Radio over fiber: An alternative broadband network technology for Iot

Wireless broadband access networks have been positioning themselves as a good solution for manufacturers and users of IoT (internet of things) devices, due mainly to the high data transfer rate required over terminal devices without restriction of information format. In this work, a review of two Radio over Fiber strategies is presented. Both have excellent performance and even offer the possibility to extend wireless area coverage where mobile networks do not reach or the 802.11 network presents issues. Radio Frequency over Fiber (RFoF) and intermediate Frequency over Fiber (IFoF) are two transmission strategies compatible with the required new broadband services and both play a key role in the design of the next generation integrated optical–wireless networks, such as 5G and Satcom networks, including on RAU (Remote Antenna Unit) new functionalities to improve their physical dimensions, employing a microelectronic layout over nanometric technologies

MIMO RADIO-OVER-FIBRE DISTRIBUTED ANTENNA SYSTEM FOR NEXT GENERATION WIRELESS COMMUNICATION

This thesis introduces low-cost implementations for the next generation distributed antenna system (DAS) using analogue radio over fibre. A multiple-input-multiple-output (MIMO) enabled radio over fibre (RoF) system using double sideband (DSB) frequency translation system is proposed. In such a system, the 2x2 MIMO signals can be transmitted to the remote antenna units (RAUs) from the base station via a single optical link. By using the DSB frequency translation, the original single-input-single-output (SISO) DAS can be upgraded into the MIMO DAS without implementing parallel optical links. Experimentally, the DSB frequency translation 2x2 MIMO RoF system transmits 2x2 LTE MIMO signals with 20MHz bandwidth in each channel via a 300m MMF link. The condition number of the system is <10dB within the power equaliser bandwidth which means the MIMO system is well-conditioned and the crosstalk between the channels can be compensated by the MIMO signal processing. To install the DSB frequency translation system in a wideband service-agnostic DAS, the original MIMO signals need to be translated into unoccupied frequency bands over the DAS, which are usually occupied by specific applications that are not to be transmitted over the DAS. The frequency spectrum allocation of the wireless services is analysed showing that by choosing a particular LO frequency (2.2GHz in the UK), in the DSB frequency translation system, the original MIMO signals can always be translated into unoccupied frequency bands so that the same infrastructure can support multiple services. The idea of DSB frequency translation system can not only support MIMO radio over fibre but can also improve the SFDR of a general radio over fibre system. Because when the upper sideband and the lower sideband of the signal after translation are converted back to the original frequency band, the noise adds incoherently but the signals add-up coherently, this gives the system theoretically 2dB 3rd order SFDR improvement. If the idea of the DSB frequency translation is extended into a higher number of sidebands, the system SFDR can be further improved. Experimentally, the system 3rd order SFDR can be improved beyond the intrinsic optical link by 2.7dB by using quadruple sideband (QSB) frequency translation. It means the optical bandwidth in a general RoF system can be traded for the electrical SFDR. By integrating the analogue and the digital RoF systems, a hybrid DAS has been demonstrated, showing that the EVM dynamic range for the 4G LTE service (using digital RoF link) can be improved to be similar to the 3G UMTS service (using analogue RoF link), so that fewer number of RAUs for the LTE services are needed

Application priority framework for fixed mobile converged communication networks

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The current prospects in wired and wireless access networks, it is becoming increasingly important to address potential convergence in order to offer integrated broadband services. These systems will need to offer higher data transmission capacities and long battery life, which is the catalyst for an everincreasing variety of air interface technologies targeting local area to wide area connectivity. Current integrated industrial networks do not offer application aware context delivery and enhanced services for optimised networks. Application aware services provide value-added functionality to business applications by capturing, integrating, and consolidating intelligence about users and their endpoint devices from various points in the network. This thesis mainly intends to resolve the issues related to ubiquitous application aware service, fair allocation of radio access, reduced energy consumption and improved capacity. A technique that measures and evaluates the data rate demand to reduce application response time and queuing delay for multi radio interfaces is proposed. The technique overcomes the challenges of network integration, requiring no user intervention, saving battery life and selecting the radio access connection for the application requested by the end user. This study is split in two parts. The first contribution identifies some constraints of the services towards the application layer in terms of e.g. data rate and signal strength. The objectives are achieved by application controlled handover (ACH) mechanism in order to maintain acceptable data rate for real-time application services. It also looks into the impact of the radio link on the application and identifies elements and parameters like wireless link quality and handover that will influence the application type. It also identifies some enhanced traditional mechanisms such as distance controlled multihop and mesh topology required in order to support energy efficient multimedia applications. The second contribution unfolds an intelligent application priority assignment mechanism (IAPAM) for medical applications using wireless sensor networks. IAPAM proposes and evaluates a technique based on prioritising multiple virtual queues for the critical nature of medical data to improve instant transmission. Various mobility patterns (directed, controlled and random waypoint) has been investigated and compared by simulating IAPAM enabled mobile BWSN. The following topics have been studied, modelled, simulated and discussed in this thesis: 1. Application Controlled Handover (ACH) for multi radios over fibre 2. Power Controlled Scheme for mesh multi radios over fibre using ACH 3. IAPAM for Biomedical Wireless Sensor Networks (BWSN) and impact of mobility over IAPAM enabled BWSN. Extensive simulation studies are performed to analyze and to evaluate the proposed techniques. Simulation results demonstrate significant improvements in multi radios over fibre performance in terms of application response delay and power consumption by upto 75% and 15 % respectively, reduction in traffic loss by upto 53% and reduction in delay for real time application by more than 25% in some cases

