1. School of Electrical Engineering, Kookmin University, Seoul, South Korea
2. School of Electrical and Computer Engineering, University of Seoul, Seoul, South Korea
3. Memory Division, Samsung Electronics Company, Ltd., Hwaseong, South Korea
4. Department of Electronics Engineering, Korea National University of Transportation, Chungju, South Korea
5. Department of Convergence IT Engineering, Pohang University of Science and Technology, Pohang, South Korea