i

INFRA-RED (IR) BASED WIRELESS BODY AREA NETWORKS FOR

MONITORING VITAL SIGNS

A Thesis Submitted By

Attiya Baqai

In fulfillment of the requirements for the degree of

Doctor of Philosophy

In

Electronic Engineering

Department of Electronic Engineering

Faculty of Electrical, Electronic and Computer Engineering

MEHRAN UNIVERSITY OF ENGINEERING & TECHNOLOGY

JAMSHORO

2015

ii

This Thesis is Dedicated

To

My Abbu Dr. Waheed-Uddin Baqai

and my Late Ammi Saleema Baqai

iii

MEHRAN UNIVERSITY OF ENGINEERING & TECHNOLOGY

JAMSHORO

This thesis, written by Ms. Attiya Baqai under the direction of her supervisors and

approved by all the members of the thesis committee, has been presented to and accepted

by the Dean, Faculty of Electrical, Electronic and Computer Engineering, in fulfillment

of the requirements of the degree of Doctor of Philosophy in Electronic Engineering.

Supervisor Co-Supervisor

Internal Examiner External Examiner

Director, IICT Dean, Faculty of Electrical,

Electronic and Computer

Engineering

Date: ______________________

iv

ACKNOWLEDGMENTS

Starting with the name of ALLAH, Most Gracious, Beneficent and Merciful. Prior to

acknowledgment, I would humbly thank Almighty ALLAH, the Most Merciful and the

Most Beneficent, who bestowed me the opportunity, wisdom and courage to successfully

complete this project. I am nothing without His help and guidance. All that I have

achieved till today are just His blessings upon me.

I am very much grateful to my Supervisor Prof. Dr. B.S Chowdhry DEAN FEECE

MUET Jamshoro, whose cooperation, support, encouragement and suggestions have

boosted me to complete this work in a timely manner. I am extremely thankful to my co-

supervisor Dr. Fahim Aziz Umrani for his scholastic and technical advice, skilled

assistance, continuous encouragement, inspiration and strong support throughout this

research. It was his knowledge and vision which made it possible to accomplish the task

and face challenges during this research. I am also very thankful to Prof. Dr. Mukhtiar

Ali Unar Director IICT for all the suggestions, motivation, support, guidance and prayers.

Special thanks to my Father, my mentor, my teacher in every walk of life, my source of

inspiration, my support, my ideal and my best friend Dr. Waheed Uddin Baqai and my

late Mother Saleema Baqai who always dreamed high for me and celebrated my each and

every small to big success.

I am grateful to my family, my Phuppo for taking care like a mother throughout this

journey, my elder phuppo who was there to help me to start this journey, my sisters

(Amber & Nausheen), their husbands and their kids Shariq, Shayan & Haris. Haris even

v

played the role of my experimental subject. I am very thankful to him as he is only 6

years old but he very patiently and sensibly let me put on all the sensors upon him for

taking readings. I can’t express my gratitude to each family member for giving me free

hand to study, for always supporting me, for bearing my absence due to my tough

schedule and work. This research would not have been accomplished if I would not be

having tremendous support from home and family.

I am very much gratified to Engr. Khuhed Memon for all the motivation, moral support,

encouragement, help, guidance; either technical or non-technical, ideas for making things

possible for me and not letting me settle for less. His constant reminders to meet

deadlines, help in fully utilizing my office as lab, facilitating in acquiring equipment and

modules whenever needed and strengthening me to cross every hurdle, are highly

appreciated. His knowledge and discussions related to Matlab and Communication has

helped me a lot in completing this project. I am thankful to him from every perspective.

I want to pay my bundle of thanks to Engr. Azam for helping me out whenever I got

stuck in Microcontroller/ Hardware or Android issues. His kind & selfless nature and

technical expertise have assisted me a lot. I will always remember the discussions with

my research team in my ResearchLab1 IIT building.

This work was tested in the Red Crescent Institute of Cardiology (Hila-e-Ahmar

Hospital) Unit No-2 Latifabad Hyderabad. Special thanks to Dr. Bahadur Khan- Senior

Medical Officer Red Crescent Cardiac Hospital & CCU for his time, cooperation,

vi

discussion, suggestions and facilitation in taking experimental readings on the patients

admitted in the hospital

Great acknowledgment to Lab assistants who rendered their technical services whenever

asked with so much generosity. Mr. Mushtaq, Mr. Mohammad Ali Soomro (Lab

Assistant of Basic Electronics Lab and Digital Electronics Lab ES Dept. MUET) and Mr

Jamil (Senior IT assistant, IICT-MUET)) have significant contribution to help me around.

I am very much thankful to Engr. Sindhu and Engr. Hyder Bux for assisting me in

Optical Communication lab (TL Dept.) with their utmost cooperation and support.

Special Thanks to Mam Rosy Ilyas (Director ELDC) my teacher and my friend for all the

support, prayers, good wishes she used to give me for bucking me up, tolerating and

listening to my daily stories for the ups and down I was facing during my journey,

lending me her mobiles phones for experiments and she didn’t care that she got out of

contact, she offered all her support and enjoyed my every little success.

I would like to thank Prof. Dr. Aftab Memon, Madam Nafeesa Zaki, Prof. Dr. Faisal

Karim Shaikh and Prof. Dr. Wajiha Shah (Head of the Telecommunication and

Electronics Departments) for granting me permissions for using lab equipment within my

office and providing me resources. Many thanks to IICT Mehran UET Jamshoro for

providing this scholarship to fulfil the dream of doing doctorate.

Finally, I am thankful to all my friends, colleagues and students who have helped me or

prayed for me in this journey.

vii

TABLE OF CONTENTS

Description Page

List of Abbreviations ix

List of Tables xi

List of Figures xii

Abstract xv

Chapter 1 INTRODUCTION 01

1.1 INTRODUCTION TO WBAN 02

1.2 BACKGROUND & RATIONALE 02

1.3 MOTIVATION 04

1.4 RESEARCH QUESTIONS AND CHALLENGES 04

1.5 AIMS & OBJECTIVES 06

1.6 METHODOLOGY 07

1.7 MAJOR CONTRIBUTIONS 08

1.8 PROPOSED SYSTEM’S ADVANTAGES 09

1.9 THESIS STRUCTURE 10

1.10 SUMMARY 12

Chapter 2 LITERATURE REVIEW 13

2.1 EXISTING WBAN SYSTEMS AND THEIR

ADVANTAGES AND DISADVANTAGES

13

2.2 IEEE 802.15.6 STANDARDS, REQUIRENMENTS AND

SPECIFICATIONS

18

2.3. OPTICAL COMMUNICATION 21

2.3.1 Characteristics of Optical Communications 23

2.4. SUMMARY 26

Chapter 3 PROTOCOL DESIGN & ALGORITHM 28

3.1 PROTOCOL SPECIFICATION 29

3.2 EXPERIMENTAL SETUP AND METHODOLOGY 32

3.2.1 Patient authentication & sensor Identification 33

3.2.2 Transmission & Reception with interference

rejection

34

3.2.3 Energy efficiency 36

3.2.4 Node Joining/Un-joining 37

3.3 SUMMARY 37

Chapter 4 MOBILE APP DEVELOPMENT 38

4.1 MATLAB DATABASE DEVELOPMENT 38

4.2 MATLAB MOBILE APPLICATION 40

4.3 ARDUINO & ANDROID DATABASE WITH

ANDROID APP ACCESS

45

4.3.1 SD Card Database creation and its Access 46

viii

4.3.2 B4A Anywhere software 46

4.3.3 Developed Android App 47

4.4 SUMMARY 51

Chapter 5 PROTOTYPE DESIGN 52

5.1 SELECTION OF SENSORS 53

5.1.1 Features of e health sensor platform 53

5.1.2 Data Acquisition 55

5.2 SELECTION OF IR SOURCE 56

5.2.1 LED Drive circuitries 56

5.3 IR RECEIVERS/DETECTORS 57

5.3.1 Testing Photodiode 58

5.3.2 Testing Photo Transistor for Transceiver Design 1 59

5.3.3 IR Remote Control Receiver IC and Working of IR

Transceiver design2

61

5.4 PERFORMANCE ANALYSIS 65

5.5 EXPERIMENTAL SETUP 65

5.6 ThorLAB PIN DIODE 67

5.7 SUMMARY 72

Chapter 6 RESULTS & DISCUSSION 73

6.1 TRANSCEIVER DESIGN 1 READINGS WITH

INCREASE IN DISTANCE

73

6.2 TRANSCEIVER DESIGN 1 NOISE EFFECT

READINGS

76

6.3 EXPERIMENTAL RESULTS FOR TRANSCEIVER

DESIGN 2

78

6.4 TRANSCEIVER DESIGN 2 NOISE EFFECT READING 79

6.5 TRANSCEIVER DESIGN 3 84

6.6 TRANSEIVER DESIGN 3 READINGS AND

OBSERVATIONS

87

6.7 DISCUSSION FOR TRANSCEIVER DESIGN 3

EXPERIMENTAL READINGS

89

6.7.1 Data Rate 104

6.8 SUMMARY 108

Chapter 7 CONCLUSION, LIMITATIONS AND FUTURE

RECOMMENDATIONS

109

7.1 ACHIEVEMENTS 109

7.2 LIMITATIONS 113

7.3 FUTURE RECOMMENDATIONS 114

7.4 SUMMARY 114

References 115

ix

LIST OF ABBREVIATIONS

3rd

-Generation = 3G

4th

-Generation = 4G

Amplitude Modulation = AM

Amplitude Shift Keying = ASK

Basic4Android = B4A

Bit Error Rate = BER

Bluetooth Low energy = BLE

Bayonet Neill–Concelman = BNC

Binary Phase Shift Keying = BPSK

Continuous Wave = CW

Data+Control = D+C

Direct Current = DC

Double Side Band = DSB

Digital Storage Scope = DSO

Elliptic Curve Cryptography = ECC

Electrocardiograms = ECG

Electromyography = EMG

Electromagnetic Interference = EMI

Elettronica Veneta = EV

Federal Communications Commission = FCC

Free-space optical = FSO

Gaussian frequency shift keying = GFSK

General Packet Radio Service = GPRS

Galvanic Skin Response = GSR

Integrated circuit = IC

Integrated Development Environment = IDE

Institute of Electrical and Electronics Engineers = IEEE

Intensity Modulation/ Direct Detection = IM/DD

Infra-Red = IR

Inter Symbol Interference = ISI

Industrial, Scientific and Medical = ISM

Light Emitting Diode = LED

Line of Sight = LOS

Media Access Control = MAC

Message Authentication Code = MAC

Multiple Access Interference = MAI

Medical Implant Communication Service = MICS

Non Line of Sight = NLOS

Non Return to Zero = NRZ

On Off Keying = OOK

Operational Amplifiers = OPAMP

x

Optical Wireless Communication = OWC

Pulse Amplitude Modulation = PAM

Personal Area Networks = PAN

Physical layer = PHY

Pulse Position Modulation = PPM

Phase Shift Keying = PSK

Pulse Width Modulation = PWM

Quality of Service = QoS

Rapid Application Development = RAD

Regulatory Cooperation Council = RCC

Radio Frequency = RF

Received = Rx

Return to Zero = RZ

Specific Absorption Rates = SAR

Suppressed Carrier Modulation = SCM

Secure Digital = SD

Signal to Noise Ratio = SNR

Structured Query Language = SQL

Single Side Band = SSB

Test Point = TP

Transmitted = Tx

User Datagram Protocol = UDP

Ultra Violet = UV

Ultra-Wide band = UWB

Visible Light Communication = VLC

Wireless Body Area Networks = WBAN

Wireless Local Area Network = WLAN

Wireless personal Area Networks = WPAN

xi

LIST OF TABLES

Description

Page

Table 2.1 Comparison between RF and IR 24

Table 3.1 Specifications for S, I, D and Sensor Information 31

Table 5.1 Various IR Remote Control Protocols 63

Table 5.2 Protocols supported by Arduino IR Remote Library 63

Table 5.3 MCM31/EV Encoding schemes and their respective data

rates

70

Table 6.1 Experimental Readings for Transceiver Design 1 with

Distance

75

Table 6.2 Experimental Readings for Transceiver Design 1 with Noise

effect

77

Table 6.3 Experimental Readings with Noise for Transceiver Design 2 80

Table 6.4 Experimental Readings with Noise for BER in Transceiver

Design 2

81

Table 6.5 Received Power Readings taken at Research Lab1 IIT

building from PIN RX for change in light due fluorescent

bulbs switching.

85

Table 6.6 Readings taken while switching the light at Research lab1

IIT Building MUET by ambient light sensor of Smart Phone

86

Table 6.7 ThorLAB DET100A Large Area Silicon Detector Electrical

Specifications

87

Table 6.8 Transceiver Design 3 Readings with varying one parameter

at a time

88

Table 6.9 Matlab required parameters calculation with 25KHz and

50KHz sampling frequency for plotting eye diagram and

constellation diagram.

