Yuanjie Li
Associate Professor
FIT 1-217 Tsinghua University, Beijing, China 100084

yuanjiel [at] tsinghua.edu.cn

liyuanjie08 [at] gmail.com

CV, Google Scholar, Linkedin, GitHub, 中文

I am an associate professor at the Institute for Network Sciences and Cyberspace, Tsinghua University. Before joining Tsinghua, I was a researcher at Hewlett Packard Labs from 2018 to 2020, and the co-founder of MobIQ Technologies from 2017 to 2018. I received my Ph.D. in Computer Science at University of California, Los Angeles (UCLA) in June 2017 (advised by Prof. Songwu Lu) and B.E. in Electronic Engineering at Tsinghua University in 2012.

I am broadly interested in network systems and security, with an emphasis on satellite networking, wireless networking, intelligent mobile/edge computing, and Internet-of-Things (IoT). My research strives to make these systems smart and secure, by bridging the networking and security with data science, machine learning, formal verifications, economics, game theory, artificial intelligence, communication theory, distributed computing, and aerospace techniques.

I am always looking for self-motivated, creative and hard-working graduate and undergraduate students to work with. Please email me your CV if you are interested.

What's New

Apr 2024
MOSAIC receives the USENIX NSDI'24 Outstanding Paper Award!
Apr 2024
Invited to serve on NSDI'25 TPC. Please consider submitting!
Feb 2024
Our position paper on 6G and beyond network functions from space will appear at IEEE Internet Computing.
Dec 2023
Invited to serve on ICNP'24, and ICCCN'24 TPC. Please consider submitting!
Dec 2023
MOSAIC (Multi-Operator Satellite Access via In-band Control) accepted by NSDI'24.
Nov 2023
Stable hierarchical routing for operational satellite networks conditionally accepted by MobiCom'24.
Oct 2023
Security analysis of direct-to-cell satellite mega-constellations accepted by IEEE S&P'24.
Oct 2023
Invited to serve on SIGCOMM'24 TPC. Please consider submitting!
Sep 2023
Invited to serve on CoNEXT'24 TPC. Please consider submitting!
May 2023
Invited to serve on NSDI'24 TPC. Please consider submitting!
May 2023
Invited to serve on INFOCOM'24 TPC. Please consider submitting!
Jan 2023
Awarded ACM China Rising Star!
Nov 2022
A networking perspective on self-driving satellite mega-constellations accepted by MobiCom'23.
Nov 2022
Invited to serve on CoNEXT'23 TPC. Please consider submitting!
Sep 2022
Awarded ACM SIGCOMM China Rising Star!
July 2022
StarryNet, an experimentation framework for space network to appear in NSDI'23.
May 2022
SpaceCore, a stateless mobile core network in space to appear in SIGCOMM'22.
Feb 2022
Honored to be elevated to the grade of ACM Senior Member and IEEE Senior member.
Feb 2022
MobileInsight 6.0 has been released! Check its new features and code release!

More

Aug 2021
Cyber-Physical Convergence for the "Internet in space" to appear in HotNets'21.
Jul 2021
Strategic deterrence against intelligent DDoS to appear in CCS'21.
Jun 2021
I am invited to serve on MobiCom'22 TPC. Please consider submitting!
May 2021
Online learning for 5G mobility to appear in IWQoS'21.
Feb 2021
I am invited to serve as a TPC member for IEEE ICNP'21. Please consider submitting!
Dec 2020
Device-based mobile network latency reduction at application layer has been accepted by USENIX NSDI'21.
Nov 2020
The five-year retrospective of MobileInsight has been accepted by ACM MobiCom'21.
Sep 2020
MobileInsight 5.0 has been released! Check its new features and code release!
Jul 2020
I am invited to serve as a TPC member for ACM MobiCom'21.
May 2020
Beyond-5G reliable extreme mobility management (REM) will appear in ACM SIGCOMM'20.
May 2020
Measurements of 4G LTE on high-speed rails will appear in JSAC'20.
August 2019
I am invited to serve in the ACM MobiCom'20 TPC.
August 2019
MobileInsight 4.0 has been released! Check it out from our official website and GitHub repositories!
May 2019
Trusted, Latency-friendly Charging (TLC) for intelligent mobile edge will appear in ACM SIGCOMM'19.
October 2018
Measurement sutdy of 4G LTE on high-speed rails will appear in ACM MobiCom'19.
August 2018
iCellular will appear in IEEE/ACM Transactions on Networking (ToN).
May 2018
Resolving policy conflicts in multi-carrier cellular access has been accepted by ACM MobiCom'18.
May 2018
Awarded Cisco Outstanding Graduate Student Research Award in UCLA.
December 2017
Edge-powered mobile virtual reality (VR) has been accepted by ACM SIGMETRICS'18.
October 2017
Tick has won the MobiCom 2017 Best Community Paper Award.
August 2017
cniCloud has been accepted by WinTech'17.
June 2017
MobileInsight 3.0 has been released! See our new website and GitHub repositories!
June 2017
I have successfully defended my Ph.D. thesis. See my Ph.D. thesis online.
June 2017
Two papers to appear in ACM MobiCom'17: Reducing data access latency via control-plane acceleration (DPCM), and low-latency software-defined radio (Tick).
October 2016
MobileInsight has won the MobiCom 2016 Best Community Paper Award.
July 2016
4G-SMS security has been accepted by ACM CCS'16.
June 2016
MobileInsight has been accepted by ACM MobiCom'16.
April 2016
MobileInsight 2.0 has been released. Try our in-phone version of cellular network monitoring and analysis!
February 2016
Mobility misconfiguration analysis has been accepted by ACM SIGMETRICS'16.
August 2015
VoLTE security work has been accepted by ACM CCS'15.
April 2014
CNetVerifier has been accepted by ACM SIGCOMM'14.
December 2015
MMDiag and VoLTE* have been accepted by ACM HotMobile'16.
December 2015
iCellular has been accepted by USENIX NSDI'16.
November 2015
Femtocell work has been accepted by IEEE INFOCOM'16.
October 2015
Media coverage of our VoLTE work: TheVerge and RCRWireless News

Research

In my undergraduate research, I also worked on data center networking [ToN'13] and superconducting quantum computing [Physical Review A'13][JRB'13].

Honors/Awards

April 2024
USENIX NSDI Outstanding Paper Award
January 2023
ACM China Rising Star
Since 2022
ACM Senior Member
Since 2022
IEEE Senior Member
September 2022
ACM SIGCOMM China Rising Star
January 2019
NSF SBIR Phase I Award
April 2018
NSF I-Corps Award
May 2018
Cisco Outstanding Graduate Student Research Award in UCLA
October 2017
MobiCom’17 Best Community Paper Award
October 2016
MobiCom’16 Best Community Paper Award
July 2016
Outstanding Chinese Oversea Graduate Student Award
June 2016
UCLA Dissertation Year Fellowship
March 2015
Finalist Award for Qualcomm Innovation Fellowship (QINF)
December 2012
Best Student Research Training (SRT) Award, Tsinghua University
December 2011
Qianheng Huang Scholarship, Tsinghua University

Selected Publications

Please check my Google Scholar profile for the complete publication list.

(Note: Underline marks the students I supervised, "†" marks the co-primary authors, and "*" marks the corresponding authors.)

Democratizing Direct-to-Cell Low Earth Orbit Satellite Networks NSDI'24

Lixin Liu, Yuanjie Li*, Hewu Li*, Jiabo Yang, Wei Liu, Jingyi Lan, Yufeng Wang, Jiarui Li, Jianping Wu, Qian Wu, Jun Liu, Zeqi Lai
The 21st USENIX Symposium on Networked Systems Design and Implementation (NSDI'24)
Outstanding Paper Award

Multi-tenant Low Earth Orbit (LEO) satellites emerge as a cost-effective win-win solution for direct 4G/5G access to our regular phones/IoTs anywhere on Earth. However, the current hop-by-hop stateful cellular session impedes this effort due to its need for tight functional coupling and stable service relationships among satellite operators, mobile operators, and users. Our empirical study with real satellite data shows that, it restricts LEO satellites' serviceable areas, limits the use of available (possibly competitive) satellites, and suffers from signaling storms and dynamic many-to-many relationships in extreme LEO mobility. We thus devise MOSAIC to strive for self-serve multi-tenant LEO satellites. MOSAIC defines policy-embedded one-time tokens for pay-as-you-go local satellite access. These tokens allow satellites to self-serve users anywhere without relying on remote mobile operators, alleviate inter-satellite coordinations to enjoy competitive satellites, and simplify many-to-many service relationships for on-demand multi-tenancy. MOSAIC is attack-resilient and incrementally deployable using our SIM-based solution. Our evaluations with the real satellite data and commodity 3GPP NTN protocol stack validate MOSAIC's viability.

@inproceedings{nsdi24liu, title={Democratizing Direct-to-Cell Low Earth Orbit Satellite Networks}, author={Liu, Lixin and Li, Yuanjie and Li, Hewu and Yang, Jiabo and Liu, Wei and Lan, Jingyi and Wang, Yufeng and Li, Jiarui and Wu, Jianping and Wu, Qian and Liu, Jun and Lai, Zeqi}, booktitle={21st USENIX Symposium on Networked Systems Design and Implementation (NSDI'24)}, year={2024}, organization={USENIX} }

Stable Hierarchical Routing for Operational LEO Networks MobiCom'24

Yuanjie Li, Lixin Liu, Hewu Li, Wei Liu, Yimei Chen, Wei Zhao, Jianping Wu, Qian Wu, Jun Liu, Zeqi Lai
To appear at the 30th Annual International Conference On Mobile Computing And Networking (MobiCom'24)

Low Earth Orbit (LEO) satellite mega-constellations promise ubiquitous network services to “unconnected” users. But their upcoming global routing for Earth will be unstable due to exhaustive topology updates between satellites and Earth, inside an orbital shell, and across heterogeneous orbital shells. In real LEO networks, these multi-dimensional dynamics are interleaved and complicated by chaotic orbital maneuvers and random failures. They are less predictable than most satellite routing proposals expect and threaten these proposals’ availability, efficiency, or resiliency at scale.

We propose SHORT, a Stable Hierarchical Orbital Routing Technique to decouple, localize, and mask multi-dimensional dynamics from operational LEO networks. SHORT takes a geographic paradigm to organize the LEO network as stable hierarchical routing domains, split heterogeneous LEO dynamics into each domain, mask them with domain-specific routing via orbital-geodetic coordinates, and localize adaptions to orbital maneuvers, random failures, and partial deploy- ments. SHORT can work incrementally as a control-plane overlay to enhance existing LEO routing proposals. Our evaluations with the U.S. Space Surveillance Network datasets and prototype validate SHORT’s near-optimal availability, efficiency, and resiliency in operational LEO networks.

@inproceedings{mobicom24li, title={Stable Hierarchical Routing for Operational LEO Networks}, author={Li, Yuanjie and Liu, Lixin and Li, Hewu and Liu, Wei and Chen, Yimei and Zhao, Wei and Wu, Jianping and Wu, Qian and Liu, Jun and Lai, Zeqi}, booktitle={The 30th Annual International Conference On Mobile Computing And Networking (MobiCom'24)}, year={2024}, organization={ACM} }

The Dark Side of Scale: Insecurity of Direct-to-Cell Satellite Mega-Constellations S&P'24

Wei Liu, Yuanjie Li, Hewu Li, Yimei Chen, Yufeng Wang, Jingyi Lan, Jianping Wu, Qian Wu, Jun Liu, Zeqi Lai
To appear at the 45th IEEE Symposium on Security and Privacy (S&P'24)

The emergent direct-to-cell Low-Earth Orbit (LEO) satellite mega-constellations promise ubiquitous LTE/5G access for our commodity phones and IoTs without terrestrial base stations. While their extreme scale and mobility help tolerate diverse attacks, we show that both new features are exploitable to amplify signaling protocol vulnerabilities inherited from LTE/5G and obfuscate attacks to threaten satellite services. We showcase this with SatOver, a control-plane cross-layer attack that lets a greedy terrestrial operator or a man-in-the-middle attacker block all direct-to-cell satellites in urban areas. SatOver can reuse terrestrial LTE/5G base stations or deploy commodity software-defined radios as false satellites, stealthily hijack victim devices, delay their satellite access, stop them from probing other satellites, and block the entire mega-constellation. Our real-world satellite tests, lab tests with commodity 3GPP NR/IoT-NTN stacks, and operational trace-driven emulation validate SatOver’s viability for attacking COTS and upcoming NTN phones/IoTs. We discuss potential defenses against SatOver’s attack amplification/obfuscation.

