What are the key RAN components and functions in a 5G network?

The Radio Access Network (RAN) serves as a critical component in a 5G network, connecting user devices to the core network. My experience highlights the pivotal role of RAN in delivering high-speed, low-latency connectivity, crucial for applications like augmented reality and IoT.

O RAN é a interface entre os dispositivos móveis (smartphones, CPEs, sensores etc.) e a esta??o rádio base, formada principalmente pelas antenas e unidade de rádio (Lte-eNB/5G-gNB). Esses componentes conectam os endpoints ao acesso a internet ou a aplica??es. Essa interface também possuí fun??es de gest?o dos recursos de RF, como frequência, largura de canal, potência, aloca??o de subcarrier, elementos ID de área, dentre outros. Em minha experiência, o RAN é uma parte crucial para em solu??es de redes privativas, seja 4G ou 5G. No projeto, devemos considerar a largura de banda esperada, no de usuários conectados, área de atendimento, e outros requisitos.

The CU is actually the Centralized Unit, and it can be split in two, the CU-CP for the Control Plane, and the CU-UP for the User Plane. And the gNB, the 5G RAN node actually includes all 3 elements: the Radio Unit (RU), the Distributed Unit (DU) and the Centralized Unit (CU).

he 5G RAN is comprised of three key components: the user equipment (UE), the gNodeB (gNB), and the distributed unit (DU). Drawing from my experience, the UE, representing devices like smartphones or tablets, forms the interface between users and the network. The gNB, serving as a base station or cell, plays a pivotal role in connecting users to the network. The innovative architecture involves a DU that can be co-located or separated from the central unit (CU). The CU manages control plane functions like authentication, while the DU handles user plane functions, including data processing and transmission. This distributed architecture enhances flexibility, scalability, and overall network efficiency.

Radio resource control (RRC) establishes and maintains UE-gNB connections, configuring parameters and security. Radio link control (RLC) manages data packet segmentation, reassembly, and delivery between UEs and gNBs. Medium access control (MAC) allocates radio resources, controlling data access and transmission on the physical layer. In the PHY layer's role in converting data into radio signals using modulation, coding, and beamforming techniques. These functions collectively ensure efficient and reliable wireless communication in a 5G RAN.

The 5G RAN architecture defines the interconnection of RAN components and their interaction with the core network. Designed to be flexible and scalable, it accommodates various deployment scenarios and use cases. The architecture offers two main options: non-standalone (NSA) and standalone (SA). NSA mode leverages the existing 4G LTE network for control functions, while SA mode enables a fully independent connection to the 5G core network. The adaptive nature of 5G RAN architecture is crucial for navigating the complexities of evolving network deployments.

Fronthaul refers to the network that connects remote radio heads to BBUs many kilometers away, while Midhaul refers to the link between the DU and CU, and finally the Backhaul is representing the link between the CU and the core network.

The 5G RAN interfaces, standardized by 3GPP, establish logical connections facilitating data and control information exchange between RAN components. Key interfaces include Uu, the air interface connecting UE and gNB, carrying user data and signaling messages. Xn, the inter-gNB interface, coordinates handovers across cells. F1, the fronthaul interface between CU and DU, facilitates data and control exchange in centralized-distributed gNB parts. Ng, the backhaul interface between gNB and 5G core network, connects RAN to network services. These interfaces, integral to 5G functionality, ensure seamless communication and coordination within the RAN architecture.

It is equally important to consider other streams of 5G to diversify as well to explore the true potential of 5G which are gaining some momentum in recent times - 5G open ran, 5G private networks, RIC solution, redcap and 5G advance use cases of AI/ML.