Sangtae Ha

Sangtae Ha

I am an Associate Professor in the Computer Science Department at the University of Colorado Boulder. My research focuses on building and deploying practical systems that span multiple disciplines including practical machine learning and deep learning systems, networks and distributed systems, internet protocols and algorithms, video streaming, storage systems, and wireless (LTE/5G/6G) networks and security. I lead the Internet Systems Lab (ISL).

Email: sangtae DOT ha AT colorado DOT edu

ECCR 1B14
1045 Regent Drive 430 UCB
Boulder CO, 80309-0430 USA



Sangtae Ha is an Associate Professor in the Computer Science Department at the University of Colorado Boulder. He was an Associate Research Scholar in the Department of Electrical Engineering at Princeton University from 2009 to 2013. He received his Ph.D from the Department of Computer Science at North Carolina State University in late 2009.

His research focuses on building and deploying practical systems that span multiple disciplines, including networks and distributed systems, internet protocols and algorithms, video streaming, storage systems, wireless (LTE) networks and security, and smart data pricing. He currently serves Chief Architect Officer (CAO) at Earable which aims at revolutionizing cognitive healthcare with smart earphones that improve human’s cognitive functions. He also serves the technical advisor for Myota, a storage startup spun off from his recent research in secure and reliable storage. Previously, he co-founded DataMi, a startup on wireless networks, in 2012, and served as the founding CTO/VP Engineering. He also co-founded Zoomi, which develops an artificial intelligence (AI) learning platform. He is a co-author of CUBIC (RFC 8312), which is the default TCP congestion control algorithm for Linux, Android and Windows, and is currently being used by the majority of Internet servers around the world and by several billion Android and Linux devices.


Selected Publications:

  1. Demystifying Commercial Video Conferencing Applications

    Insoo Lee, Jinsung Lee, Kyunghan Lee, Dirk Grunwald, and Sangtae Ha,
    accepted in ACM Multimedia, 2021 (542 out of 1942 = 27.9% acceptance rate)

  2. zTT: Learning-based DVFS with Zero Thermal Throttling for Mobile Devices

    Seyeon Kim, Kyungmin Bin, Sangtae Ha, Kyunghan Lee, and Song Chong
    ACM MobiSys 2021 (36 out of 166 = 21.7% acceptance rate, Best Paper Award)

  3. Securing the Wireless Emergency Alerts System

    Jihoon Lee, Gyuhong Lee, Jinsung Lee, Youngbin Im, Max Hollingsworth, Eric Wustrow, Dirk Grunwald, and Sangtae Ha,
    accepted in Communications of the ACM, 2021

  4. Exploiting Client Inference in Multipath TCP over Multiple Cellular Networks

    Sandesh Dhawaskar Sathynarayana, Jinsung Lee, Jihoon Lee, Dirk Grunwald, and Sangtae Ha,
    accepted in IEEE Communications Magazine 2021

  5. eMRC: Efficient Miss Rate Approximation for Multi-Tier Caching

    Zhang Liu, Hee Won Lee, Yu Xlang, Dirk Grunwald, and Sangtae Ha,
    USENIX FAST’21 (28 out of 130 = 21.5% acceptance rate)

  6. SPARCLE: Streaming Processing Applications over Dispersed Computing Networks

    Parisa Rahimzadeh, Jinsung Lee, Youngbin Im, Siun-Chuon Mau, Eric C. Lee, Bradford O. Smith, Fatemah Al-Duoli, Carlee Joe-Wong, and Sangtae Ha,
    IEEE ICDCS 2020 (18% acceptance rate)

  7. FluidMem: Full Flexible and Fast Memory Disaggregation for the Cloud

    Blake Caldwell, Youngbin Im, Sepideh Goodarzy, Sangtae Ha, Richard Han, Eric Keller, and Eric Rozner,
    IEEE ICDCS 2020 (18% acceptance rate)

  8. PERCEIVE: Deep Learning-based Cellular Uplink Prediction Using Real-time Scheduling Patterns

    Jinsung Lee, Sungyong Lee, Jongyou Lee, Sandesh Dhawaskar Sathyanarayana, Hyoyoung Lim, Jihoon Lee, Xiaoqing Zhu, Sangeeta Ramakrishnan, Dirk Grunwald, Kyunghan Lee and Sangtae Ha,
    ACM MobiSys 2020 (34 out of 175 = 19.4% acceptance rate)

  9. Towards Automated Network Management: Learning the Optimal Protocol Selction

    Xiaoxi Zhang, Siqi Chen, Youngbin Im, Maria Gorlatova, Sangtae Ha, and Carlee Joe-Wong,
    IEEE ICNP 2019 (short paper – 19.3% acceptance rate).

