Usman Habib

The new flexible mobile fronthaul: Digital or analog, or both?

It has become apparent that current fronthaul technology cannot be simply extended to meet the projected demands of 5G and beyond mobile systems. This current technology, based on the transport of sampled radio waveforms, has been the preferred option, with analog radio over fiber reserved to relatively niche application scenarios. However, for future systems, it is recognised that different functional splits between the central location and the remote units are needed; sampled waveform transport is not scalable to these systems. We propose a flexible fronthaul, therefore, in which both digital and analog transport technologies can coexist. Using practical examples from our work, we describe where these technologies can be used in the future fronthaul.

In-fibre diffraction grating based beam steering for full duplex optical wireless communication

A novel approach to achieve wavelength controlled optical beam steering using a 45° tilted fiber grating (TFG) for full-duplex indoor optical wireless transmission is proposed and experimentally demonstrated for the first time. The 45° TFG functions as an in-fiber passive diffraction device for wavelength steered light emission and reception, which enables full-duplex optical wireless transmission. The unique advantages of using an in-fiber TFG device for beam steering include high diffraction efficiency, low cost, compactness and inherent compatibility with existing fiber links. In a proof-of-concept experiment, 1.4 m freespace full-duplex transmission has been demonstrated with data rate of 9.6 Gb/s per beam using 2.4 GHz bandwidth signals.

Performance improvement for OFDM-RoF transported 60 GHz system using spatial diversity and multiplexing

60 GHz system architectures with Radio over Fiber (RoF) transport and integrated transmitters/receivers provide a comprehensive solution for future mobile systems. Since 60 GHz communication relies on line-of-sight (LoS) conditions and narrow-beam antennas to compensate the high path-loss, it has limitations in terms of coverage for multiple user locations. In this paper, performance analysis of a 60 GHz integrated transmitter and receiver system supported by RoF transport has been performed experimentally at different user locations for up to 1.5m transmission distance. Extension of experimental results to prove feasibility for longer distances has been shown with a simulation model, whose results at various shorter distances have been benchmarked against the acquired experimental results at different user locations. A modified version of the Saleh Valenzuela channel has been used to model the millimeter wave (mmW) LoS indoor experimental environment. Furthermore, as a proof of concept, we present an experimental analysis demonstrating an improvement in performance of the proposed RoF based 60 GHz system using spatial diversity and multiplexing. Channel measurements at different transmitter/receiver locations and their processing have shown that an improvement (decrease from 12.5% to 10.5%) in Error Vector Magnitude (EVM) can be achieved using the Alamouti Space Time Block Coding algorithm. Then it has been shown that a two-fold data rate increase can be obtained by combining data from two transmitter locations using the Zero Forcing algorithm.

Wavelength-controlled beam steering for optical wireless transmission using an in-fiber diffraction grating

Passive beam steering for optical wireless transmission based on wavelength tuning using a novel in-fiber diffraction grating featuring compactness, high diffraction efficiency and inherent fiber-compatibility, is proposed and experimentally demonstrated for the first time.

Radio over fiber transport of mm-Wave 2×2 MIMO for spatial diversity and multiplexing

DWDM-RoF transport and photonic generation of millimeter-wave MIMO signals has been demonstrated. Generation and modulation of independent data streams over different wavelengths provides allocation flexibility and centralization. EVM results show that this low-cost technique provides antenna diversity/multiplexing gain for STBC-Alamouti and Zero-Forcing algorithms based OFDM-MIMO.

Demonstration of radio-over-fiber-supported 60 GHz MIMO using separate antenna-pair processing

Coverage at millimeter-wave (mmW) frequencies is a constraining bottleneck. Spatial diversity and spatial multiplexing multiple-input multiple-output (MIMO) improve performance over a spread of user locations and these can benefit from wider antenna spacing. Radio-over-Fiber (RoF) transport provides flexibility in deploying a number of widely-spaced Remote Antenna Units (RAUs) connected to the same Central Unit (CU). Hence, mmW systems with an integrated analog RoF fronthaul are strong candidates for use in future 5G networks. An approach to measure channel coefficients individually for MIMO processing has been demonstrated in a RoF transported 2×2 MIMO system at 60 GHz. Experimental results verify this approach through real 2×2 experiments.