The Potential
for
Unlicensed
Spectrum
Can cognitive radio help mission-critical
users take advantage of unlicensed
spectrum opportunities?
By Rick Rotondo
I
It’s sometimes difficult to find a consensus on important
topics facing industry, government and mission-critical
entities. However, one area that has wide agreement is
that there is a shortage of spectrum needed to support the
increasing demand for increased voice, data, video,
telemetry and control applications.
Proof includes the FCC declaring a “looming spectrum
crisis,” as well as the public-safety D block spectrum tied
up by arguments and lobbying from cellular carriers that
they can put it to best use. The National Association of
Broadcasters (NAB) is fighting to preserve its spectrum
holdings and issued studies showing why broadcasters
should keep their spectrum and not have it auctioned to
mobile network operators. The Utilities Telecom Council
(UTC) asked the FCC for 30 megahertz of new spectrum
for the utility industry, along with access to the 4.9 GHz
spectrum, a band reserved for public-safety use.
Although there is general agreement that there is a
spectrum crisis, there is disagreement on who should get
any new allocations from the FCC. Many competing sectors make strong arguments for more spectrum, claiming
that others already have enough. However, there is an
increasing chorus of wireless experts who say that the crisis isn’t driven by a deficiency in the amount of spectrum,
but rather by lingering inefficiencies in spectrum use. The
experts claim that we don’t need more spectrum; we need
to use the spectrum we already have — both licensed and
unlicensed — more efficiently and effectively. One solution for this is cognitive radio networks.
Cognitive Radios and Networks
Cognitive or smart radios have been around for a
decade or more, and the Defense Advanced Research Projects Agency (DARPA) for military applications performed
significant early work. As the need for additional capacity
for public and private mobile networks began to surface,
cognitive radios were proposed and deployed as a solution
for various applications and users outside the military.
The FCC’s Public Safety and Homeland Security
Bureau (PSHSB) describes the concept and benefits of
cognitive radios systems with the following:
Cognitive radio has become an emerging advanced
radio technology that enables a radio device to monitor,
sense, detect and autonomously adapt its communications
channel access to the dynamic radio frequency (RF) environment in which it exists. In other words, cognitive
radio devices can sense, detect and monitor the surrounding RF conditions including interference and access
availability and reconfigure their own operating characteristics to best match those conditions. A cognitive
Snapshot
Survey
What Are Your
Spectrum Needs?
— Private-Safety Users —
I have
adequate spectrum
63%
I need more
spectrum for
voice and data
communications
23%
I need more
spectrum for data
communications only
6%
Snapshot
Survey
What Are Your
Spectrum Needs?
— Public-Safety Users —
I need more
spectrum for
voice and data
communications
29%
I have
adequate spectrum
41%
I need more
spectrum for voice
communications only
18.5%
I need more
spectrum for voice
communications only
8%
I need more
spectrum for data
communications only
11.5%
The results reflect a 95 percent confidence level with a ±5 percent margin of error.
The results reflect a 95 percent confidence level with a ±5 percent margin of error.
capability that can make real-time autonomous decisions
for radio operations can increase spectrum efficiency,
leading to higher bandwidth services, as well as reduce
the burdens of centralized spectrum management by
public-safety communications officials.
In short, cognitive radios can find under-used or
unused wireless frequencies and dynamically put them to
use in an opportunistic fashion. These radios can rapidly
scan multiple bands and adapt to use available frequencies, even if they are available for only fractions of a second, such as between other radio transmissions. Some
newer cognitive radios support advanced interference mitigation via powerful signal processing engines that allow
them to operate in RF environments that would otherwise
challenge conventional radios. These techniques allow
cognitive radios to extract latent capacity and bandwidth
from existing spectrum bands, while traditional dumb
radios would find those bands fully occupied or too filled
with interference.
Recently, the concept of cognitive radios has expanded
to cognitive networks. A cognitive network collects data
from individual radios and makes decisions that optimize
the deployment and operation of the entire network automatically and autonomously.
