link budget analysis for undewater acoustic...

LINK BUDGET ANALYSIS FOR UNDEWATER ACOUSTIC SIGNALING

YOUSIF MOHSIN HASAN

A project report submitted in partial fulfilment

of the requirements for the award of the degree of

Master of Engineering (Electrical – Electronics and Telecommunications)

Faculty of Electrical Engineering

Universiti Technologi Malaysia

DECEMBER 2014

iii

“To my beloved Father, Mother, brothers, Wife, and Children”

iv

ACKNOWLEDGEMENT

First and foremost, I must be thankful to our creator “ALLAH” for this

continuous blessing and finishing my research, which make this work neither the first

nor the last. I would like to express my thanks and gratitude to my supervisor

“Dr. NOR HISHAM BIN HAJI KHAMIS”. He gave me this opportunity to do

research under his supervision.

Especially, I would like to send my deep appreciations to my beloved “Father

and Mother", thank you for the encouragement, for being my inspiration, for your

endless love.

I would like to send my deep appreciations to my family who brought me up

with love and completely support during my study.

v

ABSTRACT

Link-budget analysis is the method to get the link margin of the underwater

acoustic communication considering the transmitter signal power, transmitter

antenna characteristics, propagation losses, channel ambient noise, and receiver

antenna characteristics. Link-budget analysis is commonly applied to satellite and

wireless communications for estimating signal-to-noise ratio (SNR) at the receiver.

Underwater signal and the terms for the sonar equation translate easily to the

formulation of the link budget. However, the high frequency dependence of the

diffusion of underwater acoustics requires special attention, and is the result of an

argument called signal to noise ratio channel. And compared to many of the

problems of communication and voice navigation through link analysis of the large-

scale budget. Link budget is applied to voice communications system using the same

principles to sea radio link budget. The active sonar equation is utilized to provide an

estimate of the first class of signals available at the receiver. Three case studies have

shown wireless link budget of the utility systems in the design of broadband

communications. Link budget is a useful tool in the perceived impact of the channel

on the transmitted signal and evaluate the consequences of the strategic wireless

transmission. Aim of this case of the research is design wideband frequency

underwater acoustic communication system and comparative study of link budget

analysis for underwater communication with the attenuation of the underwater

channel by means of the modeling in the MATLAB software. Find out the channel

conditions of the underwater acoustic communication in the wideband frequency are

strongly range dependent due to underwater attenuation and interference noise. This

study found at that link budgeting considers the range and frequency dependence of

wideband signals in the acoustic medium. In particular, the channel SNR is strongly

frequency dependent in the bands of interest.

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ABSTRAK

Dengan mengambil kira kuasa isyarat pemancar, ciri-ciri antena pemancar,

rosotan perambatan, hingar ambien laluan, dan ciri-ciri antena penerima,

penganalisaan kepada keperluan had-laluan adalah satu kaedah untuk menentukan

had keperluan laluan untuk komununikasi akustik di dalam air. Penganalisaan had-

laluan sering dilakukan untuk perhubungan satelit dan komunikasi tanpa wayar untuk

menentukan nisbah kuasa isyarat kepada kuasa hingar (SNR) pada penerima. Isyarat

dalam air dan terma-terma persamaan sonar yang digunakan mudah diterjemahkan

kepada formulasi had-laluan. Walaubagaimanapun, resapan akustik di dalam air

dengan kebergantungannya kepada ketinggian frekuensi, perlu diberikan perhatian,

dan ini adalah hasil daripada perincian tentang nisbah kuasa isyarat kepada kuasa

hingar. Juga perbandingan kepada masalah komunikasi dan navigasi suara melalui

penganalisaan had-laluan pada skala yang besar. Prinsip had laluan untuk sistem

komunikasi suara diaplikasikan kepada had-laluan perhubungan radio di dalam

lautan. Persamaan sonar aktif digunakan untuk menganggar isyarat kelas pertama

yang tersedia di penerima. Tiga kajian kes telah dilaksanakan untuk mempamerkan

penganalisaan had-laluan dan rekabentuk laluan jalurlebar di dalam air. Kajian had-

laluan adalah satu kaedah yang sangat berguna untuk memberikan gambaran kesan

laluan ke atas isyarat yang dipancarkan dan juga untuk menilai hasil perambatan

tanpa wayar yang strategik. Tujuan kajian ini adalah untuk merekabentuk sistem

komunikasi akustik jalurlebar di dalam air, dan melakukan satu kajian komparatif

tentang penganalisaan had-laluan komunikasi di dalam air dengan kesan rosotan. Ini

dilakukan dengan perisian MATLAB. Kajian ini mendapati bahawa kondisi saluran

komunikasi akustik di dalam air pada frekuensi jalurlebar adalah sangat bergantung

