Su altı akustik haberleşme sistemlerinin bilgi kuramı perspektifinden başarım analizi ve eniyilemesi

Underwater wireless communication is a rapidly growing field of research and engineering as its applications, which were once exclusively military, are extending into commercial fields. The need for underwater wireless communications exists in a wide range of applications including offshore oil field exploration/monitoring, oceanographic data collection, maritime archaeology, seismic observation, environmental monitoring, disaster preventing, port and border security among many others. Although capacity calculations for terrestrial radio-frequency channels have been extensively studied, the literature on the capacity of underwater acoustic (UWA) channels is sporadic with many remaining open questions. Aiming to fill research gaps in this growing field, this thesis makes several contributions to the information theoretical performance analysis of point-to-point and relay-assisted UWA systems. A single-carrier communication architecture and sparse Rician frequency-selective UWA channel with intersymbol interference (ISI) is considered in our work. We assume non-white Gaussian distribution to model the ambient noise and consider Francois-Garrison path loss formula to take into account the effects of environmental parameters such as temperature, salinity, pressure as well as system parameters such as distance and frequency. We develop an equivalent channel model for UWA channel with ISI under consideration and show that the capacity of the equivalent channel converges to that of the operating channel in the limit of infinite block length. Using these results, we first obtain a capacity expression for the UWA channel and demonstrate the dependency on channel parameters such as the number and location of significant taps and power delay profile, and environmental parameters such as temperature, salinity, and pressure. Then, we use this expression to determine the optimal carrier frequency, input signaling, and bandwidth. A closed-form formula for the optimum carrier frequency is further obtained. In the second part of the thesis, we extend our results to cooperative UWA systems and obtain achievable rates of single-carrier cooperative UWA systems with orthogonal decode-and-forward (DF) relaying. We take into account the effect of relay geometry in the derivations of achievable rates, and use the derived expressions to optimize the location of the relay.