Cloud + 5G = A perfect mesh
Episode 2: The flexible bones
5G cloud-native architecture determines that is not just 4G+1G. Compared with the previous generations of mobile infrastructure, 5G has brought innovative changes, produce new business models and benefits.
The design of the 5G architecture fully adopts and combines the technologies of cloud architecture and cloud computing, enabling the 5G system to greatly improve communication capabilities while also having flexibility.
Flexibility of what? Well, a traditional “rigid network” usually connects fixed network elements, and a 5G “flexible network” can be dynamically adjusted, i.e. it could adapt to customer needs, even automatically scale-out and scale-in based on traffic pattern. In other words, it will lift the burden of monitoring, the worry of congestion, and the cost of redundant capacity for peak hours.
Sounds puzzling? Let’s demystifier the 5G architecture.
CORE
The main change of the 5G network architecture is on the core side as 5G network elements become cloud-native NFV which can be deployed in the cloud.
3GPP introduced cloud-native and SBA (Service-Based Architecture) which abstracts 5G network functions and forms a highly cohesive, independent, and manageable function unit, the service. Those services are small and use a standardized external interface, so upgrading one of the services will not affect other NFVs.
Now, 5G network functions can be built on the cloud, but to form a tangible and robust infrastructure will involve the coordination between network elements, cloud resources, and network resources. The traditional/manual deployment method is long, inefficient, and prone to human errors. For example, deploying an “IMS+EPC” system in the data center would take more than a month if everything goes well.
The orchestrator(Kubernetes :P) and SDN controller can achieve automatic network configuration and deployment, hence greatly improving the efficiency of service deployment. The deployment cycle of the same “IMS+EPC” system will be shortened to days or even hours. Amazing! :)
Cloud-native makes the Teco infrastructure can be sufficiently elastic to accommodate customer demand.
Another benefit of cloud-native 5G core is NFV and SDN technology enables the cross-data-center and hybrid/multi-cloud by unified orchestration, which makes the 5G network slicing and NaaS(network as a service) possible.
Through network slicing, edge computing, low-latency, and large connections, the network is transformed from generalized services to personalized and customized services.
5G SBA reconstructs the control plane based on microservices and makes the upper-layer network functions conform to the underlying cloud computing infrastructure.
This means customizing network functions are like playing Lego: Let small service modules form a systematic network architecture on demand. These service modules divide the business logic according to the three principles: “self-contained, reusable, and independent life cycle management”.
The SBA of the 5G core network architecture is a disruptive change in the 5G era. It has the advantages of flexibility, orchestration, decoupling, and openness that are unmatchable by 4G network architectures.
RAN
The 5G network architecture changes also happened on the RAN side, that is, the separation of CU-DU (centralized unit-distributed unit) to achieve more flexible networking and more centralized control.
The architecture of the wireless system has undergone a series of changes in 3G, 4G, and 5G. In 3G era, the core controls the base station through an RNC (Radio Network Controller) node. In 4G era, in order to reduce the delay, the RNC node is removed and the base station is directly connected to the core. In 5G era, the CU-DU network architecture is introduced since new requirements such as ultra-low latency emerged.
The CU is responsible for completing the low real-time & high-level protocol stack [RRC (Radio Resource Control) and PDCP (Packet Data Convergence Protocol) layer], and the DU is responsible for completing the high real-time & low-level protocol Stack [RLC (radio link layer control), MAC, PHY, RF layer]．
When CU and DU are co-located, you can only choose equipment from the same manufacturer. When the CU and DU are deployed separately, the CU and DU may use equipment from different manufacturers.
Further separation of CU into CP and UP
In traditional mobile infrastructure, network functions have both a control plane and a user plane. With the rise of SDN technology, when designing 5G architecture, this architecture has been changed.
The separation of the control plane and the user plane makes 5G networks have advantages in two ways: centralized deployment of the control plane will provide centralized management and control, simplified user plane function will provide flexible deployment and efficient forwarding.
For example, the functions of session management scattered among multiple network elements in a 4G network are stripped out, integrated together and evolve into 5G session management function.
The separation of the control plane and the user plane makes it possible to further flatten the network architecture which has been evolved from 4 Layers in 2G/3G to 3 Layer 3 in 4G era.
When it comes to 5G, the data traffic from the base station can be directly transmitted to the user plane gateway. A flatter architecture brings shorter paths, lower latency, and higher efficiency to the network.
