Two year leave from Mar. 2006 to Feb. 2008.Portable medical system platform using Linux/Qt, 2013-2014.- Designing and developing a reference system platform (hardware/OS/software) based on Embedded Linux and Qt for portable medical imaging diagnosis system.Portable medical system platform using Android, 2012.- Designed and developed a reference system platform (hardware/OS/software) based on Android for portable medical imaging diagnosis system.Data forwarding management in delay tolerant networks, 2011-2012.- Designed a control mechanism to decide whether to forward data according to link status in delay tolerant networks consisting of Android smartphones.Android/iPhone APPs for hotel customer services, 2011.- Developed Android and iPhone client APPs and a DB server for hotel customer services. Interference mitigation in dual heterogeneous radios, 2010.- Analyzed the interference in wireless sensor networks whose cluster heads are equipped with dual heterogeneous radios of IEEE 802.11 and IEEE 802.15.4, and designed and implemented algorithms to mitigate the interference. Authentication and key management for wireless sensor networks, 2005.- Designed a public-key authentication protocol and a key management protocol suitable for wireless sensor networks. MPEG-4 streaming client for ARM, 2003.- Developed an MPEG-4 streaming client using the RTP/RTCP/RTSP and Qt library, and ported it on ARM9 target board.

IEEE 802.11n performance test, 2009.- Identified and characterized the flexibility inherent in IEEE 802.11n for performance improvement. Multihomed video delivery over 3 screen television (3STV), 2008.- Implemented a multi-way pervasive video delivery system using various access technologies of WiMAX, Wi-Fi bridging, 1xEV-DO, DSL, and Cable, and developed a multihoming module into Linux kernel 2.6, all of which were built in the Aware Home at Georgia Tech.Channel management in IEEE 802.11, 2007.- Designed a channel management algorithm in IEEE 802.11 using wireless sensor networks. Cue-based networking (CBN), 2007.- Developed a user-aware video delivery system using wireless sensor networks and RFID, and built it in the Aware Home at Georgia Tech.VoIP over Wi-Fi, 2006.- Designed optimization algorithms to improve VoIP call capacity over IEEE 802.11, and developed one of them into Linux kernel 2.6 in the real testbed and showed up to 300 % improvement.

Layer 2 tunneling protocol (L2TP), 2001.- Designed and implemented L2TP/PPP, which was deployed on GGSN to provide mobile users with secure access to ISPs. UMTS core network testbed development, 2001.- Designed an UMTS Core Network using a number of Cisco 3600/7200 routers and Linux/UNIX servers, and performed a benchmarking test of a variety of networking protocols such as GPRS, GTP, L2TP, PPP, IPSec, Mobile IP, AAA, RIP, OSPF, and BGP with KT-ICOM.

Security consulting methodology, 2000.- Designed a framework for security consulting methodology, and carried out security consulting services to SK Telecom and KOSCOM.

Single sign-on (SSO), 2000.- Designed and implemented a SSO system based on public-key infrastructure (PKI) using the RSA BSAFE cryptographic toolkits.Postprocessing of block-coded images, 1997.- Designed an efficient and fast-converging algorithm using projection onto convex set (POCS) theory to reduce blocking artifact appearing in block-coded images.2D wavelet transform (WT), 1996.- Designed a nonseparable filter banks using the quincunx sampling lattice for 2D wavelet transform, which minimizes aliasing energy causing annoying pattern in low bit rate coded images.Fast discrete cosine transform (DCT), 1995.- Designed a fast DCT algorithm with reduced multiplication stages and fewer numbers of additions and multiplications, which decreases propagation error appearing in the fixed-point computation.