1. Information and Telecommunication Technology Center, Department of Electrical Engineering and Computer Science, University of Kansas, Lawrence, KS, USA. E-mail: hui@ittc.ku.edu
2. OpNeAR Lab, Erik Jonsson School of Engineering and Computer Science, The University of Texas at Dallas, Richardson, TX, USA. E-mails: {wxh063000, mrazora, mtacca, andreaf}@utdallas.edu