5G System Architecture: Complete Guide to 5G Core Network Functions 2026
Introduction to 5G System Architecture
The evolution of mobile communication has transformed the way people, businesses, and connected devices communicate. In 2026, understanding 5G System Architecture is essential for telecom engineers, network planners, protocol testers, researchers, and students who want to build expertise in modern telecommunications.
The fifth-generation mobile communication system, known as 5G, provides high-speed connectivity, improved network efficiency, flexible service deployment, and support for advanced applications such as industrial automation, smart cities, private networks, and the Internet of Things (IoT).
The 5G System (5GS) consists of three major components: User Equipment (UE), the 5G access network, and the 5G Core Network (5GC). Unlike traditional mobile network architectures, the 5G Core uses a Service-Based Architecture (SBA), in which Network Functions (NFs) communicate through standardized services and interfaces.
This architecture supports scalability, modularity, cloud-based deployment, network slicing, and flexible service management. It also allows network operators to introduce new capabilities and upgrade individual network functions with less dependence on the entire network architecture.
In this complete guide, we will explore the major components of the 5G system, the roles of important core network functions, service-based interfaces, registration procedures, PDU session establishment, network slicing, edge computing, and practical applications.
Whether you are a telecom student, a working engineer, or a professional preparing for advanced 5G and 6G technologies, this article will help you understand how a modern 5G network operates.
Table of Contents
What Is a 5G System?
Understanding 5G System Architecture
What Is Service-Based Architecture in 5G?
Control Plane and User Plane
Major 5G Core Network Functions
Important 5G Interfaces and Protocols
UE Registration and Authentication
PDU Session Establishment in 5G
Network Slicing and Edge Computing
Difference Between 5G Standalone and Non-Standalone
Practical Applications of 5G Core
5G Core Network Troubleshooting
Skills Required for 5G Core Engineers
5G Training and Certification
Frequently Asked Questions
Conclusion
1. What Is a 5G System?
A 5G System is an end-to-end mobile communication architecture that connects user devices to applications, services, and external data networks.
It supports smartphones, 5G routers, industrial devices, IoT sensors, connected vehicles, enterprise applications, and other connected equipment.
The 5G system consists of three fundamental components.
1.1 User Equipment (UE)
User Equipment refers to the device used by a subscriber or application to access the mobile network.
Examples include smartphones, tablets, industrial sensors, customer-premises equipment, and 5G-enabled routers.
The UE communicates with the radio access network and exchanges signaling and user data according to the procedures supported by the network.
1.2 5G Access Network
The 5G access network connects the UE to the 5G Core Network.
The primary 5G radio access network is called the Next-Generation Radio Access Network (NG-RAN). It includes network elements such as the gNB, which provides radio connectivity using 5G New Radio (NR).
Supported non-3GPP access networks can also provide connectivity to the 5GC through the appropriate architecture.
The access network handles radio transmission, radio resource management, and communication with the core network.
1.3 5G Core Network (5GC)
The 5G Core is responsible for important network operations such as registration, authentication coordination, mobility management, session management, policy control, and user-data forwarding.
It includes network functions such as AMF, SMF, UPF, UDM, AUSF, PCF, NRF, and NSSF.
These functions work together to provide connectivity and manage subscriber services.
Why Is the 5G Core Important?
The 5G Core does more than provide internet access. It enables operators to manage subscriber permissions, establish data sessions, apply quality-of-service policies, support network slicing, and connect applications to suitable data networks.
For example, a smartphone streaming a video and an industrial machine requiring low-latency connectivity may use the same underlying infrastructure while having different service requirements.
The core network provides mechanisms for managing these requirements according to subscription permissions, operator policies, and deployment capabilities.
2. Understanding 5G System Architecture
The 5G System Architecture is designed around modular network functions that perform specific responsibilities. These functions interact through standardized interfaces to provide connectivity, mobility management, session control, authentication, and data forwarding.
The major architectural elements include the UE, NG-RAN, 5GC, and external Data Networks (DNs).
