New Chip Will Enable Larger Multiple Antenna System

By Marlys Amundson

A research group in the UCLA Henry Samueli School of Engineering and Applied Science has developed a revolutionary integrated circuits chip for wireless communications that could lead to more reliable broadband Internet connections and crisper cellular phone calls.

Electrical engineering professor Babak Daneshrad and Jingming Wang (PhD ’05) have designed a very large scale integration (VLSI) chip capable of meeting the tremendous processing power demands required for successful MiMo communications.

Multiple input, multiple output (or MiMo) technology is a communications technique that uses multiple antennas to send and receive wireless signals. When received, the combined signals are decoded, allowing more data to be transmitted without increasing bandwidth requirements.

The theories behind MiMo are well established and UCLA is one of a handful of experimental testbeds in operation around the country. Most of these are testing systems of four or fewer antennas on both the transmitting and receiving ends.

“The processing power required to realistically test the theories behind MIMO is horrendous,” explains Daneshrad. “To do what we want to – to develop an eight-by-eight MiMo configuration – would take about 20 high-end digital signal processing chips, or roughly 200 times more processing power than is needed for a cell phone.”

Wang has designed, developed, and fabricated a VLSI chip capable of supporting an eight-by-eight MiMo configuration transmitting a billion bits of information per second, more than 10 times as much as wireless local area networks (LANS), although it will run in the same bands.

As it decodes the signals using a matrix inversion operation, the powerful chip will process 40 to 50 giga operations (gops) per second for a bandwidth of 10 to 20 megahertz. In comparison, a general purpose T1 digital signal processor operating 700 megahertz handles only 1.4 gops per second.

“It’s pushing the envelope relative to what is currently available,” notes Daneshrad, “by about two orders of magnitude. We’ll be able to leverage the chips that we’ve built in experimental wireless communications.”

The team plans to make Wang’s chip the heart of an eight-by-eight MiMo testbed. UCLA researchers will create boards with processors to support the non-computational intensive operations of the receivers and transmitters, and communicate with the VLSI chips.

The UCLA system will use two of the new chips, each of which will support the processing computations for 12.5 megahertz of bandwidth. The breakthrough technology allows the researchers to come up with a realistic form factor for the testbed, which is both area and power efficient.

“UCLA offers specialization in both signal processing communications and implementation,” says Wang, who is working at Marvell Technology Group. “To have strengths in theoretical testing and implementation is a huge advantage for the group and very sought after in industry.”

From the program’s inception, the research group has been exploring the MiMo system from several viewpoints, including algorithmic and theoretical simulation issues and practical issues through experimental testbeds.

The project elements they have completed thus far – including the VLSI chips – will feed into a third prototype system running gigabit per second transmission rates. The group’s first setup was a two-by-two MiMo system running on a PC, and the second phase will be a four-by-four system running real-time on a couple of programmable semiconductor devices (field programmable gate arrays) with limited bandwidth and small data rates.

“Our goal,” says Daneshrad, “is be the first to demonstrate gigabit per second wireless networking with 25 megahertz of bandwidth. It’s ambitious, but in two years, we’ll have a working demonstration unit.”

Main Image: Multiple input, multiple output (or MiMo) technology is a communications technique that uses multiple antennas to send and receive wireless signals