Generalized quadrature spatial modulation techniques for VLC

• Published in: Optics communications 2020-09, Vol.471, p.125905, Article 125905
• Main Authors: Celik, Yasin, Aldırmaz-Çolak, Sultan
• Format: Article
• Language: English
• Subjects: Illumination; Spatial modulation; Visible light communication
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2020.125905

In this paper, generalized quadrature spatial modulation (QSM) techniques are proposed for multiple-input single-output (MISO) visible light communication (VLC) systems using quadrature spatial modulation subcarrier intensity modulation (QSM-SIM). Additionally, realistic channel condition including both line-of-sight (LOS) and non-LOS (NLOS) components up to the third reflection is also considered and channel coherence bandwidths are calculated for varying number of LEDs. Since the indoor MISO VLC channel has strong correlation between coefficients, particle swarm optimization (PSO) and approximated maximum minimum Euclidean distance (AMMD) based precoding on the transmitter side are studied to reduce the channel correlation under illumination constraints. As a performance metric, bit error rate (BER) performance of considered modulation techniques is analyzed for different MISO schemes. The upper bound BER performances are also derived analytically in order to validate the simulation results. According to the results, we reached three important conclusions. First one is that variable length generalized QSM (VGQSM) by having few LED arrays on the transmitter side performs the best BER results compared to other schemes that provide the same spectral efficiency (SE) and the second is that precoding is essential for indoor MISO VLC systems to reduce the channel correlation. Finally, an increase in the number of LED arrays results in a decrease in channel coherence bandwidth.