Cognitive radio Over fibre: potential advantages for spectrum management

The paper explores some of the advantages that radio over fibre technologies can bring to wireless networks when combined with cognitive radio techniques

Cognitive radio systems in LTE networks

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.The most important fact in the mobile industry at the moment is that demand for wireless services will continue to expand in the coming years. Therefore, it is vital to find more spectrums through cognitive radios for the growing numbers of services and users. However, the spectrum reallocations, enhanced receivers, shared use, or secondary markets-will not likely, by themselves or in combination, meet the real exponential increases in demand for wireless resources. Network operators will also need to re-examine network architecture, and consider integrating the fibre and wireless networks to address this issue. This thesis involves driving fibre deeper into cognitive networks, deploying microcells connected through fibre infrastructure to the backbone LTE networks, and developing the algorithms for diverting calls between the wireless and fibre systems, introducing new coexistence models, and mobility management. This research addresses the network deployment scenarios to a microcell-aided cognitive network, specifically slicing the spectrum spatially and providing reliable coverage at either tier. The goal of this research is to propose new method of decentralized-to-distributed management techniques that overcomes the spectrum unavailability barrier overhead in ongoing and future deployments of multi-tiered cognitive network architectures. Such adjustments will propose new opportunities in cognitive radio-to-fibre systematic investment strategies. Specific contributions include: 1) Identifying the radio access technologies and radio over fibre solution for cognitive network infrastructure to increase the uplink capacity analysis in two-tier networks. 2) Coexistence of macro and microcells are studied to propose a roadmap for optimising the deployment of cognitive microcells inside LTE macrocells in the case of considering radio over fibre access systems. 3) New method for roaming mobiles moving between microcells and macrocell coverage areas is proposed for managing spectrum handover, operator database, authentication and accounting by introducing the channel assigning agent entity. The ultimate goal is to reduce unnecessary channel adaptation

Green radio communication networks applying radio-over-fibre technology for wireless access

Wireless communication increasingly is becoming the first choice link to enter into the global information society. It is an essential part of broadband communication networks, due to its capacity to cover the end-user domain, outdoors or indoors. The use of mobile phones and broadband has already exceeded the one of the fixed telephones and has caused tremendous changes in peoples life, as not only to be recognised in the current political overthrows. The all-around presence of wireless communication links combined with functions that support mobility will make a roaming person-bound communication network possible in the near future. This idea of a personal network, in which a user has his own communication environment available everywhere, necessitates immense numbers of radio access points to maintain the wireless links and support mobility. The progress towards “all-around wireless” needs budget and easily maintainable radio access points, with simplified signal processing and consolidation of the radio network functions in a central station. The RF energy consumption in mobile base stations is one of the main problems in the wireless communication system, which has led to the worldwide research in so called green communication, which offers an environmentally friendly and cost-effective solution. In order to extend networks and mobility support, the simplification of antenna stations and broadband communication capacity becomes an increasingly urgent demand, also the extension of the wireless signal transmission distance to consolidate the signal processing in a centralised site. Radio-over-Fibre technology (RoF) was considered and found to be the most promising solution to achieve effective delivery of wireless and baseband signals, also to reduce RF energy consumption. The overall aim of this research project was to simulate the transmission of wireless and baseband RF signals via fibre for a long distance in high quality, consuming a low-power budget. Therefore, this thesis demonstrated a green radio communication network and the advantage of transmitting signals via fibre rather than via air. The contributions of this research work were described in the follows: Firstly, a comparison of the power consumption in WiMAX via air and fibre is presented. As shown in the simulation results, the power budget for the transmission of 64 QAM WiMAX IEEE 802.16-2005 via air for a distance of 5km lies at -189.67 dB, whereas for the transmission via RoF for a distance of 140km, the power consumption ranges at 65dB. Through the deployment of a triple symmetrical compensator technique, consisting of SMF, DCF and FBG, the transmission distance of the 54 Mbps WiMAX signal can be increased to 410km without increasing the power budget of 65dB. An amendment of the triple compensator technique to SMF, DCF and CFBG allows a 120Mbps WiMAX signal transmission with a clear RF spectrum of 3.5 GHz and constellation diagram over a fibre length of 792km using a power budget of 192dB. Secondly, the thesis demonstrates a simulation setup for the deployment of more than one wireless system, namely 64 QAM WiMAX IEEE 802.16-2005 and LTE, for a data bit rate of 1Gbps via Wavelength Division Multiplexing (WDM) RoF over a transmission distance of 1800km. The RoF system includes two triple symmetrical compensator techniques - DCF, SMF, and CFBG - to obtain a large bandwidth, power budget of 393.6dB and a high signal quality for the long transmission distance. Finally, the thesis proposed a high data bit rate and energy efficient simulation architecture, applying a passive optical component for a transmission span up to 600km. A Gigabit Optical Passive Network (GPON) based on RoF downlink 2.5 Gbps and uplink 1.25Gbps is employed to carry LTE and WiMAX, also 18 digital channels by utilising Coarse Wavelength Division Multiplexing (CWDM). The setup achieved high data speed, a low-power budget of 151.2dB, and an increased service length of up to 600km

