Design and Implementation of an Ethernet-VLC Interface for Broadcast Transmissions

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Design and Implementation of an Ethernet-VLC Interface for Broadcast Transmissions Seminar report submitted in partial fulfillment of the requirements for the Award of the degree

BACHELOR OF TECHNOLOGY in ELECTRONICS AND COMMUNICATION ENGINEERING Submitted by

VISHAL K M

Under the guidance of

Mr. EMIL RAJ VARGHESE Assistant Professor Dept. of Electronics and Communication Engineering

JANUARY 2013 DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING MANGALAM COLLEGE OF ENGINEERING, ETTUMANNOOR Affiliated to Mahatma Gandhi University, Kerala

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MANGALAM COLLEGE OFENGINEERING, ETTUMANOOR, KOTTAYAM

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

CERTIFICATE This is to certify that the Seminar report entitled “Design and Implementation of an EthernetVLC Interface for Broadcast Transmissions” is the bonafide report of the work done by VISHAL K M of Bachelor of Technology in ELECTRONICS AND COMMUNICATION ENGINEERING towards the partial fulfillment of the requirement for the award of the Degree of Bachelor of Technology by the Mahatma Gandhi University, Kerala during the academic year 2012-2013.

Internal Guide

Head of the department

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ACKNOWLEDGEMENT I owe my heartfelt gratitude to God almighty for all the blessings showered on me during this endeavor. I take this opportunity to express my sincere gratitude to all the people who have been instrumented in bringing out this work to the correct form. I would like to express my sincere thanks to the Principal, Mangalam College of Engineering, Dr. N. K. VARGHESE for his precious advice for the successful completion of this seminar. I am very much thankful to Prof. ASHA PANICKER, HOD, Electronics and Communication Engineering Department, for her timely help and encouragement. I am deeply indebted to my Seminar coordinator Mr. EMIL RAJ VARGHESE, Asst. Professor, Electronics and Communication Engineering Department for providing conductive environment and requisite library and internet facilities. I thank my internal guide Mr. EMIL RAJ VARGHESE, Asst. Professor, Electronics and Communication Engineering Department for his proper guidance and support during the course of this seminar. I also thank the Staff members of Electronics and Communication Engineering Department, for their co-operation for the completion of the seminar. Finally I thank my friends, classmates and family for providing me the strength and endurance.

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ABSTRACT In this work, a complete interface between Ethernet and Visible Light Communications (VLC) networks is presented. It requires the use of previously proposed DPPM schemes for this kind of applications, but with some modifications so as to keep constant duty cycle in order to assure its use in illumination facilities [2]. The prototype has been tested using a 2Mbps VLC Link, obtaining distances of, at least, 3 meters in an interfering environment. The PPM characteristics allow transmission without severe signal degradation on this environment. This Ethernet- VLC interface is intended to demonstrate the capability of IP broadcast applications of this kind of devices. This interface performs packing functions and flow control.

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CONTENTS CHAPTER

1

2

TOPICS

PAGE No

ABSTRACT

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LIST OF FIGURES

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LIST OF ABBREVIATIONS

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INTRODUCTION

1

1.1 EXISTING TECHNOLOGIES

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1.2 PROPOSED TECHNOLOGY

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VISIBLE LIGHT COMMUNICATOIN

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2.1 MOTIVATION 2.2 HISTORY 3

ETHERNET

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4

VLC-ETHERNET INTERFACE

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4.1 SYSTEM ARCHITECTURE 4.2 SYSTEM IMPLEMENTATION 5

ADVANTAGES

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6

DISADVANTAGES

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7

APPLICATIONS

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8

CONCLUSION

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9

REFERENCES

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LIST OF FIGURES Figure No.

Title

Page No.

2.1

Photophone

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2.2

Basic Block Diagram

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4.1

System Architecture

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4.2

System Block Diagram

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4.3

Different Pulse Position Modulation Waveforms

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4.4

Payload Extraction And Packaging

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4.5

Transmission/Reception Complete Flow Chart

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LIST OF ABBREVIATIONS

VLC

Visible Light Communication

LED

Light Emitting Diode

DPPM

Differential Pulse Position Modulation

LAN

Local Area Network

Wi-Fi

Wireless Fidelity

Li-Fi

Light Fidelity

Design and Implementation of an Ethernet-VLC Interface for Broadcast Transmissions

