Over the recent few years, optical wireless communication (OWC) has attracted significant attention in both academia and the research community. Contrary to radio frequency (RF) systems, the spatial confinement of the optical beams makes the OWC system a potential system offering higher data rates and secured communication. OWC systems and applications in several areas, such as terrestrial outdoor (free-space optical (FSO) communication), indoor and outdoor visible light communication (VLC), etc. For the terrestrial outdoor FSO systems, spatial diversity techniques are employed over FSO links to enhance the diversity and overall performance. To this end, the spatial diversity techniques corresponding to the state-of-the-art are repetition coding (RC), transmit laser selection (TLS), and orthogonal space-time block codes. Note that, TLS is the optimal transmission scheme in the FSO systems. In this dissertation, we name the conventional TLS scheme as a single TLS (STLS) scheme. However, the performance of the conventional STLS scheme is highly dependent on the feedback errors. On the other side, the outdoor VLC finds applications in vehicle-to-vehicle (V2V) communications, infrastructure-to-vehicle (I2V) communications, etc. Emphasizing the state-of-the-art corresponding to the outdoor V2V-VLC systems, there is a lack of comprehensive modeling and performance investigation under the adverse challenges of the outdoor VLC environment. Moreover, to address the challenges of the next-generation-based outdoor intelligent transportation systems (ITSs), an indoor testbed design for an outdoor I2V-VLC system is still missing.
In order to enhance the diversity and overall performance of the terrestrial outdoor FSO systems, the study begins by proposing two novel TLS schemes. We call the proposed schemes as two TLS (TTLS) and modified error-tolerant weighting scheme (METWS). Note that, the conventional STLS scheme gives optimal performance under a perfect feedback scenario. However, its performance degrades significantly under an imperfect feedback scenario. To this end, the two proposed schemes overcome the practical limitations of the conventional STLS scheme. Moreover, we analyze the performance of the two proposed schemes for both perfect and imperfect channel state information (CSI)-based communication scenarios. Further, different performance metrics, such as bit error rate (BER), diversity gain, etc., are thoroughly analyzed. Furthermore, to gain more insight
Table of Contents
1 Introduction
1.1 Free-Space Optical Communication System
1.1.1 Advantages
1.1.2 Applications
1.1.3 Limitations
1.2 Visible Light Communication System
1.2.1 Advantages
1.2.2 Applications
1.2.3 Limitations
1.2.4 V2V Communication
1.2.5 I2V communication and V2I communication
1.3 Literature Review (Diversity Techniques in FSO Systems)
1.3.1 State-of-the-Art
1.3.2 Motivation and Proposed Diversity Improving Techniques
1.4 Literature Review (Indoor and Outdoor VLC)
1.4.1 State-of-the-Art (Indoor VLC)
1.4.2 State-of-the-Art (Modeling of Outdoor V2V-VLC)
1.4.3 State-of-the-Art (Recent Research on Outdoor V2V-VLC)
1.4.4 State-of-the-Art (Experimental Research on Outdoor V2V-VLC and I2V-VLC)
1.4.5 Motivation
1.5 Key Contributions
1.6 Organization of Thesis
2 Clustering-Based TLS Schemes for a Terrestrial Outdoor FSO System
2.1 Introduction
2.2 Preliminaries
2.2.1 System Model
2.2.2 Channel Model
2.2.3 Detection
2.3 Different Transmission Schemes with Generalized Weight Vector Structure
2.4 Performance Investigation of TTLS Scheme
2.4.1 Performance Investigation of TTLS Scheme with Perfect Feedback
2.4.2 Performance Investigation of TTLS Scheme with Erroneous Feedback
2.4.3 Diversity Order Investigation of TTLS Scheme
2.5 Performance Investigation of METWS
2.6 Results and Discussion
