Introduction
The
use of wireless technologies is by no means
a new concept. When people hear the word
wireless they are probably thinking of cellular
phones or pagers. However, there are several
different facets to using wireless connections
in the rural United States. In agriculture,
we have used CB radios, cellular phones,
radio, television and recently GPS to communicate
data. However, our information needs have
increased based on time and the amount of
data needed for decision making. In addition,
high-speed telecommunications in rural areas
are limiting and to implement a permanent
structure of wiring can be costly, location
prohibitive and time consuming. The use
of point-to-point wireless technologies
and wide-area wireless networks can help
solve some of these communication barriers
in addition expedite the ability to send
data to multiple locations at once.
What
is Wireless Technology?
Wireless
technology is the process of sending information
through invisible waves in the air. Information
such as data, voice, and video are carried
through the radio frequency of the electromagnetic
spectrum. The electromagnetic spectrum consists
of different levels of energy waves including
gamma rays, x-ray, ultraviolet light, visible
light, infrared, microwave and radio. The
equipment needed to send and receive information
via wireless has to be accomplished through
a modulator and demodulator. A modulator
is used to send the information wirelessly
into the air. A demodulator is used to convert
it from air waves to another use.
Electromagnetic
Spectrum
The
degree of data sent wireless depends on
its wavelength and frequency. Wavelength
is the length of the energy wave and frequency
is the number of times or cycles per second
the wave length occurs. Typically radio
frequencies have long wave lengths and low
frequencies making them ideal for communications.
There are several different bands within
the radio frequency section of the spectrum
creating different uses for communication.
Extremely
Low Frequency (ELF) < 3kHz Submarine
communications
Very Low Frequency (VLF) 3 kHz-30 kHz Maritime
communications
Low Frequency (LF) 20 - 300 kHz AM Radio
Medium Frequency (MF) 300 - 3,000 kHz AM
Radio
High Frequency (HF) or Short Wave (SW) 3
- 30 MHz AM Radio, Short Wave and Amateur
Radio
Very High Frequency (VHF) 30 - 300 MHz FM
Radio and Television Broadcasting
Ultra High Frequency (UHF) 300 - 3,000 MHz
Television and Cellular Phones
Super High Frequency (SHF) 3 and 30 GHz
Wireless Communications and Satellite Transmissions
Extreme High Frequency (EHF) 30 - 300 GHz
Satellite Transmissions and Radar
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Methods
of Wireless Connectivity
IrDA
IrDA
(Infrared Data Association) comes with most
laptops and PDAs and uses the infrared wavelength
on the electromagnetic spectrum. It needs
a clear line of site to operate. Typical
examples of using IrDA is "beeming"
electronic business cards between two PDAs,
remote control for your TV, or printing
from a laptop to a printer equipped with
a IrDA device. There is a limited use of
IrDA compared to other wireless technologies
today.
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HF,
SW, VHF, and UHF Radio Frequencies
Radio
frequencies use a radio transmitter in the
device to send and receive signals. One
example of using radio includes a wireless
keyboard and mice for your computer. These
devices can communicate up to 6 feet and
operate at 27 MHz. CB radios can also operate
at 27 MHz but can extend communication up
to 5 miles due to the radio transmitter
and tower capabilities. FM radios allowed
closed networks of communication within
short range distances. Most all FM frequencies
are also governed by the FCC and you pay
license fees to use specific frequency channels
depending on the use. In agriculture, wireless
meteorological stations, RFID readers for
livestock identification, and sensors use
frequencies between 20 MHz up to 900 MHz
and can wirelessly communicate weather data.
They have been economically feasible to
install and easy to operate.
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Wireless
3G and Cellular Technology
Cellular
technologies have been around for years
and also have direct applications in agriculture.
Today's third generation or 3G technology
delivers the capabilities of video, music,
voice, e-mail, and data transmission through
the use of cellular towers and specialized
equipment. This technology requires high-speed
communications between 384 kbps and up to
2 Mbps which is much different from today's
standard of cellular communication. Another
difference of this technology is that you
are always connected to the Internet and
that you will not need to dial to connect
to the Internet. However, several limitations
still exist for rural areas and that is
reluctance to several cellular phone towers.
