A Study on Signature Codes and Bit Error Rate Performance of Synchronous Optical CDMA with MUI Cancellation

摘要

In optical CDMA systems, unipolar codes are used as signature codes. Available number of signature sequences in an orthogonal code is much smaller than that in a non-orthogonal code with the same codeweight. However, orthogonal codes are far less vulnerable to MUI than non-orthogonal codes. Recently, several kinds of MUI cancellation techniques have been proposed for synchronous optical CDMA systems. All these techniques utilize MPSCs, which is a class of non-orthogonal codes. In this paper, we show the conditions for non-orthogonal codes to be applied to such MUI cancellation techniques. It is shown that not only MPSCs but also other non-orthogonal codes can be used in Shalaby's scheme and the EWO scheme. Furthermore, we investigate the bit error rate performances of synchronous optical CDMA systems with MUI cancellation under the condition that background noise, thermal noise and APD noise are taken into account. The results show that there are three major factors which affect bit error rate performance of synchronous optical CDMA systems.