Performance of CDMA systems with low-rate coding and interference cancellation

Paper i proceeding, 1999

ABSTRACT The performance of a CDMA system employ-ing very low-rate maximum free distance codes for com-bined coding and spreading is analyzed when successive o r parallel interference cancellation is applied. An analytical approach to the evaluation of the bit error rate is presented and shown to give results close to simulations. Our results show that the code spread system outperforms the conven-tionally spread system. Without interference cancellation the single-user bound is never reached except for one user. With two stages of parallel interference cancellation, a code-spread system with a load only slightly less than 1 bittchip obtains a bit error rate very close to that of a single user system with signal-to-noise ratio per information bit of 4 dB. Keywords| CDMA, low-rate convolutional codes, orthog-onal codes, successive i n terference cancellation, parallel in-terference cancellation, rate-compatible, maximum free dis-tance.