REAL TIME BIOMEDICAL SIGNAL TRANSMISSION USING VISIBLE LIGHT COMMUNICATION

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1 REAL TIME BIOMEDICAL SIGNAL TRANSMISSION USING VISIBLE LIGHT COMMUNICATION D.Ilakkiaselvan 1, K.K.Naveen2, M.Veerasekar, S.Ponnaiah4 1 Department of Electronics &Communication, University College of Engineering, Villupuram 2, 3, 4 Student, University College of Engineering, Villupuram mdilakki@gmail.com,naveenkk995@gmail.com,veera0508@gmail.com Abstract - An electrocardiogram (ECG) is a graph produced by an electrocardiograph, which records the electrical activity of the heart over time. Analysis of the various waves and normal vectors of depolarization and repolarization yields important diagnostic information. It is the gold standard for the evaluation of cardiac arrhythmias. It guides therapy and risk stratification for patients with suspected acute myocardial infraction. In health care applications the utilization of RF signals is inefficient since it is affected by electromagnetic interference. This leads to decrease in efficiency, reliability and accuracy and also causes health hazards. So to overcome these disadvantages VLC (visible light communication) is used. Keywords: Visible Light Communication, Data through Illumination, PWM, Matlab coding, Peak Detection I. INTRODUCTION Nowadays, wireless communications has become fundamental to our lives and we transmit a lot of data every day. The main way to transmit wireless data is by using electromagnetic waves, in particular radio waves. However, radio waves can support only limited bandwidth because of restricted spectrum availability and interference. Furthermore, radio spectrum is full to bursting and it is difficult to find radio capacity to support media applications. In health care applications the utilization of RF signals is inefficient since it is affected by electromagnetic interference. This leads to decrease in efficiency, reliability and accuracy and also causes health hazards. There is an emerging wireless communication with a promising future and which can be a complement of radio waves-visible Light Communication (VLC). VLC is free from health hazards and EMI interference and the spectrum is available for free of cost. Electrocardiogram is an important measurement in health care applications Radio waves are almost used in all fields of wireless communication. Hence the available bandwidth is less and proves costly. Also it is affected by EMI interference and is hazardous in health care applications. Cardiovascular diseases have become the major cause of deaths globally. To monitor it continuously at free of Cost and to use the free available bandwidth of visible light spectrum, visible light communication technology is proposed. Also it is free from interferences. The main objective of this project is to improve the efficiency, accuracy by using visible light spectrum for transmission of the patient s biomedical data (ECG) in real time. White LED beam is used as the transmitter and photodiode is used as the receiver to receive the transmitted light signal, which is free from EMI and other RF interferences. The transmitted signal is then continuously monitored in the PC. II. EXISTING TECHNOLOGIES AND PROBLEMS ON IT: The currently existing technologies of wireless ECG use Radio waves which restricts transmission in intensive care units due to its hazardous nature and interference. Present day ECG monitor devices are bulky and costly. A.Radio frequency (RF) The wide implementation of radio frequency (RF) wireless technology in healthcare centers like hospitals and nursing homes has been often associated with mobility, feasibility and high speed features of this ISSN: Vol.3 No.1 Jan/Feb

2 technology to provide real time information such as biomedical signal and patient information.but the prolonged usage of radio frequency (RF) wireless technology in the medical field leads to various health hazards due to continuous emission of RF radiations. B. VLC over IR Communication Infrared Communication sends data at a rate of 20Mb/s while VLC can send data up to 100Mb/s. The transmission distance for VLC is possible up to several meters due to its illumination requirement. Since the infrared communication is used for a remote controller, the maximum distance is ~ 3 meters. Due to the wavelength of the light source, the noise sources will be different. For infrared communication, noise comes from ambient light containing infrared light. In the case of VLC, the sunlight and other illumination light can be noise sources. Infrared Technology is used in communication only while VLC is used both for illumination and communication. Infrared Technology is used in remote control and point-to-point connection while VLC can beused in many applications such as smart lighting, hazardous environments, mobile connectivity, under water communication etc. C. Visible Light Communication (VLC) Visible Light Communication (VLC) technology, one of the advanced optical wireless communication technologies, in which light in the visible region (375nm-780nm) is used as a medium for data transmission is more secure and achieves high data rate as compared to conventional wireless technologies like Wi-Fi, Bluetooth, Wi-max etc., which use radio waves for communication. While using wireless internet, when more than one device is tapped into the network, then bandwidth got frustrated at the slow speeds. To overcome the shortage of bandwidth light can be used to transfer the data which can be known as DATA THROUGH ILLUMINATION. The idea behind is that, infra-red remote is slightly modified i.e., LED light bulb that varies in intensity which cannot be followed by the naked eye. III. VLC CHARACTERISTICS: Visible light communication is a data communication technology that uses visible light between 380 nm and 780 nm. These wavelengths correspond to a frequency range of approximately 384 THz to 789 THz. Fig 1 :Electromagnetic Spectrum A. VLC versus Radio Waves Although radiofrequency communications is the most popular technology today, it has its disadvantages when compared to VLC. ISSN: Vol.3 No.1 Jan/Feb

