Q. Why do you think FCC did this with GPR? Was it ignorance
or are they looking at something we haven't talked about yet?
A. I'm not sure why FCC did this. There are some real significant reasons why
GPR shouldn't be lumped in with medical imaging and through-wall imaging. Both of these have
a pretty strong air transmission component. We don't want to transmit in air and we should
be treated differently with respect to any new rules.
GSSI and many others in the GPR community, both users and manufacturers, did get involved
in the early phases of the comment process, but FCC consistently told us that GPR is known to
be valuable, don't worry about it, you're OK. I think what happened, is there was such
a last minute rush to make the changes covering the air transmission devices that GPR was
the baby that got thrown out with the bathwater.
Q. What are the differences between GPR and the air transmission
devices that make it so they should be treated differently? How do you think GPR should be handled
in the Rules?
A. There are several differences. The biggest is the one we've already mentioned -
GPR is only an unintentional air transmitter. Second is pulse repetition frequency. For GPR,
the operating range is 50 KHz to 500 KHz, and the air guys want to use 1 MHz to 100 MHz. Third
is spectrum range - we operate from 40 MHz to 2.2 GHz, and the air transmitters usually operate
a lot higher. Finally, there's a big difference in quantity - the air guys want to sell
millions to a consumer market, we want to sell hundreds to more specialized commercial markets.
So from our viewpoint, there should be separate rules for GPR, and it should not be lumped in
with other devices. All the GPR manufacturers should be required to have their equipment tested
to make sure it conforms to Part 15 class B specs, but the user should not have to be licensed
and certainly no one should have to do prior notifications before each use.
Q. What is DOD's position on GPR and the new rules?
A. I don't think DOD was thinking about GPR when they raised their concerns about
interference with GPS and other national security systems. Last week I went down to the
Pentagon and talked to some of the DOD people. Part of the problem is that some of the NTIA
testing to look for interference only tested at pulse rate frequencies of 100 khz, 1 MHz, and
higher. GPR operates at 50-500khz. The 100 KHz testing showed no problem with interference,
but no testing was done at 500 KHz, so anything over 100 is suspect in DOD's eyes. They agreed
that GPR is a valuable tool for the military, and now recognize that the proposed rules are likely to
cause them problems in using it. They indicated that they would support use of GPR to the FCC
at a pulse rate frequency of 100 KHz.
100 KHz helps but still causes problems. Doing highway surveys, for example, we need high
data density, 1 scan per inch. We take the data by towing the equipment down the highway, and
to get this resolution at 55 mph, we need to use a 500 KHz pulse rate frequency. If we use
100 KHz, we can only go at 15 mph, which will seriously disrupt traffic. It's the same
situation with railroad bed testing - we have to use the higher pulse rate frequency to
avoid traffic disruptions.
Highway Inspection Set-up
Q. What's next? Have you brought this up to FCC since the
Report and Order was announced?
A. No, we've been waiting for the issuance of the R&O. It's possible, but
probably unlikely, that the actual language will give us more operating room than is apparent
from the press release and the charts. At least it may provide more clarity about what is meant.
In the meantime, we've contacted our congressional delegations - and so have the other
manufacturers -- we're doing this in a coordinated manner . The user group is also coordinating
their actions together. When the R&O is issued, we plan to contact NTIA, FCC, and others to see
what needs to be done and what can be done to find a compromise position.
We'll be working to get testing up to 500 khz pulse rate frequency to show that there isn't
any interference at this level.
Q. There's a 6month reexamination. Are you gearing up for
this and how?
A. Six months is too late - we'll be out of business if customers stop buying
from us because of needing licenses and get permission for every use. A six month delay will
just about completely kill the GPR industry in this country. Besides, I'm not convinced that
this six month reexamination will ever happen.
Q. Anything else you'd like to add about this controversy?
A. Our biggest shortcoming as an industry is that we haven't done enough to
educate people, especially at administrative levels, about the use and importance of GPR. We have
a lot of customers doing very important work, some of it related to public safety, but beyond
that we're relatively unknown.
Q. Dennis, thank you very much for talking with us about this issue.
It's been a real eye-opener.
