Global Positioning System Reference
In-Depth Information
Either the radio is there or not; if present, signal strength may give a very rough
approximation of range. The radio environment propagation statistics are very
complex, especially within the built environment, so finding position on signal
strength alone tends to be unreliable.
The importance of bandwidth and signal-to-noise ratio was discussed. More
power is needed for a greater bandwidth signal (i.e., a signal modulated with more
information). And when accuracy is needed, the greater the signal-to-noise ratio,
the better, since noise (or random signal-level fluctuations) gets translated into
timing errors.
Near-field communications (NFC) was discussed since this mode of radio is
now widely used in RFID systems and has the advantage of not only providing
communications and positioning, but also transfering power to operate a simple
RFID tag's electronics.
A review was made of all the most common radio systems including GNSS,
cellular radio, hotspots, and radio tags. GNSS is set for a major enhancement in
the medium term when GPS is joined by the EU Galileo system and others.
Accuracy, availability, and resilience will be increased and commercial services
will be launched offering service guarantees.
The most recent transponder tags use ultrawideband nanopulse
communications that is perhaps the most interesting new radio technology for
positioning indoors. It has very high accuracy combined with all the other
advantages of radio.
As the wireless becomes more widespread as the scope of the digital
networked economy increases, truly ubiquitous positioning looks increasingly
achievable in the medium term.
References
[1]
Straw, R., Dean, Ford, S.R., and C.L. Hutchinson,
The ARRL Handbook for Radio
Communications 2006
, American Radio Relay League (ARRL).
[2]
Amos, S.W.,
Scroggie's Foundations of Wireless and Electronics
, 11th Edition, Newnes,
Oxford, UK: Boston, MA: 1997
[3]
Ralph, D., Searby, S., (eds.), “Location and Personalisation,”
BT Technology Journal
,
Volume 21, No. 1, Jan. 2003.
[4]
Bross, M., Smyth, P. (eds.), “Telecomms Unplugged,”
BT Technology Journal
, Volume 21,
No. 3, Jul. 2003.
[5]
Dennis, R., Wisely, D., “Mobility and Convergence,”
BT Technology Journal
, Volume 25,
No. 2, Apr. 2007.
[6]
Rosum
, http://www.rosum.com/, Jan. 2008.
[7]
Kaplan, E.D.,
Principles and Applications Understanding GPS
, Norwood, MA: Artech
House, 1996.