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CHAPTER 1 INTRODUCTION In the last years, different research lines have focused o energy saving techniques for illumination sources, since current lamps present very low power efficiency. In this way new more efficient lighting devices are being developed replace incandescent and fluroscent lights (including low consumption bulbs). These systems make use of Solid State Lightning (SSL) which, compared to filament heating electric arc (both of which are used in conventional lamps allows to convert electric energy into optical emitted power more efficiently. They are based on LED devices, which provide high-level savings in energy consumption and have a lifespan between 10000 and 50000 hours. Using illumination fixtures for data transmission is not new concept; however, only the new SSL devices allow the implementation of feasible communication links because their available bandwidth. As a consequence of the increasing development of these new devices, multiple contributions VLC have been proposed. The aim of these works is based on adding the communication capability to the lamp, while maintaining its main function as light source. Therefore, the transmitted data sign should not alter the illumination perception at the user eye. This implies some restrictions on the emitted signal in order avoid light flickering. For this reason, in this work, a modified Differential Positioning Pulse Modulation (DPPM) technique which always presents only a pulse in each transmission symbol, has been proposed. On the other side, an interface between wired network (Ethernet) and Optical network has been developed. Due to the asymmetrical properties of these links, a flow control at the optical network access point has been implemented.

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1.1 EXISTING TECHNOLOGIES 1.1.1 ETHERNET (Ethernet over Copper) Ethernet is the most widely-installed local area network (LAN) technology. An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires. The most commonly installed Ethernet systems are called 10BASE-T and provide transmission speeds up to 10 Mbps. Fast Ethernet or 100BASE-T provides transmission speeds up to 100 megabits per second and is typically used for LAN backbone systems, supporting workstations with 10BASE-T cards. Gigabit Ethernet provides an even higher level of backbone support at 1000 megabits per second (1 gigabit or 1 billion bits per second). Pulling cable from a distant source to the site, then preparing and installing the cable internally to the facility and, likely to every room in the facility is a daunting and expensive task. That is why the option of wireless local area networking is becoming popular.

1.1.2 Wi-Fi Wi-Fi is a popular technology that allows an electronic device to exchange data wirelessly (using radio waves) over a computer network, including high-speed Internet connections. Wi-Fi can be less secure than wired connections (such as Ethernet) because an intruder does not need a physical connection. The use of Wi-Fi band that is 2.4 GHz does not require a license in most countries provided that is stays below limit of 100mW and one accepts interference from other sources; including interference which causes the users devices to no longer function. Power consumption is fairly high compared to some other standards, making the battery life and heat a concern to some users. Wi-Fi uses the unlicensed 2.4GHz spectrum, which often crowded with other devices such as Bluetooth, microwave ovens, cordless phones, or video sender devices, and among many others. This may cause degradation in performance. Wi-Fi networks have limited range. A typical Wi-Fi home router might have a range of 45m (150ft) indoors and 90m (300ft) outdoors. Free access points can be used by the malicious to anonymous to initiate an attack that would be extremely difficult to track beyond the owner of the access point.

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1.2 PROPOSED TECHNOLOGY In the past few years, an unprecedented demand for wireless technologies has been taking place. Usually, the radio frequency (RF) is used for wireless data transmission, but it has its bandwidth constraints. In some cases where the distance between transmitter and receiver is relatively small, RF technology can be replaced by visible light communication (VLC) to provide high data rates. In addition, this technique not only provides better security than RF communication, but it is also less prone to interference for indoor situations. VLC uses spectral region with corresponding wavelengths lying between 450nm-900nm and offers potentially large bandwidths. High power LEDs used for lighting are simultaneously used to transfer data, over the wireless channel. On the receiver side a photo sensitive device is used for data reception.

