Turning Everyday Cell Phones into Search-and-Rescue Beacons

“It’s profound,” says Tim Durkin, an emergency medicine physician and search-and-rescue program coordinator at Colorado Highland Helicopters. “The aircraft enters the canyon, and immediately you acquire a signal. Within a minute and a half, you’ve geolocated someone within meters.”

This rapid location capability represents a revolutionary advance in search-and-rescue technology. Traditional search methods have limitations. Search dogs are heavily dependent on environmental conditions, such as wind and humidity. Infrared cameras can detect body heat, but not through dense tree cover. Even visual searches from helicopters often fail to spot people wearing earth-toned clothing against natural backgrounds.

The system essentially turns a rescue helicopter into a mobile cell tower. After installation, Lifeseeker’s hardware connects to three antennas—two cellular and one GPS—and creates a signal that any active phone in the search area will attempt to connect to. The system rejects all other phones and only connects to the device it is specifically searching for, thus protecting the data of other phones in the immediate area. Using sophisticated time-of-flight analysis and signal processing powered by MATLAB^®, the system can quickly triangulate the location of a lost person’s device, even in areas with no cellular coverage.

Despite its technological sophistication, Lifeseeker is simple to deploy. “It’s a plug-and-play type of deal,” says Durkin. Someone on the search-and-rescue team can install the entire system in a helicopter in three to five minutes, requiring just four cable connections. The interface runs on any tablet through a Wi-Fi^® connection, displaying data in a format familiar to pilots and search teams. When emergency services provide a missing person’s phone details, teams can program the system to focus solely on that device, filtering out other cellular signals in the search area.

CENTUM, the Spanish company behind Lifeseeker, began developing the tool in 2011 with a visionary idea: turning mobile phones into emergency beacons. The founders believed the market was ready for airborne search-and-rescue solutions but discovered that search-and-rescue organizations weren’t yet aware of cellular technology’s potential.

Early prototypes faced another significant challenge: the rapid evolution of cellular technology. CENTUM’s initial system, designed for 2G networks, was nearly obsolete by the time it was ready, as 3G networks were becoming prevalent. This experience highlighted a unique challenge CENTUM would need to navigate: bridging two very different technological worlds.

“We are part of the telecommunication sector, which evolves superfast, but we are also part of the slow aviation sector, where safety is the top concern and performing any change is painful for aircraft builders and avionics integrators,” says Brais Sánchez Rama, technology manager at CENTUM.

To stay ahead of rapid cellular evolution while meeting rigorous aviation requirements, three engineers work on early-stage prototyping of this engineered system, using an array of simulation tools to overcome the challenges of detecting and localizing cell phones across different cellular generations and varied terrain. The technology monitors the state of the commercial cellular network within search areas using specific phone identifiers from emergency services and cellular carriers. Once these identifiers are input, the system can detect target phones and analyze cellular signals to estimate a person’s position—all while accounting for variables such as aircraft movement and speed, weather conditions, and radio propagation effects coming from the wireless network.

The development process starts with extensive simulation. The team uses MATLAB and Simulink^® to model how different cellular signals behave in various environments. This virtual testing ground allows them to identify design failures early and optimize their geolocation techniques before moving to field trials. One of the biggest technical hurdles was ensuring the system could work with any phone.

The team leverages more than a dozen specialized toolboxes throughout development, including Communications Toolbox™, LTE Toolbox™, and 5G Toolbox™ to generate, modify, and decode signals across generations. Signal Processing Toolbox™ and Radar Toolbox help optimize processing methods. RF Toolbox™, Antenna Toolbox™, and Phased Array System Toolbox™ emulate hardware effects on the signal processing chain, which is crucial for understanding how physical factors impact detection capabilities.

Mapping Toolbox™ and Navigation Toolbox™ are key to developing geolocation algorithms that accurately pinpoint the missing person’s location on the map. Knowledge and solutions derived during the system simulation stages, which rely on MATLAB, are then transferred to production. The system allows search-and-rescue teams to use a web-based interface easily operated on a tablet or laptop.

Before deploying updates to Lifeseeker, the team validates their algorithms in the laboratory using software-defined radio devices. These hardware pieces, controlled through Communications Toolbox, bridge the gap between simulation and real-world performance.

With reports of over 220 successful missions in the past year, and many more unreported due to privacy restrictions, Lifeseeker’s impact has already helped over 40 clients in more than 20 countries. One mission with Rega, an air rescue service in Switzerland and Liechtenstein, particularly demonstrates the system’s life-saving capabilities.

After about 10 minutes, the driver’s cell phone connected to the Lifeseeker system. After a few minutes, the rescuers precisely located the phone: The vehicle had gone over an embankment and crashed in the forest below. The impact had trapped the driver inside with her phone out of reach somewhere in the wreckage. Lifeseeker enabled them to find the wreckage in time to get the victim to the hospital, where she successfully recovered.

As CENTUM looks to the future, it’s preparing for the next generation of cellular technology. 6G will bring new challenges and opportunities, particularly through its integration of artificial intelligence. “AI is going to be fundamental in 6G,” says Sánchez Rama. “Radio systems will be expected to have the ability to learn from one another and their environments.” The team anticipates adapting their systems to this new AI-based paradigm using Deep Learning Toolbox™.