91

Table 7.1 Summary of Research in context of specific parameters 112

xii

LIST OF FIGURES

Description Page

Fig. 1.1 Issues related to WBAN 6

Fig. 2.1 WBAN Applications 14

Fig. 2.2

Existing technologies available for WBAN and their

comparison

15

Fig. 2.3 WBAN Functional Requirements 19

Fig. 2.4 Power vs Data Rate comparison of different wireless standards 20

Fig. 2.5 WBAN requirements according to applications 21

Fig. 2.6 Problems in IR links and their proposed solutions 25

Fig. 3.1 Packet Format and Specifications 29

Fig. 3.2 Conceptual Diagram 32

Fig. 3.3 Circuits for simple IR Transmitter and Receiver 33

Fig. 3.4 System Flowchart 34

Fig. 3.5 Interference creation with various Remote controls (a)

TV/DVD Remote (b) AC remote

35

Fig. 3.5(c) Snapshot of Arduino IDE while receiving all signals i.e. ID1,

ID2 and remote control

36

Fig. 4.1 Flowchart for database creation 39

Fig. 4.2 Snapshot showing various Fields of created database 40

Fig. 4.3 Matlab Mobile App Script Algorithm 41

Fig. 4.4 Script execution output on Matlab Mobile App

42-45

Fig. 4.5 RAD tools by Anywhere Software 47

Fig. 4.6 Android App Screen Shots 48-51

Fig. 5.1 Proposed Prototype WBAN 52

Fig. 5.2 e-health sensor complete kit 54

Fig. 5.3 Sensor Shield 55

Fig. 5.4 LED Drive Circuits 57

Fig. 5.5 Photodetectors 58

xiii

Fig. 5.6 Photo Diode Response in Open Circuit 59

Fig. 5.7 Photo Diode response with Resistor Biasing when a signal

from Remote control is given

59

Fig. 5.8 Photo Transistor Receiver Design 60

Fig. 5.9 Block Diagram and Prototype of IR Transceiver Design1 61

Fig. 5.10 Block Diagram of IR Transceiver Design 2 62

Fig. 5.11 Sony SIRC Protocol & Phillips-RC5 Protocol 64

Fig. 5.12 Test Set-up for Noise Effect Measurements 66

Fig. 5.13 Noise Signal generation from Agilent 33250A Function

generator/ Arbitrary Waveform generator and its effect in

transmission and reception

67

Fig. 5.14 EV/MCM31 Digital Modulation Trainer 69

Fig. 5.15 IR Transceiver using ThorLAB PIN and MCM31/EV Trainer 71

Fig. 6.1 (a-c) Photo Transistor Response with increasing distances 74

Fig. 6.1(d) Effect of increasing Distance on SNR for Transceiver

Design1

75

Fig. 6.1(e) Matlab Simulation for SNR vs BER with varying distance for

Transceiver Design 1

75

Fig. 6.2(a) Results with adding Noise offset from 0V to 2V 76

Fig. 6.2(b) Effect of increasing Noise DC offset on SNR Value for

Transceiver Design 1

77

Fig. 6.2(c) Matlab Simulation for SNR vs BER with DC offset Noise

Value for Transceiver Design 1

77

Fig. 6.3 Experimental setup for Transceiver Design 2 (Link distance up

to 4 feet)

78

Fig. 6.4 Experimental Results with Receiver up to 4 feet apart (a) Sony

Protocol (b) RC5 Protocol

79

Fig. 6.5(a) Experimental Results for Effect of adding Noise offset (RC5

Protocol)

79

Fig. 6.5(b) Experimental Results for Effect of adding Noise offset (Sony

Protocol)

80

Fig. 6.5(c) Effect of Distance & Noise on SNR in IR Receiver IC 80

Fig. 6.5(d) BER curve with noise offset in Transceiver Design 2 82

Fig. 6.6 Comparative results for performance analysis of transceiver

design 1 & 2

83

Fig. 6.7 Research Lab 1 (IIT building MUET) Experimental setup and

lab dimensions

84

xiv

Fig. 6.8 Matlab plots with 2-PSK with 2 lights ON a) I & Q amplitudes

b) Eye Diagram c) Constellation

92

Fig. 6.9 Matlab plots with 2-PSK with 4 lights ON a) I & Q amplitudes

b) Eye Diagram c) Constellation

93

Fig. 6.10 Constellation diagrams for 2-PSK with a) No light b) 2 lights

c) 4 lights

94

Fig. 6.11 Eye diagrams for 2-PSK with a) No light b) 2 lights c) 4 lights 94

Fig. 6.12 Constellation diagrams for 4-PSK with a) No light b) 2 lights

c) 4 lights

94

Fig. 6.13 Eye diagrams for 4-PSK with a) No light b) 2 lights c) 4 lights 95

Fig. 6.14 Eye diagrams for FSK with a) No light b) 2 lights c) 4 lights 95

Fig. 6.15 Eye diagrams for ASK with a) No light b) 2 lights c) 4 lights 95

Fig. 6.16 SNR curves for varying (a) Angle (b) Distance (c) No of

Lights for ASK

96

Fig. 6.17 SNR curves for varying (a) Angle (b) Distance (c) No of

Lights for FSK

97

Fig. 6.18 SNR curves for varying (a) Angle (b) Distance (c) No of Light

for 2PSK

98

Fig. 6.19 SNR curves for varying (a) Angle (b) Distance (c) No of Light

for 4PSK

99

Fig. 6.20 BER vs SNR curves for varying (a) Distance (b) Angle(c) No

of Light for ASK

100

Fig. 6.21 BER vs SNR curves for varying (a) Distance (b) Angle(c) No

of Light for FSK

101

Fig. 6.22 BER vs SNR curves for varying (a) Distance (b) Angle(c) No

of Light for 2PSK

102

Fig. 6.23 Fig. 6.23: BER vs SNR curves for varying (a) Distance (b)

Angle(c) No of Light for 4PSK

103

Fig. 6.24

(a,c,e,g)

Test set up for Binary ASK Transceiver for Data Rate

Observations

104

Fig. 6.25 Information Vs Modulated signal-(b,d,f,h) Tx vs Rx signals at

Node a and Node b

105-107

xv

ABSTRACT

Due to the technology advancement in many fields, life has become easy and safer. We

come across new devices and gadgets every day. This has also improved health care

splendidly. The wearable technology is now part of our daily life and in order to keep one

updated about his/ her health, daily or routine tests are must. Wireless Body Area

Networks is one of that advent of science and technology which has served as a blessing

to reduce health risks. The patients can get their checkups done while staying at their

homes without even going to the hospital and share that information with their Doctors or

Care giver through Smart phones. This reduces the unnecessary expenses and only

initiated when it is required.

WBAN are the networks comprising of many sensors capable of monitoring various vital

signs within human body range (within 2m). These sensors after sensing the

physiological data send this information to a controlling node from where it can be

transferred to hospital, clinic, medical staff or anywhere. Most of the research that is done

for developing WBANs relies on RF, microwave or Ultra-Wide Band Technology. These

technologies are mostly based on Wireless Personal Area Networks WPAN and lack in

fulfilling the requirements of WBAN. They have frequency licensing issues and the

Electromagnetic spectrum has become so overcrowded that researches are trying to find

alternate solutions. The WBAN based on these technologies interfere with the medical

equipment/ devices and vice versa, also they cannot be used in airplanes, they have power

and health issues too.

xvi

In order to address these issues, an alternative of utilizing Optical Wireless

Communication in form of Infra-red signaling has been proposed in this thesis for

WBAN which has huge unregulated free bandwidth available with no licensing issues.

OW links are inherently secure as they confine within the room, fulfilling the major

requirement of WBAN. For this a prototype WBAN has been developed by designing

optical transceivers using cheap and low power components.

An e-health sensor platform by Cooking Hacks Libellium (Spain) has been used in this

research to collect physiological data from the sensors worn over the body. This shield is

compatible with Arduino and comes with an eHealth library. The shield has other

connectivity options but does not include Infra-red connectivity. The transceiver to

transmit and receive IR signals is designed in this research work and the e-health library

is modified using Arduino IR Remote library to support not only this connection but also

to implement security protocol developed for this research. The issues related to WBAN

are investigated and a novel light weight protocol with security and interference rejection

has been developed in this thesis.

Various experiments were performed to observe the effects on the Infra-red link in the

laboratory by varying link distance, angle deviation from LOS, noise, ambient light,

modulation scheme etc. The prototype investigated gives satisfactory results up to 7 feet

(around 2m) with 30 to 60 degrees deviation from LOS. The low data rate requirement

for physiological data and waveform is achieved with acceptable accuracy, which can

further be enhanced to fully exploit the OW high data rate potential.

xvii

The Mobile App developed in this research makes it easy to visualize vital signs data in

forms of charts and graphs. The results can easily be shared or stored for later use.

Initially the results were tested on Matlab Mobile. After getting successful results a

standalone Android App was developed using Basic4Android.

The research presented in this thesis investigates the feasibility of Infra-red signaling

scheme for WBAN and propose it as an alternative approach to the presently deployed

wireless technologies for WBAN by highlighting the potential of OWC.

1

CHAPTER 1

INTRODUCTION

Due to the tremendous advancement of technology in consumer electronics, wireless

transmission techniques, sensors, low power devices and microelectronics [1] the world

is becoming smarter day by day and the burden of the user is being relieved day by day as

things have become easy to access and share with others within seconds. This remarkable

technology advancement has benefited every field. One of such field is the Health care.

With the introduction of the concepts like telemedicine, e-health and m-health, number of

cases that suffered due to lack of availability of resources, access, communication and

delay have greatly reduced. E-health uses internet and electronic processes in order to

transmit medical information whereas M-health is an abbreviation of Mobile health. It

uses Mobile devices for health and clinical information. The m Health field has emerged

as a sub-segment of e Health. Telemedicine uses telecommunications and information to

exchange clinical information. In order to have healthy life frequent tests and checkups

have become the need of today which in critical cases are necessary and must be

monitored continuously. Besides the critical cases, there is an increase in number of

elderly people each year who need periodic or regular checkups but the hospital visits,

out of reach clinics/hospitals/medical centers, unavailability of medical staff, the

transportation difficulties and expenses demands the development of some easy way out

[2]. The advent of WBAN is the solution for the afore mentioned problems which not

2

only improves and facilitates health care but also lifestyle, entertainment, gaming, fitness,

assisted living and many more. Thus WBAN can be utilized to reduce rush at the medical

centers, to efficiently utilize the resources and staff, to improve the lifestyle & health

awareness of the people. Due to easy and fast access WBAN also improves the efficiency

of staff.

1.1 INTRODUCTION TO WBAN

Wireless Body Area Network (WBAN) is the wireless network made of small sensor

nodes with sensing or actuating capabilities which can also have some sort of storage and

processing. The WBAN are specific to the applications in which the human body is

directly involved with sensors being installed within the human body range i.e. in, on or

around the body. Typical coverage of transmission from these sensors is short range

around 2m which is different form WPAN that covers around 10m. Due to the difference

in requirements of WBANs, IEEE 802.15.6 has set a separate standard to fulfill the needs

specific to human body like low power, low data rate, assurance of skin and tissue safety.

Research and study reveals that the amplitude and frequency ranges for human

physiological signals are quite low and hence low data transmission rate and low

sampling frequency would be adequate where as the number and type of sensors to be

deployed depends upon the application and infrastructure [3].

1.2 BACKGROUND & RATIONALE

Depending upon the range, the applications for short-range communications can be

considered in the form of three networks WBAN, WPAN and WLAN they vary in the

3

distances for the coverage, WLAN being in the range of few tens of meters up to WBAN

within range of typically 3 to 2 meters.

In Optical Communications the devices or the nodes utilize communication via short-

range wireless signals operating on optical carrier wavelengths having different

characteristics from their counterpart radio. Optical Wireless Communication (OWC) or

Free-space optical (FSO) technology has recently attracted researchers to explore as a

possible alternative to traditional optical fiber or radio-frequency or microwave links to

meet the requirements of high-bandwidth next generation networks. OWCs are found

especially suitable but not limited for short-range communication systems [4].

For short-range indoor wireless communications, Radio frequency as well as Infrared

both have been used frequently and reported in literature. But due to a number of reasons

preference is given to OWC in specific cases from which to name a few is its low cost for

high bandwidth, is not much effected by electromagnetic interference (EMI), no licensing

required for the spectrum, the components are cheap, having small form factor, light in

weight and power consumption is very low. Majority of the work that is reported for

WBAN has been done using radio, microwave, Ultra-Wide band Bluetooth Low energy

and ZigBee especially ultra-wideband (UWB) [5-9] which have licensing and power

issues. The Radio spectrum has become so over crowded that the researches are trying to

find suitable alternatives. One of the possible solutions is the use of optical signaling

because of its unique features as mentioned above.

4

1.3 MOTIVATION

Fiber Optics have been used for a long time as high speed backbone links so if the optical

Wireless links are stablished they could easily be connected to the pre-deployed

backbone links. Indoor and outdoor systems OW present all the benefits of optical fiber-

based systems with easy and quick installation at a low cost. As optical signals are

confined within a room so this feature provides interference free communication with

frequency reuse in nearby cells/ rooms. The availability of huge bandwidth in THz range

makes it better choice than RF. The same geographical area can be divided in a number

of cells and a single wavelength can be used in the cells without resorting to the

frequency reuse [10-12]. This all can happen with minimum or no inter-channel

interference. The cell size and shape can be specifically defined depending upon the

desired application which is a distinct feature in optical wireless systems. The optical

signals do not interfere with medical equipment radiations, neither these radiations from

medical equipment interfere with optical signals, this make OWC systems extremely

useful in hospital or clinical environment. They are also useful in environments where

use of RF signals is forbidden or can be dangerous like in airplanes etc. So OW can be

extremely suitable in the environments where security is of prime concern.

1.4 RESEARCH QUESTIONS AND CHALLENGES

The OW wireless signaling presents distinctive advantages as mentioned in the previous

section but contrary to the RF system these links pose some disadvantages as well. To

name a few the drawbacks include limitation in mobility, the links get blocked, potential

5

risk of eye and skin damage, connectivity is not easy and as RF links Non-Line of sight

links also suffer from multipath-induced ISI. There are some solutions to the above

mentioned problems: Eye and skin can be made safe from potential hazards if (i) a higher

wavelength of 1550 nm is used, at this wavelength the cornea and lens absorbs the laser

beams and this wavelength is not focused on the retina [13], it also provides compatibility

with the backbone fiber optic links third transmission window, (ii) power-efficient

modulation schemes can be utilized. From different configurations, the most bandwidth

and power efficient is the line of sight link as there is no multipath hence there is no loss

or pulse dispersion and a highly concentrated optical power is achieved [9]. But there are

some limitations to LOS links as they need accurate alignment, they encounter link loss

when get blocked, all these limitations restrict them to particular applications which are

free from blocking. Broadened transmitted beams can be used to enhance coverage area

and provide mobility at the cost of power efficiency suggested in [14, 15], Usage of non-

line of site links can also serve the purpose of improving coverage area.

WBANs are recent phenomenon [16] and most of the research being carried out in this

area is in its infant stage, and therefore, plenty of room to work. The issues that need to

be considered and addressed are illustrated in Figure 1.1.

6

Fig. 1.1 Issues related to WBAN

Keeping in mind the above mentioned challenges, the focus of attention in this research

project is on the following aims and objectives.

1.5 AIMS & OBJECTIVES

The main focus of this research, in relation to the application chosen i.e., WBANs, is put

on OW for indoor environments.