3 Capacity:Radio spectrum is full and it is difficult to find radio capacity to support the demand of wireless data transmissions for media applications. Radio waves are limited, expensive and only a certain range of it is available. By using VLC more spectrum and infrastructure are available because there are lots of LED-based lights installed in the world that are potentially VLC transmitters. The available bandwidth is also higher Δf (RF)~300 GHz Δf (VLC)~400 THz Efficiency: Radio waves consume a lot of energy while VLC is highly energy efficient because LED can be illuminated and also used to transmit data at the same time. Furthermore, VLC transmitters and receivers devices are cheap and there is no need for expensive RF units Availability: Radio waves cannot be used in some sensitive scenarios like hospitals, aircraft, etc.., due to interferences with other devices. On the other hand, VLC can be used when there is light and no interference with radiofrequency based systems exits. Hence,this technology can be used in many places Security: Radio waves penetrate through walls and they can be intercepted. By using VLC it can only transmit data where the light is because light does not penetrate through walls, that is to say, there will be a very secure data communication. Human health: The transmission power of radio waves can cannot be increased over a certain level because there are serious health risks for humans. As VLC is harmless for the human body therefore the transmission power can be increased if neede IV. BLOCK DIAGRAM: Fig.2.Block diagram 1. Lead electrodes 2. ECG monitoring circuit 3. Microcontroller unit 4. LED 5. Photo diode 6. PC Display( peak detection) The three ECG electrodes (Lead), attached to both the arms and to right leg collects the ECG signals from the patient s body. These signals are fed to the ECG monitoring circuit which amplifies the signals and filters it. The amplified signal is then fed to the microcontroller unit that converts the analog values of the ECG signal to digital values and sends them through LED and also displays the result in the LCD. The signal from LED is detected by photodiode and is displayed in the PC as values and waveform. It indicates with an alarm in case of any abnormality in the peak of the detected wave. The ECG waveform helps in studying the patient s health condition. ISSN: Vol.3 No.1 Jan/Feb

4 V. HARDWARE DESCRIPTION A. Power Supply Fig.3.Block diagram of power supply The ac voltage, typically 220V rms is connected to a transformer, which steps that ac voltage down to the level of the desired dc output. A diode rectifier provides a full-wave rectified voltage that is initially filtered by a simple capacitor filter to produce a dc voltage. This resulting dc voltage usually has some ripple or ac voltage variation. The regulator circuit removes the ripples and also remains the same dc value even if the input dc voltage varies. This voltage regulation is usually obtained using one of the popular voltage regulator IC units. B.Components Rectifier section : Bridge rectifier Filtering section :Capacitor 0.01uF,1000uF Regulator section :IC 7805,7812,7912 C.ECG Monitering Circuit Fig.4.ECG Monitering Circuit (Part 1) In this circuit there are three electrodes used to measure the ECG waves in which two electrodes are fixed with left and right hand and the other electrode is fixed in the right leg which acts as reference ground ISSN: Vol.3 No.1 Jan/Feb

5 electrode. Electrode 1 and Electrode 2 pick up the ECG waveform both the hands. Then the ECG waves are given to instrumentation amplifier section which is constructed by the TL072 operational amplifier. The TL072 are high speed J-FET input dual operational amplifier incorporating well matched, high voltage J-FET and bipolar transistors in a monolithic integrated circuit. The devices feature high slew rates, low input bias and offset current and low offset voltage temperature coefficient. The instrumentation amplifier amplifies the differential signals from both electrodes. This amplified ECG waves contains the line frequency, high frequency and low frequency noise signals. So the ECG wave is fed to filter section. The filter is a band pass filter (comprising of high pass filter and low pass filter) which is used to remove the high frequency and low frequency noise signals. Fig.5. IC TL072 Fig.6.ECG Monitering Circuit (Part 2) After the filtration, the ECG wave is given to Pulse Width Modulation unit. In this section, the ECG wave is converted to pulse format in order to perform the isolation. The isolation is done by the opto-coupler. The isolation is necessary to isolate the human body signals from that of the monitoring equipment such as CRO, PC, etc. Then the ECG pulse format wave is given to PWM demodulation unit in which the pulse format ISSN: Vol.3 No.1 Jan/Feb

