The International Telecommunication Union (ITU), a United Nations (UN) agency, is the agency that,
under an international treaty, sets radio spectrum usage regulations among member nations. Within the
United States of America (USA), the organization that sets regulations, coordinates an application for use,
and provides authorization for federal government/agency use of the radio frequency (RF) spectrum is the
National Telecommunications and Information Administration (NTIA). In this regard, the NTIA defines
which RF spectrum is available for federal government use in the USA, and how it is to be used. The
NTIA is a component of the United States (U.S.) Department of Commerce of the federal government.
The significance of ITU regulations is that ITU approval is required for U.S. federal government/agency
permission to use the RF spectrum outside of U.S. boundaries. All member nations have signed a treaty
to do so. U.S. federal regulations for federal use of the RF spectrum are found in the Manual of
Regulations and Procedures for Federal Radio Frequency Management, and extracts of the manual are
found in what is known as the Table of Frequency Allocations. Nonfederal government and private sector
use of the RF spectrum within the U.S. is regulated by the Federal Communications Commission (FCC).
There is a need to control "unwanted emissions" (defined to include out-of-band emissions, which are
those immediately adjacent to the necessary and allocated bandwidth, plus spurious emissions) to
preclude interference to all other authorized users. This paper discusses the causes, effects, and
mitigation of unwanted RF emissions to systems in adjacent spectra.
Digital modulations are widely used in today's satellite communications. Commercial communications
sector standards are covered for the most part worldwide by Digital Video Broadcast - Satellite (DVB-S)
and digital satellite news gathering (DSNG) evolutions and the second generation of DVB-S (DVB-S2)
standard, developed by the European Telecommunications Standards Institute (ETSI). In the USA, the
Advanced Television Systems Committee (ATSC) has adopted Europe's DVB-S and DVB-S2 standards
for satellite digital transmission. With today's digital modulations, RF spectral side lobes can extend out
many times the modulating frequency on either side of the carrier at excessive power levels unless
filtered. Higher-order digital modulations include quadrature phase shift keying (QPSK), 8 PSK (8-ary
phase shift keying), 16 APSK (also called 12-4 APSK (amplitude phase shift keying)), and 16 QAM
(quadrature amplitude modulation); they are key for higher spectrum efficiency to enable higher data rate
transmissions in limited available bandwidths. Nonlinear high-power amplifiers (HPAs) can regenerate
frequency spectral side lobes on input-filtered digital modulations. The paper discusses technologies and
techniques for controlling these spectral side lobes, such as the use of square root raised cosine (SRRC)
filtering before or during the modulation process, HPA output power back-off (OPBO), and RF filters after
the HPA. Spectral mask specifications are a common method of the NTIA and ITU to define spectral
occupancy power limits. They are intended to reduce interference among RF spectrum users by limiting
excessive radiation at frequencies beyond the regulatory allocated bandwidth.The focus here is on the communication systems of U.S. government satellites used for space
research, space operations, Earth exploration satellite services (EESS), meteorological satellite services
(METSATS), and other government services. The 8025 to 8400 megahertz (MHz) X band can be used to
illustrate the "unwanted emissions" issue. 8025 to 8400 MHz abuts the 8400 to 8450 MHz band allocated
by the NTIA and ITU to space research for space-to-Earth transmissions such as receiving very weak
Deep Space Network signals.
The views and ideas expressed in this paper are those of the authors and do not necessarily reflect
those of The Aerospace Corporation or The National Oceanic and Atmospheric Administration (NOAA)
and its National Environmental Satellite Service (NESDIS).
Errors due to wireless transmission can have an arbitrarily large impact on a compressed file. A single bit error appearing in the compressed file can propagate during a decompression procedure and destroy the entire granule. Such a loss is unacceptable since this data is critical for a range of applications, including weather prediction and emergency response planning. The impact of a bit error in the compressed granule is very sensitive to the error's location in the file. There is a natural hierarchy of compressed data in terms of impact on the final retrieval products. For the considered compression scheme, errors in some parts of the data yield no noticeable degradation in the final products. We formulate a priority scheme for the compressed data and present an error correction approach based on minimizing impact on the retrieval products. Forward error correction codes (e.g., turbo, LDPC) allow the tradeoff between error correction strength and file inflation (bandwidth expansion). We propose segmenting the compressed data based on its priority and applying different-strength FEC codes to different segments. In this paper we demonstrate that this approach can achieve negligible product degradation while maintaining an overall 3-to-1 compression ratio on the final file. We apply this to AIRS sounder data to demonstrate viability for the sounder on the next-generation GOES-R platform.
