A study on mobile ad hoc networks equipped with free-space optical capabilities.

A mobile ad hoc network (MANET) offers a cost-effective solution for communications in areas where infrastructure is unavailable, e.g. emergency response, disaster recovery, and battlefield scenarios. Traditional MANETs operate in the radio frequency (RF) spectrum, where the available bandwidth is facing the challenge of the rapidly increasing demands. Free-space optics (FSO) provides an attractive complement to RF wireless MANETs because of its high bandwidth and interference-free operation. An effort to combine the main advantages of MANET and FSO technologies by equipping the network nodes with hybrid communications capabilities will be presented. Computer models of such a network were created using the network simulator OPNET Modeler. Various indicators of network performance, including packet loss ratio, end-to-end delay, throughput, etc. were obtained through simulation and examined. The analysis will be of significant assistance in the design and implementation of such next-generation MANETs

Radio over fiber broadband access networks architectures based on wavelength division multiplexing techniques

The recent remarkable growth in bandwidth of both wired optical and wireless access networks supports a burst of new high bandwidth Internet applications such as: peer-topeer file sharing, cloud storage, on-line gaming, video streaming, etc. Within this scenario, the convergence of fixed and wireless access networks offers significant opportunities for network operators to satisfy user demands, and simultaneously reduce the cost of implementing and running separated wireless and wired networks. The integration of wired and wireless network can be accomplished within several scenarios and at several levels. In this thesis we will focus on converged radio over fiber architectures, particularly on two application scenarios: converged optical 60 GHz wireless networks and wireless overlay backhauling over bidirectional colorless wavelength division multiplexing passive optical networks (WDM-PONs). In the first application scenario, optical 60 GHz signal generation using external modulation of an optical carrier by means of lithium niobate (LiNbO3) Mach- Zehnder modulators (MZM) is considered. The performance of different optical modulation techniques, robust against fiber dispersion is assessed and dispersion mitigation strategies are identified. The study is extended to 60 GHz carriers digitally modulated with data and to systems employing subcarrier multiplexed (SCM) mm-wave channels. In the second application scenario, the performance of WDM-PONs employing reflective semiconductor optical amplifiers (RSOAs), transmitting an overlay orthogonal frequency-division multiplexing (OFDM) wireless signal is assessed analytically and experimentally, with the relevant system impairments being identified. It is demonstrated that the intermodulation due to the beating of the baseband signal and wireless signal at the receiver can seriously impair the wireless channel. Performance degradation of the wireless channel caused by the RSOA gain modulation owing to the downstream baseband data is also assessed, and system design guidelines are provided.Universidade do Algarve, Faculdade de Ciências e Tecnologi

Radio over fiber broadband access networks architectures based on wavelength division multiplexing techniques

The recent remarkable growth in bandwidth of both wired optical and wireless access networks supports a burst of new high bandwidth Internet applications such as: peer-topeer file sharing, cloud storage, on-line gaming, video streaming, etc. Within this scenario, the convergence of fixed and wireless access networks offers significant opportunities for network operators to satisfy user demands, and simultaneously reduce the cost of implementing and running separated wireless and wired networks. The integration of wired and wireless network can be accomplished within several scenarios and at several levels. In this thesis we will focus on converged radio over fiber architectures, particularly on two application scenarios: converged optical 60 GHz wireless networks and wireless overlay backhauling over bidirectional colorless wavelength division multiplexing passive optical networks (WDM-PONs). In the first application scenario, optical 60 GHz signal generation using external modulation of an optical carrier by means of lithium niobate (LiNbO3) Mach- Zehnder modulators (MZM) is considered. The performance of different optical modulation techniques, robust against fiber dispersion is assessed and dispersion mitigation strategies are identified. The study is extended to 60 GHz carriers digitally modulated with data and to systems employing subcarrier multiplexed (SCM) mm-wave channels. In the second application scenario, the performance of WDM-PONs employing reflective semiconductor optical amplifiers (RSOAs), transmitting an overlay orthogonal frequency-division multiplexing (OFDM) wireless signal is assessed analytically and experimentally, with the relevant system impairments being identified. It is demonstrated that the intermodulation due to the beating of the baseband signal and wireless signal at the receiver can seriously impair the wireless channel. Performance degradation of the wireless channel caused by the RSOA gain modulation owing to the downstream baseband data is also assessed, and system design guidelines are provided.Universidade do Algarve, Faculdade de Ciências e Tecnologi

