I'm currently working in Dept. of Computer Science of University Colorado Boulder, as a research faculty from Oct. 2017. Since I've been worked in wired and wireless telecommunication industry for more than 15 years, I participated to develop many different network systems such as Ethernet switch, IP router, WiMAX/LTE base station, LTE EPC, LoRa gateway, etc. Basically I'm a software engineer who loves to define a network reference diagram and to specify/implement L2/L3 protocols between them. I'm also familiar with the cellular network planning with performance analysis and its optimization.
I was the official secretary of IETF 16ng WG in 2007-2010. I'm a co-founder of PLNetworks Inc. I'm a co-author of NextEPC, which is an open-source implementation of the 3GPP LTE Evolved Packet Core. I received my B.S. degrees in industrial engineering and computer science from POSTECH in 2000. I received my Ph.D. from Seoul National University, Korea in 2015.
I have an extensive experience in Linux and open source projects. In particular, I have been working on an open source project aiming at releasing a publicly available Evolved Packet Core (EPC) implementation. My expertise includes Linux Kernel drivers and applications, 3GPP standards (5G, 4G/LTE, WiMax), and other emerging standards such as LoRa.
Recently I'm doing research on the LTE public safety communication, client-side network inference, mobile cellular infrastructure, and 5G low-latency backhaul.
Oct 2017 - Present
I'm working with Prof. Sangtae Ha in Internet Systems Lab (ISL). The ISL is part of the Network and Security Research (NSR) Group, which is led by three faculty members (Eric Keller, Eric Wustrow, and Sangtae Ha), and is also part of the Computer Systems Group at the University of Colorado Boulder.
- LTE public safety communications research
- Client-side LTE channel inference
- Portable and mobile LTE infrastructure
- Physiological sensing with IoT
Jan 2017 - Present
NextEPC is a software solution for LTE and 5G core network entities.
- Private enterprise cellular
- Multi-access edge solution for 4G/5G
- 4G/5G network virtualization
Jan 2015 - Oct 2017
PLNetworks provides LoRa-based IoT (Internet of Things) solutions (https://www.lora-alliance.org) including LoRa modules, LoRa-integrated sensor devices, relay, LoRa gateway, and application servers. I'm a co-founder of PLNetworks Inc.
- Private LoRa-based IoT network provider at a low cost
- Korea Railroad Research Institute adopted PLNetworks' products and won the award of the UIC Global Research & Innovation 2016 for the IoT-based realtime freight cars and hazardous freight monitoring system.
Aug 2010 - Oct 2017
Principal Research Engineer, SW Team Leader
Juni established in Sydney, Australia in 1988, has grown to become a multinational company providing the latest wireless telecommunication technologies around the world. Juni is now an enterprise small cell developing company, and I am the team leader of software R&D including the developments of LTE protocol stack, self-organizing network functions, small cell virtualization, RAN sharing, and neutral host small cells.
- Charter Communications (2017): Showed Citizen Broadband Radio Service (CBRS) LTE small cell using a DOCSIS backhaul.
- Google (2016-2017): Showed the world's first Spectrum Access System (SAS)-based LTE small cell.
- Fujitsu Japan (2015-2017): Research on the coexistence of WiMAX and LTE-TDD systems. Developed a neutral host LTE small cell.
- Korea Telecom (2015-2017): Showed the world's first backpack-typed LTE small cell for public satefy. It was shown on 2018 Winter Olympics in PyeongChang, Korea.
- Telstra Australia (2015-2016): Developed Single Radio Voice Call Continuity (SRVCC) that ensures the continuity of VoLTE calls under limited LTE coverage.
- China Mobile (2015): Showed a network listening mode for the auto-configuration of LTE cells.
Apr 2004 - Feb 2008
POSDATA, founded in 1989, is one of the largest system integrators in Korea and is a leader in Mobile WiMAX products and technology. With R&D centers in the US and Korea, POSDATA is very active in developing core OFDMA technology, creating mobile broadband products, and supporting trials for service providers inside and outside of Korea based on the IEEE 802.16e standard.
- Development of Mobile WiMAX (IEEE 802.16d/e) protocol stack
Jan 2000 - Apr 2004
Corecess is a device vendor of Ethernet switches, IP routers, and xDSL products. Founded in 1997, it has grown to over $266M in sales in 2002 working with Yahoo Broadband Japan owned by SoftBank.