@inproceedings{sp24liu, title={The Dark Side of Scale: Insecurity of Direct-to-Cell Satellite Mega-Constellations}, author={Liu, Wei and Li, Yuanjie and Li, Hewu and Chen, Yimei and Wang, Yufeng and Lan, Jingyi and Wu, Jianping and Wu, Qian and Liu, Jun and Lai, Zeqi}, booktitle={The 45th IEEE Symposium on Security and Privacy (S&P'24)}, year={2024}, organization={IEEE} }

Enabling 6G and Beyond Network Functions from Space: Challenges and Opportunities IEEE Internet Computing

Lixin Liu, Wei Liu, Yuanjie Li, Hewu Li
To appear at IEEE Internet Computing, 2024

Cellular networks from space, powered by recent technological advances in satellite mega-constellations, promise to expand operators’ service areas to anywhere on Earth for commercial revenues and social goods. While existing 5G has attempted to support satellites via its non-terrestrial network (NTN) enhancements, its hop-by-hop stateful session-based network architecture impedes this progress due to various functionality, scalability, reliability, and security concerns under the mega-constellation’s extreme mobility in the harsh outer space. This article investigates these issues and explores how to remove this architectural barrier for 6G and beyond from space. We propose a user-centric design that shifts from the hop-by-hop session-based to stateless on-demand cellular service. We discuss how this paradigm shift can stabilize the cellular function inter-networking under extreme satellite mobility, refactor in-orbit cellular functions to be stateless with local user equipment’s assistance, and foster efficient use of satellites for low capital costs and large-scale deployments.

@article{liu2024enabling, title={{Enabling 6G and Beyond Network Functions from Space: Challenges and Opportunities}}, author={Liu, Lixin and Liu, Wei and Li, Yuanjie and Li, Hewu}, journal={{IEEE Internet Computing}}, year={2024}, publisher={IEEE} }

SatGuard: Concealing Endless and Bursty Packet Losses in LEO Satellite Networks for Delay-Sensitive Web Applications WWW'24

Jihao Li, Hewu Li, Zeqi Lai, Qian Wu, Yijie Liu, Qi Zhang, Jun Liu, Yuanjie Li
To appear at the ACM Web Conference (WWW'24)

Delay-sensitive Web services are crucial applications in emerging low-earth orbit (LEO) satellite networks (LSNs). However, our realworld measurement study based on SpaceX’s Starlink, the most widely used commercial LSN today reveals that the endless and bursty packet losses over unstable LEO satellite links impose significant challenges on guaranteeing the quality of experience (QoE) of Web applications. We propose SatGuard, a distributed in-orbit loss recovery mechanism that can reduce user-perceived delay by completely concealing packet losses in the unstable and lossy LSN environment from endpoints. Specifically, SatGuard adopts a series of techniques to: (i) correctly migrate on-board packet buffer to support link local retransmission under LEO dynamics; (ii) efficiently detect packet losses on satellite links; and (iii) ensure packets ordering for endpoints. We implement a SatGuard prototype, and conduct extensive trace-driven evaluations guided by public constellation information and real-world measurements. Our experiments demonstrate that, in comparison with other state-of-the-art approaches, SatGuard can significantly improve Web-based QoE, by reducing: (i) up to 48.3% of page load time for Web browsing; and (ii) up to 57.4% end-to-end communication delay for WebRTC.

@inproceedings{www24li, title={SatGuard: Concealing Endless and Bursty Packet Losses in LEO Satellite Networks for Delay-Sensitive Web Applications}, author={Li, Jihao and Li, Hewu and Lai, Zeqi and Wu, Qian and Liu, Yijie and Zhang, Qi and Liu, Jun and Li, Yuanjie} booktitle={ACM TheWebConf 2024 Conference (WWW'24)}, year={2024}, organization={ACM} }

SKYCASTLE: Taming LEO Mobility to Facilitate Seamless and Low-latency Satellite Internet Services INFOCOM'24

Jihao Li, Hewu Li, Zeqi Lai, Qian Wu, Weisen Liu, Xiaomo Wang, Yuanjie Li, Jun Liu, Qi Zhang
To appear at IEEE International Conference on Computer Communications (INFOCOM'24)

Recent satellite constellations deployed in low earth orbit (LEO) are extending the boundary of today’s Internet, constructing integrated space and terrestrial networks (ISTNs) to provide Internet services pervasively, not only for residential users, but also for mobile users such as airplanes. Efficiently managing global mobility and keeping connections active is critical for operators. However, our quantitative analysis identifies that existing mobility management (MM) schemes inherently suffer from frequent connection interruptions and long latency. The fundamental challenge stems from a unique characteristic of ISTNs: not only users are mobile, but also core network infrastructures (i.e., LEO satellites) are frequently changing locations in networks.

To facilitate seamless and low-latency Internet services, this paper presents SKYCASTLE, a novel network-based global mobility management mechanism. SKYCASTLE incorporates two key techniques to address connection interruptions caused by space-ground handovers. First, to reduce connection interruptions, SKYCASTLE adopts distributed satellite anchors to track the location changes of mobile nodes, manage handovers and accelerate routing convergence. Second, SKYCASTLE leverages an anchor manager to schedule MM functionalities at satellites to reduce deployment costs while guaranteeing low latency. Extensive evaluations combining real constellation information and popular flight trajectories demonstrate that: SKYCASTLE can improve uninterrupted time by up to 55.8% and reduce latency by 47.8%.

@inproceedings{infocom24lai, title={SKYCASTLE: Taming LEO Mobility to Facilitate Seamless and Low-latency Satellite Internet Services}, author={Li, Jihao and Li, Hewu and Lai, Zeqi and Wu, Qian and Liu, Weisen and Wang, Xiaomo and Li, Yuanjie and Liu, Jun and Zhang, Qi} booktitle={ IEEE International Conference on Computer Communications (INFOCOM'24)}, year={2024}, organization={IEEE} }

In-Orbit Processing or Not? Sunlight-Aware Task Scheduling for Energy-Efficient Space Edge Computing Networks INFOCOM'24

Weisen Liu, Zeqi Lai, Qian Wu, Hewu Li, Qi Zhang, Zonglun Li, Yuanjie Li, Jun Liu
To appear at IEEE International Conference on Computer Communications (INFOCOM'24)

With the rapid evolution of space-borne capabilities, space edge computing (SEC) is becoming a new computation paradigm for future integrated space and terrestrial networks. Satellite edges adopt advanced on-board hardware, which not only enables new opportunities to perform complex intelligent space tasks, but also involves new challenges due to additional energy consumption in power-constrained space environment.

In this paper, we present PHOENIX, an energy-efficient task scheduling framework for futuristic SEC networks. PHOENIX exploits a key insight that in a SEC network, there exist a number of sunlit edges which are illuminated during their orbital period and have sufficient energy supplement from the sun. PHOENIX accomplishes energy-efficient in-orbit computing by judiciously offloading space tasks to “sunlight-sufficient” edges or to the ground. Specifically, PHOENIX first formulates the SEC battery energy optimizing (SBEO) problem to minimize average battery energy consumption while satisfying various task completion constraints. Then PHOENIX incorporates a sunlight- aware SEC task scheduling mechanism to make scheduling decisions effectively and efficiently. We implement a prototype and build a hardware-in-the-loop SEC experimental environment. Extensive data-driven evaluations demonstrate that as compared to other state-of-the-art solutions, PHOENIX can effectively reduce up to 28.4% battery energy consumption and prolong battery lifetime to 1.7× while still completing tasks on time.

@inproceedings{infocom24liu, title={In-Orbit Processing or Not? Sunlight-Aware Task Scheduling for Energy-Efficient Space Edge Computing Networks}, author={Liu, Weisen and Lai, Zeqi and Wu, Qian and Li, Hewu and Zhang, Qi and Li, Zonglun and Li, Yuanjie and Liu, Jun}, booktitle={ IEEE International Conference on Computer Communications (INFOCOM'24)}, year={2024}, organization={IEEE} }

Your Mega-Constellations Can be Slim: A Cost-Effective Approach for Constructing Survivable and Performant LEO Satellite Networks INFOCOM'24

Zeqi Lai, Yibo Wang, Hewu Li, Qian Wu, Qi Zhang, Yunan Hou, Jun Liu, Yuanjie Li
To appear at IEEE International Conference on Computer Communications (INFOCOM'24)

Recently we have witnessed the active deployment of satellite mega-constellations with hundreds to thousands of low-earth orbit (LEO) satellites, constructing emerging LEO satellite networks (LSN) to provide ubiquitous Internet services globally. However, while the massive deployment of mega-constellations can improve the network survivability and performance of an LSN, it also involves additional sustainable challenges such as higher deployment cost, risk of satellite conjunction and debris.

In this paper, we investigate an important research problem facing the upcoming satellite Internet: from a network perspective, how many satellites exactly do we need to construct a survivable and performant LSN? To answer this question, we first formulate the survivable and performant LSN design (SPLD) problem, which aims to find the minimum number of needed satellites to construct an LSN that can provide sufficient amount of redundant paths, link capacity and acceptable latency for all communication pairs served by the LSN. Second, to efficiently solve the tricky SPLD problem, we propose MEGAREDUCE, a requirement-driven constellation optimization mechanism, which can calculate feasible solutions for SPLD in polynomial time. Finally, we conduct extensive trace-driven simulations to verify MEGAREDUCE’s cost-effectiveness in constructing survivable and performant LSNs on demand, and showcase how MEGAREDUCE can help optimize the incremental deployment and long-term maintenance of future satellite Internet.

@inproceedings{infocom24lai, title={Your Mega-Constellations Can be Slim: A Cost-Effective Approach for Constructing Survivable and Performant LEO Satellite Networks}, author={Lai, Zeqi and Wang, Yibo and Li, Hewu and Zhang, Qi and Hou, Yunan and Liu, Jun and Li, Yuanjie}, booktitle={ IEEE International Conference on Computer Communications (INFOCOM'24)}, year={2024}, organization={IEEE} }

A Networking Perspective on Starlink's Self-Driving LEO Mega-Constellation MobiCom'23

Yuanjie Li, Hewu Li, Wei Liu, Lixin Liu, Wei Zhao, Yimei Chen, Jianping Wu, Qian Wu, Jun Liu, Zeqi Lai, Han Qiu
ACM International Conference on Mobile Computing and Networking (MobiCom'23)

Low-earth-orbit (LEO) satellite mega-constellations, such as SpaceX Starlink, are under rocket-fast deployments and promise broadband Internet to remote areas that terrestrial networks cannot reach. For mission safety and sustainable uses of space, Starlink has adopted a proprietary onboard autonomous driving system for its extremely mobile LEO satellites. This paper demystifies and diagnoses its impacts on the LEO mega-constellation and satellite networks. We design a domain-specific method to characterize key components in Starlink’s autonomous driving from various public space situational awareness datasets, including continuous orbit maintenance, collision avoidance, and maneuvers between orbital shells. Our analysis shows that, these operations have mixed impacts on the stability and performance of the entire mega-constellation, inter-satellite links, topology, and upper-layer network functions. To this end, we investigate and empirically assess the potential of networking-autonomous driving co-designs for the upcoming satellite networks.

@inproceedings{mobicom23li, title={A Networking Perspective on Starlink's Self-Driving LEO Mega-Constellation}, author={Li, Yuanjie and Li, Hewu and Liu, Wei and Liu, Lixin and Zhao, Wei and Chen, Yimei and Wu, Jianping and Wu, Qian and Liu, Jun and Lai, Zeqi and Qiu, Han}, booktitle={The 29th International Conference on Mobile Computing and Networking (MobiCom'23)}, year={2023}, organization={ACM} }

A First Look at Networking-Aware LEO Maneuvers LEO-NET'23

Wei Zhao, Yuanjie Li, Hewu Li, Yimei Chen
The 1st ACM Workshop on LEO Networking and Communication (LEO-NET)

Low-earth-orbit (LEO) mega-constellations, such as Starlink, are rapidly growing and enabling global Internet access from space. These LEO satellites undergo maneuvers for mission safety. However, contrary to conventional wisdom, we have discovered that satellite maneuvers can disrupt multiple inter-satellite links, impact network topology, and cause routing path failures, even if these maneuvers only slightly change the orbits of satellites. This occurs because maneuvering satellites have varying speeds in relation to other satellites, leading to the accumulation of relative displacement over time. This displacement disturbs the inter-satellite connection relationship, ultimately affecting the satellite network. To address this issue, we explore the network-aware LEO maneuver to reduce the frequency of such an issue by eliminating unnecessary maneuvers and optimizing necessary maneuvers.

