In today’s urban centres, we are surrounded by countless wireless signals from smartphones, Wi-Fi routers, and even smart devices such as streetlights. With every new device, the demand for radio frequency (RF) spectrum grows, or in other words, as our reliance on wireless communication intensifies, the available RF spectrum is becoming increasingly crowded. Efficiently monitoring and managing this spectrum is vital for maintaining seamless communication. However, traditional methods for spectrum monitoring are expensive and cumbersome.

“ORAN-Sense: Localizing Non-cooperative Transmitters with Spectrum Sensing and 5G O-RAN” is a publication by Yago Lizarribar, Roberto Calvo-Palomino, Alessio Scalingi, Giuseppe Santaromita, Gerome Bovet, and Domenico Giustiniano.

The Need for Efficient Spectrum Monitoring 

This scarcity of availability on the spectrum has significant implications: unauthorised or malfunctioning transmitters can cause interference, disrupting essential services such as emergency communication systems, GPS signals, and commercial networks. Additionally, unauthorised spectrum usage can pose security risks, from illegal broadcasts to potential espionage activities. Efficient spectrum usage is crucial for ensuring that the ever-growing number of devices can communicate without interference. Think about the chaos that ensues during a major event like the Super Bowl. Thousands of devices are vying for bandwidth, leading to potential interference and communication breakdowns. Efficient spectrum monitoring can help mitigate these issues, ensuring smooth operation of all wireless devices.

Introducing ORAN-Sense

ORAN-Sense has been developed, a groundbreaking approach that leverages the power of IoT and 5G technology to monitor and localise non-cooperative transmitters efficiently and cost-effectively. It is is a novel system designed to revolutionise spectrum monitoring. It integrates low-cost IoT sensors into the 5G Open Radio Access Network (O-RAN) infrastructure. This innovative approach promises to make spectrum monitoring more efficient and cost-effective.

Fig. 1: Proposed architecture for ORAN-Sense, a Time Difference of Arrival (TDOA)-based localization approach of noncooperative transmitters that can be embedded in O-RAN by using its open interfaces.

Cost-Efficiency and Integration with 5G O-RAN

One of the key innovations of ORAN-Sense is its cost efficiency. The system utilises inexpensive IoT devices such as Raspberry Pi and Software Defined Radios (SDRs) to create a network of spectrum sensors. These sensors are small, cost-effective, and easy to deploy. Imagine using inexpensive webcams to create a city-wide surveillance system. Each webcam captures video footage, which is then analysed centrally. Similarly, IoT sensors in ORAN-Sense capture RF signals for analysis.

Fig. 2: The RU is comprised of a Raspberry Pi and an RTLSDR

ORAN-Sense also taps into the 5G O-RAN infrastructure, which is already maintained by network operators. This integration ensures that the system benefits from the reliability and coverage of the 5G network. Think of adding smart sensors to a well-established public transportation network. The sensors benefit from the existing infrastructure, making the overall system more efficient and reliable.

The Technology Behind ORAN-Sense

To understand the magic behind ORAN-Sense, let’s break down its process. The system employs low-cost SDRs that often suffer from clock drifts, affecting frequency measurements. ORAN-Sense uses correction algorithms to adjust for these drifts. Accurate time synchronisation is achieved using the Network Time Protocol (NTP) and reference signals, eliminating the need for GPS. The system then determines the location of RF signals using Time Difference of Arrival (TDOA) and multilateration. TDOA calculates the time difference in signal arrival at various sensors to estimate the signal source’s position, while multilateration uses the TDOA data to triangulate and pinpoint the location of the non-cooperative transmitter. Consider how GPS systems determine your location by measuring the time it takes for signals from multiple satellites to reach your device. Similarly, ORAN-Sense determines the location of RF signals using TDOA and multilateration.

Fig. 3: Effect of multipath on cross-correlation between 2 signals. On the left, we have the autocorrelation of each one. The signal affected by multipath will present multiple peaks. On the right is the cross-correlation between both. If the indirect path is stronger (as in this case), we might select the erroneous peak (instead of the one at 0 µs), leading to higher errors in the location estimation.

Real-World Deployments and Results

ORAN-Sense has been deployed in two European cities, demonstrating impressive localisation accuracy. IoT sensors were strategically placed across the cities, integrated with the 5G network. The system achieved localisation accuracies within tens of meters, validating its feasibility in real-world scenarios. Imagine a city like London deploying ORAN-Sense during major events like the New Year’s Eve fireworks. The system could efficiently monitor the spectrum, ensuring that no unauthorised broadcasts disrupt emergency communications or public broadcasts.

Future Implications and Scalability

ORAN-Sense is set to transform how we monitor and manage spectrum usage. Its reliance on low-cost IoT devices makes it easily scalable across large areas. By leveraging existing 5G infrastructure, it significantly reduces deployment and

maintenance costs. Enhanced localisation accuracy ensures efficient monitoring and quick identification of unauthorised transmitters. Ongoing work aims to improve the accuracy and robustness of the system, with plans to expand deployment across more cities and regions, enhancing global spectrum management. Picture a future where ORAN-Sense is deployed globally, ensuring seamless communication during international events like the Olympics. It would provide real-time monitoring, ensuring that every wireless device operates smoothly without interference.

In a nutshell

ORAN-Sense showcases the potential of integrating IoT and 5G technologies to tackle the challenges of spectrum monitoring. As we move towards a more connected world, innovative solutions like this will be key to ensuring efficient and effective use of our wireless resources. As we embrace the future of wireless communication, it’s crucial to support and invest in technologies like ORAN-Sense. They promise not only to enhance our connectivity but also to safeguard the RF spectrum that enables a significant amount of digital connectivity.