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CHAPTER 2 VISIBLE LIGHT COMMUNICATOIN Visible light Communication (VLC) is a modern communication technology which employs visible solid-state light sources (LEDs) for transmitting data wirelessly as they are used for general illumination at the same time." 2.1 MOTIVATION Using visible light for data transmission entails many advantages and eliminates most drawbacks of transmission via electromagnetic waves outside the visible spectrum. For instance, few known visible light-induced health problems exist today, exposure within moderation is assumed to be safe on the human body [Wurtman 1975]. Moreover, since no interference with electromagnetic radiation occurs, visible light can be used in hospitals and other institutions without hesitation. Furthermore, visible light is free. No company owns property rights for visible light and thus no royalty fees have to be paid nor do expensive patent-license have to be purchased in order to use visible light for communication purposes [Langer 2010]. Visible light can serve as an entirely free infrastructure to base a complex communication network on. VLC is mostly used indoors and transmitted light consequently does not leave the room when the doors are closed and the curtains drawn, because light cannot penetrate solid objects such as walls or furniture. Therefore, it is hard to eavesdrop on a visible light based conversation, which makes VLC a safe technology if the sender intends to transmit confidential data. The most important requirement that a light source has to meet in order to serve communication purposes is the ability to be switched on and again in very short intervals, because this is how data is later modulated. This rules out many conventional light sources, such as incandescent lamps. Over the course of the last years, usage of LEDs has risen sharply [Won et al. 2008]. LEDs are often built into traffic and braking lights, but they also push conventional illumination methods (such as incandescent lamps) aside generally (LEDs are applied in more and more flashlights, headlights, status displays etc.) and might replace these other light sources entirely in the near future ([Wesson 2002] and [Evans 1997]). LEDs fulfill the above

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requirement in that they can be switched on and o_ quickly. Thus they are well suited to modulate data into visible light. In order to receive data sent out in this way, photodiode receivers or CCD/CMOS sensors can be used which are typically built into digital cameras.

2.2 History Though the research and development of visible light communications systems was started not long ago (2003), man has always resorted to some form of communications employing a light source since Stone Age. The age-old techniques of optical communication are listed in a chronological order: Heliograph: In bygone times, reflecting mirrors were used to deliver information over a large distance. This technique is referred to as `Heliograph'. Lamps and Fires: Burning kites were used in the battlefield for communication. Similarly, lamps were used in lighthouses as well. Ship-to-ship communication: Morse code was used for communication between ships. The message was transmitted in the form of `marks' and `spaces'.

Fig 2.1

Photophone

Photophone: In 1880 Graham Bell devised a wireless communication system called a Photophone in which sunlight was used as the optical source. A vibrating mirror was used to modulate and reflect light to the receiver consisting of a parabolic mirror. This system worked for a distance of around 700 ft.

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Traffic Signals: Traffic signals also employ visible light communication in principle as three different colours are used to communicate three different messages to the onlookers. 2.3 VISIBLE LIGHT COMMUNICATIONS CONSORTIUM The Visible Light Communications Consortium (VLCC) which is mainly comprised of Japanese technology companies was founded in November 2003. It promotes usage of visible light for data transmission through public relations and tries to establish consistent standards. A list of member companies can be found in the appendix. The work done by the VLCC is split up among 4 different committees:

2.3.1 Research Advancement and Planning Committee This committee is concerned with all organizational and administrative tasks such as budget management and supervising different working groups. It also researches questions such as intellectual rights in relation to VLC.

2.3.2 Technical Committee The Technical Committee is concerned with technological matters such as data transmission via LEDs and fluorescent lights.

2.3.3 Standardization Committee The standardization committee is concerned with standardization efforts and proposing new suggestions and additions to existing standards.

2.3.4 Popularization Committee The Popularization Committee aims to raise public awareness for VLC as a promising technology with widespread applications. It also conducts market research for that purpose.

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2.4 TECHNOLOGY

Fig 2.2 Basic Block Diagram

2.4.1 TRANSMITTERS Every kind of light source can theoretically be used as transmitting device for VLC. However, some are better suited than others. For instance, incandescent lights quickly break down when switched on and off frequently. These are thus not recommended as VLC transmitters. More promising alternatives are fluourescent lights and LEDs. VLC transmitters are usually also used for providing illumination of the rooms in which they are used. This makes fluorescent lights a particularly popular choice, because they can icker quickly enough to transmit a meaningful amount of data and are already widely used for illumination purposes. However, with an ever-rising market share of LEDs and further technological improvements such as higher brightness and spectral clarity [Won et al. 2008], LEDs are expected to replace fluorescent lights as illumination sources and VLC transmitters. The simplest form of LEDs are those which consist of a bluish to ultraviolet LED surrounded by phosphorus which is then stimulated by the actual LED and emits white light. This leads to data rates up to 40 Mbit/s [Won et al. 2008]. RGB LEDs do not rely on phosphorus any more to generate white light. They come with three distinct LEDs (a red, a blue and a green one) which, when lighting up at the same time, emit light that humans perceive as white. Because there is no delay by stimulating phosphorus first, Data rates of up to 100 MBit/s can be achieved using RGB LEDs ([Won et al. 2008]). In recent years the development of resonant cavity LEDs (RCLEDs) has advanced considerably. These are similar to RGB LEDs in that they are comprised of three distinct LEDs, but in addition they