@inproceedings{leonet23zhao, title={A First Look at Networking-Aware LEO Maneuvers}, author={Zhao, Wei and Li, Yuanjie and Li, Hewu and Chen, Yimei}, booktitle={ACM Workshop on LEO Networking and Communication (LEO-NET)}, year={2023}, organization={ACM} }

LDRP: Device-Centric Latency Diagnostic and Reduction for Cellular Networks without Root IEEE TMC

Zhaowei Tan, Jinghao Zhao, Yuanjie Li, Yifei Xu, Yunqi Guo Songwu Lu
IEEE Transactions on Mobile Computing (TMC), 2023

We design and implement LDRP, a device-based, standard-compliant solution to latency diagnosis and reduction in mobile networks without root privilege. LDRP takes a data-driven approach and works with a variety of latency-sensitive applications. After identifying elements in LTE uplink latency, we design LDRP that can infer the critical parameter used in data transmission and infer them for diagnosis. In addition, LDRP designates small dummy messages, which precede uplink data transmissions, thus eliminating latency elements due to power-saving, scheduling, etc. It imposes proper timing control among dummy messages and data packets to handle various conflicts. We achieve the latency diagnosis and reduction without requiring root privilege and ensure the latency is no worse than the legacy LTE design. The design of LDRP is also applicable for 5G. The evaluation shows that, LDRP infers the latency with at most 4% error and reduces the median LTE uplink latency by a factor up to 7.4× (from 42 to 5ms) for four apps over 4 mobile carriers.

@inproceedings{tan2023ldrp, title={LDRP: Device-Centric Latency Diagnostic and Reduction for Cellular Networks without Root}, author={Tan, Zhaowei and Zhao, Jinghao and Li, Yuanjie and Xu, Yifei and Guo, Yunqi and Lu, Songwu}, booktitle={IEEE Transactions on Mobile Computing (TMC)}, year={2023} }

One-bit Flip is All You Need: When Bit-flip Attack Meets Model Training ICCV'23

Jianshuo Dong, Han Qiu, Yiming Li, Tianwei Zhang, Yuanjie Li, Zeqi Lai, Chao Zhang, Shu-Tao Xia
IEEE International Conference on Computer Vision (ICCV), 2023

Deep neural networks (DNNs) are widely deployed on real-world devices. Concerns regarding their security have gained great attention from researchers. Recently, a new weight modification attack called bit flip attack (BFA) was proposed, which exploits memory fault inject techniques such as row hammer to attack quantized models in the deployment stage. With only a few bit flips, the target model can be rendered useless as a random guesser or even be implanted with malicious functionalities. In this work, we seek to further reduce the number of bit flips. We propose a training-assisted bit flip attack, in which the adversary is involved in the training stage to build a high-risk model to release. This high-risk model, obtained coupled with a corresponding malicious model, behaves normally and can escape various detection methods. The results on benchmark datasets show that an adversary can easily convert this high-risk but normal model to a malicious one on victim’s side by flipping only one critical bit on average in the deployment stage. Moreover, our attack still poses a significant threat even when defenses are employed.

@inproceedings{dong2023one-bit, title={One-bit Flip is All You Need: When Bit-flip Attack Meets Model Training}, author={Dong, Jianshuo and Qiu, Han and Li, Yiming and Zhang, Tianwei and Li, Yuanjie and Lai, Zeqi and Zhang, Chao and Xia, Shu-Tao}, booktitle={IEEE International Conference on Computer Vision (ICCV)}, year={2023} }

Achieving Resilient and Performance-Guaranteed Routing in Space-Terrestrial Integrated Networks INFOCOM'23

Zeqi Lai, Hewu Li, Yikun Wang, Qian Wu, Yangtao Deng, Jun Liu, Yuanjie Li, Jianping Wu
IEEE International Conference on Computer Communications (INFOCOM'23)

Satellite routers in emerging space-terrestrial integrated networks (STINs) are operated in a failure-prone, intermittent and resource-constrained space environment, making it very critical but challenging to cope with various network failures effectively. Existing resilient routing approaches either suffer from continuous re-convergences with low network reachability or involve prohibitive pre-computation and storage overhead due to the huge amount of possible failure scenarios in STINs.

This paper presents STARCURE, a novel resilient routing mechanism for futuristic STINs. STARCURE aims at achieving fast and efficient routing restoration while maintaining the low-latency, high-bandwidth service capabilities in failure-prone space environments. First, STARCURE incorporates a new network model, called the topology-stabilizing model (TSM) to eliminate topological uncertainty by converting the topology variations caused by various failures to traffic variations. Second, STARCURE adopts an adaptive hybrid routing scheme, collaboratively combining a constraint optimizer to efficiently handle predictable failures, together with a location-guided protection routing strategy to quickly deal with unexpected failures. Extensive evaluations driven by realistic constellation information show that STARCURE can protect routing against various failures, achieving close-to-100% reachability and better performance restoration with acceptable system overhead, as compared to other existing resilience solutions.

@inproceedings{STARCURE-infocom23, title={Achieving Resilient and Performance-Guaranteed Routing in Space-Terrestrial Integrated Networks}, author={Lai, Zeqi and Li, Hewu and Wang, Yikun and Wu, Qian and Deng, Yangtao and Liu, Jun and Li, Yuanjie and Wu, Jianping}, booktitle={IEEE International Conference on Computer Communications (INFOCOM)}, year={2023}, organization={IEEE} }

FALCON: Towards Fast and Scalable Data Delivery for Emerging Earth Observation Constellations INFOCOM'23

Mingyang Lv, Qian Wu, Zeqi Lai, Hewu Li, Yuanjie Li, Jun Liu
IEEE International Conference on Computer Communications (INFOCOM'23)

Exploiting a constellation of small satellites to realize continuous earth observations (EO) is gaining popularity. Large-volume EO data acquired from space needs to be transferred to the ground. However, existing EO delivery approaches are either: (a) efficiency-limited, suffering from long delivery completion time due to the intermittent ground-space communication, or (b) scalability-limited since they fail to support concurrent delivery for multiple satellites in an EO constellation. To make big data delivery for emerging EO constellations fast and scalable, we propose FALCON, a multi-path EO delivery framework that wisely exploits diverse paths in broadband constellations to collaboratively deliver EO data effectively. Specifically, we formulate the constellation-wide EO data multipath download (CEOMP) problem, which aims at minimizing the delivery completion time of requested data for all EO sources. We prove the hardness of solving CEOMP, and further present a heuristic multipath routing and bandwidth allocation mechanism to tackle the technical challenges caused by time-varying satellite dynamics and flow contention, and solve the CEOMP problem efficiently. Evaluation results based on public orbital data of real EO constellations show that as compared to other state-of-the-art approaches, FALCON can reduce at least 51% delivery completion time for various data requests in large EO constellations.

@inproceedings{FALCON-infocom23, title={FALCON: Towards Fast and Scalable Data Delivery for Emerging Earth Observation Constellations}, author={Lv, Mingyang and Wu, Qian and Lai, Zeqi and Li, Hewu and Li, Yuanjie and Liu, Jun}, booktitle={IEEE International Conference on Computer Communications (INFOCOM)}, year={2023}, organization={IEEE} }

StarryNet: Empowering Researchers to Evaluate Futuristic Integrated Space and Terrestrial Networks NSDI'23

Zeqi Lai, Hewu Li, Yangtao Deng, Qian Wu, Jun Liu, Yuanjie Li, Jihao Li, Lixin Liu, Weisen Liu, Jianping Wu
USENIX Symposium on Networked Systems Design and Implementation (NSDI'23)

Futuristic integrated space and terrestrial networks (ISTN) not only hold new opportunities for pervasive, low-latency Internet services, but also face new challenges caused by satellite dynamics on a global scale. It should be useful for researchers to run various experiments to systematically explore new problems in ISTNs. However, existing experimentation methods either attain realism but lack flexibility (e.g., live satellites), or achieve flexibility but lack realism (e.g., ISTN simulators).

This paper presents STARRYNET, a novel experimentation framework that enables researchers to conveniently build credible and flexible experimental network environments (ENE) mimicking satellite dynamics and network behaviors of large-scale ISTNs. STARRYNET simultaneously achieves constellation-consistency, networked system realism and flexibility, by adopting a real-data-driven, lightweight-emulationaided approach to build a digital twin of physical ISTNs in the terrestrial virtual environment. Driven by public and real constellation-relevant information, we show STARRYNET’s acceptable fidelity and demonstrate its flexibility to support various ISTN experiments, such as evaluating different internetworking mechanisms for space-ground integration, and assessing the network resilience of futuristic ISTNs.

@inproceedings{StarryNet, title={StarryNet: Empowering Researchers to Evaluate Futuristic Integrated Space and Terrestrial Networks}, author={Lai, Zeqi and Li, Hewu and Deng, Yangtao and Wu, Qian and Liu, Jun and Li, Yuanjie and Li, Jihao and Liu, Lixin and Liu, Weisen and Wu, Jianping}, booktitle={USENIX Symposium on Networked Systems Design and Implementation (NSDI)}, year={2023}, organization={USENIX} }

Movement-Based Reliable Mobility Management for Beyond 5G Cellular Networks IEEE/ACM ToN

Zhehui Zhang, Yuanjie Li*, Qianru Li, Jinghao Zhao, Ghufran Baig, Lili Qiu, Songwu Lu
IEEE/ACM Transactions on Networking (ToN), 2022

Extreme mobility becomes a norm rather than an exception with emergent high-speed rails, drones, industrial IoT, and many more. 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 qualitysignal 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, Reliable Extreme Mobility management for beyond 5G cellular networks while maintaining backward compatibility to 4G/5G. shifts to movement-based mobility management in the delay-Doppler domain. Its signaling overlay relaxes feedback via cross-band 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, reduces failures comparable to static and low mobility, with low signaling and latency cost. reduces the network failures by up to an order of magnitude, eliminates policy conflicts, and improves application performance by 31.8%-88.3% compared to legacy 4G/5G.

@inproceedings{zhang2022movement, title={Movement-Based Reliable Mobility Management for Beyond 5G Cellular Networks}, author={Zhang, Zhehui and Li, Yuanjie and Li, Qianru and Zhao, Jinghao and Baig, Ghufran and Qiu, Lili and Lu, Songwu}, booktitle={IEEE/ACM Transactions on Networking (TON)}, year={2022}, }

Extracting and Predicting Multipath Profiles under High Mobility and Its Application MobiHoc'22

Ghufran Baig, Changhan Ge, Lili Qiu, Yuanjie Li, Wangyang Li, Jian He, Zhehui Zhang, Songwu Lu
International Symposium on Theory, Algorithmic Foundations, and Protocol Design for Mobile Networks and Mobile Computing (MobiHoc'22)

The wireless signal propagates via multipath arising from different reflections and penetration between a transmitter and receiver. Extracting multipath profiles (e.g., delay and Doppler along each path) from received signals enables many important applications, such as channel prediction and crossband channel estimation (i.e., estimating the channel on a different frequency). The benefit of multipath estimation further increases with mobility since the channel in that case is less stable and more important to track. Yet high-speed mobility poses significant challenges to multipath estimation. In this paper, instead of using time-frequency domain channel representation, we leverage the delay-Doppler domain representation to accurately extract and predict multipath properties. Specifically, we use impulses in the delay-Doppler domain as pilots to estimate the multipath parameters and apply the multipath information to predicting wireless channels as an example application. Our design rationale is that mobility is more predictable than the wireless channel since mobility has inertial while the wireless channel is the outcome of a complicated interaction between mobility, multipath, and noise. We evaluate our approach via both acoustic and RF experiments, including vehicular experiments using USRP. Our results show that the estimated multipath matches the ground truth, and the resulting channel prediction is more accurate than the traditional channel prediction schemes.

