Analogue Radio Over Fiber Aided Wireless MIMO Downlink System Design

Abstract

In this thesis, we design cost-efficient high-performance communication systems employing analogue radio over fiber (A-RoF) techniques combined with wireless multiple-inputmultiple-output (MIMO) techniques. Our objective is to exploit the A-RoF design for reducing complexity of MIMO signal processing, without degrading the MIMO gains attained. <br/><br/>Explicitly, we propose four novel systems involving both A-RoF and wireless MIMO schemes. Firstly, we conceive a novel A-RoF aided beamforming technique beneficially exploiting the fiber’s potentially harmful non-linearity, in order to circumvent the excessive insertion loss of electronic phase-shifters. In this system, the phased array antenna elements are fed by the output of the highly non-linear fiber (HNLF), resulting in a beneficial angular beamsteering range depending on the length of the HNLF used, which can be exploited by sophisticated cloud/centralised radio access networks (C-RANs) for reducing the co-channel interference. Secondly, we propose an A-RoF aided spatial modulation (SM) scheme, where the SM’s antenna indices are conveyed by the optical side-bands. Furthermore, we experimentally demonstrate the feasibility of our proposed concept by a prototype system using two-antenna based SM, realising an A-RoF aided SM system supporting a downlink rate of 2 Gbps. Then, we further developed the ARoF aided wireless MIMO design to conceive an adaptive C-RAN system, where both the modulation format and the number of connected remote radio heads are selected depending on the channel conditions. <br/><br/> Additionally, inspired by our previous designs of amalgamating beamforming and SM using A-RoF, we extend our vision to multi-functional MIMO (MF-MIMO) systems. We subsequently conceive a novel A-RoF system design relying on the sophisticated multiset space-time shift keying (MS-STSK) concept, which is capable of combining diversity and SM. This flexible MF-MIMO design carries out its signal processing tasks in a central unit and it is capable of achieving a rate of 10 Gbps using 16QAM. <br/><br/>The above-mentioned three systems rely on using single-mode silicon fiber for outdoor cellular systems, while in our fourth study, we propose an architecture for indoor scenarios in order to meet the increasing demands for in-home services. Thus, we design an all-optical processing aided wireless MF-MIMO architecture employing plastic optical fiber (POF), where both diversity and beamforming gains can be attained. Explicitly, we aim for realising a MF-MIMO system by using radio over POF techniques for RF operating in the 2.4 GHz band. Specifically, Alamouti’s twin-antenna space-time block coded symbols are transmitted using a single Mach-Zehnder modulator (MZM). The attainable angular beamsteering range is 150◦ . We also show that this concept can be extended to a multi-user system using mode division multiplexing (MDM). <br/><br/>Our research described in this thesis demonstrates the feasibility and the benefits of using A-RoF aided MIMO signal processing, in terms of both its cost-reduction and performance-improvements.<br/>