types of communication: human-to-human, human-to-machine, and machine-to-machine.

This article dives into these categories, offering a detailed, reader-friendly narrative that brings the visual content to life.

Breaking Down the Three Pillars of 5G

5G networks are built around three core service families. Each one caters to different performance needs and serves specific industry sectors.

1. Enhanced Mobile Broadband (eMBB): Elevated Connectivity Solutions

eMBB is all about advancing data-driven services, prioritizing high throughput, improved spectral efficiency, and better mobility performance.

Key Performance Goals for eMBB

20 Gbps / 10 Gbps peak download/upload speeds

~4 ms user-plane latency

Mobility support for speeds up to 500 km/h

These specs allow for smooth, high-quality connections, even in crowded places and fast-moving situations like high-speed trains.

Main eMBB Use Cases (as shown in the image)

• Virtual Reality (VR) & Augmented Reality (AR)

For applications like VR and AR, you need speedy connections and minimal lag for a truly immersive experience. That’s where 5G steps in, making these technologies viable for gaming, training remotely, and teamwork.

• Video Calls and Virtual Meetings

With remote work becoming the norm, 5G enhances real-time, high-resolution communication, ensuring that video streams run smoothly from users to cloud services.

• Fixed Wireless Access (FWA)

5G FWA can deliver fiber-like speeds, particularly in suburban and rural areas, transforming last-mile access.

• Ultra-High Definition (UHD) Video Streaming

The delivery of high-bandwidth 4K/8K content becomes seamless, especially during busy times in overcrowded urban areas.

• Video Surveillance and Mobile Cloud Computing

In machine-to-machine scenarios, eMBB is used for cloud-based video analytics, security monitoring, and real-time data transfer from edge devices.

2. Massive Machine-Type Communication (mMTC): Fueling the IoT Revolution

mMTC is designed for high device density, ultra-low power usage, and solid indoor coverage—key for expansive IoT ecosystems.

Key Performance Goals for mMTC

1 million devices per km²

Battery life over 10 years

20 dB coverage improvement

With these targets, millions of sensors can function within smart homes, smart cities, agriculture, and various industrial settings.

Core mMTC Use Cases (according to the image)

• Wearables and Connected Gadgets

Devices like fitness trackers, medical patches, and smartwatches depend on mMTC for efficient, lasting connections.

• Social Media and Daily Connected Devices

As more gadgets come with sensors and wireless features, mMTC offers scalable connectivity that avoids network clutter.

• Smart Homes and Smart Cities

This category covers:

Energy management sensors

Smart lighting

Waste management systems

Environmental tracking

Automation of public services

Smart cities need dense IoT connections that require minimal maintenance.

• Healthcare Monitoring

Remote monitoring devices send small data packets over long stretches of time. Thanks to mMTC’s long battery life and improved coverage, continuous health tracking is possible, whether in hospitals or at home.

• Vehicle-to-Infrastructure (V2I) Communication

Traffic signals, road signs, and connected vehicles can exchange data, leading to better safety and efficiency.

• Industrial Automation

Factories are using IoT sensors to monitor systems, optimize production, and quickly identify issues.

3. Ultra-Reliable Low-Latency Communication (URLLC): Critical Applications for 5G

URLLC is aimed at applications that need nearly flawless reliability and ultra-low latency, which is essential for safety, automation, and real-time control.

Key Performance Goals for URLLC

1 ms user-plane latency

99.99999% availability (seven nines reliability)

Heightened security and resilience

Peak rates for critical data flows

These features make 5G a good fit for sectors that require consistent service performance.

Core URLLC Use Cases (from the image)

• Emergency Services Communications

First responders get a significant boost from ultra-reliable communication, crucial for real-time data sharing, imagery, voice communications, and mission coordination.

• Remote Surgical Procedures

Remote surgery relies on haptic feedback and rapid robotic control, needing extremely low latency and assured reliability. 5G URLLC facilitates surgical assistance and robotic interventions.

• Vehicle-to-Pedestrian (V2P) Interaction

Automated safety features can detect pedestrians and react within split seconds, enhancing urban mobility and reducing accidents.

• Vehicle-to-Vehicle (V2V) Communication

Connected vehicles need to communicate for safe braking and lane changes, necessitating sub-millisecond latency for smooth autonomous driving.

• Industrial Automation (Mission-Critical)

In factories that utilize robotics and require timely control, URLLC is vital for precise timing and machine cooperation.

Mapping 5G Communication Modes to Use Cases

The image also shows how different use cases fit into communication directions:

Mode | Description | Typical Use Cases

Human-to-Human | Traditional communication made better by 5G speed and reliability | VR meetings, video calls

Human-to-Machine | Interaction between users and devices | Fixed wireless access, video surveillance

Machine-to-Machine | Communication among sensors, vehicles, and control systems | IoT, industrial automation, V2V, V2I

This categorization makes it clear that 5G isn’t just about super-fast internet; it’s enabling a range of intelligent, automated communication pathways.

The Importance of These Use Cases for Telecom Professionals

Telecom operators and engineers need to weigh several factors when rolling out 5G networks:

• Spectrum Distribution

eMBB works best in mid-band and mmWave spectrums.

mMTC benefits from low-band spectrum.

URLLC might need dedicated slices for enhanced reliability.

• Network Slicing

Applications for URLLC and mMTC often need isolated virtual networks that ensure reliable performance.

• Edge Computing Integration

Low-latency applications, like those in autonomous vehicles or remote surgery, do better when computing resources are placed nearby.

• Backhaul and Transport Efficiency

High-capacity fiber and microwave backhaul need to keep up so that 5G radio performance isn’t hindered by transport limits.

Final Thoughts

This summary emphasizes the transformative potential of 5G across eMBB, mMTC, and URLLC. Each category opens up new opportunities—ranging from immersive digital experiences and scalable IoT to mission-critical automation and smart transportation.

Understanding these use cases equips telecom professionals to design, enhance, and deploy networks that meet a variety of performance needs. As 5G advances and evolves into 5G-Advanced and beyond, these foundational pillars will be crucial in shaping the next wave of connectivity innovation.