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are transmitted with Bragg mirrors which enhance the spectral clarity to such a degree that emitted light can be modulated at very high frequencies. In early 2010, Siemens has shown that data transmission at a rate of 500MBit/s is possible with this approach [Siemens 2010]. It should be noted that VLC will probably not be used for massive data transmission. High data rates as the ones referred to above, were reached under meticulous setups which cannot be expected to be reproduced in real-life scenarios. One can expect to see data rates of about 5 kbit/s in average applications, such as location estimation [Haruyama et al. 2008]. The distance in which VLC can be expected to be reasonably used ranges up to about 6 meters [Won et al. 2008].

2.4.2 RECEIVERS The most common choice of receivers are photodiodes which turn light into electrical pulses. The signal retrieved in this way can then be demodulated into actual data. In more complex VLC-based scenarios, such as Image Sensor Communication [Iizuka and Wang 2008], even CMOS or CCD sensors are used (which are usually built into digital cameras).

2.4.3 MODULATION In order to actually send out data via LEDs, such as pictures or audio files, it is necessary to modulate these into a carrier signal. In the context of visible light communication, this carrier signal consists of light pulses sent out in short intervals. How these are exactly interpreted depends on the chosen modulation scheme, two of which will be presented in this section. At first, a scheme called subcarrier pulse-position modulation is presented which is already established as VLC-standard by the VLCC. The second modulation scheme to be addressed is called frequency shift keying, commonly referred to as FSK. A detailed account on modulation can be found in Sugiyama et al. [2007]. They also explore how to combine pulse-position modulation with illumination control. 2.4.3.1 PULSE-POSITION MODULATION To successfully carry out subcarrier pulse-position modulation (SC-PPM) a time window T is chosen in which exactly one pulse of length T/k is expected. Thus, subcarrier pulse-position modulation can also be described as parameterized form, i.e. SC - kPPM. k has to be a power of two, i.e. k = 2l for some l. Then there are k = 2l different points of time for

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the pulse to occur. Suppose a pulse is registered a some point k’ ≤ k. The data represented by this pulse is then simply the number k’ written as k-digit binary number.

2.4.4 STANDARDIZATION EFFORTS 2.4.4.1 IEEE 802.15 TG7 Within the IEEE working group for wireless and personal area networks (802.15) the IEEE has formed task group 7 (TG7) which is supposed to write a PHY and MAC standard for VLC. Unfortunately though as of writing this document, information on their progress (the most recent of which dates back to January 2009) is scarce.

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CHAPTER 3 ETHERNET Ethernet is a family of computer networking technologies for local area networks (LANs). Ethernet was commercially introduced in 1980 and standardized in 1985 as IEEE 802.3. Ethernet has largely replaced competing wired LAN technologies. The Ethernet standards comprise several wiring and signaling variants of the OSI physical layer in use with Ethernet. The original 10BASE5 Ethernet used coaxial cable as a shared medium. Later the coaxial cables were replaced by twisted pair and fibre optic links in conjunction with hubs or switches. Data rates were periodically increased from the original 10 megabits per second to 100 gigabits per second. Systems communicating over Ethernet divide a stream of data into shorter pieces called frames. Each frame contains source and destination addresses and error-checking data so that damaged data can be detected and re-transmitted. As per the OSI model Ethernet provides services up to and including the data link layer. Since its commercial release, Ethernet has retained a good degree of compatibility. Features such as the 48-bit MAC address and Ethernet frame format have influenced other networking protocols. Higher level network protocols like Internet Protocol (IP) use Ethernet as their transmission medium. Data travels over Ethernet inside protocol units called frames. The run length of individual Ethernet cables is limited to roughly 100 meters, but Ethernet networks can be easily extended to link entire schools or office buildings using network bridge devices.

3.1 ETHERNET FRAME A data packet on an Ethernet link is called an Ethernet frame. A frame begins with preamble and start frame delimiter. Following which, each Ethernet frame continues with an Ethernet header featuring destination and source MAC addresses. The middle section of the frame is payload data including any headers for other protocols (e.g. Internet Protocol) carried in the frame. The frame ends with a 32-bit cyclic redundancy check which is used to detect any corruption of data in transit.

