High Capacity Fiber-Connected Wireless MIMO Communication

There will be more and more users while beyond-5G (B5G) and 6G bring more wireless applications. Current cellular communication networks assign specific serving boundaries for each radio, which becomes a limitation when too many users work with one radio simultaneously. By physically distributing radios. user’s service can be more uniform. Radio-over-fiber is a promising enabling technology for distributed antenna systems.To have several tens of Gbit/s data rate, we need to apply millimeter-wave (mm-wave) frequency band in radio-over-fiber (RoF). However, mm-wave signals have weak penetration and high propagation loss. Hence, beamforming and/or multiple-input-multiple-output (MIMO) technology become necessary for mm-wave RoF to overcome those drawbacks.This thesis introduces an automatic distributed MIMO (D-MIMO) testbed with a statistical MIMO capacity analysis for an indoor use case. Raytracing-based simulations also predicts the indoor case to make a comparison. The statistical MIMO capacity analysis shows that D-MIMO has a higher and more uniform capacity than co-located MIMO (C-MIMO) in measurements and simulations.Next, a mm-wave sigma-delta-over-fiber (SDoF) link architecture is proposed for MIMO applications. In the implementation of this link, a QSFP28 fiber link connects a central unit with a remote radio unit with four bandpass sigma-delta-modulation (BPSDM) bitstreams. The remote radio unit generates four mm-wave signals from four BPSDM signals and feeds a linear array antenna. The measurement characterizes the remote radio head at each stage and concludes that this proposed link can reach 800 Msym/s data rate with -0.5 dBm output bandpower.Furthermore, the proposed link is demonstrated with digital beamforming and multi-user MIMO (MU-MIMO) functionalities. The digital beamforming function reaches 700 Msym/s with -25 dB error vector magnitude (EVM) results by improving the received bandpower in comparison to (single-input-single-output) SISO results. The MU-MIMO function serves two independent users at 500 Msym/s symbol rate and satisfies 3GPP requirements at 1 m over-the-air distance.In conclusion, this thesis proves that D-MIMO has a higher and more uniform capacity than C-MIMO by statistical analysis from measurements and simulations. The proposed novel mm-wave SDoF link can pave the way for future D-MIMO applications

Demonstration of Flexible mmWave Digital Beamforming Transmitter using Sigma-Delta Radio-Over-Fiber Link

This work demonstrates a millimeter-wave digital beamforming transmitter based on a sigma-delta radio-over-fiber link. The digital beamforming is controlled from a central unit and distributed to a remote radio unit using a standardized quad small form-factor pluggable 28 (QSFP28) fiber connection. The experimental results demonstrate 26.2 GHz transmission with high-quality beamforming functionality up to 130 MHz effective radio bandwidth at 2.2 m wireless distance. The solution offers a flexible transmitter solution suitable for millimeter-wave distributed active antenna systems

Comparison of Co-located and Distributed MIMO for Indoor Wireless Communication

This paper compares the communication performance for co-located and emerging distributed MIMO in a typical indoor scenario. The simulations, which are verified against experimental measurement data, show that distributed MIMO offers a significantly more uniform capacity for the users. The results also show that the same user capacity can be achieved with half the number of antennas in the distributed MIMO case

Localization With Distributed MIMO Using a High-Speed Sigma-Delta-Over-Fiber Testbed

Distributed MIMO (D-MIMO) with synchronized access points (APs) is a promising architecture for both communications and localization in 5G and beyond systems. In this letter, we develop a time-difference-of-arrival (TDOA)-based indoor localization system using a 2.35-GHz high-speed sigma-delta-over-fiber (SDoF) D-MIMO testbed with 40-MHz bandwidth, exploiting the fully synchronized nature of the APs. Experimental results over an area of size 100 m\ub2 demonstrate accuracies below 0.2 m and agree with the theoretical Cram\ue9r-Rao bounds (CRBs) at most measurement locations, indicating the localization capability of high-speed SDoF D-MIMO

Automatic Distributed MIMO Testbed for beyond 5G Communication Experiments

This paper demonstrates an automated testbed suitable for beyond-5G distributed MIMO experiments, where bandwidth, number of transmitters and precoding methods are flexible and configured through a central unit. This is based on an all-digital radio-over-fiber approach to communication through 12 fully coherent, low-complexity remote radio transmitters. An automated robot receiver is implemented to facilitate efficient communication data collection in realistic environments. Using the proposed system, co-located and distributed MIMO communication antenna configurations are compared in a real in-door environment. The results show that distributed MIMO provides more significantly more uniform power distribution and better overall MIMO capacity compared to co-located MIMO

Flexible Mm-Wave Sigma-Delta-Over-Fiber MIMO Link

Millimeter-wave and multiple-input-multiple-output (MIMO) technologies combine broad bandwidth with spatial diversity to offer a greater data rate. This paper investigates a flexible millimeter-wave sigma-delta-over-fiber based transmitter solution with digital beamforming MISO and MIMO functionality. Those functions are controlled by a central unit connecting a remote radio head with a standardized QSFP28 fiber link. The central unit generates binary encoded intermediate frequency signals using bandpass sigma-delta modulation. The QSFP28 based fiber link transmits the intermediate frequency bitstreams to the remote radio head. The remote radio head consists of a QSFP28 module, $90^{\circ }$ hybrids, and upconverters. The remote radio head feeds four parallel, independent, coherent, and central-unit controlled 28\ua0GHz signals to a linear array transmitting antenna. The transmitter performance is experimentally verified, demonstrating up to 800\ua0Msym/s at an EVM/NMSE of 6.7%/-23.5\ua0dB when tested with a 64 quadrature amplitude modulation (64-QAM) modulation scheme. Digital over-the-air beamforming MISO functionality is demonstrated up to 700\ua0Msym/s across 1\ua0m wireless distance. MIMO communication capabilities is demonstrated by over-the-air transmission of two independent 500\ua0Msym/s to two spatially separated receivers. The results show that the proposed link can be used for realization of scalable, low-cost and flexible transmitter solution for emerging distributed antenna systems

Design and Measurements of MSK-LFM RadCom System

This paper focuses on design and measurements of MSK (minimum-shift keying) LFM (linear frequency modulation) RadCom (radar communication) system which is useful in progressing industry with the advantage of cost and integration. MSK has seen many uses in communication systems and LFM in many radar applications because of its good correlation properties. This research is based on the integration of a MSK and LFM signal into a joint RadCom system. Firstly, the signal and system design are introduced, followed by methods of radar signal processing. The paper presents results from simulations and lab experiments, supporting the corresponding theory. Simulation results shows that a range resolution of 13.2 cm can be achieved using 1 GHz bandwidth. Lab measurements support this result and it is shown that a range resolution of 6 cm can be achieved using a wider bandwidth