Technical Papers

TRANSFORMING THE WAY THE WORLD TECHNICAL PUBLICATION INTRODUCTION With the introduction of Maxwell™ 7 Technology, Trimble has added several technical innovations that improve the performance of its receivers. This technical bulletin provides an overview of how Trimble receivers provide protection from the increasing threat of false GNSS signals. These false or spoofed signals could potentially result in a receiver calculating positions in error by many kilometers. This is not to be confused with jamming, which also disrupts positioning by transmitting strong undesired signals that overload the GNSS receiver's RF or signal processing. However in the jamming scenario, while the receiver has difficulty calculating a position, it will generally not be in the wrong location. A separate technical bulletin will describe how Trimble Maxwell™ 7 technology helps overcome GNSS jamming signals. WHAT IS GNSS SPOOFING? GNSS receivers track low-power signals transmitted from satellites. With the availability of low- cost programmable radios it is now possible to develop a transmitter that will broadcast a spoofing signal that a receiver will use instead of the true signal. Depending on the sophistication of the spoofer, this can cause various positioning and timing errors. Although Trimble is not seeing spoofing in its high- Trimble Maxwell TM 7 Technology - Protection Against GNSS Spoofing precision applications today, such activities may increase in the coming years. WHAT IS TRIMBLE DOING ABOUT GNSS SPOOFING? Trimble receivers that incorporate Maxwell™ 7 Technology include a number of features to protect from spoofing. Maxwell™ 7 Technology is based around Trimble's next-generation ASIC, RF and processor developments. The technology provides robust precision positioning by fusing all GNSS constellation signals with additional sensor data. The defense against spoofing is currently handled at the following levels: ► Rejection of Spoofed Signals in the Digital Signal Processing (DSP) Advanced tracking algorithms detect if multiple signals are received for each satellite and ensure only the true signal is tracked. The spoofed signal generally shows as a stronger secondary correlation peak, which the tracking channel isolates and rejects from reaching the positioning algorithm. ► Satellite Data Checking By keeping a historical record of the orbital parameters transmitted by each satellite, Trimble can detect if these change unexpectedly or fall outside reasonable bounds.

• Cover