Impact of systematically constructed nonorthogonal code shift keying for optical code division multiple access

It is desirable to provide Optical Code Division Multiple Access (OCDMA) systems for practical use in optical wireless communication application systems. Because the data transmission efficiency of the conventional OCDMA system is relatively low, one of the issues encountered with the OCDMA system is increasing the data transmission efficiency. This study proposes the nonorthogonal CSK system in order to clarify the performance improvement of the proposed system on the OCDMA system. Our proposed nonorthogonal CSK system systematically constructs nonorthogonal codes. This paper analyzes the system performances of the proposed system considering the scintillation, background noise, and multiple access interferences to evaluate the fundamental performance of the proposed system. The numerical results show that the proposed system outperforms the conventional OCDMA systems. Our obtained results that the systematically constructed nonorthogonal code is effective for enhancing OCDMA system performance is a useful finding for future research approaches.