By Lily Sun, Research Program Manager, Microsoft Research Asia
As mobile browsing continues to consume an ever larger share of Internet services, the stakes of improving the mobile user experience have never been greater.
That’s one of the reasons that Microsoft Research Asia (MSRA) and Peking University are embarking on a joint project to raise the quality of user experience (QoE) for mobile browsers. Building on the success of earlier collaborations, MSRA researcher Yunxin Liu will once again join forces with Xuanzhe Liu, associate professor at the university’s School of Electronics Engineering and Computer Science.
The mobile experience
It’s common sentiment that the QoE of mobile web browsing is far from satisfying. Mobile browsers suffer from the redundant transfer of resources, which leads to duplicated data transmission, long page load time, and high energy drain.
Building a collaborative team
Representing their organizations, Yunxin and Xuanzhe have jointly conducted various in-depth studies covering mobile web performance, Android OS latency, human-computer interactions, and related technologies. After first winning a Microsoft Fellowship in 2007, Xuanzhe came to MSRA in 2013 as “Star-Track” Young Visiting Professor.
The two researchers co-authored a number of papers presented at top conferences such as the International World Wide Web Conference (WWW), and published in leading journals including IEEE Transactions on Mobile Computing and IEEE Transactions on Services Computing. Together they’ve fostered a strong, sustained relationship between the two organizations.
“In our collaborations, Microsoft Research, as a leader in operating system research and industry, is able to provide first-hand, real-world users’ requirements and industry resources, where we can explore valuable and interesting problems to tackle”, says Xuanzhe. “Furthermore, collaborating with top researchers in Microsoft Research greatly helps promote the rapid growth of my students. Working with Dr. Yunxin Liu and other colleagues from the System Research Group is really an invaluable opportunity.”
Solving the puzzle of web cache performance
The team’s focus on QoE issues in mobile web browsing has led to some key findings. Research papers published in IEEE Transactions on Mobile Computing and WWW showed mobile web browsing currently suffers from an imperfect cache mechanism. The studies — based on analyzing 1 month of version traces for more than 100 popular web apps — pinpoint three root causes for the weak mobile web cache performance:
- Same content. The same resources have different URLs when requested at different times.
- Heuristic expiration. The caching policy is not explicitly defined by the server and thus it depends on browsers to infer an expiration time.
- Conservative expiration time. The expiration time is set to be too short.
at the IEEE International Conference on Web Service (ICWS). Analyzing the differences between native apps and web apps with the same functionality, their results helped inform how native apps package resources before delivering them to the user.
Building the dual proxy solution
The findings enabled the team to design and implement a dual-proxy system to optimize the QoE of mobile web browsing. Consisting of a remote proxy on the cloud/cloudlet and a local proxy on a client device, the system differs from traditional proxies that remain largely limited to simple request forwarding and cache lookup. The improved remote proxy can proactively crawl and render webpages from web servers. It can store all the downloaded resources in loading each webpage as well as build a resource loading graph for the webpage. As a result, proxies can now determine the resources required to load the webpage. And crucially, they can optimize the order in which they should load.
Now when a client requests a webpage (via the local proxy of the client), the remote proxy can immediately send all the pre-fetched resources of the webpage to the client in a batch and in the right order.
So far, the project is showing measurable success: An evaluation of 50 websites indicate average page load time is reduced by 43.1 percent and network data transmission is cut by 57.6 percent — while imposing marginal system overhead. Given these findings, the team is hopeful that their project will lead to improved QoE of mobile web browsing on a broader scale.