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.

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.

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.

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).

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.

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Identifiers

ORCID for Yichuan Li: orcid.org/0000-0003-2078-0983

ORCID for Mohammed El-Hajjar: orcid.org/0000-0002-7987-1401

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