1. Information and Telecommunication Technology Center, Department of Electrical Engineering and Computer Science, The University of Kansas, Lawrence, KS 66045, USA
2. Department of Computer Science, Naval Postgraduate School, Monterey, CA
3. Information and Telecommunication Technology Center, Department of Electrical Engineering and Computer Science, The University of Kansas, Lawrence, KS 66045, USA and School of Computing and Communications (SCC) and InfoLab21, Lancaster University, LA1 4WA, UK and Department of Computing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong