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If anyone finds an article or link to an item of general interest
email me and I'll post it on this page.
(I don't care if it talks about systems based on manufacturer's equipment other than what I sell.)
This page was last modified
Monday, June 09, 2008
B-K Electric, Inc.'s Government Sales Policy
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Posted on June 6th, 2008
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Posted on May 11th, 2008
Over the past five years, I’ve had the opportunity to study
many digital trunked radio systems used for public-safety
communication. Though I am sure there are some success
stories, my interest has focused on the systems that have
problems or do not meet the expectations of their users. A
very high percentage of the Nation’s digital trunked radio
systems are in this category. There is a clear pattern of
problems with digital trunked radio systems that are endemic
to the nature of the technology.
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Vocoder characteristics (Poor background
noise rejection) |
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Frequent dropouts and garbled audio caused
by multipath interference |
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Software defects |
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Long keyup delay and high latency |
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Unacceptably low battery life for handheld
radios |
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Poor system administration practices |
An equally high percentage of problems are attributable to
poor judgment in the initial system design and configuration.
Radio systems may be optimized at design time for high
capacity, wide area service, or good in-building coverage, but
they are almost never optimized for all three because of the
extraordinarily high cost. There is a trend to assume that
optimization must favor high capacity and wide area service
even when there is no compelling business case to do so. Many
contemporary digital public-safety radio systems are deemed
inadequate by police and fire users because first-responders
in metropolitan and suburban areas expect (and truly need)
excellent in-building coverage, even though their digital
trunked systems were not designed to provide it.
Specifications for good in-building coverage are almost always
compromised in favor of high capacity and wide area service
because of economics. This has resulted in numerous
communities not providing their police officers and
firefighters with adequate communications equipment which is
essential to employee safety and welfare.
The perceived need for wide-area radio interoperability
fosters the justification to compromise in-building coverage.
There is rarely sufficient money to do both. In reality,
police officers and firefighters in metropolitan and suburban
areas rarely need to communicate by radio over long distances,
and rarely need to roam very far out of their jurisdiction.
Reliable communication at the scene of critical incidents is
essential, and rarely extends beyond a few square block area.
Life safety of first responders is frequently dependent on
effective radio communication on the fireground and in police
tactical situations. Why has the emphasis in radio system
design shifted away from constructing systems that provide
this level of service?
In most of the cases I’ve studied, the police and fire
executives who were involved in the system procurement
honestly thought they would be getting a radio system that
provided excellent in-building coverage and are surprised when
it is not the case. Some refuse to believe there is a problem
and rely on the excuse that the system is performing in accord
with its design specifications.
Signal quality for digital radio systems is often
represented as a number between 1 and 5, and referred to as
Digital Audio Quality, or simply as
DAQ.
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DAQ 1 Unusable. Speech present but not
understandable. |
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DAQ 2 Speech understandable with
considerable effort. Requires frequent repetition due to
noise/distortion. |
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DAQ 3 Speech understandable with slight
effort. Requires occasional repetition due to
noise/distortion. |
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DAQ 3.4 Speech understandable without
repetition. Some noise/distortion present. |
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DAQ 4 Speech easily understood. Occasional
noise/distortion present. |
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DAQ 5 Speech easily understood. No
noise/distortion present. |
The most common coverage specification I’ve seen for
digital trunked radio systems requires a minimum DAQ of 3.4.
98% of the time, over 95% of the defined coverage area. This
is a very weak specification that will fall short of the
expectations of almost all first responders. This could be
interpreted to mean that it is acceptable for 2 minutes out of
every 100 minutes of radio traffic to be unintelligible. Or it
could mean that is is acceptable to have an unintelligible
signal in 5 square city blocks out of every 100 square city
blocks. Such a coverage specification is woefully inadequate.
For comparison, the generally accepted specification for
the municipal law enforcement radio systems in San Mateo
County, California is for a 100% full-quieting analog signal
to and from a mobile radio 100% of the time when the vehicle
is parked or in motion on a city street within its
jurisdiction. Nothing less is acceptable. The expectation for
portable radio coverage inside residential buildings and when
above grade is for easily understood communication in both
directions at least 99% of the time. I believe this is typical
of what most metropolitan and suburban police officers and
firefighters expect and need.
Why is it that digital trunked radio systems are rarely
held to the same, or higher standard of performance? Perhaps
because the systems would be too expensive to afford and too
complex to reliably maintain. Coverage specifications must be
low in order to keep the cost low enough to initially sell the
system. Of course, consultants and manufacturers will always
be available to sell additional infrastructure to improve
coverage.