- Development of L2/L3 protocol stack
2007 - 2010
16ng WG in IETF was organized to specify the operation of IPv4 and IPv6 over IEEE 802.16, taking into account the IPv4, IPv6 and Ethernet Convergence Sublayers. Five RFCs are published: RFC 5692, RFC 5948, RFC 4968, RFC 5121, and RFC 5154.
2007 - 2008
Member of Standardization Experts Group
TTA, founded in 1988, has played a key role in ICT standardization, testing and certification in Korea.
- Gyuhong Lee*, Jihoon Lee*, Jinsung Lee, Youngbin Im, Max Hollingsworth, Eric Wustrow, Dirk Grunwald, and Sangtae Ha, This is Your President Speaking: Spoofing Alerts in 4G LTE Networks, ACM MobiSys, Seoul, South Korea, 2019 (* both authors are equally contributed, 40 out of 172 = 23.2\% acceptance rate). Best Paper Award at MobiSys 2019.
- Jihoon Lee, Jinsung Lee, Youngbin Im, Sandesh Dhawaskar Sathyanarayana, Parisa Rahimzadeh, Xiaoxi Zhang, Max Hollingsworth, Carlee Joe-Wong, Dirk Grunwald, and Sangtae Ha, CASTLE over the Air: Distributed Scheduling for Cellular Data Transmissions, ACM MobiSys, Seoul, South Korea, 2019 (40 out of 172 = 23.2\% acceptance rate).
- Max Hollingsworth, Gyuhong Lee, Jihoon Lee, Jinsung Lee, Youngbin Im, Eric Wustrow, Dirk Grunwald, and Sangtae Ha, Demo - This is Your President Speaking: Spoofing Alerts in 4G LTE Networks, ACM MobiSys, Seoul, South Korea, 2019.
- Sandesh Dhawaskar Sathyanarayana, Jihoon Lee, Jinsung Lee, Youngbin Im, Parisa Rahimzadeh, Xiaoxi Zhang, Max Hollingsworth, Carlee Joe-Wong, Dirk Grunwald, and Sangtae Ha, Demo - CASTLE over the Air: Distributed Scheduling for Cellular Data Transmissions, ACM MobiSys, Seoul, South Korea, 2019.
- Shinik Park, Jinsung Lee, Junseon Kim, Jihoon Lee, Sangtae Ha, and Kyunghan Lee, ExLL:An Extremely Low-Latency Congestion Control for Mobile Cellular Networks, ACM CoNEXT, Heraklion/Crete, Greece, 2018 (32 out of 185 = 17.3% acceptance rate).
- Youngbin Im, Jinyoung Han, Ji Hoon Lee, Yoon Kwon, Carlee Joe-Wong, Ted Taekyoung Kwon, and Sangtae Ha, FLARE: Coordinated Rate Adaptation for HTTP Adaptive Streaming in Cellular Networks, The 37th IEEE International Conference on Distributed Computing (ICDCS 2017), Atlanta, GA, USA, June 2017.
- Wonjun Yoon, Ji Hoon Lee, Ted "Taekyoung" Kwon, and Yanghee Choi, Adaptive Access Control for a Femtocell Network, in Proc. KICS Conference 2010 Fall, Seoul, Korea, November 2010.
- Youngbin Im, Hakyung Jung, Ji Hoon Lee, Wonjun Yoon, Ted Taekyoung Kwon, and Yanghee Choi, Vertical Handovers in Multiple Heterogeneous Wireless Networks: A Measurement Study for the Future Internet, in Proc. International Conference on Future Internet Technologies (CFI) 2010, Seoul, Korea, June 2010.
- Obaid ur Rehman, Ji Hoon Lee, and Ted Taekyoung Kwon, MBMS Performance Improvement Mechanism for UMTS, in Proc. KICS Conference 2009 Fall, Suwon, Korea, November 2009.
- Junho Suh, Ji Hoon Lee, Ted "Taekyoung" Kwon, and Yanghee Choi, Qualitative Analysis in PMIPv6-based Mobile Multicast Solutions, in Proc. KICS Conference 2009 Fall, Suwon, Korea, November 2009.
- Ji Hoon Lee, Sangheon Pack, Taekyoung Kwon, and Yanghee Choi, Proactive Transmission-based QoS Provisioning for Multicast and Broadcast Services in Mobile WiMAX Systems, in Proc. ACM Workshop on Mobile Internet Through Cellular Networks (MICNET), MobiCom'09, Beijing, China, September 2009.
