My research work has led to actual effect on industrial systems including Baidu PhoneGuard, Xiaomi Mobile, MIUI OS, Tencent Game Buddy, Tencent App Store, Tencent Offline Downloading, 360 CloudDisk, and

Why Does Android Stop Responding?

✎ Android users often experience poor responsiveness, in particular Application Not Responding (ANR) and System Not Responding (SNR) that directly disrupt user experience. We make an in-depth study of ANR/SNR at scale in the wild, uncover multifold root causes of ANR/SNR, and pinpoint the largest pathology that roots in Android's flawed implementation of Write Amplification Mitigation (WAM). We design a practical approach to eliminating this largest root cause; after large-scale deployment, it reduces almost all ANR/SNR caused by WAM.

Paper in MobiCom'20


✎ By examining apps' API invocations, we build APIChecker, an machine learning-based mobile malware detection system. The key to successfully developing such systems is manifold: 1) feature selection, 2) feature engineering, 3) app analysis speed, 4) developer engagement, and 5) model evolution. Failure in any of the above aspects would lead to "wooden barrel effect" of the entire system. APIChecker is adopted by Tencent Android App Store to efficiently check 10K newly submitted apps per day.

Paper in EuroSys'20

UFC2: User-Friendly Collaborative Cloud

✎ Mainstream cloud storage services all support collaborative file editing, which however often leads to poor experiences. We unravel a number of their design and implementation issues as the root causes. Thereby, we reconsider their collaboration support from a novel perspective of operations without using any locks. To enable this, we design intelligent approaches to the inference and transformation of users' editing operations, as well as optimizations to the maintenance of files' historic versions. We build an open-source system UFC2 to embody our design, which can avoid most conflicts with little overhead.

Paper in FAST'20

Mobile Gaming on PCs with Direct Android Emulation

✎ Efficiently emulating heavy 3D Android games on Windows PCs has long been desired while highly challenging. This paper presents DAOW, a commercial game-oriented Android emulator that implements the idea of direct Android emulation, which directly executes Android app binaries on top of x86-based Windows PCs without employing virtualization techniques. It has been widely adopted by 50M+ PC users to run thousands of heavy 3D Android games, achieving almost the same level of smoothness as being played natively on Android smartphones.

Paper and Best Demo Award in MobiCom'19


✎ Linux-based IoT devices have emerged as one primary target of today's cyber attacks. To understand realistic attacks on such devices at scale in the wild, we deploy 4 hardware IoT honeypots and 108 specially designed software IoT honeypots across eight mainstream public clouds. The measurement study leads to multi-fold insights towards actionable defense strategies that can be adopted by IoT vendors and end users.

Paper in MobiSys'19.


✎ As a key UI feature of Android, overlay enables one app to draw over other apps by creating an extra View layer on top of the host View. While greatly facilitating user interactions with multiple apps at the same time, it is often exploited by malicious apps (malware) to attack users. To combat this threat, we build OverlayChecker to automatically detect overlay-based malware at market scales. It is adopted by Tencent Android App Store to efficiently check 10K newly submitted apps per day.

Paper in MobiSys'19.

Xiaomi MVNO

✎ Mobile virtual network operators (MVNOs) operate on top of existing cellular infrastructures of base carriers, while offering cheaper or more flexible data plans. We present a two-year measurement study towards understanding various key aspects of today's MVNO ecosystem, based on Xiaomi MVNO with 1M customers. Our measurements clarify several key concerns raised by MVNO customers. We also leverage big data analytics and machine learning to optimize an MVNO's key businesses such as data plan reselling and customer churn mitigation.

Paper in MobiSys'19.

Web-based Delta Sync for Cloud Storage Services

✎ Striving towards a practical web-based delta synchronization solution for cloud storage services (e.g., Dropbox). Leveraging a series of state-of-the-art web techniques (JavaScript, WebSocket, HTML5 File APIs, and asm.js) and cloud techniques (virtual machine, object storage, and node.js), we have developed an open-source prototype solution WebR2sync+, and a usable online system THU-CloudDisk that has integrated our solution.

Paper in FAST'18.

FBS-Radar: Uncovering Fake Base Stations at Scale in the Wild


✎ Yet another key component of Baidu PhoneGuard, FBS-Radar precisely identifies malicious fake base stations (FBSes) and accurately geolocates FBSes based on crowdsourced data of nearly 100 million users. It protects users from millions of spam and fraud SMS messages per day, and has helped the Ministry of Public Security of China arrest hundreds of FBS operators. Also, we have made a public website that shows the current locations of detected FBSes in real time.

Paper in NDSS'17.

Cross-App Cellular Traffic Optimization with Baidu TrafficGuard


✎ As a key component of Baidu PhoneGuard, Baidu TrafficGuard is a third-party mobile traffic proxy widely deployed for Android 4.0+ devices in China. It effectively reduces cellular traffic using a network-layer VPN that connects a client-side proxy to a centralized traffic processing cloud. Most importantly, it works transparently across heterogeneous applications, so is not constrained to any specific app.

Paper in NSDI'16.

Offline Downloading in China: A Comparative Study


✎ Examining two typical implementations of "offline downloading" in China: the  cloud-based approach and the smart AP (access point, also known as home router) based approach. Driven by the measurement findings, we design and implement an intelligent middleware, Offline Downloading Redirector, to help users achieve the best expected performance.

Paper in IMC'15.

Towards Network-level Efficiency for Cloud Storage Services

✎ Addressing a simple yet critical question: Is the current data sync traffic of cloud storage services efficiently used?   Based on real-world traces and comprehensive experiments, we discover that a considerable portion of the data sync traffic is in a sense wasteful, and can be effectively avoided or significantly reduced via carefully designed data sync mechanisms.

Paper in IMC'14.

Efficient Batched Synchronization for Cloud Storage Services

Acting as a middleware between the user's file storage system and a cloud storage application (e.g., Dropbox), our proposed UDS (i.e., update-batched delayed sync) mechanism properly batches updates from clients to minimize the "traffic overuse problem", while preserving the rapid file synchronization that users expect from cloud storage services.

Papers in Middleware'13 and CCCF'14 (Cover Article).

Cloud Transcoder

✎ Bridging the format and resolution gap between Internet videos and mobile devices by utilizing an intermediate cloud platform. The user only sends his video request to Cloud Transcoder which does everything else: download, transcode, cache, transfer back, and so forth.

Paper in SIGMM NOSSDAV'12.

  Cloud Download  (or says Offline Download)

Achieving high-quality content distribution (especially for unpopular videos) by using cloud utilities as a cache to guarantee the data health and enhance the data transfer rate. Please try the large-scale  Xuanfeng Cloud Download system!

Papers in ACM-MM'11 and JCST'15.

Cloud Tracker  (or says Open-P2SP content distribution)


✎ Dynamically tracking and integrating various third-party servers, contents and data transfer protocols all over the Internet into a large, open and federated P2SP (peer-to-server/peer) platform, so as to accelerate the content distribution from servers to clients and among peer swarms. It also facilitates load-balancing among the involved servers. Please try the large-scale  Xunlei or Xuanfeng system!

Papers in ACM-MM'11 and TPDS'13.