The specific, but not limited to, objectives of this study are:

To analyze the performance of Optical Wireless Communication techniques in

Wireless Broadband Area Networks (WBANs).

To develop a prototype BAN system using optical communications (IR), and

choose different vital signs to test the data transmission.

7

To explore various techniques (such as modulations, forward error coding, and

artificial intelligence, etc.) to enhance the system performance of WBAN devices

for medical applications.

1.6 METHODOLOGY

Following methodology is adopted for this research work:

Optimize and analyze vital sign sensors.

Interfacing of sensors in Wireless Body Area Networks.

Compare Optical signaling with its counterpart, i.e., Radio.

Develop mathematical model for a prototype WBAN device capable of measuring

vital signs.

Implement WBAN test bed.

Test and analyze the performance of WBAN test bed.

The primary aim of this research is to study, examine, develop, design, improve and

demonstrate the applications of Infra-red signaling in WBAN. A prototype WBAN

system capable of measuring different vital signs using sensors, operating on optical

signals is established. The specificities of IR based WBAN are highlighted by comparing

them with the existing WBANs predominantly implemented on UWB systems. The

technical challenges related to implementation of OW link and for developing a prototype

WBAN as mentioned earlier are considered.

8

In order to develop a prototype WBAN system with Infra-red signaling scheme an e-

health sensor platform from Libellium is used comprising of Blood Pressure sensor,

Temperature sensor, Galvanic Skin Response sensor, ECG sensor, Air Flow sensor and

Position sensor. At first, the prototype was developed by keeping in mind that it should

remain cost effective and power efficient design. Secondly the feasibility of WBAN also

depends on network-level issues such as how efficient the communication protocols are.

To deal with the first issue, the low cost and inexpensive optical transceiver is adopted.

Moreover, their integration into future wireless heterogeneous networks gains importance

as a necessary step to shape the 4G landscape. Furthermore, the necessary modelling and

design implementation is carried out in a way that the overall system design remains cost

effective.

1.7 MAJOR CONTRIBUTIONS

A cost effective prototype WBAN system is developed using least expensive and

easily available components for optical transceiver.

A novel protocol with patient and node identification for optical WBAN with

inherent security and interference rejection is developed and tested using infrared

signaling.

The performance of the system is tested and analyzed through SNR, BER, eye

diagrams and constellation diagrams over various parameters such as Distance/

Spacing, Noise, Angle (Orientation) and modulation schemes.

9

Various detectors/ Receivers including phototransistor, photodiode, IR remote

receiver, and ThorLAB photodiode are tested for the development of the

prototype WBAN.

A user friendly mobile app is developed using Basic4Android to acquire, store,

visualize and share the health status/ vital signs data of a person.

1.8 PROPOSED SYSTEM’S ADVANTAGES

Because our proposed WBAN system is based on optical signaling:

- The cost is reduced.

- Power requirement is also reduced.

- Compatible with human body environment as opposed to UWB.

Further, we also aim to work towards standardization of the WBAN by proposing

a new system compatible with the requirements posed by WBAN IEEE 802.15.6

task group.

The proposed system enables medical staff to perform following remote

functions:

- Monitoring can be done in real-time.

- Diagnosis can be done at earlier stages before entering into an alarming

state.

- Possible dangerous diseases can be cured.

10

Additionally, through wire/ wireless communication channels, the medical

professionals can perform the medical diagnosis similarly patients can also

consult their doctors via same channels.

Many chronic diseases can be avoided by implementing the proposed healthcare

system. It can also provide long lasting smarter solution at low cost for continuous

monitoring and managing patients to provide better care.

1.9 THESIS STRUCTURE

In Chapter 1 general overview about the WBAN has been discussed. This chapter briefly

discusses the existing technologies used and available for WBAN. It also points some key

features of optical communication which served as motivation to choose infrared

signaling for design of WBAN prototype in this research. The research challenges,

objectives, proposed methodology and summary of major contributions for this research

are also conversed in this chapter.

In Chapter 2 the existing WBANs, their advantages and disadvantages have been

discussed. It also mentions standards, key requirements and specifications laid down by

IEEE 802.15.6 Task Group 6 specially made for WBAN. This chapter highlights the

characteristics of OWC, compares them with its counterpart i.e. RF communication and

argues for the feasibility of infrared signaling for WBAN highlighting its advantages over

RF. This chapter also puts some light on the problems encountered by Infra-red links and

proposes solutions to address them.

11

The development of a novel protocol for this research having key features of node and

patient identification with interference rejection from other IR sources is highlighted in

Chapter 3 . The protocol specifications and its working algorithm along with simple IR

Transceiver designs are discussed in this chapter. The protocol is specially made light in

computation and processing to incur least possible overhead while addressing the security

and privacy requirements of WBANs.

In Chapter 4 the development of the mobile apps to visualize the physiological data in a

user friendly manner is covered. This chapter presents the app development and their

results in numerical as well as graphical screen shots form. Two mobile app platforms i.e.

Matlab Mobile and Basic4Android are used in this research and discussed in this chapter.

In Chapter 5 the prototype development for the IR based WBAN has been investigated. It

highlights the interfacing of sensors, their connectivity in WBAN, the issues encountered

in choosing transmitter and detectors for the prototype development and their possible

solutions. This chapter also explains the experimental set up and describes each

component, board and equipment specifications, usage and limitations in the

experimental work for this research.

In Chapter 6 the experimental results of the selected components and transceiver designs

for the Prototype WBAN are discussed. The experimental readings and observations

made for the established Infra-red link are analyzed in this chapter for various parameters

such as noise, ambient light, angular displacement of receiver from transmitter’s LOS,

link distance and data rate.

12

Finally in Chapter 7 a conclusion is made for the thesis by highlighting the achievements

made in this research project. It also enumerates the limitations of the project and gives

suggestions for the future extensions for the research carried out in this thesis.

1.10 SUMMARY

In this chapter basic idea of the WBAN was discussed along with brief discussion of the

existing technologies used and available for WBAN. It also points some key features of

optical communication which served as motivation to choose infra-red signaling for

design of WBAN prototype in this research. The research challenges, objectives,

proposed methodology and summary of major contributions for this research are also

conversed in this chapter.

13

CHAPTER 2

LITERATURE REVIEW

The research in this thesis aims to develop of a prototype WBAN, based on Infra-red

signaling. In order to develop such prototype a thorough study about the existing

WBAN’S was needed in order to know the main requirements of WBAN. Optical

Communication has its own unique characteristics so a review has been done to explore

the specific features of OW that can be utilized in WBAN. Hence for this research the

literature review is done in the following three directions:

Studying about already existing WBAN systems and noting their advantages and

disadvantages.

Making the proposed system design compatible with IEEE 802.15.6 standard and

therefore finding its requirements/ specifications.

Exploring the Optical Communication techniques and other skills required to

execute this project.

2.1 EXISTING WBAN SYSTEMS AND THEIR ADVANTAGES AND

DISADVANTAGES

WBAN (Wireless Body Area Network) is derived from the Wireless Sensor Network

which is a very vast field covering numerous applications in different kinds of

environments and ranges. The WBAN are specific to the applications in which the human

14

body is directly involved with sensors being installed within the human body range. Due

to the direct human involvement main concerns related to WBAN are security, privacy

and safety from health issues. The WBAN can be used in variety of applications some of

which are shown in Figure 2.1. In general, from application perspective, WBAN can be

broadly classified in Medical and Non-Medical Applications [2]. Medical applications

can further be classified as wearable and implanted.

Fig. 2.1 WBAN Applications

A WBAN can be described as a set of sensors which are miniaturized in nature, low

power, low cost that can be worn or can be implanted within the human body. They

can have some sort of storage as well as processing capability or can simply be sensor

nodes. These nodes collect physiological data also called vital body parameters or

signs. Some of the common vital signs include Body temperature, Blood oxygen

Saturation, Blood pressure, electrocardiograms (ECG), Pulse rate, heart rate etc. [2].

15

These vital body conditions and movements can be continuously monitored for the

heart attack patients, diabetic or asthma patients. The data from the sensors is sent to

a controlling node which is more intelligent node in terms of processing capability.

This node aggregates the sensors data, performs signal processing and transmits it to

the home base station via existing wireless technologies for WBAN such as Ultra-

Wide Band, Microwave, ZigBee, Bluetooth or Optical Wireless etc. Chakraborty, C.,

Gupta, B., & Ghosh, S. K. (2013) in Figure 2.2 [2] compares the technologies/

standards and their specifications available for WBAN. The data from the home base

station can then be sent to the doctor, medical staff, clinic, caregiver, hospital or

anywhere in real time where the user wants to send the data for further analysis, help

or action.

Fig. 2.2 Existing technologies available for WBAN and their comparison (Source: A review on telemedicine-based WBAN framework for patient monitoring. Telemedicine and e-

Health, 19(8), p.622)

16

[17] Classifies WBAN into three classes as follows which is the basis of WBAN

architecture also known as three tier system.

- Intra-WBAN (communication between sensors and WBAN coordinator).

- Beyond WBAN (communication that is held between coordinators and

outside world).

- Inter-WBAN (communication between WBANs).

Preliminary Study of Wireless Body Area Networks reveals that:

- Majority of WBAN are using UWB (i.e. radio/ microwave) technology

[5-7, 9, 12, 18-27].

- They are developed over PAN technology.

- Existing WBANs have issues with QoS [23].

The main disadvantage of using UWB (i.e. radio/ microwave) technology is use of large

number of antennas which make a multi-hop wireless network which are very close to

human skin. The radio signals also have the effects on human body including organs or

tissues. It also effects if there is any other medical implants such as orthopedic devices,

cardiac pacemakers, and cochlear implants. [19] Discusses the issues related to existing

WBAN technologies with power consumption, SAR, frequency regulations and

transceiver considerations for WBAN for medical applications. Most of the Existing

WBANS are using PAN technologies using RF technologies from which Bluetooth or

ZigBee are more common which have the power consumption, health safety and

frequency licensing issues although low power versions of these technologies i.e.

17

Bluetooth® low energy (LE) and ZigBee RF4CE are also there but they waste the

spectrum and need cautious planning while deployment in order to avoid interference.

[28] Reports about the research for security concerns related to some LE Bluetooth

devices. The people carrying these devices may be unaware but they can easily be

tracked because of a unique identifier that these devices transmit. Most of the work done

in WBAN is reported on the MAC layer protocols. [17] States that although there are

limitations and additional requirements for WBAN which are not fulfilled by existing

technologies and standards but they are still in use mainly because of the unavailability of

the current IEEE 802.15.6 submissive devices. They impose key limitations in terms of

acquired data rates, communication range, peak-power consumption, created RF

interferences, and effective on-body communications. Both ZigBee and Bluetooth LE use

128-bit keys to implement their security mechanisms. These technologies overcome the

common issues related with infra-red like line of sight, interoperability and limited

improved features but they do not cater the breath of security, interference rejection,

frequency reuse, cost and packet payload overhead.

In WBANs equal emphasis should be made on the security as well as system

performance, therefore, it is a challenging task to integrate a high-level security in such

resource-constrained networks. Several prototype implementations of WBANs that deal

with QoS and energy efficiency are reported in the literature, however, less research is

found on the aspects of data security and privacy; also the presented solutions are not

much mature.

18

In order to ensure safe and successful transmission and reception the security

requirements for WBAN such as Confidentiality, Integrity, Authentication, Availability

and Data freshness are to be fulfilled. To address security challenges, issues,

requirements, threats and attacks various solutions/ schemes and protocols are proposed

from which Message Authentication code (MAC), hardware or software encryption

techniques, symmetric or asymmetric cryptography, heterogeneous or hybrid

cryptosystems, Bio metric key establishment, Private or Public keys distribution, Elliptic

Curve Cryptography (ECC) and Hash Functions are some of them[29-45]. All existing

security solutions which involve cryptographically strong protocols incur too much

computation and communication cost for body sensors.

2.2 IEEE 802.15.6 STANDARDS, REQUIRENMENTS AND SPECIFICATIONS

Due to the deficiency of PAN to address the issues related to the requirements and

standardization IEEE made a new Task group in 2007. Alam, M. M., & Hamida, E. B.

(2014) have summarized this standard in [17] which is specifically designed to meet the

WBAN Functional requirements as shown in Figure 2.3.

19

Fig. 2.3 WBAN Functional Requirements

(Source: Alam, M. M., & Hamida, E. B. (2014). Surveying wearable human assistive technology for life

and safety critical applications: Standards, challenges and opportunities. Sensors, 14(5), p.9160)

The main objectives of this standard are to provide communication for short range

usually within the vicinity of a human body (sub meter range typically up to 2 to 3

meters), the devices should offer less power consumption with high security and privacy.

The devices should SAR compliant, MICS, ISM compatible where possible (low

cost).The data rate up to 10Mbps are required if video streaming or high quality images

are to be transmitted. Figure 2.4 [17] illustrates the power requirements vs Data Rate for

20

IEEE15.6 WBAN standard. The power consumption for the other standards is quite high

whereas the WBAN requirement is just of 0.1 to 1 mW.

Fig. 2.4 Power vs Data Rate comparison of different wireless standards

Alavikia, Z., Khadivi, P., & Hashemi, M. R. (2012) in [46] summarize the data rate,

delay, security and other parameter requirement for WBAN with respect to the

application chosen as shown in Figure 2.5. In this research Real time data comprising of

waveforms and physiological data is targeted so a bandwidth of 10 to 100Kbps would be

sufficient.

21

Fig. 2.5 WBAN requirements according to applications

(Source: Alavikia, Z., Khadivi, P., & Hashemi, M. R. (2012). A Model for QoS–Aware Wireless

Communication in Hospitals. Journal of medical signals and sensors, 2(1), 1)

The 802.15.16 is a standard in which the requirements of WBAN are adjusted for short

range communication with security, low power and reliability on Physical (PHY) and

Medium Access Control (MAC) layers.

