August 2025 - In this interview, Onel López, Associate Professor in Sustainable Wireless Systems at the University of Oulu, discusses his work on the foundations for 6G IoT. These involve enabling technologies for future 6G devices and infrastructure as communications networks become more decentralized, heterogeneous, and deeply integrated with sensing and computing. 6G IoT is not just about smarter devices, it is about smarter ecosystems.
Q: Would you begin with some introductory information about yourself and how you came to be based in Finland?
OL: I am originally from Cuba, where I worked as a telematics specialist for the Cuban telecommunication company, ETECSA, following my studies in Telecommunication and Electrical Engineering at the Central University of Las Villas.
After completing my master’s studies in Brazil, I moved to the University of Oulu (Finland) at the invitation of Professors Hirley Alves and Matti Latva-aho to conduct my doctoral studies and research on resource allocation for machine-type communications. In 2024, I became an IEEE Senior Member and was promoted to the role of Associate Professor. Recently, I was on a 6-month research visit to Rice University and the University of Houston in the USA.
My funded activities in Finland include: the UPRISING project on realizing a functional and competitive indoor RF wireless power transfer system; the AMBIENT-6G on energy-neutral devices and standardization efforts; the ECO-LITE project on context-aware protocols for sensing, actuation, computing, and communication in energy-natural devices; and a contribution to Hexa-X-II on low‑power/cost IoT devices and infrastructure support in the context of 6G. I am grateful to the Research Council of Finland and Horizons Europe SNS-JU for their funding support.
Q: You recently wrote about the completion of the Hexa‑X‑II work. Before we get to that, would you begin by telling us about the HEXA‑X‑II program and the University’s participation in it?
OL: Yes, you’re referring to something I published about work package 5 (WP5) of Hexa-X-II. Hexa-X-II is a major European research initiative with the goal of envisioning and developing technology foundations for 6G. It just concluded in June. The project brought together leading universities, research centers, and companies to explore what the next generation of wireless communication should look like, not just in terms of faster or more efficient networks, but also in terms of sustainability, resilience, and societal impact, and how to get there.
At the University of Oulu, and especially the Centre for Wireless Communications, we have had a long-standing commitment to pushing the boundaries of wireless research and we have had quite a history of success in this regard. So, it was only natural that we were deeply involved in Hexa-X-II. Our researchers participated in several work packages (WPs) across the project, covering topics from intelligent network architectures to device and infrastructure technologies.
Personally, I participated in WP5, which looked at enabling technologies for future 6G devices and infrastructure. This is an exciting area because it touches on many of the challenges we will face as networks become more decentralized, heterogeneous, and deeply integrated with sensing and computing.
It was a privilege to be part of a project that was not only exploring technical innovations but also helping define the role of 6G in shaping future societies.
Q: What was the scope of the work package you led?
OL: I led Task 5.4 within WP5 and served as the editor for the final WP5 deliverable, D5.5. So, I have been quite closely involved in shaping its outcomes. WP5 focused on enabling technologies for 6G devices and infrastructure. There were four tasks:
- Task 5.1 laid the foundation by defining categories of future devices, from ultra‑low‑power zero‑energy IoT nodes to advanced extended reality (XR) and sub‑THz devices, as well as infrastructure components.
- Task 5.2 dove into hardware and RF transceivers, focusing on mmWave and sub‑THz frequency bands, including energy consumption, antenna integration, and how to support joint sensing and communication. It also touched on reconfigurable intelligent surface (RIS) technologies and related techniques.
- Task 5.3 targeted system on a chip (SoC) enablers, specifically, signal processing, AI components, power management, and trusted execution features to secure future 6G platforms.
- And Task 5.4, which I led, focused on ultra-low power and cost-efficient device and communication designs. We looked at cost, power consumption, and manufacturing aspects; energy harvesting; backscatter communication; lightweight protocol design; energy-aware operation; and sustainability trade-offs in future IoT platforms.
