Communication in the underwater wireless sensor networks (UWSNs) faces many challenges due to the acoustic wave characteristics. Acoustic wave has very limited bandwidth, long propagation delay, high bit error rate (BER), and unreliable communication compared to the radio wave. Therefore, media access control (MAC) protocols proposed in terrestrial wireless sensor networks (TWSNs) cannot be implemented underwater as TWSNs rely on radio waves and enables multiple transmissions at a time without causing a collision. Besides, underwater nodes operate in a half-duplex mode and only allows one transmission at a time. Designing an efficient MAC protocol for underwater time-sensitive applications, such as the oil/gas pipeline and climate change prediction applications is necessary. While each application has its own requirements, the software-based approach promises great enhancements to meet more than one application's requirements. The software-based approach allows us to reconfigure the variables through a software without additional hardware requirements. To address the above issues, this paper proposes a software-based MAC protocol that utilizes optical and acoustic wave for communication and allows multiple transmissions at a time in different directions. This study aims to maximize throughput, packet delivery ratio (PDR) network utilization while minimizing latency.

If the recovery or remedial time is not incorporated in the reliability of a software module in a safety and time-critical integrated system operation, then a mere reliability index based on failure characteristics is simply not adequate and realistic. In deriving the probability density function (pdf) of the software availability, empirical Bayesian procedures will be used to employ expert engineering judgment through appropriate noninformative and informative prior distribution functions employing various definitions of risk functions. It is emphasized that the usage of maximum likelihood estimators regardless of the extent of historical data is erroneous and misleading.