GNSS Simulator Basics: Specifications and Vendors

This page covers the fundamentals of GNSS simulators, including their specifications, receiver test setups, and a list of vendors.

Understanding GNSS

GNSS stands for Global Navigation Satellite System. It’s a technology that delivers navigation and other location-based services to users worldwide.

The GNSS system is composed of two primary elements:

• Space Segment: This involves a constellation of satellites orbiting the Earth.
• Ground Segment: This consists of GNSS receivers that receive and process the signals broadcast by the satellites. These receivers determine location, speed, and time for users within the satellite coverage area.

Examples of GNSS include GPS, Galileo, and GLONASS. Due to the widespread use of GNSS in numerous applications, thorough testing of GNSS receivers is crucial to ensure high-quality user devices.

GNSS and other navigation systems are typically tested either in the field or in a laboratory setting. Lab testing utilizes a GNSS simulator.

Advantages of GNSS Simulators

Here’s why GNSS simulators are often preferred over live field testing:

• Complete Control: GNSS simulators offer full control over the satellite constellation, which isn’t possible in real-world testing.
• Simulated Environments: Lab testing can simulate various environmental conditions and severity levels.
• Repeatability: Lab tests are repeatable, unlike live testing which is subject to changing conditions.
• Error Injection: Testing can be performed while introducing constellation errors to evaluate receiver performance.
• Cost-Effective: Lab testing is generally cheaper than field testing.
• Versatile Scenarios: Testing can be conducted for any location on Earth, simulating past, present, or future scenarios.
• Secure Environment: Testing can be done in a controlled environment, free from unintended interference and multipath signal effects.

GNSS Receiver Test Setup

GNSS simulator test setup

What is a GNSS Simulator?

A GNSS simulator is a device that recreates the conditions found in live field scenarios, complete with satellite constellations and environmental factors. It’s also referred to as a GNSS RF Simulator.

Essentially, it provides a platform that emulates real-world conditions, including the motion of satellites and vehicles, allowing for comprehensive testing of GNSS receivers.

The diagram above illustrates a typical GNSS receiver test setup. As shown, the GNSS receiver can be directly connected to the GNSS simulator using an RF cable, or they can communicate wirelessly via RF antennas. Often, GNSS simulation software is installed on a laptop or PC connected to the GNSS simulator hardware. Many simulators also incorporate a GNSS signal generator with built-in software for configuring various system parameters. These tests verify that both the RF and processing components of the GNSS receiver are functioning correctly.

Key GNSS Simulator Specifications

When choosing a GNSS simulator for receiver testing, consider the following specifications:

• Configurable Satellites and Constellations: The ability to customize satellite configurations and constellations.
• Remote Control Interface: Support for USB, Ethernet, or RS232 interfaces for remote control.
• 1 PPS Output: A 1 Pulse Per Second (PPS) output for timing synchronization.
• Data Storage: Capability to record test data.
• Output Signal Level: Typical range of -83dBm to -115dBm.
• Number of RF Channels: Ranging from 1 to 3 channels.
• Output Frequencies: Common frequencies include 1561.098 MHz, 1575.4 MHz, and 1602 MHz.

GNSS Simulator Vendors

The following table lists some GNSS simulator vendors and their products: