RF-based Wireless Communication for Shallow Water Networks: Survey and Analysis

In modern times, applications such as port security, navigation, tsunami alert, etc., need real-time data transfer in shallow waters. These applications require large data rates for multimedia communication between underwater nodes and base-station. Although wired networks provide large data rates, the wires would be an obstacle to moving objects in the water. Alternatively, wireless acoustic communication is used in deep water applications. Notably, in shallow water, radio frequency (RF) communication serves a higher data rate than acoustic but, suffers from less transmission range due to large attenuation. The objective of this research is to study the feasibility of RF propagation in shallow waters and analyze the requirements and challenges for RF-based shallow water wireless networks. A range enhancement technique for RF communication, multi-hop communication, is also surveyed and its challenges for shallow waters are discussed. In the oceans around the Indian subcontinent, the shallow water can be considered as a lossy-dielectric medium and the physical parameters affect the electrical properties. The conductivity of the water increases linearly with an increase in salinity and temperature though this rate is higher with the increase in salinity. The variation in conductivity, in turn, affects the attenuation and path loss. The path loss in Bay-of-Bengal is approximately 2% less than in the Arabian Sea which affects the performance of RF propagation. It is also observed that the RF communication range using a multi-hop technique can be increased up to 240 m in shallow water with a bit error rate of 10−2 at 1 Mbps data rate.