• P. Mähönen is with the Institute for Networked Systems, RWTH Aachen University, Aachen, Germany. E-mail: email@example.com.
• H. Zheng is with the Department of Computer Science, University of California, Santa Barbara. E-mail: firstname.lastname@example.org
For information on obtaining reprints of this article, please send e-mail to: email@example.com.