66 research outputs found

    FFT size optimization for LTE RoF in nonlinear fibre propagation

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    This papers investigates the performance of the fast Fourier transform (FFT) sizes- 64, 128, 256, 512 and 1024 for the orthogonal frequency division multiplexing (OFDM) scheme in 3 rd generation partnership program (3GPP)-long term evolution (LTE) and LTE-Advanced (LTE-A). This paper aims to optimize the FFT sizes with respect to quadrature phase shift keying (QPSK), 16, 64 and 256-quadrature amplitude modulation (QAM). This optimization is for the transmission of LTE signals between eNodeB (eNB) and relay node (RN) to extend the mobile coverage employing radio-over-fibre (RoF). This paper will take into account the positive frequency chirp (PFC) induced by distributed feedback laser (DFB) through direct modulation with chromatic dispersion (CD) and self phase modulation (SPM) impairments into consideration. We present the optimum optical launch power (OLP) region termed as the intermixing region between linear and nonlinear optical fibre propagation. The optimum OLP in this investigation takes place at -4 dBm which falls within the intermixing region. At the transmission rate of 200, 400, 600 and 800 Mb/s of QPSK, 16, 64 and 256-QAM, the FFT size-128 provides the optimum power penalty with average system efficiency with respect to FFT size-64 is 54% and FFT size-256 is 65%

    The Experimental Design of Radio-over-Fibre System for 4G Long Term Evolution

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    The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is the potential key to meet the exponentially increasing demand of the mobile end users. The entire LTE network architecture and signal processing is carried out at the enhanced NodeB (eNB) level, hence the increased complexity and cost. Therefore, it is not efficient to deploy eNB for the purpose of extending the network coverage. As a solution, deployment of relay node (RN), with radio-over-fibre (RoF) acting as the interface between eNB and RN is proposed. Due to the high path loss and multipath fading, wireless interface would not be the ideal channel between eNB and RN. A detailed investigation is carried out by comparing the Rayleigh multipath fading channel with the optical fibre channel, where the latter achieved a ~31 dB of signal-to-noise ratio (SNR) gain. The distributed feedback laser (DFB) is selected as the direct modulated laser (DML) source, where the modulation method introduces a positive frequency chirp (PFC). The existing mathematical expression does not precisely explain on how the rate equations contribute to PFC. Therefore, an expression for PFC is proposed and derived from the carrier and photon densities of the rate equations. Focusing on theoretical development of DML based RoF system, a varying fast Fourier transform (FFT) scheme is introduced into LTE-Advanced (LTE-A) technology as an alternative design to the carrier aggregation. A range of FFT sizes are investigated with different levels of optical launch power (OLP), the optimum OLP has been defined to be within the range of ~-6 to 0 dBm, which is known as the intermixing region. It is found that FFT size-128 provides improved average system efficiency of ~54% and ~65% in comparison to FFT size-64 and FFT size-128, respectively, within the intermixing region. While fixing FFT size to 128, the investigation is diverted to the optimisation of optical modulators. The author revealed that the performance of dual electrode-Mach Zehnder modulator (DE-MZM) is superior to both DML scheme and single electrode (SE)-MZM, where DE-MZM achieved a transmission span of 88 km and 71 km for 16-quadrature amplitude modulation (QAM) and 64-QAM, respectively. At the initial experimental link design and optimisation stage, an optimum modulation region (OMR) is proposed at the optical modulation index (OMI) of 0.38, which resulted in an average error vector magnitude (EVM) of ~1.01% for a 10 km span. The EVM of ~1.01% is further improved by introducing the optimum OLP region at –2 dBm, where the observed average EVM trimmed to ~0.96%. There is no deviation found in the intermixing region by transmitting the LTE signal through a varying transmission span of 10 to 60 km, additionally, it was also revealed that the LTE RoF nonlinear threshold falls above the OLP of 6 dBm. The proposed system was further developed to accommodate 2×2 multiple-input and multiple-output (MIMO) transmission by utilising analogue frequency division multiplexing (FDM) technique. The studies procured that the resulting output quality of signal at 2 GHz and 2.6 GHz is almost identical with a twofold gain in the peak data rate and no occurrence of intermodulation (IMD). In order to emulate the complete LTE RoF solution, an experimental design of full duplex frequency division duplex (FDD) system with dense wavelength division multiplexing (DWDM) architecture is proposed. It is found that channel spacing of 50 MHz between the downlink (DL) and uplink (UL) introduces severe IMD distortion, where an adjacent channel leakage ratio (ACLR) penalty of 14.10 dB is observed. Finally, a novel nonlinear compensation technique utilising a direct modulation based frequency dithering (DMFD) scheme is proposed. The LTE RoF system average SNR gain observed at OLP of 10 dBm for the 50 km transmission span is ~5.97 dB. External modulation based frequency dithering (EMFD) exhibits ~3 dB of average SNR gain over DMFD method