For example, a cognitive network could be deployed in
an emergency-response scenario where other communications networks may or may not be operating. The radios
would turn on and immediately begin sensing and mapping the RF environment. The network could then develop
its own channel plan and configure its radios. If RF conditions change because of the arrival of mutual-aid agencies
for example, the network will dynamically incorporate or
avoid channels based on the policies programmed into the
network management system. As a side benefit, these net-
works use software and onboard processing to reduce or
eliminate expensive and scarce wireless networking
expertise needed to initialize and set up the communications network.
The benefits of making the network cognitive don’t
stop there. Some vendors are building adaptable network
protocols into their systems that give them additional flexibility and robustness. For example, cognitive networks
are being designed to sense when a fixed tower or repeater
infrastructure is damaged or destroyed — as happened on
Sept. 11 — and instantly reconfigure itself to operate in a
mesh-networking mode that enables communications to
continue in the absence of fixed resources. When
resources become available, they are reincorporated automatically into the network.
Leveraging Unlicensed Spectrum
Previously, unlicensed spectrum and mission-critical
applications haven’t been considered in the same sentence. Traditional public-safety radios can’t proactively
mitigate interference and switch bands when unlicensed
spectrum resources become taxed by other users. There
was also a limited amount of spectrum available for unlicensed use at frequencies with good propagation and
building penetration. There is a lot of unlicensed spectrum
at 5 GHz and above, but range suffers when using these
high bands. The problems associated with unlicensed
spectrum — little of the long range, a lot of the shortrange type — seemed destined to keep it from being
leveraged and used by mission-critical users.
However, the FCC made more unlicensed and shareduse spectrum available that offers both significant bandwidth and good to great range. A prime example of this is
the newly available TV white spaces band. The majority
Snapshot
Survey
Is Interference a
Problem for Your Network?
Snapshot
Survey
Is Interference a
Problem for Your Network?
— Private-Safety Users —
— Public-Safety Users —
No
48%
Yes, at VHF
27%
Yes, at 800 MHz
10
2%
19%
Yes, at 800 MHz
13%
0
18%
Yes, at 700 MHz
5%
Yes, in unlicensed bands
33%
Yes, at UHF
9%
Yes, at 900 MHz
45%
Yes, at VHF
28%
Yes, at UHF
No
20
3.5%
Yes, at 4.9 GHz
30
40
50
Percentage of Respondents
0
10
20
30
40
50
Percentage of Respondents
The results reflect a 95 percent confidence level with a ±5 percent margin of error.
The results reflect a 95 percent confidence level with a ±5 percent margin of error.
of this spectrum lies in the 400 – 700 MHz range, so propagation and building penetration are good. In addition,
much of the country has 100 – 200 megahertz of this spectrum available. The FCC allotted other bands, such as
3.65 GHz, and indicated via a recently issued notice of
inquiry (NOI) that it’s strongly considering making more
spectrum available on an unlicensed and shared opportunistic use basis.
While the allocation of vast new unlicensed and shared
spectrum bands is significant, it’s the combination of this
spectrum coupled with advanced multiband cognitive
radio networks that is the real game changer. These systems can scan, analyze and use multiple frequency bands
simultaneously. If one channel or set of frequencies gets
crowded, these systems can instantly switch to new channels or even move bands to maintain robust connectivity
and bandwidth. With the ability to now detect and avoid
interference and instantly access hundreds of megahertz of
new and existing unlicensed spectrum, cognitive radio
networks can potentially offer mission-critical users and
applications a licensed spectrum experience using unlicensed spectrum.
handle more mission-critical traffic; and
■ Creates a self-deploying, self-configuring and selfoptimizing rapid response system that leverages onboard
software, low-cost processors and preloaded policies to
reduce the burden on over-taxed communications specialists, critical in high-stress disaster response scenarios.
Benefits for Mission-Critical
Communications
The following are just a few benefits of unlicensed
spectrum to public safety, utilities and other missioncritical enterprises:
■ Dynamically creates and delivers reliable bandwidth
out of underused and unlicensed spectrum to support
voice, data, video and location-based services without
requiring costly or scarce licensed frequencies;
■ Enhances and extends mobile communications networks without reducing availability and capacity of existing systems;
■ Enables nonmission-critical traffic to be moved off
public-safety bands and on to unlicensed or white-space
frequencies, increasing capacity of existing networks to
Cognitive Network Case Studies
xG Technology is the developer and manufacturer of
the xMax cognitive radio network system and has experience deploying and operating cognitive radio networks.