HIGH-PERFORMANCE PERIODIC ANTENNAS WITH HIGH ASPECT RATIO VERTICAL FEATURES AND LARGE INTERCELL CAPACITANCES FOR MICROWAVE APPLICATIONS

Modern communications systems are evolving rapidly to address the demand for data exchange, a fact which imposes stringent requirements on the design process of their RF and antenna front-ends. The most crucial pressure on the antenna front-end is the need for miniaturized design solutions while maintaining the desired radiation performance. To satisfy this need, this thesis presents innovative types of periodic antennas, including electromagnetic bandgap (EBG) antennas, which are distinguished in two respects. First, the periodic cells contain thick metal traces, contrary to the conventional thin-trace cells. Second, such thick traces contain very narrow gaps with very tall sidewalls, referred to as high aspect ratio (HAR) gaps. When such cells are used in the structure of the proposed periodic antennas, the high capacitance of HAR gaps decreases the resonance frequency, mitigates conduction loss, and thus, yields considerably small high efficiency antennas. For instance, one of the sample antenna designs with only two EBG cells offers a very small XYZ volume of 0.25λ×0.28λ×0.037λ with efficiency of 83%. Also, a circularly polarized HAR EBG antenna is presented which has a footprint as small as 0.26λ×0.29λ and efficiency as high as 94%. The main analysis method developed in this thesis is a combination of numerical and mathematical analyses and is referred to as HFSS/Bloch method. The numerical part of this method is conducted using a High Frequency Structure Simulator (HFSS), and the mathematical part is based on the classic Bloch theory. The HFSS/Bloch method acts as the mainstay of the thesis and all designs are built upon the insight provided by this method. A circuit model using transmission line (TL) theory is also developed for some of the unit cells and antennas. The HFSS/Bloch perspective results in a HAR EBG TL with radiation properties, a fragment of which (2 to 6 cells) is introduced as a novel antenna, the self-excited EBG resonator antenna (SE-EBG-RA). Open (OC) and short circuited (SC) versions of this antenna are studied and the inherently smaller size of the SC version is demonstrated. Moreover, the possibility of employing the SE-EBG-RA as the element of a series-fed array structure is investigated and some sample high-efficiency, flat array antennas are rendered. A microstrip antenna is also developed, the structure of which is composed of 3×3 unit cells and shows fast-wave behaviors. Most antenna designs are resonant in nature; however, in one case, a low-profile efficient leaky-wave antenna with scanning radiation pattern is proposed. Several antenna prototypes are fabricated and tested to validate the analyses and designs. As the structures are based on tall metal traces, two relevant fabrication methods are considered, including CNC machining and deep X-ray lithography (DXRL). Hands-on experiments provide an outlook of possible future DXRL fabricated SE-EBG-RAs

Accelerating Network Functions using Reconfigurable Hardware. Design and Validation of High Throughput and Low Latency Network Functions at the Access Edge