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Posted on December 18th, 2007
Ada County Idaho was one of the first jurisdictions in the United States
to embark on a cutting edge 700 MHz digital trunked radio system. The
City of Boise is in Ada County and agreed to participate in the
countywide radio system. The Boise Fire Department purchased more than
one million dollars of 700 MHz digital mobile and portable radio
equipment with the expectation that the new equipment would provide the
best possible communication for its first responders. Unfortunately, the
Fire Department staff has determined that the digital radios would
present a risk to firefighter safety if placed into service. The radios
have not been deployed because of this issue.
Specifically, Boise firefighters have determined that voice
transmissions over the digital radio system are usually unintelligible
when a VibraAlert feature on a Scott SCBA is alarming, or when multiple
PASS alarms are sounding in the same area. The software used in the
digital radios that converts voice to digital data cannot isolate the
spoken voice from the noise. Voice transmissions are unintelligible when
the radios are used in a high-noise environment.
Boise Fire staff conducted extensive tests and determined that the
problem is endemic to the digital modulation used in the new radios. The
problem is not directly related to the 700 MHz frequency band or to
trunking, however the FCC requires that digital modulation be used in
700 MHz radio systems. The only reasonable conclusion is that 700 MHz
digital radio equipment is not suitable for use on the fireground.
In
2006, some fire departments discovered that the voice audio from
digital radios in the presence of background noise (common to
firefighting operations) will cause distortion to the degree of
unintelligibility. The International Association of Fire Chiefs (IAFC)
have established a working group to study this issue. The IAFC issued an
alert to its membership on March 20, 2007. There is no known workaround
or solution to this problem as of this writing.
Boise Fire Department and the other fire departments in Ada County will
remain on analog VHF radio systems.
The City of Boise Idaho has a population of about 201,000 residents,
however the metropolitan area has about 635,000 persons. The City covers
approximately 64 square miles.
Please contact me if you would like contact information at the Boise
Fire Department to hear this information first hand.
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Digital Radio Noise Problem: Best
Practices Solicited
http://www.iafc.org/displayindustryarticle.cfm?articlenbr=33964
Fairfax, Va., June 21, 2007... The
IAFC Digital Problem Working Group is actively working to identify the
causes and potential solutions for the digital distortion some users of
digital radio systems have experienced in high-noise environments. The
working group currently has two task groups working on different aspects
of the digital problem:
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The Testing Task Group is working with the National
Institute of Standards and Technology to identify scenarios to be tested
in an effort to objectively quantify the nature and scope of the problem
and potential solutions. |
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The Best Practices Task Group is working to identify
procedural and technical solutions departments may have successfully
implemented to address the problem. |
The Best Practices Task Group is soliciting input from users of radio
systems that use digital modulation. The task group is interested in the
steps user agencies have taken to address audio distortion problems they
have experienced in high-noise environments. These practices may be:
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procedural |
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technical adjustments to radio equipment |
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the use of specific radio accessories that have been
found to work well minimizing or mitigating digital audio distortion |
To submit a best practice online, go to
www.iafc.org/DigitalProblem and click on
the “Submit a best practice” button.
Where appropriate, the Best Practices Task Group will
forward the practices collected to the Testing Task Group for validation
and optimization.
For more information on the digital noise issue, visit the
IAFC website at
www.iafc.org/DigitalProblem.
-end-
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Common Fireground Noise May Cause
Unintelligibility of Digital Radio Transmissions
http://www.iafc.org/displayindustryarticle.cfm?articlenbr=33118
Fairfax, Va., Mar. 20, 2007...
The International Association of Fire Chiefs is alerting its members to a
potential issue and soliciting their input to a solution. The IAFC has
received reports of firefighters experiencing unintelligible audio
communications while using a digital two-way portable radio when operating
in close proximity to the low-pressure alarm of their self-contained
breathing apparatus (SCBA). In addition, other common fireground noise,
including powered tools, apparatus and PASS devices, may affect voice
intelligibility.
This is an industry-wide issue and is not specific to any
one manufacturer’s radios. There are indications that any digital voice
communication product utilizing parametric voice encoders could be
affected by this problem. The IAFC does know the problem is not related to
any specific radio spectrum, as it is not a frequency of operation issue,
or a particular communication standard.
Due to these reports, the IAFC board of directors has
asked the Communications Committee to form a working group to work with
other IAFC committees and sections and other appropriate organizations to
investigate and provide recommendations to address this concern. The
specific focus of the group will be to:
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Fully understand the facts and identify potential
solutions that may be required. |
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Facilitate industry collaboration among the
communications equipment manufacturers to explore options to mitigate or
eliminate this concern. |
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Recommend best practices for digital portable radio use
on the fireground. |
The IAFC is asking you to contact the Communications Working Group if you
have experienced similar issues. Go to
www.iafc.org/digitalproblem to learn more
about the tests you can conduct to provide the working group the
information it needs to study the issue and make recommendations.
