ASIA - Taming the Wireless Wilderness

By Richard Harth

A haystack of wireless gadgets is growing by the day. From cell phones, tablets, and laptops to e-readers, baby monitors, and satellite-guidance systems, these tools have become our steady companions.

ASIA - Taming the Wireless Wilderness Image

Photo: Michael Goss

As IIT faculty members Xiang-Yang Li (Ph.D. CS ’01) and Erdal Oruklu (Ph.D. CPE ’05) explain, there’s trouble on the wireless ranch. Studies point to a 6,000 percent increase in mobile-data transmission since the advent of smartphones, threatening the entire system with a snarl of virtual traffic.

“All wireless communication signals travel over air using a specific radio frequency, or spectrum,” Li says. “If multiple stations transmit over the same radio frequency simultaneously in the same location, the result is interference and signal loss for the receivers.”

One promising approach to an overpopulated spectrum—cognitive radio (CR)—is the focus of Li’s and Oruklu’s new project, funded by a $498,122 grant from the National Science Foundation.

Li is a professor in the Department of Computer Science and director of IIT’s Wireless Network Research Laboratory. He has been actively involved in the design and instrumentation of two large-scale wireless networking systems, GreenOrbs and CitySee, which carry out real-time ecological surveillance through thousands of wireless sensor nodes in an urban section of Wuxi City, China.

Oruklu, an associate professor in the Department of Electrical and Computer Engineering and director of the Very Large Scale Integration and System-on-a-Chip Research Laboratory, will oversee hardware and software development as well as related circuits for CR devices.

As Li, principal investigator on the project, explains, “Cognitive radios are capable of monitoring, sensing, and detecting the conditions of their operating environment, and they can dynamically reconfigure their own behavior to best match those conditions.”

In order to prevent frequency bands from becoming clogged with messages, CR devices can talk to their neighboring devices and make appropriate choices. “In other words,” Oruklu says, “CR can achieve improved spectrum efficiency by optimizing the use of shared frequencies.”

To maximize spectrum availability through CR, a process of opportunistic spectrum access (OSA) is applied. This involves not only an evaluation of the existing frequency spectrum but also optimization of the temporal domain (by exploiting traffic patterns) and the spatial domain (by exploiting rarely used geographic regions).

ASIA - Taming the Wireless Wilderness Image

A mounted wireless sensor node used to collect data in Wuxi City, China.
Image used courtesy of Xiang-Yang Li

“Although OSA has many benefits,” Li says, “a number of challenges—including spectrum sensing, management, mobility, sharing, security, and efficiency—must be resolved before we can design an efficient wireless network system adopting it.”

Smart radio devices that optimize spectrum use require wise governments to implement the advances. In the case of the United States, the Federal Communications Commission presented the National Broadband Plan to Congress in 2010, with the aim of freeing up an additional 500 MHz of spectrum for wireless broadband use by 2020 to meet demand.

Li and Oruklu hope that cognitive radio strategies will play an integral part in a more robust wireless universe. They will apply and verify their methodologies and algorithms over the CitySee and GreenOrbs systems as well as a cognitive radio network in their laboratory.

More Online

IIT Wireless Network Research Laboratory: www.cs.iit.edu/~winet/index.html

Cognitive radio tutorial: www.radio-electronics.com/info/rf-technology-design/cognitive-radio-cr/technology-tutorial.php