In communication networks today, the amount of users and traffic is constantly increasing. This results in the need for upgrading the networks to handle the demand. Free space optics is a technique which is relatively cheap with high capacity compared to most systems today. On the other hand, FSO have some disadvantages with the effects on the system by, for instance, turbulence and weather. The aim of the project is to investigate the use of network optimization for designing an optimal network in terms of capacity and cost. Routing optimization is also covered in terms of singlepath and multipath routing. To mitigate the problem with turbulence affecting the system network survivability is implemented with both proactive and reactive solutions. The method used is to implement the system in Matlab, the system should also be tested so that it works as intended. The report covers related work as well as theory behind FSO and the chosen optimization algorithms. The system uses modified Bellman-Ford optimization as well as Kruskal’s minimum spanning tree. K-link-connectivity is also implemented for the network survivability and multipath algorithm. Results of the implementation shows that the network survivability improves the robustness of the system by changing paths for traffic which is affected by broken links. Routing done by multipath will increase the throughput and also reduce the delay for the traffic.

In communication networks today, the amount of users and traffic is constantly increasing. This results in the need for upgrading the networks to handle the demand. Free space optics, FSO, is a technique which is relatively cheap with high capacity compared to most systems today. On the other hand, FSO have some disadvantages with the effects on the system by, for instance, turbulence and weather. The aim of the project is to investigate the use of network optimization for designing an optimal network in terms of capacity and cost. Routing optimization is also covered in terms of singlepath and multipath routing. To mitigate the problem with turbulence affecting the system network survivability is implemented with both proactive and reactive solutions. The method used is to implement the system in Matlab, the system should also be tested so that it works as intended. The report covers related work as well as theory behind FSO and the chosen optimization algorithms. The system uses modified Bellman-Ford optimization as well as Kruskal’s minimum spanning tree. K-link-connectivity is also implemented for the network survivability and multipath algorithm. Results of the implementation shows that the network survivability improves the robustness of the system by changing paths for traffic which is affected by broken links. Routing done by multipath will increase the throughput and also reduce the delay for the traffic.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / We investigate pulse position modulation (PPM) and multipulse PPM (MPPM) for free space op- tical channels using bit interleaved coded modulation with iterative decoding. Data bits are first encoded by using a non recursive convolutional code and the coded bits after an interleaver are modulated before transmission. Iterative decoding is performed at the receiver. Optimized mapping is designed for MPPM. A genetic algorithm is used to find the optimized mapping for MPPM. Our simulation results show that a significant improvement in the error performance can be achieved by using optimized mapping and iterative decoding at the receiver.

One of the potential solutions to the radio frequency (RF) spectrum scarcity problem is optical wireless communications (OWC), which utilizes the unlicensed optical spectrum. Long-range outdoor OWC are usually referred to in the literature as free-space optical (FSO) communications. Unlike RF systems, FSO is immune to interference and multi-path fading. Also, the deployment of FSO systems is flexible and much faster than optical fibers. These attractive features make FSO applicable for broadband wireless transmission such as optical fiber backup, metropolitan area network, and last mile access. Although FSO communication is a promising technology, it is negatively affected by two physical phenomenon, namely, scintillation due to atmospheric turbulence and pointing errors. These two critical issues have prompted intensive research in the last decade. To quantify the effect of these two factors on FSO system performance, we need effective mathematical models. In this work, we propose and study a generalized pointing error model based on the Beckmann distribution. Then, we aim to generalize the FSO channel model to span all turbulence conditions from weak to strong while taking pointing errors into consideration. Since scintillation in FSO is analogous to the fading phenomena in RF, diversity has been proposed too to overcome the effect of irradiance fluctuations. Thus, several combining techniques of not necessarily independent dual-branch free-space optical links were investigated over both weak and strong turbulence channels in the presence of pointing errors. On another front, improving the performance, enhancing the capacity and reducing the delay of the communication link has been the motivation of any newly developed schemes, especially for backhauling. Recently, there has been a growing interest in practical systems to integrate RF and FSO technologies to solve the last mile bottleneck. As such, we also study in this thesis asymmetric an RF-FSO dual-hop relay transmission system with both fixed and variable gain relay.

