The Huawei BTS3900 is a series of base transceiver stations BTS used in wireless communication networks. Within the BTS3900 series, there are several modules with different functionalities.

The HUAWEI CRFU module stands for Common Radio Frequency Unit. It is responsible for handling the radio frequency RF functions in the base station, including signal transmission and reception.

The MRFU module stands for Multi-Mode Radio Frequency Unit. It is a versatile module capable of supporting multiple wireless communication standards, such as GSM, UMTS, and LTE. The MRFU provides flexibility in network deployments by accommodating different technologies within a single base station.

The CRFU module stands for Grouped Radio Frequency Unit. It is similar to the HUAWEI CRFU but designed for grouped base station configurations, where multiple RF units are combined into one group and connected to the BBU.

It is used in distributed base station configurations, where the baseband processing unit BBU is separated from the RF unit. The DRFU handles the RF functions and connects to the BBU via fiber optic cables.