Distributing Wireless Signals in Buildings


October 1, 2004

Professor of ECE Dan Stancil was issued a patent last summer for his method to distribute wireless signals through buildings using heating, ventilation, and air conditioning (HVAC) ducts. Part of a long-term project with the Center for Wireless and Broadband Networking (CWBN), the research uses multiple input, multiple output (MIMO) techniques to increase the duct’s channel capacity.

“This approach is being actively researched for conventional wireless networks, and makes use of multi-element antenna arrays,” Stancil, who directs the center, explained. “To implement similar ideas in the duct, we would use multiple coupling probes into and out of the duct.”

ECE graduate students Ben Henty and Jess Hess are helping with the system; Ben is spending six months in Norway with the team’s corporate sponsor, YIT Building Systems, to deploy a large-scale wireless test network using ducts (this test system will not use the most recent patent).

“I'm enthusiastic about ventilation ducts as an enabler for wireless communication indoors and the early results here in Norway are very encouraging,” Henty reported on his progress converting their research into a functioning product. “It's exciting as an engineer to see something that has been quite theoretical actually work in a practical setting.”

Current wireless performance indoors is often irregular in part due to a wide variety of building materials. Hampered by the need for many test measurements and dead spots, designers can be unwilling to make firm bids for new wireless installs. The HVAC duct concept provides an advantage over today’s methods, according to Henty, because the ducts carry the radio waves directly to the users, circumventing (no pun intended) the losses due to the building structure.

Previous collaborators on the study include Stancil’s students Ahmet Cepni, who completed his M.S. on the HVAC project, and is now continuing his Ph.D. in another area, and Ph.D. student Pavel Nikitin. ECE Professor Ozan Tonguz and his student Ariton Xhafa also contributed to the group.

Along with YIT Building Systems, the National Science Foundation is funding the patent, with past support from ABB Corporate Research.

Members of the project team in front of a large-scale test network at the National Robotics Engineering Consortium (NREC) laboratory in Pittsburgh. L-R: Ahmet Cepni, Ozan Tonguz, Dan Stancil, Pavel Nikitin, Ariton Xhafa.

This figure illustrates how a duct network would work.