In addition, this technology is still being
introduced so devices are not fully developed.
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Wireless
Networks
A
wireless network consists of several access
points for connecting computers, PDAs, or
other equipment with wireless network cards
in a nearby area to network or get access
to the Internet. There are two main standards
for wireless networking, Bluetooth and IEEE
802.11. Both Bluetooth and IEEE 802.11 networks
can coincide in the same environment but
each have different approaches to connectivity.
Bluetooth
can be used in any device computers, printers,
fax machines, GPS, cameras, and other devices.
Bluetooth consists of a microchip and software
within the chip called a link controller
that works to identify other Bluetooth devices
to send and receive data. It can send both
voice and data. It operates at 2.4 GHz radio
spectrum and is designed for a small proximity.
It can communicate up to 100 feet, however,
the average standard distance for reliable
use is typically within a 33 feet area.
Devices
connect with each other by examining each
other's profiles that are coded into the
devices. Profiles contain information about
the device, what it can communicate with,
and what it is used for. A connection of
two or more Bluetooth devices is called
piconet. If there are several devices near
each other the radio signals could have
some interference but are usually very unnoticeable.
Bluetooth networks are usually not very
large.
IEEE
802.11 is generally designed for large networks
and can carry a longer range of radio transmission
depending on the wireless setup of equipment.
It works by connecting the computer equipped
with a 802.11 network card to a wireless
access point and antenna. Any user within
the area of an access point could get onto
the network. However, it can use security
services using Wired Equivalent Privacy
(WEP) protocol to block unwanted traffic
onto a particular wireless network.
There
are four approved standards for 802.11:
802.11
- The original standard that allows for
speeds for up to 2 Mbps.
802.11a
- Operates between 5-6 GHz and applies to
wireless ATM systems and is used in access
hubs. It uses an orthogonal frequency-division
multiplexing allowing it to generate data
speeds as high as 54 Mbps but usually it
communicates at 6 Mbps, 12 Mbps, and 24
Mbps. It is used for short ranges between
25-75 feet. It is incompatible with 802.11b
and 802.11g.
802.11b
- Also called Wi-Fi and is backward compatible
with 802.11. It operates at 2.4 GHz and
offers data transmission at 11Mbps and is
less susceptible to multipath-propagation
interference. It has a range of 100-150
feet. This is the most common standard used
today.
802.11g
- This standard has just recently been introduced.
It operates at 2.4 GHz and offers wireless
transmission up to 54 Mbps. It has a range
of 100-150 feet.
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GPS
GPS
(global positioning systems) units use a
receiver chip and software to communicate
to specific satellites in order to determine
your location on earth. There is a network
of 24 GPS satellites that orbit the earth.
They are spread out enough that four should
be visible from any spot on earth at one
time. These satellites constantly transmit
signals on two frequencies, 1575.42 MHz
and 1227.60 MHz. Once the data of your location
has been logged it can be further communicated
through other wireless or non-wireless networks.
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Satellite
Internet and Video Connectivity
This
is broadcast connectivity between satellite
dishes and specific subscription paid service
satellites. Satellite television or Internet
can be achieved directly by sending a signal
from a large dish antenna to a geostationary
satellite. Geostationary satellites remain
in the same spot above the earth all times.
This guarantees signals being sent and received
without loosing connection to the satellite.
Sending the data to the satellite is called
uplink. The satellite receives the signal
through a transponder that converts it to
a different frequency and transmits back
to earth called downlink. Downlink speeds
are typically faster than uplink data speeds.
In order for this to work properly the look
angles of the satellite dishes need to be
pointed toward the communication satellite.
There is a great range of satellite data
transmission rates between 1,000 MHz to
several hundred GHz for data connectivity.
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Common
Applications of Wireless in Agriculture
and Natural Resources
There
are many applications in agriculture that
can use wireless technologies. Some examples
include:
- Monitoring
pesticide and herbicide applications.
- Animal
tracking and identification.
- Monitoring
water or flood levels.
- Indicate
warning for frost events.
- Monitor
crop health, rainfall, temperature and
other meterological data.
- Track
shipments of perishable crops and crop
inputs.
- Monitor
equipment movement and performance.
- Web
cameras to view hazardous or remote areas.