2.3 OPTICAL COMMUNICATION

Information can be sent via wired systems or wireless systems. In wireless systems the

transfer of information can be through visible optical, invisible infra-red, ultra-violet or

Radio Frequency. When the information passes through air or vacuum or space

wirelessly through optical carriers such as visible optical radiation also termed as Visible

Light Communication (VLC), invisible infra-red (IR) or ultra-violet (UV) then this is

referred to as Optical Wireless Communication.[47] Discusses that depending upon the

range, Optical wireless communication (OWC) can be categorized in the following five

categories:

22

i. Ultra-Short range: Mostly used for chip to chip communication.

ii. Short range: Used in under water, WPAN and WBAN applications.

iii. Medium range: Its typical examples are indoor infra-red, Visible Light

communication for WLAN, vehicle to vehicle or to infrastructure

communications.

iv. Long range: This communication is between buildings and is also termed as

Free Space Communication (FSO).

v. Ultra-Long range: This type of communication occurs between satellites and

to establish links for deep space.

For short-range indoor wireless communications, Radio frequency as well as Infra-

red both have been used frequently and reported in literature. But due to a number of

reasons preference is given to OWC in specific cases from which to name a few is its

low cost for high bandwidth, is not much effected by electromagnetic interference

(EMI), no licensing required for the spectrum, the components are cheap, having

small form factor, light in weight, and power consumption is very low. Since the

focus of this research is for short-range optical wireless communication systems and

as Infra-red supersedes OW communication systems for short-range applications

hence Infra-red signaling scheme is investigated here for the intended WBAN.

23

2.3.1 Characteristics of Optical Communications

This section discusses some of the characteristics of OWC that are different from

their counterpart i.e. radio which make it an attractive choice to use OWC for this

research. The OW channel has huge bandwidth typically in the range of THz and that

is not regulated. As the optical signals have higher frequency they are more

directional if compared with RF signals which are Omni directional which does not

require specific directive antennas. Additionally, optical signals do not have the

capability to penetrate solid objects only possible if they become transparent to

radiation frequency; whereas RF signals when operated at lower frequencies have the

capability to traverse through solid objects like walls. Dark objects absorb optical

signals; light-colored objects diffusely reflect them where as shiny surfaces reflect

them directionally. IR signals can pass through glass, but not capable to penetrate

opaque structures such as walls and ceilings which gives the concept of frequency

reuse. As the signal is confined within one room so it avoids interference from nearby

room using same optical carrier frequency similar characteristics as of visible light so

this feature can be used to provide privacy in IR based WBANs. A comparison

between RF and IR is given in Table 2.1.

24

Table 2.1 Comparison between RF and IR

Besides the distinct characteristics, RF and optical signals also have some common

properties like various surfaces which including mirror, buildings, walls and water

have the capability to bounce them off. Both type of signals travel a distance and get

weakened but they can be recovered by the receiver. The amount of recovered signal

depends upon the medium the signal propagation, transmitted signal strength and the

receiver’s sensitivity.

Theoretically, the transmission distance is a function of source output power and

receiver’s sensitivity, hence a transceiver should be designed in order to operate at a

suitable power lever with high receiver gain to obtain desirable link distance but

practically IrDA 1.0 and 1.1 compliant devices have the distance limitation up to 1.0

meter (~3.3 feet) a data rate of 115.2 Kb/s with nearly error free transmission.

Directional IR LEDs can be used to enhance the distance to 30 to 40 feet.

25

Because of the small wavelengths of infra-red in comparison to the detector size, IR

systems are free from the fading effects as opposed to their counterpart RF systems.

The safety from fading and stability in position (i.e. slow movement and static nature

of objects) of the indoor environment result in very low variations in the

characteristics of IR channel for substantial periods of time. Although in IR systems

multipath fading is alleviated but this multipath propagation causes dispersion and

hence resulting in inter-symbol interference in high-speed systems.

[5-12, 27] discusses the features, modulation schemes, comparison with RF, selection

of source as transmitter and detectors as receivers and gave us the reasons supporting

the use of IR in WBANs. The optical wireless signaling offers unique advantages as

mentioned earlier. However, in contrast to the RF system, OW links poses some

disadvantages as well [48]. These problems and their possible solutions are depicted

in Figure 2.6.

Fig. 2.6 Problems in IR links and their proposed solutions

26

With other parameters one of the design considerations for a WBAN is the right choice of

Modulation/ Encoding scheme. Various Modulation schemes are discussed in literature to

ensure the reliability and design of power efficient WBAN [48]. In [12] it is stated that

the intensity modulation direct detection (IM/DD) is the most suitable modulation

scheme for infra-red links. In this modulation, information signal modulates the

instantaneous power of the carrier. [49] Discusses the OW systems usually use three

elementary modulation schemes which are PPM, OOK and SCM. It also discusses

several Spread-spectrum modulation techniques to cope with the issues in OW systems.

[12] compares the results of using OOK with NRZ pulses, OOK with RZ pulses of

normalized width δ(RZ- δ) and pulse position modulation with L pulses (L-PPM) [50]

demonstrates the usage of Gaussian frequency shift keying (GFSK) for the development

of Prototype BAN System with Bluetooth. In [51] WBAN performance is evaluated

through BER and SNR for different BPSK carrier frequencies. [52] analyzes and

compares UWB system using PAM, PWM and PPM.

2.4 SUMMARY

From the survey and literature review it is expected that, the developed techniques

- will advance the vital sign sensors and

- Enable more flexible and highly integrated Tx and Rx architectures.

Currently, majority of the work on WBANs rely on RF and Microwave technologies, and

little is done to investigate the optical signaling schemes despite numerous advantages of

IR over RF. It is aimed to tap into this opportunity!

27

It is also aimed to consider the impacts of

- different transceiver array geometries,

- modulation techniques,

- error-correcting codes, and artificial intelligence techniques

on the performance of the Optical communication systems specifically tailored for

WBAN applications.

The discussion in this chapter gives a general overview about the WBAN. It briefly

discusses the existing technologies used and available for WBAN. It also points some key

features of optical communication which served as motivation to choose infrared

signaling for design of WBAN prototype in this research. The research challenges,

objectives, proposed methodology and summary of major contributions for this research

are also conversed in this chapter.

28

CHAPTER 3

PROTOCOL DESIGN & ALGORITHM

In WBANs equal emphasis should be made on the security as well as system

performance, therefore, it is a challenging task to integrate a high-level security in such

resource-constrained networks. Several prototype implementations of WBANs that deal

with QoS and energy efficiency are reported in the literature, however, less research is

found on the aspects of data security and privacy; also the presented solutions are not

much mature [53]. The pros and cons of the existing security mechanisms are discussed

in Chapter 2.

One of the main concerns in WBANs is the secure transmission, without overloading the

energy requirements. In this research, a new energy efficient protocol is presented with

the following features:

- Improved inherent security

- Interference rejection

- Patient/ node identification

The energy consumption is low as there is no extra circuitry required for encryption.

Also, the nodes can go into the sleep mode in the slots while not transmitting or

receiving. The protocol implementation is experimentally demonstrated using low cost IR

transceiver & Arduino Microcontroller. Experimental results reveal the successful

29

transmission & reception of measured parameters over short ranges with sufficient

accuracy. Furthermore, a Matlab based mobile application is developed which helps to

set up a database in distributed manner and subsequently allow the user to monitor,

visualize and share the measured readings remotely.

This chapter discusses the utilization of IR transceivers to design a new protocol for

energy efficient and secure data transmission in WBANs.

3.1 PROTOCOL SPECIFICATION

A simple but efficient protocol is developed from the perspective of security, and patient/

sensor identification. It also incorporates a method to reject interference from other IR

sources like TV, AC remote controls and false data intruders.

Every data sample acquired from the sensor undergoes the packet formation according to

the packet layout developed; hence every reading from the sensors is converted into a 4

byte packet as shown in Figure 3.1.

Fig. 3.1 Packet Format and Specifications

30

Three types of bits are utilized in the packet: unused bits (1 bit), supervisory bits (21 bits)

and the data bits (10 bits). The first byte called IDTAG uses 8 supervisory bits and is

used for the patient identification. Every person or patient is assigned a unique ID from 1

to 255. It is ensured that neither IDTAG nor SUM exceeds limit of 255 in order to

accommodate it in one byte size. The microcontroller is programmed in a manner that it

generates a unique IDTAG for every person/ patient. For instance the user enters the ID =

123, then the required IDTAG is calculated using the formula developed in Eq 3.1.

IDTAG = [FRACTIONAL PART (SQRT (ID)) x 100] + SUM (3.1)

Here, SUM is the fourth byte of frame and its value is calculated by adding the ID

numbers (in our case SUM = 1+2+3 = 06). This unique IDTAG serve dual purpose.

Firstly, it provides inherent encryption for data transmission; secondly it also rejects the

interference caused by other ambient sources.

The second byte contains 1 unused bit, 5 supervisory bits and two data bits as shown in

Figure 3.1. The specification for Byte 2 is summarized in Table 3.1. There are 10 data

bits divided in byte 2 and byte 3 of the frame. Third byte uses the 8 data bits in

conjunction with the 2 least significant bits of byte 2 to store the data from the sensors.

31

Table 3.1 Specifications for S, I, D and Sensor Information

# S I D a B Sensor selected Information

1 0 0 1 0 0 Airflow Data samples

2 0 0 1 0 1 Airflow No of breadth

3 0 1 0 0 0 ECG Data samples

4 0 1 1 0 0 BP Diastolic Pressure

5 0 1 1 0 1 BP Systolic Pressure

6 1 0 0 0 0 Pulse Oximeter SPO2

7 1 0 0 0 1 Pulse Oximeter Pulse Rate

8 1 0 1 0 0 GSR Skin resistance

9 1 0 1 0 1 GSR Skin conductance

10 1 1 0 0 0 Temperature Data sample

The proposed packet length comprises only 4 bytes while majority of the proposed

protocols in the literature are not less than 16 bytes [29-32]. Out of 4 bytes from which it

utilizes 21 bits for encryption and 10 bits for data whereas 1 bit is unused. The ROM used

for the complete program i.e., authentication, acquisition, encryption and transmission is

just of 18964 byes (18.5KB out of 32KB available, 58% usage of the available resource)

whereas the RAM utilization is 1369 bytes. A light weight security protocol is developed

in a resource constrained environment offering least possible overhead (that is fast in

computation and stored in less amount of memory offering least overhead in both

32

perspectives) by using symmetric keys. The transmission of the packet takes place using

Sony protocol [54].

3.2 EXPERIMENTAL SETUP & METHODOLOGY

Figure 3.2 shows the conceptual block diagram of the proposed system. The experimental

design and implementation of the system is presented in [55]. The sensing node includes

temperature, position, Galvanic skin response, ECG, respiration, blood pressure and pulse

oximeter sensors [56]. The Arduino Uno Board having Atmega328 Microcontroller with

the LED drive circuitry is used as a controlling node and for transmitting IR packets,

whereas Arduino Mega2560 with Atmega AVR microcontroller is used at the receiving

side with IR receiver interfaced with it as shown in Figure 3.3. All the experiments are

performed in a well illuminated room with distance up to 3 to 4 feet between transmitter

and receiver.

Fig. 3.2 Conceptual Diagram

33

Fig. 3.3 Circuits for simple IR Transmitter and Receiver

3.2.1 Patient authentication & sensor identification

Initially the controlling node is kept in a locked state to avoid any unauthorized access.

The controlling node will only be unlocked when valid ID and password issued to the

user is entered. Next, the user is asked to select the desired sensor to collect data from.

According to the sensor selection Sensor Node ID is assigned along with the unique data

code representing start/ or joining of the node which will make up the complete packet

for transmission after concatenation of the ID TAG, SUM and the data bytes.

34

Fig. 3.4 System Flowchart

3.2.2 Transmission & Reception with interference rejection

The transmission initiates with a start packet in which all the 10 data bits are one and it

ends with an end packet where all data bits are zero. A simple IR transmitter is designed

by connecting an LED of 940 nm wavelength through resistor on Arduino. The e-Health

sensor platform library is modified and the proposed algorithms are developed on it as it

does not directly support IR transmission. For this we have used IR remote library which

35

basically supports the transmission of the remote control codes. We have sent the

developed packets using Sony protocol with frequency of 40 kHz.

A simple IR receiver is designed by connecting TV Remote IR receiver IC with Arduino

Mega 2560 microcontroller. The receiver is placed in close proximity of 3 to 4 feet of the

transmitter. The incoming packets are received by the IR receiver and unpacked by the

microcontroller. If they are sent from the authentic source then they must follow the

formula as described in Eq 3.1 for IDTAG otherwise should be rejected and treated as

unauthorized. Similarly if any remote control is directed towards the receiver, it can

reject those signals as well, as shown in Figure 3.5 (a) and (b). The processing results are

shown in Figure 3.5 (c).

(a) (b)

Fig. 3.5 Interference creation with various Remote controls (a) TV/ DVD Remote (b)

AC remote

36

Fig. 3.5 (c) Snapshot of Arduino IDE while receiving all signals i.e. ID1, ID2 and

remote control

3.2.3 Energy efficiency

After the data has been successfully transmitted and received, the controlling node enters

in the sleep mode to save energy during idle periods. The controlling node is scheduled to

wake up every hour or it can be alerted whenever an interrupt is generated from the wake

up circuitry in case of an emergency or upon user’s requirement. Furthermore, the

IDTAGS are soft generated and, therefore no additional circuitry is required for either

encryption or interference rejection. Thus rendering the system energy efficient.

37

3.2.4 Node Joining/ Un-joining

The node enters into the network after authentication process as described above. After

the transmission of start data packet, further packets are formed using actual data from

the sensor which is placed within the packet as described in Table 3.1. When the user

wants to remove the node or when the time for acquisition reaches the preset time limit

an end packet is generated to indicate end of data or removal of the node.

3.3 SUMMARY

This chapter highlighted the development of a novel protocol for this research having key

features of node and patient identification with interference rejection from other IR

sources. The protocol specifications and its working algorithm along with simple IR

Transceiver designs are discussed in this chapter. The protocol is specially made light in

computation and processing to incur least possible overhead while addressing the security

and privacy requirements of WBANs.

38

CHAPTER 4

MOBILE APP DEVELOPMENT

In order to provide the user interface and easy access to the patient/ user an android app is

developed for this research project. Initially the results were tested by using the Matlab

mobile and it gave satisfactory results but to make it more user friendly, a standalone

Android App for acquiring and visualizing vital signs of a person in the form of data and

charts is developed as part of this research project. This chapter discusses the main

development aspects and features of both the mobile Apps.