The NG-RAN communicates with the AMF through the N2 interface for control-plane signaling and with the UPF through N3 for user-plane traffic.
Within the core network, control-plane functions coordinate registration, authentication, policy decisions, and session management. The UPF handles user-plane packet processing and forwarding toward the appropriate data network.
Key Characteristics of 5G Architecture
Modular network functions: Each network function has a defined role, allowing individual capabilities to be developed and managed separately.
Service-based communication: Authorized network functions can discover and consume services provided by other network functions.
Cloud and virtualization support: The 5GC can be deployed using virtualized infrastructure, containers, orchestration, and cloud-native technologies where supported.
Flexible scalability: Operators can scale selected network functions according to workload, subscriber demand, and service requirements.
Advanced service support: The architecture supports network slicing, differentiated QoS, edge computing, and secure network capability exposure.
These characteristics make 5G suitable for diverse applications ranging from consumer broadband to enterprise connectivity and industrial IoT.
3. What Is Service-Based Architecture in 5G?
Service-Based Architecture (SBA) is one of the most important concepts in the 5G Core.
In SBA, network functions provide services that can be consumed by other authorized network functions through standardized service-based interfaces.
A network function providing a service is called a service producer, while a network function requesting that service is called a service consumer.
For example, an AMF can communicate with the AUSF to support authentication procedures, while the SMF can obtain relevant subscription or policy information through the applicable network functions.
Benefits of Service-Based Architecture
1. Interoperability
Standardized interfaces help network functions from different vendors interact when their implementations conform to the applicable specifications.
2. Scalability
Individual network functions and services can be scaled according to demand.
3. Service discovery
The Network Repository Function (NRF) helps network functions discover available services and suitable network function instances.
4. Flexible upgrades
Individual functions can be enhanced without necessarily redesigning the entire core network, subject to compatibility and deployment requirements.
5. Cloud-native implementation
SBA complements cloud technologies, containerization, orchestration, automation, and modern software deployment practices.
6. Simplified service integration
The modular design helps operators integrate new capabilities and develop more flexible network services.
It is important to understand that not every 5G interface is a service-based API. Interfaces such as N1, N2, N3, N4, and N6 have distinct roles and defined communication procedures.
4. Control Plane and User Plane in 5G
The 5G Core separates network control and decision-making from the forwarding of user traffic. This separation is essential for understanding how the network manages signaling and transports data.
Control Plane
The control plane handles signaling and network decisions.
Its activities include:
UE registration and deregistration.
Authentication coordination.
Mobility and reachability management.
PDU session establishment and release.
Policy and QoS coordination.
Network function discovery.
Network slice selection.
Functions such as AMF, SMF, PCF, AUSF, UDM, and NRF contribute to control-plane operations.
User Plane
The user plane carries actual user traffic between the access network and data networks.
The UPF is the principal 5GC function responsible for user-plane packet handling.
For example, when a user opens a website, the control plane helps establish the required connectivity. Once the session is active, the user plane transports the packets between the UE and the destination network.
Difference Between Control Plane and User Plane
Feature | Control Plane | User Plane |
Primary function | Signaling and decisions | User-data forwarding |
Main functions | AMF, SMF, PCF | UPF |
Typical activity | Registration and session control | Packet forwarding |
Important interfaces | N1, N2, SBI | N3, N6, N9 |
Troubleshooting | Authentication and signaling failures | Routing, packet loss, and throughput |
A UE may register successfully but still experience data connectivity problems because the PDU session, UPF configuration, routing, or external data network is not functioning correctly.
5. Major 5G Core Network Functions
The 5G Core consists of multiple network functions, each responsible for specific operations. Understanding their individual roles and interactions is essential for network engineering, protocol testing, and troubleshooting.
5.1 Access and Mobility Management Function (AMF)
The AMF manages access and mobility-related operations between the UE, access network, and core network.
Its primary responsibilities include:
Managing UE registration and deregistration.
Handling Non-Access Stratum (NAS) signaling.
Coordinating access authentication and authorization procedures.
Managing UE connection and reachability information.
