Termins

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4G and 5G networks are different.

Each 4G base station has a BBU and is directly connected to the core network through the BBU. In 5G networks, access networks no longer consist of BBUs, RRUs, and antennas. Instead, it is reconstructed into the following three functional entities: a CU (Centralized Unit, centralized unit), a DU (Distribute Unit, distributed unit), and an AAU (Active Antenna Unit, active antenna unit). The original 4G RRUs and antennas are combined into an AAU, and the BBU is divided into CUs and DUs. The DUs are deployed at the AAU. One CU can be connected to multiple DUs.

4G has only two parts: fronthaul and backhaul. On a 5G network, there are three parts. The part where the AAU connects to the DU is called 5G fronthaul, and the part where the DU connects to the CU is middlehaul. Backhaul (Backhaul) is a communication bearer between a CU and a core network.