The UMG8900 can be applied in the mobile core network. It can work with the media gateway controller (MGC) to serve as a visited mobile switching center (VMSC), tandem mobile switching center (TMSC), or gateway mobile switching center (GMSC). When applying to IP multimedia subsystem (IMS) networking, the UMG8900works with the media gateway control function (MGCF) to implement interworking between the circuit switched (CS) domain of the core network and an external network.

The UMG8900 supports SSM-256 and SSM-32 frames that can work in multiple cascading modes. When the UMG8900 serves as a VMSC, it can connect to an external shared IWF (SIWF) frame to provide the IWF function. These modules are described as follows:

• Figure 1 shows the hardware components of the UMG8900 when only SSM-256 frames are configured.

  Figure 1 Hardware components (SSM-256 frames) 
  
  

  In the case of cascading only SSM-256 frames, the UMG8900 supports nine-frame cascading at most. When the UMG8900 works as a VMSC, it needs to attach an SIWF frame to provide the IWF function. The UMG8900 and the SIWF connect to each other through FE and E1 cables, and communicate through internal protocols.

  The frames of the UMG8900 can be logically classified into the main control frame, central switching frame, service frame, and control frame. The main control frame is the control and management center of the UMG8900 and also provides the service processing function. The central switching frame provides switching and cascading functions. The service frame provides the service processing function. The control frame only processes call control messages rather than carry services.

  In the case of cascading only SSM-256 frames, TDM, FE, and GE cascading channels are available between frames. The UMG8900 supports 4 x 8 K TDM cascading, 2 x GE cascading, and 1 x FE cascading. The cascading channels work in master/slave mode.

  When the SSM-256 frames are configured, independent CLKs are required to provide stratum-2A and stratum-3 clock signals. In addition, clock distribution cables are connected from the CLKs in the main control frame to the service frames and central switching frame to provide clock signals for the service frames and central switching frame.

• Figure 2 shows the hardware components of the UMG8900 when only SSM-32 frames are configured.

  Figure 2 Hardware components (SSM-32 frames) 
  
  

  In the case of cascading only SSM-32 frames, the UMG8900 supports three-frame cascading at most. When the UMG8900 works as a VMSC, it needs to attach an SIWF frame to provide the IWF function. The frames of the UMG8900 can be logically classified into the main control frame, service frame, and central switching frame. The main control frame is always numbered 1. The main control frame can also serve as the central switching frame at the same time.

  If the UMG8900 adopts only SSM-32 frames, TDM and FE cascading channels are available for cascading between frames to provide 1 or 2 x 8 K TDM and 1 x FE cascading capacities. The TNCs in the main control frame or the central switching frame connect to the TNCs in other frames. No independent cascading boards are required.

  The SSM-32 frames support GE cascading as well. In this case, you need to configure independent cascading boards, that is, NLUs.

  Clock subboards can be installed on the TNCs in the main control frame to provide stratum-3 clock signals, or independent CLKs can be configured to provide stratum-2A or stratum-3 clock signals. Other frames extract clock signals through the TDM cascading cables between frames. No independent clock distribution cables are required.

• Figure 3 shows the hardware components when SSM-32 and SSM-256 frames are used.

  Figure 3 Hardware components (SSM-256 and SSM-32 mixed application) 
  
  

  When the UMG8900 works as a VMSC, it needs to attach an SIWF frame to provide the IWF function. The frames of the UMG8900 can be logically classified into the main control frame, service frame, and central switching frame. The main control frame is always numbered 1 and the central switching frame is always numbered 0. In this case, the SSM-32 frame or the SSM-256 frame serves as the main control frame; the SSM-256 frame serves as the central switching frame; the SSM-32 frame or the SSM-256 frame serves as the service frame.

  In the case of mixed application of SSM-256 and SSM-32 frames, TDM and FE cascading channels are available between frames. The cascading capability of 1 or 2 x 8 K TDM and 1 x FE is provided between the SSM-256 central switching frame and the SSM-32 frame.

  In the case of mixed cascading of SSM-256 and SSM-32 frames, the UMG8900 also supports GE cascading between frames. In this case, you need to configure independent NLU cascading boards in the SSM-32 frames.

  In this mode, the SSM-32 main control frame can use the clock subboard on the TNC to provide stratum-3 clock signals or use the CLK to provide stratum-2 or stratum-3 clock signals. The SSM-32 service frame uses TDM cascading cables to extract clock signals. The SSM-256 central switching frame and the SSM-256 service frame use clock distribution cables to extract clock signals.

This document is very well done

What do mean ssm-32 frame?

Please share the installation procedure also...

I like the post..

visited mobile switching center (VMSC), tandem mobile switching center (TMSC), or gateway mobile switching center (GMSC). 

what are the difference of above them...

Figure 1 Hardware components (SSM-256 frames) 

Nice figure....thanks

what is the main activity of central switch???

what is the the SSM-256 frames...??? 

very nice post...