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Special Report ­
Information Technology

 April 1997



photo of cell phoneSoftware 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The End of Outdated Cell Phones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"This could signal the end of outdated cellular telephones," he added.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."

The Bradley Department of Electrical Engineering
Virginia Tech

Last Updated, June 10, 1997
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