DS-CDMA assisted visible light communications systems

In this contribution we propose and investigate the performance of Direct Sequence Code Division Multiple Access (DS-CDMA) based VLC system using M-ary orthogonal modulation under Additive White Gaussian Noise (AWGN) channel. Various types of spreading code sequences are considered, including the modified binary sequences previously used in wireless CDMA systems and the optical orthogonal code (OOC) which is widely employed in the optical domain. For each code set correlation property is studied for the purpose of predicting whether its corresponding multiple access interference (MAI) is tolerable. Furthermore, sophisticated code designs are proposed to improve the system performance while reducing the overall MAI effect under specified channel conditions. The numerical results show that the performance of optical wireless networks can be enhanced with the proposed spreading code design.