Prof Bhavani Shankar; recently had the opportunity to speak with Prof Bhavani Shankar, head of the Signal Processing Applications in Radar and Communications (SPARC) research group at the Interdisciplinary Centre for Security, Reliability and Trust (SnT) at the University of Luxembourg (

Prof Shankar's research interests include mathematical modelling as well as real-world applications such as the optimisation of multiple-input and multiple-output (MIMO) communication systems, automotive radio detection and ranging (radar) and array processing, polynomial signal processing, satellite communication (SatCom) systems, resource allocation, game theory and fast algorithms for structured matrices.

With 5G resources and application on the horizon, coupled with space communications (like a telephone call) and Earth observation (like Global Positioning System - GPS) integrated applications, there are enormous possibilities ahead, but one of the key challenges is to collect, analyse and process the exceptionally high amount of signals in a fast, reliable, efficient and secure way. This not only means optimisations in signal process algorithms but also optimisations between communication systems, real-time decision making, on-board problem-solving, and much more. Through MIMO, in other words, using multiple transmission and receiving antennas, one can increase the capacity of a radio link based on multi-path propagation, the backbone of today's everyday wireless communication, like Wi-Fi and Long Term Evolution (LTE) applications.

Together with Prof Björn Ottersten, Director of SnT, Prof Shankar's project was recently awarded a three-year grant from the European Office of Aerospace Research & Development, part of the US Air Force Office of Scientific Research, for civilian applications and challenges associated with cognitive radars (discussed below). Please tell us about your research interests in signal processing and satellite communications, and how these have evolved over the years?

Prof Shankar: My research interests in signal processing started with my Masters at the Indian Institute of Science (IISc). I enrolled in the Master of Engineering (ME) in Signal Processing (SP), then a very happening field. The mathematical aspects related to Signal Processing motivated me to take this new course in ME. The training and the ambience at IISc really motivated me to pursue academics, particularly in Signal Processing. When I moved to Luxembourg, SnT was in the process of creating a partnership with SES in the field of satellite communications. Being one of the early researchers here at SnT, and the new challenges in a novel system led me to work on satellite communications. I have been employing signal processing aspects in most of my research including satellite communications. I have also moved on to research in radar signal processing, again motivated by a partnership with another Luxembourg firm, IEE. The fundamentals of SP from IISc are being also applied here.

My research has evolved from being the single contributor on a project to the head of one of SnT’s research groups. What are the new and upcoming challenges in signal processing and satellite communications field that need immediate attention?

Prof Shankar: Satellite communications is very often seen as an alternative infrastructure to cellular communications. However, satellites are much more than that. Getting this message across is important so that mobile operators see satellite systems as complementary and not a competitor. When it comes to satellite systems providing support for mobile networks, SP plays an important role. Cutting-edge SP supports efficient communication links for the multiple constellations using the on-board processing. This concept, which is evolving, offers significant opportunities for the satellite communications industry. Given that space is one of the main focus areas of Luxembourg's government, how did your research align with this and how has this shaped your research at SnT?

Prof Shankar: SnT was created with the aim of furthering the focus areas of Luxembourg in the fields of information and communications technology (ICT). What a lot of people don’t realise is that satellite communication is a key enabler of ICT and Luxembourg has a world leading satellite operator, SES. Therefore, SnT has a natural role to play in this sphere, which started with our partnership with SES. Since then we have expanded our activities even further and now multiple research groups at SnT are focused on other aspects of the space ecosystem, including space resources and interstellar exploration. We should be highly indebted to the Luxembourg government and the National Research Fund (Fonds National de la Recherche - FNR) for supporting our European Space Agency (ESA) and fundamental research projects, and also SES for putting SnT in the ecosystem. These encouraging factors, aligned with my interest in satellite communications, shaped my research. SES is one of the global players in satellite communications with several constellations planned. Is SnT, especially your group, involved in any research with SES or other private satellite companies?

Prof Shankar: We have a long-standing partnership with SES, which has been very successful. Many researchers have moved on to employment with SES following their time at SnT; in fact, my first co-advised student at SnT was one of the first in this list. We also have an Industrial Partnership Block Grant (IPBG) project with FNR that acknowledges the long-standing partnership. Our partnership with SES is rather open in terms of collaboration with other actors. The group has worked with manufacturers, ground segment operators and even other satellite operators. You are part of the prestigious European Research Council (ERC) advanced grant AGNOSTIC, an ongoing project at SnT. Please tell us more about the "situation awareness" and "cognitive radar" concepts, and how does it affect the general public?