@inproceedings{baig22extracting, title={Extracting and Predicting Multipath Profiles under High Mobility and Its Application}, author={Baig, Ghufran and Ge, Changhan and Qiu, Lili and Li, Yuanjie and Li, Wangyang and He, Jian and Zhang, Zhehui and Lu, Songwu}, booktitle={the 23rd International Symposium on Theory, Algorithmic Foundations, and Protocol Design for Mobile Networks and Mobile Computing (MobiHoc)}, year={2022}, organization={ACM} }

A Case for Stateless Mobile Core Network Functions in Space SIGCOMM'22

Yuanjie Li, Hewu Li, Wei Liu, Lixin Liu, Yimei Chen, Jianping Wu, Qian Wu, Jun Liu, Zeqi Lai
Annual conference of the ACM Special Interest Group on Data Communication (ACM SIGCOMM'22)

Is it worth and feasible to push mobile core network functions to low-earth-orbit (LEO) satellite mega-constellations? While this paradigm is being tested in space and promises new values, it also raises scalability, performance, and security concerns based on our study with signaling datasets from operational satellites and 5G. A major challenge is today’s stateful mobile core, which suffers from signaling storms in satellites’ extreme mobility, intermittent failures in outer space, and attacks when unavoidably exposed to untrusted foreign locations. To this end, we make a case for a stateless mobile core in space. Our solution, SpaceCore, decouples states from orbital core functions, simplifies location states via geospatial addressing, eliminates unnecessary state migrations in satellite mobility by shifting to geospatial service areas, and localizes state retrievals with device-as-the-repository. Our evaluation with datasets from operational satellites and 5G shows SpaceCore’s 17.5× signaling reductions and resiliency to failures/attacks compared to existing solutions.

@inproceedings{li2022spacecore, title={A Case for Stateless Mobile Core Network Functions in Space}, author={Li, Yuanjie and Li, Hewu and Liu, Wei and Liu, Lixin and Chen, Yimei and Wu, Jianping and Wu, Qian and Liu, Jun and Lai, Zeqi}, booktitle={Proceedings of the ACM Special Interest Group on Data Communication (SIGCOMM)}, year={2022}, organization={ACM} }

An In-Depth Study of Uplink Performance of 5G mmWave Networks SIGCOMM 5G-MeMU'22

Moinak Ghoshal, Z. Jonny Kong, Qiang Xu, Zixao Lu, Shivang Aggarwal, Imran Khan, Yuanjie Li, Y. Charlie Hu, Dimitrios Koutsoniklas
Proceedings of 2nd ACM SIGCOMM Workshop on 5G and Beyond Network Measurements, Modeling, and Use Cases (5G-MeMU), 2022

The highly anticipated 5G mmWave technology promises to enable many uplink-oriented, latency-critical applications (LCAs) such as Augmented Reality and Connected Autonomous Vehicles. Nonetheless, recent measurement studies have largely focused on its downlink performance. In this work, we perform a systematic study of the uplink performance of commercial 5G mmWave networks across 3 major US cities and 2 mobile operators. Our study makes three contributions. (1) It reveals that 5G mmWave uplink performance is geo-graphically diverse, substantially higher over LTE in terms of bandwidth and latency, but often erratic and suboptimal, which can degrade LCA performance. (2) Our analysis of control messages and PHY-level KPIs shows that the root causes for the suboptimal performance are fundamental to 5G mmWave and cannot be easily fixed via simple tuning of network configurations. (3) We identify various design and deployment optimizations that 5G operators can explore to bring 5G mmWave performance to the level needed to ultimately support the LCAs.

@inproceedings{Ghoshal2022in-depth, title={An In-Depth Study of Uplink Performance of 5G mmWave Networks}, author={Moinak Ghoshal and Z. Jonny Kong and Qiang Xu and Zixao Lu and Shivang Aggarwal and Imran Khan and Yuanjie Li and Y. Charlie Hu and Dimitrios Koutsoniklas}, booktitle={Proceedings of 2nd ACM SIGCOMM Workshop on 5G and Beyond Network Measurements, Modeling, and Use Cases (5G-MeMU)}, year={2022}, organization={ACM} }

Interpreting AI for Networking: Where We Are and Where We Are Going IEEE Communications Magazine

Tianzhu Zhang, Han Qiu, Marco Mellia, Yuanjie Li, Hewu Li, Ke Xu
IEEE Communications Magazine, 60(2), pp.25-31, 2022

In recent years, Artificial Intelligence (AI) techniques have been increasingly adopted to tackle networking problems. Although AI algorithms can deliver high-quality solutions, most of them are inherently intricate and erratic for human cognition. This lack of interpretability tremendously hinders the commercial success of AI-based solutions in practice. To cope with this challenge, networking researchers explore eXplainable AI (XAI) techniques to make AI models interpretable, manageable, and trustworthy. In this paper, we overview the application of AI in networking and discuss the necessity for interpretability. Next, we review the current research on interpreting AI-based networking solutions and systems. At last, we envision future challenges and directions. The ultimate goal of this paper is to present a general guideline for AI and networking practitioners and motivate the continuous advancement of AI-based solutions in modern communication networks.

@inproceedings{tianzhu2022interpreting, title={Interpreting AI for Networking: Where We Are and Where We Go}, author={Tianzhu Zhang and Han Qiu and Marco Mellia and Yuanjie Li and Hewu Li and Ke Xu}, booktitle={IEEE Communication Magazine}, year={2022} }

Can 5G mmWave Support Multi-User AR? PAM'22

Moinak Ghoshal, Pranab Dash, Zhaoning Kong, Qiang Xu, Y. Charlie Hu, Dimitrios Koutsonikolas, Yuanjie Li
Passive and Active Measurement Conference 2022 (PAM'22)

Augmented Reality (AR) has been widely hailed as a representative of ultra-high bandwidth and ultra-low latency apps that will be enabled by 5G networks. While single-user AR can perform AR tasks locally on the mobile device, multi-user AR apps, which allow multiple users to interact within the same physical space, critically rely on the cellular network to support user interactions. However, a recent study showed that multi-user AR apps can experience very high end-to-end latency when running over LTE, rendering user interaction practically infeasible. In this paper, we study whether 5G mmWave, which promises significant bandwidth and latency improvements over LTE, can support multi-user AR by conducting an in-depth measurement study of the same popular multi-user AR app over both LTE and 5G mmWave.

Our measurement and analysis show that: (1) The E2E AR latency over LTE is significantly lower compared to the values reported in the previous study. However, it still remains too high for practical user interaction. (2) 5G mmWave brings no benefits to multi-user AR apps. (3) While 5G mmWave reduces the latency of the uplink visual data transmission, there are other components of the AR app that are independent of the network technology and account for a significant fraction of the E2E latency. (4) The app drains 66% more network energy, which translates to 28% higher total energy over 5G mmWave compared to over LTE.

@inproceedings{moinak2022can, title={Can 5G mmWave support Multi-User AR?}, author={Moinak Ghoshal and Pranab Dash and Zhaoning Kong and Qiang Xu and Y. Charlie Hu and Dimitrios Koutsonikolas and Yuanjie Li}, booktitle={Passive and Active Measurement Conference 2022 (PAM'22)}, year={2022} }

“Internet in Space” for Terrestrial Users via Cyber-Physical Convergence HotNets'21

Yuanjie Li, Hewu Li, Lixin Liu, Wei Liu, Jiayi Liu, Jianping Wu, Qian Wu, Jun Liu, Zeqi Lai
Twentieth ACM Workshop on Hot Topics in Networks (ACM HotNets'21)

We study a new design objective for “Internet in space” for terrestrial users: To align logical network topology, address, and route in the virtual cyberspace with movements of satellite mega-constellations and earth’s rotations in the real physical world. We explain why this is particularly desirable by the recent low-earth-orbit (LEO) mega-constellations, and how it welcomes mobility to streamline the network design for stability, efficiency, and scalability in an unstable space-ground environment. We showcase its feasibility with the common fixed satellite sub-point trajectory in mega-constellations. We describe how it permits stable recursive topology, unifies cyber-physical locations in the address, and naturally embeds the geographical routing into the topological routing.

@inproceedings{li2021cyber, title={“Internet in Space” for Terrestrial Users via Cyber-Physical Convergence}, author={Li, Yuanjie and Li, Hewu and Liu, Lixin and Liu, Wei and Liu, Jiayi and Wu, Jianping and Wu, Qian and Liu, Jun and Lai, Zeqi}, booktitle={Twentieth ACM Workshop on Hot Topics in Networks (HotNets)}, year={2021}, organization={ACM} }

Deterrence of Intelligent DDoS via Multi-Hop Traffic Divergence CCS'21

Yuanjie Li, Hewu Li, Zhizheng Lv, Xingkun Yao, Qianru Li, Jianping Wu
Proceedings of the 2021 ACM SIGSAC Conference on Computer and Communications Security (ACM CCS'21)

We devise a simple, provably effective, and readily usable deterrence against intelligent, unknown DDoS threats: Demotivate adversaries to launch attacks via multi-hop traffic divergence. This new strategy is motivated by the fact that existing defenses almost always lag behind numerous emerging DDoS threats and evolving intelligent attack strategies. The root cause is if adversaries are smart and adaptive, no single-hop defenses (including optimal ones) can perfectly differentiate unknown DDoS and legitimate traffic. Instead, we formulate intelligent DDoS as a game between attackers and defenders, and prove how multi-hop traffic divergence helps bypass this dilemma by reversing the asymmetry between attackers and defenders. This insight results in EID, an Economical Intelligent DDoS Demotivation protocol. EID combines local weak (yet divergent) filters to provably null attack gains without knowing exploited vulnerabilities or attack strategies. It incentivizes multi-hop defenders to cooperate with boosted local service availability. EID is resilient to traffic dynamics and manipulations. It is readily deployable with random-drop filters in real networks today. Our experiments over a 49.8 TB dataset from a department at the Tsinghua campus network validate EID’s viability against rational and irrational DDoS with negligible costs.

@inproceedings{li2021eid, title={Deterrence of Intelligent DDoS via Multi-Hop Traffic Divergence}, author={Li, Yuanjie and Li, Hewu and Lv, Zhizheng and Yao, Xingkun and Li, Qianru and Wu, Jianping}, booktitle={Proceedings of the 2021 ACM SIGSAC Conference on Computer and Communications Security (CCS)}, year={2021}, organization={ACM} }

Experience: A Five-Year Retrospective of MobileInsight MobiCom'21

Yuanjie Li, Chunyi Peng, Zhehui Zhang, Zhaowei Tan, Haotian Deng, Jinghao Zhao, Qianru Li, Yunqi Guo, Kai Ling, Boyan Ding, Hewu Li, Songwu Lu
The 27th Annual International Conference On Mobile Computing And Networking (ACM MobiCom'21)

This paper reports our five-year lessons of developing and using MobileInsight, an open-source community tool to enable software-defined full-stack, runtime mobile network analytics inside our phones. We present how MobileInsight evolves from a simple monitor to a community toolset with cross-layer analytics, energy-efficient real-time user-plane analytics, and extensible user-friendly analytics at the control and user planes. These features are enabled by various novel techniques, including cross-layer state machine tracking, missing data inference, and domain-specific cross-layer sampling. Their powerfulness is exemplified with a 5-year longitudinal study of operational mobile network latency using a 6.4TB dataset with 6.1 billion over-the-air messages. We further share lessons and insights of using MobileInsight by the community, as well as our visions of MobileInsight’s past, present, and future.

