Husileng Bao, Mikrovågselektronik

Opponent: Guy Torfs, Professor, Ghent University, Belgium

Sammanfattning: 

The advent of beyond-5G (B5G) and 6G technologies brings increases in wireless
devices and their applications. Although massive multiple-input-multiple-output
(MIMO) delivers high-capacity services using co-located MIMO (C-MIMO) technology,
distributed MIMO (D-MIMO) technology offers a more uniform user service.
This thesis introduces an automatic D-MIMO testbed featuring a statistical
MIMO capacity analysis for an indoor use case. Additionally, raytracing-based
simulations are employed for predictions and comparisons in an indoor scenario. The
statistical MIMO capacity analysis demonstrates that D-MIMO outperforms C-MIMO
in terms of both higher and more uniform capacity, as observed in measurements
and simulations.
A promising solution for such future communication systems is radio-over-fiber
(RoF). Achieving data rates in the range of several tens of Gbit/s necessitates the
utilization of the millimeter-wave (mm-wave) frequency band in RoF. However, mmwave
signals exhibit high propagation loss. Overcoming these challenges requires the
incorporation of beamforming and/or MIMO technology in mm-wave RoF systems.
Subsequently, a mm-wave sigma-delta-over-fiber (SDoF) link architecture is
proposed for MIMO applications. The first implementation utilizes bandpass sigmadelta
modulation (SDM) between a central unit (CU) and a remote radio unit
(RRU) through a commercially available QSFP28-based optical interconnect. The
implementation achieves symbol rates of 700/500 Msym/s for single-input-singleoutput
(SISO)/multi-user MIMO (MU-MIMO) cases at a 1 m over-the-air (OTA)
distance. The second implementation employs lowpass SDM between a CU and a
RRH, and reaches 1 Gsym/s with 1024-quadrature amplitude modulation (1024-
QAM) signal across a 5 m OTA distance.
Furthermore, the proposed mm-wave link is extended to two SDoF D-MIMO
architectures, both incorporating a CU-inherited local oscillator for phase coherence
verification. The bandpass SDoF-based D-MIMO system supports a 748 MHz
bandwidth with orthogonal frequency-division multiplexing (OFDM) signals for
multiple-input-single-output (MISO)/MU-MIMO cases, while the lowpass SDoFbased
D-MIMO system operates in the W-band for MISO measurement cases.
In conclusion, this thesis has shown that D-MIMO surpasses C-MIMO in both
capacity and uniformity, as validated through statistical analyses from measurements
and simulations. The proposed innovative mm-wave SDoF D-MIMO architectures
lay the foundation for future high-capacity wireless communication networks.