WP8 – Open field experiments

One of the final aims of the GATEMAN project was the validation of the detection and localization algorithms in open-field experimentation campaigns. The field experiments took place at Instituto Tecnológico “La Marañosa”, which belongs to the Spanish Department of Defense managed by INTA (Instituto Nacional de Técnica Aeroespacial).

Dates allocated and dedicated to perform the open-field experiments were:

• 27^th August 2019. Spoofing tests completed.
• 29^th August 2019. Jamming tests partially completed and some spoofing tests repeated.

Two areas were selected to perform these field experiments. They were chosen to ensure visibility from the interference source (BaseTx) and because a vehicle with the demonstrator could move in these areas:

• Location of the interference source (BaseTx). WGS-84 coordinates: 40°16’23.93″N        3°33’55.30″W
• Zone Z1. Straight trajectory within 1200m from the source.
• Zone Z2. Curve trajectory within 100m from the source.

Description of demonstrator

The Demonstrator is a system composed of hardware and software used during the open-field validation tests . Its purpose is to be a full-validation platform for the detection and localization algorithms developed in GATEMAN either for jamming or spoofing. A laboratory verification was already completed for these algorithms, including not only simulations but hardware-in-the-loop, achieving results closer to the reality.  The goal of the Demonstrator was to go one step further, completing the validation in real conditions (i.e. open-field with radiated interferences) and without simulated data (i.e. data recorded will be processed, dealing with clock bias, calibration needs…). A brief description of hardware and software components used in the open-field experimentation campaign is given below. The demonstrator can be divided in the following elements:

Interference source – Jamming and Spoofing (Configuration 1)

The following components shown below were used to generate the jamming and spoofing GNSS interference:

Interference source – Jamming (Configuration 2)

A second configuration was used in order to ensure an appropriate performance for large distance test cases, providing a directive radiation pattern that transmitted a more powerful jamming interference than the previous (Configuration 1).

Interference source – Spoofing (Configuration 2)

Also for the spoofing interference source a second type of transmitter was used:

Receiver platform – Jamming

The receiver platform intends to emulate the behaviour of an aircraft, where the jamming & spoofing detection and localization system will be installed. The following components constitute the platform to receive the jamming interference in order to record the IQ samples that were post-processed for the DOA estimation:

Receiver platform – Spoofing

The components shown below receive the GNSS interference to detect and to estimate the direction of arrival of the spoofing source:

Antennas baseline

The same baselines between antennas was used for jamming and spoofing to simplify the installation during the trials. According to the results of spoofing presented in project deliverable D4.2 , the preferred configuration for the estimation of direction of arrival (DOA) in the presence of spoofing are orthogonal baselines where shorter distance ranges between 1 and 1.5m and longer around 2.5m. The orthogonality of the baselines is assumed in the algorithms, and therefore it was maintained. Therefore, the antennas baselines in the demonstrator are defined to meet the restrictions of spoofing algorithms.

 Description of scenarios

Jamming scenario

This scenario checks the capabilities of the demonstrator for jamming detection and localization. The AM-Tone was the jamming signal used in this scenario.

The Jamming scenario is made of these elements:

• Jamming interference source: This element creates and radiates the jamming signal (AM-tone).
• Receiver platform: This element receives and records the raw IQ samples.
• Localization (Post-processing): Raw IQ samples are post-processed with the TAU software in order to obtain the azimuth (direction of arrival of the source). Then source localisation algorithms developed by GMV make use of the direction finding results and the position of the receiver.

Spoofing scenario

This scenario checks the capabilities of the demonstrator for spoofing detection and direction finding. The Spoofing scenario is made of these elements:

• Spoofing interference source: This element creates and radiates the spoofed GNSS signal. The spoofed signals specified for this scenario will be generated through different methods (see table below), according to the transmitter configuration type.
• Receiver platform: This element receives and records the GNSS observables (e.g. pseudoranges, carrier phases, CN0…).
• Localization (Post-processing): For each test of this scenario, we have run at first the detection capability of the Dispersion of Double Differences (D3) algorithm and then the Precise and Fast (PAF) algorithm for the DOA estimation, both validated in previous project deliverable D4.2.

Types of trajectories

As illustrated before, during the open-field experiments the antenna baselines will be mounted on a vehicle moving on the area affected by the interferences. In order to obtain a wide direction of arrival variation, different trajectories describing straight lines and curve paths with stops stages were specified in the trials. Some examples are shown below:

 Field experiments raw data

Additional information on the data obtained during the open field trials is described in detail in the following publication associated to the project deliverable D8.2 :

https://zenodo.org/record/3532660#.XejF8egzaUk