@inproceedings{li2021mobileinsight, title={Experience: A Five-Year Retrospective of MobileInsight}, author={Li, Yuanjie and Peng, Chunyi and Zhang, Zhehui and Tan, Zhaowei and Deng, Haotian and Zhao, Jinghao and Li, Qianru and Guo, Yunqi and Ling, Kai and Ding, Boyan and Li, Hewu and Lu, Songwu}, booktitle={Annual International Conference On Mobile Computing And Networking (MobiCom)}, year={2021}, organization={ACM} }

Device-Based LTE Latency Reduction at the Application Layer NSDI'21

Zhaowei Tan, Jinghao Zhao, Yuanjie Li, Yifei Xu, Songwu Lu
18th USENIX Symposium on Networked Systems Design and Implementation (NSDI'21)

We design and implement LRP, a device-based, standard-compliant solution to latency reduction in mobile networks. LRP takes a data-driven approach. It works with a variety of latency-sensitive mobile applications without requiring root privilege, and ensures the latency is no worse than the legacy LTE design. Using traces from operational networks, we identify all elements in LTE uplink latency and quantify them. LRP designates small dummy messages, which precede uplink data transmissions, thus eliminating latency elements due to power-saving, scheduling, etc. It imposes proper timing control among dummy messages and data packets to handle various conflicts. The evaluation shows that, LRP reduces the median LTE uplink latency by a factor up to 7.4× (from 42ms to 5ms) for four tested apps over five mobile carriers.

@inproceedings{tan2021device, title={Device-Based LTE Latency Reduction at the Application Layer}, author={Tan, Zhaowei and Zhao, Jinghao and Li, Yuanjie and Xu, Yifei and Lu, Songwu}, booktitle={18th USENIX Symposium on Networked Systems Design and Implementation (NSDI)}, year={2021}, organization={USENIX} }

Can Online Learning Increase the Reliability of Extreme Mobility Management? IWQoS'21

Yuanjie Li, Esha Datta, Jiaxin Ding, Ness B Shroff, Xin Liu
IEEE/ACM International Symposium on Quality of Service (IEEE/ACM IWQoS'21)

Seamless Internet access under extreme user mobility is highly demanded on high-speed trains and vehicles.However, existing mobile networks (e.g., 4G LTE and 5G NR) cannot reliably satisfy this demand, with a 5.5%–12.6% handover failure ratio at 200–350 km/h. A root cause is that, the 4G/5G handovers have to balance the exploration of more measurements for satisfactory handover and the exploitation for timely handover before the fast-moving user leaves the coverage.

We design BaTT, an online learning solution for reliable handovers in extreme mobility. BaTT decomposes the explorationexploitation tradeoff into two multi-armed bandit problems. It uses ε-binary-search to optimize the threshold of a serving cell’s signal strength to initiate the handover with O(log J log T) regrets. It further adopts opportunistic Thompson sampling to optimize the sequence of target cells measured for reliable handovers. BaTT can be implemented using the recent Open Radio Access Network (O-RAN) framework in operational 4G LTE and 5G NR. Our evaluations over a dataset from operational LTE networks on the Chinese high-speed rails show a 29.1% handover failure reduction at the speed of 200-350 km/h.

@inproceedings{li2021online, title={Can Online Learning Increase the Reliability of Extreme Mobility Management?}, author={Li, Yuanjie and Datta, Esha and Ding, Jiaxin and Shroff, Ness and Liu, Xin}, booktitle={IEEE/ACM International Symposium on Quality of Service (IWQoS'21)}, year={2021}, organization={IEEE/ACM} }

Beyond 5G: Reliable Extreme Mobility Management SIGCOMM'20

Yuanjie Li, Qianru Li, Zhehui Zhang, Ghufran Baig, Lili Qiu, Songwu Lu
Annual conference of the ACM Special Interest Group on Data Communication (ACM SIGCOMM'20)

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 delay-Doppler domain. Its signaling overlay relaxes feedback via cross-band 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.

@inproceedings{li2020beyond, title={Beyond 5G: Reliable Extreme Mobility Management}, author={Li, Yuanjie and Li, Qianru and Zhang, Zhehui and Baig, Ghufran and Qiu, Lili and Lu, Songwu}, booktitle={Proceedings of the ACM Special Interest Group on Data Communication (SIGCOMM)}, pages={344--358}, year={2020}, organization={ACM} }

A First Look at Disconnection-centric TCP Performance on High-speed Railways JSAC'20

Chenren Xu, Jing Wang, Zhiyao Ma, Yihua Cheng, Yunzhe Ni, Wangyang Li, Feng Qian, Yuanjie Li
IEEE Journal on Selected Areas in Communications, 2020

High-speed rail (HSR) systems potentially provide a more efficient way of door-to-door transportation than airplane. However, they also pose unprecedented challenges in delivering seamless Internet service for on-board passengers. In this paper, we conduct the first large-scale disconnection-centric measurement study of TCP performance over LTE on HSR. Our measurement targets the main HSR route in China operating at 300/350 km/h. We performed extensive data collection obtaining 378.3 GB data collected over 56639 km of trips. Leveraging such a unique dataset, we measure important performance metrics such as TCP goodput, latency and loss rate across different congestion control algorithm, mobile carrier, and different train speed. We further develop the LTE disconnection taxonomy, and conduct a in-depth correlation study between TCP stall and LTE disconnection. Our findings reveal the networking performance on today’s HSR environment “in the wild”, as well as identify several root causes of performance inefficiencies, which together highlight the need to develop dedicated protocol mechanisms that are friendly to extreme mobility.

@article{xu2020first, title={A First Look at Disconnection-centric TCP Performance on High-speed Railways}, author={Xu, Chenren and Wang, Jing and Ma, Zhiyao and Cheng, Yihua and Ni, Yunzhe and Li, Wangyang and Qian, Feng and Li, Yuanjie}, journal={IEEE Journal on Selected Areas in Communications}, year={2020}, publisher={IEEE} }

Bridging the Data Charging Gap in the Cellular Edge SIGCOMM'19

Yuanjie Li, Kyu-Han Kim, Christina Vlachou, Junqing Xie
Annual conference of the ACM Special Interest Group on Data Communication (ACM SIGCOMM'19)

The 4G/5G cellular edge promises low-latency experiences anywhere, anytime. However, data charging gaps can arise between the cellular operators and edge application vendors, and cause over-/under-billing. We find that such gap can come from data loss, selfish charging, or both. It can be amplified in the edge, due to its low-latency requirements. We devise TLC, a Trusted, Loss-tolerant Charging scheme for the cellular edge. At its core, TLC enables loss-selfishness cancellation to bridge the gap, and constructs publicly verifiable, cryptographic proof-of-charging for mutual trust. We implement TLC with commodity edge nodes, OpenEPC and small cells. Our experiments in various edge scenarios validate TLC's viability of reducing the gap with marginal latency and other overhead.

@inproceedings{li2019bridging, title={{Bridging the Data Charging Gap in the Cellular Edge}}, author={Li, Yuanjie and Kim, Kyu-Han and Vlachou, Christina and Xie, Junqing}, booktitle={Proceedings of the ACM Special Interest Group on Data Communication (SIGCOMM)}, pages={15--28}, year={2019}, organization={ACM} }

An Active-Passive Measurement Study of TCP Performance over LTE on High-speed Rails MobiCom'19

Jing Wang, Yufan Zheng, Yunzhe Ni, Chenren Xu, Feng Qian, Wangyang Li, Wantong Jiang, Yihua Cheng, Zhuo Cheng, Yuanjie Li, Xiufeng Xie, Yi Sun, Zhongfeng Wang
The 25th Annual International Conference on Mobile Computing and Networking (ACM MobiCom'19)

High-speed rail (HSR) systems potentially provide a more efficient way of door-to-door transportation than airplane. However, they also pose unprecedented challenges in delivering seamless Internet service for on-board passengers. In this paper, we conduct a large-scale active-passive measurement study of TCP performance over LTE on HSR. Our measurement targets the HSR routes in China operating at above 300 km/h. We performed extensive data collection through both controlled setting and passive monitoring, obtaining 1732.9 GB data collected over 135719 km of trips. Leveraging such a unique dataset, we measure important performance metrics such as TCP goodput, latency, loss rate, as well as key characteristics of TCP flows, application breakdown, and users' behaviors. We further quantitatively study the impact of frequent cellular handover on HSR networking performance, and conduct in-depth examination of the performance of two widely deployed transport-layer protocols: TCP CUBIC and TCP BBR. Our findings reveal the performance of today's commercial HSR networks "in the wild", as well as identify several performance inefficiencies, which motivate us to design a simple yet effective congestion control algorithm based on BBR to further boost the throughput by up to 36.5%. They together highlight the need to develop dedicated protocol mechanisms that are friendly to extreme mobility.

@inproceedings{wang2019active, title={An Active-Passive Measurement Study of TCP Performance over LTE on High-speed Rails}, author={Wang, Jing and Zheng, Yufan and Ni, Yunzhe and Xu, Chenren and Qian, Feng and Li, Wangyang and Jiang, Wantong and Cheng, Yihua and Cheng, Zhuo and Li, Yuanjie and others}, booktitle={The 25th Annual International Conference on Mobile Computing and Networking (MobiCom)}, pages={1--16}, year={2019}, organization={ACM} }

Device-Customized Multi-Carrier Network Access on Commodity Smartphones ToN'18

Yuanjie Li, Chunyi Peng, Haotian Deng, Zengwen Yuan, Guan-Hua Tu, Jiayao Li, Songwu Lu, Xi Li
IEEE/ACM Transactions on Networking (ToN), 2018

Accessing multiple carrier networks (T-Mobile, Sprint, AT&T, etc.) offers a promising paradigm for smartphones to boost its mobile network quality. However, the current practice does not achieve the full potential of this approach because it has not utilized fine-grained, cellular-specific domain knowledge. Our experiments and code analysis discover three implementation-independent issues: (1) it may not trigger the anticipated switch when the serving carrier network is poor; (2) the switch takes a much longer time than needed; and (3) the device fails to choose the high-quality network (e.g., selecting 3G rather than 4G). To address them, we propose iCellular, which exploits low-level cellular information at the device to improve multi-carrier access. iCellular is proactive and adaptive in its multi-carrier selection by leveraging existing end-device mechanisms and standards-complaint procedures. It performs adaptive monitoring to ensure responsive selection and minimal service disruption, and enhances carrier selection with online learning and runtime decision fault prevention. It is readily deployable on smartphones without infrastructure/hardware modifications. We implement iCellular on commodity phones and harness the efforts of Project Fi to assess multi-carrier access over two US carriers: T-Mobile and Sprint. Our evaluation shows that, iCellular boosts the devices’ throughput with up to 3.74× throughput improvement, 6.9× suspension reduction, and 1.9× latency decrement over the state-of-the-art, with moderate CPU, memory and energy overheads.

@inproceedings {li2018icellular, title = {Device-Customized Cellular Network Access on Commodity Smartphones}, author = {Yuanjie Li and Haotian Deng and Chunyi Peng and Zengwen Yuan and Guan-Hua Tu and Jiayao Li and Songwu Lu and Xi Li}, journal={IEEE/ACM Transactions on Networking (ToN)}, year = {2018}, publisher = {IEEE/ACM} }

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), acceptance rate: 54/270 = 20%

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}}

A Machine Learning Based Approach to Mobile Network Analysis ICCCN'18

Zengwen Yuan, Yuanjie Li, Chunyi Peng, Songwu Lu, Haotian Deng, Zhaowei Tan, Taqi Raza
The 27th International Conference on Computer Communications and Networks (ICCCN 2018), invited paper

In this paper, we present our recent work in progress on 4G mobile network analysis. In order to provide an in-depth study on the closed network operations, we advocate a novel approach via two-level, device-centric machine learning that can open up the system behaviors and facilitate fine-grained analysis . We describe our proposed approach, and use the latency analysis on two popular mobile apps (Web browsing and Instant Messaging) to illustrate how our scheme works. We further present preliminary results and discuss open issues.

@inproceedings {icccn18ml, author = {Zengwen Yuan and Yuanjie Li and Chunyi Peng and Songwu Lu and Haotian Deng and Zhaowei Tan and Taqi Raza}, title = {A Machine Learning Based Approach to Mobile Network Analysis}, booktitle = {The 27th International Conference on Computer Communications and Networks (ICCCN 2018)}, year = {2018}, month = Jul, address = {Hangzhou, China}}

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), acceptance rate: 42/187 = 22.2%

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}}

A Control-Plane Perspective on Reducing Data Access Latency in LTE Networks MobiCom'17

Yuanjie Li, Zengwen Yuan, Chunyi Peng
The 23rd Annual International Conference on Mobile Computing and Networking (ACM MobiCom'17), acceptance rate: 35/186 = 18.8%

Control-plane operations are indispensable to providing data access to mobile devices in the 4G LTE networks. They provision necessary control states at the device and network nodes to enable data access. However, the current design may suffer from long data access latency even under good radio conditions. The fundamental problem is that, data-plane packet delivery cannot start or resume until all control-plane procedures are completed, and these control procedures run sequentially by design at the device and network nodes. In this work, we show both are more than necessary under popular usage cases. We design DPCM, which reduces data access latency through parallel processing approaches and exploiting device-side state replica. We implement DPCM and validate its effectiveness with extensive evaluations.

