27-03-2014, 04:57 PM
RFID BASED VEHICLE TRACKING SYSTEM
RFID BASED VEHICLE TRACKING.pdf (Size: 1,005.21 KB / Downloads: 43)
INTRODUCTION TO RFID
Radio-frequency identification (RFID) is an automatic identification method, relying on
storing and remotely retrieving data using devices called RFID tags or transponders. The
technology requires some extent of cooperation of an RFID reader and an RFID tag.
An RFID tag is an object that can be applied to or incorporated into a product, animal, or
person for the purpose of identification and tracking using radio waves. Some tags can be
read from several meters away and beyond the line of sight of the reader.
An RFID tag is an object that can be applied to or incorporated into a product, animal, or
person for the purpose of identification and tracking using radio waves. Some tags can be
read from several meters away and beyond the line of sight of the reader.
What is RFID?
A basic RFID system consists of three components:
a) An antenna or coil
b) A transceiver (with decoder)
c) A transponder (RF tag)
Electronically programmed with unique information. There are many different types of
RFID systems out in the market. They are categorized according to there frequency
ranges. Some of the most commonly used RFID kits are as follows:
1) Low-frequency (30 KHz to 500 KHz)
2) Mid-Frequency (900KHz to 1500MHz)
3) High Frequency (2.4GHz to 2.5GHz)
These frequency ranges mostly tell the RF ranges of the tags from low frequency tag
ranging from 3m to 5m, mid-frequency ranging from 5m to 17m and high frequency
ranging from 5ft to 90ft. The cost of the system is based according to there ranges with
low-frequency system ranging from a few hundred dollars to a high-frequency system
ranging somewhere near 5000 dollars.
ANTENNA
The antenna emits radio signals to activate the tag and read and write data to it. Antennas
are the conduits between the tag and the transceiver, which controls the system's data
acquisition and communication. Antennas are available in a variety of shapes and sizes;
they can be built into a door frame to receive tag data from persons or things passing
through the door, or mounted on an interstate tollbooth to monitor traffic passing by on a
freeway. The electromagnetic field produced by an antenna can be constantly present
when multiple tags are expected continually. If constant interrogation is not required, a
sensor device can activate the field.
Often the antenna is packaged with the transceiver and decoder to become a reader (a.k.a.
interrogator), which can be configured either as a handheld or a fixed-mount device. The
reader emits radio waves in ranges of anywhere from one inch to 100 feet or more,
depending upon its power output and the radio frequency used. When an RFID tag passes
through the electromagnetic zone, it detects the reader's activation signal. The reader
decodes the data encoded in the tag's integrated circuit (silicon chip) and the data is
passed to the host computer for processing.
Frequencies
Like all wireless communications, there are a variety of frequencies or spectra through
which RFID tags can communicate with readers. Again, there are trade-offs among cost,
performance and application requirements. For instance, low-frequency tags are cheaper
than ultra high-frequency (UHF) tags, use less power and are better able to penetrate non-
metallic substances. They are ideal for scanning objects with high water content, such as
fruit, at close range. UHF frequencies typically offer better range and can transfer data
faster. But they use more power and are less likely to pass through some materials. UHF
tags are typically best suited for use with or near wood, paper, cardboard or clothing
products. Compared to low-frequency tags, UHF tags might be better for scanning boxes
of goods as they pass through a bay door into a warehouse. While the tag requirements
for compliance mandates may be narrowly defined, it is likely that a variety of tag types
will be required to solve specific operational issues.
Common Problems with RFID
Some common problems with RFID are reader collision and tag collision. Reader
collision occurs when the signals from two or more readers overlap. The tag is unable to
respond to simultaneous queries. Systems must be carefully set up to avoid this problem.
Tag collision occurs when many tags are present in a small area; but since the read time
is very fast, it is easier for vendors to develop systems that ensure that tags respond one at
a time. See Problems with RFID for more details.