Optical techniques for broadband in-building networks

Optical fibres, which can easily handle any bandwidth demand, have been rolled out to more than 32 million consumer’s homes and professional buildings worldwide up to 2010. The basic technological and economical challenges of fibre-to-the-home (FTTH) has been solved. The current FTTH technology can now providing baseband Gbit Ethernet and high definition TV services to the gates of homes. Thus, the bottleneck for delivery of broadband services to the end users is shifting from the access network to the in-building network. In the meantime, the need for high-capacity transmission between devices inside the building, e.g. between desktop PC and data services, are also rapidly increase. How to bring high bandwidth to the mobile terminals such as laptops, PDAs or cell phones as well as to the fixed terminals such as desktop PCs and HDTV equipment in an all-in-one network infrastructure is a challenge we are facing. Building on the flexibility of the wireless access networks and the latent vast bandwidth of a fibre infrastructure, radio-over-fibre (RoF) techniques have been proposed as a cost-effective solution to the future integrated broadband services in in-building networks. This thesis investigates techniques to deliver high data rate wireless services via in-building networks: high capacity RoF links employing optical frequency multiplication (OFM) and sub-carrier multiplexing (SCM) techniques, with single- or multi-carrier signal formats. The orthogonal frequency division multiplexing (OFDM) format is investigated for the RoF transmission system, particularly with regard to the optical system nonlinearity. For low-cost short-range optical backbone networks, RoF transmission over large-core diameter plastic optical fibre (POF) links has been studied, including the transmission of the WiMedia-compliant multiband OFDM UWB signal over bandwidth-limited large-core POF as well as a full-duplex bi-directional UWB transmission over POF. In order to improve the functionalities for delivery of wireless services of in-building networks, techniques to introduce flexibility into the network architecture and to create dynamic capacity allocation have been investigated. By employing optical switching techniques based on optical semiconductor amplifiers (SOA), an optically routed RoF system has been studied. The dynamic capacity allocation is addressed by investigating one-dimensional and two-dimensional routing using electrical SCM and optical wavelengths. In addition, next to RoF networking, this thesis explores techniques for wired delivery of baseband high capacity services over POF links by employing a multi-level signal modulation format, in particular discrete multi-tone (DMT) modulation. Transmission of 10 Gbit/s data over 1 mm core diameter PMMA POF links is demonstrated, as a competitor to more expensive fibre solutions such as silica single and multimode fibre. A record transmission rate of more than 40 Gbit/s is presented for POF whose core diameter is comparable with silica multimode fibre. Finally, from the network perspective, the convergence of wired and wireless multi-standard services into a single fibre-based infrastructure has been studied. Techniques have been designed and demonstrated for in-building networks, which can convey both high capacity baseband services and broadband radio frequency (RF) services over a POF backbone link. The multi-standard RoF signals carry different wireless services at different radio frequencies and with different bandwidths, including WiFi, WiMax, UMTS and UWB. System setups to carry them together over the same multimode optical fibre based network have been designed and experimentally shown. All the concepts, designs and system experiments presented in this thesis underline the strong potential of multimode (silica and plastic) optical fibre techniques for the delivery of broadband services to wired and wireless devices in in-building networks, in order to extend to the end user the benefits of the broadband FTTH networks which are being installed and deployed worldwide

Studies on Optical Components and Radio Over Fibre Systems

In the modern era good communication systems are the need of the hour. This project includes the study of optical components and Radio over Fibre systems. Various Optical components are used in optical systems and those optical components have different characteristics. Various optical components have been studied in this project and in addition to that there is a study of components using S-matrix. The use of S-matrix in analyising the directional coupler. Optical networks can be analysed with the same methods as microwave networks in theory of microwave networks, components are generally represented by complex scattering parameters which form the S- matrix. we adopted this formalism to fibre optic coupler used in optical network taking the polarization dependence into account. There is the study of Fabry- perot filter in which the study of free spectral range (FSR) and the Transfer function was determined through Matlab simulation. The results thus obtained are studied. For the future provisions of broadband, multimedia the radio over fibre systems are a good alternative. RoF systems are used basically because of their low loss and extremely wide bandwidth and robustness. Radio over fibre can use millimeter waves and serve as a high speed wireless local or personal area network. In this project various parts of the Radio over fibre systems are studied, The power spectrum measurements of a millimeter wave Radio over Fibre under different single mode fibre length is done with a Matlab simulation it is found that the fading occurs at some values of length of fibre in the power spectrum. In radio over fibre systems the two subcarrier modulations (SCMs) i.e., single sideband and tandem single sideband have been widely used both SSB and TSSB SCMs can be obtained by using optical mach Zehnder modulator. In this project we investigate the impact of the impact of the harmonic distortion and inter modulation distortion in RoF systems for one wavelength carrying two radio frequency signals with either SSB or TSSB SCM. It is found that non linear distortion can be reduced when the frequency difference ~ 1 GHz. It was found that non linear distortion strongly depends on the modulation index. The source of these results was a mat lab simulation and calculations. For the different values of the signal frequencies the NSR was calculated

