The existing underwater acoustic modems are designed for deep oceans and long range communication leading to immense consumption of power and high cost. These long range underwater acoustic modems are not suitable choice for deployment in underwater sensor networks, Hence the problem was chosen to design and develop a underwater acoustic modems that operates in shallow waters of depth below 100m and for a short range of below 100 m. Underwater wireless sensor network is contemporary technology that can be applied in the fields of security, surveillance, military, commercial, industrial and environmental. The major drawback is that the traditional underwater acoustic modems cannot be deployed for underwater sensor networks. This work focusses on the research and development of the underwater acoustic modem for shallow waters and short range communication. The relevant background theory required understand acoustics and for modelling the unique characteristics of the underwater channel is described in detail. Different concepts to model and implement the functionalities of the transmitter and receiver were explored, while converging to the most suitable choice of concepts. The modelled system is simulated for different channel conditions such as depth, range and induced ambient noise. The results were analysed in order to conclude the performance outcome of the system. The modelled system can efficiently operate for a depth of 30m, 50m and 70m for a range up to 50m. The hardware was developed using minimum number of components as a proof of concept for efficient data transmission and reception using acoustic signals. The hardware was tested to operate efficiently in air, however hardware tests for underwater is suggested for future work, which will provide much better performance since acoustics is more suitable for communication in water than air.
Table of Contents
CHAPTER 1 - Introduction
1.1 Introduction to Underwater Acoustic Modem
1.2 Classification of the Acoustic/Sonar Communication Systems
1.3 Motivation
1.4Scope of the work
1.5Thesis Outline
CHAPTER 2 – Background Theory
2.1 Introduction
2.2 Classification of Bandwidths for Underwater Acoustic Communication Systems
2.3 Fundamentals of Underwater Acoustic Communication
2.3.1 Sound
2.3.2 Acoustic Pressure
2.3.3 Acoustic Intensity
2.3.4 Speed of Sound
2.4 Underwater Channel Characteristics
2.4.1 Spreading Loss
2.4.2 Absorption Loss
2.4.3 Path Loss
2.4.4 Doppler Effect
2.4.5 Multipath Fading
2.4.6 Ambient Noise
2.5 Bit Error Rate (BER)
2.6 Conclusion
CHAPTER 3-Literature Review
3.1 Introduction
3.2. Literature review on Underwater Acoustic Modems for Short Range Communication
3.3 Summary of Literature Review
CHAPTER 4 –Problem Definition
4.1 Problem Statement
4.2 Project Objectives
4.3 Methods and Methodologies adopted to meet the project objectives
CHAPTER 5 – System Engineering Based Design and Development of Underwater Acoustic Modem
5.1 Introduction
5.2 Need Analysis
5.3 Concept Exploration
5.3.1 Binary Frequency Shift Keying (BFSK)
5.3.2 Binary Phase Shift Keying (BPSK)
5.3.3 Error Protection and Detection
5.4 Concept Definition
5.4.1 Modulation Scheme
5.4.2 Error Protection and Detection
5.5 Advanced Development
5.5.1 System Block Diagram
5.5.2 Software tool used for simulations
5.5.3 Underwater Acoustic Channel Model
5.6 Engineering Design
5.6.1 Block Diagram and Description of the System
5.6.2 Hardware Set up
5.7 Conclusion
CHAPTER 6 – Results and Discussion
6.0 Introduction
6.1 Model 1-Simulations with Additive White Gaussian Noise (AWGN)
6.2 Model 2 – Simulations with AWGN and Path Loss
6.3 Model 3-Simulation with AWGN, Path Loss and 2 Multipath delays
6.4 Model 3-Simulation with AWGN, Path Loss, 2 Multipath delays and shipping noise (Complete underwater acoustic channel)
6.5 Hardware Implementation Results
6.6 Conclusion
CHAPTER 7 – Conclusion and Scope for Future Work
9.1 Summary
9.2 Conclusion
9.3 Recommendation for Future Work
Research Objectives and Topics
This project aims to design and develop an underwater acoustic modem specifically optimized for shallow water environments (depths < 100m) and short-range communications (< 100m). By leveraging systems engineering principles, the research seeks to overcome the high cost, high power consumption, and bulkiness associated with current commercial off-the-shelf acoustic modems, thereby enabling the practical deployment of dense underwater wireless sensor networks.
- Analysis of underwater acoustic channel characteristics, including path loss, multipath fading, and ambient noise.
- Comparative evaluation of digital modulation schemes, focusing on BFSK for robustness in shallow water.
