3 RNC Switching Subsystem

About This Chapter

This part describes the functions and components of the RNC switching subsystem.

3.1 Functions of the RNC Switching SubsystemThe RNC switching subsystem mainly performs the switching of data in the RNC.

3.2 Components of the RNC Switching SubsystemThe RNC switching subsystem consists of the switching and control unit and high-speedbackplane channels in each subrack.

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3.1 Functions of the RNC Switching SubsystemThe RNC switching subsystem mainly performs the switching of data in the RNC.

The switching subsystem has the following functions:l Provides internal Medium Access Control (MAC) switching for the RNC and enables

convergence of ATM and IP networks.l Provides port trunking for the RNC.

l Connects subracks of the RNC.

l Provides a service switching channel for the service processing subracks of the RNC.

l Provides an OM channel for the service processing subracks of the RNC.

l Distributes timing signals and RFN signals to the service processing boards of the RNC.

3.2 Components of the RNC Switching SubsystemThe RNC switching subsystem consists of the switching and control unit and high-speedbackplane channels in each subrack.

Figure 3-1 shows the components of the RNC switching subsystem.

Figure 3-1 Components of the RNC switching subsystem

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Switching and Control Unit

Each switching and control unit shown in Figure 3-1 is implemented by an SCUa board. Theboard provides a platform of GE switching and of maintenance and administration for the RNC.For functions of the SCUa board, refer to Functions of the SCUa Board.

Each subrack of the RNC can be configured with two SCUa boards. The SCUa boards work infull-interconnection and dual-plane mode and enable connection of subracks for the RNC.

NOTE

For details about the maintenance and administration functions of the SCUa board, refer to 6.1 Componentsof the RNC OM Subsystem.

Intra-Subrack Data Switching

The intra-subrack data switching of the RNC adopts backplane-based communication. The intra-subrack switching channels provide port trunking. The GE switching between the SCUa boardand the other boards in the subrack is performed through the high-speed backplane channels.

Inter-Subrack Data Switching

The inter-subrack data switching of the RNC adopts star topology. In this topology, the RSS isthe main subrack and the RBSs are extension subracks. The SCUa boards in the RBS subracksare connected to the SCUa boards in the RSS subrack through Ethernet cables. The inter-subrackGE switching is performed through the RSS subrack. Figure 3-2 shows the inter-subrackconnections.

Figure 3-2 RNC inter-subrack switching

The RSS subrack and an RBS subrack are connected in full connection mode. This topologyhelps prevent single-point failure. Thus, the failure of any board does not affect data switchingof the RNC. The GE ports on the SCUa board provide port trunking. As shown in Figure 3-2,four GE channels comprise a trunk group. Port trunking enables bandwidth expansion and trafficbalancing.

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