Dear Lalit, The problem is every time the simulation is run, the amount of BER differs from the last time for every user. I think this is due to three main factors: randomness of noise, random seeds generation being chosen, and short bit sequence. I just increased the bit length to 4096 (and reduced samples per bit just to make simulation time shorter; you don’t have to do this) and got min. BER of about 10-4 to 10-6 for all users for three simulations. So I suggest that you increase it.