4.1 MATLAB DATABASE DEVELOPMENT

A database is created through Matlab using simple Excel files by exporting data from the

Arduino Microcontroller. The database creation flowchart is shown in Figure 4.1. The

microcontroller having IR receiver is programmed in such a way that it is capable to

differentiate between various patients with assigned IDs and can store their data

separately in Matlab database. From the data that is coming from the serial port of

Receiving Arduino to Matlab the ID of patient is extracted, through which the record of

the patient is located in the Excel database. Every patient has been assigned a different

sheet name in Excel database file for writing his vital signs information in his respective

sheet. The Matlab program after locating the filename and extracting every individual

39

sensor information, writes it in different columns for a particular patient. The snapshot of

the database with sensors data received by Matlab is shown in Figure 4.2.

Fig. 4.1 Flowchart for database creation

40

Fig. 4.2 Snapshot showing various Fields of created database

4.2 MATLAB MOBILE APPLICATION

A Matlab mobile application [57] is used due to its simplicity to acquire, visualize, store

and share the data from the sensors. It is specially designed by Math Works for smart

phones so that they can be connected to the running sessions on their Cloud or destined

computer. As Matlab mobile does not support the GUI execution, a simple Matlab script

file is developed to be run from Matlab Mobile. Figure 4.3 shows the flowchart for the

algorithm adopted in this script file.

41

Fig. 4.3 Matlab Mobile App Script Algorithm

In order to access the vital signs data of a person or to know the health condition of a

person one must connect to the computer where this information is saved through Matlab

Mobile. In order to access the information one must connect to that computer by giving

first IP address or DNS name, computer name, connector password and port number etc.

through which some are optional settings while others are mandatory. The user knows the

script file name which he or she writes on the Matlab mobile command prompt, once the

Mobile app is connected to the computer. The m script file is simply the code which is

written to load the respective excel file in which the vital signs or sensors data

information is saved for a particular user/ person. After loading the sensor’s data the

42

values are simply displayed on the command prompt with the help of display commands

written in the script file whereas the data from the sensors such as ECG and Airflow are

plotted using plot commands. It is also programmed to show the pictorial representation

of the position detected by the position sensor, five positions detection is programmed for

this purpose. Once the graphs and pictures are brought up in the main window they can

be either saved in pictures/ gallery or easily shared from within the Matlab Mobile App

just like any other applications sharing options. The snapshots of the Matlab Mobile App

running the script file are shown in Figure 4.4.

(a) (b)

43

(c)

(d)

44

(e)

(f)

45

(g)

Fig. 4.4 Script execution output on Matlab Mobile App: (a) Matlab Mobile App

Settings (b) Summary generated on command prompt after script execution (c)

ECG plot (d) Airflow chart (e) Position State (f) images to be saved in pictures (g)

Options to share images from Matlab Mobile

4.3 ARDUINO & ANDROID DATABASE WITH ANDROID APP ACCESS

Another method that is used in this research for accessing the vital signs sensors data

through Mobile is with the help of Android App which is more user friendly, easy and is

independent of the Matlab platform.

46

4.3.1 SD Card Database creation and its Access

After authentication and the sensor’s data extraction from the Arduino program according

to the packet formation, sensor data values are saved now in SD card with every patient’s

separate text file having starting and ending packets to distinguish each sensor data set’s

start and its end. So the SD card will be recording multiple sets of the tests for the same

patient or different patients at different instances.

The Arduino program besides writing the data on SD card also checks for any message at

UDP port 5555 if there is any message then check either it is of the form “fetch:id*#--3*”

or not, if yes then extract the ID from it, note IP address of the sender, read particular

id.txt file from the SD card and the file contents to the same sender’s IP at same port

5555 and if there is no such message on UDP port then skip this step and continue the

previous routine.

4.3.2 B4A Anywhere software

An android app is developed using B4A Anywhere software (Rapid Application

Development) RAD tools. B4X programming language is an enhanced form of VB plus it

gives the facility thorough B4A-Bridge to directly connect your physical device right

from the IDE and observe the effects instantly while developing over the local network

either by using Wi-Fi or Bluetooth so it was found easy to develop the app for this

research using B4A. The features of this software are shown in Figure 4.5 [58].

47

Fig. 4.5 RAD tools by Anywhere Software

4.3.3 Developed Android App

The Android app is capable to perform:

i. Online tests i.e. fetch most recent values.

ii. Fetch previous values saved in the SD card attached with Arduino

Microcontroller.

iii. Display charts/ Graphs of ECG & Airflow, also pictorial representation of

person’s position.

iv. Save and share from within the developed Android App.

Another database is created in the mobile using SQLite. When the user is connected to

the receiver he/ she can get the recent test values. Once the new values are acquired they

are saved in the Mobile’s memory using SQLite which can be seen later in offline mode

48

as well, until the new values are acquired as they will be overwritten in order to display

new graphs and charts in accordance with the fresh data. This is done in order to avoid

any overload on mobile’s memory. The app supports saving and sharing of the data and

charts so it is up to the user’s decision which test reading he/ she wishes to save or share

for later use within mobile. Figure 4.6 illustrates the snapshots of the developed Android

App.

(a) (b) (c)

49

(d) (e) (f)

(g) (h) (i)

50

(j)

(k)

(l)

51

(m) (n)

Fig. 4.6 Android App Screen Shots (a) Home Screen (b) About Screen (c) Start

Screen (d) Fetch Information Screen (e) Results of Fetch Information Screen (f)

Pulse Rate Screen (g) Blood Pressure Screen (h) Temperature Screen (i) GSR

screen (j) Airflow Graph (k) ECG graph (l) Position State Screen (m) Share Screen

(n) Result of Sharing data on WhatsApp Screen

4.4 SUMMARY

This chapter discusses the development of the mobile apps to visualize the physiological

data in a user friendly manner. This chapter presents the app development and their

results in numerical as well as graphical screen shots form. Two mobile app platforms i.e.

Matlab Mobile and Basic4Android are used in this research and discussed in this chapter.

52

CHAPTER 5

PROTOTYPE DESIGN

One of the major contributions for this research work is the prototype design that could

be used as a WBAN. As WBAN is a network consisting of sensors capable of measuring

and monitoring vital signs, the main objectives were to select appropriate sensors, their

interfacing in WBAN & data acquisition through them and the design of optical

transceiver working within sub meter range of human body. The proposed prototype can

be better understood form Figure 5.1.

Fig. 5.1 Proposed Prototype WBAN

53

5.1 SELECTION OF SENSORS

The foremost technical challenge is to design a physiological sensor or device [20]. As

the primary focus in this research was optical signaling from the sensor nodes so a

number of sensor nodes were investigated which can easily be connected and interfaced

in this prototype. After surveying different sensors available in the market, e-health

sensor platform by Cooking Hacks Libellium (Spain) was chosen to be the source of

Vital signs sensor data [56].

5.1.1 Features of e-health sensor platform

The e-health sensor platform is a complete kit which comes along with 9 sensors (V1.0)

and 10 sensors in (V2.0) including EMG sensor. It consists of a biometric shield

compatible with Arduino and Raspberry Pi. The shield contains all the necessary drive

circuitry for the sensors and connectors. The e-health shield and the sensors are shown in

Figure 5.2 [56].

54

Fig. 5.2 e-health sensor complete kit [56]

In this research following sensors are used:

i. Position sensor or Accelerometer

ii. Pulse Oximeter

iii. Temperature sensor

iv. GSR sensor

v. ECG sensors

vi. Blood Pressure sensor

vii. Air Flow sensor

55

Fig. 5.3 Cooking Hacks e-health sensor platform by Libellium (a) Sensor Shield (b)

Sensor Shield mounted on Arduino UNO

5.1.2 Data Acquisition

In order to acquire data, the sensors are plugged in with the shield and connected with the

Arduino UNO microcontroller which now serves as the controlling node for this

prototype WBAN shown in Figure 5.3 (a & b). The e-health shield comes with the e-

health library and programs to acquire the data which are customized and the data packets

are appended with security and patient/ node identification information according to the

developed protocol as described in chapter 3.

E-health sensor platform provides connectivity through the following 5 wireless

technologies:

i. 3G

ii. Bluetooth

56

iii. GPRS

iv. ZigBee/ 802.15.4 and

v. Wi-Fi

All of these require extra shield/ module to be mounted on the shield which is not cost

effective plus it was aimed to provide low power, low cost solution for wireless

transmission. In order to transmit data with low complexity in context of cost, power and

computational overhead, an IR transceiver is designed with the inexpensive and easily

available components.

5.2 SELECTION OF IR SOURCE

There are two main sources for IR transmission i.e. LED and Laser Diode. LED being the

cheaper, simpler, low in output power, suitable for low data rate and short ranges as

compared to the laser diode is chosen here for a simple IR transmitter design.

5.2.1 LED Drive circuitries

Various LED drive circuits were tested to cover longer range as shown in Figure 5.4.

From the experiments it was found that the transistor drive circuitry gives better coverage

amongst the components discussed here. The detection efficiency also depends upon the

receiver or the detector used for the IR transceiver.

57

Fig. 5.4 LED Drive Circuits

Hence a simple IR Transmitter is designed just by connecting IR LED with transistor

drive to pin 3 of the Arduino that is responsible for IR transmission.

5.3 IR RECEIVERS/ DETECTORS

There are various photodetectors available in the market. Following four detectors are

used which are easily available in the market/ Lab at very low price for testing and

analyzing the performance for the development of proposed IR based WBAN.

i. Photodiode

ii. phototransistor

iii. TV remote IR receiver

iv. Thor Lab PIN diode

58

Fig. 5.5 Photodetectors

5.3.1 Testing Photodiode

The photodiode was tested first in an open loop by giving an IR signal from a remote

control as our vital signs data has to be a modulated signal using IR Remote control

modulation schemes. It was observed that the voltage across the simple diode is only of

the order of 300mv (Figure 5.6) which specifies the need for biasing circuitry. So a

resistive biasing circuitry was employed but it introduced noise at the receiver.

Photodiode response in both cases is shown in Figure 5.7 when a square wave signal is

fed to the LED from the Function generator and when a modulated signal from Arduino

pin 3 is given to the LED.

59

Fig. 5.6 Photo Diode Response in Open Circuit Fig. 5.7 Photo Diode response with

ResistorBiasing when a signal

from Remote control is given

5.3.2 Testing Photo Transistor for Transceiver Design 1

In order to improve the response of the photodetector in terms of noise and signal level, a

photo transistor with amplification stage added is used as shown in Figure 5.8. Though

this configuration improves the received signal, but it is still limited to a transmission

distance upto few centimeters. Beyond 5 cm the signal degrades significantly.

60

Fig. 5.8 Photo Transistor Receiver Design

So IR Transevier design 1 is designed with the above mentioned components and drives

that yields better results i.e. LED with transistor drive and a phototransistor with OPAMP

amplification stage. The Block diagram and the prototype is shown in Figure 5.9 (a) and

5.9 (b).

61

Fig. 5.9 (a) Block Diagram of IR Transceiver Design 1 (b) Prototype of IR

Transceiver Design 1

Another IR transiever prototype is designed using simple LED drive transmitter and an

IR remote control receiver IC both connected with the separate arduinos.

5.3.3 IR Remote Control Receiver IC and Working of IR Transceiver design 2

The transmitter of the IR Trasnsceiver design 2 sends the remote control codes but having

vital signs sensors data encoded as remote control codes. This working is explained in

Figure 5.10 where an arduino Uno board sends the data from arduino pin 3 as modulated

IR packets.

(a) (b)

62

Fig. 5.10 Block Diagram of IR Transceiver Design 2

These packets can be encoded in any of the remote control protocol and modulation

scheme supported by Arduino IRremote Library. The new protocol developed in this

research was described in chapter 3. Various IR Remote Control Protocols which are

present are listed in Table 5.1 where as the protocols supported by Arduino IRremote

Library are listed in Table 5.2. In this research Sony SIRC Protocol and Phillips-RC5

Protocol are tested in experiments.

63

Table 5.1 Various IR Remote Control Protocols

Table 5.2 Protocols supported by Arduino IR Remote Library

S. No. Protocol S. No. Protocol

1 NEC 6 DISH

2 Sony 7 Panasonic

3 Sharp 8 JVC

4 RC5 9 Sanyo

5 RC6 10 Mitsubishi

The Arduino IR Remote library provides the following features:

Encodes the data in accordance with desired protocol specification.

Supports development of user defined protocols (Raw data).

Recognizes the protocol type at receiving end.

Decodes the received data according to protocol specifications.

S. No. IR

Protocol

Modulation/

Encoding

Scheme

No of

D+C bits

Msg

Duration(ms)

Carrier

Frequeny

1 ITT Pulse

Distance

14 1.7-2.7ms -

2 JVC Pulse

Distance

16 43.6 (max) 38KHz

3 Nokia

NRC17

Bi Phase 17 20 38KHz

4 NEC Pulse

Distance

16 49.5 (max) 38KHz

5 Sharp Pulse

Distance

13 26 (typ) 38KHz

6 Sony

SIRC

Pulse width 12,15,20 27(max) 40KHz

7 Phillips

RC-5

Bi Phase

(Manchester)

11 25 36KHz

8 Phillips

RC-6

Bi Phase

(Manchester)

variable 36KHz

9 Phillips

RCMM

Pulse position 12,24 3.5-6.5 36KHz

10 Phillips

RECS-80

Pulse

Distance

12 38(max) 38KHz

11 X-Sat Pulse

Distance

16 48(max) 38KHz

64

Supports the protocols mentioned in Table 5.2.

The Sony SIRC Protocol and Phillips-RC5 Protocol formats are shown in Figure 5.11(a)

and (b).

Fig. 5.11 (a) Sony SIRC Protocol Fig. 5.11 (b) Phillips-RC5 Protocol

Once the encoded data is transmitted, it is received by the IR remote control IC. As the

IC contains built in Amplifier, Band pass filter, Demodulator and Comparator, things

become really easiy with this small IC occupying very less space and circuitry with very

low power consumption. The raw data that appears on LED at transmitting side and at pin

1 of the IR remote control receiver IC is shown in Figure 5.11 (a) and 5.11 (b). The

decoding part is taken care by Arduino IR Remote library. So with simple harware design

and using the library features we acquire secure and reliable IR communication between

transmitter and receiver for our prototype WBAN.