@inproceedings {li2017dpcm, author = {Yuanjie Li and Zengwen Yuan and Chunyi Peng}, title = {A Control-Plane Perspective on Reducing Data Access Latency in LTE Networks}, booktitle = {The 23rd ACM Annual International Conference on Mobile Computing and Networking (MobiCom'17)}, year = {2017}, month = Oct, address = {Snowbird, Utah, USA}}

The Tick Programmable Low-Latency SDR System MobiCom'17

Haoyang Wu, Tao Wang, Zengwen Yuan, Chunyi Peng, Zhiwei Li, Zhaowei Tan, Boyan Ding, Xiaoguang Li, Yuanjie Li, Jun Liu, Songwu Lu
The 23rd Annual International Conference on Mobile Computing and Networking (ACM MobiCom'17), acceptance rate: 35/186 = 18.8%
Best Community Paper Award

Tick is a new SDR system that provides programmability and low latency at both PHY and MAC. It supports modular design and element-based programming, similar to the Click router. It uses an accelerator-rich architecture, where an embedded processor executes control ows and handles various MAC events. User-defined accelerators o oad those computation-intensive, communication-heavy, fine-grained timing control tasks from the processor, and accelerate them in hardware. Tick applies a number of hardware and software co-design techniques to ensure low latency, includ- ing multi-clock-domain pipelining, field-based processing pipeline, separation of data and control flows, etc. We have implemented Tick and validated its effectiveness through extensive evaluations as well as two prototypes of 802.11ac SISO/MIMO and 802.11a/g full-duplex.

@inproceedings {wu2017tick, author = {Haoyang Wu and Tao Wang and Zengwen Yuan and Chunyi Peng and Zhiwei Li and Zhaowei Tan and Boyan Ding and Xiaoguang Li and Yuanjie Li and Jun Liu and Songwu Lu}, title = {The Tick Programmable Low-Latency SDR System}, booktitle = {The 23rd ACM Annual International Conference on Mobile Computing and Networking (MobiCom'17)}, year = {2017}, month = Oct, address = {Snowbird, Utah, USA}}

Towards Automated Intelligence in 5G Systems ICCCN'17

Haotian Deng, Qianru Li, Yuanjie Li, Songwu Lu, Chunyi Peng, Taqi Raza, Zhaowei Tan, Zengwen Yuan, Zhehui Zhang
(In alphabetical order)
The 26th International Conference on Computer Communications and Networks (ICCCN 2017), invited paper

In this paper, we call for a paradigm shift away from the wireless-access focused research efforts on 5G networked systems. We believe that the architectural limitations should share equal blame on issues of performance, reliability, and security. We thus identify architectural weakness on both sides of the mobile clients and the 4G network infrastructure. Our recent findings show that, contrary to commonly held perceptions, many design and operational issues arise not due to poor wireless link qualities. Instead, they are rooted in such architectural downsides. To address these issues, we further propose a new approach of enabling automated intelligence inside the 4G/5G network systems. We next describe our ongoing efforts along two dimensions: empowering data-driven smart clients and constructing verifiable network infrastructure. We report some early results and discuss possible next steps.

@inproceedings {li17toward, author = {Haotian Deng and Qianru Li and Yuanjie Li and Songwu Lu and Chunyi Peng and Taqi Raza and Zhaowei Tan and Zengwen Yuan and Zhehui Zhang}, title = {Towards Automated Intelligence in 5G Systems}, booktitle = {The 26th International Conference on Computer Communications and Networks (ICCCN 2017)}, year = {2017}, month = Jul, address = {Vancouver, Canada}}

cniCloud: Querying the Cellular Network Information at Scale WinTech'17

Wenguang Huang, Chang Zhou, Yuanjie Li, Songwu Lu, Xinbing Wang, Luoyi Fu
11th Workshop on Wireless Network Testbeds, Experimental evaluation & Characterization (WinTech 2017)

This paper presents cniCloud, a cloud platform for mobile devices to share and query the fine-grained cellular information at scale. cniCloud extends the single-device cellular analytics via crowdsourcing: It collects the fine-grained cellular network data from massive mobile devices, aggregates them in a cloud database, and provides interfaces for end users to run SQL-like query over the cellular data. It offers efficient and responsive processing by optimizing the database storage, and adopting the domain-specific optimizations. Our preliminary deployments and experiments validate its feasibility in performing crowdsourced analytics.

@inproceedings {huang17cnicloud, author = {Wenguang Huang and Chang Zhou and Yuanjie Li and Songwu Lu and Xinbing Wang and Luoyi Fu}, title = {cniCloud: Querying the Cellular Network Information at Scale}, booktitle = {11th Workshop on Wireless Network Testbeds, Experimental evaluation & CHaracterization (WiNTECH 2017)}, year = {2017}, month = Oct, address = {Snowbird, Utah, US}}

MobileInsight: Extracting and Analyzing Cellular Network Information on Smartphones MobiCom'16

Yuanjie Li, Chunyi Peng, Zengwen Yuan, Jiayao Li, Haotian Deng, Tao Wang
The 22nd Annual International Conference on Mobile Computing and Networking (ACM MobiCom'16), acceptance rate: 31/247 = 12.6%
Best Community Paper Award

We design and implement MobileInsight, a software tool that collects, analyzes and exploits runtime network information from operational cellular networks. MobileInsight runs on commercial off-the-shelf phones without extra hardware or additional support from operators. It exposes protocol messages on both control plane and (below IP) data plane from the 3G/4G chipset. It provides in-device protocol analysis and operation logic inference. It further offers a simple API, through which developers and researchers obtain access to low-level network information for their mobile applications. We have built three showcases to illustrate how MobileInsight is applied to cellular network research.

@inproceedings {li2016mobileinsight, author = {Yuanjie Li and Chunyi Peng and Zengwen Yuan and Jiayao Li and Haotian Deng and Tao Wang}, title = {MobileInsight: Extracting and Analyzing Cellular Network Information on Smartphones}, booktitle = {The 22nd ACM Annual International Conference on Mobile Computing and Networking (MobiCom'16)}, year = {2016}, month = Oct, address = {New York, USA}}

Instability in Distributed Mobility Management: Revisiting Configuration Management in 3G/4G Mobile Networks SIGMETRICS'16

Yuanjie Li, Haotian Deng, Jiayao Li, Chunyi Peng, Songwu Lu
The 42nd ACM International Conference on Measurement and Modeling of Computer Systems (SIGMETRICS), Antibes Juan-les-Pins, France, June 2016, acceptance rate: 28/208 = 13.4%

Mobility support is critical to offering seamless data service to mobile devices in 3G/4G cellular networks. To accommodate policy requests by users and carriers, micro-mobility management scheme among cells (i.e., handoff) is designated to be configurable. Each cell and mobile device can configure or even customize its own handoff procedure. In this paper, we examine the handoff miscon- figuration issues in 3G/4G networks. We show that they may incur handoff instability in the form of persistent loops, where the device oscillates between cells even without radio-link and location changes. Such instability is mainly triggered by uncoordinated parameter configurations and inconsistent decision logic in the handoff procedure. It can degrade user data performance, incur excessive signaling overhead, and violate network’s expected handoff goals. We derive the instability conditions, and validate them on two major US mobile carrier networks. We further design a software tool for automatic loop detection, and run it over operational networks. We discuss possible fixes to such uncoordinated configurations among devices and cells.

@inproceedings {li2016instability, title = {Instability in Distributed Mobility Management: Revisiting Configuration Management in 3G/4G Mobile Networks}, author = {Yuanjie Li and Haotian Deng and Jiayao Li and Chunyi Peng and Songwu Lu}, booktitle = {The 42nd ACM International Conference on Measurement and Modeling of Computer Systems (SIGMETRICS'16)}, year = {2016}, month = Jun, address = {Antibes Juan-les-Pins, France}, }

iCellular: Device-Customized Cellular Network Access on Commodity Smartphones NSDI '16

Yuanjie Li, Haotian Deng, Chunyi Peng, Zengwen Yuan, Guan-Hua Tu, Jiayao Li, Songwu Lu
The 13th USENIX Symposium on Networked Systems Design and Implementation (USENIX NSDI '16), acceptance rate: 45/228 = 19.7%

Exploiting multi-carrier access offers a promising direction to boost access quality in mobile networks. However, our experiments show that, the current practice does not achieve the full potential of this approach because it has not utilized fine-grained, cellular-specific domain knowledge. In this work, we propose iCellular, which exploits low-level cellular information at the device to improve multi-carrier access. Specifically, iCellular is proactive and adaptive in its multi-carrier selection by leveraging existing end-device mechanisms and standards-complaint procedures. It performs adaptive monitoring to ensure responsive selection and minimal service disruption, and enhances carrier selection with online learning and runtime decision fault prevention. It is readily deployable on smartphones without infrastructure/hardware modifications. We implement iCellular on commodity phones and harness the efforts of Project Fi to assess multi-carrier access over two US carriers: T-Mobile and Sprint. Our evaluation shows that, iCellular boosts the devices with up to 3.74x throughput improvement, 6.9x suspension reduction, and 1.9x latency decrement over the state-of-the-art selection scheme, with moderate CPU, memory and energy overheads.

@inproceedings {li2016icellular, title = {iCellular: Device-Customized Cellular Network Access on Commodity Smartphones}, author = {Yuanjie Li and Haotian Deng and Chunyi Peng and Zengwen Yuan and Guan-Hua Tu and Jiayao Li and Songwu Lu}, booktitle = {13th USENIX Symposium on Networked Systems Design and Implementation (NSDI 16)}, year = {2016}, month = Mar, address = {Santa Clara, CA}, url = {https://www.usenix.org/conference/nsdi16/technical-sessions/presentation/li-yuanjie}, publisher = {USENIX Association}, }

CAP on Mobility Control for Mobile Networks HotWireless '16

Yuanjie Li, Zengwen Yuan, Chunyi Peng, Songwu Lu
The 3rd ACM Workshop on Hot Topics in Wireless (HotWireless'16), invited paper

The CAP theorem exposes the fundamental tradeoffs among three key properties of strong consistency, availability and partition tolerance in distributed networked systems. In this position paper, we take the CAP perspective on 4G mobility control. We view the control-plane management for mobility support as a distributed signaling system. We show that the impossibility result of the CAP theorem also holds for mobility control: It is impossible for any mobility control to guarantee sequential consistency, high service availability, and partition tolerance simultaneously. Unfortunately, the current 4G system adopts its mobility scheme with the notion of sequential consistency. Our empirical study further confirms that, the incurred data unavailability (i.e., data service suspension) time is comparable to that induced by wireless connectivity setup. We argue that the desirable mobility control for the upcoming 5G networks should take a paradigm shift. We discuss our early effort on re-examining the consistency notion for higher availability and fault tolerance.

@inproceedings{li2016cap, title={CAP on Mobility Control for 4G LTE Networks}, author={Li, Yuanjie and Yuan, Zengwen and Peng, Chunyi and Lu, Songwu}, booktitle={The 3rd ACM Workshop on Hot Topics in Wireless (HotWireless'16)}, year={2016}, organization={ACM} }

A First Look at Unstable Mobility Management in Cellular Networks HotMobile '16

Yuanjie Li, Jiaqi Xu, Chunyi Peng, Songwu Lu
17th International Workshop on Mobile Computing Systems and Applications (ACM HotMobile 2016), acceptance rate: 18/55 = 32.7%

Mobility management is a prominent feature in cellular networks. In this paper, we examine the (in)stability of mobility management. We disclose that handoff may never converge in some real-world cases. We focus on persistent handoff oscillations, rather than those transient ones caused by dynamic networking environment and user mobility (e.g., moving back and force between two base stations). Our study reveals that persistent handoff loops indeed exist in operational cellular networks. They not only violate their design goals, but also incur excessive signaling overhead and data performance degradation. To detect and validate instability in mobility management, we devise MMDIAG, an in-device diagnosis tool for cellular network operations. The core of MMDIAG is to build a handoff decision automata based on 3GPP standards, and detect possible loops by checking the structural property of stability. We first leverage device-network signaling exchanges to retrieve mobility management policies and configurations, and then feed them into MMDIAG, along with runtime measurements. MMDIAG further emulates various handoff scenarios and identifies possible violations (i.e., loops) caused by the used policies and configurations. Finally, we validate the identified problems through real measurements over operational networks. Our preliminary results with a top-tier US carrier demonstrate that, unstable mobility management indeed occurs in reality and hurts both carriers and users. The proposed methodology is effective to identify persistent instabilities and pinpoint their root causes in problematic configurations and policy conflicts.

