New design of optical zero correlation zone codes in quasi-synchronous VLC CDMA systems

Direct-sequence optical code division multiple access technology is one efficient and simple way to reduce the multiple access interferences that existed in visible light communication system due to its ease implementation by simply turning the light-emitting diodes (LEDs) on and off. To overcome the multi-path effect and non-perfect clock impairment, an optical zero correlation zone code set is proposed in visible light communication quasi-synchronous optical code division multiple access system. Bit error rate performance is evaluated while taking into account the effects of phase-induced intensity noise, shot noise, and thermal noise. Based on the proposed optical zero correlation zone codes, the multiple access interference and phase-induced intensity noise can be eliminated finally; therefore, a better bit error rate can be obtained.