Os sistemas de comunicação óptica por espaço livre, comumente denominados sistemas FSO (Free Space Optics), servem para estabelecer enlaces de comunicação do tipo wireless, ponto-a-ponto, a uma elevada taxa de dados e com alcances que podem variar de algumas centenas de metros a alguns quilômetros. O interesse pela tecnologia FSO tem sido estimulado pela necessidade de se fornecer soluções complementares às tradicionais (e.g. fibra óptica e RF) visando a atender à crescente demanda por conexões de banda larga. Algumas de suas aplicações mais importantes são a conexão de redes locais de computadores, a conexão de estações rádio base de telefonia móvel às centrais e o acesso de última milha. Embora a tecnologia FSO venha sendo empregada em pequena escala no Brasil, vislumbra-se o potencial de maior aplicação desta tecnologia em um futuro próximo, razão pela qual se propõe este estudo, focado no projeto de sistemas FSO. A principal contribuição deste trabalho é demonstrar uma possível solução para a realização de um enlace óptico operando em espaço livre, destinado a conectar duas redes locais de computadores Ethernet Rápida (100 Mbps). As seguintes atividades foram desenvolvidas: estudo das questões mais relevantes pertinentes ao projeto de sistemas FSO; projeto, construção e caracterização eletro-óptica de circuitos; montagem e demonstração do funcionamento de uma versão de testes do sistema, realizadas em laboratório; estudo de características associadas à transferência de radiação óptica de transmissor para receptor, envolvendo o balanço de potência para estimativa do alcance do enlace, sob condições atmosféricas ideais. Como resultado, obtivemos um sistema de comunicação do tipo full-duplex, operando no comprimento de onda de 850 nm em formato de modulação OOK, a uma taxa de dados efetiva de 125 Mbps. Com base na experiência obtida, melhoras ao sistema são sugeridas no final do trabalho. / Free space optical communication systems (FSO systems) provide wireless, point-to-point communication links at high data rates, at maximum distances ranging from hundreds of meters to several kilometers. The growing interest in FSO technology arises from the necessity of providing complementary and alternative solutions to those already adopted (eg. fiber optics and RF), aiming to satisfy the increasing demand for broadband connections. Some of its most important applications are connecting local area networks (LANs), backhauling wireless networks and providing last mile access. Although today FSO is not widely adopted in Brazil, the technology has the potential for being adopted in a greater scale in the near future, which is the reason we propose a study focused on issues related to the design of FSO systems. This work\'s main contribution is to demonstrate a possible solution for the construction of a FSO system intended to connect two Fast Ethernet LANs (100 Mbps). For this purpose, the following activities were developed: study of the main aspects related to FSO system design; design, construction and electrooptical characterization of circuits; mounting and demonstration, in the lab, of a test version of the system; study of characteristics related to radiation transfer from transmitter to receiver, involving the use of the link power budget for an estimation of the maximum distance achievable under ideal atmospheric conditions. The result is a full-duplex communication system that employs the 850 nm wavelength in OOK modulation format, operating at an effective bit rate of 125 Mbps. Based on the knowledge achieved, improvements to the system are suggested at the end of this work.

