A Strategy for Active Remote Sensing Amid Increased Demand for Radio Spectrum (2015) / Chapter Skim
Currently Skimming:
9 Technology and the Opportunities for Interference Mitigation
9 Technology and the Opportunities for Interference Mitigation
Pages 189-206
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 189... ...
If interference exceeds this threshold, it is sometimes still possible to apply technological remedies that reduce the interference to a level below the threshold, thereby recovering the data without loss of information. In a sensing application, however, the target environment has many thresholds because the strength of the signal scattered from the atmospheric volume or the land or ocean surface may vary over a wide range, so there is no clear or absolute level for successful interference mitigation.
|
From page 190... ...
If an active remote sensing system relies on the transmission of an independent signal that is already present in the spectrum, allocation of additional spectrum is not necessary for the sensing function. Two key examples are provided to illustrate the process: (1)
|
From page 191... ...
SOURCE: NOAA Space Weather Prediction Center, "U.S. Total Electron Content," http://www.swpc.noaa.gov/products/us-total-electron-content, accessed August 3, 2015.
|
From page 192... ...
Frush, and E Loew, Design of a bistatic dual-Doppler radar for retrieving vector winds using one transmitter and a remote low-gain passive receiver, Proceedings of the IEEE 82(12)
|
From page 193... ...
Unilateral approaches to interference mitigation are used when appropriate. In some applications, however, there is no effective method of cooperation.
|
From page 194... ...
Frush, and E Loew, Design of a bistatic dual Doppler radar for retrieving vector winds using one transmitter and a remote low-gain passive receiver, Proceedings of the IEEE 82(12)
|
From page 195... ...
allocations at the front end of this equipment may mix via nonlinear effects to cause interference in, or partially outside, the spectrum served by this equipment. Older transmitting equipment may lack the filtering to meet adjacent spectral allocations, and/or the wave shaping, especially for pulsed signals, may be insufficient to reduce transient creation of spurious products that fall outside the spectral allocation for this equipment.
|
From page 196... ...
MOBILE time signal satellite FIXED (space-to-Earth) EXPLORATION RADIOLOCATION 2700.0 27.54 Standard frequency and INTER-SATELLITE FIXED MOBILE RADIONAVIGATION METEOROLOGICAL AERONAUTICAL MOBILE ISM – 24.125 ± 0.125 Amateur-satellite 241.0 FIXED RADIOLOCATION RADIOASTRONOMY Amateur 27.0 Radiolocation AIDS RADIONAVIGATION 28.0 MOBILE 248.0 Inter-satellite FIXED MOBILE INTER-SATELLITE AMATEUR AMATEUR SATELLITE Radioastronomy AMATEUR-SATELLITE AMATEUR 2900.0 except aeronautical mobile SPACE RESEARCH 250.0 27.5 29.7 275 EARTH EXPLORATION- LAND MOBILE FIXED RADIOASTRONOMY (passive)
|
From page 197... ...
The motivated user generally implements some form of power control, so that only the required power for the communication link is used, and this reduces the potential for leakage relative to the case where all signals operate at full power. Much of the foreseeable future gains in data bandwidth to mobile users will be due to spatial sharing.
|
From page 198... ...
The second feature is a new implementation of spatial sharing between different users of the spectrum: devices within 35 km of a terminal Doppler weather radar (TDWR) location must be separated by at least 30 MHz (center-to-center)
|
From page 199... ...
Technology and the O pp o r t u n i t i e s for I n t e r f e r e n c e M i t i g at i o n 199 FIGURE 9.10 Spectral sharing efficiency is improved with the use of three sectors within a cell and a frequency-reuse factor of 4 between cells. SOURCE: Courtesy of TruTeq Wireless, truteq.com.
|
From page 200... ...
. As discussed earlier, time slots within each frequency slot may be used by mul tiple users, and this is called time division multiple access (TDMA)
|
From page 201... ...
This limitation in isolation, coupled with the larger dynamic range required in active sensor systems, means that there is limited benefit for the use of the code domain in active sensing systems. However, if there are known interferers using a known code set, there are opportunities for both unilateral and cooperative sharing using this technology.
|
From page 202... ...
for air traffic control and weather radar, with the use of phased array methods in place of existing mechanically steered radar systems.2 The MPAR concept would enable rapid-update weather observations that are fundamentally important for severe weather safety, among other significant improvements, ben efiting both the active sensing community and the public. Another advantage of an MPAR system would be its improved spectral efficiency, since radars operating 2 Multifunction Phased Array Radar (MPAR)
|
From page 203... ...
program funds multidisciplinary research in technologies and techniques with potential to greatly increase the efficiency of spectrum, including sharing. For example, since space-based, active remote sensing sensors typically observe a single spot on Earth only a few times per day, they could coordinate with other transmitting services to more efficiently use the spectrum otherwise reserved only for remote sensing when not in use by remote sensing.
|
From page 204... ...
For unilateral interference mitigation, the optimum approach is to probe the channel and adjust the transmit waveform for minimum correlation with the channel interference characteristics. A simple form of this (previously discussed)
|
From page 205... ...
Therefore, specific radar bands are best allocated for either ground-based systems or Earth-imaging systems. FINDINGS AND RECOMMENDATIONS Finding 9.1: From the perspective of efficient spectrum usage, the active sensing community would benefit from consolidating the L-, C-, and S-band radar assets of NOAA and the FAA to a single multifunction radar at the S-band, as proposed by the Multifunction Phased Array Radar program.
|
From page 206... ...
Finding 9.3: The use of millimeter-wave frequencies for shortwave, femtocell sized communications would increase network capacity by an order of magnitude, thereby reducing pressure on the spectrum and on the active sensing science ser vices, as well. Recommendation 9.2: The wireless industry should pursue the femtocell approach by developing towers, networks, and the like to add the use of millimeter-wave frequencies for communications in 6G communication standards and up.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.