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CHAPTER 4 VLC-ETHERNET INTERFACE 4.1 SYSTEM ARCHITECTURE This system is designed to allow broadcast transmissions from a wired LAN (Ethernet in this case) to the VLC network. Because of the different bit rates in both systems, a flow control implementation is necessary at the VLC access point node. Taking into account all these factors, the complete system block diagram is shown in Fig. 2. This work focuses on Modulator/Demodulator and Flow Control Blocks development. The system uplink shown in Fig. 2 consists of an infrared link between optical nodes and VLC access point, which performs a command channel for the downlink broadcast transmissions. The main limitation of this link is determined by its low power transmission and wide coverage area, employing optical devices that do not need critical alignments, so that, a low data rate link (125 Kbps) has

been

selected.

Fig 4.1

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Fig 4.2

4.1.1 Visible Optical Channel Characteristics As already commented on, the main restrictions of these systems are the limited bandwidth and the need of maintaining constant luminescence along all communication time due to their simultaneous use as conventional lamps. Long sequences of “zeroes” or “ones” in an On-off Keying (OOK) communications system could cause illumination flickering. At the same time, high communications rates are not possible because of their high rise and fall times. For typical white LED lamps, minimum pulse width allowed is about 200ns as shown in Fig. 3. Besides, this channel is affected by interference signals caused by ambient light, especially by incandescent and fluorescent lamps, with frequency components under 1 MHz.

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4.1.2 DPPM Modulator and Demodulator Pulse position modulating (PPM) techniques are extensively used in wireless optical links, due to their high average-power efficiency and artificial illumination effect reduction. Moreover, this technique allows the system to work with lights turned “off” and “on”, and with varying PPM pulse width without optical power losses. This is achieved by means of a variation in the chip pulse duration. In this case, 20% of symbol duration has been selected for the “turn off” mode and 80% for the “turn on” mode. The main inconvenience of these modulation techniques is the need of complex synchronism systems to ensure correct detection. To avoid this, Differential Pulse Position Modulation (DPPM) could be selected, which presents non coherent detection capability at the receiver. However, the bit rate is not constant during transmissions and this can affect the system performance as illumination fixture. In this work, a modified 4-DPPM has been developed in order to solve this problem. This technique ensures that transmitted signal duty cycle is always the same, so that light intensity variations do not occurs.

Fig 4.3 Figure 4.3 shows the waveforms corresponding to the Pulse Position Modulations cited above.

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In fact this is a PPM scheme where position of the next chip is given by:

=

{

−1 +

{

Where

−

−1 +

( (

−1 + −1 +

)≥ )<

} }

= number of chips available,

−1 = Last chip position and

= Symbol value.

This modified DPPM scheme presents the same bandwidth and power requirements than the conventional PPM one, but allows non coherent detection at the receiver, like in a DPPM receiver. This is achieved by counting clock samples between rising edges (distances, including a guard interval to compensate LED fall time). Correspondence between symbol and distances for the proposed scheme is shown in Table 1. It can be seen that there are two possible distances for the same symbol in some cases. The transmission block selects the appropriate one in order to ensure the constant duty cycle (20%) of the transmitted signal explained before. To obtain a duty cycle of 80%, the transmitted signal is inverted.

6.1.3 Interface Ethernet-Optical Access Point The developed system transmits information encapsulated in UDP packets. The interface block performs the payload extraction and encapsulation and the Flow control between Ethernet network and serial interface. These processes are shown in Fig. Flow control is necessary because optical transmission rate is about 2 Mbps and Ethernet frames arrive to the access point at 10Mbps data rate. Payload from UDP frames are buffered before their transmission through optical link. After UDP payload extraction, encapsulation is carried out to ensure correct detection. A header is added to each UDP payload before its serial transmission and modulation. At the receiver side, this header is detected and data are buffered. Figure 6 shows this packaging process. After that, the receiver encapsulates the buffered payload in a UDP frame and transmits it to the client node by an Ethernet connection, so that the complete process is accomplished. UDP facilities are included in the employed Xilinx core.

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Fig 4.4

Fig 4.5

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4.2 SYSTEM IMPLEMENTATION The proposed scheme has been implemented using a Xilinx Spartan-3 design kit, which includes Ethernet MAC facilities and cores to negotiate communications between the wired network and the optical link. This design kit implements the following features: flow control, modulation/demodulation and UDP frames payload unpacking and packing. The complete system has been tested over a visible optical link composed by a commercial visible LED lamp (20 white LED diodes array, each of them with the time response shown in Fig. 3). At the transmitter, a circuit based on SN75452 open collector logic gates has been used. The reception circuit basically consists on a transimpedance amplification stage and two HAMAMATSU S7510 photodiodes, with a total active area of 132 mm2.