65

5.4 PERFORMANCE ANALYSIS

Two parameters are selected to analyze the performance of the IR Transciever designs 1

& 2, which are Distance and Noise. Experimental setup for observing the effect of

varying these parameters through eye diagram is described in the next section.

The measurements can be read directly from the oscilloscope where as the signal to noise

ratio and bit error rate (BER) can be calculated by using Eq 5.1 to Eq 5.4.

( )

( ) (5.1)

( ) ( ) (5.2)

(√ ) (5.3)

(

√ ) (5.4)

We have taken readings and calculated the above mentioned parameters for both

Transeiver designs 1 & 2.

5.5 EXPERIMENTAL SETUP

An eye diagram is generated on an oscilloscope using the setup of Figure 5.12 . The data

signal to be transmitted is generated from either the function generator or from arduino

pin 3 which is applied to the LED drive circuitry and also visualized at oscilloscope’s

channel 1. When taking the measurements for noise effect, a noise signal is added with

this input signal from Agilent 33250A Function generator/ Arbitrary Waveform

66

generator, whereas the received signal from the detector is visualised at channel 2 of the

oscilloscope. Here we have used the data signal itself as a trigger signal for making

overlapping eye patterns and have set the persistance value to 1 sec in order to get clear

measurement results from the eye diagrams [59-64].

Fig. 5.12 Test Set-up for Noise Effect Measurements

The noise signal generated from the Function generator is a white noise. There are four

options available in the Function generator to vary noise parameters as shown in Figure

5.13. Experiments show significant effect in reception when DC Noise offset is varied

hence results for varying offset value are discussed in chapter 6.

67

Fig. 5.13 Noise Signal generation from Agilent 33250A Function generator/

Arbitrary Waveform generator and its effect in transmission and reception

5.6 ThorLAB PIN DIODE

Due to the limitations incurred by the photodiode and phototransistor in terms of distance

and sensitivity to noise, other options like TV remote control receiver IC and ThorLAB

PIN diode were also tested in this research for the suitability of designing WBAN

Prototype IR receiver. The ThorLAB DET100A is a large area Silicon photodetecter with

a wavelength range of 400 to 1100nm and Peak Wavelength at 970nm which is close to

the IR Transmitter LED used i.e. 940nm. These diodes are ideal for measuring both

pulsed and CW light sources. The output is taken from the BNC connector which is the

direct photocurrent out of the photodiode anode and is the function of incident light

power and wavelength. The output from the PIN diode is coming in range of 300mV so

an OPAMP amlifier is connected to its BNC output to amplify the signal upto 2V. This

PIN Diode is used in conjuction with the EV/MCM31 Digital Modulation Trainer which

68

is used here to generate an encoded and modulated signal which will serve as Tx signal

and through which IR LED is driven. The ThorLAB receiver is palced at a distance of

upto 3 feet from the IR transmitter. The ThorLAB Receiver’s output after getting

amplified is now fed to another EV/MCM31 trainer to ensure isolation between

transmitting trainer and receiving trainer plus to vary the distance between transmitter

and receiver easily.

The MCM31/EV trainer board (Figure 5.14) is used here to study the effects of digital

modulation schemes on the reception provided by the trainer along with the test points

and connectivity [65], through which it becomes easy and handy to observe the impacts

of varying various parameters like distance between the transmitter and receiver, angular

displacement from LOS to few degrees from receiver, effects of increasing light intensity

in the room by making the number of lights ON and OFF. Different encoding schemes

(BIT, Dibit, TRIBIT, Manchester) provided by the trainer were also tested to observe the

effect on reception. Various experiments are performed and the performance of the link

is evaluated with the help of eye diagrams and constellation diagrams plotted on

TEKTRONIX TDS2012 Oscilloscope discussed in chapter 6.

69

Fig. 5.14 EV/MCM31 Digital Modulation Trainer

The modulation scheme, encoding scheme, demodulator and decoder are selected through

the jumpers.

Following connections and settings are carried out in order to perform all the experiments

for this Transeiver set up.

- TP20 is used as the TX signal for driving IR LED from trainer 1.

- Amplified output from ThorLAB PIN detector connected to TP20 of Trainer 2 at

distance upto 5-7 ft.

- TP24 which is the low pass filtered output and serves as the carrier removed

signal is used to plot the eye diagrams of the received signal.

- TP9 (Trainer 2) RX DATA is used to compare the received data against the

transmitted data at TP4 (Trainer1).

70

- TP3 is used to observe the clock frequency/ data seed for the generated data

according to selected encoding scheme and modulation through jumpers which

are fixed or by default setting of the trainer.

- The data rates supported by the trainer are listed in Table 5.3.

Table 5.3 MCM31/EV Encoding schemes and their respective data rates

S.No Encoding Scheme Data speed (bits/s)

1 Manchester 300

2 Bit 600

3 DiBit 1.2K

4 Tribit 1.8K

- The bit speed is changed to keep the same symbol speed (i.e. 600 Baud) in every

encoding/ modulation.

- TP27(X) and TP28(Y) of trainer 2 are used to plot constellation diagrams on

Oscilloscope in XY Mode.

The transeiver designed using the two trainers is illustrated in Figure 5.15.

71

Figu

re 5

.15

IR T

ran

seiv

er

usi

ng

Th

orL

AB

PIN

an

d M

CM

31

/EV

Tra

iner

72

The experimentul results with these connections and settings according to the variations

in parameters chosen are discussed in Chapter 6.

5.7 SUMMARY

The prototype development for the IR based WBAN has been covered in this chapter. It

highlights the interfacing of sensors, their connectivity in WBAN, the issues encountered

in choosing transmitter and detectors for the prototype development and their possible

solutions. This chapter also explains the experimental set up and describes each

component, board and equipment specifications, usage and limitations in the

experimental work for this research.

73

CHAPTER 6

RESULTS & DISCUSSION

The performance of Transceiver designs presented in chapter 5 is evaluated in this

chapter by using eye diagrams. The first two designs are tested for the two parameters i.e.

Distance and Noise whereas Transceiver design using ThorLab PIN detector is tested for

varying distance, ambient light, angle and modulation schemes.

6.1 TRANSCEIVER DESIGN 1 READINGS WITH INCREASE IN DISTANCE

Figure 6.1 (a-c) shows the effect of varying link distance when a simple square wave was

transmitted through IR transceiver design 1. The received waveforms and eye diagram

clearly shows the degradation in the signal when the distance is increased. The

experimental readings found from oscilloscope and the SNR calculated using Eq 5.1 and

Eq 5.2 are listed in Table 6.1. The degradation of SNR with increase in distance is also

visualized by graph in Figure 6.1 (d) whereas the BER is calculated using Eq 5.3 & Eq

5.4 and plotted in Matlab in Figure 6.1 (e).

74

Fig. 6.1 (a) Fig. 6.1 (b)

Fig. 6.1 (c)

Fig. 6.1 Photo Transistor Response- (a) Tx-Rx 3cm (b) Tx-Rx 6 cm (c) Tx-Rx 9cm

75

Table 6.1 Experimental Readings for Transceiver Design 1 with Distance

S.No. Distance

(cm)

Noise

level

(mV)

Signal

level

(V)

SNR SNR

(dB)

Jitter

(µs)

Vertical

Eye

Opening

(V)

Horizontal

Eye

Opening

(µs)

Rise

Time

(µs)

Fall

Time

(µs)

1 3cm 560 9.12 16.28 24.23 14 7.76 47 17.6 16.45

2 3cm 560 9.6 17.1 24.6 16 8.4 50 17.1 17.60

3 6cm 280 2.52 9 19.08 13 2.2 56 20 21.03

4 6cm 320 2.52 7.8 17.84 11 2.1 58 22 24

5 6cm 160 1.42 8.87 18.9 22 1.16 74 20.2 21.2

6 9cm 80 376m 4.7 13.44 15 192m 96 24.4 26.60

7 9cm 160 608m 3.8 11.59 18 336m 97 36.3 38.2

8 9cm 140 460 3.2 10.1 20 260m 42 21.5 25

Fig. 6.1 (d) Effect of increasing Distance on SNR (e) Matlab Simulation for SNR vs

BER with varying distance for Transeiver Design1

SNR of 16.28 achieved with 3 cm Distance

(e) (d)

76

6.2 TRANSCEIVER DESIGN 1 NOISE EFFECT READINGS

The Transceiver is tested with the addition of white noise as described in the

experimental setup. Now the distance is kept constant where the best SNR was achieved

i.e. 3 cm so that effect of noise addition can be observed. The snapshots of the

oscilloscope screen in Figure 6.2 clearly shows that not only the received signal level

reduces when the Noise DC offset is increased from 0V to 2V but also it becomes

drastically noisy and the eye opening gets really diminished. The experimental

measurements taken are summarized in Table 6.2.

Fig. 6.2 (a) Results with adding Noise offset from 0V to 2V

77

Table 6.2 Experimental Readings for Transceiver Design 1 with Noise effect

S.No. Noise

offset

V

DC

Noise

level(mV)

Signal

level(V)

SNR SNR

(dB)

Vertical

Eye

Opening(V)

Horiz-

ontal

Eye

Opening

(µs)

Jitter

(µs)

Rise

Time

(µs)

Fall

Time

(µs)

1 0 640 9.60 15 23.52 8.56 93 14 15.1 16.8

2 1 880 9.2 10.45 20.3 7.92 96 27 15.3 17.8

3 1.2 960 8.56 8.916 19 7.12 68 4.6 16.5 17.2

4 1.3 1.04V 7.76 7.46 17.4 6.24 85 12 18.2 20

5 1.4 800 7.2 9 19.08 5.2 99 10 21.8 29

6 1.4 880 7.04 8.4 18.48 5 102 16 20.7 26

7 1.5 1.04V 7.04 6.7 16.5 4.72 88 24 22.9 78.7

8 1.6 1.12V 6.24 5.57 14.92 3.84 88 13 21.2 22

9 1.6 1.36V 6.24 4.58 13.22 3.4 99 19 20.3 22.2

10 1.7 1.44V 5.28 3.66 11.27 2.9 92 24 18.2 20

11 1.8 960 4.16 4.33 12.73 2.72 97 26 18.8 19.3

12 1.9 960 3.36 3.5 10.88 2.24 99 9 16.3 18.8

13 2 800 1.84 2.3 7.23 960m 92 2.2 18.8 21.4

Best SNR of 15(23.52dB) achieved with 0VDC

Fig. 6.2 (b) Effect of increasing Noise DC

offset on SNR

Fig. 6.2 (c) Matlab Simulation for SNR vs

BER with DC offset Noise Value for

Transeiver Design 1

78

6.3 EXPERIMENTAL RESULTS FOR TRANSCEIVER DESIGN 2

The Transceiver Design 2 as discussed in Figure 5.10 is also tested by varying link

distance as well as DC Noise offset value in a well illuminated room setup as shown in

Figure 6.3. Readings are taken while increasing the distance from 1ft to 4ft and

comparing the data sent versus received data as shown in Figure 6.4 (a) and (b). It is

observed that there are not many errors introduced in the data and the WBAN vital signs

data reach the destination quite reliably. Also the received signal maintains a good SNR

value due to the built in circuitry in the IR Remote Control Receiver IC. The data was

sent using Sony as well as RC5 protocols.

Fig. 6.3 Experimental setup for Transceiver Design 2 (Link distance upto 4 feet)

79

(a) (b)

Fig. 6.4 Experimental Results with Receiver upto 4 feet apart (a) Sony Protocol (b)

RC5 Protocol

6.4 TRANSCEIVER DESIGN 2 NOISE EFFECT READING

The Noise is added in the same way as in Transceiver Design 1. The observations and

readings show that the SNR remains pretty constant with the increase in Noise DC offset

but after a threshold value of DC offset the data starts getting corrupted. This effect is

shown in Figure 6.5 (a-c) for both protocols i.e. RC5 as well as Sony.

Fig. 6.5 (a) Experimental Results for Effect of adding Noise offset (RC5 Protocol)

80

Table 6.3 Experimental Readings with Noise for Transceiver Design 2

Fig. 6.5 (b) Experimental Results for Effect of adding Noise offset (Sony Protocol)

(c) Effect of Distance & Noise on SNR in IR Receiver IC

(b) (c)

81

As the SNR is not much effected by the addition of DC offset noise so calculation based

on SNR will not yeild correct results so we have measured the level of data corruption by

calculating BER through Matlab by importing transmitted sequence versus received

sequence and then comparing bit by bit to calculate number of errors. Thus BER is given

by Eq 6.1.

(6.1 )

The readings taken are illustrated in Table 6 and Figure 6.5 (d).

Table 6.4 Experimental Readings with Noise for BER in Transceiver Design 2

S.No. Noise

offset

No of

samples

No of bits

(no of

Samples*16bits)

No of

bits in

error

Bit error

rate

1 0 VDC 3000 48000 0 0

2 0.5VDC 3000 48000 07 0.000146

3 1VDC 3000 48000 13 0.000271

4 1.3VDC 3000 48000 843 0.0175

5 1.6 VDC 3000 48000 967 0.020146

6 1.7VDC 3099 49584 2183 0.044026

7 1.72VDC 1632 26112 977 0.03741

8 1.73VDC 3026 48416 1803 0.03724

9 1.74VDC 3028 48448 1333 0.027514

10 1.75VDC 3034 48512 1115 0.0222969

11 1.8 VDC 2894 46304 5673 0.122516

12 1.9 VDC 3000 48000 9078 0.189125

82

Fig. 6.5 (d) BER curve with noise offset in Transceiver Design 2

It is observed in Figure 6.5 (d) that when the DC Noise offset is below the threshold

value of 1.3V DC, the BER is within the range of 0 to 1 %. So in order to get successful

reception within tolerable limts the Noise DC offset should be less than 1.3VDC.

Two low cost transceiver designs have been tested for WBAN using optical signaling

schemes with their performance analysis with respect to Distance and Noise. It is

demonstrated through experiments that Transceiver Design 2 is better than Transceiver

Design 1 due to coverage upto 4 feet as well as signal quality which are the requirements

of WBAN. These comparative results are summarized in Figure 6.6.

83

Fig. 6.6 Comparative results for peformance analysis of transceiver design 1 & 2

84

6.5 TRANSCEIVER DESIGN 3

The arrangements and connections of the ThorLAB PIN receiver with the MCM31/EV

Trainers were discussed in chapter 5. In order to evaluate the performance of this

transceiver system discussed in Figure 5.15. The experimental setup was made in the

Research Lab1 IIT Building MUET whose dimensions for this evaluation are illustrated

in Figure 6.7.