2.6.1 Performance of the Proposed Schemes over Negative Exponential Channel Model
2.6.2 Simulation-Based Results of the Proposed Schemes over G-G and LN Channel Models
2.6.3 Extension of the Proposed Schemes to MIMO-FSO Scenario
2.7 Conclusions
3 Diversity-Multiplexing Tradeoff for OWC Systems
3.1 Introduction
3.2 Indoor VLC System
3.3 DMT Analysis of Indoor VLC System
3.3.1 Outage Probability and DMT Analysis for SISO-VLC System
3.3.2 Outage Probability and DMT Analysis for MIMO-VLC System
3.4 Outdoor FSO System
3.4.1 Channel Models
3.4.2 Fundamental Definitions
3.5 DMT Analysis of Outdoor FSO System
3.5.1 Single-Rate Transmission
3.5.2 Adaptive-Rate Transmission
3.6 Results And Discussion
3.6.1 DMT of Indoor VLC System
3.6.2 DMT of Outdoor FSO System
3.7 Conclusions
4 Modeling of Outdoor V2V-VLC System Under Dynamic Scenarios
4.1 Introduction
4.2 Preliminaries
4.2.1 System Model
4.2.2 Channel Model and Detection
4.3 Performance Metrics Under Scenario 1
4.3.1 Average Path Loss
4.3.2 Outage Probability
4.3.3 ABER
4.3.4 Diversity Order
4.4 Performance Metrics Under Scenario 2
4.4.1 Average Path Loss
4.4.2 Outage Probability
4.4.3 ABER and Diversity Order
4.5 Average Path Loss and DCMC Capacity under Practical Outdoor Propagation Characteristics
4.5.1 Average Path Loss for LOS V2V-VLC Scenario
4.5.2 Average Path Loss for NLOS V2V-VLC Scenario
4.5.3 Mutual Information and DCMC Capacity
4.6 Results and Discussion
4.6.1 Effect of Path Loss
4.6.2 Outage Performance
4.6.3 ABER and Diversity Performance
4.6.4 Path Loss and DCMC Capacity Considering the Outdoor Propagation Characteristics of Table 4.2
4.7 Conclusions
5 Modeling of Outdoor V2V-VLC System Under Shadowing
5.1 Introduction
5.2 Preliminaries
5.2.1 Proposed V2V-VLC System Model under Shadowing and AT
5.2.2 Channel Model
5.2.3 Noise Model
5.2.4 Proposed Rx Structure and Effect of Ambient Noise
5.3 Average Path Loss Calculations
5.4 Formulation of the Optimization Problem and DMT Analysis of the V2V-VLC System under Shadowing and AT
5.5 Results and Discussion
5.5.1 Path Loss Performance
5.5.2 Outage Performance
5.5.3 DMT Performance
5.6 Conclusions
6 An Indoor Testbed Design for an Outdoor I2V-VLC System and Experimental Demonstration
6.1 Introduction
6.2 Preliminaries
6.2.1 Proposed I2V-VLC System
6.2.2 Normalized Beam Profile and Channel Modeling
6.2.3 Fundamental Definitions
6.3 Indoor I2V-VLC Testbed Design Approach and Experimental Lab Setup
6.3.1 Tx and Rx
6.3.2 Experimental Setup
6.4 Experimental Results and Analysis
6.4.1 BER without AT
6.4.2 BER with AT
6.4.3 PSNR Results
6.4.4 Capacity Results
6.4.5 Impact of LOS Blockage
6.5 Conclusions
7 Conclusions and Future Works
7.1 Conclusions
7.2 Future Scope of Work
Research Objectives and Topics
This dissertation investigates the design and performance of Optical Wireless Communication (OWC) systems across diverse indoor and outdoor scenarios, focusing specifically on Visible Light Communication (VLC) and Free-Space Optical (FSO) communication. The work addresses critical connectivity challenges in the context of Intelligent Transportation Systems (ITS) and terrestrial outdoor environments by developing robust channel models, innovative diversity schemes, and experimental validation testbeds to achieve reliable, high-speed data transmission.
- Clustering-based Transmit Laser Selection (TLS) schemes for terrestrial outdoor FSO systems.
- Diversity-Multiplexing Tradeoff (DMT) analysis for both indoor VLC and outdoor FSO systems.
- Comprehensive modeling of outdoor Vehicle-to-Vehicle (V2V) VLC systems affected by dynamic scenarios and shadowing.
- Design and experimental demonstration of an indoor testbed for outdoor Infrastructure-to-Vehicle (I2V) VLC communication.
- Enhancement of system performance through novel receiver structures and advanced signal processing techniques.
