Optical Improved Quadrature Spatial Modulation for Cooperative Underwater Wireless Communication under Weak Oceanic Turbulence Conditions

摘要

Amplify-and-forward cooperative underwater optical wireless communication employing optical improved quadrature spatial modulation (OIQSM) is proposed in this study. It uses multiple signal constellations, thereby improving the system performance. It uses multiple lasers but it activates only a few of them depending on the message bits and can transmit double modulated symbols in a single symbol interval. The OIQSM system performance is compared in terms of bit error rate (BER) with other existing schemes in the literature. The analysis is conducted for weak oceanic turbulence conditions, which is generally prevalent in deep oceans. The cost and power consumption analysis of OIQSM is performed to highlight its benefits over other schemes. It is observed that OIQSM yields a signal-to-noise ratio gain of at least 5.5 dB over the conventional optical spatial modulation scheme for any BER value between 10(-2) and 10(-4).