“A critical factor affecting the wide-scale deployment of wireless ad hoc networks is network capacity,” asserted Thomas Hou, associate professor of electrical and computer engineering at Virginia Tech.

A key technology to increase the capacity of wireless networks is called multiple-input-multiple-out (MIMO). It means the use of multiple antennas at both the transmission and the receiving ends. The objective is to improve communication performance.

“Unfortunately, existing models for this technology are either too mathematically complex to be used or too simple to be accurate,” Hou said. “As a result, research progress on multi-hop multiple-in-multiple-out ad hoc networks remains stagnant despite rapid advancements in this research at the physical layer.”

Hou, who received an Office of Naval Research Young Investigator Award in 2003 and a National Science Foundation CAREER Award in 2004 for his research on optimizations and algorithm design for wireless ad hoc and sensor networks, developed a few novel ideas on how to increase the capacity for wireless networks.

Hou, who has coedited a textbook on cognitive radio communications, collaborated with Scott Midkiff, professor and head of the Bradley Department of Electrical and Computer Engineering at Virginia Tech, on his ideas. Together, they have now received a little over $1 million from the National Science Foundation for two projects on wireless network research. On one of the projects, Hanif Sherali of Virginia Tech’s Grado Department of Industrial and Systems Engineering is also a co-principal investigator.

“We expect our research to be potentially transformative. With one of the two projects, we believe our work will serve a critical need in advancing multi-hop multiple-in-multiple-out network research by exploring new models beneath the network layer that are both tractable and accurate.”

Sherali, a University Distinguished Professor and W. Thomas Rice Chaired Professor of Engineering in the College of Engineering at Virginia Tech, is an expert in designing and analyzing mathematical models. Working with Hou and Midkiff, the three also say they hope their work will result in the development of new cross-disciplinary wireless networking curricula, as well as research opportunities for both undergraduates and graduates.

With the second project, they will be exploring cooperative communications where each node is only equipped with a single antenna and spatial diversity is achieved by exploiting the antennas on other nodes in a network. They will focus on designing network level algorithms based on cooperative relaying that can maximize throughput.

“Cooperative communications is well recognized as a key technology to increase throughput and reliability of wireless networks,” Hou said. “Although advances in this technology have been made, many fundamental problems remain open at the network layer.”

Using multiple antennas such as the multiple-in-multiple-out for spatial diversity is not always practical, Hou said. If this is the case, then cooperative communication can be used. In this technology each node is equipped with only a single antenna and spatial diversity is achieved by exploiting the antennas on other nodes in the network through cooperative relaying.

He again pointed to the solutions that he, Midkiff, and Sherali will be working on -- new algorithms to advance the state of the art in wireless network capacities.

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