Providing Internet access to billions of people worldwide is one of the main technical challenges in the current decade. The Internet access edge connects each residential and mobile subscriber to this network and ensures a certain Quality of Service (QoS). However, the implementation of access edge functionality challenges Internet service providers: First, a good QoS must be provided to the subscribers, for example, high throughput and low latency. Second, the quick rollout of new technologies and functionality demands flexible configuration and programming possibilities of the network components; for example, the support of novel, use-case-specific network protocols. The functionality scope of an Internet access edge requires the use of programming concepts, such as Network Functions Virtualization (NFV). The drawback of NFV-based network functions is a significantly lowered resource efficiency due to the execution as software, commonly resulting in a lowered QoS compared to rigid hardware solutions. The usage of programmable hardware accelerators, named NFV offloading, helps to improve the QoS and flexibility of network function implementations. In this thesis, we design network functions on programmable hardware to improve the QoS and flexibility. First, we introduce the host bypassing concept for improved integration of hardware accelerators in computer systems, for example, in 5G radio access networks. This novel concept bypasses the system’s main memory and enables direct connectivity between the accelerator and network interface card. Our evaluations show an improved throughput and significantly lowered latency jitter for the presented approach. Second, we analyze different programmable hardware technologies for hardware-accelerated Internet subscriber handling, including three P4-programmable platforms and FPGAs. Our results demonstrate that all approaches have excellent performance and are suitable for Internet access creation. We present a fully-fledged User Plane Function (UPF) designed upon these concepts and test it in an end-to-end 5G standalone network as part of this contribution. Third, we analyze and demonstrate the usability of Active Queue Management (AQM) algorithms on programmable hardware as an expansion to the access edge. We show the feasibility of the CoDel AQM algorithm and discuss the challenges and constraints to be considered when limited hardware is used. The results show significant improvements in the QoS when the AQM algorithm is deployed on hardware. Last, we focus on network function benchmarking, which is crucial for understanding the behavior of implementations and their optimization, e.g., Internet access creation. For this, we introduce the load generation and measurement framework P4STA, benefiting from flexible software-based load generation and hardware-assisted measuring. Utilizing programmable network switches, we achieve a nanosecond time accuracy while generating test loads up to the available Ethernet link speed

Análisis comparativo del desempeño de receptores ópticos coherentes y no coherentes para GFDM en redes PON.

El objetivo fue analizar el desempeño de una transmisión GFDM utilizando receptores ópticos coherentes y no- coherentes, para lo cual se realizó una transmisión de una señal de radio frecuencia sobre fibra usando la señal GFDM sobre una red óptica pasiva (PON) a 10 Gb/s por medio de una cosimulación OptSim –Matlab. La necesidad de mejorar el rendimiento de las futuras redes 5G implicará que el enlace de fronthaul sea un enlace de alta velocidad implementado sobre fibra óptica, para garantizar los requerimientos de la nueva generación de la red móvil. Con el fin de satisfacer tasas de datos de usuario superiores a 10 Gb/s, con una latencia menor a 1ms, uno de los candidatos principales es el esquema multiportadora GFDM como forma de onda para 5G. El desafío es aumentar la capacidad del enlace frontahaul el cual depende de la combinación de: el tipo de detección óptica que se emplee, los formatos de modulación y post-procesamiento digital de la señal. Además, una buena opción para el esquema de transmisión a ser empleado es la transmisión coherente, dado que esta aumenta sustancialmente la capacidad del rendimiento de una red óptica a comparación de los esquemas basados en modulación de intensidad con detección directa. Los resultados obtenidos demuestran una mejora apreciable en la sensibilidad del receptor (alrededor de 3 dB) empleando un detector coherente. Dentro de esta perspectiva se avizora que la detección coherente permitirá incrementar la capacidad de las redes ópticas fronthaul. Sin embargo, una desventaja importante de la transmisión coherente es su alto costo de implementación. Adicionalmente se podría realizar estudios de pre-compensación y post-compensación de la dispersión introducida en la señal por la propagación de la misma en la fibra óptica.The objective was to analyse the performance of GFDM transmission using coherent and noncoherent optical receivers, for which a transmission of a radio frequency signal over fiber was made using GFDM signal on a passive optical network (PON) at 10 Gb/s through an OptSim-Matlab cosimulation. The need to improve the performance of future 5G networks will mean that the fronthaul will be a high-speed link implemented over an optical fiber, to guarantee the requirements of the new generation mobile network. In order to satisfy user data rates higher than 10 Gb/s, with a latency less than 1 ms, one of the main candidates is the GFDM multi-carrier scheme as a 5G waveform. The challenge is to increase the fronthaul link capacity which depends on the combination of: the type of optical detection that is used, the modulation formats and digital post-processing of the signal. In addition, a good option for the transmission scheme to be used is the coherent transmission, because this substantially increases the performance capacity of an optical network compared to schemes based on intensity modulation and direct detection. The results obtained show an appreciable improvement in the receiver sensitivity (around 3 dB) using a coherent detector. Within this perspective it is envisioned that the coherent detection will allow to increase the capacity of the fronthaul optical networks. However, an important disadvantage of the coherent transmission is its high implementation cost. Additionally, dispersion pre-compensation and post-compensation studies could be carried out introduced in the signal by the propagation of its in the optical fiber