Experimental Evaluation of Hybrid Fibre−Wireless System for 5G Networks

This article describes a novel experimental study considering a multiband fibre–wireless system for constructing the transport network for fifth-generation (5G) networks. This study describes the development and testing of a 5G new radio (NR) multi-input multi-output (MIMO) hybrid fibre–wireless (FiWi) system for enhanced mobile broadband (eMBB) using digital pre-distortion (DPD). Analog radio over fibre (A-RoF) technology was used to create the optical fronthaul (OFH) that includes a 3 GHz supercell in a long-range scenario as well as a femtocell scenario using the 20 GHz band. As a proof of concept, a Mach Zehnder modulator with two independent radio frequency waveforms modifies a 1310 nm optical carrier using a distributed feedback laser across 10 km of conventional standard single-mode fibre. It may be inferred that a hybrid FiWi-based MIMO-enabled 5G NR system based on OFH could be a strong competitor for future mobile haul applications. Moreover, a convolutional neural network (CNN)-based DPD is used to improve the performance of the link. The error vector magnitude (EVM) performance for 5G NR bands is predicted to fulfil the Third Generation Partnership Project’s (3GPP) Release 17 standards

Timing Signals and Radio Frequency Distribution Using Ethernet Networks for High Energy Physics Applications

Timing networks are used around the world in various applications from telecommunications systems to industrial processes, and from radio astronomy to high energy physics. Most timing networks are implemented using proprietary technologies at high operation and maintenance costs. This thesis presents a novel timing network capable of distributed timing with subnanosecond accuracy. The network, developed at CERN and codenamed “White- Rabbit”, uses a non-dedicated Ethernet link to distribute timing and data packets without infringing the sub-nanosecond timing accuracy required for high energy physics applications. The first part of this thesis proposes a new digital circuit capable of measuring time differences between two digital clock signals with sub-picosecond time resolution. The proposed digital circuit measures and compensates for the phase variations between the transmitted and received network clocks required to achieve the sub-nanosecond timing accuracy. Circuit design, implementation and performance verification are reported. The second part of this thesis investigates and proposes a new method to distribute radio frequency (RF) signals over Ethernet networks. The main goal of existing distributed RF schemes, such as Radio-Over-Fibre or Digitised Radio-Over-Fibre, is to increase the bandwidth capacity taking advantage of the higher performance of digital optical links. These schemes tend to employ dedicated and costly technologies, deemed unnecessary for applications with lower bandwidth requirements. This work proposes the distribution of RF signals over the “White-Rabbit” network, to convey phase and frequency information from a reference base node to a large numbers of remote nodes, thus achieving high performance and cost reduction of the timing network. Hence, this thesis reports the design and implementation of a new distributed RF system architecture; analysed and tested using a purpose-built simulation environment, with results used to optimise a new bespoke FPGA implementation. The performance is evaluated through phase-noise spectra, the Allan-Variance, and signalto- noise ratio measurements of the distributed signals

Optimised Radio over Fibre Links for Next Generation Radio Access Networks

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonOptical fibre has become the dominant theme of transmission in long haul, high data rate communication systems due to its tremendous bandwidth and low loss. Radio over Fibre (RoF) technology facilitates the seamless integration between wireless and optical communication systems and found to be the most promising solution to meet the exponential bandwidth demands expected for the upcoming years. However, the main bit-rate/distance limitation in RoF systems is the chromatic dispersion. In this thesis, the two generations of RoF technologies, namely Analogue RoF (ARoF) and Digital RoF (DRoF) are investigated. The overall aim of this research is to optimise the optical bandwidth utilisation of these two approaches for a typical transmission of the fronthaul link proposed in the next generation Centralised Radio Access Network (C-RAN). Consequently, a number of physical layer design scenarios for the optimised transmission of the Radio Frequency (RF) signals over a Standards Single Mode Fibre (SSMF) are demonstrated. Firstly, for an ARoF transmission, where the analogue RF signals are transported over SSMF using an optical carrier, a bidirectional link transmitting four Downlink/Uplink channels in a chromatic dispersion limited scenario is designed. Simulation results have shown a clear constellation diagram of a 2.5 Gb/s RF signal transmission over 120 km fibre length. Secondly, a DRoF system with reduced optical bandwidth occupancy is proposed. This system employs an optical Duobinary transmission to the digitised RF signal at the transmitter side to reduce its spectrum and to address the chromatic dispersion effect, simultaneously. Simulation results demonstrate the capability of the proposed system to maintain high-quality transmission of the digitised signals over 70 km of fibre distance without dispersion compensation requirements. Finally, an advanced DRoF transmission link based on integrating digital Optical Single Sideband (OSSB) transmission with Duobinary encoding scheme is designed. Simulation results have clearly verified system’s robustness against transmission impairments and have better performances in terms of the obtained BER and EVM with respect to the 3GPP standardised values. Moreover, the results show that both transmission distance and power budget are furtherly improved in comparison with two other digital transmission scenarios