Resilient PNT based on 5G broadcast

Last Updated: 21/02/2023 13:05     Created at: 21/02/2023 13:03

Final Presentation of NAVISP Project EL2 112 now available:

On Tuesday, February the 15th, 2023, Rohde & Schwarz GmbH & Co. KG presented the results of the NAVISP project “Resilient PNT based on 5G broadcast”. The presentation was very interesting and about 100 people from industry and research institutes followed it!

Global Navigation Satellite Systems (GNSS) like Galileo play a crucial role in providing position and timing services to various economic sectors today. However, events such as natural disasters or human interference can lead to disruptions in GNSS signals, potentially causing economic losses worth billions of dollars, such as disruption of telecommunication networks, financial transactions, and port operations. Therefore, it is advisable to develop a GNSS backup system that can ensure availability of services in the event of such outages. To create a resilient backup system, several factors need to be considered, including the signal power, susceptibility to space weather, and dependence on external infrastructure like the power grid. Additionally, the backup system needs to be dispersed, using a different frequency and transmitter location, ideally outside of the MEO orbit. However, any such backup system must also be cost-effective to deploy and maintain.

In response to this challenge, Rohde & Schwarz has developed a demonstrator of a GNSS back-up system that utilizes existing terrestrial TV/Radio transmitters. To optimize the system, they focused on enhancing the synchronization between the transmitters and added the special positioning reference signals, UTC time, and transmitter locations to the signals of the 5G broadcast transmission. As these transmitted signals are no longer just a "signal-of-opportunity" but are now fully functional navigation signals. With this backup system, if the GNSS signal is disrupted, the 5G broadcast transmission signals can provide positioning and timing information to users, helping to ensure the continuity of critical services and and  to mitigate the economic losses that can result from GNSS signal disruption .

In order to make the project both cost-effective and sustainable, the team took several approaches. First, they leveraged the existing infrastructure for TV broadcasting, including reusing towers, amplifiers, frequencies, and antennas for timing and navigation purposes. Second, they utilized the worldwide 5G Broadcast standard. Their main goal was to improve jitter of TV transmitters to nano-second level, while also synchronizing the transmitters and build a test receiver. They reduced the TV transmitter jitter from 30 ns to 4 ns. Finally, they demonstrated that the concept is working in a lab environment as well as in the field. 

Thanks to the support of NAVISP, Rohde & Schwarz GmbH & Co. KG developed an alternative back-up system as a second source for timing. The system offers in a static scenario an accuracy within target, and in moving scenarios less accuracy, presumably due to the multipath effect on test receiver. Since most of the targeted applications are relying on the timing part of GNSS, this can be replaced by this alternative back-up system. 

To make the system operational and bring the product to the market, it is suggested to invite Broadcast Network Operators to upgrade transmitter sites in regions where all frequencies for DVB-T/T2 are not currently used, while also inviting chipset and end-user equipment manufacturers to support 5G broadcast navigation signal. Initially, the primary focus could be on distributing a precise time signal, while navigation support could be extended later. Additionally, operators of critical infrastructure can be invited to use alternative time sources.

The project was part of NAVISP Element 2, which aims to maintain and improve the capabilities and competitiveness of the participating States' industry in the global market for satellite navigation and, more broadly, PNT technologies and services.

More detailed information can be found in the slides of the Final Presentation.