I participated in the proposal stage and helped shape the scope of work for this WP. Within the project, this was an important WP because it provides much of the hardware-level grounding for other WPs. For example, WP4 builds theoretical models and abstractions using assumptions and data coming directly from our work. We also received important guidance from other WPs, especially on what kinds of capabilities future devices might need, or what trade-offs will be acceptable in terms of power, latency, or cost.
I believe that the project received funding and ultimately succeeded because it brought together a strong consortium and a clear, well‑structured vision. The scope covered everything from devices and hardware up to architectural enablers and societal impact. The depth and balance across layers of the technology stack and the credibility of the partners involved played a key role in securing the huge funding of just over 25 million Euros.
Q: From an IoT perspective, what use-cases and performance criteria did your team study?
OL: Our focus in Task 5.4 was specifically on the technical enablers for 6G IoT devices, particularly those aiming for ultra-low power and cost. This task had one of the broadest and most active groups within WP5, bringing together ten partners from across Europe: from Finland, we had the University of Oulu, Aalto University, and Ericsson; from France, Orange, Qualcomm, and Sequans; IMEC from Belgium; WINGS from Greece; and NXP from Germany. It was a very dynamic mix, ranging from large companies to SMEs, operators, and leading academic institutions.
We worked closely with Task 5.1, which was more focused on defining the device types and system-level characteristics, including performance criteria and envisioned use cases. That mutual coordination was essential as we needed clear targets to design around.
We studied ‘Energy Neutral’ (EN) and enhanced Low Power Wide Area (eLPWA) devices as part of our studies on 6G IoT devices. EN devices are small, ultra-constrained IoT devices that harvest energy from ambient sources like solar, thermal, RF, or vibrations, or even dedicated RF transmissions, to operate continuously, without traditional batteries. Their design prioritizes minimal energy consumption across the full lifecycle, including manufacturing with recyclable or biodegradable materials to support circularity.
EN devices are intended for low data rate applications (typically tens of kbps or even bps), with latency requirements ranging from tens of milliseconds to even minutes depending on the use case. High connection density and near-global coverage (targeting 99.9 % of landmass) are important, especially for applications like earth monitoring or autonomous supply chains.
EN devices can be used as passive and active support in several use cases. They can function as a passive form of support to track the location and movements of devices in a real‑time digital twin through external sensors. They can provide active support to ubiquitous network use cases like earth monitoring for environment protection, food production monitoring, and autonomous supply chains. In this case, they can provide near real time sensory information, improving the digital trustworthiness of the end users. There are other use cases in human centric services like precision healthcare. These will enable continuous health monitoring (outside hospitals) and optimized care. They involve the use of EN devices in body tags, and in- or on-body implants/sensors.
Privacy was a major consideration. Given the sensitivity of sensor data, our studies emphasized privacy-preserving techniques like anonymization and homomorphic encryption. When we designed our technical studies in T5.4, we constantly cross-checked against these KPIs and deployment expectations.
Q: What is different about these use cases from a 6G perspective?
OL: What stands out in these 6G use cases is that they go beyond increasing speed or reducing latency in directions that are not so apparent in today’s 5G networks and MTC devices. 6G stretches the concept of what a ‘device’ is and what it is expected to do. In 6G, devices are not just endpoints for data anymore. They are expected to sense, process, learn, and operate autonomously, all while being energy- and resource-aware. That distinction led the WP5 team, and especially within the T5.1 umbrella, to define four novel device classes, each aligned with specific demands that did not exist, or were not feasible, in 5G.
First, there are the Energy Neutral (EN) devices I mentioned before. This class is crucial for scaling sustainable deployments in remote, harsh, or maintenance-free environments like environmental monitoring, smart agriculture, or supply chain tracking.
Next, the Reliable High Data Rate with Bounded Latency (RHDRBL) devices support applications that need consistent high throughput, such as extended reality (XR), digital twins, or remote robotics, while meeting deterministic latency and reliability constraints.
