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LEIRP ou Le PFD
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Nextel operated mobile telephone system in 800 MHz spectrum interleaved with ... Near/far interference near Nextel towers results in receiver-generated ... – PowerPoint PPT presentation
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Title: LEIRP ou Le PFD
1
LEIRPouLe PFD?
Consulting on wireless technology and policy
- Michael J. Marcus, Sc.D., FIEEE
- Director
- Marcus Spectrum Solutions, Paris, France
- mjmarcus_at_alum.mit.edu
- www.marcus-spectrum.com
ANFR 26 avril 2006
2
Background
- Many concepts of spectrum regulation date to the
early days of radio technology - Higher frequencies and new technology may create
new options - Traditionally ERP and EIRP have been the
dimension space to specify transmitter power
3
Basic Spectrum Management Issues
- Cochannel issues are the most straightforward and
have a major impact on frequency reuse - Adjacent and nearby channels also have a real
impact due to limitations of practical receivers - Example In US NTSC/TV rules only 1 of 6 channels
used in a given city due to receiver limitations
4
Basic Spectrum Management Issues
- Near/far issues limit system performance and
practical use of spectrum - Usually addressed through
- Frequency assignment practices
- Transmitter frequency rolloff
- Receiver selectivity
F1 transmitter
F2 receiver
F2 transmitter
5
Northpoint Nextel
- Two recent FCC issues with near/far at their
roots - Northpoint
- A proposal to use 12 GHz BSS downlink band for
terrestrial point-to-multipoint video
distribution - If transmitter on north side of community, no
interference on a clear day - Rain impacts downlink more than terrestrial path
and leads to near/far problems
6
Northpoint Nextel
- Nextel operated mobile telephone system in 800
MHz spectrum interleaved with land mobile public
safety/PS users - for historical reasons - Near/far interference near Nextel towers results
in receiver-generated intermodulation in PS
receivers
7
csc2 Antenna Technology
- Cosecant squared antenna technology has great
potential to reduce real practical limits to
efficiency at UHF and above - csc2 technology, developed at WWII MIT Radiation
Laboratory and used in GPS, results in relatively
uniform pfd over a large area - Requires vertical length of 10?
8
csc2 Antenna Technology
- Good design of vertical pattern of antennas can
limit dynamic range of signals near antenna sites - For example, UHF TV transmitters have moderate
PFDs near antenna despite 5 MW EIRP
9
csc2 Antenna Technology
- csc2 technology is practical at
- f gt 1 GHz and could be used productively in
many applications to improve spectrum efficiency - New computer algorithms simplify antenna
synthesis
www.remec.com/pdfs/LMDS20ShapeBeam.pdf
10
csc2 Antenna Technology
- Near/far problems are generally externalities
and little incentive for licensees to control
them - Not aware of any regulations that encourage or
require pfd control for terrestrial systems - But satellite pfd limits exist
- Few products available at present
- Possible chicken or egg problem
11
Examples of Products
2 GHz
28 GHz
12
Conclusions
- csc2 antennas create some new options for
increasing spectrum efficiency above 1 GHz - Would ANFR like to explore issue in future ITU-R
deliberations?
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