An xMax system deployed in Fort Lauderdale, Fla., for
more than 18 months covers an area of more than 32
square miles of an interference-rich urban environment.
The system has been in continuous operation during this
time using the 902 – 928 MHz industrial, scientific and
medical (ISM) band. Its detect-and-avoid technology
enables the system to recover significant amounts of latent
bandwidth by sensing and analyzing 18 channels every 30
milliseconds.
The same system has been deployed at Fort Bliss,
Texas, for evaluation as an in-garrison cellular network
using unlicensed frequencies. The Fort Bliss xMax system
is being displaced to the White Sands Missile Test Range
in New Mexico for the second stage of its testing and in
support of operational training exercises for a battalion
scheduled to deploy to Afghanistan in mid-2012.
There are also trials of the cognitive network system
being conducted with Townes Telecommunications in two
of its rural markets. These systems are now operational in
Lewisville/Stamps, Ark., as well as MacClenny, Fla.
Townes is providing mobile voice and messaging services
to its rural residents, businesses and educational agencies
via the system.
All of these deployments are taking advantage of the
cognitive network’s end-to-end IP architecture, optimized
session initiation protocol (SIP) signaling and patented
mobile VoIP technology. By leveraging these industry
A cognitive network collects data from individual radios and
makes decisions that optimize the deployment and operation of
the entire network automatically and autonomously.
standards, integration and interoperability with existing
infrastructure are simplified.
The Future
There is ongoing work in standards bodies worldwide
to incorporate cognitive technologies into existing and
new radio protocols. For example, Long Term Evolution
(LTE) Advanced is supposed to include self-organizing
network (SON) capabilities. However, the timing of these
and other features is in question.
Commercial companies are rapidly developing and
deploying new cognitive capabilities. This is important
because the FCC and other global regulatory bodies have
made new spectrum bands, such as TV white spaces and
other white spaces that require cognitive radio network
operation, available for immediate use.
Cognitive radio networks are delivering on the
promise of more efficient spectrum use by extracting
significant amounts of latent bandwidth from frequencies
that appear saturated or laden with interference. Some
cognitive networks offer other advantages as well,
including self-planning and organizing capabilities that
remove the burden of complex network configuration and
coordination by overtaxed communications specialists.
The technology has applications in both mission-critical
and commercial networks.
Given that we all share the same limited spectrum
resources, improving use across all wireless networks can
help relieve growing pressure on first responders, utilities
and other mission-critical users to forgo newly earmarked
frequencies or worse — lose frequencies they already use. ■
Rick Rotondo is vice president of marketing for xG Technology.
He has more than 20 years of telecom and wireless experience
from companies such as Motorola Solutions, MeshNetworks,
Lucent Technologies and Nortel Networks. Prior to joining xG,
Rotondo was co-founder and chief marketing officer of Spectrum
Bridge, responsible for planning and implementing the company’s
marketing and communications strategy. Email comments to
editor@RRMediaGroup.com.
RadioResource MissionCritical Communications delivers wireless voice and data solutions for mobile and remote mission-critical operations. The magazine covers business, public
safety, and regulatory news; case studies; in-depth features; innovative applications; product information and comparisons; emerging technologies; industry reports and trends; and
technical tips. In addition, each issue contains Public Safety Report, a special section devoted solely to the needs of the public safety community. Editorial content targets organizations
in the United States and Canada with mobile and remote communications needs, including public safety, government, transportation, manufacturing, utility/energy, business, and
industrial entities. To request a FREE subscription or get more information, go to www.mccmag.com. RadioResource MissionCritical Communications is published by the RadioResource
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Pandata Cor p. All rights reser ved. Reprinted from the August 2011 issue of RadioResource MissionCritical Communications. For more infor mation about
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