The Performance Evaluation of the QZSS Authentication Service Toward the First Drone Experiment
Takahiro Yamamoto, Kazuhiro Terao, Hidehiko Araki, Sumi Daiki, Miyamoto Sho, Kengo Takahashi, Core Corporation
Date/Time: Wednesday, Sep. 18, 11:26 a.m.
In recent years, autonomous control technologies of self-driving vehicles and drones using GNSS have been spreading in order to improve work efficiency and safety. Autonomous control requires a high level of safety in that it does not involve human operation. Therefore, it is important to prevent malfunctions due to spoofing signals of GNSS. There is a variety of anti-spoofing techniques, of which signal authentication is particularly important as an effective technique in term of certainty using public key cryptography. Japan's QZSS satellite system is scheduled to begin delivering digital signatures in 2024 to enable signal authentication functions. The digital signature is delivered in the L6 signal of QZSS, enabling signal authentication of QZSS, GPS, and Galileo. CORE CORPORATION developed the GNSS receiver Cohac? Ten++ (hereinafter referred to as Ten++), which supports QZSS signal authentication, and the drone "ChronoSky PF2-AE" (hereinafter referred to as PF2-AE) with Ten++. Through our demonstration experiment (*1), QZSS signal authentication was confirmed to be effective for drones requiring high safety.
The signal types to be authenticated by the QZSS signal authentication function are LNAV, CNAV, and CNAV2 for GPS, I/NAV, F/NAV for Galileo, and LNAV, CNAV, and CNAV2 for QZSS. The authentication confirms that the satellite clock information and satellite orbit information have not been rewritten by spoofing. Digital signatures corresponding to the authenticated signals of QZSS are embedded and delivered in each signal of QZSS, but QZSS digital signatures of GPS and Galileo cannot be embedded because they are satellites of other countries and so are delivered in the L6E signal of QZSS. Therefore, all of the above digital signatures are created by the QZSS control station, uploaded to the QZSS, and delivered to the ground. However, for GPS and Galileo, there is a 5-minute lag between the reception of the authenticated signals and the digital signature because they are created after receiving the authenticated signals from each satellite and being verified in the control station.
In September 2023, when test delivery of digital signature began, we developed and demonstrated Ten++. Ten++ is a high-precision positioning GNSS receiver compatible with RTK, CLAS, and MADOCA. Ten++ has the function of receiving and decoding the L6D and L6E signals of QZSS, and can obtain CLAS augmentation information from L6D, MADOCA augmentation information from L6E, and digital signatures. Using the acquired digital signatures, Ten++ performs positioning using only the signals that has been confirmed safe by signal authentication, and has the capability to detect and remove spoofing signals from the positioning. To compensate for the 5-minute lag, we adopted an algorithm in which the received digital signature is stored in Ten++ and reused at startup.
We have done the tests to detect spoofing signals created by a GNSS simulator. The spoofing signal was mixed with the real signal and the mixed signal was input to the receiver over the wire. We confirmed that Ten++ with an authentication function can detect and remove the spoofing signal. It outputted the correct position. On the other hand, a GNSS receiver without an authentication function outputted the wrong position or couldn’t calculate its position. In addition to the wired test, we executed the wireless test in the anechoic chamber.
Now, we are evaluating the time which the receiver needs to verify the real satellite signals. We are measuring the time required for each signal to be received and authenticated, the time required to authenticate signals of satellites visible in the sky, TTFF (Time To First Fix) and so on. Also, we are evaluating the comparison between the existed receiver without the authentication function and Ten++ with the authentication. The existed receivers have their own anti-spoofing functions. Therefore, we are trying to clarify the effect of the authentication service. In this presentation, we will describe these performance evaluation results regarding QZSS authentication service.
(*1) Cabinet Office, "Michibiki Demonstration Project 2023" CORE Corporation, ACSL Ltd., Rakuten Group, Inc.,
Successful demonstration of GNSS anti-spoofing in drone delivery
https://www.core.co.jp/system/files/2024-02/CORE_NEWSRELEASE_MICHIBIKI_DEMO_SUCCESSFUL_EN.pdf
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