FCC ESTABLISHES OUT-OF-BAND EMISSION LIMITS
FCC established new out-of-band emission limits for certain mobile earth station terminals (METs) used for Mobile Satellite Service (MSS) communications in report and order (R&O) released Wed. Restrictions apply to METs operating in 1610-1660.5 MHz band and METS in 1990-2025 MHz. Commission said it was imposing limits to prevent METS from interfering with aeronautical reception of satellite radionavigation signals in 1559-1610 MHz band. Specifically, limits are designed to improve flight safety by ensuring that emissions from METS won’t impair aircraft radionavigation during instrument approach and landing.
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Commission also offered proposal to adopt rules to facilitate global operation of METs designed to implement international Memorandum of Understanding on Global Mobile Personal Communication by Satellite (GMPCS) that was signed by 120 govts, including U.S., and private sector organizations. FCC said it wasn’t prepared to take action on GMPCS, but would do so in future order. Comments are due in 60 days; reply comments 90 days.
International Civil Aviation Organization (ICAO) has designated 2 satellite radionavigation systems for use as components of integrated Global Navigation Satellite System (GNSS) for aeronautical applications -- NAVSTAR Global Positioning System (GPS) and GLONASS. Space segment of GPS system consists of 24 satellites in nongeostationary orbit maintained by U.S. govt. GPS satellites transmit ranging signals on 1575.42 MHz carrier, Standard Positioning Service (SPS) signal and Precise Positioning Service (PPS) signal. PPS signal is modulated by code that can be processed only by users equipped with cryptographic keys that are limited primarily to military. SPS signal, which is available for general civilian use, extends through band 1563.42 to 1587.42 MHz and is modulated with pseudo-random noise C/A code sequence, null-to-null bandwidth of which occupies 2 MHz centered on 1575.42.
FAA is planning shift from reliance on ground-based systems for aircraft radionavigation during instrument approach and landing in U.S. to satellite guidance obtained mainly from GPS-SPS. Because latter isn’t accurate enough to serve as primary means of guidance, FAA is promoting development of 2 auxiliary systems: (1) Wide Area Augmentation System (WAAS). WAAS signals providing correction data will be downlinked to aircraft receivers by geostationary satellites transmitting in GPS-SPS frequency band. FAA expects to certify GPS/WAAS that will afford horizontal and vertical positioning accuracy to tolerance of 8 meters as primary means of instrument navigation for Category 1 precision approach flight and all less-critical phases of flight, FCC said. GPS/WAS is expected to be fully operational in next 6 years. (2) Local Area Augmentation System (LAAS). LAAS involves transmission of additional corrective signals from ground stations sited near runways. GPS/LAAS is expected to receive guidance accuracy and reliability sufficient for all phases of instrument approach flight.
Commission accepted NTIA recommendation to adopt requirement to suppress EIRP of discrete emissions of less than 700 Hz bandwidth to -80 dBW in frequencies between 1559 and 1605 MHz. Motorola and Hughes Network systems argued against proposal. NTIA said proposed narrowband limit was necessary to protect aeronautical radionavigation. GPS-SPS, WAAS and GLONASS are known to be particularly susceptible to disruption from continuous-wave or very narrowband interfering signals, NTIA said. Commission proposed in R&O to temporarily excuse 1.6 GHz METs placed in service before Jan. 2002 from meeting -70 dBW/MHz and -80 dBW wideband/narrowband limits in upper segments of ARNS band.