Subject: [NEXTEL-1] Megahertz Matters: Is Your Wireless Data Investment Riding on the Right Frequency?

From: [email-masked]
Date: Tue, 03 Aug 2004 14:39:38 -0400

Field Report

Megahertz Matters: Is Your Wireless Data Investment Riding on the Right
Frequency?

While most IT systems are driven largely by equipment and architecture,
wireless data communications depend on an additional factor: the
frequency on which the system operates. Whether you need to communicate
with a mobile workforce or public safety team, or maintain contact with
SCADA collection points across a large service area, the choice of
frequency for your communications system will go a long way toward
determining its success. 

>From tree foliage to weather and geography, a host of issues can affect frequency choices. Fortunately, most wireless decision-makers can rely on the expertise of trusted partners to help them make the right choice. “Regardless of who they partner with, however, wireless decision-makers should understand that products are designed to work at different frequencies… and different frequencies have different characteristics,” says Dataradio engineer Mark Christensen. 

“Generally, frequency choices are examined in the planning process and
evaluated with a propagation study,” says Christensen. “It helps to work
with a partner that has the expertise to make an accurate evaluation and
the selection of available solutions to make the right recommendation.”

"Even though we have significant security advantages, we cannot, and do
not, take security for granted."

Why some frequencies work… and others don’t.

VHF? UHF? What type of communications frequency is right for your
system? Radio frequencies are determined by wavelength, and different
wavelengths have different performance characteristics. A surprising
variety of factors go into choosing an appropriate operating frequency.
Below are some, but not all, of those factors:

Intended Use—Is your organization focused on delivering mission-critical
data? Your choice of frequency will likely include a licensed band—one
that ensures your system stays up and running during periods of
emergency or heavy use, when public systems may go down. 

Geography—Some frequencies have the ability to “crawl” across hills and
valleys to deliver better coverage with minimal infrastructure. Shorter,
higher frequencies require clearer lines of site to coverage areas, and
therefore require more towers to deliver that coverage. Other geographic
considerations include in-building coverage—something that can’t be
delivered using lower frequencies.

Foliage—Oddly enough, the wavelengths of certain frequencies match
perfectly with the characteristics of certain pine needles. In effect,
each needle acts as an antenna, absorbing the waves and resulting in
lost coverage. Leaves also affect coverage, and are considered in any
evaluation regardless of season. 

Distance—The longer waves of VHF travel farther, requiring less
infrastructure to support them. Shorter waves, such as those used by 2.4
GHz wi-fi solutions can deliver high-quality data solutions, but they
only work in limited areas. UHF bandwidth is an ideal choice for many
applications.

Infrastructure Needs—High-bandwidth applications usually have low-output
power restrictions, which requires more infrastructure. The cost of
maintaining additional towers can play an important role in frequency
determination. Not surprisingly, in many urban areas, real estate
expertise is as important as technical expertise in determining where
and how to handle infrastructure needs.

How Frequency Affects Wireless Design

Performance: Data-rich applications require higher frequencies. Most
SCADA and public safety operations do not require large-scale data
transmission.

Reliability: Licensed spectrum provides mission-critical reliability for
utility and public safety applications.

Infrastructure: Some frequencies require fewer towers, which means less
infrastructure to maintain.

Experienced Partnerships are Crucial to Wireless Design Decisions

While many wireless system decision-makers know that frequencies affect
performance, few are going to trust their own judgment to decide which
frequency is right for their application. “Whether or not you rely on
expert input to make a final decision, it is important to have a basic
understanding of frequencies when you are considering one product
against another,” says Christensen. “If they are not designed for the
same frequency, you may not be comparing apples to apples.”

To learn more about how Dataradio can help you determine the right
solutions for your wireless data implementation, visit www.dataradio.com

Source: http://www.dataradio.com/twdr/072904.html#2
DataRadio's Trusted Wireless Data Report - 07/29/04

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