Turbo coded CDMA system with an interference cancellation technique

In this paper. we suggest the interference cancellation (IC) technique suit able for turbo coded code division multiple access (CDMA) systems, that mer ges IC processes into turbo decoding processes to improve system performanc e and reduce system complexity. To ensure the reliability of the temporary decision bits for cancellation. we use cyclic redundancy code (CRC) check a s a measure. Prior to design turbo coded CDMA system, we first derive the o ptimized polynomials of low-rate turbo codes appropriate to CDMA systems. A ccording to the simulation results with setting the processing gain (PG) to 120, the turbo coded CDMA system with the proposed IC technique can accomm odate 60 users over additive white Gaussian noise (AWGN) channel when signa l to noise ratio (SNR) is about 2.5 dB and required frame error ratio (FER) is 10(-2). Compared this result with the performance of single user's syst em, it requires only additional 1 dB SNR.