Adaptive MMSE decision feedback equalizer for asynchronous CDMA with erasure algorithm

Adaptive decision feedback equalizer with erasure algorithm (E-DFE) is proposed for asynchronous code division multiple access (CDMA) transmission, which not only combats intersymbol interference (ISI) and multiple access interference (MAI) but also reduces the effects of error propagation in the presence of Gaussian background noise. To reduce the possibility of feeding back the wrong decisions, the output of the feedforward filter of the E-DFE is processed before it is fed back to the feedback filter. Specifically, the focus is on the performance of E-DFE using soft-slicer based on a novel erasure algorithm. In addition, the fully connected feedback filter of E-DFE has been used to eliminate ISI due to other active users. Comparison of the performance of conventional decision feedback equalizer (C-DFE) and E-DFE over slowly varying frequency selective fading channel is presented to show the advantages of E-DFE in terms of reduced average bit error rate performance. Simulation results are also presented to show the substantial improvement in its performance under near-far situations and the sudden change in the signal power of the desired user.