# The difference between 4G and 5G:
### 1.RAN(radio access network) base station:
4G:
It is composed by BBU(Baseband Unit), RRU(Remote Radio Unit), feeder line and antennas.
5G:
It is composed by BBU, AAU and feeder line.
### 2. Antenna unit:
4G: Antennas+RRU(Remote Radio Unit)
5G: AAU(Active Antenna Unit)
### 3. BBU:
5G:
* Composed by CU(Centralized Unit) and DU(Distribute Unit), BBU is responsible for communication through the physical interface.
* DU is responsible for real time L1 and L2 scheduling functions.
* CU is responsible for non-real time, higher L2 and L3.

:::warning
**Glossary**
>**Core Network**: it is the central element of network that provides services to custmers who are connected by the access nework, one of the main function is to route telephone calls across the public switched telephone network(PSTN)
>**RAN**: it is a type of network infrastructure used commonly for mobile networks that consist of radio base stations with large antennas. A RAN wirelessly connects user equipment to a core network.
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