July - 2003 - issue > Technology
Software Radio And The Spectrum Drought
Venkat Ramana
Tuesday, July 1, 2003
SOMETIME SOON, ONE COMMON HARDWARE will be able to run multiple wireless services, with software defining their functionalities,” predicts Dr. Vanu Bose, founder and CEO of Vanu Inc., the Cambridge, MA-based startup.

Currently, the hardware in each wireless device—digital or analog handsets, domestic cordless phones, two-way radios, even garage—is built to handle specific RF signal processing software. Wireless systems employ protocols that vary from one service to another. Link-layer protocol standards (2.5G, 3G, and 4G), existence of incompatible wireless network technologies in different countries inhibiting deployment of global roaming facilities, and problems in rolling-out new services/features due to wide-spread presence of legacy subscriber handsets have hindered wireless growth.

Software Defined Radio is a platform that seeks to integrate the protocols at the software level. Software-defined radio (SDR), refers to wireless communication in which the transmitter modulation is generated or defined by a computer, and the receiver uses a computer to recover the signal intelligence.

The most significant asset of SDR is versatility. Wireless systems employ protocols that vary from one service to another. Even in the same type of service, for example wireless fax, the protocol often differs from country to country. A single SDR set with an all-inclusive software repertoire can be used in any mode, anywhere in the world. Changing the service type, the mode, and/or the modulation protocol involves simply selecting and launching the requisite software, and making sure the batteries are adequately charged if portable operation is contemplated.

The ultimate goal of SDR engineers is to provide a single radio transceiver capable of playing the roles of cordless telephone, cell phone, wireless fax, wireless e-mail system, pager, wireless videoconferencing unit, wireless Web browser, Global Positioning System (GPS) unit, and other functions still in the realm of science fiction, operable from any location on the surface of the earth, and perhaps in space as well.

The FCC has shown keen interest in this space. Dale Hatfield, chief of the Office on Engineering and Technology, FCC, says it is “because of its potential impact on one of the agency’s core responsibilities—the management of the radio spectrum resource in the public interest; and the exploding demand for access to that resource.” The primary market is represented by the initial distribution of a block of spectrum through auctions, for example. In contrast to the primary market, the secondary—or after-market—is represented by the exchange of spectrum after the initial distribution. SDR—by cutting down the expensive custom-built equipment for lessors of spectrums—alleviates the spectrum drought, by helping the FCC “lease” the secondary spectrum for short-term use.

Vanu, Inc. was founded as a spinoff of the 1994-1998 SpectrumWare research project at MIT. SpectrumWare developed the technology needed to use commercial off-the-shelf (COTS) PCs as SDR platforms. The project’s novel aim was to use the general-purpose CPU of the PC as the SDR signal processing engine. In fact, SpectrumWare ran the SDR application as a normal process on top of a standard desktop operating system.

Software Radio (SWR) is a type of SDR that maximizes software reuse across platforms and hardware generations. The key technology that enables this is to write the signal processing software as an application-level program running on top of a standard operating system (whether on GP CPU, DSP, or other processing engine). In addition to reducing software development costs, use of application-level software and an OS allows the underlying hardware components to be upgradedwithout incurring the high cost of redeveloping the software.

“Vanu Software Radio (VSR) currently focuses on public radios which are not battery dependent,” says Bose. “Our real focus is on the infrastructure-side.” The wireless basestation implementation that VSR provides has a threefold value proposition. For example, at a base station where VSR is currently on trial, 25Mhz of the spectrum is digitized and streamed through HP’s Proliant servers, which in turn are interconnected by gigabit ethernet. “The processing equipment has become faster and cheaper every year, riding the Moore’s law curve. Telecom equipment has not ridden this curve, as everything was custom designed,” says Bose. “By being able to work over commodity components that get cheaper and faster every year, cost are reduced dramatically.”

This implementation of the architecture does not limit the system to GSM. Multiple standards can be run simultaneously. “Currently AT&T is running three networks around the country. We can bring that down to one network running three different applications. In effect, operating costs are reduced significantly. Upgrades and maintenance are now just a pure software download,” observes Bose. As long as the RF front-ends are capable of handling 5 MHz wide channels, the system can be upgraded to GPRS, EDGE, IS-95, 1xRTT, or WCDMA by simply downloading new software.

Public safety agencies’ communications is a big industry. Every agency—the police, fire, emergency, ambulances and so on—use different radios on different frequencies. There have been numerous instances when all these agencies turned up at a location, but could not communicate with each other. Vanu has been developing patch systems—boxes that sit in vehicles at the scene of emergency—so that by touching icons on the screen, users from different agencies can speak to each other.

Bose founded Vanu in 1998 with some angel funding, and focused in R&D for the first three years. “The SpectrumWare technology was pretty raw, and we spent time to develop this into viable products,” says Bose. First customers included Boeing and the DoD. “The focus on the infrastructure market has influenced our growth. Sales cycles in this space span over a few years, and since the last couple of years, we have been generating revenues,” says the CEO. “We will be in the handheld market in the next five years or so; I think it may take that long before the market is mature to handle true software radio potential.”

As the existing mainstream markets focus on applications where the flexibility offered by software radio is not absolutely necessary. In such applications, the additional cost to provide reprogrammable signal processing or agile transmit and receive hardware is difficult to justify. Also, a software reprogrammable processing engine flips more transistors than a dedicated circuit does to perform the same computation. Power consumption can easily be a factor of ten higher when comparing dedicated circuits to portable software for a DSP or GPP. This rules out software radio at present for most battery-powered applications. And finally, the FCC is concerned that these devices not make it easier than it is at present for software faults, hackers or viruses to cause a radio to transmit out of compliance. “But eventually, ongoing progress in component technology, software standards, and the regulatory environment will steadily grow the markets to which software radio is applicable,” says Bose.

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