Abstract
In this paper, we investigate and enhance the performance of data transmission using a hybrid underwater and terrestrial system with low‐complexity linear equalization. Due to the low speed, salinity, water depth, pH degree, and water temperature variations, underwater acoustic communication has become one of the most challenging technologies in the world. The most common linear equalizers are the Linear Zero Forcing (LZF), and Linear Minimum Mean Square Error (LMMSE) equalizers. The LZF equalizer suffers from the noise enhancement problem, while the LMMSE equalizer requires the value of the operating Signal‐to‐Noise Ratio (SNR) to work, correctly, which increases the computational complexity. In addition, this paper presents a low‐complexity equalization scheme to overcome the drawbacks associated with the LZF, and LMMSE equalizers. The proposed equalizer is called the Joint Low‐Complexity Regularized LZF equalizer, which depends on a fixed regularization parameter to minimize the noise enhancement phenomenon caused by the LZF equalizer. The proposed equalizer does not need the estimation of the SNR, and the computational complexity is reduced due to the utilization of the banded‐matrix approximation. The proposed equalizer is implemented based on the Single‐Input‐Single‐Output configuration for Orthogonal Frequency Division Multiplexing (OFDM) using the Discrete Cosine Transform. The obtained simulation results show that the proposed equalizer outperforms different equalizers for the same channel conditions.
The proposed communication system consists of two segments: the underwater segment that can be implemented by acoustic waves, and the second segment in the air that can be implemented by electromagnetic waves. Note that the transducer in the underwater medium is the hydrophone, while the antenna is the transducer for the electromagnetic propagation. The linked transceiver (buoy) is a conversion stage from acoustic waves to electromagnetic waves. The aim of the proposed system is to transfer any underwater information to land. This information may include vital data for divers, such as temperature, heartbeat, and blood pressure, to monitor the health conditions of the divers. Also, it may be an information gathered from an underwater sensor network for monitoring of water temperature and salinity or studying a phenomenon for environmental or research purposes.