- Odor,
gas and other environmental indicators
for livestock housing facilities.
- Integrating
GPS data into Geographic Information Systems.
- Precision
agriculture applications in data collection
and reporting.
- Food
safety and security through continuous
tracking capabilities from production
(knowing what pesticides or other treatments
have been used) and packing and shipping
of products.
- Agro-Security
by reducing theft of farm products, vandalism
of property, and detection of bio-chemicals.
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Wireless
Use in Crop Management and Precision Agriculture
Field
sensors and other technologies and equipment
are getting better defined for crop production
use each day. Using principles and technologies
of precision agriculture we are constantly
collecting data along with GPS from various
sources of sensors, controllers, and other
hardware for use as standalone or integrated
into geographic information systems (GIS)
management software. Precision agriculture
applications have the greatest to gain for
a comprehensive data collection and reporting
system in order for all those involved to
make timely decisions.
Data
sources typically gathered for crop management
that can be shared through wireless technologies:
- Topo
and elevation mapping
- Soil
sampling
- Yield
monitoring
- Soil
electromagnetic conductivity mapping
- Satellite
and aerial imagery
- Soil
Moisture for irrigation needs
- Crop
input record keeping and tracking
- Crop
scouting of weeds, diseases, and insects
- Meteorological
data collection
Some
traditional limitations in collecting this
data includes timeliness of transferring
data to the appropriate locations or central
databases and loosing data from equipment
malfunction or battery loss. Data can be
collected in real-time or after a specific
process has been completed. Information
can also come in large sizes so the transfer
rate of data needs to be handled through
larger bandwidth and data storage capabilities.
Another benefit of using wireless technology
is that it can send several sources of data
in real-time to one central location like
a server database system. Allowing data
to be pooled to a central location allows
multiple users to utilize that data when
they need it. For example, weed scouting
data collected in the field from a consultant
using a handheld PDA equipped to a cellular
phone or local wireless network system relays
treatment information to office server.
Server-side software generates an appropriate
application map to grower and sent on to
commercial chemical applicator for application
at the same time.
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Resources
General
Information
Everything
Wireless - http://www.wireless.com
Bluetooth - http://www.bluetooth.com
Federal Communications Commission - http://www.fcc.gov/
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Satellite
Data Connectivity
AgriStar
Global Networks - http://www.agristar.com
C-Com Satellite Systems - http://www.c-comsat.com/
SkyTower Telecommunications - http://www.skytowerglobal.com
DTN SpeedNet - http://www.dtnspeed.net
(Kansas, Illinois, Ohio, Nebraska, Texas,
Indiana, Oklahoma coverages only)
Prairie iNet - http://www.prairieinet.net
(Iowa and Illinois Coverage only)
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Wireless
Equipment
Proxim
- http://www.orinocowireless.com
Linksys - http://www.linksys.com
Cisco - http://www.cisco.com
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Wireless
Sensors and Monitoring Systems
Spectrum
- http://www.specmeters.com
VitWatch - http://www.vitwatch.com
Adcon Telemetry AG - http://www.adcon.ro
FieldServer - http://model.job.affrc.go.jp/FieldServer/FieldServerEn/default.htm
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Traceability
and Documentation Software
Freshloc
- http://www.freshloc.com
CropVerifeye - http://www.cropverifeye.com/
Ag Code - http://www.agcode.com
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Bluetooth
Wireless GPS/WAAS Receivers
Socket
Bluetooth GPS - http://www.socketcom.com/
GPS Smart - Fortuna Electronics, http://www.fortuna.com.tw/GPSmart.htm
GPS 4400 - Navman, http://www.navman.com
GlobalSat - http://www.globalsat.com.tw/
TomTom - http://www.tomtom.com/
Crux II / BTGPS - EMTAC, http://www.emtac.com/
Pocket GPS Navigator - Pharos GPS, http://www.pharosgps.com/
Earthmate - Delorme, http://www.delorme.com/
Trimble - http://www.trimble.com
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Additional
Information on Handheld Computers and Bluetooth
GPS
For more information:
Nathan Watermeier
Agriculture and Natural Resources
Ohio Geospatial Program
OSU Precision Agriculture Team
email
Copyright 2004. Nathan Watermeier,
Ohio State University Extension
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