1. USC/ISI, 4676 Admiralty Way, Marina del Rey, CA 90292-6695, USA
2. Klipsch School of Electrical & Computer Engineering, New Mexico State University, P.O. Box 30001, MSC 3-O, Las Cruces, NM 88003-8001, USA
3. Department of Electrical and Computer Engineering, George Washington University, 800 22nd St., Science & Engineering Hall, Washington, DC 20052, USA