In NetSim, Random back off time algorithm can be modified using the function below:

Open fn_NetSim_IEEE802_11_CSMACA_RandomBackOffTimeCalculation() function present in CSMA.c file inside IEEE802_11 project


It uses a linear congruential random number generator to generate the randomness. For more information on how random number generator works in NetSim, please refer the link below

how-does-the-random-number-generator-in-netsim-work-