6 is reconstructed to original wave. Then the wave is fed to notch filter section in order to remove the line frequency noise signal. A notch filter is a band-stop filter with a narrow stop band (high Q factor). Notch filters are used to reduce or prevent feedback, while having little notable effect on the rest of the frequency spectrum. Typically, the width of the stop band is less than 1 to 2 decades. The notch filter is constructed by the operational amplifier TL075. Finally noise free ECG wave is given to the amplifier. Then the amplified signal is given to monitored device such as CRO, PC, etc. D. PIC 16F877A The microcontroller that has been used for this project is PIC16F877A. PIC microcontroller is the first RISC based microcontroller fabricated in CMOS (Complementary Metal Oxide Semiconductor) that uses separate bus for instruction and data, allowing simultaneous access of program and data memory.the main advantage of CMOS and RISC combination is low power consumption resulting in a very small chip size with a small pin count. Technology that is used in PIC16F877A is flash technology, so that data is retained even when the power is switched off. Easy Programming and erasing are other features of PIC 16F877A. Fig.7.Pin Diagram of 16F877A E. LCD Display LCD (Liquid Crystal Display) screen is an electronic display module and finds a wide range of applications. A 16x2 LCD display is very basic module and is very commonly used in various devices and circuits. These modules are preferred over 1 and other multi segment LEDs. The reasons being: LCDs are economical; easily programmable; have no limitation of displaying special & even custom characters (unlike in seven segments), animations and so on. A 16x2 LCD means it can display 16 characters per line and there are 2 such lines. In this LCD each character is displayed in 5x7 pixel matrix. This LCD has two registers, namely, Command and Data. The command register stores the command instructions given to the LCD. ISSN: Vol.3 No.1 Jan/Feb

7 Fig.8.LCD Pin Diagram E. RS 232 In communications, RS-232 is a standard for serial binary data interconnection between a DTE (Data terminal equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports. Fig.9.RS 232 F. White LED From the communication viewpoint the phosphor based white LED has longer rise/fall times due to phosphor absorption/re-emission times. It is noted that each LED can find its appropriate applications for VLC Systems. Fig.10. 1W Power LED ISSN: Vol.3 No.1 Jan/Feb

8 G.Photo Detector A photodiode is a semiconductor device that converts light into current. The current is generated when photons are absorbed in the photodiode. A small amount of current is also produced when no light is present. Photodiodes may contain optical filters, built-in lenses, and may have large or small surface areas. Photodiodes usually have a slower response time as their surface area increases. The common, traditional solar cell used to generate electric solar power is a large area photodiode. Fig.11. Photo Detector V. CONCLUSION: The ECG signal has been transmitted using Visible Light Communication. It improves the reliability of transmission and reduces health hazards. White LED has been used as the transmitter and photodiode has been used as the receiver to receive the transmitted signal. The received signal has been displayed in the PC for continuous monitoring of the patient s ECG signal using MATLAB and the peak of the ECG signal has also been detected to indicate any abnormalities. REFERENCES [1]Yee Yong Tan,Sang-Joong Jung and Wan-Young Chung (2013), Real time biomedical signal transmission of mixed ECG signal and patient information using visible light communication,35 th Annual International conference of the IEEE EMBS [2] Ke Wu, Debabani Choudhury, Hiroshi Matsumoto (2013), Wireless Power Transmission, Technology and Application, proceedings of the IEEE on( vol.101, No.6) [3] Fensil. R, Gunnarson. E, Hejlisen. O (2004), A wireless ECG system for continuous event recording and communication to a clinical alarm station using RF, Engineering in Medicine and Biology Society, IEMBS '04. 26th Annual International Conference of the IEEE (Volume:1 [4] Jacqueline J.George, Mohammed Hayder Mustafa, Nada Mahjoub Osman, NuhaHashimAhmed,Da ad Mohammed Hamed (2014), A Survey on Visible Light Communication,International Journal Of Engineering And Computer Science ISSN: [5] D.Doberv, Two-electrode low supply voltage electrocardiogram signal amplifier,centre of Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria [6] Joachim H. Nagel Biopotential Amplifiers, University of Stuttgart, 2000 by CRC Press LLC [7] Sayanti Chattopadhyay1, Susmita Das2, Avishek Nag3, Jayanta Kumar Ray4, Soumyendu Bhattacharjee5, Dr. BiswarupNeogi6, Design and Simulation Approach Introduced to ECG Peak Detection with Study on Different Cardiovascular Diseases [8] P.D.Khandait, Features Extraction of ECG signal for Detection of Cardiac Arrhythmias, Department of Etrx. K.D.K.C.E.,Nagpur,National Conference on Innovative Paradigms in Engineering & Technology (NCIPET-2012) Proceedings published by International Journal of Computer Applications (IJCA) [9] Naazneen M. G., SumayaFathima, SyedaHusnaMohammadi, Sarah Iram L. Indikar, Abdul Saleem, Mohamed Jebran (May 2013), Design and Implementation of ECG Monitoring and Heart Rate Measurement System,International Journal of Engineering Science and Innovative Technology (IJESIT) Volume 2, Issue 3 ISSN: Vol.3 No.1 Jan/Feb