Let us say there is some delay in sensing the primary. This would mean that there is a delay in sending the UCS. To incorporate this

In the file SpectrumManager.c

in then function int fn_NetSim_CR_QuietPeriod(), go to the line

pstruPacket->pstruMacData->dArrivalTime = pstruEventDetails->dEventTime;

Add some delay in the above line. 

Then check the packet trace/metrics to see the effect of this delay