kepada rosotan di dalam air dan gangguan hingar. SNR juga adalah sangat

bergantung kepada frekuensi di dalam jalur frekuensi untuk komukasi akustik di

dalam air.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF FIGURES ix

LIST OF SYMBOLS xi

1 INTRODUCTION 1

1.1 Background of the Research 1

1.2 Problem Statement 3

1.3 Objective of the Research

1.4 Benefits of Study

3

4

2 LITERATURE REVIEW 5

2.1 Acoustic Communication Link Budget 7

2.1.1 Link Budget 7

2.1.2 Required Signal Level ( ) 8

2.1.3 Available Signal Level 9

2.1.4. Link Margin 9

2. 2 Acoustic Link Budget Model 10

2.2.1 Sonar Equation (Received SNR ) 11

2.2.2 Directivity Index 11

viii

2.2.3 Pressure Spectrum Level 12

2.3 Channel Component of The Sonar Equation 13

2.3.1 Transmission Loss 13

2.3.2 Ambient Noise 15

2.3.2.1 Wind Speed 16

2.3.2.2 Thermal Noise 16

2.3.2.3 Shipping Traffic 16

2.3.2.4 Biologics

2.3.2.5 Precipitation

2.3.3 Ambient Noise VS. Wind Speed

17

17

18

2.3.4 Channel SNR 19

3 RESEARCH METHODOLOGY

3.1 Telesonar Directivity

21

21

3.1.1 Introduction 21

3.1.2 Design Trade-Offs 22

3.1.3 Link Budget model as comparison tool 22

3.2 Telesonar Transmitter

3.2.1 Introduction

3.2.2 Method of Design

3.2.3 Experiment and Practical Measurement of

Underwater Channel SNR

25

25

25

28

4 TELESONAR SHORT RANGE LINK BUDGET 30

4.1 Range Dependent Bandwidth 31

4.2 Sensitivity to Wind Speed 31

5 CONCLUSION AND FUTURE WORKS 39

5.1 Conclusion of the Result

5.2 Limitation

39

40

5.3 Future Work 40

REFERENCES 41

Appendix 43

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LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Block diagram representation of the link budget expressed in

Equation 2.1

8

2.2 Figure 2.2 Theoretical bit error rate vs. for selected

modulation schemes 4-QAM, 16-QAM, 64-QAM and

256-QAM

8

2.3 Frequency dependent Link margin (ws=25 m/s & D=0.5) 10

2.4 Coefficient for acoustic attenuation in seawater 14

2.5 Frequency dependent TL (dB re 1 μPa), plotted as a negative

quantity, -TL

15

2.6 Frequency dependent ambient noise 18

2.7 Dependence of total ambient noise with various wind speed 19

2.8 Channel SNR (dB) for a noise environment with heavy

shipping and 20 m/s. winds.

20

3.1 SNR comparison of candidate frequency bands. Wind speed

is 5 m/s. Omni-directional transducers are used in both bands.

23

3.2

3.3

3.4

3.5

SNR Comparison of candidate frequency bands . Wind speed

is 5 m/s. 9 dB directivity is employed in the a)15-20 kHz

b) 9-14 kHz band.

Channel SNR for 15 m/s wind speed exhibiting strong

frequency dependent

Channel SNR (dB) as a function of frequency for r=15000 m

and 15 m/s wind speed.

Link margin for uniform PLS=148 dB. Note that a region of

unsatisfactory SNR exists at high frequencies for range

greater than 12150 m

24

25

26

27

x

3.6

3.7

Measurement Channel SNR (dB) as a function of frequency

for 15 m/s wind speed.

Measure link margin for uniform PLS=148 dB.

28

29

4.1 Transmission loss and link performance are highly frequency

dependent. As a result, the available transmission bandwidth

will vary highly with range for a specific transmit power. This

figure shows channel SNR with a wind speed of 5 m/s.

30

4.2 Available bandwidth in the 0-70 kHz spectrum as a function

of range for a family of specified channel SNRs. Wind speed

is 5 m/s.

31

4.3

4.4

Channel SNR as a function of wind speed Ws=0 m/s


32

32

4.5

4.6



33

33

4.7

4.8

Channel SNR as a function of wind speed Ws=20m/s


34

34

4.9

4.10

Range-dependent bandwidth in the 0-70 kHz spectrum as a

function of wind speed Ws=0m/s



35

35

4.11

4.12

4.13


function of wind speed Ws=10 m/s





36

36

37

4.14 Range-dependent bandwidth in the 0-70 kHz spectrum as a

function of wind speed e) Ws=20, f) Ws=25 m/s

37

xi

LIST OF SYMBOLS

AN - Ambient Noise Spectrum Level of the environment

D - Shipping traffic coefficient

DIr - Directivity Index of the receiver

DIt - Directivity Index of the transmitter

Eb - Energy required per bit of information

F - Frequency in kHz

Gr - Receiving Antenna Gain

Gt - Transmitting Antenna Gain

KB -

Boltzmann's constant =

LM - Link margin

Ln - Noise Factor

Ls - Free Space Path Loss, spreading and atmospheric

attenuation

N0 - Thermal receiver noise

Pr - Received Power, equivalent to SNR (all quantities in dB)

