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Professor Ali Niknejad's other research focuses on the development of inexpensive radios for indoor wireless networks with ten times the bandwidth of conventional WiFi technology.

In UC Berkeley electrical engineer Ali Niknejad's imagination, tomorrow's personal computers will look more like iPods than laptop PCs. You'd carry all of your data in your pocket. Need a monitor? Walk up to a wall screen and forge an instant wireless link. Inside your office, the device might connect to the local WiFi network for online access. Step outside and the Internet connection seamlessly switches to cellular. Such a device would require either several radios capable of operating at different frequencies, or a single radio with a bit of brains and a lot of flexibility. Niknejad is working on the latter.

"We're trying to build a cognitive radio that would be aware of its environment," says Niknejad, a member of the Berkeley Wireless Research Center. "It would decide what specifications like frequency and power consumption are appropriate and adjust itself accordingly."

This integrated circuit, a highly-tunable wideband voltage-controlled oscillator, was designed and tested by graduate student Axel Berny, It will form the core of a universal frequency synthesizer chip for the cognizant radio. [View larger image]

The wireless world -- from Bluetooth mobile phone headsets to 3G networks -- is a mess of myriad technical specifications and standards. For example, most cellular phones in the United States operate in the 1-2 GHz frequency range. To complicate matters, a single cellular standard may be implemented in different bands depending on the country. As anyone who has traveled from the US to Europe knows, this makes global connectivity a big challenge unless you have a high-end phone loaded with components that can change from band to band. On the shorter range, wireless local area networks and Bluetooth devices occupy the 2-3 GHz bands while long-awaited ultra-wideband (UWB) promises high-speed delivery of multimedia content at still another frequency.

"You really need to have one device that communicates with a plethora of standards," Niknejad.

Not only would this enable single devices to access many wireless networks, the flexibility could keep new products from becoming outdated even before they hit the marketplace.

"By the time committees come up with a standard, and industry designs radios that meet the specifications, the technology is often obsolete," Niknejad says. "For example, we might use one modulation scheme today but in a year we'll probably find a better one."

The Cognizant Universal Radio (COGUR) that Niknejad is developing with graduate student Axel Berny and others was built from the bottom up to be flexible. The COGUR design combines analog and digital components into a single "programmable" system, Niknejad explains.

"We're figuring out how to put knobs in the building blocks of radio circuits," he says.

Already, the researchers have fabricated a key component for COGUR. A voltage-controlled oscillator (VCO) regulates the radio waves that carry a signal. The frequency of a traditional VCO can be tuned by about 10 to 20 percent up or down, but Niknejad and Berny's device is capable of 100 percent variation. For example, it can shift frequency from one gigahertz to two, or five gigahertz to ten. By adding a frequency synthesizer that Berny is now testing, "it could hit any frequency you want," Niknejad says.

Not only is the frequency programmable, but other variables are also tunable on the fly. Take power, for instance. A Bluetooth signal need only travel a few feet, requiring far less juice than, say, a cell phone conversation.

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"A cognitive radio will find the optimal current level to get the best performance without wasting power," Niknejad says.

Right now, the researchers are designing the various building blocks that they someday hope to combine into a fully functional cognizant radio. In the next few years, the goal is to integrate all of the components on a single piece of silicon that would not only make our wireless devices smarter and more powerful, but also smaller and cheaper.

"We're going for the holy grail here, putting an entire cognizant radio onto a single chip," Niknejad says. "Today's technology is almost there."

Ali M. Niknejad's home page

Berkeley Wireless Research Center

On-silicon Gigahertz Radio Exploration

Berkeley EECS Annual Research Symposium (BEARS) 2005

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