Qianru Li


I am Qianru Li, pursuing Computer Science Ph.D. at UCLA. I work in Wireless Networking Group (WiNG), supervised by Prof. Songwu Lu. Before that, I received Bachelor of Science in Computer Science from Shanghai Jiao Tong University in 2016. My research interest are in the area of cellular networks and mobile systems.




Beyond 5G: Reliable Extreme Mobility Management SIGCOMM'20

Yuanjie Li, Qianru Li, Zhehui Zhang, Ghufran Baig, Lili Qiu, Songwu Lu

Extreme mobility has become a norm rather than an exception. However, 4G/5G mobility management is not always reliable in extreme mobility, with non-negligible failures and policy conflicts. The root cause is that, existing mobility management is primarily based on wireless signal strength. While reasonable in static and low mobility, it is vulnerable to dramatic wireless dynamics from extreme mobility in triggering, decision, and execution. We devise REM, Reliable Extreme Mobility management for 4G, 5G, and beyond. REM shifts to movement-based mobility management in the delayDoppler domain. Its signaling overlay relaxes feedback via crossband estimation, simplifies policies with provable conflict freedom, and stabilizes signaling via scheduling-based OTFS modulation. Our evaluation with operational high-speed rail datasets shows that, REM reduces failures comparable to static and low mobility, with low signaling and latency cost.

Resolving Policy Conflicts in Multi-Carrier Cellular Access MobiCom'18

Zengwen Yuan, Qianru Li, Yuanjie Li, Songwu Lu, Chunyi Peng, George Varghese
The 24th Annual International Conference on Mobile Computing and Networking (ACM MobiCom'18)

Multi-carrier access dynamically selects a preferred cellular carrier, by leveraging the availability and diversity of multiple carrier networks at a location. It offers an alternative solution to the dominant single-carrier practice, and shows early signs of success through the operational Project Fi by Google. In this paper, we study an important, yet largely unexplored problem of inter-carrier switch for multi-carrier access. We show that policy con icts may arise between the inter- and intra-carrier levels, resulting in oscillations among carriers in the worst case, akin to BGP looping. We derive the conditions under which such oscillations occur for three categories of popular policy, and validate them with Project Fi whenever possible. We provide practical guidelines that ensure loop-freedom and assess them via trace-driven emulations.

@inproceedings {yuan2018resolving, author = {Zengwen Yuan and Qianru Li and Yuanjie Li and Songwu Lu and Chunyi Peng and George Varghese}, title = {Resolving Policy Conflicts in Multi-Carrier Cellular Access}, booktitle = {The 24th ACM Annual International Conference on Mobile Computing and Networking (MobiCom'18)}, year = {2018}, month = Oct, address = {New Delhi, India}}

Supporting Mobile VR in LTE Networks: How Close Are We? SIGMETRICS'18

Zhaowei Tan, Yuanjie Li, Qianru Li, Zhehui Zhang, Zhehan Li, Songwu Lu
The 44th ACM Annual Conference of Special Interest Group on Measurement and Evaluation (SIGMETRICS'18)

Mobile virtual reality (VR) headsets (e.g., Google Cardboard and Samsung Gear VR) seek to offer “anytime, anywhere” panorama, immerse 3D experiences for users. In this work, we study the viability of supporting mobile VR over operational 4G LTE networks, where the device provides pose information to the edge servers to offload graphical processing. We find that, contrary to common perceptions, wireless bandwidth is not the latency bottleneck for medium-quality VR. Instead, the signaling operations, which facilitate wireless data delivery, constitute a bulk portion of the latency. We report findings that challenge five common beliefs on VR network latency in LTE under both static and mobile scenarios, and quantify their impact. We design LTE-VR, a client-side solution to medium-quality VR over LTE. LTE-VR leverages cross-layer design and rich side channel information to reduce various latency sources in the signaling operations. Our prototype evaluation has confirmed its viability in 4G LTE. We discuss its applicability to the upcoming 5G.

@inproceedings {tan2018vr, author = {Zhaowei Tan and Yuanjie Li and Qianru Li and Zhehui Zhang and Zhehan Li and Songwu Lu}, title = {Enabling Mobile VR in LTE Networks: How Close Are We?}, booktitle = {The 44th ACM Annual Conference of Special Interest Group on Measurement and Evaluation (SIGMETRICS'18)}, year = {2018}, month = Jun, address = {Irvine, California, USA}}


MobileInsight: In-phone mobile network analytics
My contribution:
  • Support control-plane monitoring (RRC/NAS) on MediaTek chipsets.
  • Build analyzers to extract performance metrics on data plane (PDCP/RLC/MAC/PHY).

    Software Engineering Intern @ Google, Seattle

    Jun 2019 - Sept 2019

    Design and evaluate approaches to mitigate latency for Google Stadia on Wi-Fi.

    Software Engineering Intern @ Uber, Palo Alto

    Jun 2018 - Sept 2018

    Develop network event collecting tools for Android. Analyze impact of LTE behavior on ride-sharing traffic.


    CS 118 Computer Network Fundamentals, 2020
    CS M51A Logic Design of Digital Systems, 2019
    CS 32 Introduction to Computer Science II, 2019
    CS 117 Computer Neworks: Physical Layer, 2018