Performing Faster GNSS Receiver Validation With Averna’s NI PXI-Based Record and Playback

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"Averna’s RP-3200 Wideband RF Record & Playback provides us with many tangible benefits. Now we can use repeatable standardized tests, replaying GNSS signals in our lab to eliminate environmental variables and save on travel and repeated location testing."

- Peter France, Trimble Navigation Ltd

The Challenge:
Speeding up Trimble Navigation’s validation and test processes, which for years featured manual GNSS receiver testing, while ensuring thorough test coverage and high product quality.

The Solution:
Using Averna’s rugged and portable RP-3200 Wideband RF Record & Playback to collect live GNSS signals, including GPS and GLONASS, for unlimited playback in the Trimble Navigation lab in New Zealand. This eliminated many time-consuming and expensive field trips and accelerated Trimble’s receiver validation processes.

Author(s):
Peter France - Trimble Navigation Ltd
Etienne Frenette - Averna

Averna, an NI Platinum Alliance Partner, has considerable expertise in validating and testing RF products and systems across multiple industries, including aerospace and defense, automotive, and consumer electronics. Along with test engineering services and turnkey test systems, Averna offers a line of RF record and playback instruments for both consumer-grade products (for example, car radios, GPS receivers) and highly specialized applications (for example, satellite and signal analysis monitoring).

The Many Challenges of GNSS Receiver Validation

Effective GNSS receiver validation depends on repeated testing with accurate data, so a lot of effort typically goes into manual data collection, field analysis, and lab-based debugging. With all of this activity, GNSS testing cycles are long and prone to setbacks.

These cycles are further lengthened by the development of new receivers and devices with additional functionality, as well as regular updates to navigation infrastructure and ever-evolving industry standards. Gathering high-quality, dependable measurements with manual tools is a costly and painstaking process.

Trimble Navigation

As a developer of position- and location-based GNSS receivers and software, Trimble Navigation is well aware of these challenges. The company’s Mapping & GIS division in New Zealand tests GNSS receiver accuracy from the meter level down to centimeters using rigorous test procedures that emulate its customers’ working conditions by surveying dozens of control points under tree canopies and near buildings as well as in more open conditions.

In the past, Trimble’s testers used a GNSS receiver to manually collect positional data, compare it with the company’s control coordinates, and perform statistical error analyses. Trimble’s GNSS validation personnel had been spending a lot of time outdoors performing repetitive test procedures. In just one year, they conducted 680 GPS-related field tests, and one engineer collected 900 files.

Trimble’s GNSS receiver validation processes also involved significant complexity. Each test included many variables such as the satellite constellation, the operator’s field technique, and the operator’s

position at each control point (affecting which satellites were blocked). These factors introduced significant variability to the results. Therefore, each test needed to be repeated multiple times to ensure a statistically valid conclusion.

Peter France, a technical consultant with Trimble Navigation, explained, “We need to test in the difficult conditions in which our customers work. Repetitive manual testing is very time-consuming, and the signal obstruction and multipath conditions meant that there was no way we could use a simulator to get acceptable results.”

Using a Portable Solution to Capture GNSS Signals

To make its processes more efficient, Trimble chose Averna’s RP-3200 Wideband RF Record & Playback for field recording and lab playback. The RP-3200 has two 50 MHz channels (expandable to four, or 200 MHz), a frequency range of 10 MHz to 2.7 GHz, and considerable RAID-based storage space (up to 48 TB) to collect and hold large libraries of real signals. On the road, the RP-3200 can be operated in a vehicle and powered by the vehicle’s battery.

The system features several NI PXI products that are integral to its high-throughput, high-performance makeup. For example, in addition to being housed in an 18-slot 3U PXI Express chassis, the RP-3200 incorporates the following:

 

Figure 1. Averna’s RP-3200 Wideband RF Record & Playback

Averna’s RF and GNSS Expertise Adds Value

To these NI components, Averna adds its own RF and GNSS expertise. For example, to enable coherent record and playback of the GPS L1 and L2 bands, Averna integrates its software IP, which extends the range of applications for the NI VSA and VSG. This combination of NI hardware and Averna application software allows for tight synchronization between channels and ensures perfect coherency between multiple recorded frequencies.

To help users, especially with their field-recording tasks, the RP-3200 provides a high resolution of 0.1 Hz and real-time spectrum views, allows file cropping, supports timestamped comments, and records more than 24 hours on one channel.

Figure 2. Trimble’s RP-3200 Setup for Signal Recording and Playback

Taking the RP-3200 on the Road

In the past, Trimble performed satellite-based augmentation system (SBAS) testing by shipping GNSS receivers around the world. Location-specific data collection was expensive and time-consuming. When receiver algorithm problems surfaced, debugging had to be done back in the office and then retesting was completed on location. With the RP-3200, SBAS RF signals captured in the field are available in the lab for repeat testing and analysis, allowing Trimble to reduce travel costs and advance its testing cycle significantly.

Figure 3. To validate receiver performance, a Trimble team captures GNSS signals under tree canopies and near buildings.

GNSS Playback Improves Regression and Self-Jam Testing

Trimble uses the RP-3200’s Playback feature as a key time-saver for regression testing, such as when the receiver’s firmware or data-collection software has changed. Before they had the RP-3200, Trimble’s test team members manually collected and analyzed around 50 GNSS data files during a busy week, which represented typical end-user workflows in various hardware-software combinations. Now the testers no longer need to perform repetitive fieldwork for regression testing; instead they use the RP-3200’s Playback feature to ensure correct operation of the whole system, including receiver hardware, firmware, and application.

Another challenging area for GNSS receiver validation is self-jam testing. As more electronics—including cellular and Bluetooth transmitters—are added to devices that also include a GNSS receiver and antenna, and multiple GNSS bands and wider bandwidths need to be tracked, self-jamming has become a significant issue. Though it is possible to use live-sky signals to test performance, the results vary widely and it is difficult to identify improvements. Playback eliminates those variables and reduces the amount of testing required.

Solution Enables Efficient, Repeatable GNSS Receiver Validation

Averna’s PXI-based RF record and playback solution has really enhanced Trimble New Zealand’s GNSS testing process. As Peter France concluded, “The RP-3200 now allows us to efficiently perform rigorous testing and analysis. We have significantly reduced the need for labor-intensive manual testing, with its inevitably variable run-to-run outcomes. With the Averna system, we record some runs and then replay them for improved efficiency and highly repeatable results.”

A National Instruments Alliance Partner is a business entity independent from National Instruments and has no agency, partnership, or joint-venture relationship with National Instruments.

Author Contact Information:
Etienne Frenette
Averna
87 Prince St., Suite 510
Montreal, Quebec
Canada H3C 2M7

Author Information:
Peter France
Trimble Navigation Ltd
Trimble Navigation Ltd 15 Birmingham Drive
Christchurch 8024
New Zealand

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