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How to Make a Digital Satellite Link Simulation to Compare RRC and ...
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Short Description: How to Make a Digital Satellite Link Simulation to Compare. RRC and Bessel Uplink Filters. *. Robert A. Peters,. †. Stellar Solutions, 250 Cambridge Ave. ...
Content Inside: 24th AIAA International Communications Satellite Systems Conference (ICSSC) and 4t AIAA 2006-5314 11 - 14 June 2006, San Diego, California How to Make a Digital Satellite Link Simulation to Compare RRC and Bessel Uplink Filters* Robert A. Peters, Stellar Solutions, 250 Cambridge Ave. Palo Alto, CA 94306 Meeting the ITU requirement that sidelobes be less than -25 dBC required a new sidelobe specification for NOAA's Data Collection Service (DCS) uplinks. NOAA used this opportunity to determine if the selection of an RRC (Root Raised Cosine) or Bessel filter would allow greater capacity and/or better performance. A digital simulation was undertaken to assist in filter specifications. Conducting this simulation required developing a systematic approach to optimize the: over sample rate, filter order, filter bandwidth, output power back-off of the uplink SSPA, and SSPA output power back-off of the satellite. The step by step approach developed to determine the appropriate values of the variables is described. The study found that for higher order filters (greater than 6th order, either filter could be used, but that RRC filter performance, unlike Bessel filter performance, did not degrade as the filter order is reduced. Bessel filters lower than 5th or 6th order could not meet the sidelobe specification. I. The DCS System The GOES Data Collection System (DCS) system began in 1976 with the launch of the NOAA's (National Oceanic and Atmospheric Administration) GOES (Geostationary Operational Environmental Satellite) with a dedicated 400 kHz bandwidth DCS transponder. Initially uplinks were 100 bps/BPSK. Today DCS consists of approximately 16,000 platforms that uplink 100,000 messages per day on the Geostationary Operational Environmental Satellite (GOES) satellites. The platforms access the satellite either on a timed basis, usually a fraction of a minute once every 4 hours or on demand basis. This service is made available over the Western Hemisphere and is used not only by the U.S. government and also by Canada, Mexico, Chile, Columbia, Peru, Guatemala, Nicaragua, Venezuela, Costa Rica and Ecuador.1 The platforms are on land or in the ocean and are used to monitor: Monitoring weather conditions, particularly in inaccessible regions Monitoring water levels for flood monitoring, dam management, tide monitoring, and reservoir levels Monitoring forest fires Monitoring ocean temperatures and Tsunami warning system II. The Problem Usage of DCS has steadily increased and to allow for continued expansion NOAA has implemented a transition plan requiring that all new platforms after May 31, 2003 have 8-PSK 300 or 1200 bps uplinks2. Existing 100 bps platforms can continue until 2013. Both 8-PSK links are rate 2/3 coded. To keep costs low, the original 100 bps platforms did not have any filtering and so had wide frequency separations (1.5 kHz). To ease transition, the 300 bps links kept the same spacing as the 100 bps links and the 1200 bps links had double that spacing (3 kHz). Filtering was required for both 8-PSK links but the original mask did not meet ITU requirements that the sidelobes of at least -25 dB down from the carrier3. To meet the increasing demand, NOAA also decided on a long range plan to halve the spacing of the 300 bps links to 750 Hz. Meeting ITU sidelobe specifications required a new filter specification. NOAA took this opportunity to determine which filter (RRC or Bessel) that met the ITU requirements had superior performance in bandwidth and/or lower implementation loss. * This work supported by NOAA which does not necessarily views expressed Work Address: Dr. Robert Peters, Code 415, Goddard Space Flight Center, Greenbelt, MD 20771 1 American Institute of Aeronautics and Astronautics Copyright 2006 by Stellar Solutions, Inc. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.
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