OneNav L5-direct navigates through GPS interference in field trial

For the first time, the oneNav L5-direct receiver was flown on a UAV through a simulated electronic warfare GPS signal interference field. The assessment took place Feb. 12 at the Emerging Technology Lab at U.S. Special Operations Command (USSOCOM). This non-classified evaluation replicated battlefield conditions, including variable speeds, altitudes, maneuvers and robust L5 signal interference.

Assessment Setup

The assessment included two GNSS devices secured to the UAV, an onboard navigation computer and an onboard interference device. Two additional interference sources were located on the ground.

The onboard navigation computer integrated data from both GNSS receivers to determine and maintain the vehicle’s position and guide its movement. GNSS 1 was a competitor L1/L5 dual-band receiver that uses the L1C/A signal for initial acquisition before adding L5 signals. GNSS 2 was the oneNav L5-direct receiver, which exclusively utilized modern L5-band signals for both acquisition and tracking.

Test Conditions and Results

The in-flight assessment, conducted on a UAV under real-world dynamic and RF interference conditions, demonstrated that the oneNav L5-direct receiver operates independently of legacy GNSS signals such as L1 and L2. While conventional dual-band receivers require L1 acquisition before transitioning to L5 tracking, the oneNav solution used only modern L5 signals for both functions6.

The Emerging Technology Lab implemented comprehensive RF interference protocols, including both ground-based and airborne signal interference across multiple L5 frequencies. The oneNav L5-direct receiver maintained tracking capabilities during L5/E5a signal interference centered at 1176.45 MHz. This performance is attributed to the receiver’s wideband RF front-end architecture, which enables simultaneous processing across an extensive frequency range. The system leverages Galileo’s dual sideband configuration (E5a and E5b), automatically transitioning to E5b when E5a experiences interference—a feature unique to the oneNav technology. A brief six-second delay was observed during this transition, reflecting a three-second lock loss on E5a followed by a three-second acquisition of E5b. The ability to track E5b signals, despite a 10 dB power differential, highlights the receiver’s sensitivity.

Key Findings

• The oneNav L5-direct GNSS receiver acquired, tracked and provided location data to the drone flight computer under actual flight dynamics and through L5 band signal interference.
• Direct acquisition and tracking using only L5-band signals was demonstrated, confirming immunity to L1 signal interference.
• The receiver demonstrated resilience to L5 in-band signal interference at typical electronic warfare power levels, quickly adapting by switching to the E5b sideband when E5a was disrupted.
• The receiver maintained stability and responsiveness when both E5a and E5b sidebands were blocked.
• Continuous tracking functioned well with the BeiDou constellation off and the almanac on or off6.

Technical Background

The oneNav L5-direct technology was originally developed for consumer applications such as wearables, phones and surface vehicles. Its adaptability allows for rapid customization and deployment across a range of platforms, including those requiring robust performance in challenging environments.

Because the L5-direct receiver uses signals exclusively within the L5 band, it can leverage the advanced features of these signals. L5-band signals offer greater power and increased resistance to RF interference compared to L1 signals. Industry experts, including Prof. Brad Parkinson, recognize the advantages of L5-only receivers for jam resistance.

Currently implemented on FPGA architecture, a future L5-direct ASIC is expected to deliver performance improvements, including enhanced acquisition and tracking capabilities.