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CHAPTER 5 ADVANTAGES VLC provide Virtual unlimited bandwidth with over 540 THz for wavelengths in the range [200-1550nm]. VLC offer a good bandwidth compared to other systems. A further advantage is that VLC systems can transmit data more securely over short distances than radiofrequency/microwave communications devices whose signals can be easily detected outside the rooms and buildings they originate in.

5.1 SUPERIORITY OVER RF WAVES As was demonstrated earlier, the visible light has considerable edge over RF waves in many fields. This is the one of the main advantage of VLC which makes the technology outstanding.

5.2 LITTLE INFRASTRUCTURE REQUIREMENTS There are an estimated 14 billion bulbs in the world today. Since Li-Fi can operate on conventional LEDs infrastructure is pretty much present already.

5.3 SIMPLE SYSTEM STRUCTURE A typical VLC system consists of an LED array, a photo receiver , a De/modulator pair.

5.4 PHYSICAL LAYER SECURITY VLC offer a high level security, optical signals allows secure data exchanging.

5.5 IMMUNE TO ELECTROMAGNETIC INTERFERENCE (EMI) VLC depends on light for communication, no Electromagnetic Waves is used. So VLC is highly immune to Electromagnetic Interference. Due to this VLC can be used in areas where radio waves are restricted. This finds wide application of VLC. This is an important advantage which makes VLC to be used in Hospitals and Industries.

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CHAPTER 6 DISADVANTAGES 6.1 LINE OF SIGHT COMMUNICATION The greatest disadvantage of visible light communication is that it requires line of sight communication.

6.2 SHORT RANGE This technology usually works over a short distance range. To increase the transmission distance, the power of the lighting source must be increased. Image Sensor communication can be used in conjunction with telescope lenses to realize long distance ranges. Unfortunately, this range improvement leads to an appreciable increase in the implementation cost.

6.3 PRONE TO INTERFERENCE The VLC system is prone to interference from other illuminating devices. This disadvantage can be overcome to an extent by using advanced techniques.

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CHAPTER 7 APPLICATIONS 7.1 NETWORKING VLC is used in conjunction with PLC (Power Line Carrier Communications) to convert the illuminating sources in homes and offices into optical hotspots [8]. Thus, the users can enjoy high speed network access where the light sources are used to setup a wireless LAN. Thus, there are no bandwidth bottlenecks owing to the high bandwidth offered by VLC systems.

7.2 HIGH SPEED MULTIMEDIA STREAMING VLC supports a high bandwidth and can be used for transferring data at a very high rate. This makes VLC networks can be used for multimedia streaming, and for transferring files of huge size at a high speed.

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CHAPTER 8 CONCLUSION In this work a new VLC system architecture has been presented. This scheme performs data broadcast from a server in a cable network by means of visible optical links implemented using commercial LED lamps. A modified DPPM scheme has been also developed to ensure constant illumination intensity and constant bit rate. Therefore, these devices work simultaneously as communications systems and as illumination sources. Finally, an interface Ethernet-VLC prototype has been implemented. This could be easily used for conventional internet connections and applications.

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CHAPTER 9 REFERENCE [1] F. Delgado, I. Quintana, J. Rufo, J.A. Rabadan, Crisanto Quintana, and R. PerezJimenez “Design and Implementation of an Ethernet-VLC Interface for Broadcast Transmissions ” IEEE Communications Letters, vol. 14, no. 12, December 2010. [2] T. Komine and M. Nakagawa, “Integrated system of white LED visiblelight communication and power-line communication,” IEEE Trans. Consumer Electron., vol. 49, no. 1, Feb. 2003. [3] F. J. Lopez Hernandez, E. Poves, R. Perez-Jimenez, and J. Rabadan, “Low-cost diffuse wireless optical communication system based on white LED,” 2006 IEEE Tenth International Symposium on Consumer Electronics (ISCE’06). [4] http://visiblelightcomm.com/ [5] http://www.vlcc.net/ [6] http://en.wikipedia.org/ [7] EFY Magazine April 2012

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Design and Implementation of an Ethernet-VLC Interface for Broadcast Transmissions

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