CPCC/Cal-(IT)² Poster Presentation Day for Local High-Technology Companies Takes Place

After a brief welcome by the companies, the students spread out between the lobbies of the two buildings, standing by their posters, ready to explain their research.

Enis Akay, who pursues research in physical layer (PHY) Multi-Input Multi-Output (MIMO) algorithms for IEEE 802.11 wireless local area networks (LANs), said he was very happy with the level of detail in the questions he received from Conexant employees: “They were eagerly asking me when I can have results for parts of my research and how they can access them. It felt great.” In fact, a large number of Conexant employees from across the continent and even Europe were in town for an IEEE 802.11 standards meeting and the poster event was very timely for the participating employees of Conexant and the CPCC researchers.

MIMO techniques are under close consideration by the IEEE 802.11 standardization group. A task group recently formed within IEEE 802.11 has targeted doubling the transmission rates of these wireless LANs. However, there are a number of different options with different tradeoffs. Enis Akay has recently combined space-time block coding with standard transmission techniques in 802.11 networks, achieving what he states as “maximum space and frequency diversity achievable in such networks.” He states he believes that his method provides the best alternative in terms of the diversity order of the transmission system, however he says he is considering additional techniques to provide “spatial multiplexing gain.” He says although there are some known such techniques that provide a large degree of spatial multiplexing gain (meaning higher transmission rates), they require feedback. His main interest is in coming up a technique that avoids the complexity of feedback while increasing the transmission rate.

Around the corner stood CPCC students Feyza Keceli and Inanc Inan, whose research is on a related aspect of 802.11 wireless LANs, the Medium Access Control algorithm or the MAC. “The MAC determines a major part of the overall system performance in wireless LANs” explains Inanc Inan. “It ensures channel access to all users in the network, in a fair and efficient way. Today wireless LANs are being used for real-time services, requiring Quality-of-Service support.” Contrary to the physical layer, where analytical techniques can be used to determine system performance, MAC algorithms are usually designed by heuristics. In order to study their performance, however, one needs to either have the system built, or have a simulation system. Feyza Keceli and Inanc Inan are in the process of building a simulation tool that will enable them to do research in the most recent version of the 802.11 MAC standard, known as 802.11e. “Without this tool, it is not possible to know how the MAC and the combined MAC and physical layer will perform” says Keceli. “Whereas after we build our tool, we will be able to introduce various bandwidth-demanding real-time services, such as High-Definition Television into the mix of services on an 802.11 network, and will be able to characterize system performance.” This turns out to be extremely important since the 802.11 community now requires system performance measured not at the physical layer but at the MAC layer. Keceli and Inan expect to get their simulation tool, being developed as a collaborative research project with a team from Conexant, completed by early fall.

At Mindspeed lobby, Ying Zhang described her work to Cal-(IT)² UCI Division Director Albert Yee. She builds ultra high-speed circuits employing silicon for the new Ultra Wide Band (UWB) frequency band requiring multi-GigaHertz bandwidth. “These huge bandwidths require new paradigms in circuit design,” she says. “New circuit topologies for low-noise amplifiers, mixers, power amplifiers, and frequency synthesizers are needed, and that’s where I do my research with CPCC member faculty Payam Heydari.” She was also impressed with the number and the level of detail of questions she received from her audience. “A number of Mindspeed employees have actually asked me to make a presentation in their lab next week” she says. (Later on, Ying Zhang actually spent the summer as an intern at Mindspeed Technologies.)

Next to her stood her groupmate Ahmad Yazdi. His work is also on UWB. “My work starts with analytical models” explains Yazdi. “Then, I design the circuits and work with circuit simulation software to simulate our circuits.” But he does not stop with simulations, in fact he needs to build as well as test his circuits in order to have the work accepted as a presentation in a conference. “We have been working Jazz Semiconductor,” explains Zhang’s and Yazdi’s advisor Payam Heydari, a CPCC faculty member. “In fact, my group has been designing and manufacturing about 6-7 high-performance ultra- high speed circuits every year for the last three years. We have developed a good deal of expertise in this area, useful for both wireless and wireline ultra high-speed applications,” says Heydari. He adds “commercial utilization of these applications is just around the corner.”

Among the presenters was second year UCI graduate student Lynn Zheng who will be receiving her Master’s degree this spring. Zheng has been studying resource allocation in fading ad-hoc networks with her advisor CPCC member Professor Hamid Jafarkhani and will be doing a summer internship at another Cal-(IT)² industry partner, Broadcom. “I was nervous about how it would go, what level of interest and questions I would get from those looking at my poster, but it has been very rewarding,” said Zheng. “I’ve talked with all levels of expertise from the novice to the experienced engineer. It was very exciting to see the level of interest and I think I actually learned a lot while describing my work.”

Another student who works with CPCC member Professor Hamid Jafarkhani is Yun Zhu. Her research area is an extension of space-time codes, which Professor Hamid Jafarkhani is one of the inventors of. Yun Zhu studies techniques known as differential modulation that are based on a space-time coding methodology known as orthogonal codes. These codes are a MIMO technique. Whereas basic MIMO techniques generally known as beamforming require channel state information at both the transmitter and receiver, the space-time block coding technique reduces that to channel state information at the receiver only. Differential techniques go one more step and remove the need to know the channel state information from the receiver. Yun Zhu is a third year Ph.D. student and expects to take her Ph.D. qualifying exam this fall.

Other participants included Nhi Pham and Byung Moo Lee. Nhi Pham, who was a 2003-2004 CPCC Fellow, works with CPCC affiliate member Professor Franco De Flaviis. In her research, she worked on miniature antennas that can be implemented on printed circuit boards. These antennas, called Meander Antennas, are accommodated on printed circuit boards in a back-and-forth pattern in order to minimize their dimensions. Pham’s work is on adding a small additional strip alongside the meander pattern that gives the antenna a second characteristic wavelength. Pham has been working with Skyworks on a number of related projects. Bung Moo Lee was also a CPCC Fellow in 2003-2004. He works with CPCC affiliate member Professor Rui de Figueiredo. His work is on linearizing power amplifiers for Orthogonal Frequency Division Multiplexing (OFDM) systems. OFDM is known for a high peak-to-average power ratio which requires the power amplifier being operated at a low-efficiency operating point. Linearizing the amplifier increases system efficiency as well as the cost of such systems which are commonly used, for example, in 802.11 wireless LANs.

“This is the beginning of a long-term research partnership with our donor companies,” said CPCC Director Ender Ayanoglu. “We will follow up with a Research Day at UCI where the companies and our faculty describe their research interests and activities. This will lead to a joint research program whose projects will be renewed every year.”

Dr. Mojy Chian, Senior Vice President, Core Technologies at Mindspeed, and CPCC Board Member, agreed, “The three companies see CPCC an extremely useful resource just across the street,” he said. “We are very keen on building on this relationship and putting an ongoing research program in place. This is just a first step and I know there will be more to come” he added.

Click here for the list of all poster presentations.