The switching subsystem BSC6900

The switching subsystem

The switching subsystem consists of logical modules of two types: MAC switching and TDM switching. Figure 3-5 and Figure 3-6 show the position of the switching subsystem in the MPS/ EPS and TCS respectively, with the modules highlighted in apricot.

Functions

· Provides intra-subrack Medium Access Control (MAC) switching

· Provides intra-subrack Time Division Multiplexing (TDM) switching

· Provides inter-subrack MAC switching and TDM switching

· Distributes clock signals and RFN signals to the service processing boards

Hardwar Involve

The switching subsystem consists of the SCUa boards, TNUa boards, high-speed backplane channels in each subrack, crossover cables between SCUa boards, and inter-TNUa cables.

SCUa : GE Switching network and Control Unit REV:a

TNUa : TDM switching Network Unit REV:a

SCUa

l Provides MAC/GE switching and enables the convergence of ATM and IP networks.

l Provides data switching channels.

l Provides system-level or subrack-level configuration and maintenance.

l Distributes clock signals for the BSC6900

l BSC6900 GSM and BSC6900 UMTS

TNUa

l Provides the TDM switching and serves as the center of the circuit switched domain.

l Assigns the resources of the TDM network and establishes the network connection.

l Provides communication processing on the GE port.

Network Topologies Between Subracks

In the switching subsystem of the BSC6900, the star topology is established among the MAC switching logical modules, and the mesh topology is established among the TDM switching logical modules.

Inter-Subrack Connection

The MAC switching logical modules switch the ATM/IP traffic data, OM signals, and signaling.

The switching is performed by the SCUa boards and the Ethernet cables between the SCUa boards. The inter-subrack connections related to MAC switching can be classified into the following types:

Interconnections between the MPS and the EPSs

The MPS functions as the main subrack, and a maximum of five EPSs function as extension subracks. The star interconnections between the MPS and the EPSs are established through the Ethernet cables between the SCUa boards, as shown in Figure 3-8.

Interconnections between the TCSs

One TCS functions as the main subrack, and a maximum of three TCSs function as extension subracks. The star interconnections between the TCSs are established through the Ethernet cables between the SCUa boards, as shown in Figure 3-9.