@inproceedings{li2016first, title={A First Look at Unstable Mobility Management in Cellular Networks}, author={Li, Yuanjie and Xu, Jiaqi and Peng, Chunyi and Lu, Songwu}, booktitle={Proceedings of the 17th International Workshop on Mobile Computing Systems and Applications}, pages={15--20}, year={2016}, organization={ACM} }

Understanding and Diagnosing Real-World Femtocell Performance Problems INFOCOM'16

Chunyi Peng, Yuanjie Li, Zhuoran Li, Jie Zhao, Jiaqi Xu
IEEE International Conference on Computer Communications (INFOCOM'16), acceptance rate: 18.3%

Femtocells (small cells) augment the current mobile network by providing users short-range radio access at home and small-business settings. They have rapidly emerged as a promising scheme to alleviate capacity and coverage shortage by offloading traffic from the conventional Macrocells (large cells). Despite its increasing popularity, the real-world Femtocell performance has remained largely unexplored. In this paper, we conduct an in-depth study to assess Femtocell performance and diagnose identified issues in operational carrier networks. We focus on user-deployed Femtocells in a top-tier US mobile network. While the Femtocell generally works well, unanticipated performance degradations and even failures still occur. Contrary to conventional wisdom in the research community, we find that, radio link quality and interference is not the main bottleneck of Femtocells in many real-life usage scenarios. For instance, while Femtocell deployment at blind-zones with no radio coverage is desirable, not all deployments have succeeded; Compared with their Macrocell counterparts, Femtocells exhibit lower speed and larger speed variations, and induce larger delay for data services. Moreover, mobility support for femtocells is incomplete and no seamless migration is available under certain usage scenarios. We pinpoint their root causes, quantify the potential impacts,and share the learned lessons.

@inproceedings{li16-infocom, title = {{Understanding and Diagnosing Real-World Femtocell Performance Problems}}, author = {Chunyi Peng and Yuanjie Li and Zuoran Li and Jie Zhao and Jiaqi Xu}, booktitle = {INFOCOM}, month = {April}, year = {2016}, }

New Security Threats Caused by IMS-based SMS Service in 4G LTE Networks CCS'16

Guan-Hua Tu, Chi-Yu Li, Chunyi Peng, Yuanjie Li, Songwu Lu
The 23rd ACM Conference on Computer and Communications Security (CCS'16), acceptance rate: 137/837=16.3%

SMS (Short Messaging Service) is a text messaging service for mobile users to exchange short text messages. It is also widely used to provide SMS-powered services (e.g., mobile banking). With the rapid deployment of all-IP 4G mobile networks, the underlying technology of SMS evolves from the legacy circuit-switched network to the IMS (IP Multimedia Subsystem) system over packet-switched network. In this work, we study the insecurity of the IMS-based SMS. We uncover its security vulnerabilities and exploit them to devise four SMS attacks: silent SMS abuse, SMS spoofing, SMS client DoS, and SMS spamming. We further discover that those SMS threats can propagate towards SMS-powered services, thereby leading to three malicious attacks: social network account hijacking, unauthorized donation, and unauthorized subscription. Our analysis reveals that the problems stem from the loose security regulations among mobile phones, carrier networks, and SMS-powered services. We finally propose remedies to the identified security issues.

@inproceedings{tu16-ccs, author = {Guan-Hua Tu and Chi-Yu Li and Chunyi Peng and Yuanjie Li and Songwu Lu}, title = {{New Security Threats Caused by IMS-based SMS Service in 4G LTE Networks}}, booktitle = {ACM CCS} month = {October}, year = {2016}, location = {Hofburg Palace, Vienna, Austria}, }

VoLTE*: A Lightweight Voice Solution to 4G LTE Networks HotMobile '16

Guan-Hua Tu, Chi-Yu Li, Chunyi Peng, Zengwen Yuan, Yuanjie Li, Songwu Lu
The 17th International Workshop on Mobile Computing Systems and Applications (ACM HotMobile 2016), acceptance rate: 18/55 = 32.7%

VoLTE is the designated voice solution to the LTE network. Its early deployment is ongoing worldwide. In this work, we report an assessment on VoLTE. We show that VoLTE offers no categorically better quality than popular VoIP applications in all tested scenarios except some congested scenarios. Given the high cost on infrastructure upgrade, we argue that VoLTE, in its current form, might not warrant the deployment effort. We sketch VoLTE*, a lightweight voice solution from which all parties of users, LTE carriers, and VoIP service providers may benefit.

@inproceedings{tu2016volte, title={VoLTE*: A Lightweight Voice Solution to 4G LTE Networks}, author={Tu, Guan-Hua and Li, Chi-Yu and Peng, Chunyi and Yuan, Zengwen and Li, Yuanjie and Zhao, Xiaohu and Lu, Songwu}, booktitle={Proceedings of the 17th International Workshop on Mobile Computing Systems and Applications}, pages={3--8}, year={2016}, organization={ACM} }

Demystify Undesired Handoff in Cellular Networks ICCCN '16

Chunyi Peng, Yuanjie Li
25th International Conference on Computer Communication and Networks (ICCCN 2016), acceptance rate: 30%

Handoff is critical to providing seamless network access to mobile devices in cellular networks. To accommodate diverse requirements by users and operators, micro-mobility management scheme among cells (i.e., handoff) is designated to be configurable. Each cell and mobile device can configure or even customize its own handoff procedure which likely results in inconsistent among their handoffs. In this paper, we examine the current design and practice of handoff in desired reachability. We show that handoff misconfigurations exist and they make the device stuck in an undesired target cell (e.g., 2G when 4G available). We model the distributed mobility management as an iterative process and use analysis to classify the causes. We further design a software tool for automatic loop detection, and run it over operational networks. We validate the identified issues on two major US mobile carrier networks.

@inproceedings{peng16-icccn, author = {Chunyi Peng and Yuanjie Li}, title = {{Demystify Undesired Handoff in Cellular Networks}}, booktitle = {ICCCN}, month = {August}, year = {2016}, }

Detecting Problematic Control-Plane Protocol Interactions in Mobile Networks ToN'16

Guan-Hua Tu†, Yuanjie Li†, Chunyi Peng, Chiyu Li, Songwu Lu
IEEE/ACM Transactions on Networking (ToN), 24(2): 1209-1222, April 2016

The control-plane protocols in 3G/4G mobile networks communicate with each other, and provide a rich set of control functions, such as radio resource control, mobility support, connectivity management, to name a few. Despite their significance, the problem of verifying protocol correctness remains largely unaddressed. In this paper, we examine control-plane protocol interactions in mobile networks. We propose CNetVerifier, a two-phase signaling diagnosis tool to detect problematic interactions in both design and practice. CNetVerifier first performs protocol screening based on 3GPP standards via domain-specific model checking, and then conducts phone-based empirical validation in operational 3G/4G networks. With CNetVerifier, we have uncovered seven types of troublesome interactions, along three dimensions of cross (protocol) layers, cross (circuit-switched and packet-switched) domains, and cross (3G and 4G) systems. Some are caused by necessary yet problematic cooperation (i.e., protocol interactions are needed but they misbehave), whereas others are due to independent yet unnecessary coupled operations (i.e., protocols interactions are not required but actually coupled). These instances span both design defects in 3GPP standards and operational slips by carriers and vendors. They all result in performance penalties or functional incorrectness. We deduce root causes, present empirical results, propose solutions, and summarize learned lessons.

@article{tudetecting, title={Detecting Problematic Control-Plane Protocol Interactions in Mobile Networks}, author={Tu, Guan-Hua and Li, Yuanjie and Peng, Chunyi and Li, Chi-Yu and Lu, Songwu}, publisher={IEEE} }

Insecurity of Voice Solution VoLTE in LTE Mobile Networks CCS '15

Chi-Yu Li, Guan-Hua Tu, Chunyi Peng, Zengwen Yuan, Yuanjie Li, Songwu Lu, Xinbing Wang
The 22nd ACM Conference on Computer and Communications Security (CCS '15), acceptance rate: 128/646 = 19.8%

VoLTE (Voice-over-LTE) is the designated voice solution to the LTE mobile network, and its worldwide deployment is underway. It reshapes call services from the traditional circuit-switched telecom telephony to the packet-switched Internet VoIP. In this work, we conduct the first study on VoLTE security before its full rollout. We discover several vulnerabilities in both its control-plane and data-plane functions, which can be exploited to disrupt both data and voice in operational networks. In particular, we find that the adversary can easily gain free data access, shut down continuing data access, or subdue an ongoing call, etc. We validate these proof-of-concept attacks using commodity smartphones (rooted and unrooted) in two Tier-1 US mobile carriers. Our analysis reveals that, the problems stem from both the device and the network. The device OS and chipset fail to prohibit non-VoLTE apps from accessing and injecting packets into VoLTE control and data planes. The network infrastructure also lacks proper access control and runtime check.

@inproceedings{Li:2015:IVS:2810103.2813618, author = {Li, Chi-Yu and Tu, Guan-Hua and Peng, Chunyi and Yuan, Zengwen and Li, Yuanjie and Lu, Songwu and Wang, Xinbing}, title = {Insecurity of Voice Solution VoLTE in LTE Mobile Networks}, booktitle = {Proceedings of the 22nd ACM SIGSAC Conference on Computer and Communications Security}, series = {CCS '15}, year = {2015}, isbn = {978-1-4503-3832-5}, location = {Denver, Colorado, USA}, pages = {316--327}, numpages = {12}, url = {http://doi.acm.org/10.1145/2810103.2813618}, doi = {10.1145/2810103.2813618}, acmid = {2813618}, publisher = {ACM}, address = {New York, NY, USA}, keywords = {LTE, attack, cellular networks, defense, volte},}

Control-Plane Protocol Interactions in Cellular Networks SIGCOMM'14

Guan-Hua Tu†, Yuanjie Li†, Chunyi Peng, Chi-Yu Li, Hongyi Wang, Songwu Lu
ACM SIGCOMM'14, acceptance rate: 45/237 = 18.9%

Control-plane protocols are complex in cellular networks. They communicate with one another along three dimensions of cross layers, cross (circuit-switched and packet-switched) domains, and cross (3G and 4G) systems. In this work, we propose signaling diagnosis tools and uncover six instances of problematic interactions. Such control-plane issues span both design defects in the 3GPP standards and operational slips by carriers. They are more damaging than data-plane failures. In the worst-case scenario, users may be out of service in 4G, or get stuck in 3G. We deduce root causes, propose solutions, and summarize learned lessons.

@inproceedings{tu2014control, title={Control-plane protocol interactions in cellular networks}, author={Tu, Guan-Hua and Li, Yuanjie and Peng, Chunyi and Li, Chi-Yu and Wang, Hongyi and Lu, Songwu}, booktitle={ACM SIGCOMM Computer Communication Review}, volume={44}, number={4}, pages={223--234}, year={2014}, organization={ACM} }

Scalable Opportunistic VANET Content Routing With Encounter Information VCA'13

Yu-Ting Yu, Yuanjie Li, Xingyu Ma, Wentao Shang, MY Sanadidi, Mario Gerla
The 2nd International Workshop on Vehicular Communications and Applications (VCA), 2013

Recently, Information Centric Networking (ICN) has attracted much attention also for mobiles. Unlike host-based communication models, ICN promotes data names as the first-class citizen in the network. However, the current ICN name-based routing requires Interests be routed by name to the nearest replica, implying the Interests are flooded in VANET. This introduces large overhead and consequently degrades wireless network performance. In order to maintain the efficiency of ICN implementation in VANET, we propose an opportunistic geo-inspired content based routing method. Our method utilizes the last encounter information of each node to infer the locations of content holders. With this information, the Interests can be geo-routed instead of being flooded to reduce the congestion level of the entire network. The simulation results show that our proposed method reduces the scope of flooding to less than two hops and improves retrieval rate by 1.42 times over flooding-based methods.

