An innovative and cost-effective Galileo signal receiver designed to simplify the use and speed-up uptake of Galileo navigation services has won the European satnav Oscar.
Developed by Airbus engineers, the receiver offers considerably higher levels of security and reliability than rival system GPS while using a comparatively simple system architecture.
“The navigation messages of the Galileo Public Regulated Service (PRS) signals are highly encrypted, so that a valid PRS key and an implementation of the respective crypto-algorithms in a so-called Security Module are required in order to make use of these signals,” explained Wolfgang Kogler, an engineer at Airbus Defence and Space and one of the inventors of the system.
“The Security Module adds significant complexity to a PRS receiver, and the need to handle the PRS keys renders it very complicated for staff of public authorities and organisations (like police and fire brigades) to use PRS receivers. That’s why we focused on streamlining the system, developing a special network architecture that allows us to simplify the end-user receivers.”
Instead of having a Security Module integrated into every individual end-user receiver, the concept – developed by Kogler and his colleague Jan Wendel – relies on complex assistance servers and secure communications links.
The assistance server, equipped with a complete PRS receiver with a Security Module, receives the satellite data and transmits them to the users via the secure links. The end-user receivers thus don’t need to be equipped with the Security Modules while maintaining the exact same level of security as the primary receivers.
“A convenient configuration would work as follows: The assistance server provides to the user receivers a snapshot of e.g. 10 ms duration of PRN ranging code chips modulated with the encrypted message symbols, shortly after these have been received from the satellites,” said Kogler.
“As soon as the modulated PRN ranging code chips arrive at the user receiver, the user receiver constructs replicas, correlates them with the previously recorded samples, and obtains relative data in a process that is comparable to a fine acquisition.”
The Galileo Public Regulated Service, providing data about position, time and speed, is only available to authorised end-users including police departments, fire brigades, broadcasters or public authorities. The system serves as a back-up in situations when the more commonly available GPS service is compromised.
“The number one advantage of Galileo’s Publicly Regulated Services over GPS is that it can’t be spoofed that easily,” said Jan Wendel.
“In a common GPS receiver, the structure of the signals used is publicly known, so that it is possible to generate false satellite signals that appear legitimate to mislead a receiver and make it report a false position and time. Due to its encryption, this is not possible with Galileo PRS.”
Apart from being spoof-proof, Galileo is also more resilient against solar storms that could commonly disrupt GPS services.
The technology, promising to make Galileo services more convenient, has won the €20,000 grand prize as part of the European Satellite Navigation Competition 2014.
The inventors said the simplicity of the end-user receiver as well as its relatively lower price would hopefully attract more customers to Europe’s very own navigation system – a costly project, which has struggled with multiple drawbacks since its conception in the early 2000s.
In August this year, the first two Full Operational Capability Galileo satellites to have been launched ended in incorrect orbits after a malfunction of a Russian rocket.