PhD position on Beam Tracking in Wireless Optical Communications

Updated: 2 months ago
Deadline: 30 Apr 2021

Background

The demand for wireless connectivity keeps growing exponentially. Communication by radio is reaching limits as further densification (more bits/s/m2) requires extreme sophistication of massive antenna arrays for beam steering and MIMO. In contrast to this, beam steering of light can rely on simple principles. Interestingly, the Eindhoven region developed world-class expertise in steering beams for optical recording. We see an opportunity for breakthroughs in wireless communication, by reusing these principles.   

Although the international scientific community has shown that one light beam can carry vast amounts of data, concepts for the control of where to steer the beam are not at a level where these can make a realistic chance of being adopted in scalable systems. For a ceiling mounted unit and a user client device to find each other, a 4 dimensional search (x,y on both ends) needs to be executed. Equally of concern is that after a minor deviation of the beam direction, most reported systems in literature do not have ability to derive an error signal to correct for the deviations. In fact, most proposed systems are just two uncoupled one-directional beams, hence a suitable tracking mechanism is not present and full re-acquisition is needed. Rather, most scientific work focuses on a speed race (more bit/s) but disregarded tracking. It can be argued that tracking is a field with more fundamental challenges to be solved.  

System concept for Optical Wireless Communication, inspired by optical recording principles

During development of the CD and DVD there was ample attention to keeping the laser on the track of the disc. Perhaps even more R&D effort went into navigating the laser position with respect to the disc, than on increasing the number of bit/s.

A lesson to be learned from Optical Recording (CD, DVD, ..)  is that electromagnetically actuated system concepts with semi-transparent mirrors can automatically align the angles of incoming and outgoing beam. Moreover, small errors in the incoming beam can be detected by a multi-segmented photodetector, similar to the Optical Pick-Up (OPU) in CD, and can be used to direct the outgoing beam.  These concepts, borrowed from optical recording, are identified (by Oxford Univ [WORTECS EU PROJECT} and Signify) as one of the few concepts that potentially can provide continuous tracking in a feedback loop.

Potential Impact

Via this project, we can give a wealth of inputs to the visual light communications world. We tap into the knowledge still existing from optical recording, which is currently not connected in this way to the photonics and communication community.

Tasks

  • Study of optical wireless communication (OWC) system concept.
  • Study of optical pick-up units (OPUs) and tracking in optical discs.
  • Modelling of OWC system with OPU-based beam acquisition and tracking. Link budget, achievable bit rates versus width of the beam, sensitivity to errors and mis-alignments, acquisition and tracking capabilities. Does a typical OPU suffice to meet all system requirements and if not then how can it be adapted?
  • Design and build a test client system that can shoot a beam back towards an already aligned ceiling unit.
  • Build a system with a controllable direction on both sides.  
  • Evaluate and iteratively optimize the system.

Work environment

Eindhoven University of Technology (TU/e, https://www.tue.nl/en/ ) is one of Europe's top technological universities, situated at the heart of a most innovative high-tech region. Thanks to a wealth of collaborations with industry and academic institutes, TU/e's research is known for its real-world impact and has worldwide a leading position in effective academic - industrial cooperation. TU/e has around 3,000 employees and 2,300 PhD students (half of which international, representing about 70 nationalities).

The candidate will work in the Signal Processing Group (SPS) at the Department of Electrical Engineering (https://www.tue.nl/en/university/departments/electrical-engineering/ ). Within the EE department, research and education is done in domains of Telecommunication, Care and Cure, and Smart energy systems. The SPS group has a strong track record not only in signal processing for digital communication, but also for medical applications and for intelligent lighting systems. The impact of the work of the group is evident from a very close cooperation with industrial partners and research institutes and from international recognition and awards of the team.

The project is run in close cooperation with other Optical Wireless Communication projects at TU/e. Within the SPS group, the team of Prof Jean-Paul Linnartz focusses on intelligent lighting systems and on optical wireless communication. The team is well connected to state-of-art industrial developments, in particular the Signify (Philips Lighting) R&D in LiFi. The team has pioneered in converting nonlinear LED models into signal processing concepts, to boost communication performance. Previously, activities in his research teams led to three new High Tech ventures with unique technologies in security and communications and to over 12,000 citations is scientific literature (GS). A unique aspect of this project is its ambition to reuse technology used in the past for CD and DVD optical storage. In this field many optical principles have been refined to optimize the storage capacity, retrieval speed and robustness.       

Qualifications
In the Signal Processing group, we are looking for a candidate who is interested and has a background in the overall system, but particularly has a background in wireless (optical) communications principles, optics, signal processing algorithms The project includes work on the hardware infrastructure (transceivers, OPUs, control hardware supporting cooperation between multiple emitters and receivers, backbone infrastructure), as well as experimental verification and demonstration of beam acquisition and tracking in practical system trials.

The PhD candidate will have to design, analyze, engineer and implement an OWC system which is able to reliably offer high data rates using advanced signal processing (including diversity, MIMO) techniques. The candidate also should consider constraints in the system design, such as cost-optimized coverage, power consumption, acquisition and tracking speeds, and signaling complexity. Moreover, he/she should validate the system in a realistic system application environment of IoT.

The PhD candidate should regularly report about his/her work, both orally in progress meetings as well as in writing deliverable reports. He/she should cooperate with the other researchers in the project, amongst others by integrating his/her results in the joint project system demonstrator. He/she should disseminate his/her work, including transfer to project partners and via publications in scientific journals and conferences.


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