CDMA performance improvement through bias reduction using optimized partial parallel interference cancellation factor

In a CDMA system, the number of simultaneous users is a very important factor. So, a great number of researchers are interested in increasing the maximum available number of users for a given performance of a cellular system. To increase that number, multiple access interference (MAI) had to be cancelled. These cancellation techniques result in a bias term (BT) appearing in amplitude estimates after the cancellation process. The BT deviates the estimated values of amplitudes from their real mean, leading to a wrong decision. This paper introduces a new method to decrease the BT. Using the partial parallel interference cancellation (PPIC) factor, this factor is optimized against the bit error rate (BER). Also we show a comparison between BER of different types of sub-optimal receiver structures and PPIC with optimized factor F_g. Finally, we compare the BER of 3-main categories of CDMA receivers: the conventional CDMA receiver, brute force cancellation with 2 stages and 3 stages, and PPIC with optimized factor F, with 2 stages and 3 stages. We can say that the use of PPIC with optimized factor is a very good technique to decrease the BER and increase the number of simultaneous users for a given system´s parameters