Quick simulation of multi-channel direct sequence spread spectrum communication systems

In evaluating the BER for direct sequence spread spectrum multiple-access communication systems, it is very difficult to obtain a closed form expression for the output of these systems. Therefore one usually resort to simulation techniques such as the Monte Carlo method to evaluate the BER. The BER is usually small for these systems, hence an excessive amount of time and computations is required to adequately estimate the BER. One way to circumvent this problem is to utilize importance sampling method, which will give a good estimate for the BER with relatively small number of simulation runs. A technique known as quick simulation method developed from the principles of large deviation theory and importance sampling is used to estimate the BER. The quick simulation method is compared to two other methods used to evaluate the BER