Tampere University team's innovative research on Reconfigurable Intelligent Surfaces and high-altitude platforms wins 'Future 6G NTN Systems' challenge

Congratulations on the victory in the "Future 6G NTN Systems" challenge! Could you, Ayush Kumar Dwivedi, share more details about how your idea, "Enhancing HAP Networks with Reconfigurable Intelligent Surfaces," came about, and what was the main focus of your research?

– Thank you. This achievement is the result of a collective team effort. While I am pleased to discuss the work here, the credit belongs to the entire team.

– The idea emerged from collaborative brainstorming sessions with my colleague, Islam Mohammad Tanash. Islam had previous experience with Reconfigurable Intelligent Surfaces (RISs) from her PhD research under Professor Taneli Riihonen at Tampere University. My own background includes work on communication topologies for smart cities and related applications. Both of us have utilized stochastic geometry for analytical purposes in our research.

– By integrating our areas of expertise, we developed a concept that enhances Non-Terrestrial Networks (NTNs) using Low Earth Orbit (LEO) satellites and High-Altitude Platforms (HAPs) augmented with RIS capabilities. Our approach leverages the strengths of both RISs and HAPs to improve network performance and efficiency. This work proposes a futuristic communication architecture that is particularly suitable for various smart city applications.
 

How did your team come together?

– This is quite an interesting story. Our team comprises Prof. Taneli Riihonen's past, present, and future supervisees. Islam has completed her PhD with Prof. Taneli and was a PostDoc researcher at Aalto University when we started working. I have recently begun my PostDoc research with Prof. Taneli. This competition marked my first contribution to the group. Additionally, we were joined by Fatemeh Rafiei Maleki, who will be joining Prof. Taneli for her doctoral studies soon.

– The idea to participate in the challenge was floated by Prof. Taneli. Islam and I, who shared office space, discussed the opportunity and decided to collaborate. Prof. Taneli introduced us to Fatemeh, who will soon be joining the group. This collaboration gave us an opportunity to work with her early on, and it also allowed her to dive into the research and manuscript writing processes. Although we started close to the deadline, we quickly aligned on the idea and focus of the paper, which facilitated a successful collaboration.
 

Could you briefly explain what "Reconfigurable Intelligent Surfaces" are and how they relate to high-altitude platform networks (HAP)?

– Reconfigurable Intelligent Surfaces (RIS) are advanced reflective surfaces that can control and redirect wireless signals to enhance communication quality. Typically deployed on terrestrial surfaces or structures, RIS support communication by improving signal transmission. High-altitude platform networks (HAP), which use platforms like balloons or drones, provide communication services from the sky. When users cannot directly connect to HAPs, RIS can serve as an intelligent bridge, enhancing coverage and reliability.
 

What significance does this win and the development of 6G technology have for the future of satellite and space communication systems?

– The upcoming 6G technology will natively incorporate non-terrestrial networks (NTNs), such as satellites and HAPS, into its architecture. These elements are expected to seamlessly integrate with existing terrestrial infrastructure, extending communication services to even the most remote areas. Our research aligns closely with this vision. We have proposed a system concept that leverages LEO satellites and HAPS, demonstrating its feasibility for various modern applications.

– The proposed system can be effectively deployed in several use-case scenarios. For instance, in smart cities, where RISs act as passive reflectors, HAPs can periodically hover over the city to collect and offload data from densely deployed IoT sensors. In large gatherings like sporting events or festivals, where network demand spikes within a confined area, temporarily deploying HAPs with RISs on top of buildings can provide additional backhaul capacity, alleviating congestion and ensuring seamless connectivity for attendees.
 

What was the biggest challenge in this project, and how did your team manage to overcome it?

– The biggest challenge was not only conceptualizing the system but also ensuring its relevance against the backdrop of existing literature and verifying its feasibility through mathematical analysis and system simulations. We overcame this by effectively dividing the tasks among the team. Fatemeh conducted a thorough literature survey to identify relevant use-case scenarios. Islam focused on the mathematical analysis, while I set up the simulation environment to validate the analysis and generate insights. Prof. Taneli provided valuable feedback on the analysis and assisted with proofreading the manuscript. This efficient division of tasks allowed us to complete the project within the given timeframe. 


What are the next steps in your research after this win? Are there plans for further development or applications of the solution you presented? 

– Yes, this was a preliminary study of the proposed architecture, and we plan to further develop the idea. Our next steps include integrating the architecture with more advanced communication technologies as enabling solutions. We aim to address challenges such as the dynamically changing locations of LEO satellites and HAPS networks, as well as the need to support a massive number of users with varying data rate requirements. These developments will be crucial in making the proposed system more robust and adaptable to real-world applications. 
 

How do you believe competitions and awards like this one help young researchers in their careers, especially in the fields of communications and signal processing? 

– Competitions like these are highly valuable for young researchers. They offer a platform to present early-stage ideas and receive constructive feedback, helping to refine and develop those ideas further. These events also promote wider discussion and visibility for innovative concepts. Additionally, they provide opportunities to connect with like-minded individuals and engage in thought-provoking discussions. The incentives for winning are also a strong motivation to continue pursuing and developing these ideas. 
 

What was your experience like participating in the international ICCSPA conference and presenting your ideas in the workshop? 

– Unfortunately, due to the short notice after the results were announced, we were unable to travel to Istanbul to present our idea in person. Both Islam and I had prior travel commitments. As a result, I presented the work virtually at the conference. Despite the remote format, it was a valuable experience with engaging discussions and thought-provoking questions. I also attended presentations by other winning teams, which showcased a wide array of ideas across diverse themes, all contributing to the future of non-terrestrial networks. 
 

How do you envision the role of 6G and NTN (Non-Terrestrial Networks) technologies in future wireless network architectures? 

– As I mentioned earlier, the time for non-terrestrial networks has arrived. NTN networks are being natively integrated with 6G through ongoing efforts at 3GPP. We will see communication networks that seamlessly combine existing terrestrial infrastructure with emerging non-terrestrial infrastructure. Initiatives like the European Union Agency for the Space Program's (EUSPA) IRIS2 and GOVSATCOM programs are also driving the development of NTN systems. I believe it’s only a matter of a few years before services from satellites and other aerial platforms become a common part of our daily lives. 
 

Is there anything specific you'd like to share about the learning process in this project or working together with your team? 

Working on this project was an enjoyable and insightful experience. While I've had the opportunity to work with large teams during my doctoral studies, the speed at which we delivered this project was a valuable lesson. It reinforced my belief that, with effective resource optimization, we can achieve significant results in a short timeframe. This experience has been both a learning opportunity and a motivation for future projects. 
 

What is your current job description in the electrical engineering unit, and which projects are you working on? 

– I recently completed my doctoral studies at the International Institute of Information Technology Hyderabad (IIITH), India, where I focused on developing topologies and transmission schemes for satellite-based IoT networks. I have now joined Prof. Taneli Riihonen´s group as a post-doctoral researcher in the electrical engineering unit at TAU. Currently, I am working on a Business Finland project titled "Stochastic 3D Modelling of 6G Networks."