IPLOOK 4G/5G Core Network

Virtualized 5GC, EPC and IMS

What is 4G Core Network and 5G Core Network?

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  • Jimmy at
  • August 10, 2020

4G core network
The core network is located in the center of network data exchange and is mainly responsible for EU mobility management, session management and data transmission. There are mainly 4 NE in 4G core network -- MME, SGW, PGW, HSS.

4G core network

Mobility Management Entity(MME) is the core element of 4G core network. As the name implies,it is mainly responsible for mobility management and control, including user authentication, paging, location update and switching, etc. In short, the phone must regularly report its location to MME, go through MME security if it wants to access the Internet, and coordinate the switch if the phone goes to another base station. MME is the general manager to command overall arrangements.
Service Gateway (SGW) is equivalent to the data relay station which mainly responsible for the management of the mobile phone context session and the routing and forwarding of packets.
Packet Data Network Gateway (PGW) is mainly responsible for connecting to the external network. If the mobile phone wants to access the Internet, it must have the permission from PGW. In addition, PDW is also responsible for the mobile phone session management and load control, IP address allocation, billing support and other functions.
Home Subscriber Server (HSS) is a central database that contains user-related information and subscription-related information.

However, there are some drawbacks to this architecture. The control side and the user side are not completely separated. As mentioned above, SGW and PGW should not only deal with the forwarding user plane data, but also be responsible for the control plane functions such as session management and load bearing control. Such disadvantages of interweaving user plane and control plane lead to complex business changes, difficult efficiency optimization, and difficult deployment, operation and maintenance.

Besides, although the CUPS is a good architecture, it grew out of the 4G core which was born only for high-speed Internet access on mobile phones and applicable only for the eMBB scenario for 5G. This architecture is not flexible enough to support diversified 5G services. Therefore, a new core network architecture is needed urgently.

5GC--caterpillar's metamorphosis into a mature butterfly.

5G core network.vsdx

After painstaking research by industry experts, they decided to adopt service-oriented architecture (SBA) to embrace virtualization, separation of control and user surface, separation of computing and storage. It fully support network slice and open the interface to the third party. In short, this is a complete transformation.
Thus, the hardware-related terms such as "entity", "server" and "gateway" disappeared in the 4G core network. The virtualized network no longer focused on the underlying hardware. Those intricate software functional modules are all rebuilt and transferred into a series of Network functions(NF) in a software sense.
Each network function is logically equivalent to a network element, and these functions are completely independent and autonomous. When we upgrade or expand capacity for these NF, they will not affect each other, which provides great convenience for the maintenance and expansion of the network.
It’s like a caterpillar melting itself and morphing into a butterfly. It's a complete metamorphosis.

Now let's look at how all this has happened. From caterpillars to butterflies, the basic functions of movement, circulation and digestion have been reorganized, but they still grow out of the "imaginal disc" that has been incubated in the caterpillar for a long time.The changes of 5G core network are the same. The strange network function (NF) is actually like the imaginal disc in caterpillar. With the call of the The times, it absorbs the nutrients of the evolution of 4G core network, grows rapidly and finally emerges from the cocoon.

A comparison between 4G and 5G - What changes have taken place in pupae?
We can find the shadow of the 4G core in most 5G NF, just as we can find the "imaginal disc" of butterflies in caterpillars. As shown in the figure below, the functions responsible for access and mobility management in MME are independent and become 5G AMF. At the same time, the part responsible for session management in MME is extracted and that part combines with SGW-C and PGW-C into SMF. The model for the function of session management changed from decentralized management to the current professional and centralized management.
Besides, the function of user authentication in MME and HSS was extracted and merged into 5G AUSF. At the same time, the remaining user data management functions in HSS become UDM independently and cooperate with AUSF to complete the processing related to user authentication data.
In addition to these 4G heritage features, the 5G core network also introduces some completely new network functions NF, mainly including NSSF, NEF and NRF.
As for the user plane, the two control plane network elements, SGW-U and PGW-U of 4G CUPS, are combined into one to become the user plane function of 5G. That is UPF.

Seeing from the above changes, 5G core network is very complex. From the design of architecture to the final maturity of commercial use, there is still a long way to go. After such a great transformation, 5G core network is now accumulating strength. It will lead 5G into a new era in the near future. 
IPLOOK has been dedicated in core network for more than 8 years. We used to be a caterpillar in the past. However, we have already completed the metamorphosis into a mature butterfly which is full of vitality and confidence. IPLOOK not only can provide mature EPC product, but also has perfect 5GC, which can be witnessed by our customers at home and aboard.