初步评估干扰发射机选择频带和带外接收机的潜在影响

INITIAL ASSESSMENT OF THEPOTENTIAL IMPACT FROM A JAMMINGTRANSMITTER ON SELECTED IN-BANDAND OUT-OF-BAND RECEIVERS U.S. DEPARTMENT OF COMMERCENational Telecommunications and Information Administration INITIAL ASSESSMENT OF THEPOTENTIAL IMPACT FROM A JAMMINGTRANSMITTER ON SELECTED IN-BANDAND OUT-OF-BAND RECEIVERS Edward F. Drocella U.S. DEPARTMENT OF COMMERCE Lawrence E. Strickling, Assistant Secretary forCommunications and Information May 2010 ACKNOWLEDGMENTS The author would like to thank Frank Sanders and Robert Johnk from theNational Telecommunications and Information Administration Institute forTelecommunication Sciences for providing the measurements that were necessary toperform the assessment contained in this technical memorandum. EXECUTIVE SUMMARY This technical memorandum examines issues related to the potential interferenceimpact of a specific Cellular Radiotelephone Service (Cellular) and PersonalCommunications Service (PCS) jammer transmitter on selected out-of-band and in-bandreceivers. The National Telecommunications and Information Administration (NTIA)Institute for Telecommunication Sciences performed laboratory and field measurementsof a specific jammer transmitter and where appropriate these measurements were used inthe interference assessment. Assessment of Out-of-Band Receivers In the assessment of out-of-band receivers, NTIA considered Federal land mobileradio (LMR) receivers in the 162-174 MHz and 406.1-420 MHz bands and GlobalPositioning System receivers in the 1559-1610 MHz, 1215-1240 MHz, and 1164-1188MHz bands most likely to be used in the vicinity of a jammer transmitter at prisonfacility. NTIA performed laboratory measurements of the equivalent isotropicallyradiated power (EIRP) levels to characterize the emissions from the jammer transmitter inthe LMR and GPS frequency bands and used the measured EIRP levels and establishedinterference protection criteria to compute the distance separations necessary to precludepotential interference. Therefore, based on this method, NTIA can calculate theseparation distances required for any jammer transmitter for which the emissioncharacteristics are known. NTIA can then use these distance separations to determine fora particular jammer of known configuration and emission characteristics, whether thatjammer will protect Federal receivers at or near a specific site. Based on the results of NTIA’s measurements and this assessment, whenoperating at full power and jamming in the Cellular and PCS bands, the tested jammertransmitter could cause some impact to LMR receivers at the prison and GPS receiver usein and around the facility. However, the use of a diplexer decreased the potentialinterference and reduced the required distance separations to such low values as to benegligible. Therefore, the specific jammer tested could be implemented with the diplexeror another appropriate filter without risk to Federal operations. However, because of thelimited deployment of the jammer transmitter at the Federal facility, NTIA cannot draw,from the field measurements, any conclusions assessing the potential of aggregateinterference to out-of-band receivers if multiple jammer transmitters of this same typewere operated throughout the facility. Variations in jammer configurations, effects of multiple jamming transmitters,structural characteristics of buildings, and propagation factors will be different dependingon the installation and the facility making it difficult to fully assess potential interferenceto Federal operations outside the bands where jamming is performed. Given all of thepossible variations in a jammer system installation, on-site measurements to determinethe out-of-band signal levels outside of each facility for each installation would benecessary. Assessment of In-Band Receivers There are currently no industry adopted standards for in-band interference fromother systems to Cellular and PCS handset receivers. In order to assess the potentialinterference impact to Cellular and PCS handset receivers, the Federal CommunicationsCommission and the wireless industry will need to develop interference protectioncriteria. Variations in jammer configurations, effects of multiple jamming transmitters,structural characteristics of buildings, and propagation factors will be differentdepending on the installation and the facility making it difficult to develop analyticaltechniques to fully assess potential interference to Cellular and PCS receivers withoutusing very conservative assumptions. Given all of the possible variations in a jammersystem installation, on-site measurements to determine the signal levels outside of thefacility would be necessary. Based on the field measurements, NTIA observedvariations in the measured signal levels of the jammer transmitter outside of the facility.These variations can make it difficult to distinguish the jammer transmitter signal in theenvironment. Moreover, depending on the relative signal levels it