  10. ECHO: Efficiently Overbooking Applications to Create a Highly Available Cloud

    Parisa Rahimzadeh, Youngbin Im, Gueyoung Jung, Carlee Joe-Wong and Sangtae Ha,
    IEEE ICDCS 2019 (19.6% acceptance rate).

  11. This is Your President Speaking: Spoofing Alerts in 4G LTE Networks

    Gyuhong Lee, Jihoon Lee, Jinsung Lee, Youngbin Im, Max Hollingsworth, Eric Wustrow, Dirk Grunwald and Sangtae Ha,
    ACM MobiSys 2019 (40 out of 172 = 23.2% acceptance rate, Best Paper Award).

  12. CASTLE over the Air: Distributed Scheduling for Cellular Data Transmissions

    Jihoon Lee, Jinsung Lee, Youngbin Im, Sandesh Sathyanarayana, Parisa Rahimzadeh, Xiaoxi Zhang, Max Hollingworth, Carlee Joe-Wong, Dirk Grunwald and Sangtae Ha,
    ACM MobiSys 2019 (40 out of 172 = 23.2% acceptance rate).

  13. I Sent It: Where Does Slow Data Go to Wait?

    Youngbin Im, Parisa Rahimzadeh, Brett Shouse, Shinik Park, Carlee Joe-Wong, Kyunghan Lee and Sangtae Ha,
    EuroSys 2019 (45 out of 207 = 21.7% acceptance rate).

  14. ExLL: An Extremely Low-Latency Congestion Control for Mobile Cellular Networks

    Shinik Park, Jinsung Lee, Junseon Kim, Jihoon Lee, Sangtae Ha and Kyunghan Lee,
    ACM CoNEXT 2018 (32 out of 185 = 17.3% acceptance rate).

  15. Virtual Redundancy for Active-Standby Cloud Applications

    Gueyoung Jung, Parisa Rahimzadeh, Zhang Liu, Sangtae Ha, Kaustubh Joshi, and Matti Hiltunen,
    IEEE INFOCOM 2018 (309 out of 1606 = 19.2% acceptance rate).

  16. Calibrating Time-variant, Device-specific Phase Noise for COTS WiFi Devices,

    Jincao Zhu, Youngbin Im, Shivakant Mishra, and Sangtae Ha,
    ACM Sensys 2017 (17.4% acceptance rate).

  17. FLARE: Coordinated Rate Adaptation for HTTP Adaptive Streaming in Cellular Networks,

    Y. Im, J. Lee, J. Han, Y. Kwon, C. Joe-Wong, T. Kwon and S. Ha,
    IEEE ICDCS 2017 (90 out of 531 = 16.94% acceptance rate).

  18. SVC-TChain: Incentivizing Good Behavior in Layered P2P Video Streaming,

    P. Rahimzadeh, C. Joe-Wong, K. Shin, Y. Im, J. Lee and S. Ha,
    IEEE INFOCOM 2017 (292 out of 1395 = 20.93% acceptance rate).

  19. Performance Analysis of Incentive Mechanism for Cooperative Computing

    C. Joe-Wong, Y. Im, K. Shin, and S. Ha,
    IEEE ICDCS 2016 (68 out of 386 = 17.6% acceptance rate).

  20. Viability of Virtual Cloud Providers

    L. Zheng, C. Joe-Wong, C. Brinton, C. Tan, S. Ha, and M. Chiang,
    ACM SIGMETRICS 2016 (28 out 208 = 13.46% acceptance rate).