GSSI UWB Position
Paper A very interesting paper with more facts on UWB and GPR, the GPR industry,
GPR customers and applications, etc. Editor's note 11/26/08: link is broken. We have contacted
GSSI for permission to post on SSS-mag.
Editor's Note: This list was compiled by Jeffrey R. Forster for a UWB mailing list we're on. Good info --
UWB specific channels
M. Z. Win and R. A. Scholtz, "Energy Capture vs. Correlation Resources in
Ultra-Wideband Bandwidth Indoor Wireless Communications Channels," 1997.
M. Z. Win and R. A. Scholtz, "On the Robustness of Ultra-Wide Bandwidth
Signals in Dense Multipath Environments," IEEE Comm. Letters, Vol. 2, No.2, Feb. 1998.
J.M. Cramer, R.A. Scholtz, and M.Z. Win, "On the analysis of UWB
communication channel," Proceedings of MILCOM 1999, Vol. 2, pp. 1191-1195, 1999.
J. M. Cramer, M. Win, and R.A. Scholtz, "Evaluatoin of the Multipath
Characteristics of the Impulse Radio Channel," Proc. of PIMRC '98, vol. 2, p. 864-868.
J. M. Cramer, R.A. Scholtz, and M.Z. Win, "Evaluation of an
Ultra-Wideband Propagation Channel," pre-print, publication soon.
S. S. Ghassemzadeh, R. Jana, C. W. Rice, W. Turin, V. Tarokh
(authors are with AT&T Research, "Measurement and Modeling of an Ultra-Wide
Bandwidth Indoor Channel", pre-print of submission to a special JSAC issue
L. Rusch, C. Prettie, D. Cheung, Q. Li, and M. Ho (authors are with
Intel Labs), "Characterization of UWB Propagation from 2 to 8 GHz in a
Residential Environment," pre-print of submission to a special JSAC issue
D. Cassioli, M. Win, and A. Molisch, "A Statistical Model for the
UWB Indoor Channel," Spring VTC 2001 Conf. Proceedings.
(see also other similar papers by Cramer, Win, and/or Scholtz)
Other channel models to consider (some wideband in nature with > 100s
MHz not necessarily 'ultra-wideband', but show similar trends as with UWB)
Model suggested by ITU P.1238 which was described in IEEE 802.15-00/294r1.
Model used for the evaluation of the IEEE 802.11g high rate PHY,
described in document IEEE 802.11-00/282r2 & IEEE 802.11-00/211r9.
Model suggested to evaluate the 802.15.3 PHY layers, described in document
G. Janssen, P. Stigter, and R. Prasad, "Wideband Indoor Channel Measurements
and BER Analysis of Frequency Selective Multipath Channels at 2.4, 4.75, and
11.5 GHz," IEEE Trans. Commun., Vol. 44, No. 10, Oct. 1996.
T. S. Rappaport and S. Sandhu, "Radio-Wave Propagation for Emerging Wireless
Personal-Communication Systems," IEEE Antennas and Propagation Magazine,
Vol. 36, No. 5, 1994. (a survey paper)
K. Pahlavan and A. Levesque, Wireless Information Networks, John Wiley and Sons, 1995.
H. Hashemi, "Impulse Response Modeling of Indoor Radio Propagation
Channels," IEEE JSAC, Vol. 11, No. 7, Sept. 1993, pp. 967-978.
A. Saleh and R. Valenzuela, "A Statistical Model for Indoor Multipath
Propagation," IEEE JSAC, Vol. SAC-5, No. 2, Feb. 1987, pp. 128-137.
R. Ganesh and K. Pahlavan, "Statistical modeling and computer
simulation of indoor radio channel," IEE Proceedings-1, Vol. 138, No. 3, June 1991.
T. S. Rappaport and S. Sandhu, "Radio-Wave Propagation for Emerging
Wireless Personal Communication Systems," IEEE Antennas and Propagation
Magazine, Vol. 36, No. 5, pg. 14-24, Oct. 1994 and the references therein.
K-W Cheung, J. Sau, and R. Murch, "A New Empirical Model for Indoor
Propagation Prediction," IEEE Trans. On Vehic. Tech.,Vol. 47, No. 3, pp.
996-1001, Aug. 1998.
Webmaster's Note: What's New on SSS-Mag
By Karen Edwards
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