Supporting mobility procedures and handover-related signaling.
Relaying session-management signaling between the UE and SMF.
Supporting paging when required.
The logical NAS signaling relationship between the UE and AMF is identified as N1. The N2 interface connects the NG-RAN to the AMF.
Practical example: When a smartphone powers on and attempts to register with a 5G network, the AMF processes registration signaling and coordinates with other network functions as required.
Successful registration does not automatically guarantee internet access. A suitable PDU session must also be established.
5.2 Unified Data Management (UDM)
The UDM manages subscriber-related information and supports subscription and authentication procedures.
Its responsibilities include:
Managing subscriber profiles and subscription information.
Supporting authentication credential handling.
Providing relevant subscriber information to authorized network functions.
Supporting subscription identity privacy procedures through the applicable architecture.
Supporting subscriber-data management.
The Subscription Permanent Identifier (SUPI) identifies a subscriber permanently within the relevant subscription framework.
The Subscription Concealed Identifier (SUCI) provides a concealed representation of the SUPI for applicable identity-protection procedures.
The UDM works with the AUSF and associated subscriber-data functions to support authentication and subscription management.
5.3 Authentication Server Function (AUSF)
The AUSF supports UE authentication procedures.
Its responsibilities include:
Participating in network authentication.
Working with the UDM to obtain or process authentication-related information.
Validating authentication responses according to the applicable procedure.
Coordinating with the AMF through authentication-related signaling.
During registration, the network verifies whether the UE can authenticate using valid subscriber credentials.
The AMF coordinates the signaling, while the AUSF performs its designated authentication role with support from the relevant subscriber-data functions.
Authentication verifies identity or credentials, whereas authorization determines which network access and services are permitted.
5.4 Session Management Function (SMF)
The SMF manages Protocol Data Unit (PDU) sessions between the UE and a data network.
Its responsibilities include:
Establishing, modifying, and releasing PDU sessions.
Allocating or managing UE IP addressing as applicable.
Selecting and controlling the UPF.
Coordinating QoS and session-related policy enforcement.
Managing session-related signaling through the AMF.
Supporting user-plane path management and traffic-routing decisions.
Practical example: When a UE requests a data session, the SMF processes the request, coordinates policy requirements, selects an appropriate UPF, and arranges the required user-plane configuration.
Depending on the deployment, PDU sessions can support IPv4, IPv6, IPv4v6, Ethernet, or unstructured connectivity.
5.5 User Plane Function (UPF)
The UPF handles user-plane packets and provides connectivity between the access network and data networks.
Its responsibilities include:
Packet routing and forwarding.
QoS enforcement and traffic treatment.
Usage measurement and reporting.
Packet detection and traffic classification.
Support for mobility-related user-plane anchoring.
Traffic steering toward central or local data networks.
The UPF connects to the NG-RAN through N3 and to a data network through N6. It may also connect to another UPF through N9.
For example, an industrial application may send selected traffic to a local edge data network while general internet traffic follows a central network path.
5.6 Network Slice Selection Function (NSSF)
The NSSF supports network slice selection.
Its responsibilities include:
Helping determine allowed network slices for a UE.
Supporting selection of an appropriate AMF set where required.
Helping select suitable network slice instances.
Supporting slice-related decisions according to subscription and network configuration.
Network slicing allows shared physical infrastructure to support logically differentiated network services.
For example, a mobile operator may configure different services for consumer broadband, enterprise connectivity, and industrial applications.
5.7 Application Function (AF)
The AF represents application-level requirements to the 5G Core.
Its responsibilities may include:
Influencing policy decisions through the PCF.
Providing application information relevant to QoS.
Influencing traffic routing where supported.
Supporting application-aware connectivity services.
An AF may be deployed by a service provider or an authorized third party.
For example, a real-time application may communicate its service requirements so that the network can consider suitable QoS and routing policies.
5.8 Policy Control Function (PCF)
The PCF provides policy decisions for applicable network procedures.
Its responsibilities include:
Providing session-management policy information.
Supporting QoS and charging-related policy control.
