The BBU5900 uses a modular design.

Control subsystem: It is responsible for managing and controlling the overall operation of the BBU, it provides functions such as system initialization, software management, and alarm management.

Transmission subsystem: It is responsible for the transmission of data between the baseband subsystem and the RF subsystem, it includes functions such as data encoding, modulation, and multiplexing.

Baseband subsystem: It performs the baseband processing for the BBU, it includes functions such as demodulation, decoding, and demultiplexing.