Then we have Highly Reliable Low Latency (HRLL) devices, for mission-critical, safety-sensitive applications. Think of autonomous drones cooperating in real time, or robotic systems in industrial environments where even milliseconds matter.
Finally, there is the enhanced Low Power Wide Area (eLPWA) device class, which extends current massive MTC into new levels of efficiency, cost reduction, and density, still supporting mobility and some uplink capabilities but with much stronger constraints on power and device complexity.
So, in short, what is different in 6G is not just the ‘more’, it is the ‘what for’ and the ‘how’. We are designing devices for a world where communication, computation, and context-awareness are deeply intertwined, and that is both exciting and challenging.
Q: Did your studies reveal any commonalities across these device classes?
OL: In some respects, yes. For example, one fascinating cross-cutting feature in 6G is sensing. Many 6G devices, especially those in the RHDRBL and HRLL categories, are expected to natively support sensing, either by processing data locally or by collaborating with the network. That is a big leap from current systems. It opens new possibilities for integrated communication and perception within the same platform.
And of course, with all these capabilities comes a greater need for smart, secure hardware. That is where the SoC work in WP5 plays a vital role. For this, Task 5.3 explored scalable and energy-efficient SoC architectures that integrate not only signal processing, but also on-device AI acceleration and hardware-supported security, like application isolation and trusted computing concepts. These are essential to protect against misuse or attacks, especially as intelligence and autonomy moves towards the edge.
Q: How are manufacturing choices, deployment strategies, and energy/cost trade-offs shaping the design of future 6G IoT devices?
OL: That is a very relevant angle for 6G IoT devices, especially the EN ones. How a device is built and deployed is just as important as what it can do. We tackled this holistically, from sustainable manufacturing to deployment scenarios, looking at the trade-offs between energy, performance, and cost.
On the manufacturing side, we explored the use of lightweight, cost-effective materials like printed electronics. These are not only scalable and affordable, but also support circularity, enabling devices that can be recycled or even biodegrade after use. This is essential when thinking about large-scale deployments, as in logistics or environmental sensing, where billions of devices may be produced and deployed in transient roles.
When it comes to deployment, we were mainly concerned with how to ensure that these devices operate reliably, without conventional batteries, in real-world conditions. We did not limit ourselves to ambient energy harvesting but also investigated dedicated RF Wireless Power Transfer (WPT) technology. Indeed, one of the more futuristic and increasingly feasible scenarios we explored is where the network itself becomes an energy provider. Through power beacons, RIS-assisted delivery, or targeted RF charging, the network could offer energy as a service to selected EN devices. We analyzed the efficiency and feasibility of such setups, for example, looking at beamforming strategies and the harvested energy profiles over distance and frequency bands.
Of course, deploying such systems at scale requires a clear understanding of both costs and energy budgets. That is why we also included detailed cost and power modeling. For instance, in D5.5 we present an analysis comparing energy consumption across different device states (e.g., active, sleep, wake-up), and assess the impact of protocol choices, wake-up schemes, and communication strategies on both lifetime and cost. We looked at device bill-of-materials, modem-level energy consumption, and even protocol-level overheads in terms of signaling vs. payload trade-offs. These insights are crucial in designing devices that are not only technically viable but economically scalable.
So ultimately, our work pushes the idea that 6G IoT is not just about smarter devices, it is about smarter ecosystems: ones that consider manufacturing impact, that can power devices wirelessly, and that optimize for long-term sustainability and cost-efficiency. This systemic view is what 6G requires if we are to move beyond isolated innovations and toward truly scalable, intelligent infrastructures.
Q: The work scope also included some proof of concepts (PoC). What issues did these PoCs address and what were your findings?
