Spatial correlation analysis of imaging MIMO for underwater visible light communication

Abstract

Absorption and scattering are the main problems affecting the transmission of large capacity information data in underwater visible light communication system(UVLC). To address these problems, we propose the imaging multiple input multiple output (MIMO) system for the underwater communication in this paper. Furthermore, the proposed system uses imaging lens to separate the light signal resulting in that decreasing disturbance of the proposed system is better than that of non-imaging MIMO. In this paper, the spatial correlation caused by imaging lens structure of underwater visible light imaging MIMO communication channel is analyzed. In addition, the influence of the spatial position for transmitting and receiving ends of the imaging system such as light-emitting diode (LED) light source array spacing, and the distance between LED and photodiode (PD) on spatial correlation are modeled. Moreover, the imaging MIMO channel capacities under different channel conditions are derived. The upper bounds of channel capacities under different spatial correlations are solved by equal power allocation method and water injection power allocation method. Finally, the simulation results show that the imaging MIMO system achieves a 12 dB gain at the same bit error rate (BER) compared to the non-imaging MIMO system. Furthermore, the capacity and BER performance of the proposed system are the best in the case of the weakest spatial correlation, and the performance is greatly improved as the spatial correlation becomes weaker.