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statement saying that it would
consider new services in the white
spaces as long as they do not
interfere with other nearby existing
wireless services. TV broadcasters
have really fought against that, but
so have the wireless microphone
manufacturers and users. They claim
their low power microphones will be
widely interfered with. Tests by the
FCC, however, say this isn’t so.
60 GHz — THE
WIRELESS FRONTIER
When you start running out of
spectrum space, you start looking for
more spectrum. However, keep in
mind that spectrum is like land: There
is only so much of it to go around.
The spectrum is owned mainly by
countries and a handful of large
companies. We’ve used up just about
all of it.
One solution would be to make
better use of what you have. For
radio, that means sharing frequencies
and/or using clever modulation and
multiplexing techniques. TDMA,
CDMA, and OFDM already make it
possible for cell phone operators to
squeeze more subscribers per Hz of
spectrum space than ever before.
There is spectrum available in the
30 to 300 GHz range — super the
extremely high frequencies. In fact,
these are so high they’re only a bit
below the infrared (IR) optical
spectrum. This wavelength is so
small, it is commonly referred to as
millimeter (mm) waves. The problem
with using these frequencies is that it
is very difficult to make electronic
components work at these
frequencies. Current semiconductor
technologies are now allowing radios
to be made. One other downside is
that such waves are easily scattered
and won’t penetrate walls. Existing
applications are in mostly military
radar and satellites, but also in some
short-range backhaul for networks
and cellular systems.
There is also an unlicensed band
open for use in the 57 to 64 GHz
range. Some have already targeted
60 GHz as a band where very high
speed digital data can be transmitted
at rates of up to about 10 Gbits/
second. One application already
available is called WirelessHD: a
wireless technology that lets you
transmit uncompressed, high
definition TV (1.5 to 3 Gb/s
depending on level of definition)
over several meters.
WIMAX NOW OUT THERE
WiMAX, of course, is the high
speed wireless metropolitan area
network (MAN) technology that was
created to compete with DSL and
cable TV Internet access. It uses
OFDM in the 2.3 to 2.5 GHz bands
in the US, and 3. 5 GHz in Europe
and other parts of the world. For
people in remote and rural areas
without Internet access services,
WiMAX provides a high speed
connection (> 1 Mb/s) to the Internet
for anyone within range of a
basestation. WiMAX is widely
deployed outside the US for
telephone service (Voice over IP),
as well as Internet connectivity.
Adoption of it has lagged in this
country mainly because companies
have struggled with business models,
as well as technical problems. Now,
Sprint Nextel has launched its first
commercial WiMAX service in
Baltimore. Called XOHM, this service
is expected to roll out over the US
as Sprint and wireless innovator
Clearwire build out a nationwide
system. It is a fourth generation (4G)
technology that could eventually
include voice service that is in direct
competition with existing wireless
operators. There are no WiMAX cell
phones yet, but you can get WiMAX
USB dongles, PC cards, and modems
for home and office use. Intel has
chips that will put WiMAX into
laptops in the near future. With this
service and no fixed contract, you
get high speed Internet connectivity
that easily competes with Wi-Fi hot
spots, as well as some 3G cell phone
data services. Look for XOHM in
Chicago and Washington, DC soon.
Go to the Sprint XOHM website for
details. NV
