On the study of a quasi-synchronous CDMA-VLC system with two channels.

Abstract

In this paper, a new construction of optical zero correlation zone (OZCZ) code set pair is proposed for quasi-synchronous code division multiple access (QS-CDMA) visible light communication (VLC) system. Owing to its excellent correlation properties within zero correlation zone and greater code weight, the multi-user QS-CDMA-VLC system using the proposed code construction can obtain both good performance in illumination and communication. An experimental QS-CDMA-VLC system with two optical channels and two experiment setups is designed to evaluate the performance of the new OZCZ code set pair. When the free-space transmission distance difference is 1 m, we successfully achieve the 2-user and 14-user CDMA-VLC for 32.5 Mb/s and 24.1 Mb/s overall bit rate respectively, under the 7% forward-error-correction (FEC) limit of 3.8×10 -3. The experimental results indicate that, comparing to the other existing optical code sets, the proposed OZCZ construction can effectively reduce the impact of non-perfect synchronous problem, so that the bit error rate (BER) performance is improved. And dimming values and overall bit rates of the system can be significantly improved.