Blind adaptive multiuser detection using linear parallel interference cancellation for CDMA systems
M. Li, Walaa Hamouda · 2005
We consider the application of parallel interference cancellation (PIC) schemes to improve both convergence speed and bit error rate (BER) performance of blind adaptive minimum mean output-energy (MMOE) detectors for direct-sequence code-division multiple-access (DS-CDMA) systems in near-far environments. The approach taken is to make use of the available knowledge of spreading codes for all users (i.e., at the base-station) to cancel multiple access interference (MAI) using a combined adaptive MMOE-PIC algorithm. The BER of the proposed system is evaluated using the Gaussian approximation. Simulation results show that the Gaussian approximation yields a precise evaluation at BER levels that are of practical interest. Moreover, it is shown that for a 10 user system with a severe near-far scenario and binary phase shift keying (BPSK) transmission, a 4-stage adaptive MMOE-PIC receiver does not need a training period for convergence to be reached. Furthermore, the proposed receiver is shown to attain a steady-state BER performance close to the standard minimum mean-squared error (MMSE) receiver while the adaptive MMOE detector suffers from a higher BER due to the imperfect filter coefficients.