`91.08 ~ `00.05Member of Technical Staff, LG Corporate Institute of Technology
`00.06 ~ `02.08Director of R&D Center, Telephus Inc.
`02.09 ~ `04.09Team Leader of Application Technology Team, R&D Center, S1 Corporation
`04.10 ~ `08.09Assistant Professor, Radio Science and Engineering, Chungnam National University
`08.10 ~ `13.09Associate Professor, Radio Science and Engineering, Chungnam National University
`09.06 ~ `09.12Invited Researcher, WBAN Research Team, ETRI
`10.01 ~ `11.01Visiting Professor, Dept. of ECE, University of California, San Diego
`13.10 ~ presentProfessor, Radio Science and Engineering, Chungnam National University
Reviewer and Senior Member of IEEE / Reviewer of PIER and JEMWA Editorial Member and Life Member of KIEES Life Member of IEEK Member of Project Evaluation Committee of KIAT Technical Expert Group Member of DTAQ