Broadband millimetre-wave fibre-radio access networks

© 2000 Dr. Graham H. Smith.Millimetre-wave (mm-wave) fibre-radio networks are emerging as a promising technology for providing customer access to future interactive broadband multimedia services. At mm-wave frequencies, propagation effects through air limit radio cell sizes so an implementation of a mm-wave fibre-radio network would require large numbers of simple, low-cost antenna base stations (BSs). To achieve this goal, it is advantageous to share some of the electronic functionality and processing at a central office (CO) rather than at each BS, with the connection between the CO and BSs provided by an optical fibre network The integration of the optical and radio technologies poses a new set of technical challenges. These include mm-wave generation schemes using optics, effects of fibre distribution on radio signals, implementation of low cost BSs, network architectures that provide lower cost links with improved system performance, and system modelling techniques. This thesis advances each of these areas. The optical chirp associated with modulation is shown to be able to improve fibre link performances that are usually limited by chromatic dispersion. Furthermore, a novel modulation scheme generating an optical single sideband- with-carrier (OSSB-WC) spectrum and a novel frequency tripling self-heterodyning scheme are shown to also significantly reduce the effects of fibre dispersion. These optical sources are also inc1uded in demonstrations of a number of novel bi-directional links. A descriptive analysis is used to determine the expected system performance using each technique. This same analysis is extended to predict component specifications and system algorithms that are necessary to achieve certain levels of system performance in a variety of mm-wave fibre-radio link scenarios. The thesis also examines the optical-radio interface and determines suitable techniques that can be used to transport different radio modulation formats, inc1uding multilevel QAM and spread spectrum signals. The physical optoelectronic interface is also considered and a novel system function and hybrid integrated circuit package design is described. A major contribution of this thesis is a detailed investigation into wavelength-division-multiplexing (WDM) based mm-wave fibre-radio networks. Simple uni-directional ring/bus and star-tree architectures are proposed and implemented and the deterioration effects of linear and homodyne crosstalk are also considered so that the limitations of each architecture can be determined. The final major contribution of this thesis is to examine the modelling of mm-wave fibre-radio systems, which is especially important for dimensioning networks. One critical parameter that does require consideration in the models is the deterioration of signal quality from intermodulation distortion in multi-carrier systems. This thesis extends conventional fixed load models that have been developed for low frequency fibre-radio networks and applied them to mm-wave systems. This fixed load model was the first attempt to link physical layer limitations to system performance. While the model derived is simple and fast to simulate, it does not model the behaviour of users in the system. In this thesis, the first model to link physical layer limitations and user behaviour has been implemented and the significant changes in the expected system performance are shown. The model can also be used to predict the required component specifications and for examining system algorithms that are necessary to achieve certain levels of system performance in a variety of mm-wave fibre-radio link scenarios