@inproceedings{yu2013scalable, title={Scalable opportunistic vanet content routing with encounter information}, author={Yu, Yu-Ting and Li, Yuanjie and Ma, Xingyu and Shang, Wentao and Sanadidi, MY and Gerla, Mario}, booktitle={Network Protocols (ICNP), 2013 21st IEEE International Conference on}, pages={1--6}, year={2013}, organization={IEEE} }

ESM: Efficient and Scalable Data Center Multicast Routing ToN'13

Dan Li, Yuanjie Li, Jianping Wu, Sen Su, Jiangwei Yu
IEEE/ACM Transactions on Networking (ToN), 20(3): 944-955, 2013

Multicast benefits group communications in saving network traffic and improving application throughput, both of which are important for data center applications. However, the technical trend of data center design poses new challenges for efficient and scalable multicast routing. First, the densely connected networks make traditional receiver-driven multicast routing protocols inefficient in multicast tree formation. Second, it is quite difficult for the low-end switches widely used in data centers to hold the routing entries of massive multicast groups. In this paper, we propose ESM, an efficient and scalable multicast routing scheme for data center networks. ESM addresses the challenges above by exploiting the feature of modern data center networks. Based on the regular topology of data centers, ESM uses a source-to-receiver expansion approach to build efficient multicast trees, excluding many unnecessary intermediate switches used in receiver-driven multicast routing. For scalable multicast routing, ESM combines both in-packet Bloom Filters and in-switch entries to make the tradeoff between the number of multicast groups supported and the additional bandwidth overhead. Simulations show that ESM saves 40%-50% network traffic and doubles the application throughputs compared to receiver-driven multicast routing, and the combination routing scheme significantly reduces the number of in-switch entries required. We implement ESM on a Linux platform. The experimental results further demonstrate that ESM can well support online tree building for large-scale groups with churns, and the overhead of the combination forwarding engine is light-weighted.

@article{li2012esm, title={ESM: efficient and scalable data center multicast routing}, author={Li, Dan and Li, Yuanjie and Wu, Jianping and Su, Sen and Yu, Jiangwei}, journal={IEEE/ACM Transactions on Networking (TON)}, volume={20}, number={3}, pages={944--955}, year={2012}, publisher={IEEE Press} }

Photon induced tunneling in optomechanical systems PRA'13

Xun-Wei Xu, Yuanjie Li, Yu-xi Liu
Physical Review A (PRA), 87.025803, 2013

In contrast to recent studies [Rabl, Phys. Rev. Lett. 107, 063601 (2011); Nunnenkamp et al., Phys. Rev. Lett. 107, 063602 (2011)] on photon blockade that prevents subsequent photons from resonantly entering the cavity in optomechanical systems, we study the photon-induced tunneling that increases the probability of admitting subsequent photons in those systems. In particular, we analytically and numerically show how two- or three-photon tunneling can occur by avoiding single-photon blockade. Our study provides another way on photon control using a single mechanical resonator in optomechanical systems.

@article{xu2013photon, title={Photon-induced tunneling in optomechanical systems}, author={Xu, Xun-Wei and Li, Yuan-Jie and Liu, Yu-xi}, journal={Physical Review A}, volume={87}, number={2}, pages={025803}, year={2013}, publisher={APS} }

Antibunching photons in a cavity coupled to an optomechanical system JPB'13

Xun-Wei Xu, Yuanjie Li
Journal of Physics B (JPB), 2013

We study the photon statistics of a cavity linearly coupled to an optomechanical system via second order correlation functions. Our calculations show that the cavity can exhibit strong photon antibunching even when optomechanical interaction in the optomechanical system is weak. The cooperation between the weak optomechanical interaction and the destructive interference between different paths for two-photon excitation leads to the efficient antibunching effect. Compared with the standard optomechanical system, the coupling between a cavity and an optomechanical system provides a method to relax the constraints to obtain single photon by optomechanical interaction.

@article{xu2013antibunching, title={Antibunching photons in a cavity coupled to an optomechanical system}, author={Xu, Xun-Wei and Li, Yuan-Jie}, journal={Journal of Physics B: Atomic, Molecular and Optical Physics}, volume={46}, number={3}, pages={035502}, year={2013}, publisher={IOP Publishing} }

Patents

  • Yuanjie Li, Hewu Li, Jiayi Liu, Wei Liu, Lixin Liu, Qian Wu, Jun Liu, Zeqi Lai, "Method and Device for Constructing Integrated Space-Terrestrial Network", US Patent US20240106528A1
  • Yuanjie Li, Kyu-Han Kim, Qianru Li, "Systems and Methods for Mitigating Cyberattacks", US Patent US20220272120A1
  • Yuanjie Li, Kyu-Han Kim, "Learning-Driven Low Latency Handover for 5G Mobility", US Patent US20210329522A1
  • Kyu-Han Kim, Yuanjie Li, "Data Gap Bridging Methods and Systems", US Patent US10893151B1
  • Yuanjie Li, Chunyi Peng, Songwu Lu, "Methods, systems, apparatuses, and devices for facilitating managing connections from one or more caller devices", US Patent US20210014353A1
  • Yuanjie Li, Zengwen Yuan, Jinghao Zhao, Songwu Lu, "Methods, systems, apparatuses and devices for facilitating optimizing of a network connection established between the device and one or more servers", US Patent US20210112509A1
  • Yuanjie Li, Zhaowei Tan, Kaiyuan Chen, Jinghao Zhao, Songwu Lu, "Optimizing the Wireless-powered Outdoor Target Advertising", US Patent App. 62/937,037
  • 李元杰，刘李鑫，李贺武，刘威，蓝静怡，汪宇峰，吴茜，刘君，赖泽祺，《直连蜂窝卫星网络的自助服务方法及装置》，专利申请号：202410144397.5
  • 李元杰，李贺武，陈怡梅，刘威，吴茜，刘君，赖泽祺，《一种针对伪卫星的多设备协同检测与防御方法》，专利申请号：202310912592.3
  • 李元杰，李贺武，刘威，刘李鑫，陈怡梅，吴茜，刘君，赖泽祺，《网元状态管理方法、装置、电子设备及存储介质》，国际专利申请号：PCT/CN2023/111726
  • 李元杰，李贺武，赵玮，陈怡梅，刘威，刘李鑫，吴茜，刘君，赖泽祺，《卫星自动变轨检测方法、装置、电子设备及存储介质》，专利申请号：202310839887.2
  • 李元杰，李贺武，赵玮，陈怡梅，吴茜，刘君，赖泽祺，《一种面向网络稳定性的卫星变轨方法和装置》，专利申请号：202311247368.3
  • 李元杰,刘李鑫，李贺武，刘威，陈怡梅，吴茜，刘君，赖泽祺，陆璐，郑韶雯，《星地融合互联网的稳定层次化路由方法、装置及电子设备》，专利申请号：202310675671.7
  • 李元杰, 李贺武, 刘李鑫, 刘威, 刘嘉镱, 吴茜, 刘君, 赖泽祺, 《一种星地协同组网方法及装置》, 专利授权公告号：CN114039644A
  • 李元杰, 李贺武, 吕治政, 赵玮, 吴茜, 刘君, 赖泽祺, 《天地融合网络恶意流量攻击主动抑制方法及装置》,专利授权公告号： CN114785551B
  • 李元杰, 李贺武, 刘威, 刘李鑫, 陈怡梅, 吴茜, 刘君, 赖泽祺, 《一种天地融合移动网络的网元功能状态管理机制》, 专利申请号：202211430022.2
  • 吴茜, 宋兆杰, 李贺武, 李元杰, 《用于高铁场景的多路径传输数据预调度方法及系统》, 专利授权公告号： CN113329413B
  • 赖泽祺, 李贺武, 吴茜, 邓洋涛, 刘伟森, 刘君, 李元杰, 李基豪, 刘李鑫, 吴建平, 《一种天地融合网络仿真试验系统及其试验方法》, 专利申请号：CN114785401A
  • 赖泽祺, 刘伟森, 吴茜, 李贺武, 吴建平, 刘君, 李元杰, 《一种星地协作的广域实时通信系统及其通信方法》,专利申请号： CN114915331A
  • 吴茜, 刘伟森, 赖泽祺, 李贺武, 李元杰, 刘君, 《一种星地协同的全球内容分发路由方法、系统及电子设备》, 专利申请号： CN114928869A
  • 吴茜, 张瑶蓥, 赖泽祺, 李贺武, 刘君, 李元杰, 陆璐, 郑韶雯, 《星地链路处理方法、装置及网络设备》, 专利申请号： CN114710193A

Students

I'm fortunate to work with the following talented students:

PhD students

MS students

  • Wei Zhao (2021)
  • Yufeng Wang (with Hewu Li, 2023)

Undergraduate students

  • Li Ouyang (2022)
  • Junyi Li (2022)
  • Jiabo Yang (2023)
  • Xi Long (2023)
  • Bowen Sun (2023)

Alumni

Teaching

  • Wireless and Mobile Network Security (graduate course), Spring 2022, Tsinghua University
  • Technical Reading, Writing, and Presentation for Networking Science (graduate course), Fall 2022, Tsinghua University
  • Network Protocol and Systems Software Design for Wireless and Mobile (CS211, graduate course), Fall 2015, Spring 2015, UCLA
  • Computer Network Fundamentals (CS118, undergraduate course), Fall 2013, Fall 2014, UCLA
  • Introduction to Computer Science (CS31, undergraduate course), Winter 2014, UCLA
  • Introduction to Computer Organization (CS33, undergraduate course), Spring 2014, UCLA

Services

  • Program committee member:
    • 2025: USENIX NSDI
    • 2024: ACM SIGCOMM, USENIX NSDI, IEEE INFOCOM, ACM CoNEXT, IEEE ICNP, IEEE ICCCN
    • 2023: ACM CoNEXT, IEEE ICNP, ACM SIGCOMM workshop on 5G-MeMU, ACM WiNTECH
    • 2022: ACM MobiCom, IEEE ICNP, ACM ICN, AAAI, APNet, ACM WiNTECH, EAI 6G-xCOM
    • 2021: ACM MobiCom, IEEE ICNP, ACM SIGCOMM workshop on 5G-MeMU, IEEE MSN, AAAI
    • 2020: ACM MobiCom, IEEE INFOCOM (external)
    • 2018: ACM Ubicomp, ACM SIGCOMM Workshop on VR/AR
    • 2017: IEEE INFOCOM, IEEE PAC, ACM MobiCom (external), IEEE CNS, ACM WinTech
    • 2016: ACM CarSys, ACM MobiCom (external)
  • Journal reviewer: IEEE/ACM Transactions on Networking (ToN), IEEE Transactions on Mobile Computing (TMC), IEEE Transactions on Dependable and Secure Computing (TDSC), IEEE Transactions on Computers (TC), IEEE Network Magazine, IEEE Access, China Communication
  • Session chair: ACM APNet’22, ACM MobiCom’21, IEEE ICNP’21
  • Juror of ACM SIGCOMM'19 Student Research Competition (SRC) and hackathon
  • Social Media Chair for ACM MobiCom'18
  • Member of UCLA Graduate Student Admission Review Committee, 2016-2017

Software and Dataset

MobileInsight
Runtime, fine-grained cellular network analytics inside your smartphone [MobiCom'21] [MobiCom'16] [software] [dataset].
SpaceCore
A stateless mobile core network for low-earth-orbit (LEO) satellite mega-constellations [SIGCOMM'22][artifact]
REM
Reliable Extreme Mobility Management for 4G, 5G and Beyond [SIGCOMM'20][artifact]
High-speed rails
A 357.9 GB dataset with TCP pcap and LTE signaling traces, by traveling 51,367 km on the Beijing-Shanghai (300/350 km/h) route [MobiCom'19][dataset]
LRP
Reducing mobile network latency at the application layer [NSDI'21][code]
Mobile VR in LTE
An 8-month empirical study over top-four U.S. carriers. [SIGMETRICS'18] [dataset].
DPCM
Control-plane acceleration for low-latency mobile network [MobiCom'17][software]