Cables to Go CDM-570L manual Load Switch Example

Load Switch Example

3.The STDMA Hub Controller compares the remote CDM-570/570L’s pre- selected buffer limits with its buffer status and if the buffer status exceeds the preselected limits the STDMA Hub Controller increases the time-slot allocated to that channel. If this brings the buffer status within established limits no further changes are made.

4.If the buffer status continues to exceed the preselected limits, the STDMA Controller sends an Automatic Switch Request (ASR) to the VMS.

5.The VMS processes the switch request by checking for available resources by:

•Determining if there is a free demodulator.

•Determining the channel space (bandwidth) requirements to accommodate the data flow requested by the STDMA Hub Controller.

6.If the VMS finds available resources it processes the switch request and sends tuning commands which switches the remote CDM-570/570L out of STDMA into SCPC mode.

The ideal condition being looked for is that about 90% utilization of the channel be achieved striving to optimize the use of available bandwidth.

In the case where the remote CDM-570/570L continues to report buffer overflow, the STDMA Hub Controller will send a request to the VMS which in turn will attempt to double the carrier bandwidth for that channel.

The ability to actually accomplish this is limited by the currently available carrier bandwidth, and ultimately the power output and antenna size available at the transmitting remote site.

If the STDMA Hub Controller cannot make the increase in bandwidth, it will continue to receive buffer status reports from the remote CDM-570/570L indicating that buffer flow is continuing and the STDMA Hub Controller will, in turn, continue to request additional bandwidth from the VMS. If at any time another service drops making bandwidth available, the next time the STDMA Hub Controller requests additional bandwidth the VMS will grant the request.

If the video data stream is completed before the switch in bandwidth is done, the channel is closed, the bandwidth which had been used is made available again to the pool, and no further action is taken.

Appendix B - Automatic Switching B-9