Fwd: "Overcoming Spectrum Scarcity"
wa7nwp at gmail.com
Thu Aug 30 11:10:13 PDT 2012
Hams 'could be' leaders in efficient spectrum usage. :(
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From: <n6ze at aol.com>
Date: Tue, Aug 28, 2012 at 8:09 AM
Subject: [PNWVHFS] "Overcoming Spectrum Scarcity"
To: n6ze at aol.com
>From "The Institute" (13AUG12), an IEEE on-line news source. Written
by Kathy Pretz (c)
"With the exploding popularity of all things wireless, the radio
spectrum has become a scarce commodity in many countries. The United
States, for example, will run out of radio spectrum by next year,
according to the U.S. Federal Communications Commission.
Radio spectrum, which is finite, must accommodate cellphone calls and
data traffic that is increasing at an unprecedented rate. Globally,
traffic on mobile broadband systems has grown so fast that current
levels already exceed predictions made in 2010 for 2020, according to
Huawei, a global information and communications technology provider,
Cognitive radio (CR) is one technology under development that could
allow spectrum to be used more efficiently. A CR transceiver scans for
unused bands and changes its transmission and reception parameters to
different frequencies during heavy data loads without interruption. It
also can listen for interference on busy channels and calculate a way
to reduce it so the channels may be used by more people.
IEEE Vehicular Technology Magazine devoted its June issue to CR,
explaining how it works and describing areas that could benefit from
A CHANGING LANDSCAPE
Spectrum is a scarce resource, but measurements reveal that several
licensed frequency bands are underutilized most of the time. The key
advantage of CR, also known as dynamic spectrum access (DSA), is that
it can sense an unused channel and switch to it.
CR is expected to operate in a large portion of the spectrum in the
future, according to IEEE Member Gabrield Porto Villardi, Senior
Member Giuseppe Thadeu Freitas de Abreu, and Member Hiroshi Harada,
the authors of “TV White Space Technology.” In their article, they
point out that deployment of CR technology is regulated today only in
the vacant channels or white spaces between TV channels. In the United
States, for example, those vacant channels lie in the range of 54 to
Vacant channels will be released by governments for new services,
according to the researchers. With new unlicensed RF devices—called TV
band devices or TVBDs—expected to operate in those channels,
regulators in Japan, Singapore, the United Kingdom, and the United
States have been rewriting their spectrum management policies. The
European Conference of Postal and Telecommunications Administrations
works with different allocations and has defined TVBD requirements in
the 470- to 790-MHz band.
The authors note that the FCC has established two categories for
TVBDs: fixed and personal portable devices. Fixed devices may use any
of the vacant U.S. TV channels 2, 5 to 36, and 38 to 51, with a power
of up to 1 watt (4 watts EIRP—effective isotropic-radiated power). The
devices may communicate with each other on any of those channels, and
also with so-called personal/portable devices in TV channels 21
through 51. Fixed devices also must be location-aware, query an
FCC-mandated database at least daily to retrieve a list of channels
usable at their location, and monitor the spectrum locally. They may
transmit only within the channels where the database indicates
operation is permissible and no signals are detected locally.
Personal/portable stations may operate only on channels 21 to 36 and
38 to 51, with a power of 100 milliwatt EIRP, or down at 40 mW if on a
channel adjacent to a TV channel. They may either retrieve a list of
permissible channels from an associated fixed station or use a lower
output power of 50 mW EIRP and use spectrum sensing alone.
According to the IEEE authors, the Japanese Ministry of Internal
Affairs and Communications is considering various uses for its TV
white space (TVWS) including advertising, traffic reports, sports and
cultural information, and weather forecasts. It also is looking at the
white spaces to establish a communications system for disaster areas.
The authors include a study of how a TVWS system could have assisted
with communications during the 9.0-magnitude earthquake that struck
Japan in March 2011.
The dynamic spectrum access techniques of CR also have the potential
for changing how cellular networks are formed, owned, and operated,
according to IEEE members Timothy K. Forde and Linda Doyle and
nonmember Justin Tallon in in their article “Dynamic Spectrum Access
Networks.” Cellular networks typically are owned and operated by
national or transnational companies. But the advent of TVWS systems,
the authors say, will let lots of suppliers—not just big
carriers—provide cellular service. A provider could be as small as a
single base station or access point. The researchers say there could
be a host of geographically distributed, independent service providers
offering services in uncoordinated, ad hoc ways.
The authors offer ways such providers could form coalitions that would
not require much planning or organization. For example, a physical
signature placed on each transmission could identify members of a
coalition and enable them to devise a handover process so mobile users
could move smoothly from one provider to the next. The authors
describe how the signature could be used with frequency-varying or
dynamic control channels. Embedded in the digital communications
signal, the signature could be easily generated, manipulated,
detected, and analyzed using simple transceiver architectures. The
feature would require little signaling overhead and be detected using
short signal observation times. Its detection would facilitate signal
acquisition and help establish a communication link.
“The system we proposed is an example of a more decentralized and ad
hoc network construction process whereby temporary service can be
offered to users without a huge amount of preplanning,” they write.
Once cognitive radio becomes a reality, it’s expected to be used in a
wide variety of applications, which several articles in the magazine
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