Applying policies based on subscription and service information.
Supporting access and mobility-related policies where applicable.
Working with the SMF and other authorized network functions.
The resulting policies must comply with subscription permissions, operator configuration, available resources, and the capabilities of the deployed network.
5.9 Network Repository Function (NRF)
The NRF supports network function registration and service discovery.
It maintains information about registered network function instances and their offered services, helping authorized consumer functions discover suitable service providers.
The information may include network function identity, endpoint details, supported services, and relevant selection attributes.
For example, an NF can discover an available service instance through the NRF rather than relying entirely on a manually configured destination.
5.10 Network Exposure Function (NEF)
The NEF securely exposes selected network capabilities and information to authorized applications and third parties.
Its responsibilities include:
Exposing supported network APIs.
Supporting secure provisioning of external information.
Helping control access to network capabilities.
Supporting event exposure and application integration.
Enabling approved application-aware connectivity use cases.
For example, an enterprise application may use an authorized API to access a supported network capability, subject to operator policy, access controls, and security requirements.
5.11 Network Slice-Specific and SNPN Authentication and Authorization Function (NSSAAF)
The NSSAAF supports slice-specific authentication and authorization in applicable architectures.
It may interact with an external Authentication, Authorization, and Accounting (AAA) server and support authentication-related procedures for Standalone Non-Public Networks (SNPNs).
This function is relevant to deployments that require additional authorization procedures for network slices or non-public networks.
5.12 Service Communication Proxy (SCP)
The SCP supports indirect communication between network functions and their services.
Its responsibilities may include:
Forwarding requests to suitable service instances.
Routing messages between consumers and producers.
Supporting service discovery interactions.
Applying supported routing and communication policies.
An SCP can help simplify communication management in larger deployments. Its use depends on the selected architecture and implementation.
5.13 Edge Application Server Discovery Function (EASDF)
The EASDF supports edge computing and DNS-related procedures.
Its responsibilities include:
Processing DNS messages according to instructions from the SMF.
Exchanging DNS messages with the UE and DNS servers.
Reporting relevant DNS-related information to the SMF.
Supporting edge application discovery in applicable deployments.
For example, an application may be hosted at an edge location. Appropriate DNS handling and network policies can help the UE discover the correct application endpoint.
5.14 Network Slice Admission Control Function (NSACF)
The NSACF supports admission control for network slices.
Its responsibilities include:
Monitoring registered UE counts for a slice.
Monitoring established PDU session counts.
Supporting configured slice admission limits.
Providing relevant slice-status notifications to consumer network functions.
These controls help operators manage configured capacity limits and slice-level policies.
5.15 Unified Data Repository (UDR)
The UDR stores structured data used by relevant network functions.
Examples include subscriber-related data, policy information, and other structured records needed by the UDM, PCF, or associated functions.
The exact information stored depends on the standardized data model and implementation.
5.16 Unstructured Data Storage Function (UDSF)
The UDSF provides mechanisms for storing, modifying, and retrieving unstructured data when supported by the architecture and deployment.
It complements structured data management by providing storage capabilities for applicable use cases.
Summary of 5G Core Network Functions
Network Function | Main Responsibility |
AMF | Access, registration, and mobility |
UDM | Subscriber and subscription management |
AUSF | Authentication procedures |
SMF | PDU session management |
UPF | User-plane packet forwarding |
NSSF | Network slice selection |
AF | Application-level influence |
PCF | Policy control |
NRF | NF registration and service discovery |
NEF | Secure network capability exposure |
NSSAAF | Slice-specific and SNPN authentication support |
SCP | Indirect service communication and routing |
EASDF | Edge application discovery and DNS handling |
NSACF | Slice admission monitoring and control |
UDR | Structured data storage |
UDSF | Unstructured data storage |
The exact functions deployed depend on the supported features, network design, and applicable 3GPP release.
6. Important 5G Interfaces and Protocols
Understanding interfaces is essential for telecom engineers involved in call-flow analysis, interoperability testing, network integration, and troubleshooting.