GaN-Based Micro-LED Visible Light Communication: Line-of-Sight VLC with Active Tracking and None-Line-of-Sight VLC Demonstration

abstract: Visible light communication (VLC) is the promise of a high data rate wireless network for both indoor and outdoor uses. It competes with 5G radio frequency (RF) system as well. Even though the breakthrough of Gallium Nitride (GaN) based micro-light-emitting-diodes (micro-LEDs) enhances the -3dB modulation bandwidth dramatically from tens of MHz to hundreds of MHz, the optical power onto a fast photo receiver drops exponentially. It determines the signal to noise ratio (SNR) of VLC. For full implementation of the useful high data-rate VLC link enabled by a GaN-based micro-LED, it needs focusing optics and a tracking system. In this dissertation, we demonstrate a novel active on-chip monitoring system for VLC using a GaN-based micro-LED and none-return-to-zero on-off keying (NRZ-OOK) modulation scheme. By this innovative technique without manual focusing, the field of view (FOV) was enlarged to 120° and data rates up to 600 Mbps at a bit error rate (BER) of 2.1×10⁻⁴ were achieved. This work demonstrates the establishment of a VLC physical link. It shows improved communication quality by orders, making it optimized for real communications. This dissertation also gives an experimental demonstration of non-line-of-sight (NLOS) visible light communication (VLC) using a single 80 μm gallium nitride (GaN) based micro-light-emitting diode (micro-LED). IEEE 802.11ac modulation scheme with 80 MHz bandwidth, as an entry level of the fifth generation of Wi-Fi, was employed to use the micro-LED bandwidth efficiently. These practical techniques were successfully utilized to achieve a demonstration of line-of-sight (LOS) VLC at a speed of 433 Mbps, and a bit error rate (BER) of 10⁻⁵ with a free space transmit distance 3.6 m. Besides this, we demonstrated directed NLOS VLC links based on mirror reflections with a data rate of 433 Mbps and a BER of 10⁻⁴. For non-directed NLOS VLC using a print paper as the reflective material, 195 Mbps data rate and a BER of 10⁻⁵ was achieved.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Acesso rádio UMTS, WLAN e WIMAX sobre fibra

Mestrado em Engenharia Electrónica e TelecomunicaçõesO presente trabalho tem por objectivo o estudo e implementação de uma rede óptica passiva para a transmissão de sinais rádio sobre fibra. Para tal, são estudados e analisados diversos componentes optoelectrónicos que constituem uma rede óptica passiva, tendo em vista a optimização e desenvolvimento da mesma. Por forma a definir os limites, bem como desenvolver conhecimentos sobre os processos que limitam ondas de rádio em fibra, foram realizadas simulações computacionais em redes óptica passivas com transmissão de sinais 3G-UMTS, objectivando estudar possibilidades de acesso múltiplo, bem como os efeitos da alteração de determinadas propriedades dos dispositivos ópticos. Para demonstrar os processos limitativos da propagação, laboratorialmente foram implementadas duas topologias de redes ópticas passivas recorrendo a amplificadores ópticos e lasers de baixo custo, para estudar a transmissão de multi-formatos de sinais rádio sobre fibra. A primeira consiste na transmissão de um canal que consiste na modulação directa de um laser com o sinal rádio que pode ser 3G-UMTS, WLAN ou WiMAX. A segunda inclui, para além do cenário apresentado, um canal extra modulado em amplitude num cenário de multiplexagem no comprimento de onda. ABSTRACT: The present work intends to study and implement a passive optical network for the transmission of radio signals over optical fiber. For this intent, several optoelectronic devices used in passive optical networks were studied and analyzed in order to optimize the developed network. A passive optical network for the transmission of 3G-UMTS signals was simulated and the effect of multiple access and other optical factors were studied and analyzed. In the laboratory were implemented two different topologies for passive optical networks using low cost optical amplifiers and lasers in multi-format multiwavelength radio over fiber signals. The first consider the transmission of a single channel consisting of directly modulating the laser with a radio signal that can be UMTS, WLAN or WiMAX, and the second includes an extra channel with amplitude modulated signals in a wavelength division multiplexing scenario

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

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