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About Caltta 5G | Key Technologies of 5GC

What is 5GC?

5GC is short for 5G core network (5G Core).

The 5GC network architecture is shown as follows:

Dmr Internet Radio

Corresponding to the above figure, the main network function modules in 5GC are shown as follows:

Network Function

External Service


Function Description



Perform mobility management, NAS’ MM signaling processing, NAS’ SM signaling routing, security anchor point and security context management, etc.



Perform session management, UE IP address allocation and management, UP selection and control, etc.



Manage and store subscription data and authentication data



Perform different user plane processing



Perform identity authentication function for user access



Perform Slice selection



Maintain the information of deployed NF and process NF discovery requests from other NFs

Compared with the familiar network elements in 4G LTE, we can better understand the network functions in 5GC:

5G Network Functions

Compared with 4G Network Elements


RAN / eNodeB


NAS access control function in MME, terminate NAS signaling of AM layer, relay NAS signaling of SM layer


Control plane function of session and bearer management in MME & SGW & PGW, to terminate NAS signaling of SM layer


Authentication function in MME


The user plane function in SGW/PGW, corresponding to the  SGW-U and PGW-U in CU separate architecture






PDN, data network

What are the key technologies of 5GC?

Based on the Network Function Virtualization (NFV) and Software Defined Network (SDN) technologies, 5GC uses the following 4S technologies (SBA, Slice, CUPS, and Stateless) to provide 5G network functions.

Service Based Architecture (SBA) of Caltta 5G PMR Radios

The 5GC adopts the SBA microservice architecture which evolves the single-NE multi-function feature in the LTE core network to the multi-NE multi-function feature in the 5GC.

Dmr Ht Radio

With the SBA, the 5GC enables decoupling and integration of network functions, that is, the network function services can be independently expanded or evolved, and deployed on demand.

The function services use the service registration and discovery mechanism to achieve plug-and-play and automated networking of network functions in the 5GC. A service can be called by multiple NFs, improving service reusability and simplifying service process.

Service process of 5GC network modules:

1) Service registration

The NF registers the supported service list to the NRF.

The NF can update and deregister services in the NRF on demand.

2) Service discovery

Service consumers can query the required NF and service list through the NRF.

The NRF only returns the authorized NF and service list.

3) Service authorization

The service provider or NRF determines whether a service consumer is authorized to call or discover a service.

Dmr Hf Radio


Slice refers to the division of the operator's physical network into multiple virtual networks. Each virtual network is divided based on the service requirements, such as latency, bandwidth, security and reliability, to adapt to different application scenarios.

Dmr Handheld Radio

Specifically, the major application scenarios of 5G networks are as follows:

1) Mobile broadband

The application of ultra-high-definition video, holographic technology, Augmented Reality (AR), and Virtual Reality (VR) poses high requirements on the network bandwidth and speed.

2) Massive Internet of Things

A large number of Internet of Things (IoT) sensors are deployed intensively in the measurement, construction, agriculture, logistics, smart cities, and home scenarios. These sensors are densely and largely deployed, mostly are fixed, with low requirements on latency and mobility.

3) Mission-critical Internet of Things

When used in fields of unmanned driving, Internet of Vehicles, automatic plants, and telemedicine, the 5GC requires ultra-low latency and high reliability.

Dmr Handheld Ham Radio

Control and User Plane Separation (CUPS)

It originates from the idea of separating the control plane from the data plane of SDN (Software Defined Network). The communication core network has always been evolving toward separation of the control plane and user plane. The purpose is to enable deployment of the network user plane in both the central data center and the access network (edge data center), thus achieving distributed deployment.

Dmr Handheld

As the content can be deployed and distributed on the access network (edge data center) which is closer to users, the data transmission latency and network backhaul load are reduced. Only in this way can the millisecond-level latency of the 5G network be achieved.

This type of separation is critical for applications such as Internet of Vehicles. In this solution, the network operator deploys the EPC user plane in the urban data center so that it is closer to the applications, thereby reducing latency. This solution also applies to high-bandwidth applications like video. Because the core user plane is closer to end users, operators do not need to send the data back to the central service node. This reduces the cost of network deployment and improves the speed of application access.


The stateless Service refers to the processing of a single request and does not depend on other requests.

Based on the stateless service, the 5GC can easily be scaled and enable horizontal expansion through load balancing and other means.

Moreover, uninterrupted 5G network services are provided to ensure the continuity of user network access.

Conventional Radio System

Trigger Scenarios

Scenario 1: Manually triggered by AMF1 maintenance

Scenario 2: Automatically triggered in case of AMF1 fault

AMF1→New AMF traffic migration process

The AN reselects the AMF and creates new UE N2 association.

The new AMF restores user context from the UDSF and updates N2 association to the AN without impact on N3.

The AMF interacts with the peripheral CP NFs to update AMF associations.

What are the improvements of 5GC over EPC?

UE Security

User SUPIs are encrypted and air interface information is transmitted in the form of SUCI to ensure UE security.

Conventional Radio

The two-factor authentication reduces masquerading of visiting AMF in the roaming scenario.

AMF authentication on UE

AUSF authentication on UE

Dmr Conventional Networked

Session Management of Caltta 5G PMR Radios

Separation of mobility management and session management

Separation of control plane and user plane

Compared with 4G EPC, the 5G has been enhanced in the following aspects:







5G cancels the bearer definition and introduces a QoS flow with finer granularity.

N3 GTPU tunnel: it changes from bearer level to PDU session level, and the packet header encapsulates QoS Flow ID (QFI).





5G introduces the concept of SSC (Service and Session Continuity) mode, supporting Anchor UPF (PGW) change process

UL-CL Session Model



Easy to support LADN (Local Area Data Network)


home Session Model



Easy to support LADN and SSC mode 3

Secondary Authentication of PDU Session



During PDU session establishment, the DN-AAA server performs secondary authentication on the session, enhancing AF's session control

QoS Improvement

End-to-end LTE needs multiple dedicated bearers to provide UEs with services of different QoS guarantee levels. Its granularity is the EPS bearer.

The concept of bearer is replaced by QoS flow in the 5G network based on the requirement of fine QoS control of services.

A QoS flow ID (QFI) identifies only one QoS flow and is unique in a PDU session.

The mapping between flow and DRB is described. The 5G QoS is guaranteed by controlling the QoS flow, which can be preconfigured or maintained through the PDU session establishment/modification process.

Trunked Vs Conventional Radio

EPC/5GC Fusion

The 5GC can interoperate with 4G LTE EPC based on the following fusion strategies:

Fusion of UDM+HSS: unified subscription management

Fusion of PCF+PCRF: unified policy management

Fusion of SMF+PGW-C: unified session management anchor

Fusion of UPF+PGW+U: unified user plane tunnel anchor

The AMF supports N26 Interoperation interfaces.

Trunking Radio System Vs Conventional

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