Performance of Orthogonal and Non-Orthogonal Space Time Block Code Through the Underwater Wireless Optical Channels.

Multiple input multiple output (MIMO) schemes have been integrated with the space-time (ST) codes to enhance the reliability of information transfer across the wireless channel. Due to their rich algebraic structure, space time block codes (STBCs) such as orthogonal STBCs (OSTBC), quasi-orthogonal STBC (QOSTBC), and non-orthogonal STBCs (NOSTBC), offer efficient implementation of a reliable communication system. The underwater wireless optical communication (UWOC) channel is perturbed by the weak turbulence and fading (referred as scintillation), and shares many properties with a wireless channel. In this paper, we have designed OSTBC/QOSTBC and NOSTBC schemes for UWOC system, which can significantly improve the integrity of information transfer across the underwater optical wireless channels. These codes have been suitably conditioned to operate with an UWOC system employing intensity modulation. Monte-Carlo bit error rate simulations of the proposed schemes are plotted and presented with respect to the available transmit power in dB.