GOES-R, planned for launch around 2012, is currently under development by the National Oceanic and Atmospheric Administration (NOAA) of the United States. It will be the first in a new series of geostationary (GEO) environmental satellites to provide greater capabilities for weather, atmosphere, climate, and ocean monitoring. All the onboard sensors together may generate a combined raw sensor data rate of as much as 200 Mbps on the downlink, while the global rebroadcast data rate to the users after ground compression may be as much as 32 Mbps. To transmit such a high data rate through a channel of limited bandwidth, the adoption of a high-order modulation, such as QPSK, 8PSK, or 16QAM, is necessary. As a result, much higher transmit power than that for the binary modulation is needed in order to achieve the required bit error rate, which is particularly stringent for GOES-R due to the needed protection to the compressed data. Thus, the forward error correction (FEC) coding, which is a technique that can provide significant improvement of power efficiency, becomes crucial for GOES-R. This paper presents various methods of combining high-order modulations and FEC codes. We have proposed a baseline code waveform for GOES-R, which can satisfy both bandwidth and power efficiency requirements. In this paper, we also assess other commercially available code waveforms and compare their performances with that of our baseline waveform.
Research has been undertaken to examine the robustness of JPEG2000 when corrupted by transmission bit errors in a satellite data stream. Contemporary and future ultraspectral sounders such as Atmospheric Infrared Sounder (AIRS), Cross-track Infrared Sounder (CrIS), Infrared Atmospheric Sounding Interferometer (IASI), Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS), and Hyperspectral Environmental Suite (HES) generate a large volume of three-dimensional data. Hence, compression of ultraspectral sounder data will facilitate data transmission and archiving. There is a need for lossless or near-lossless compression of ultraspectral sounder data to avoid potential retrieval degradation of geophysical parameters due to lossy compression. This paper investigates the simulated error propagation in AIRS ultraspectral sounder data with advanced source and channel coding in a satellite data stream. The source coding is done via JPEG2000, the latest International Organization for Standardization (ISO)/International Telecommunication Union (ITU) standard for image compression. After JPEG2000 compression the AIRS ultraspectral sounder data is then error correction encoded using a rate 0.954 turbo product code (TPC) for channel error control. Experimental results of error patterns on both channel and source decoding are presented. The error propagation effects are curbed via the block-based protection mechanism in the JPEG2000 codec as well as memory characteristics of the forward error correction (FEC) scheme to contain decoding errors within received blocks. A single nonheader bit error in a source code block tends to contaminate the bits until the end of the source code block before the inverse discrete wavelet transform (IDWT), and those erroneous bits propagate even further after the IDWT. Furthermore, a single header bit error may result in the corruption of almost the entire decompressed granule. JPEG2000 appears vulnerable to bit errors in a noisy channel of satellite transmission, and thus has difficulty to preserve the quality of ultraspectral sounder data. A channel decoded bit error rate (BER) of 10-11 or better may be necessary for a granule error rate of 0.00116 in a compressed ultraspectral sounder data stream that is transmitted in a satellite channel. This work at The Aerospace Corporation and the University of Wisconsin, CIMSS, was under separate contracting from and performed for the National Oceanic and Atmospheric Administration (NOAA) National Environmental Satellite, Data, and Information Service (NESDIS), a component of the U.S. Department of Commerce.
Conference Committee Involvement (4)
Satellite Data Compression, Communication, and Processing IV
10 August 2008 | San Diego, California, United States
Satellite Data Compression, Communications, and Archiving III
29 August 2007 | San Diego, California, United States
Satellite Data Compression, Communication, and Archiving II
13 August 2006 | San Diego, California, United States
Satellite Data Compression, Communications, and Archiving
31 July 2005 | San Diego, California, United States