MIMO techniques for robust underwater optical wireless communications by mitigating oceanic turbulence and transceiver misalignment

By using Binary Phase-Shift Keying (BPSK) modulation with heterodyne detection, we present in this paper an analytical approach to evaluate the effect of oceanic turbulence and pointing errors effects on an Underwater Wireless Optical Communication (UWOC). We use Gamma-Gamma turbulence model, and model the system’s bit error rate (BER) by using hypergeometric Meijer G-function. We have derived new closed-form expressions for the average BER of Multiple Input and Multiple Output Underwater Wireless Optical Communication (MIMO-UOWC) for oceanic turbulence only, pointing error only, and both effects combined. Numerical simulations show that the combined effect of oceanic turbulence and pointing errors cause a degradation in the system performance by increasing the BER. For instance, in a Single Input and Single Output (SISO-UWOC) with specific parameters, such as normalized pulse width of 8, normalized jitter of 2, Rytov variance of 0.6 which represents weak turbulence, and average SNR of 20 dB, the average BER value is [[EQUATION]], indicating evident degradation of communication quality in the network. To tackle this issue, we use Multiple Input and Multiple Outputs transceivers to enhance Underwater Optical Wireless performance in terms of BER. We model the MIMO Underwater optical wireless in two scenarios: the first for two-input and two-output system and the second for three-input and three-output. The average BER values for the first system and second system under following critical conditions: normalized pulse width of 6, normalized jitter of 3, Rytov variance of 2 which presents strong turbulence, and average SNR of 15 dB are around 10-7 and 10-12, respectively. These simulation results show that Multiple Input and Multiple Output (MIMO), specially for the second configuration (3 inputs and outputs) effectively mitigates intensity fluctuations, and maintains a BER under the reference of 10-9 establishing it as the preferred choice for reliable and efficient data transmission in Underwater Optical Wireless Network.