Your input is vital to ensure that digital radio
technology can be effectively utilized in fireground applications. The
IAFC fully understands that many fire departments are using digital radio
systems with success, but there may be issues related to voice
transmission being interfered with or overridden when common fireground
noise is in the background.
We appreciate your assistance in testing your systems and
reporting back to us.
-end-
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International Association of Fire Chiefs
Digital Problem
The IAFC is alerting its members to a potential issue and
soliciting their input to a solution. We have received reports of
firefighters experiencing unintelligible audio communications while using
a digital two-way portable radio when operating in close proximity to the
low-pressure alarm of their self-contained breathing apparatus (SCBA).
Other common fireground noise, including powered tools, apparatus and PASS
devices, may affect voice intelligibility.
This is an industry-wide issue and is not specific to any
one manufacturer’s radios. There are indications that any digital voice
communication product utilizing parametric voice encoders could be
affected by this problem. The IAFC does know the problem is not related to
any specific radio spectrum, as it is not a frequency of operation issue,
or a particular communication standard.
Due to these reports, the IAFC board of directors has
asked the Communications Committee to form a working group to work with
other IAFC committees and sections and other appropriate organizations to
investigate and provide recommendations to address this concern.
If you have experienced similar issues, the
Communications Working Group needs to hear from you.
http://www.iafc.org/displaycommon.cfm?an=1&subarticlenbr=719
Digital Radio Test Protocol
Download these instructions (pdf)
The following is a set of instructions to test a digital portable
radio for interference in the presence of common fireground noises:
Test A:
- Use a portable radio on a digital channel.
Please identify the radio type.
- One firefighter will operate the power tools listed below at
full throttle while another firefighter stands directly next to the
one operating the power tool with the portable radio (approximately
3 feet between the radio and the device, apparatus and/or tool).
- A third firefighter, in a remote location, will monitor the
radio transmission.
- Once the power tool is operating at full throttle, the
firefighter with the portable radio will repeat, “MAYDAY, MAYDAY,
MAYDAY.”
- The firefighter monitoring radio traffic will document the audio
quality for each test as:
I – intelligible, able to understand the voice
audio message
U – unintelligible, unable to understand the
voice audio message
Record the mode as:
D – digital
A – analog
Use the following power tools, devices or apparatus as appropriate.
We recommend you test as many sources as possible:
K12 circular type saw
Chain Saw
PASS Device
High Apparatus engine idle
If your department uses Scott SCBA, perform the test while the
vibra-alert is activated in low air mode (in a safe environment).
Test B:
Repeat Test A using the same radio in the analog mode. |
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Interoperability: Stop Blaming the Radio
by Ronald P. Timmons
An EXCELLENT white paper on the dual problems of communications systems
that fail during emergencies
and
the personal dynamics of the failure of first responders to communicate
properly during stressful situations.
17 page .pdf:
timmonsoninteroperability-2007.pdf
A much longer (107 page) thesis from Mr. Timmons on why communications
fail.
ABSTRACT
Concerns about inadequate radio communications at the
scene of disasters predate 9/11, and have been a focal point of homeland
security funding since 2001. Under the umbrella term “interoperability,”
grant funding is facilitating the recent deployment of equipment to allow
field personnel to patch radio systems together, with the expectation of
immediate improvement of emergency scene communications dysfunction.
This thesis argues that there are numerous causal factors
for inadequate disaster communications. Communications impediments include
insufficient radio infrastructure, behavioral reactions by people in
stressful situations, intergovernmental relations, inadequate procedures
and training, and general lethargy over the need to institute special
operating policies differing from routine practices.
The sole reliance upon technological solutions,
without proportionate training and practice greatly reduces the
effectiveness of radio patching equipment. Quite opposite from the
intended effect, patching equipment, in the hands of those only minimally
acclimated to radio system architecture, is likely to trigger unintended
consequences of chaotic system overload (by combining two or more busy
channels) and sector vulnerability (by combining unsecured general public
systems with previously isolated public safety systems).
Our goal is to provide a thought-provoking examination of
the entire realm of emergency scene communications issues and practical
recommendations beyond superficial technological solutions.
107 page .pdf:
rtimmons_thesis_2006.pdf
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NFPA 1561
Standard on Emergency Services Incident Management System
NFPA_1561_Emergency_Services_IMS.pdf
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A "Must Read" Article
SPECIAL REPORT - United States Fire Administration - Technical Report
Series
Improving Firefighter Communications
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Another "Must Read" Article
NIOSH Firefighter Radio Communications -
CHAPTER III: FIREFIGHTER COMMUNICATION ISSUES
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