Doubling CDMA capacity by in-cell sequence reuse and soft interference cancellation

We investigate a multiple access concept consisting of a combined OCDMA/OCDMA scheme that can accommodate up to 2N users, with N denoting the spreading factor. Hence, the capacity of this scheme is twice the capacity of conventional OCDMA. Multiuser interference is reduced by means of iterative soft interference cancellation. For maximum load (i.e., 2N active users), the BER performance improves with increasing N. The resulting SNR degradation at BER=10^-4 is found to be negligibly small as soon as N⩾64. Our performance results show the superiority of OCDMA/OCDMA over PN-CDMA, assuming both systems have spreading factor N, accommodate 2N users, and apply soft interference cancellation. In addition, the computational complexity of OCDMA/OCDMA is only half that of PN-CDMA