Millimetre-wave radio-over-fibre supported multi-antenna and multi-user transmission

In this thesis, various features of the RoF supported mmW communication for

future wireless systems have been analysed including photonic generation of mmW

for MIMO operation, performance analysis of mmW MIMO to achieve spatial

diversity and spatial multiplexing with analog RoF fronthaul, and multi-user

transmission in the 60 GHz-band using multiplexing-over-fibre transport and

frequency-selective antenna.

A low cost mmW generation system for two independent MIMO signals has been

presented, consisting of a single optical Phase Modulator (PM). The different

aspects of experimental analysis on RoF-supported mmW MIMO in this thesis,

which were not considered before, include use of specific MIMO algorithm to

understand the amount of improvement in coverage and data rate for a particular

MIMO technique, performance comparison with SISO at several user locations, and

verification of optimum RAU physical spacing for a particular transmission

distance with the theoretical results. The results show that flexible and wider RAU

spacings, required to obtain optimum performance in a mmW MIMO system, can

be achieved using the proposed analog RoF fronthaul. The investigation was

extended to verification of a method to individual measurement of mmW channel

coefficients and performing MIMO processing, which shows that mmW channels

are relatively static and analysis can be extended to much longer distances and

making projections for N×N MIMO.

For mmW multi-user transmission, a novel low cost, low complexity system using

single RoF link and single RF chain with single transmitting antenna has been

presented and characterized, which was based on large number of RF chains and

multiple antenna units previously. The setup involves generation and RoF transport

of a composite SCM signal, upconversion at the RAU and transmission of different

frequency channels towards spatially distributed users using a frequency-selective

Leaky-Wave-Antenna (LWA), to convert Frequency Division Multiplexing (FDM)

in to Spatial Division Multiple Access (SDMA). Analysis on low user-signal

spacing for the SCM shows the feasibility to serve a large number of users within a

specific transmission bandwidth and experimental demonstration to achieve sum

rate of 10Gb/s is shown by serving 20 users simultaneously. Furthermore, investigation on SNR degradation of high bandwidth signals due to beamsteering

effect of the LWA and theoretical calculations of the sum data rate for different

number of users is performed, which shows that the proposed system can provide

much higher sum rates with high available SNR. It was also experimentally

demonstrated that improvement in coverage and spectral efficiency is obtained by

operating multiple LWAs using single RF chain. Finally, an experimental

demonstration of a DWDM-RoF based 60 GHz multi-user transmission using

single LWA is presented to show the feasibility to extend the setup for a multiple

RAU based system, serving each at distinct optical wavelength and performing

direct photonic upconversion at the RAU for low cost mmW generation.