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

Lifang Feng,Jianping Wang,Li Liu,Rose Qingyang Hu

doi:10.1186/s13638-015-0360-z

Abstract

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.

Highlights

In recent years, visible light communication (VLC) has become one attractable technology because of its advantages of eye-safe, electromagnetic-interference free, license-free, high signal-to-noise ratio (SNR), and high security [1-3]
Zero cross-correlation (ZCC) codes [12,13] do not have overlapping of bit ‘1’; they eliminate multiple access interference (MAI) and suppress phase-induced intensity noise (PIIN) of perfect synchronous Optical code division multiple access (OCDMA) system
6 Conclusions The correlation properties of multiple access codes dominate the performance of OCDMA systems

Summary

Introduction

Visible light communication (VLC) has become one attractable technology because of its advantages of eye-safe, electromagnetic-interference free, license-free, high signal-to-noise ratio (SNR), and high security [1-3]. For the system with simultaneous multiple users, the multiple access interference (MAI) and phase-induced intensity noise (PIIN) deteriorate the system performance significantly [5]. To reduce those impairments, many technologies have been proposed. Zero cross-correlation (ZCC) codes [12,13] do not have overlapping of bit ‘1’; they eliminate MAI and suppress PIIN of perfect synchronous OCDMA system. A new design of code set is proposed for VLC-QS-CDMA systems with ideal correlation properties in the zero correlation zone (ZCZ). The construction method of the optical zero correlation zone (OZCZ) code set is presented in Section 3 together with the derivation of the correlation properties. 0 0 i ≠ j; τ 1⁄4 0 0 < jτj≤Z ð3Þ where Z denotes the length of ZCZ

Construction and correlation properties of the proposed code set

Findings

Conclusions