Important 5G Interfaces
Interface | Connected Entities | Purpose |
N1 | UE and AMF | NAS signaling |
N2 | NG-RAN and AMF | Access and mobility control signaling |
N3 | NG-RAN and UPF | User-plane traffic |
N4 | SMF and UPF | User-plane control |
N6 | UPF and Data Network | External data-network connectivity |
N9 | UPF and UPF | User-plane forwarding between UPFs |
SBI | Authorized 5GC network functions | Service-based communication |
SBI is a general term for service-based interfaces rather than a single interface equivalent to N1 or N2.
Important Protocols in 5G
5G NAS: Handles UE-related registration, security, and session-management signaling.
NGAP: Supports control-plane signaling between the NG-RAN and AMF over N2.
HTTP/2 and service-based APIs: Support applicable service-based communication between 5GC network functions.
PFCP: Supports control of applicable user-plane functions over N4.
GTP-U: Commonly transports user packets over N3 and applicable N9 paths.
DNS: Supports domain-name resolution and relevant edge application discovery procedures.
For practical troubleshooting, engineers should correlate messages across multiple interfaces instead of analyzing individual signaling messages in isolation.
7. UE Registration and Authentication in 5G
UE registration is a fundamental procedure that allows a device to register with the network and establish the required context for receiving services.
The procedure may involve the UE, gNB, AMF, AUSF, UDM, and other relevant network functions.
Simplified UE Registration Procedure
Step 1: Registration Request
The UE sends a Registration Request through the NG-RAN toward the AMF.
Step 2: AMF Processing
The AMF processes the request and determines which additional procedures are required.
Step 3: Authentication
The AMF coordinates with the AUSF and relevant subscriber-data functions to perform the required authentication procedure.
Step 4: Security Establishment
The network establishes the required security context and obtains subscription-related information as applicable.
Step 5: Registration Completion
If the required checks succeed, the AMF sends a Registration Accept message. The UE may send Registration Complete when required by the procedure.
Actual signaling depends on UE state, security context, access type, and the applicable registration procedure.
Common Registration Failure Causes
Invalid or incorrectly provisioned subscriber information.
Authentication failures.
Access restrictions.
NAS security problems.
Network configuration issues.
Signaling failures between network functions.
Engineers should inspect NAS messages, registration rejection causes, and relevant AMF, AUSF, and UDM logs to identify the actual point of failure.
8. PDU Session Establishment in 5G
A registered UE generally requires a PDU session to exchange user data with an external data network.
Registration and session establishment are separate procedures. A device may be registered successfully but still lack working internet connectivity.
Simplified PDU Session Establishment Procedure
The UE sends a PDU Session Establishment Request using NAS signaling.
The AMF forwards the session-management request to the appropriate SMF.
The SMF checks relevant subscription information and policy requirements.
The SMF selects and configures a suitable UPF.
The network establishes the required user-plane path and QoS treatment.
The UE receives the applicable session acceptance and configuration information.
User packets can flow between the UE and the data network.
The complete procedure may include additional messages, resource allocation, access-network configuration, and security checks.
Example: Internet Connectivity Through 5G
When a user opens a website, the UE generates a packet destined for the website's server.
The gNB forwards the packet through the configured user-plane tunnel. The UPF applies the required forwarding rules, and the packet travels toward the data network through N6.
Return traffic follows the configured path back toward the UE.
The SMF manages session-related control, while the UPF handles user-plane traffic. This separation allows session policies and forwarding behavior to be managed independently of the actual packet-forwarding process.
Troubleshooting PDU Session Failures
Problem | Areas to Investigate |
UE registered but no internet | PDU session status, SMF logs, UPF selection |
Session rejected | NAS cause, subscription, DNN, S-NSSAI, policy |
IP address not assigned | Session type and addressing configuration |
Session active but packets fail | N3 tunnel, UPF rules, N6 routing, DNS, firewall |
Poor application performance | QoS, congestion, routing, packet loss, latency |
These are initial investigation points. The correct diagnosis depends on signaling evidence, configuration, and packet traces.