OL: The PoCs translated some of our research into demonstrable systems. An early PoC focused on EN devices, also called zero energy devices (ZEDs), using ambient backscatter communication. These devices operate without batteries, harvesting energy from ambient light and communicating by modulating reflections of commercial LTE signals. We demonstrated data transmission using both LTE downlink and uplink signals. We also implemented techniques to align the timing and frequency of the backscattered signals with those of the LTE infrastructure. The performance was encouraging, showing robust bit-error rates even under realistic indoor multipath conditions.
Building on that, we then explored indoor localization using ZEDs. The showcased system uses passive backscatter tags with location-specific signatures, enabling a reader (like a smartphone) to infer the device’s position without GPS or active transmissions. This approach is especially promising for applications like smart buildings or supply chain tracking, where long‑term maintenance‑free operation is critical.
Finally, another PoC targeted an XR use case. XR devices are among the most demanding in terms of latency, reliability, and processing power. This PoC focused on a system architecture that offloads computation from XR headsets to nearby edge nodes, while maintaining ultra-low latency and ensuring trust through secure hardware partitioning.
Together, these PoCs validated several key ideas from our work. For EN devices, we demonstrated that maintenance-free, battery-less IoT is achievable with smart energy management and ambient signal reuse. The XR PoC highlighted how it is possible to combine edge computing, low-latency links, and secure hardware support to enable future immersive applications on lightweight, wearable devices.
Q: What plans do you have to carry this work forward?
OL: That is a great question, and honestly, we are just getting started. What we achieved in Task 5.4 of Hexa‑X‑II laid important foundations, but many challenges remain before EN IoT becomes a really impactful reality. There are still open questions in device controllability and dependability, protocol optimization, RF energy delivery, hardware/software co-design, and integration with the broader 6G architecture.
At the same time, 6G standardization is only beginning to take shape. For example, 3GPP has introduced a new device category called ‘Ambient IoT’, which is remarkably aligned with the EN device class we worked on. This is encouraging; it shows that what was once a forward-looking research idea is now entering the global agenda. However, there remains a lot of research, engineering, and validation work to bridge the gap between concepts and real-world specifications.
To continue this journey, several of us from the original T5.4 team brainstormed and developed a new proposal that is now officially underway as the Ambient-6G project. The project is dedicated to the study and development of EN IoT systems, pushing the boundaries of what can be achieved and influencing standardization activities. It is an ambitious and focused initiative, bringing back many Hexa‑X‑II partners and fresh faces to bring new ideas and frameworks.
Parallel to that, I am also leading my own research project funded by the Research Council of Finland ECO-LITE, which is more academic in nature. In ECO-LITE, we are exploring synergic and context-aware protocol design for EN IoT. The goal is to rethink what information (and how to obtain it) these EN devices and networks can exploit to make system operation more dependable. We are also thinking about how communication, sensing, actuation, and computation protocols should operate when energy is not always available. In other words, how should the devices adapt, learn, and remain useful in a highly constrained, fluctuating energy landscape?
So yes, there is still a lot of work ahead and it is exciting. We are committed to continuing this line of research, both by contributing to 6G standards and by shaping the technologies that will support massive-scale, sustainable IoT in the coming decade.
Q: Are there any other thoughts you wish to add to our discussion?
OL: If there is one point I can add, it is about the need for deeper system-level thinking. Many of the challenges we face, especially with EN IoT, simply cannot be solved in isolation, as they sometimes can for more traditional, less constrained devices. In these systems, even small inefficiencies due to poor coupling between layers or protocol mismatches can render a device or application inoperable. Resources like energy and computation are not just limited, they are fragile and variable. Protocol design is tightly constrained by hardware capabilities; dependability requires context-awareness; and all of it depends not only on current energy availability, but on anticipated future energy budgets. This means we must think beyond isolated optimizations and focus on holistic, adaptive co-design.
I believe 6G IoT systems in the future will require much tighter integration between hardware, communication, computation, and intelligent orchestration. It is a significant shift. I would love to see more attention to this direction in both research initiatives and standardization efforts. It is where the next breakthroughs may happen.
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