Os sistemas de comunicação óptica por espaço livre, comumente denominados sistemas FSO (Free Space Optics), servem para estabelecer enlaces de comunicação do tipo wireless, ponto-a-ponto, a uma elevada taxa de dados e com alcances que podem variar de algumas centenas de metros a alguns quilômetros. O interesse pela tecnologia FSO tem sido estimulado pela necessidade de se fornecer soluções complementares às tradicionais (e.g. fibra óptica e RF) visando a atender à crescente demanda por conexões de banda larga. Algumas de suas aplicações mais importantes são a conexão de redes locais de computadores, a conexão de estações rádio base de telefonia móvel às centrais e o acesso de última milha. Embora a tecnologia FSO venha sendo empregada em pequena escala no Brasil, vislumbra-se o potencial de maior aplicação desta tecnologia em um futuro próximo, razão pela qual se propõe este estudo, focado no projeto de sistemas FSO. A principal contribuição deste trabalho é demonstrar uma possível solução para a realização de um enlace óptico operando em espaço livre, destinado a conectar duas redes locais de computadores Ethernet Rápida (100 Mbps). As seguintes atividades foram desenvolvidas: estudo das questões mais relevantes pertinentes ao projeto de sistemas FSO; projeto, construção e caracterização eletro-óptica de circuitos; montagem e demonstração do funcionamento de uma versão de testes do sistema, realizadas em laboratório; estudo de características associadas à transferência de radiação óptica de transmissor para receptor, envolvendo o balanço de potência para estimativa do alcance do enlace, sob condições atmosféricas ideais. Como resultado, obtivemos um sistema de comunicação do tipo full-duplex, operando no comprimento de onda de 850 nm em formato de modulação OOK, a uma taxa de dados efetiva de 125 Mbps. Com base na experiência obtida, melhoras ao sistema são sugeridas no final do trabalho. / Free space optical communication systems (FSO systems) provide wireless, point-to-point communication links at high data rates, at maximum distances ranging from hundreds of meters to several kilometers. The growing interest in FSO technology arises from the necessity of providing complementary and alternative solutions to those already adopted (eg. fiber optics and RF), aiming to satisfy the increasing demand for broadband connections. Some of its most important applications are connecting local area networks (LANs), backhauling wireless networks and providing last mile access. Although today FSO is not widely adopted in Brazil, the technology has the potential for being adopted in a greater scale in the near future, which is the reason we propose a study focused on issues related to the design of FSO systems. This work\'s main contribution is to demonstrate a possible solution for the construction of a FSO system intended to connect two Fast Ethernet LANs (100 Mbps). For this purpose, the following activities were developed: study of the main aspects related to FSO system design; design, construction and electrooptical characterization of circuits; mounting and demonstration, in the lab, of a test version of the system; study of characteristics related to radiation transfer from transmitter to receiver, involving the use of the link power budget for an estimation of the maximum distance achievable under ideal atmospheric conditions. The result is a full-duplex communication system that employs the 850 nm wavelength in OOK modulation format, operating at an effective bit rate of 125 Mbps. Based on the knowledge achieved, improvements to the system are suggested at the end of this work.

In this thesis, a fully millimetre-wave (mm-wave) generation and transmission system is proposed for futuristic communications. Significant challenges have been dealt with regarding the proposed system, including designing the mm-wave generation and transmission technique, and its application in cellular networks. These challenges are presented through five main contributions and validated via Optiwave Design Software and MATLAB simulation tools. Firstly, three novel photonic generation methods are proposed and designed based on the characteristics of Brillouin fibre laser and the Stimulated Brillouin Scattering (SBS) effects with phase modulation. The mm-wave carriers are successfully generated with a tuning capability from 5 to 90 GHz. Also, these carriers are with good Signal to Noise Ratio (SNR) up to 51 dB, and low noise signal power of about -40 dBm. The impact of these methods is obtaining stable mm-waves appropriate for Radio over Fibre (RoF) transmission systems in 5G optical networks. Secondly, a full-duplex RoF system with the generation of a 64 GHz mm-wave is proposed. Successful transmission of the mm-wave over a fibre link is achieved for up to 100 km of fibre with a data rate of 5 Gbits/s. The main impact of this system is cost reduction and performance improvement by simplifying mm-wave generation and transmission over fibre. Also, it ensures a useful communication link for small cell networks. Thirdly, a hybrid Fibre/Free-space optical (FSO) system for the generation and transmission of 64 GHz mm-wave is proposed. This optical system provides a low latency communication link and overcomes mm-wave high path losses. A successful mm-wave transmission is achieved over a 10 km fibre length, and 2 km FSO link length with a good Bit Error Rate (BER) of about 1.5×10-13 and a data rate of 10 Gbits/s. This system increases the network coverage area by transmitting the mm-wave over the FSO link to the areas with natural obstacles the laying of fibre cables impossible. Also, it can be used as an effective solution under emergency disaster conditions. Fourthly, a comprehensive study of the wireless propagation performance for different mm-wave bands (28, 60, and 73 GHz) as cellular networks is investigated and compared with the 2.4 GHz Ultra-High Frequency band (UHF). A map-based scenario is proposed for the deployment of Base Stations (BSs) within the Brunel University London Campus map to consider real blockage effects. This investigation involved specifying which mm-wave spectrum can enhance the futuristic cellular networks, by evaluating the coverage and rate trends. Comparative results show that the 73 GHz bands can achieve the higher rate with good coverage and the lowest interference effects than the other mm-wave bands. Finally, a simplified path loss model is proposed to estimate precisely the 28 GHz mm-wave performance, which is considered a key component in 5G networks in outdoor applications. The proposed path loss model captures the diffraction and specular reflection impacts on mm-wave wireless propagation.