- Ji Hoon Lee, Junho Suh, Ted Taekyoung Kwon, and Yanghee Choi, An Efficient Mechanism for IP Multicast Group Management in Wireless Networks, in Proc. Korea Computer Congress (KCC) 2009, Jeju, Korea, July 2009.
- Jaecheol Kim, Ji Hoon Lee, Taekyoung Kwon, and Yanghee Choi, Wireless Access Network Selection for Live Streaming Multicast in Future Internet, in Proc. International Conference on Future Internet Technologies (CFI), Seoul, Korea, June 2008.
- Ji Hoon Lee, Soyoung Park, Chulhyun Park, Taekyoung Kwon, and Yanghee Choi, The Effects of ARQ Timers on TCP Performance in IEEE 802.16 Systems, in Proc. Korea Computer Congress (KCC) 2008, Phoenix Park, Gangwon-Do, Korea, June 2008.
- Hakyung Jung, Ji Hoon Lee, Chulhyun Park, Youngbin Im, Taekyoung Kwon, and Yanghee Choi, A Femtocell-based Testbed for Evaluating Future Cellular Networks, in Proc. International Conference on Future Internet Technologies (CFI), Seoul, Korea, June 2008.
- Ji Hoon Lee, Sangheon Pack, Taekyoung Kwon, and Yanghee Choi, Location Management Area (LMA)-based MBS Handover in Mobile WiMAX Systems, in Proc. IEEE International Conference on Communications System Software and Middleware (COMSWARE) 2008, pp. 341-348, Bangalore, India, January 2008.
- Bokgyun Jeon, Hojin Lee, Ji Hoon Lee, Taekyoung Kwon, and Yanghee Choi, MBS Rate Adaptation Scheduling Scheme in IEEE 802.16e, in Proc. KICS Conference 2007 Fall, Seoul, Korea, November 2007.
- Ji Hoon Lee, Sangheon Pack, Taekyoung Kwon, and Yanghee Choi, Reducing Handover Delay by Location Management in Mobile WiMAX Multicast and Broadcast Services, IEEE Transactions on Vehicular Technology, vol. 60, no. 2, pp. 605-617, February 2011.
- Jaechel Kim, Ji Hoon Lee, Hojin Lee, Taekyoung Kwon, and Yanghee Choi, A Network Selection Scheme for Multicast Applications in Wireless Network Convergence, Wireless Communications and Mobile Computing, published online, DOI: 10.1002/wcm.1032, October 2010.
- Ji Hoon Lee, Junho Suh, Ted Taekyoung Kwon, and Yanghee Choi, Wireless Host Agent (WHA)-based IP Multicast Group Management Scheme, Journal of KICS, vol. 34, no. 10, pp. 1004-1012, 2009.
- Ji Hoon Lee, Yerang Hur, and Kyoungjun Kim, Apparatus and Method for Providing Virtualized Communication Cell, Korea patent No. 10-1871852 (filled on Jul. 28 2017, issued on Jun. 21, 2018).
- Ji Hoon Lee, Seongdong Park, Yanghee Choi, and Youngbin Lim, Wireless Base Station Caching and Providing Data and Operating Method thereof, Korea patent No. 10-1821154 (filled on Feb. 28 2012, issued on Jan. 17, 2018).
- Ji Hoon Lee, Jongdae Jung, Kangmin Lee, Dohoon Lee, and Kyoungsoo Lee, Basestation for Performing Synchronization based on Signal and Operating Method thereof, Korea patent No. 10-1793731 (filled on Apr. 28 2016, issued on Oct. 30, 2017).
- Yerang Hur, Ji Hoon Lee, Hwayong Jung, and Kyoungjun Kim, System and Method for Interference Mitigation, Korea patent No. 10-1530375 (filled on Sep. 27, 2013, issued on Jun 15, 2015).
- Yerang Hur, Jungnam Yun, Jihoon Lee, and Hwayong Jung, Device and Method for Radio Resource Management, Korea patent No. 10-1485499 (filled on Feb. 23, 2013, issued on Jan. 16, 2015).
- Ji Hoon Lee, Mingu Cho, Shinhaeng Oh, Jinyoung Han, Taekyoung Kwon, and Yanghee Choi, Automated Method for Composing Internet Video Diary and System using the Same, Korea patent No. 10-1126526 (filled on Sep. 28, issued on 2010 Mar. 7, 2012).