Interference cancellation in overloaded optical CDMA systems using unipolar walsh codes

In this article, the authors introduce and propose an overloaded Synchronous Optical Code Division Multiple Access (SOCDMA) based on Unipolar Walsh Code (UWC) for fiberoptic communication systems. Given L as the number of chips, it is shown that 2L - 2 active users can be supported by the proposed system. In this system the users of the network are categorized into two groups. Users of each group transmit at the same power level but different from the level of the other group´s users. Using the UWC properties we propose a simple receiver that cancels multiple-user interference (MUI) completely. Moreover, we obtain the optimal power level of each group in order to minimize the probability of error for a given average transmit power. We demonstrate that the proposed receiver has an acceptable performance compared to the optimum multiuser receiver.