 Software Radios:
The End of Outdated Cell Phones
 This semester,
Virginia Tech EE students are building software radios in the
first-ever course of its kind. Shown here, Jeannett Mulligan
tests a design.
Digital signal processing (DSP) chips are poised to change
wireless communications - and Virginia Tech students are pioneers
in both the research and education aspects.
"DSP chips will enable engineers to produce a hardware/software
solution. While the hardware continues to be used, the software
gets upgraded, i.e. a 'software radio,'" said Professor
Jeff Reed,
a DSP specialist and developer of Tech's new course, Digital
Signal Processing Implementation of Communications Systems.
"This could signal the end of outdated cellular telephones,"
he added. "Consumers will be able to upgrade their phones
with new applications - much like purchasing new programs for
their computers."
Effective DSP implementation is not simply a digital version
of an analog receiver. "DSP enables flexibility and allows
us to add more capability to the phone as the technology develops,"
he said "For example, we can more readily add various features
to the phones, such as paging, web browsing, and news alerts."
Another advantage is that software radios can support multiple
standards and flexibility in the quality of service. "In
the United States, we are seeing a fragmentation of cellular
standards, and software radios would enable travelers to overcome
the difficulties in going through areas that use different standards.
As you go into an area that uses different cellular communication
standards, the cellular telephone infrastructure could notify
your phone about the local requirements, and the phone would
automatically reconfigure for use in that area," Reed explained.
This would allow the different regions to adopt the standards
that best suit their environment.
"We can also envision the time when providers would want
to change their standards in real time, or choose variable quality
of service. If it's 5 p.m. and there is lots of activity, or
if a major accident ties up traffic in a region, and people get
on the phone, a provider can choose to lower the quality instead
of allowing the call to be blocked," he said.
"The true software radio in a hand set doesn't exist
yet," Reed said. "But we are implementing software
radio in the base stations. We are also moving toward DSP-based
wireless local loops replacing the desktop phone. A wireless
local loop would be less expensive than the current wired phone
and you wouldn't be tied to one service provider. Still another
application would be wireless local area networks (LANs), where
you bring in your laptop, open the screen, and you're connected
to the building's local network."
These applications, along with the theory and strategies of
DSP implementation, are being explored by students in Reed's
class. The first of its kind, the class is the second of three
being developed by the Department's Mobile and Portable Radio
Research Group (MPRG) through a grant by the National Science
Foundation (NSF) to improve the curriculum in wireless communications.
The class consists of a one-hour lecture and six hours of
laboratory work each week. "With more digital and software
implementation, computer engineering issues are becoming more
important for communications engineers," Reed said. "We
spent the first two weeks of class discussing computer architecture
and communication."
During the laboratory sessions, the 24 students are involved
in implementing DSP subsystems, such as demodulators, timing
recovery systems, spread spectrum direct sequences, adaptive
filters, and voice coders and decoders.
The course is geared toward semester-long team efforts to
design and build DSP-based wireless radio equipment. The teams
undergo industrial-style design reviews, where students are graded
not only on their design, but on how well they assess others'
designs. "If they can show us that they can think critically
about other designs, we know that they understand the concepts
involved," Reed commented.
"We are hoping that this class will foster a competitive
and entrepreneurial spirit among the groups and their designs.
The project will foster not only technical skills, but also organizational,
managerial, and communication skills displayed by the students.
These are the skills that will be demanded of tomorrow's wireless
engineers."
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