Free Space Optics (FSO) has received a great deal of attention lately both in the military and civilian information society due to its potentially high capacity, rapid deployment, portability and high security from deception and jamming. The main issue is that severe weather can have a detrimental impact on the performance, which may result in an inadequate availability. This report contains a feasibility study for an all-optical free-space link intended for short-range communication (200-500 m). Laboratory tests have been performed to evaluate the link design. Field tests were made to investigate availability and error performance under the influence of different weather conditions. Atmospheric impact due to turbulence related effects have been studied in detail. The most crucial part of the link design turned out to be the receiver optics and several design solutions were investigated. The main advantage of an all-optical design, compared to commercially available electrooptical FSO-systems, is the potentially lower cost.

<p>Free Space Optics (FSO) has received a great deal of attention lately both in the military and civilian information society due to its potentially high capacity, rapid deployment, portability and high security from deception and jamming. The main issue is that severe weather can have a detrimental impact on the performance, which may result in an inadequate availability. </p><p>This report contains a feasibility study for an all-optical free-space link intended for short-range communication (200-500 m). Laboratory tests have been performed to evaluate the link design. Field tests were made to investigate availability and error performance under the influence of different weather conditions. Atmospheric impact due to turbulence related effects have been studied in detail. The most crucial part of the link design turned out to be the receiver optics and several design solutions were investigated. The main advantage of an all-optical design, compared to commercially available electrooptical FSO-systems, is the potentially lower cost.</p>

The exponential increase of mobile users and the demand for high-speed data services has resulted in significant congestions in cellular backhaul capacity. As a solution to satisfy the traffic requirements of the existing 4G network, the 5G network has emerged as an enabling technology and a fundamental building block of next-generation communication networks. An essential requirement in 5G backhaul networks is their unparalleled capacity to handle heavy traffic between a large number of devices and the core network. Microwave and optic fiber technologies have been considered as feasible solutions for next-generation backhaul networks. However, such technologies are not cost effective to deploy, especially for the backhaul in high-density urban or rugged areas, such as those surrounded by mountains and solid rocks. Additionally, microwave technology faces alarmingly challenging issues, including limited data rates, scarcity of licensed spectrum, advanced interference management, and rough weather conditions (i.e., rain, which is the main weather condition that affects microwave signals the most). The focus of this work is to investigate the feasibility of using free-space-optical (FSO) technology in the 5G cellular backhaul network. FSO is a cost-effective and wide-bandwidth solution as compared to traditional backhaul solutions. However, FSO links are sensitive to atmospheric turbulence-induced fading, path loss, and pointing errors. Increasing the reliability of FSO systems while still exploiting their high data rate communications is a key requirement in the deployment of an FSO backhaul network. Overall, the theoretical models proposed in this work will be shown to enhance FSO link performance. In the experimental direction, we begin by designing an integrated mobile FSO system. To the best of our knowledge, no work in the literature has addressed the atmospheric path loss characterization of mobile FSO channels in a coastal environment. Therefore, we investigate the impact of weather effects in Thuwal, Saudi Arabia, over FSO links using outdoor and indoor setups. For the indoor experiments, results are reported based on a glass climate chamber in which we could precisely control the temperature and humidity.