- Implementation of Cyclic Redundancy Check (CRC) for error detection to ensure reliable data transmission.
- Simulation of the modem performance in MATLAB/Simulink under varying channel conditions.
- Proof-of-concept hardware realization using ultrasonic transducers and standard microcontrollers.
Excerpt from the Book
5.3 Concept Exploration
The harsh and changing environment in underwater acoustic channel has significant impact in attenuating and altering the information being transmitted. This leads to the loss and corrupting of signal information, thus leading to high probability of Bit Error Rate (Rate) at the receiver end. The data link performance of the acoustic modem depends on the type of modulation schemes used and also on the strength of error detection, protection capability. Even though, higher order modulation schemes with the modulation order of 4 and above can provide higher data throughput in air, but however for underwater, from (Burrowes and Khan, 2011), it is identified that higher order modulation schemes are not robust schemes for data communications underwater, as the signal levels increases, the system becomes more susceptible to noise and ISI. A robust data link performance can be achieved underwater using the simpler lower rate modulations schemes, and this thought has occupied researchers approach to use the BPSK and BFSK schemes for several decades. A brief to the two approaches is discussed in the following sections.
Summary of Chapters
CHAPTER 1 - Introduction: Presents the motivation for underwater communication, specifically identifying the gap in technology for short-range, shallow-water applications.
CHAPTER 2 – Background Theory: Covers the physical fundamentals of acoustic communication, including wave propagation, channel characteristics, and noise models.
CHAPTER 3-Literature Review: Reviews existing research and projects on underwater acoustic modems to establish a reference for the proposed system design.
CHAPTER 4 –Problem Definition: Outlines the project goals and the systematic methodology adopted to achieve the design objectives.
CHAPTER 5 – System Engineering Based Design and Development of Underwater Acoustic Modem: Details the system engineering process, including concept exploration, design specifications, and the modeling of the underwater acoustic channel.
CHAPTER 6 – Results and Discussion: Analyzes the simulation results across different models and discusses the findings from the hardware implementation tests.
CHAPTER 7 – Conclusion and Scope for Future Work: Summarizes the project outcomes and provides recommendations for potential future enhancements, such as implementing error correction and using high-end transducers.
Keywords
Underwater Acoustic Modem, Shallow Water Communication, BFSK, Acoustic Channel, CRC, Signal-to-Noise Ratio, BER, Underwater Wireless Sensor Networks, Path Loss, Multipath Fading, MATLAB, Simulink, Transducer, Data Transmission, Systems Engineering.
Frequently Asked Questions
What is the primary focus of this research?
The project focuses on the research, design, and development of an underwater acoustic modem tailored for shallow water (depth < 100m) and short-range (distance < 100m) communication to facilitate cost-effective underwater wireless sensor networks.
What are the central challenges addressed?
The work addresses the limitations of commercial modems, which are typically designed for long-range, deep-ocean use, resulting in high power consumption, high costs, and physical bulk that are unsuitable for dense sensor network deployments.
What is the main objective of the thesis?
The primary objective is to create an affordable, low-power, and compact acoustic modem transceiver that can efficiently adapt to the unique characteristics of the underwater channel while maintaining reliable data communication.
Which scientific methods were utilized?
The research utilizes literature reviews, systems engineering design, mathematical modeling of underwater acoustic channels, and Monte-Carlo simulations performed in MATLAB/Simulink to analyze performance parameters like Bit Error Rate (BER).
What does the main part of the work cover?
The main section covers the conceptualization, selection of the BFSK modulation scheme and CRC error detection method, software-based modeling of channel degradation (path loss, ambient noise, multipath), and the physical hardware implementation of the modem.
Which keywords characterize this work?
Key terms include Underwater Acoustic Modem, Shallow Water, BFSK, CRC, Acoustic Channel Modeling, and Underwater Wireless Sensor Networks.
Why was the non-coherent BFSK modulation scheme chosen over BPSK?
Non-coherent BFSK was selected because it is more robust in shallow water environments, specifically as it is immune to channel phase variations and simplifies the receiver design by eliminating the need for complex phase-tracking circuitry.
How were the hardware components chosen?
Hardware components, such as the PIC16F877A microcontroller and cost-effective ultrasonic transducers, were chosen based on the need to maintain low project costs and system complexity, serving as a proof-of-concept for underwater acoustics.
- Quote paper
- Masters in Electronics Systems Design Vinay Divakar (Author), 2014, Design and Development of Underwater Acoustic Modem for Shallow Waters and Short Range Communication, Munich, GRIN Verlag, https://www.grin.com/document/279298
