Visible Light Communication Systems with low complexity

Topics: Modulation, MIMO, Light Pages: 37 (6672 words) Published: April 14, 2014
MIMO-OFDM VISIBLE LIGHT COMMUNICATION
SYSTEM WITH LOW COMPLEXITY

SUBJECT: MODERN SATELLITE COMMUNICATION
SUBJECT CODE: EEE 637

SUBMITTED BY,

M.TECH COMMUNICATION ENGINEERING
(2nd SEMESTER)

SCHOOL OF ELECTRONICS ENGINEERING (SENSE)
VELLORE INSTITUTE OF TECHNOLOGY
VELLORE, TAMIL NADU - 632014

ABSTRACT

Visible Light Communication (VLC) systems are being developed with the ultimate aim to create ultra-high-speed, high security, biologically friendly communications networks that allow the creation and expansion of seamless computing applications using very large bandwidth high-frequency pulsed light instead of radiowaves and microwaves. The most commonly used scheme for VLC is intensity modulation (IM) and direct detection (DD).

In VLC systems with intensity modulation (IM) and direct detection (DD), the modulation bandwidth of light emitting diode (LED) is limited, and the dispersion of the channel might cause ISI. Therefore most modulation schemes cannot be used directly for such a system. This project aims to show that a multiple-input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) VLC system overcomes the modulation bandwidth limitation of LED and satisfies the requirements of the transmitted signal for IM/DD. Two transmit data streams require only one inverse Fourier transform (IDFT) block, resulting in low computational complexity of the system. A MIMO system provides a significant improvement in capacity and data rates, compared with their single input output (SISO) counterparts, without any increase in bandwidth or transmit power. OFDM on the other hand is an effective technique when dealing with ISI.

TABLE OF CONTENTS
ABSTRACT
LIST OF FIGURES
1. INTRODUCTION

1

2. MIMO-OFDM

4

2.1. OFDM

4

2.1.1 Traditional view of Receiving signals carrying modulation

4

2.1.2 OFDM Spectrum

5

2.1.3 Advantages of OFDM

5

2.1.4 OFDM Transmission Scheme

5

2.2 MIMO

8

2.2.1 SPECIAL CASES

18

2.2.2 ADVANTAGES OF MIMO

10

2.2.2.1 SPATIAL MULTIPLEXING

11

2.2.2.2 SPATIAL DIVERSITY

12

1. RECEIVE DIVERSITY

12

2. TRANSMIT DIVERSITY

13

2.2.3 BEAMFORMING

3. VLC and IM/DD
3.1. Visible Light Communication
3.1.1 LED (Light Emitting Diode) VLC technology

3.2. Intensity Modulation with Direct Detection
4. SYSTEMS

13

15
15
15

17
19

4.1. MIMO VLC SYSTEMS

19

4.2. PNS MIMO OFDM SYSTEMS

19

4.3. RECEIVER

20

5. LITERATURE SURVEY

22

6. EXPECTED RESULTS & GRAPHS

24

7. FUTURE SCOPE

25

REFERENCE

26

BIODATA

27

LIST OF FIGURES

Fig 1: Multiple connectivity uses for VLC indoor

(02)

Fig 2.1: OFDM

(04)

Fig 2.2: OFDM Spectrum

(05)

Fig 2.3: Structrure and spectral characteristics of OFDM transmission system

(07)

Fig 2.4: 2 x 2 MIMO System

(09)

Fig 2.5: Spatial Multiplexing

(12)

Fig 2.6: Receive Diversity

(12)

Fig 2.7: Transmit Diversity

(13)

Fig 2.8: Beamforming

(14)

Fig 3.1: Visible Light Communication using LEDs

(16)

Fig 3.2: simplified block diagram of an optical intensity direct detection communication system.
(17)
Fig 4.1: Transmitter design of PNS MIMO-OFDM SYSTEM

(19)

Fig 4.2: Receiver Block Diagram

(20)

CHAPTER 1
INTRODUCTION
Most wireless communications today are based on various radio frequency waves generated, transmitted and received by electronic devices. WI-FI, 3G and Bluetooth are examples of this most wide technology. Radio frequency based systems are suffering from increasingly limited availability of conventional bandwidths for electronic equipment. Even the fastest of these radio frequency data transmission networks cannot compete with the potential of superior communication attributes provided by visible light transmission at higher speeds. The fastest networks today are equipped with lasers, fiber optic cabling network appliances and adaptive equipment. The next...


References: [2]. Yong Soo Cho, Jaekwon Kim, Won Young Yang, Chung Gu Kang, MIMO-OFDM
Wireless Communications with MATLAB, pp 111-150, 281-307, 2010.
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