Análisis comparativo del desempeño de receptores ópticos coherentes y no coherentes para GFDM en redes PON.

El objetivo fue analizar el desempeño de una transmisión GFDM utilizando receptores ópticos coherentes y no- coherentes, para lo cual se realizó una transmisión de una señal de radio frecuencia sobre fibra usando la señal GFDM sobre una red óptica pasiva (PON) a 10 Gb/s por medio de una cosimulación OptSim –Matlab. La necesidad de mejorar el rendimiento de las futuras redes 5G implicará que el enlace de fronthaul sea un enlace de alta velocidad implementado sobre fibra óptica, para garantizar los requerimientos de la nueva generación de la red móvil. Con el fin de satisfacer tasas de datos de usuario superiores a 10 Gb/s, con una latencia menor a 1ms, uno de los candidatos principales es el esquema multiportadora GFDM como forma de onda para 5G. El desafío es aumentar la capacidad del enlace frontahaul el cual depende de la combinación de: el tipo de detección óptica que se emplee, los formatos de modulación y post-procesamiento digital de la señal. Además, una buena opción para el esquema de transmisión a ser empleado es la transmisión coherente, dado que esta aumenta sustancialmente la capacidad del rendimiento de una red óptica a comparación de los esquemas basados en modulación de intensidad con detección directa. Los resultados obtenidos demuestran una mejora apreciable en la sensibilidad del receptor (alrededor de 3 dB) empleando un detector coherente. Dentro de esta perspectiva se avizora que la detección coherente permitirá incrementar la capacidad de las redes ópticas fronthaul. Sin embargo, una desventaja importante de la transmisión coherente es su alto costo de implementación. Adicionalmente se podría realizar estudios de pre-compensación y post-compensación de la dispersión introducida en la señal por la propagación de la misma en la fibra óptica.The objective was to analyse the performance of GFDM transmission using coherent and noncoherent optical receivers, for which a transmission of a radio frequency signal over fiber was made using GFDM signal on a passive optical network (PON) at 10 Gb/s through an OptSim-Matlab cosimulation. The need to improve the performance of future 5G networks will mean that the fronthaul will be a high-speed link implemented over an optical fiber, to guarantee the requirements of the new generation mobile network. In order to satisfy user data rates higher than 10 Gb/s, with a latency less than 1 ms, one of the main candidates is the GFDM multi-carrier scheme as a 5G waveform. The challenge is to increase the fronthaul link capacity which depends on the combination of: the type of optical detection that is used, the modulation formats and digital post-processing of the signal. In addition, a good option for the transmission scheme to be used is the coherent transmission, because this substantially increases the performance capacity of an optical network compared to schemes based on intensity modulation and direct detection. The results obtained show an appreciable improvement in the receiver sensitivity (around 3 dB) using a coherent detector. Within this perspective it is envisioned that the coherent detection will allow to increase the capacity of the fronthaul optical networks. However, an important disadvantage of the coherent transmission is its high implementation cost. Additionally, dispersion pre-compensation and post-compensation studies could be carried out introduced in the signal by the propagation of its in the optical fiber

5G innovation opportunities-- A discussion paper

On the shaping of 5G technologies and networks, scope for wider service and applications innovation and UK strengths and opportunities