9. Network Slicing and Edge Computing in 5G
Network slicing and edge computing are important capabilities supported by the 5G Core architecture.
What Is Network Slicing?
Network slicing allows shared physical infrastructure to support logically differentiated networks for different services or customers.
A network slice can be designed around particular service requirements, such as enterprise connectivity, industrial applications, or consumer broadband.
Potential use cases include:
Consumer mobile broadband.
Enterprise private connectivity.
Industrial automation.
IoT deployments.
Specialized communication services where supported.
The NSSF contributes to slice selection, while subscription permissions, policies, access-network configuration, and other network functions help implement the overall service.
Network slicing does not necessarily require completely separate physical infrastructure. Its isolation and performance characteristics depend on the deployment design.
What Is Edge Computing?
Edge computing places application processing closer to users and connected devices.
By reducing the distance between an application and the device communicating with it, edge computing can help reduce latency and support local data processing.
The EASDF supports relevant edge application discovery procedures. The SMF and UPF can also contribute to routing traffic toward suitable local data networks.
For example, a factory may process camera feeds using an application deployed locally instead of sending every video stream to a distant central data center.
The actual benefits depend on radio conditions, transport networks, application placement, routing, and local computing resources.
10. Difference Between 5G Standalone and Non-Standalone
5G networks can be deployed using Standalone (SA) or Non-Standalone (NSA) architectures.
5G Non-Standalone (NSA)
In common NSA deployments, 5G NR works alongside LTE, with the LTE/EPC architecture providing the anchor for connectivity.
This approach allows operators to introduce 5G NR while continuing to use existing LTE infrastructure.
5G Standalone (SA)
In SA deployments, 5G NR connects to the 5G Core Network.
This provides the architectural foundation for native 5GC capabilities such as network slicing, advanced policy control, service exposure, and integration with edge computing.
5G SA vs. NSA Comparison
Feature | 5G NSA | 5G SA |
Core network | Commonly LTE/EPC anchored | 5G Core |
Radio access | LTE combined with NR in common deployments | NR with 5GC |
Deployment approach | Builds on existing LTE infrastructure | Requires suitable 5GC deployment |
Native 5GC capabilities | Depend on deployed architecture | Supported by the 5GC architecture |
Network slicing | Not equivalent to native 5GC-based slicing | Supports 5GC-based slicing |
Migration strategy | Can enable an earlier 5G rollout | Enables a native 5GC-based architecture |
Advanced capabilities are not automatically available simply because a network uses SA. They must also be implemented, configured, and supported by the relevant devices and services.
11. Practical Applications of 5G Core Network Functions
The 5G Core supports a wide range of applications across consumer, enterprise, industrial, and research environments.
Smart Manufacturing
Factories can use 5G connectivity for connected machinery, monitoring systems, robotics, and industrial IoT applications.
Network policies, local data processing, and appropriate QoS configurations can help support application requirements.
Private 5G Networks
Enterprises, campuses, factories, and research institutions can deploy private mobile networks to provide controlled connectivity for authorized users and devices.
Depending on the implementation, private 5G can support industrial monitoring, asset tracking, automation, and secure enterprise applications.
Edge Computing
Edge computing supports applications that benefit from processing data closer to the source, such as video analytics, industrial control applications, and connected-device services.
Connected Vehicles
5G networks can support vehicle connectivity, fleet-management applications, telematics, and other connected-transport use cases, subject to the relevant service and network requirements.
IoT Connectivity
5G-related technologies support different IoT deployment requirements, from large numbers of connected sensors to devices requiring higher throughput or more demanding service characteristics.
Telecom Research and Development
Universities, engineering colleges, and research institutions can use 5G test environments to study registration, PDU sessions, network behavior, protocol signaling, and interoperability.
These applications demonstrate why understanding 5G Core functions is important for telecom engineering and research.
12. 5G Core Network Troubleshooting
Practical troubleshooting requires more than memorizing the names of network functions. Engineers need to understand the complete signaling sequence, inspect traces, and correlate evidence across the core and access network.
