Adaptive importance sampling for bit error rate estimation in slowly fading channels

Theoretical evaluation of the bit error rate (BER) performance of digital communications systems in fading channels may be very difficult or impossible. Computer simulation is an essential approach to assess the performance for mobile and portable communications. However, in the case of a low BER value or a slowly fading channel, computer simulation time can be prohibitively long in order to obtain an accurate BER estimate. This paper proposes a new adaptive importance sampling (AIS) technique for estimating the BER performance in an indoor wireless environment. The technique adaptively searches for optimal biased probability densities during the course of the simulation. The procedure of determining the optimal biased probability densities is simplified and the computer simulation time is considerably reduced.