VoIP Voice and Fax Signal Processing

5.7 PLC TESTING

The PLC requirement arises with loss of packet in the network. In the deployment, it may not be possible to monitor the PLC performance. PLC testing may not be straightforward and simple. It requires a lot more interpretations of conditions and results. While making the modules and product, PLC has to be evaluated thoroughly. To create packet drop, several approaches can be used depending on the available instrumentation and product cycle. To test PLC performance at the module level,

1. It is required to drop packets at the input of the decoder based on the required loss pattern. Stand-alone PESQ software may be used that compares both reference input and degraded output (PLC-enhanced output signal) for various PLC and decoder operations. The results from this type of test may be used as reference for system-level tests.
2. The next level of module-level integration, jitter buffer input, can be used to erase the packets. Achieving similar results of the previous module-level test is the desired goal. Sometimes the jitter buffer may influence the packets, mainly in disturbing the packet loss duration adjustments. Increase of actual loss duration or reduction of loss duration in jitter buffer or at any other stage in the path is more harmful to the PLC operation.
3. The third levels of tests are on IP network with the test setup shown in Chapter 13. IP impediment generators are used on the IP network that creates several impediments, and they can be controlled for the required ...