question regarding an passband example

Hi,

By typing "commpassbandmod" in the command console you can open a passband simulation example model.

If the parameter "Samples per frame" in Random Integer Generator block is changed to 10 ("Samples per frame" in Local Oscillator block in Upconverter subsystem and "Samples per frame" in Local Oscillator block in Downconverter subsystem are changed to 80), the BER gets higher and the spectrum changes a lot.

My question is, why this parameter has such a great influence on performance. Does it make difference if 100 or 10 samples are sent together?

Best Regards, Owen