Fig. 6.7 Research Lab 1 (IIT building MUET) Experimental setup and lab

dimensions

An IR LED of 940nm wavelength is used for the experiments in conjunction with the

MCM31/EV Trainer to serve as the Transmitter shown as Tx in Figure 6.7 whereas a

Silicon based PIN detector is used with another MCM31/EV Trainer which serves as the

85

receiver also shown as Rx in Figure 6.7. This setup is placed on the desk in the middle of

the lab as the light if falling directly upon the receiver severely deteriorates the reception.

Also the window is covered because even if the sunlight not falling directly upon the

window but it was creating so much interference and noise that it was not possible to

carry out experiments. The room lights were purposely turned ON and OFF to observe

the impact of fluorescent/ ambient lights on the optical wireless communication link.

Table 6.5 and Table 6.6 explains the impact of turning specific light switching (ON/OFF)

upon the PIN Rx received power and light intensity in the Lab (lux). NewPort Digital

power Meter Model 815 was used to calculate the received power from PIN RX due to

lights variation at the above mentioned installation place. Table 6.5 enlists the readings

taken at Research Lab1 IICT MUET for this experimental setup.

Table 6.5 Received Power Readings taken at Research Lab1 IIT building from PIN

RX for change in light due fluorescent bulbs switching.

S. No. No. of lights ON Power received

1 One 0.62mW

2 Two 0.72mW

3 Three 1.44mW

4 Four 1.84mW

The PIN Rx is placed on a stand with rotor and markings in the base to calculate angular

displacement from LOS between Tx and Rx. The distance towards the wall also has

impact upon the readings. If the receiver is rotated clockwise (towards right wall where a

white board is placed and has greater distance from receiver to wall) the angle is less up

86

to which we can get acceptable reception as compared to the anticlockwise rotation of the

dial (towards the left wall which is just 2 feet away from the receiver). This angle also

depends upon the modulation scheme, noise due to the presence of amount of light and

the distance between the Tx and Rx.

In order to have a quantitative measurement of the light present in the lab, an ambient

light sensor (Vendor: TAOS, version: 1, power: 0.75, maximum range: 3000, resolution

1.0) built in the smart phone (Huawei Honor 6) was used along with sensor box for

Android app in these experiments to measure incident light intensity at the point where

the receiver is placed. Table 6.6 demonstrates the variation in lux values due to switching

of lights installed in the Research lab. It was observed that the lux meter showed

maximum value of 499 lux when all the four lights were ON and if the smart phone is

kept directly below the light installed at the ceiling which decreases gradually if the

phone is taken away from the light. The android app showed the reading in the range of

2000 lux when faced towards the window when the window is uncovered and 0 lux when

the smart phone is covered or there is complete darkness. It should be noted that the PIN

Rx is facing towards the LED Tx and not facing up towards the ceiling so less amount of

light is entering the PIN receiver.

Table 6.6 Readings taken while switching the light at Research lab1 IIT Building

MUET by ambient light sensor of Smart Phone

S. No. No. of lights ON Illuminance (Lux) 1 None 0-2

2 One 4-6

3 Two 8-14

4 Three 16-20

5 Four 34-39

87

The Silicon based PIN Rx (ThorLAB DT100A) used in these experiments has the

following specifications enlisted in Table 6.7.

Table 6.7 ThorLAB DET100A Large Area Silicon Detector Electrical Specifications

S. No. Parameter Value

1 Active Area 75.4mm2

2 Wavelength Range (λ) 400 to 1100nm

3 Peak Wavelength (λp) 970nm (typ)

4 Peak Response (typ) 0.65A/W (typ)

5 Power 1.5mW (min@ λp)

6 Output Voltage 0 to 10V

A TEKTRONIX TDS2012 Oscilloscope with 100MHz Bandwidth and 1GSa/s sample

rate is used for eye diagrams and constellation diagrams. Another DSO GDS-1062 of

GW Instek with 20MSa/s sampling and 60MHz bandwidth 4000 samples memory length

is used to record the samples. The MCM31/EV Digital modulation Trainer was used for

these experiments as described in Figure 4.15. The results are discussed here according to

each parameter and its impact on the Infra-red Link.

6.6 TRANSEIVER DESIGN 3 READINGS AND OBSERVATIONS

In order to observe the influence of increasing any parameter, the other parameters are

kept constant. The readings are taken for varying one of the following parameters which

are enlisted in Table 6.8.

i. Link distance

ii. Ambient light

iii. Angle of receiver towards transmitter

iv. Modulation scheme

88

Table 6.8 Transceiver Design 3 Readings with varying one parameter at a time

S. No. Modulation Distance

(ft)

Lights Angle

(degrees)

Signal

(V)

Noise

(V)

SNR

1 ASK 1 No 0 9.12 640m 14.25

2 ASK 2 No 0 5.24 400m 13.1

3 ASK 3 No 0 3.22 600m 5.3

4 FSK 1 No 0 3.4 600m 5.6

5 FSK 2 No 0 3.76 600m 6.2

6 FSK 3 Two 40 3.64 560m 6.5

7 ASK 1 Two 0 9.04 560m 16.1

8 ASK 1 Two 0 9.52 960m 9.91

9 ASK 1 Two 20 8.64 800m 10.8

10 ASK 1 Two 40 8.96 2.24 4

11 ASK 1 Two 60 4 1.6 2.5

12 ASK 3 No 0 3.22 600m 5.3

13 ASK 3 No 20 2.88 280m 10.2

14 ASK 3 No 40 2.56 600m 4.2

15 ASK 3 No 60 1.28 320m 4

16 FSK 3 Two 0 3.60 640m 5.625

17 FSK 3 Two 40 3.64 560m 6.5

18 FSK 3 Two 60 3.84 840m 4.5

19 ASK 3 No 0 3.22 600m 5.3

20 ASK 3 Two 0 2.92 640m 4.5

21 ASK 3 Four 0 6.72 4.24 1.58

22 ASK 1 No 0 9.12 640m 14.25

23 ASK 1 Two 0 9.04 560m 16.1

24 ASK 1 Four 0 9.52 1.2 7.9

25 FSK 7 Two 0 3.24 600m 5.4

26 FSK 7 No 0 3.36 360m 9.33

27 FSK 7 No 40 3.28 400m 8.22

28 FSK 7 No 55 3.32 560m 5.9

29 FSK 6 One 0 3.28 360m 9.11

30 FSK 6 No 0 3.44 440m 7.818

31 2-PSK 6 One 0 1.52 120m 12.66

32 2-PSK 6 No 0 1.52 120m 12.66

33 2-PSK 6 Two 0 1.58 280m 5.64

34 2-PSK 6 No 35 752m 152m 4.9

35 2-PSK 6 No 20 776m 160m 4.85

36 4-PSK 6 No 0 1.08 128m 8.44

37 4-PSK 6 One 0 1 120m 8.33

38 4-PSK 6 Two 0 952m 120m 7.93

89

39 4-PSK 6 Two 0 1.04 272m 3.82

40 4-PSK 6 Two 10 976m 224m 4.35

41 4-PSK 6 Two 10 960m 192m 5

42 4-PSK 6 Two 10 1.09 176m 6.19

43 4-PSK 6 Two 10 1.22 392m 3.16

44 4-PSK 6 Two 10 1.37 528m 2.59

45 4-PSK 6 Two 40 808m 352m 2.29

46 4-PSK 5 No 0 3.10 200m 15.5

47 4-PSK 5 Two 0 3.12 300m 10.4

48 4-PSK 5 Three 0 1.74 600m 2.9

49 4-PSK 5 Four 0 3.40 1.38 2.4

50 4-PSK 5 No 20 1.72 520m 3.3

51 4-PSK 5 No 40 1.32 340m 3.8

52 4-PSK 5 No 60 328m 124m 2.64

6.7 DISCUSSION FOR TRANSCEIVER DESIGN 3 EXPERIMENTAL

READINGS

It is observed that although the SNR decreases with increasing distance but it is not much

affected or remains in acceptable range up to 7 feet which is our intended range for the

WBAN.

The effect of angular displacement of the receiver from Tx has shown different

characteristics in different modulation schemes. The signal degrades in general when the

receiver moves away from transmitter slowly up to 40 degrees but is much degraded

when moved from 40 to 60 degrees (keeping the distance and light condition same while

observing the effect for the same condition). It effects more in 2-PSK and 4-PSK and less

in ASK and FSK. Amongst all FSK is more tolerant up to 60 degrees and provides good

performance even at 60 degrees which other modulation schemes do not. 2-PSK and 4-

PSK give best results with the increasing distance provided less noise from light and

90

minimum angle displacement (20 to 35 degrees) compared to other modulation schemes.

From the four tested modulation schemes FSK yielded best results in tolerating noise

from light when compared through eye diagrams and SNRs.

It is observed that from the chosen parameters ambient light effects the reception the

most. The effect is quite severe for any distance, modulation scheme or angle at which

the receiver is facing the transmitter. Figure 6.8 (a) to (c) illustrates the effect through I

and Q amplitudes, eye diagram and constellation diagram. The diagrams are plotted by

exporting the data from GW INSTEK DSO to Matlab to verify the SNR, eye diagrams

and constellation results obtained from Tektronix oscilloscope.

In order to get correct eye diagrams and constellation diagrams following settings are

done in Matlab according to the specifications of the MCM31/EV trainer and GW

INSTEK DSO:

No of samples = 4000 (memory length of DSO)

Baud rate = 600 (fixed baud rate for any encoding scheme by MCM31/EV)

The readings are taken at two Sampling Frequencies by Oscilloscope:

1. 25Khz

2. 50KHZ

91

Table 6.9 Matlab required parameters calculation with 25KHZ and 50KHZ

sampling frequency for plotting eye diagram and constellation diagram.

Sampling Frequency =25Khz

Samples per symbol =41.66

Samples per symbol 41

41 samples = 1 symbol

And Total samples = 4000

4000 samples 96 symbols

Sampling Frequency =50Khz

Samples per symbol =83.3

Samples per symbol 83

83 samples = 1 symbol

And Total samples = 4000

4000 samples 48 symbols

92

Fig. 6.8 Matlab plots with 2-PSK with 2 lights ON a) I & Q amplitudes b) Eye

Diagram c) Constellation diagram

93

Fig. 6.9 Matlab plots with 2-PSK with 4 lights ON a) I & Q amplitudes b) Eye

Diagram c) Constellation diagram

94

Fig. 6.10 Constellation diagrams for 2-PSK with a) No light b) 2 lights c) 4 lights

Fig. 6.11 Eye diagrams for 2-PSK with a) No light b) 2 lights c) 4 lights

Fig. 6.12 Constellation diagrams for 4-PSK with a) No light b) 2 lights c) 4 lights

(c) (a) (b)

(c) (a) (b)

(c) (a) (b)

95

Fig. 6.13 Eye diagrams for 4-PSK with a) No light b) 2 lights c) 4 lights

Fig. 6.14 Eye diagrams for FSK with a) No light b) 2 lights c) 4 lights

Fig. 6.15: Eye diagrams for ASK with a) No light b) 2 lights c) 4 lights

Fig 6.8 to 6.15 shows the effects of switching lights ON for various modulation schemes

with the help of eye and constellation diagrams which clearly indicates the better

performance of FSK. The experimental results of increasing distance, angle deviation,

(c)

(b) (a) (c)

(a) (b)

(c) (a) (b)

96

number of lights with ASK, FSK, 2PSK and QPSK on SNR and BER are illustrated in

Fig 6.16 to 6.23.

(c)

Fig. 6.16: SNR curves for varying (a) Angle (b) Distance (c) No of Lights for ASK

14.25 13.1

5.3

0

5

10

15

1 2 3

S

N

R

Distance in feet

SNR vs Distance for ASK

5.3 4.5

1.58 0

2

4

6

No light Two lights Four Lights

S

N

R

No of Lights

SNR vs No of Lights for ASK

16.1

10.8

4 2.5

0

10

20

0 20 40 60

S

N

R

Angle in degrees

SNR vs Angle curve for ASK

(a) (b)

97

(c)

Fig. 6.17: SNR curves for varying (a) Angle (b) Distance (c) No of Lights for FSK

9.33 8.22

5.9

0

5

10

0 40 55

S

N

R

Angle in degrees

SNR vs Angle curve for FSK

9.33 9.11

6.5

0

5

10

No light one light Two Lights

S

N

R

No of Lights

SNR vs No of Lights for FSK

9.33

9.11

9.27

9

9.1

9.2

9.3

9.4

7 6 1

S

N

R

Distance in feet

SNR vs Distance for FSK

(a) (b)

98

(c)

Fig. 6.18: SNR curves for varying (a) Angle (b) Distance (c) No of Light for 2PSK

12.66 12.66

5.64 0

5

10

15

No light one light Two Lights

S

N

R

No of Lights

SNR vs No of Lights for 2PSK

12.66

4.95 4.85 0

5

10

15

0 20 35

S

N

R

Angle in degrees

SNR vs Angle curve for 2PSK

12.66 13

14.6

11

12

13

14

15

6 5 3

S

N

R

Distance in feet

SNR vs Distance for 2PSK

(a) (b)

99

(c)

Fig. 6.19: SNR curves for varying (a) Angle (b) Distance (c) No of Light for 4PSK

8.44

15 14.3

0

5

10

15

20

6 5 3

S

N

R

Distance in feet

SNR vs Distance for 4PSK

15.5

10.4

2.9 2.4

0

5

10

15

20

No light Two light Three Lights Four

S

N

R

No of Lights

SNR vs No of Lights for 4PSK

8.44

15 14.3

0

5

10

15

20

6 5 3

S

N

R

Distance in feet

SNR vs Distance for 4PSK

(a) (b)

100

(c)

Fig. 6.20: BER vs SNR curves for varying (a) Distance (b) Angle(c) No of

Light for ASK

5 6 7 8 9 10 11 12 13 14 1510

-14

10-12

10-10

10-8

10-6

10-4

10-2

SNR

BE

R

SNR vs BER curve for ASK with Varying Distance

1 ft

3 ft

2 ft

2 4 6 8 10 12 14 16 1810

-20

10-15

10-10

10-5

100

SNR vs BER curve for ASK with Varying Angle

SNRB

ER

60 deg

40 deg

0 deg

20 deg

1.5 2 2.5 3 3.5 4 4.5 5 5.510

-3

10-2

10-1

100

SNR vs BER curve for ASK with Varying No of Lights

SNR

BE

R

Two Lights

No Light

Four Lights

(a) (b)

101

(a)

Fig. 6.21: BER vs SNR curves for varying (a) Distance (b) Angle(c) No of

Light for FSK

9.05 9.1 9.15 9.2 9.25 9.3 9.35

10-3.3

10-3.2

SNR vs BER curve for FSK with Varying Distance

SNR

BE

R

1 ft

7 ft

6 ft

5.5 6 6.5 7 7.5 8 8.5 9 9.510

-4

10-3

10-2

10-1

SNR vs BER curve for FSK with Varying Angle

SNR

BE

R

0 deg

40 deg

55 deg

6.5 7 7.5 8 8.5 9 9.510

-4

10-3

10-2

10-1SNR vs BER curve for FSK with Varying No of Lights

SNR

BE

R

No Lights

One Light

Two Lights

(b) (c)

102

(c)

Fig. 6.22: BER vs SNR curves for varying (a) Distance (b) Angle(c) No of Light for 2PSK

5 6 7 8 9 10 11 12 1310

-7

10-6

10-5

10-4

10-3

SNR vs BER curve for 2PSK with Varying No of Lights

SNR

BE

R

Two Lights

One & no Light

12.5 13 13.5 14 14.5 1510

-8

10-7

10-6SNR vs BER curve for 2PSK with Varying Distance

SNR

BE

R

6 ft

5 ft

3 ft

4 5 6 7 8 9 10 11 12 1310

-7

10-6

10-5

10-4

10-3

SNR vs BER curve for 2PSK with Varying Angle

SNRB

ER

20 deg35

deg

0 deg

(a) (b)

103

(c)

Fig. 6.23: BER vs SNR curves for varying (a) Distance (b) Angle(c) No of

Light for 4PSK

2 3 4 5 6 7 8 910

-3

10-2

10-1

SNR vs BER curve for 4PSK with Varying Angle

SNR

BE

R

40 deg

10 deg

0 deg

8 9 10 11 12 13 14 1510

-5

10-4

10-3

10-2

SNR vs BER curve for 4PSK with Varying Distance

SNR

BE

R

6 ft

5 ft

3 ft

2 4 6 8 10 12 14 1610

-5

10-4

10-3

10-2

10-1

SNR vs BER curve for 4PSK with Varying No of Lights

SNR

BE

R

Two lights

Four lights

Three lights

No light

(a) (b)

104

6.7.1 Data Rate

One important parameter for any Wireless Communication is the Data Rate which a

wireless link can support. As WBAN are low data rate applications, so simple

transceiver was used to test the data rate supported here. The MCM31/EV Trainer boards

used for the SNR calculations with respect to change in Ambient light, Distance,

Modulation scheme or Angle as discussed in the previous section could not be used to

calculate the supported the data rate due to the limitation of the fixed 600 baud and

carrier frequency that can be selected from the available frequencies which are 300Hz,

600Hz, 1.2KHz and 1.8KHz. In order to cope with this limitation and keeping the

circuitry as simple as possible, binary ASK modulation was chosen to observe the data

rate with the setup as shown in Figure 6.24.

Fig. 6.24 Test set up for Binary ASK Transceiver for Data Rate Observations

Two Function generators are used to generate carrier wave as well as Information signal

which are fed to The Balanced Modulator card T10B AM/DSB/SSB by EV. This

modulator module can modulate information signal up to 100KHz. The carrier and the

105

information signal frequencies are increased gradually and the modulated output is

observed on the oscilloscope ensuring that the output is not over modulated by adjusting

the information and carrier amplitudes. The Balanced Modulator generates the Modulated

output of the order of 600mV which cannot directly drive an LED so Amplifier is used to

drive the LED. The readings for the Tx signal are taken from Node a as shown in Figure

6.24. Also it is observed that when the frequency is increased the LED becomes dimmer

and the receiver is not able to detect the modulated wave. When the carrier frequency was

increased beyond 5MHz the LED becomes completely off or not visible. Similarly

information signal frequency also has a limit. With the increase in information signal

frequency the received signal gradually decreases in amplitude and less recognizable. The

receiver amplitude is also quite low so it is observed on Oscilloscope after amplification

as mentioned by Node b in Figure 6.24. Figure 6.25 illustrates these effects.

(a) Information Signal 50KHz & Carrier Signal 300KHz (b) Rx vs Tx signal for

50Kb/s data rate

106

(c) Information Signal 100KHz & Carrier Signal 300KHz (d) Rx vs Tx signal for

100Kb/s data rate

(e) Information Signal 100KHz & Carrier Signal 1MHz (f) Rx vs Tx signal for

100Kb/s data rate

107

(g) Information Signal 200KHz & Carrier Signal 2MHz (h) Rx vs Tx signal for

200Kb/s data rate

Fig. 6.25 (a, c, e, g) Information Vs Modulated signal-(b, d, f, h) Tx vs Rx signals at

Node a and Node b

In Figure 6.25 (b) and (e) the amplitude of the received modulated signal is of the order

of 170mV Vp-p with 300 KHz carrier this voltage is significantly reduced to 74mV Vp-p

Figure 6.25 (f) and (h) but it is still recognizable. It can be seen that there is a difference

between the amplitude of the Noise when the Receiver in ON and when it is OFF which

can serve to extract the information signal from the received modulated signal. Although

the target was to achieve data rates in MHz but due to hardware limitations, a data rate of

200Kbits/sec could be achieved. This can be improved with multiple stages of Amplifiers

or more powerful amplifiers at Tx and Rx side. One possible approach is by using

thresholding circuits at the receiver side after the amplification stage and filtering the

noise.

108

6.8 SUMMARY

In this chapter the experimental results of the selected components and transceiver

designs for the Prototype WBAN were discussed. The experimental readings and

observations made for the established Infra-red link are analyzed in this research work for

various parameters such as noise, ambient light, modulation scheme, angular

displacement of receiver from transmitter’s LOS, link distance and data rate.

109

CHAPTER 7

CONCLUSION, LIMITATIONS AND FUTURE

RECOMMENDATIONS

This chapter discusses the overall achievements of the research presented in this thesis.

The main objectives set for this research were sufficiently achieved with some limitations

that can be improved and enhanced further. The subsequent sections converse them

separately.

7.1 ACHIEVEMENTS

The main Objective of this research was to develop a prototype WBAN using infra-red

signaling and analyze its performance instead of using its counterpart i.e. Radio

Frequency WBAN which is achieved with sufficient accuracy. Its performance was

analyzed over various parameters such as distance, noise, angular displacement and

modulation schemes. The good SNR (around 20dB to 26dB) and BER values (within the

range of 0 to 1 %) for the Transceiver design 2, where as for the Transceiver design 3 the

quality of the resulting eye and constellation diagrams demonstrates the feasibility of IR

signaling for WBAN which is very less researched or experimented for this particular

application in spite of its numerous advantages like security and non-interference.

Although use of Infra-red for short range indoor applications or WPAN is found in

applications but less work has been done for this application. Infra-red Based WBAN can

particularly be useful in hospitals and airplanes or environments requiring limited access

110

and high security, as IR signals do not interfere with the signals generated from medical

equipment or aviation equipment which is the case with microwave or RF signals. The

signals are confined within the room and cannot penetrate through walls so it provides

inherent security to the data and avoidance to eavesdropping problem which fulfills one

of the requirements of the WBAN. The IR link distance tested in this research was from 5

to 7 feet which is in compliance with IEEE 802.15.6 standard for WBAN. A research

team at Worcester Polytechnic Institute Worcester, Massachusetts MA 01609, United

States has tried to establish an Optical link using least expensive components in their

thesis “VISIBLE LIGHT COMMUNICATION SYSTEMS”: (March 2015)” using white-

LEDs but they could only perform the successful transmission up to 1 foot with

transmission rate of 1.2kbps [66] . Another research work published in IEEE Photonics

Journal (Feb 2013) reports the successful transmission up to the distance of 1.65m using

white light LED with Manchester coding and have tested their transmission for 1.25Mb/s

and 2.5 Mb/s data rates, but their design uses pair of focusing lens and a medium Power

Amplifier to support the data rate in MHz range, which results in quite expensive design

[67]. Another requirement of this research was low cost and low power WBAN prototype

which is achieved by using least expensive, commercially available and low power

consuming components to build simple transceivers. So the focus was kept on using low

cost and easily available components. The research in scientific reports (2014) [68] has

used spin-nano-oscillator based wireless communication while using microwave

technology and ASK modulation (ASK modulation is used in this research as well for

testing data rate capability of the link with Transceiver design using ThorLAB PIN Rx) .

111

They have reported successful communication with 1m distance and 200kbps data rate.

In this research RF/ microwave or UWB is not used due to the reasons argued in the

previous chapters but the Data rate up to 100Kbps is achieved in this research in

Transceiver Design 3. This data rate is meeting the requirement of the application

intended i.e. for WBAN (10kbps to 100kbps as discussed in Fig 2.5 for physiological

data). The system remains SAR compatible as the LED only emits in the range of mW

plus the IR LED transmitter is not within 20cm range to damage tissue/ skin. The

modulation schemes utilized further reduce the power consumption and hence reduce the

chances of health risks.

The security requirement of WBAN is further achieved by developing a novel protocol

which includes patient and sensor identification. This protocol also provides a mechanism

to reject interference from other IR sources like remote controls for the devices using IR

protocols. The protocol not only incurs very less overhead in computation but also needs

less amount of storage as compared to the other protocols previously presented for

WBAN using RF, microwave or Ultra-wideband technologies incorporating different

encryption schemes. The existing protocols have large overhead ranging from 128 bits to

64 bytes for incorporating security. In this research the protocol is developed to provide

balance between security need and overhead. It only comprises of 32 bits for each packet

with 10 bits sensor data in it. In this research no hardware encryption was used hence the

protocol is also cost effective besides providing less computational overhead.

112

The transceiver design with the remote control receiver IC yielded better SNR and

immunity to reject ambient noise but has a fixed carrier frequency for selected protocol

(Sony, Phillips etc.) and hence limiting the maximum data rate. Its maximum allowable

angle displacement was observed to be 30 to 35 degrees. In this research this IC is

explored and utilized other than its conventional function to control appliances through

remote controls. Whereas for the transceiver built from ThorLAB PIN detector the

maximum range that was tested was 7.5 feet ( 2m) and maximum angle displacement to

be 60 degrees. This link was more sensitive to ambient light for which FSK produced the

best results in tolerating the background noise. Table 7.1 gives the comparison of various

improved parameters in this research.

Table 7.1 Summary of Research in context of specific parameters

S.No Source Ref Parameter Value improvement

1 Choi, H. S

et.al

(2014)

[66] Distance 1m 2m

Data Rate 100kbps 100kbps

Technology Microwave Infra-red

SNR 12.5dB 15dB, 20-26dB

2 Chow,C. W

et.al

(2013)

[67] Distance 1.65m 2.286m

Data Rate 1.2Mbps 200kbps

Technology VLC IR

Encoding Manchester NRZ,

Manchester,

Dibit, Tribit

Modulation None ASK,FSK,PSK

Angle LOS Tested upto 60°

Ambient

Light

Fixed Tested upto 50lux

Cost High Low

3 Ambady, S.

et.al (2015-

USA)

[68] Distance 1 foot 7.5 feet

Data rate 1.2Kbps 200kbps

4 Multiple [32- Packet size 128bits- 32 bits in total

113

47] 64bytes

5 Electronics

Wall Corp

[69] Cost of

wireless

Module

2000/Rs to

9000/Rs

<100 Rs

6 TI 4Q2014

digikey

[70] Power

consumption

Tx Current

RF (Zigbee,

LE Bluetooth)

:20mA to

40mA

IR: 20mA

Infineon

Technologies

AG(2010)

[71] Idle Tx

current

RF: < 1µA IR:0.1µA

Digi-Key

Electronics

(2008)

[72] Peak current

draw

LE =12.5mA,

ANT=17mA,

RF4CE=40mA

IrDA : 10mA

Once the data from the authentic user is received by the IR Receiver it can be accessed by

Smart phone through a user friendly Android App which can save and share the data

from within the Mobile App.

7.2 LIMITATIONS

Due to the hardware limitations and time constraints we could not get the modulators

supporting modulations in MHz. The MCM31/EV Trainer used in experiments supports

only 600 baud and the AM/DSB/SSB T10B EV module only supports modulation

frequency up to 100 KHz so the data rate up to 100Kbits/sec could be verified. The

prototype is tested only for LOS with wider beam widths and can be utilized for

developing diffuse link.

114

7.3 FUTURE RECOMMENDATIONS

This prototype can further be extended to incorporate multiple transmitters and multiple

receivers to send data of different sensors in parallel or multiplexing techniques can be

incorporated to fully utilize the available bandwidth for the optical spectrum. The system

can also be extended to use 1550nm source in order to resolve blocking, further improve

the health issues and enhance mobility. There is room for the improvement in data rate

and range enhancement. Different arrays of highly integrated transmitters and receivers

can be utilized and their suitable geometry can also yield better results.

7.4 SUMMARY

This chapter finally concludes the thesis by highlighting the achievements and novelty of

this research project. It also enumerates the limitations of the project and gives

suggestions for the future extensions for the research made in this thesis.

115

REFEERENCES

[1] Jang, C. S., Lee, D. G., & Han, J. W. (2008, December). A proposal of security framework for

wireless body area network. In Security Technology, 2008. SECTECH'08. International

Conference on (pp. 202-205). IEEE.

[2] Chakraborty, C., Gupta, B., & Ghosh, S. K. (2013). A review on telemedicine-based WBAN

framework for patient monitoring. Telemedicine and e-Health, 19(8), 619-626.

[3] Cao, H., Leung, V., Chow, C., & Chan, H. (2009). Enabling technologies for wireless body area

networks: A survey and outlook. Communications Magazine, IEEE, 47(12), 84-93.

[4] S. Arnon, (Marcel Dekker, 2003) “Optical wireless communication,” invited chapter for The

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