PSL - Pressure Spectrum Level of transmitting platform

Pt - Transmitted Power

R -

Data rate

R - Range in meters

SNR - Signal to Noise Ratio at the receiver

xii

T0 -

Receiver temperature in degrees Kelvin

W - Bandwidth

Ws - Wind speed m/s

α - The attenuation coefficient in dB/km

CHAPTER 1

INTRODUCTION

1.1 Background of the Research

The availability of affordable and sophisticated digital signal processing has

enabled modern undersea acoustic communications systems. Advances in this field

have opened the door to autonomous sensors and untethered vehicles capable of

networked operations in the undersea environment. For radio frequency (RF)

communications, link budgeting is commonly used to predict system performance in

a representative environment. The link budget estimates the signal level at the

receiver for a given transmit power and antenna configuration and accounts for

environmental factors such as transmission loss and interference.

This project shows that the link budget can be readily applied to an undersea

acoustic communication system using the same principles as the RF link budget. The

acoustic link budget combines all terms of the active sonar equation to provide a first

order approximation of signal available at the receiver.

Link budget is a method for studying the effect of ambient noise such as wind

speed, shipping density and thermal noise on the underwater acoustic signal. It

analyses the link margin at the receiver. The link margin is the difference between

the required power to noise ratio and the receive power to noise ratio at the receiver.

The link budget for underwater acoustic signal estimates the signal level at

the receiver for a given transmit power and antenna configuration and accounts for

2

environmental factors such as transmission loss and interference. Link budget

analysis for underwater acoustic channels is considered as one of the means of

communication more difficult today. Attenuation coefficient of the underwater

acoustic supports deployment to the best acoustic low frequencies and bandwidth

available to communicate is very limited. Underwater communications that used

wireless acoustic communication have several of applications in underwater war. So,

Implementation of security wireless underwater communications is of great

important to extend the network war under the water. However, underwater acoustic

communication is the effect of ambient noise on the signal so the ambient noise is

reduces the signal to noise ratio limited by the result is reduce the link margin. So in

this project we will use the link budget analysis for underwater acoustic

communication to improve the signal to noise ratio so the result is increase the link

margin. The link margin is the difference between the received signal to noise ratio

and the required signal to noise ratio.

In the next chapter, we develop a link budget model as a form of the sonar

equation. A link budget is a method used for expected the signal to noise ratio (SNR)

for given parameters such as transmit power, antenna gain, propagation loss, and

interference. This project shows that the link budget can be readily applied to an

underwater acoustic communication system using the same principles as the radio

frequency (RF) link budget. A theoretical model shows how the link budget changes

with varying wind values. The acoustic link budget combines all terms of the active

sonar equation to provide a first order approximation of signal available at the

receiver (Houdeshell, 2001).

3

1.2 Problem Statement

The link budget method of acoustic propagation analysis is a simplified

technique providing the analyst with a first-order estimate of link performance. There

are inherent inaccuracies that must be considered, all of which require incorporation

of physics based propagation modeling.

Therefore, the statements of the problems in this research are as follows

1. Low Propagation Speed: Underwater acoustic waves have a propagation

speed around 1500m/s .The low propagation speed leads to a large

propagation delay.

2. Ambient Noise: The communication link is strongly affected by ambient

noise like shipping density, wind speed, thermal noise and animal sounds.

3. Limited Bandwidth: The acoustic frequencies depend on distance since

higher frequencies are highly attenuated. Acoustic channels have low

bandwidth.

Thus, this study evaluates the link budget necessaries to overcome these problems.

1.3 Objective of the Research

1. To design underwater acoustic communication system operating in frequency

band of 9-14 kHz and maximum range is up to 8 Km.

2. To enhance network performance, we design underwater communication

system operating in the tow telesonar frequency bands (14-19, 15-20) kHz

using M-QAM modulation and compare between Omni-directional

transducer and 9dB directional.

3. To study and analyses the effect of wind speed variation on the channel signal

to noise ratio (channel SNR) of the system.

4

1.4 Benefits of Study

Underwater networks that employ wireless acoustic communication have a

wide variety of applications in undersea warfare. Therefore, implementing reliable

wireless underwater communications is of great importance to the Navy as it extends

network centric warfare under the sea. These wireless underwater acoustic

applications include networked telemetry between sensors and base stations in

littoral waters, submarine communications, control of minefields, and control of

Unmanned Underwater Vehicles (UUVs).

41

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