Prof Shankar: It was a great experience working with our director Prof Ottersten on this ERC grant. I am very glad that we received this grant. Situational awareness is about being aware of what is happening around you in terms of where you are, where you are supposed to be, and whether anyone or anything around you is a threat to your health and safety. Situational awareness involves understanding of the environment effectively and cognitive radar is a means for that. In cognitive radar, the sensing of the environment is made intelligent with intelligence embedding in the radar. One example is the radar beam following a target; this involves identifying the target first, figuring out the direction and velocity of its motion, and adjusting the illumination to follow the target. In this case, the radar has some cognition of the environment and uses this cognition to adjust the illumination pattern. This helps in the easier and faster response of the radar. A very good application is tracking the elderly in indoor environments in a privacy preserving mode. The radar can learn the presence of static, uninteresting objects in the scene (like the chair, table etc.) and focus on the subjects being monitored as they walk around (more like following them - that process itself has a cognitive interpretation as to how and when to follow). Moreover, the radar images have no semantic information and hence are privacy preserving. Could you please elaborate on real-time multi-target scene-adaptive radar tracking, for example used in automated driving, and how your research is contributing in this field?

Prof Shankar: In a typical automotive environment, the number of targets in the road scene keeps changing continuously; these include other vehicles and road side structures. In autonomous driving, the car needs to ascertain if any of these targets are a threat to the driving condition and if so, how to avoid them. This would need a tracking of the targets to understand, e.g. if they are moving away or towards you. Such a tracking procedure needs to be adaptive, e.g. targets vanish from scene, new targets appear, etc. This results in the multi-target scene-adaptive radar tracking. What has been your most memorable real-life research application to date?

Prof Shankar: The ongoing work on vital sign monitoring using radar is the most memorable one as it applies directly “to the heart”. In this project, we are interested in measuring the heart rate and breathing of neo-natals, elderly and vulnerable people in a non-invasive, non-contact mode. This offers significant flexibility and comfort to the monitored people without compromising on the accuracy. Please tell us more about the SnT spin-off Databourg with which you are closely related with.

Prof Shankar: I was the co-supervisor of Dr Ahmad Gharanjik, the founder of Databourg. We started off with a FNR Proof of concept on the use of satellite signals to estimate rainfall rate and generate rain maps. This opportunistic sensing allows for dense sampling of the rain field and offers better accuracy and temporal resolution than a weather radar or rain gauge. We are now in a partnership exploring new Machine Learning algorithms for rainfall rate. I am happy to mention that the Post doc working on this collaborative project obtained the Young Researcher award at the recently concluded International Union of Radio Science (Union Radio-Scientifique Internationale - URSI) conference. Today's world is already heavy on data and the future communications network will be even more data intensive. How do you think this will affect performance, energy efficiency and limited bandwidth usage without compromising security in future?

Prof Shankar: There will always be two facets to the use of data intensive methods: the advantage where modelling is intractable, while the disadvantage would be a guarantee on the quality of the result. However, going by the developments, the advantages seem to offset the disadvantages and more and more systems are increasingly using data-based methods to achieve the system objectives. In this context, we have taken the path of augmenting data driven approaches with model based to overcome the shortcomings. One field where we are in debt with regards to data is the civilian applications of radar. Satellites are getting smaller and smaller, and now more purpose-built, which also means that purpose-built signal processing needs will evolve in future. How do you see these purpose-built, limited capability space communications evolving in the future?

Prof Shankar: It seems to be following the terrestrial trend, big base stations to small cells with micro and pico base stations. Unmanned aerial vehicles (UAVs) and High-Altitude Pseudo-Satellite (HAPS) missions are being flown for particular objectives. There is a significant push in SnT on the cube-sats as well. I see a great potential towards resilient and ubiquitous connectivity provided some problems like scalability are solved. With several private players in space communication and some now offering exciting new products and possibilities, how do you believe the future in space communications will evolve? Will there be personalised space-based communications?

Prof Shankar: The idea is to use a connectivity device that offers required quality of service by using any of the communication modes; the user is agnostic to this selection, be it satellite or terrestrial. In this utopian image, I see a future where there is no distinction between satellite / terrestrial communication as far as the user is concerned and both form different embodiments.