The GPS Innovation Alliance (GPSIA) says it supports a 1 dB standard for determining harmful interference. In an ex parte filing posted July 14 in IB dockets 12-340 and 11-109, the GPSIA cited testing conducted under the National Advanced Spectrum and Communications Test Network (NASCTN) on the impact of LTE signals on GPS receivers (TR Daily, Feb. 17). “The test results provide both direct and indirect support for the use of the historic and well-established standard for determining harmful interference – whether an interfering signal produces a 1 dB decrease in the Carrier-to-Noise Power Density Ratio (‘C/N0’) of the affected receiver,” the GPSIA said.
“The standard is also amply supported not only by precedent and use in applicable technical standards but is also based upon well understood technical characteristics of GNSS receivers and the impact of noise on the performance of these receivers, all of which remain valid today.” Ligado Networks LLC has argued that the testing confirmed Ligado’s argument that a 1 dB increase in the noise floor is not the appropriate standard for assessing harmful interference to GPS receivers. What matters is the actual performance of the devices in the presence of LTE signals, the company says.