In response to leaked claims that 75 percent of tested receivers failed the most recent round of testing against the LightSquared signal, Javad Ashjaee, Ph.D., president and CEO of JAVAD GNSS, wrote a letter to FCC Chairman Julius Genachowski noting that any GPS receiver that failed the test against the LightSquared signal will also fail against many other existing transmitting systems. “The problem is in the design of the GPS receivers that were tested,” he said. “Anyone can test this. Take any low-end GPS receiver similar to those they claim ‘failed’ the test and get close to some FM radio transmitting stations, for example.”
He urged the FCC to establish guidelines for GPS receivers. “The FCC should mandate that any receiver used for critical applications must show their signal-to-noise numbers, so every user can see degradations when they encounter interference,” the letter said. “High precision receivers, and all those which use P-code, should have 8- to 10-dB suppression for every MHz away from the edges of the GNSS wide band (P-code). Low-end C/A-code-only receivers should have 2-dB suppression for every MHz away from the edges of the C/A code. These standards are important. The filter technology to achieve these (without negatively affecting the performance) exists today and should be applied because the cost and size of such filters are even less than what was used before.
“Had the FCC established and enforced receiver standards to begin with, we could have avoided this entire interference debate between LightSquared and the GPS industry.”
The entire letter is posted on JAVAD’s website.