Scenario 1: UE Registration Rejection
If a UE repeatedly fails to register, engineers should review the Registration Request, Registration Reject cause, NAS security procedures, subscriber provisioning, and authentication-related exchanges.
Relevant functions may include the AMF, AUSF, and UDM.
Scenario 2: PDU Session Establishment Failure
If registration succeeds but session establishment fails, engineers should inspect the PDU Session Establishment Request and response, SMF decisions, DNN configuration, S-NSSAI, subscription information, and applicable policy procedures.
Scenario 3: Session Established but No Data Traffic
If a PDU session is active but the UE cannot access an application, engineers should examine UPF selection, N3 tunnel configuration, packet-forwarding rules, N6 routing, DNS, and firewall settings.
Scenario 4: Poor QoS or Throughput
Poor performance may be caused by radio conditions, congestion, packet loss, routing, transport latency, or incorrect QoS configuration.
Engineers should correlate radio measurements, core-network logs, packet captures, and application-level measurements before concluding that the core network is responsible.
Recommended Practical Exercises
Analyze UE registration and authentication call flows.
Study PDU session establishment and release.
Identify N1, N2, N3, N4, and N6 interfaces.
Correlate signaling messages with packet captures.
Explore a suitable 5G Core test environment.
Identify rejection causes and the first point of failure.
Study the effect of DNN, S-NSSAI, and QoS configuration.
Practice systematic troubleshooting using logs and traces.
These activities help bridge the gap between theoretical understanding and real-world telecom engineering.
13. Skills Required for 5G Core Network Engineers in 2026
As mobile networks evolve toward cloud-native architectures, private 5G, network automation, and more advanced 6G-related research, engineers benefit from combining protocol knowledge with practical technical skills.
Protocol and Signaling Knowledge
Engineers should understand:
5G NAS and registration procedures.
NGAP and NG-RAN signaling.
PDU session establishment and release.
PFCP and GTP-U fundamentals.
QoS flow and policy procedures.
5G SA and NSA architecture.
Core Network Knowledge
Important areas include:
AMF, SMF, UPF, PCF, UDM, AUSF, and NRF.
Network slicing and DNN configuration.
User-plane routing and packet forwarding.
Subscriber management and authentication.
Session control and troubleshooting.
Cloud and Automation Skills
Modern telecom engineering can also benefit from knowledge of:
Linux and IP networking.
Containers and Kubernetes.
Service-based interfaces and API testing.
Python scripting and log automation.
Network monitoring and performance analysis.
Career Opportunities
Professionals with relevant knowledge and practical experience may pursue roles such as:
5G Core Network Engineer.
Telecom Protocol Testing Engineer.
5G Integration and Validation Engineer.
Core Network Operations Engineer.
Network Automation Engineer.
Private 5G Engineer.
Telecom R&D Engineer.
Interoperability and Performance Testing Engineer.
Job requirements vary according to employer, experience level, and the technologies used in a particular network.
14. 5G Training and Certification with Apeksha Telecom
For engineers who want to move beyond theoretical knowledge, structured training can help develop practical expertise in core network architecture, signaling procedures, protocol analysis, and troubleshooting.
Apeksha Telecom and Telecom Gurukul are relevant starting points for professionals exploring telecom training and technical learning opportunities.
A practical 5G learning program should ideally cover the following topics:
5G architecture and core network fundamentals.
5G NAS and NGAP procedures.
AMF, SMF, UPF, PCF, UDM, and AUSF interactions.
PDU session establishment and release.
Protocol testing and log analysis.
Network slicing and QoS.
Cloud-native core fundamentals.
Practical troubleshooting using signaling traces.
Network automation and scripting fundamentals.
Hands-on lab exercises are especially valuable because they allow learners to observe how signaling messages, configuration parameters, and network functions interact during actual procedures.
Explore Telecom Training Resources
Visit the following websites to explore relevant courses, technical resources, and training opportunities:
Telecom Gurukul: https://www.telecomgurukul.com/
Apeksha Telecom: https://www.apekshatelecom.com/
Check the official websites for current course availability, curriculum, lab access, fees, and certification details.
15. Frequently Asked Questions About 5G System Architecture
What is 5G System Architecture?
5G System Architecture describes how the UE, 5G access network, and 5G Core work together to provide connectivity, mobility management, authentication, session control, and user-data transport.
What are the three main components of a 5G System?
The three main components are User Equipment (UE), the 5G access network, and the 5G Core Network (5GC).
What is Service-Based Architecture in 5G?
Service-Based Architecture enables authorized 5G Core network functions to provide and consume services through standardized service-based interfaces. It supports modularity, service discovery, and flexible deployment.
What is the difference between AMF and SMF?
The AMF manages access, registration, NAS signaling, and mobility-related procedures. The SMF manages PDU sessions, including establishment, modification, release, and user-plane control.
What is the role of UPF in 5G?
The UPF handles user-plane packets, applies configured forwarding and QoS rules, and connects the access network to data networks through the relevant interfaces.
What is the difference between UDM and AUSF?
The UDM manages subscriber and subscription-related information and supports authentication procedures. The AUSF performs its designated role in network authentication, working with the AMF and relevant subscriber-data functions.
What does the NRF do in a 5G Core?
The NRF supports network-function registration and service discovery, helping authorized consumer functions discover suitable network-function instances and their services.
What is the role of PCF in 5G?
The PCF provides policy decisions that influence applicable network procedures, including QoS, session handling, and other policy-controlled behavior.
How does network slicing work in 5G?
Network slicing allows shared infrastructure to support logically differentiated services. The NSSF supports slice selection, while other core and access-network functions implement the required policies and configurations.
What is the difference between 5G SA and NSA?
NSA commonly combines 5G NR with an LTE/EPC anchor, whereas SA uses 5G NR with the 5G Core. SA provides the architectural foundation for native 5GC capabilities.
Why is EASDF important in 5G?
The EASDF supports DNS processing and edge application discovery procedures, helping UEs discover suitable application endpoints in supported edge-computing deployments.
Which skills are important for a 5G Core engineer?
Important skills include 5G NAS, NGAP, PFCP, GTP-U, core network functions, PDU session procedures, packet analysis, Linux, IP networking, and troubleshooting.
16. Conclusion
The 5G System Architecture represents a major evolution in mobile network design. Its service-based approach makes the core more modular and supports flexible deployment, cloud-native implementations, network slicing, edge computing, and application-aware connectivity.
Understanding individual network functions is important, but understanding how they interact is even more valuable.
The AMF coordinates access and mobility procedures, the SMF manages sessions, the UPF forwards user traffic, the UDM and AUSF support subscriber and authentication procedures, and the PCF contributes policy decisions. Other functions, including NRF, NEF, NSSF, EASDF, NSACF, UDR, and UDSF, provide additional discovery, exposure, slicing, edge, admission-control, and data-storage capabilities.
For telecom students and working engineers, the next step is to connect these concepts with real signaling flows, protocol traces, and hands-on lab exercises. Practical understanding can help build the skills needed for 5G Core testing, integration, operations, and research.
If you want to develop your knowledge of 4G, 5G, and emerging 6G technologies, explore relevant learning resources from Apeksha Telecom and Telecom Gurukul and focus on building both protocol fundamentals and practical troubleshooting skills.
References and Further Reading
3GPP TS 23.501 — System Architecture for the 5G System: https://www.3gpp.org/dynareport/23501.htm
3GPP TS 23.502 — Procedures for the 5G System: https://www.3gpp.org/dynareport/23502.htm
3GPP TS 29.500 — Technical Realization of Service-Based Architecture: https://www.3gpp.org/dynareport/29500.htm
Ericsson 5G Core: https://www.ericsson.com/en/core-network/5g-core
O-RAN Alliance Specifications: https://www.o-ran.org/specifications
Telecom Gurukul: https://www.telecomgurukul.com/
Apeksha Telecom: https://www.apekshatelecom.com/
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