By John Donovan,
Editor/Publisher, Low-Power Design
With seemingly everyone in the world over the age of six owning a smart
phone, the FCC estimates that the demand for wireless services will
continue to increase over 50% year-over-year. While the cellular network
load due to voice traffic has remained relatively flat, data traffic has
soared. Cisco reports that almost half of data traffic is streaming
video, and AT&T has discovered that the killer app on its network –
as in network killer – is the iPhone, with 4% of its iPhone customers
recently accounting for more than half of the data traffic on its 3G
network. This is a problem that isn’t going away anytime soon, and
cellular network operators are desperately trying to deal with a huge surge
in demand they hadn’t anticipated.
The most promising solution to spectrum congestion is cognitive radio
networking. Cognitive networks move intelligence to the edge of the
networks, enabling different transmitters to dynamically change their
frequency or modulation in order to avoid interfering with other stations
sharing the same portion of the spectrum. Cognitive radios need to be
able to sense and respond to the presence of other signals in their
intended operating bands, using advanced software radio techniques –
known as dynamic spectrum access – to minimize interference.
Spectrum management can be achieved one of two ways: by reference to a
central database or by dynamically responding to other signals.
Spectrum Bridge has developed a database approach to
frequency reuse for the TV white spaces, an approach which the FCC
recently approved. Under Part 15 of the FCC rules if you want to use an
unlicensed TV band device (TVBD) on these frequencies, you must first
check Spectrum Bridge’s database for a list of authorized channels at
your location and input the exact location of your device into their
database before proceeding.
While the database approach is very helpful, it’s a static solution to
the problem. The
Shared Spectrum Company (SSC) was recently granted
four patents that cover the basics of dynamic spectrum access:
determining spectrum availability within a network; monitoring and
detecting channel occupancy; detecting and classifying signals within a
channel; and implementing an efficient method for reusing spectrum while
mitigating interference. SSC has developed DSA-enabled cognitive radios
that can operate in the TV white spaces without causing interference to
other devices, thereby greatly increasing spectral efficiency and
improving quality of service over what has been impossible to date.
xG Technology Inc. claims to have built “the world’s
first carrier-grade cognitive radio cellular network” in Fort Lauderdale,
FL. The company’s xMax network automatically reallocates mobile units to
different frequencies in order to minimize interference and optimize
network utilization. While xG’s network technology is still in the trial
stage, it’s passed some preliminary
military testing and looks to be getting ready for
prime time.
Whether it’s xG’s cognitive radio network or someone else’s, dynamic
spectrum access—made possible by cognitive radio technologies—is a
potential game changer that could enable billions of humans—not to
mention the billions of machine-to-machine (M2M) devices now starting to
come online—to ‘share the air’ without fear of bringing networks to their
knees.
