Efficient Implementation of Downlink Cdma Equalization Using Frequency Domain Approximation

A signal transimitted through a wireless channel may be severely distorted due to intersymbol interference (ISI) and multiple access interference (MAI). In this paper, we propose an efficient CDMA receiver based on a frequency domain equalization with a regularized zero forcing equalizer and unit clipper decision with parallel interference cancellation (FDE-RZF-CPIC) to combat both ISI and MAI. This receiver is suitable for downlink zero padding CDMA (ZP-CDMA) cellular systems. The effects of the decision function, the channel estimation, the number of cancelled users, and the user loading on the performance of the proposed receiver are discussed in the paper. The bit error rate (BER) performance of the proposed receiver is evaluated by computer simulations. It has been found that the proposed receiver provides a good BER performance, even at a large number of interfering users. At a BER of 10, the performance gain of the proposed receiver is about 2 dB over the RAKE receiver with clipper decision and parallel interference cancellation in the half loaded case (8 users ) and is much larger in the full loaded case (16 users).