Advanced baseband technology in third-generation radio base stations
Zhongping Zhang, F. Heiser, Jürgen Lerzer, Helmut Leuschner · 2003
The functionality of a radio base station (RBS) is divided into two main parts: userplane functions and control-plane functions. The user-plane functions are associated with transport, baseband, radio and the antenna. The control-plane functions pertain to the transmission of user data and operation and maintenance (O&M) data. Ericsson’s RBS is based on the connectivity packet platform (CPP, formerly called Cello packet platform)—that is, the RBS employs the infrastructure of hardware and software modules provided in CPP. Figure 1 shows a typical indoor RBS with power subrack, baseband subrack, radio frequency subrack and power amplifier subrack. User-plane signals from the radio network controller (RNC) via the Iub interface are input directly via CPP boards to the baseband parts, whereas control-plane signals are input to the baseband parts via the traffic and O&M control parts of the main processor. Figure 2 shows the architecture of the Ericsson RBS3000. Please note that for simplicity’s sake the CPP parts and main processor are not shown. The architecture can be broken down into a cell-specific part and a non-cell-specific part. The cell-specific part contains transceiver (TRX) boards, multicarrier power amplifier (MCPA) boards and antenna interface unit (AIU) boards, whereas the common part contains boards for baseband processing. In Figure 2, the baseband processing has been split between the transmitter (TX) and random access and receiver (RAX) boards. The TX board handles downlink processing and enables coding, spreading and modulation. The RAX board handles uplink processing and enables demodulation, de-spreading and decoding.