    Theoretical and experimental design of an alternative system to 2 x 2 MIMO for LTE over 60 km directly modulated RoF link

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    Relay nodes (RN) are used as an important structure to extend the coverage of the Third Generation Partnership Program’s Long Term Evolution (3GPP-LTE). The promising technology as the interface between eNodeB (eNB) and RN is radio-over-fibre (RoF), due to its longer span transmission capability. In this paper, we propose an alternative technique to 2×2 multiple-input and multiple-output (MIMO) in LTE structure for transmission over 60 km directly modulated RoF link by introducing frequency division multiplexing (FDM) for orthogonal FDM (OFDM). The system is demonstrated theoretically and experimentally. In the baseband, quadrature phase shift keying (QPSK), 16-quadrature amplitude modulation (QAM) and 64-QAM are considered as the single carrier modulations (SCM) according to the LTE standard. The system degradation pattern is identical between the theoretical and experimental system, thus proving the accuracy of the theoretical system design. The real time QPSK, 16-QAM and 64-QAM system achieved an average EVM of 5.84%, 5.90% and 5.97%, respectively for 2 GHz and 2.6 GHz bands. These resultant EVMs are below the 8% 3GPP-LTE EVM requirement

    Millimetre-Wave Fibre-Wireless Technologies for 5G Mobile Fronthaul

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    The unprecedented growth in mobile data traffic, driven primarily by bandwidth rich applications and high definition video is accelerating the development of fifth generation (5G) mobile network. As mobile access network evolves towards centralisation, mobile fronthaul (MFH) architecture becomes essential in providing high capacity, ubiquitous and yet affordable services to subscribers. In order to meet the demand for high data rates in the access, Millimetre-wave (mmWave) has been highlighted as an essential technology in the development of 5G-new radio (5G-NR). In the present MFH architecture which is typically based on common public radio interface (CPRI) protocol, baseband signals are digitised before fibre transmission, featuring high overhead data and stringent synchronisation requirements. A direct application of mmWave 5G-NR to CPRI digital MFH, where signal bandwidth is expected to be up to 1GHz will be challenging, due to the increased complexity of the digitising interface and huge overhead data that will be required for such bandwidth. Alternatively, radio over fibre (RoF) technique can be employed in the transportation of mmWave wireless signals via the MFH link, thereby avoiding the expensive digitisation interface and excessive overhead associated with its implementation. Additionally, mmWave carrier can be realised with the aid of photonic components employed in the RoF link, further reducing the system complexity. However, noise and nonlinearities inherent to analog transmission presents implementation challenges, limiting the system dynamic range. Therefore, it is important to investigate the effects of these impairments in RoF based MFH architecture. This thesis presents extensive research on the impact of noise and nonlinearities on 5G candidate waveforms, in mmWave 5G fibre wireless MFH. Besides orthogonal frequency division multiplexing (OFDM), another radio access technology (RAT) that has received significant attention is filter bank multicarrier (FBMC), particularly due to its high spectral containment and excellent performance in asynchronous transmission. Hence, FBMC waveform is adopted in this work to study the impact of noise and nonlinearities on the mmWave fibre-wireless MFH architecture. Since OFDM is widely deployed and it has been adopted for 5G-NR, the performance of OFDM and FBMC based 5G mmWave RAT in fibre wireless MFH architecture is compared for several implementations and transmission scenarios. To this extent, an end to end transmission testbed is designed and implemented using industry standard VPI Transmission Maker® to investigate five mmWave upconversion techniques. Simulation results show that the impact of noise is higher in FBMC when the signal to-noise (SNR) is low, however, FBMC exhibits better performance compared to OFDM as the SNR improved. More importantly, an evaluation of the contribution of each noise component to the overall system SNR is carried out. It is observed in the investigation that noise contribution from the optical carriers employed in the heterodyne upconversion of intermediate frequency (IF) signals to mmWave frequency dominate the system noise. An adaptive modulation technique is employed to optimise the system throughput based on the received SNR. The throughput of FBMC based system reduced significantly compared to OFDM, due to laser phase noise and chromatic dispersion (CD). Additionally, it is shown that by employing frequency domain averaging technique to enhance the channel estimation (CE), the throughput of FBMC is significantly increased and consequently, a comparable performance is obtained for both waveforms. Furthermore, several coexistence scenarios for multi service transmission are studied, considering OFDM and FBMC based RATs to evaluate the impact inter band interference (IBI), due to power amplifier (PA) nonlinearity on the system performance. The low out of band (OOB) emission in FBMC plays an important role in minimising IBI to adjacent services. Therefore, FBMC requires less guardband in coexistence with multiple services in 5G fibre-wireless MFH. Conversely, OFDM introduced significant OOB to adjacent services requiring large guardband in multi-service coexistence transmission scenario. Finally, a novel transmission scheme is proposed and investigated to simultaneously generate multiple mmWave signals using laser heterodyning mmWave upconversion technique. With appropriate IF and optical frequency plan, several mmWave signals can be realised. Simulation results demonstrate successful simultaneous realisation of 28GHz, 38GHz, and 60GHz mmWave signals

