What happens when GPS fails? Wi-Fi, Li-Fi, Beacons to the rescue

The Global Positioning System is a good outdoor location technology, but it is unreliable indoors. Photo: Reuters

If you ever thought that Global Positioning System, or GPS, is the only technology used to develop navigation systems and give directions, you may want to think again.

A team of researchers at the University of California-Riverside (UCR) has developed a “highly reliable and accurate navigation system” that exploits existing environmental signals such as cellular and Wi-Fi rather than GPS.

Most navigation systems in cars and portable electronics use the space-based Global Navigation Satellite System (GNSS), which includes the US system GPS, Russian system GLONASS, European system Galileo, and Chinese system BeiDou.

For precision technologies such as aerospace and missiles, navigation systems typically combine GPS with a high-quality on-board Inertial Navigation System (INS), which delivers a high level of short-term accuracy but eventually drifts when it loses touch with external signals, the UCR researchers point out.

However, GPS signals alone are very weak and unusable in certain environments like deep canyons. Second, GPS signals are susceptible to intentional and unintentional jamming and interference. Third, civilian GPS signals are unencrypted, unauthenticated, and specified in publicly available documents, making them spoofable, or prone to hacking, the researchers say.

Hence, current trends in autonomous vehicle navigation systems rely not only on GPS/INS, but a suite of other sensor-based technologies such as cameras, lasers, and sonar. “By adding more and more sensors, researchers are throwing ‘everything but the kitchen sink’ to prepare autonomous vehicle navigation systems for the inevitable scenario that GPS signals become unavailable. We took a different approach, which is to exploit signals that are already out there in the environment,” said Zak Kassas, assistant professor of electrical and computer engineering in UCR’s Bourns College of Engineering, in a 13 October statement. He led the team that presented its research ( at the 2016 Institute of Navigation Global Navigation Satellite System Conference (ION GNSS+), in Portland, Oregon, last month.

Instead of adding more internal sensors, Kassas and his team in UCR’s Autonomous Systems Perception, Intelligence, and Navigation (ASPIN) Laboratory have been developing autonomous vehicles that could tap into the hundreds of signals around us at any point in time, like cellular, radio, television, Wi-Fi, and other satellite signals.

In the research presented at the ION GNSS+ Conference, Kassas’ team showcased ongoing research that exploits these existing communications signals, called “signals of opportunity (SOP)” for navigation. The system can be used by itself, or, more likely, to supplement INS data in the event that GPS fails.

The team’s research approach includes theoretical analysis of SOPs in the environment, building specialized software-defined radios (SDRs) that will extract relevant timing and positioning information from SOPs, developing practical navigation algorithms, and finally testing the system on ground vehicles and unmanned drones.

While GPS is a good outdoor location technology, it is unreliable indoors. However, the idea to supplement GPS with other technologies for indoor location use with widely-used location technologies including Wi-Fi (wireless fidelity), Li-FI (light fidelity), Beacons and NFC (near field communication) is not entirely new.

Technologies like Beacons (such as Apple Inc.’s iBeacon) are low-cost, low-powered transmitters equipped with Bluetooth Low Energy (BLE) that can be used to deliver proximity-based, context-aware messages. They are ideal for detecting smartphones indoors, where GPS isn’t always effective, and can communicate with apps on devices when they are indoors.

NFC requires users to pull out their phones and tap onto a NFC reader, thus requiring investments in tags, readers, etc. The range, however, is limited to 20cm and less. Beacons, on the other hand, typically have a wireless range of 1m to 70m but being radio transmitters, they too are susceptible to interference.

Skyhook Wireless Inc. has a Wi-Fi-based location system, which it calls Wi-Fi Positioning System (WPS). Skyhook’s patented ‘Precision Location’ combines Wi-Fi with GPS, cell towers, IP (Internet protocol) address and device sensors to provide positioning for any device on any operating system (OS).

Li-Fi is another option. Almost four years back, Harald Haas, who was then professor of mobile communications at the University of Edinburgh and the person who coined the term Li-Fi. and Gordon Povey, now chief executive at Trisent, claimed that Li-Fi broadband can replace GPS (

Haas, now co-founder and interim chief executive officer of pureLifi—a spin-out from the University of Edinburgh—believes that light fidelity (Li-Fi)-enabled LED light bulbs can also transmit data much faster than Wi-Fi ( According to a 2012 report in UK-based newspaper Independent (, Li-Fi promised to challenge the dominance of GPS with Li-Fi LED bulbs so long as we are in the line of sight of the light source.


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