Investigating and Improving the Efficiency of Space-time Codes in Visible light Communication Systems based on a Multi-input-multi-output Channel Model

Abstract

Background: Visible light communication (VLC) is a new communication method for transmitting information through semiconductor lighting devices. One of the applicable methods to improve the spectral efficiency of the system is the multi-input-multiple-output (MIMO) structure. Also, carrierless amplitude-phase (CAP) modulation is a high-dimensional modulation technique that can be used to improve the data transmission rate in modern communication systems. Methods: In this paper, carrierless amplitude-phase method is introduced in indoor optical communication systems to improve the performance of multi-input multi-output (MIMO) structures. The CAP modulation is considered a suitable method due to its low complexity and is introduced and studied in two structures with one carrier or CAP and multiple carriers or m-CAP. Results: In this study, the target system is simulated in m-CAP structures and the improvement is measured in the MIMO structure using this modulation. The results show that by using this method, the PAPR of the system was reduced compared to other research with the MIMO-OFDM structure. In addition, by not using FFT blocks, the computational and processing complexity was also reduced. Conclusion: It has been shown that the use of m-CAP increases the data transfer rate and improves the spectral efficiency of the system. In addition to CAP, spatial modulation schemes can also help improve the spectral efficiency and power efficiency of the system. Moreover, the space-time code is combined with m-CAP modulation and it is shown that this idea improves the efficiency of the MIMO system.