The Universal Handset – IEEE Spectrum

Now comes the more difficult job: You’ve got to come up with detailed designs for each piece. Fortunately, you won’t have to do that from scratch. Suitable designs for at least some of the larger building blocks—a DSP here, a general-purpose processor there—should be possible to find and license. After the hardware has been pinned down, you’ll need to pull together the software to run it, which itself should keep you and your team busy for a large number of programmer-years.

The next challenge is to verify that your radio works correctly. Unfortunately, even state-of-the-art simulation tools aren’t guaranteed to show system performance properly—and subtle errors here might be lethal for your product. Worse, many of the expected mobile services may be safety critical, so a tiny slip-up could be a literal killer, too.

One way to address this uncertainty is to go a step further than simulation: You can prototype the digital portion of your newly designed SDR system using one or more field-programmable gate arrays (FPGAs), integrated circuits that contain a vast number of logic blocks and potential interconnections. These devices can be configured after their manufacture to serve almost any purpose, constituting entire systems on a chip.

The problem with FPGAs for production is that they are the energy hogs of the semiconductor world, lacking the power-management features of their hardwired counterparts. Moreover, FPGAs suffer from the integrated-circuit equivalent of suburban sprawl, taking up a relatively large area on a silicon wafer. They are also expensive, which helps to explain why we haven’t seen FPGAs being used to manufacture SDR handsets—at least not yet. A few researchers are exploring low-power FPGA technologies, so it’s not out of the question that they could one day serve for high-volume production of handsets.

In the meantime, FPGAs remain a convenient way to build and test SDR prototypes. Among the most interesting examples of this is the Berkeley Emulation Engine 2 (BEE2) project at the University of California, Berkeley. This test-bed setup consists of five high-performance FPGAs, which with proper programming can be turned into various next-generation SDR systems. Another example of this approach is the SDRâ¿¿based design effort at San Diego State University, which became widely known through a 2007 article in DSP Magazine titled “How to Pack a Room of Analog FM Modulators Into a Xilinx FPGA.”

No doubt, many people are waiting for the day when they’ll carry just one handheld gadget they can instantly switch from cellphone mode to that of a satellite radio receiver, or from a wireless Web browser to a mobile TV set; indeed, their handset might carry out all of these functions at once. Others, including the world’s many technophobes, might be less enthusiastic about such a prospect. But SDR technology offers something for them, too—the possibility that their wireless equipment will eventually become smart enough to adapt to its communications environment all by itself.

A radio intelligent enough to reconfigure itself—perhaps by detecting free spectrum and switching its frequency of operation to claim it—would make wireless services cheaper and more reliable for their users, most of whom will not even be aware that such marvelous things are going on under the hood. As with SDR, this is a concept that Mitola promoted early on, in a 1999 article he wrote with Gerald Maguire Jr., of the Royal Institute of Technology, in Stockholm. They called it cognitive radio.

Ah, to have a radio that not only switches function on demand but also configures itself into the most effective form possible without its user even knowing it. Now that will be a truly universal handset.