RADIO MEASUREMENTS AND CHANNEL MODELING FOR UHF PASSIVE RFID APPLICATIONS

pogonotomygobbleAI and Robotics

Nov 15, 2013 (3 years and 8 months ago)

55 views


1

RADIO MEASUREMENTS AND CHANNEL MODELING FOR
UHF PASSIVE RFID APPLICATIONS


N. Venetas, A. Charitopoulos, S.P Savaidis, N.A Stathopoulos, P. Papageorgas

ΤΕΙ

of Piraeus, Dept. of Electronics, Thivon & P. Ralli, Athens
-
12244



ABSTRACT



UHF short range appl
ications and especially passive RFID (Radio Frequency Identifacation) systems have
drawn significant attention during last years. Numerous of industrial RFID implementations, including
navigation, toll ticketing and logistic systems are either in use or un
der development [1]
-
[2].

RFID systems consist of a reading device which probes the identity of tags located within its operating
range. Passive tags are actually collecting the RF signal energy emitted by the reader in order to respond
back with the transm
ition of their identification number. This simple backscattering operation principle
reveals that the RF signal strength emitted by the reader and impinging on the tag becomes the dominant
factor, which actually determines the operating range of such syste
ms. Therefore, radio propagation and
channel modeling of passive RFID systems is an issue that requires special attention [3]
-
[4].

Radio propagation and channel modeling studies in the UHF band has been thoroughly investigated during
last decades [5]
-
[8].

Nevertheless, UHF RFID applications demonstrate certain characteristics which
deviate from other systems operating at the same frequency bands e.g. mobile communication systems.
First, passive RFID operating distances range from some centimeters up to a f
ew meters. Therefore, unlike
the mobile communication systems the field measurements and modeling involves both near and far field
regions. Besides, the typical environment for RFID applications is an indoor one, where a lot of interacting
objects may caus
e multipath propagation conditions and/or temporary obstructions along the radio path.
Unlike other indoor radio applications the RFID systems are expected to have a dominant Line of Sight
component along with weaker multipath components causing signal fad
ings, which should be statistically
characterized in order to determine the actual system’s readability.

According to the above mentioned comments this paper provides signal strength measurements of reader’s
signal in different indoor sites. The measuremen
t procedures conform to the ones being used in mobile
communications operating approximately at the same frequencies [5]
-
[8]. The set of the acquired
measurements have been processed in order to extract statistical information concerning the signal’s
power

along the radio path.

Actually, the signal strength experiences rapid fluctuations (fast fading) due to small scale components of
radio propagation (multipath propagation) and slow fluctuations (slow fading) due to large scale
components (distance based
attenuation, variation of the environmental clutter). In this context, an
estimation of the average signal attenuation along the radio path is provided as an indication of the large
scale fading [8]. Next, signal’s fluctuations (fast fading) around the ave
rage value are being statistically
characterized [9]. Since, Line of Sight conditions prevail in passive RFID applications, the fast fading
statistics have been compared with the Rician channel model [10] in order to verify whether this model is
applicable

in RFID applications.





2

REFERENCES

[1]

Finkenzeller

K.
,
RFID Handbook
, John Willey
,

2003
.

[2]

Manish
B.
, Shahram

M.,
RFID Field Guide: Deploying Radio Frequency Identification
Systems
, Prentice Hall, 2005.

[3]

Mayer L.K., Wrulich M and Caban S., “Measure
ments and channel modeling for short range
indoor UHF applications”, in Proc.
“EuCAP 2006”
, Nice, France

[4]

Mitsugi J.,
UHF Band RFID Readability and fading measurements in practical propagation
environment
, Auto ID Lab Japan report.

[5]

Rappaport T.S. an
d McGillem C.D., “UHF Fading in Factories”,
IEEE J. Select.
AreasCommun.
, vol. 7, pp 40
-
48, 1989.

[6]

Lafortune J.
-
F. and Lecours M., “Measurement and Modeling of Propagation Losses in a
building at 900 MHz”,
IEEE Trans. Vehicular Technol.
, vol. 39, pp. 10
1
-
108, 1990.

[7]

Xia H.H., Bertoni H.L., Maciel L.R., Lindsay
-
Stewart A. and Rowe R., “Radio Propagation
Characteristics for Line
-
of
-
Sight Microcellular and Personal Communications,
IEEE Trans.
Antennas Propagat.
, vol 41, pp. 1439
-
1446, 1993.

[8]

Valenzuel
a R.A., Landron O. and Jacobs D.L., “Estimating Local Mean Signal Strength of
Indoor Multipath Propagation”,
IEEE Trans. Vehicular Technol.
, vol. 46, pp. 203
-
212, 1997.

[9]

Lee W.C.Y.,
Mobile Communications Engineering
, McGraw
-
Hill, 1982.

[10]

Bertoni H.L.
,
Radio Propagation for Modern Wireless Systems
, Prentice Hall, 2000.