    Development of a dc-ac power conditioner for wind generator by using neural network

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    This project present of development single phase DC-AC converter for wind generator application. The mathematical model of the wind generator and Artificial Neural Network control for DC-AC converter is derived. The controller is designed to stabilize the output voltage of DC-AC converter. To verify the effectiveness of the proposal controller, both simulation and experimental are developed. The simulation and experimental result show that the amplitude of output voltage of the DC-AC converter can be controlled

    包絡線パルス幅変調によるOFDM信号の光ファイバ無線伝送に関する研究

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    In this thesis, an Envelop Pulse-Width Modulation-RoF (EPWM-RoF) transmission scheme is proposed to solve the RoF nonlinearity and echo effect issues. Through the theoretical analysis, simulation and experimental results, it can be concluded that EPWM-RoF transmission is effective in dealing with E/O nonlinearity and echo effect in RoF channel.電気通信大学201

    Hybrid optical fiber-wireless communication to support tactile internet

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    5G technologies are systems that will set to change the way people, devices and machines connect. This generation of mobile services provide connection in just one click. The advanced 5G infrastructure, defined as “ubiquitous ultra-broadband network supporting future Internet”, represents a revolution in the telecommunications field. It will enable new secure and reliable services to everyone and everything with ultra-low latency. “Full Immersive Experience”, enriched by “Context Information” and “Anything as a Service” are the main drivers for a substantial adoption of the fifth generation networks [1]. The technical challenges that must be taken into account in the design of the 5G system are many and unprecedented. Therefore,5G is expected to be about 10 times faster than LTE-4G, in addition, it is projected that this network will have100-1000 times higher system capacity, user data rates in the order of Gbps everywhere, 10-100 higher number of connected devices per area, latency in the order of 1 millisecond, and 10 times longer battery life for devices. Due to all these technological changes, for years, researchers, suppliers and manufacturers around the world have studied this new network. In order to transform the user's wireless experience and be able to offer fast generalized connectivity anytime, anywhere, to any device.[2]. All this requires an enabler in the new approach of radio access networks, which could be hybrid optical Fiber-Wireless communications. “Photonics technology has been recognized by the European Union as a Key Enabling Technology (KET), which is a technology that enables a market, many times larger than the market of technology itself”. Photonic techniques have become key enablers to unlock future broadband wireless communications with terabit data rates in order to support the current trends of mobile data traffic[3]. The aim of this thesis is to conceive experimentally and validate 1 millisecond latency hybrid optical Fiber-Wireless access links support for tactile Internet taking into account the system requirements. For this purpose, first a review about the implementation of high-speed data links at 75-110 GHz band with low latency was made. Likewise, this work summarizes the components of hybrid optical Fiber-Wireless communication in W- Band. Second, measurements of the delay contribution from individual elements in the W -Band hybrid system were made. In addition, the main contribution was to develop a procedure for measuring latency physically using software defined radio (SDR) and estimating the overall system latency. In this procedure, potential sources of delay can be identified in current high-data-rate hybrid optical-RF communication systems. After knowing how to measure latency in a hybrid optical Fiber-Wireless system, the following objectives were developed: to test an appropriate multiplexing scheme such as Orthogonal Frequency Division Multiplexing (OFDM), and Generalized Frequency Division Multiplexing (GFDM), to achieve the lowest latency with improved performance; and to implement WDM (Wavelength Division Multiplexing) to achieve the required low latency.Resumen: Las tecnologías 5G son sistemas de generación de servicios móviles configurados para cambiar la forma en que las personas, los dispositivos y las máquinas se conectan. La infraestructura 5G está definida como una red ubicua de banda ultra-ancha que soportará Internet en el futuro, dicha red representa una revolución en el campo de las telecomunicaciones. Permitirá eficientemente nuevos servicios ultra-confiables, rápidos y seguros, preservando la privacidad y acelerando los servicios críticos para todos y para cada cosa. Estas redes son la evolución del Internet de las cosas, en donde cada una de ellas es tratada como un objeto cognitivo formando sistemas cibernéticos (CPS). La "experiencia de inmersión total", enriquecida con "información de contexto" y "todo como un servicio" son los principales impulsores para una adopción masiva de los nuevos componentes de ésta tecnología y su aceptación del mercado [1]. Se espera que 5G sea aproximadamente 10 veces más rápido que 4G LTE. Por lo tanto, los desafíos técnicos que deben abordarse en el diseño del sistema 5G son muchos y sin precedentes. Actualmente hay varias actividades en todo el mundo para capturar las aplicaciones y los requisitos para 5G, algunas empresas proveedoras de servicio y fabricantes incluso ya han realizado pruebas para la implementación de dichas redes. Algunos de los principales requisitos que demandan estas redes se pueden resumir en: 100-1000 veces más capacidad del sistema, tasas de datos de usuario en el orden de Gbps en todas partes, latencia en el orden de 1 milisegundo, 10-100 veces mayor número de dispositivos conectados por área, 10 veces más duración de la batería para dispositivos. Estos requisitos transformarán dramáticamente la experiencia inalámbrica de un usuario en un sistema 5G al ofrecer conectividad generalizada rápida en cualquier momento, en cualquier lugar, a cualquier dispositivo [2]. Todo esto requiere un habilitador en el nuevo enfoque de las redes de acceso por radio, que podrían ser comunicaciones híbridas de fibra óptica y transmisiones inalámbricas vía radio. La fotónica por su parte ha sido reconocida por la Unión Europea como una Tecnología Clave Habilitadora (KET), una tecnología que permite un mercado que es muchas veces más grande que el mercado de la tecnología en sí. Las técnicas fotónicas combinadas con la generación de microondas en lo que se conoce en su término en inglés como microwave-photonics se han convertido en habilitadores clave para desbloquear futuras comunicaciones inalámbricas de banda ancha con tasas de datos de terabit a fin de soportar las tendencias actuales del tráfico de datos móviles [3]. El objetivo de esta tesis es concebir experimentalmente y validar enlaces de acceso híbridos de fibra óptica-radio, cuya latencia sea de 1 milisegundo con el fin de soportar Internet táctil, el cual es una aplicación de 5G, teniendo en cuenta los requisitos del sistema. Para ello, primero se realizó una investigación sobre la implementación de enlaces de datos con redes híbridas fibra óptica-radio en la banda de 75-110 GHz con baja latencia. Con esto, se analizaron los componentes de la comunicación híbrida fibra ópticaradio en la banda W. En segundo lugar, se realizaron mediciones de los retardos que se generan en cada uno de los elementos en el sistema híbrido de banda W, haciendo la estimación de la latencia general del sistema e identificando fuentes potenciales de demora en los sistemas híbridos de comunicación óptica-RF de alta velocidad de datos. La principal contribución de este trabajo fue el desarrollo de un procedimiento para medir la latencia utilizando radio definida por software (SDR), además de introducir estos sistemas en los enlaces híbridos fibra óptica-radio. Una vez conocido como medir la latencia en un sistema híbrido de fibra óptica-radio, los siguientes objetivos que se desarrollaron fueron: probar un esquema de multiplexación apropiado, como la multiplexación por división de frecuencia ortogonal (OFDM) y la multiplexación por división de frecuencia generalizada (GFDM), para lograr una latencia más baja. A su vez, implementar Multiplexación por división de longitud de onda (WDM) para conocer la latencia y la confiabilidad en cuanto a tasa de error de bits variando la multiplexacion eléctrica y óptica.Doctorad

    Nonlinear impairments and mitigation technologies for the next generation fiber-wireless mobile fronthaul networks

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    The proliferation of Internet-connected mobile devices and video-intensive services are driving the growth of mobile data traffic in an explosive way. The last mile of access networks, mobile fronthaul (MFH) networks, have become the data rate bottleneck of user experience. The objective of this research are two-fold. For analog MFH, nonlinear interferences among multiple bands of mobile signals in a multi-RAT multi-service radio-over-fiber (RoF)-based MFH system are investigated for the first time. The nonlinear impairments of both single-carrier and multi-carrier signals are investigated, and it is experimentally demonstrated that inter-channel interferences play a more important role in the performance degradation of analog MFH than the nonlinear distortions of each individual signal. A digital predistortion technique was also presented to linearize the analog MFH links. On the other hand, for digital MFH, we experimentally demonstrate a novel digitization interface based on delta-sigma modulation to replace the state-of-the-art common public radio interface (CPRI). Compared with CPRI, it provides improved spectral efficiency and enhanced fronthaul capacity, and can accommodate both 4G-LTE and 5G mobile services.Ph.D
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