Excerpt from the Book
1. Introduction
With the growing increase in the number of users, the bandwidth requirement in wireless communication is also increasing exponentially. To this end, optical wireless communication (OWC) technology has emerged as a promising technology. OWC corresponds to the transmission of the optical signal in an unguided propagation medium such as the atmosphere, water, and vacuum [1]. Moreover, OWC offers unique features such as (i) High bandwidth, (ii) Unlicensed spectrum, (iii) Ease of deployment, (iv) Small size (≈ 1/10 the diameter of RF antenna), (v) Easy installation, (vi) Improved security, etc. Due to the availability of huge bandwidth, OWC technology is capable of supporting data rates up to 10 Gbps offering voice and video communication through the atmosphere/free-space. Nowadays, OWC is one of the most promising fields of research with the potential for impactful results, which will eventually bring revolution in the wireless market.
Summary of Chapters
Chapter 1: Provides a foundational overview of Optical Wireless Communication (OWC), covering Free-Space Optical (FSO) and Visible Light Communication (VLC) systems, their advantages, and motivation for the research.
Chapter 2: Introduces clustering-based Transmit Laser Selection (TLS) schemes, specifically TTLS and METWS, proposed to enhance the diversity and performance of terrestrial outdoor FSO systems.
Chapter 3: Analyzes the Diversity-Multiplexing Tradeoff (DMT) for indoor VLC and outdoor FSO systems, deriving optimal analytical expressions under various transmission scenarios.
Chapter 4: Formulates a detailed modeling of outdoor V2V-VLC systems, incorporating random vehicle mobility, path loss, and dynamic environmental challenges.
Chapter 5: Develops a comprehensive V2V-VLC model under shadowing and atmospheric turbulence, proposing a hemispherical optical concentrator-based receiver to optimize performance.
Chapter 6: Details the design and experimental validation of an indoor testbed for outdoor I2V-VLC systems, demonstrating the feasibility of the proposed solutions.
Chapter 7: Concludes the thesis by summarizing key research findings and outlining potential avenues for future investigative work.
Keywords
Optical Wireless Communication, Visible Light Communication, Free-Space Optical, Diversity-Multiplexing Tradeoff, V2V-VLC, I2V-VLC, Path Loss, Outage Probability, Atmospheric Turbulence, Shadowing, Transmit Laser Selection, MIMO, ITS, Performance Analysis, Testbed Design
Frequently Asked Questions
What is the core focus of this research?
The work focuses on investigating, modeling, and improving the design and performance of Optical Wireless Communication (OWC) systems, specifically targeting VLC and FSO applications in indoor and outdoor settings.
What are the primary fields of application?
The main applications include vehicular communication systems (V2V, I2V, V2I), Intelligent Transportation Systems (ITS), and terrestrial high-speed outdoor wireless links.
What is the overarching goal of the study?
The primary goal is to enhance data rates, reliability, and link performance of OWC systems by addressing practical challenges like atmospheric turbulence, shadowing, mobility, and fading.
Which scientific methodology is employed?
The research uses a multi-faceted approach involving analytical modeling, derivation of performance metrics (like BER, outage probability, and capacity), simulation-based validation, and experimental demonstration via a physical laboratory testbed.
What are the main components explored in the outdoor vehicle scenarios?
The study covers the effects of random mobility, path loss, road surface reflections, line-of-sight (LOS) blockage, and severe weather conditions on V2V communication performance.
What sets this work apart regarding receiver designs?
The author proposes novel hemispherical optical concentrator-based receiver structures to provide omnidirectional gain, significantly improving performance compared to conventional SPAD-based receivers.
How does the research address the complexity of feedback in FSO systems?
It proposes clustering-based TLS schemes (TTLS and METWS) that effectively manage limited and erroneous feedback, ensuring robust performance even in non-ideal channel states.
What is the significance of the experimental I2V-VLC testbed?
It offers a practical, real-world validation of outdoor I2V scenarios in a controlled laboratory environment, allowing for the comprehensive assessment of BER, PSNR, and capacity metrics with actual LED transmitters and high-speed cameras.
- Arbeit zitieren
- Pranav Sharda (Autor:in), 2023, Design and Performance Investigation of Optical Wireless Communication Systems in Indoor and Outdoor Scenarios, München, GRIN Verlag, https://www.grin.com/document/1477216