  21. T-Chain: General Incentive Scheme for Cooperative Computing

    K. Shin, C. Joe-Wong, S. Ha, Y. Yi, I. Rhee and D. Reeves,
    IEEE ICDCS 2015 (70 out of 543 = 12.89% acceptance rate).

  22. Secondary Markets for Mobile Data: Feasibility and Benefits of Traded Data Plans

    L. Zheng, C. Joe-Wong, C. W. Tan, S. Ha, and M. Chiang,
    IEEE INFOCOM 2015 (316 out of 1640 = 19% acceptance rate).

  23. CYRUS: Towards Client-Defined Cloud Storage

    J. Chung, C. Joe-Wong, S. Ha, J. Hong and M. Chiang,
    EuroSys 2015 (32 out of 150 = 21.33% acceptance rate).

  24. Sponsoring Mobile Data: An Economic Analysis of the Impact on Users and Content Providers

    C. Joe-Wong, S. Ha, and M. Chiang,
    IEEE INFOCOM 2015 (316 out of 1640 = 19% acceptance rate).

  25. When the Pricing is Right: Enabling Time-Dependent Pricing for Broadband Networks

    S. Sen, C. Joe-Wong, S. Ha, J. Bawa and M. Chiang,
    ACM SIGCHI 2013

  26. Offering Supplementary Wireless Technologies: Adoption Behavior and Offloading Benefits

    C. Joe-Wong, S. Sen and S. Ha,
    IEEE INFOCOM 2013, Turin, Italy

  27. AMUSE: Empowering Users for Cost-Aware Offloading with Throughput-Delay Tradeoffs

    Y. Im, C. Joe-Wong, S. Ha, S. Sen, T. Kwon and M. Chiang,
    IEEE INFOCOM 2013 (mini-conference), Turin, Italy

  28. TUBE: Time-Dependent Pricing for Mobile Data

    S. Ha, S. Sen, C. Joe-Wong, Y. Im and M. Chiang,
    ACM SIGCOMM 2012

  29. Joint VM Placement and Routing for Data Center Traffic Engineering

    J. Jiang, T. Lan, S. Ha, M. Chen and M. Chiang,
    IEEE INFOCOM 2012 (mini conference), Orlando, Florida, 2012

  30. Time-Dependent Broadband Pricing: Feasibility and Benefits

    C. Joe-Wong, S. Ha and M. Chiang,
    IEEE ICDCS 2011.

  31. DiffQ: Differential Backlog Congestion Control for Multi-hop Wireless Networks

    A. Warrier, S. Janakiraman, S. Ha and I. Rhee,
    IEEE INFOCOM 2009.

  32. CUBIC: A New TCP-Friendly High-Speed TCP Variant

    S. Ha, I. Rhee and L. Xu,
    ACM SIGOPS Operating System Review 2008.

  33. Stochastic Ordering for Internet Congestion Control and its Applications

    H. Cai, D. Eun, S. Ha, I. Rhee and L. Xu,
    IEEE INFOCOM 2007.

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Visit the publication of the ISL for a more complete list.


2019 Fall
  1. CSCI 4273: Network Systems
  2. CYBR 5010: Data Communicaitons
2018 Fall
  1. CSCI 4273/5273: Network Systems
  2. TLEN 5330: Data Communicaitons 1
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PhD Students
  1. Zhang Liu
  2. Parisa Rahimzadeh
  3. Ibrahim Ayad
  4. Siqi Chen
  5. Prasanth Prahladan
  6. Insoo Lee
  7. Jaeyoung Oh
  8. Hyoyoung Lim
  9. Jason Schnitzer
  10. Sandesh Dhawaskar
  11. Taeho Kim
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Visit the ISL people page for a more complete list.


Professional Services:

  • PC Co-Chair
    1. Fog World Congress, 2017.
    2. Asia-US Forum on Fog Networking for 5G and IoT, 2015.
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Campus Services:

  • Computer Science
    1. Computing Co-Chair, Fall 2016 – Current.
    2. Faculty Search Committee, Fall 2016 – Spring 2017.
    3. Graduate Committee, Fall 2014 – Spring 2016.
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We appreciate the funding from the following organizations.

Current Sponsors
  1. National Science Foundation (NSF)
  2. National Institute of Standards and Technology (NIST)
  3. Department of Homeland Security (DHS) and CIRI
  4. DARPA
  5. Cisco Systems
  6. ETRI
  7. UNIST and IITP
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