Logically, the BSC interface processing subsystem consists of the following units: Abis interface processing unit, A interface processing unit, Ater interface processing unit, Pb interface processing unit, Gb interface processing unit, and Cb interface processing unit.
Figure 1 shows the BSC interfaces.
As shown in Figure 1, the BSC is connected to the MSC/MGW over the A interface, to the BTS over the Abis interface, to the PCU over the Pb interface, to the SGSN over the Gb interface, and to the CBC over the Cb interface. The GMPS/GEPS is connected to the GTCS over the Ater interface.
NOTE: Based on the types of the PCU and the configuration modes of the BSC subracks, the BSC provides the following interfaces:
- When the built-in PCU is used, the BSC provides the Gb interface.
- When the external PCU is used, the BSC provides the Pb interface.
- In BM/TC separated configuration mode, the BM and the TC communicate with each other over the Ater interface.
Abis Interface Processing Unit
The BSC and the BTS communicate with each other over the Abis interface. The Abis interface processing unit can be the GEIUB/GOIUB, GFGUB/GOGUB, GEHUB. The Abis interface processing unit performs the following functions:
- Provides E1/T1 electrical ports, STM-1 optical ports, FE/GE electrical ports, and GE optical ports.
- Receives and transmits the signaling and traffic signals between the BSC and the BTS
- Converts internal protocols
- Processes HDLC and IP protocols
- Forwards signaling to the service control subsystem
- Forwards traffic signals to the service processing subsystem
A Interface Processing Unit
- Provides E1/T1 electrical ports, STM-1 optical ports, FE/GE electrical ports, and GE optical ports.
- Receives and transmits signaling and traffic signals between the BSC and the MSC/MGW
- Converts internal protocols
- Performs the IP protocol processing if IP transmission is used over the A interface, and performs the MTP2 protocol processing if the BM and the TC are configured in the same subrack.
- Forwards the signaling from the core network to the GE switching subsystem
- Forwards the traffic signals from the core network to the GE switching subsystem or to the TDM switching subsystem
Ater Interface Processing Unit
- Provides E1/T1 electrical ports and STM-1 optical ports
- Receives and transmits signaling and traffic signals between the BM subrack and the TC subrack
- Processes HDLC and PPP protocols
- Processes the MTP2 protocol
- Forwards signaling to the GE switching subsystem
- Forwards traffic signals to the TDM switching subsystem
Pb Interface Processing Unit
- Provides E1/T1 electrical ports and STM-1 optical ports
- Receives and transmits signaling and traffic signals between the BSC and the PCU
- Forwards signaling to the GE switching subsystem
- Forwards traffic signals to the TDM switching subsystem
Gb Interface Processing Unit
- Provides E1/T1 electrical ports, FE/GE electrical ports, and GE optical ports.
- Receives and transmits signaling and traffic signals between the BSC and the SGSN
- Processes the signaling according to the FR/IP protocol
- Forwards signaling and traffic signals to the GE switching subsystem
Cb Interface Processing Unit
- Provides FE/GE electrical ports
- Receives and transmits the signaling between the BSC and the CBC
- Forwards signaling to the GE switching subsystem