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General Packet Radio Service (GPRS) Data
The worldwide General Packet Radio Service (GPRS) system supports data transmis-
sion. Although the frequency in the United States is different than overseas, the data-
carrying capability is similar. The GPRS data system uses RF communications in the
800 to 960 MHz bands and the data bandwidth is at most 170 Kbps , but in practice, it’s
best to limit expectations to one-tenth of that. The range of transmission is similar to
cell phones and is subject to similar blackout zones according to geography. The pro-
tocol uses Global System for Mobile Communications (GSM) and Time Division
Multiple Access (TDMA) communications with narrowband GMSK-modulated com-
munications and Time Division Multiplexing (TDM). As such, users can negotiate for
more time slots and higher data bandwidth without a loss of accuracy. More info can
be found at www.gsmworld.com/technology/gprs/intro.shtml#a1a and at www.ieng
.com/warp/public/cc/so/neso/gprs/gprs_wp.htm.

Bluetooth
Bluetooth is an RF channel that is somewhat new and just coming into its own. It, too,
uses RF communication in the 2.4 GHz band and GFSK (frequency shift keying). It
uses spread spectrum communications (via frequency hops) among 79 different 1 MHz-
wide bands. It is meant for short, 10-meter-range communication. The data bandwidth
can be as fast as 723 Kbps, but practical limitations restrict the bandwidth to about half
that. This makes it poor for video, but good for Internet communications. It is adept at
overlaying an existing communication spectrum and coexisting with the communica-
tions traffic in it. Check out www.bluetooth.com and www.csr.com/enews/sw007.html
for further information.

Infrared Data Association (IRDA)
The Infrared Data Association (IRDA) standard link is an infrared channel that has been
around for some time. It uses infrared light for short-range communications of about 1
to 2 meters. It uses baseband frequencies modulated up to 1.5 MHz to transmit data at
up to 4 Mbps. It is commonly used for short communication sessions between computer
peripherals. The following web site and PDF files provide further details on IRDA:

www.irda.org/
www.irda.org/use/pubs/Overview.PDF
www.irda.org/design/infrared_data_communications_with_irda.pdf