As previously covered, the Broadcast Positioning System (BPS) uses ATSC 3.0 to deliver a complementary position, navigation and timing (PNT) solution to augment GPS. Following lab testing in 2023, BPS was deployed on a live broadcast station in the Washington, D.C., market. Having BPS on the air allows for comprehensive validation and testing, and the NAB Technology team is proud to report on some of the initial test results.
Installation at WHUT
A BPS synchronizer was installed at WHUT and integrated into its transmission chain. This first installation at a live television station provided valuable insight into real-world circumstances not present in a lab environment.
Measurement and verification of transmission and cable delays
In this initial phase of deployment, BPS is intended to provide highly accurate time, given known locations of both the receiver and the transmitter. The accuracy of the time at the receiver depends on highly accurate measurements of all of the known transmission delays. Over-the-air, each foot of distance adds approximately one nanosecond of delay. In cables, that delay is somewhat longer and varies based on the particular type of cable. Once all the transmission delays were tallied, the accuracy of the BPS-delivered time as compared to GPS-delivered time was able to be verified.
48-hour test validating <50 ns accuracy with line-of-sight reception
Once the timing was verified, the system was left untouched for 48 hours to ascertain the long-term accuracy. With a rooftop antenna with line-of-sight to the transmitter, time remained accurate within +/- 35ns over the duration of the test. It’s important to note that this level of accuracy is only expected when the transmit and receive antennas are in line-of-sight. Higher variability is expected with ground-level receivers or more challenging signal environments, which will be the subject of future tests.
Patio test in preparation for mobile testing
A portable unit containing both a GPS and television (BPS) antenna was configured, calibrated and tested at the NAB patio. In future tests, this unit will be used at additional sites to further validate BPS.
Additional Receivers Configured for testing at other sites
In addition to the mobile unit, six additional BPS receivers were configured and tested so that they can be deployed at additional locations.
Next Steps
Now that BPS is on the air, the NAB Technology team is excited to be able to further test the functionality and capabilities of BPS at additional sites and in different circumstances. We look forward to continuing to report on the progress.