Forward Error Correction Schemes for Data Communication Through Underwater Channel

The surveillance of harbor, detection of mines, detection of enemy submarine and mapping of ocean bottom are crucial factors for any country’s defence mechanism. The advent of Autonomous Underwater Vehicle (AUV) as an underwater robot has revolutionized the surveillance and navigation system particularly in the field of underwater warfare. AUVs are also deployed to carry different payloads for undertaking specific task where it is not possible for humans to be employed. The precise navigation, safe maneuvering of AUV in the constrained environment, transmission of the collected data to onboard Mission Computer System (MCS), to ship or shore-based Remote Controlling Station (RCS) and the receiving of commands from RCS to AUV are the important factors in the development of the AUV. The performance of the AUV is limited due to the complex underwater characteristics and precise estimates of the object’s signatures. The underwater characteristics such as time varying multipath and Doppler spreads cause low throughput and high bit error rates in the transmitted AUV data. In underwater medium, the use of Radio Frequencies (RF) has been restricted due to the fast attenuation of the Electromagnetic Waves. On the other hand, Sound waves (Acoustic Signals) travel exceptionally well through the water. The images are collected through Sector Scan Sonar (SSS) fitted onboard AUV. After processing these images, the data corresponding to range, bearing, size and shape of the objects is extracted and transmitted to the RCS using wireless communication through underwater channel. Therefore, a need arose to reliably transmit these data through a complex environment encountered in the underwater channel.

Objective

The objective is to bring out the various Forward Error Correction (FEC) schemes that minimizes the Bit Error Rate (BER) while the data is transmitted through the underwater channel. With respect to the design of the FEC schemes it is to be noted that the underwater channel is a multipath dominant channel and fading is quite prominent in this channel. It has been observed that the convolutional coding based schemes perform better in the multipath environment. This book will be highly useful to the researchers engaged in the data communication in underwater environment.