Graphical update caching for mobile thin clients
Bert Vankeirsbilck · Ghent University Academic Bibliography (Ghent University) · 2009
Because of form factor constraints, required portability and battery lifetime, mobile devices have limited resources. Despite the rapid development of smaller and more efficient hardware, software requirements on CPU, memory and disk space cause significant hardware needs and battery drains. The general idea behind this article is to extend the mature thin client technology for use on mobile devices, offloading heavy computations to a distant server and leaving the applications unaltered. User input is sent over a network towards a server that executes the application, the generated screen updates are returned to the user’s device. The functionality of the mobile device is reduced to presenting graphical output, capturing user events such as key strokes and pointer movements, and transmitting data over the network. The overall goal of this doctoral study is to enable demanding applications on mobile thin clients. This will be reached by optimizing thin client computing concepts on the protocol level, as well as on the infrastructural level and the application level. The need for multi-layer optimizations is thoroughly explained in [1]. In this paper we propose graphical update caching as a method to reduce long term redundancies in thin client sessions. When analyzing the sequence of graphical updates generated by a typical user session on a desktop computer, we found that a lot of frames re—————————————————– B. Vankeirsbilck is with the Department of Information Technology of Ghent University (UGent), Belgium. E-mail: [email protected]. semble others that have already been transmitted earlier in that session. Since we operate in a thin client environment where all graphical updates have to be sent over a wireless, limited bandwidth network, benefit can be found in this phenomenon by storing well-chosen key frames both at client and server side, and transmitting only the differences with respect to that frame. Since less data is to be received from the network at the client, the battery autonomy of the device decreases slower. This will contribute to the user satisfaction and will lessen the load on the environment. We assess the bandwidth optimization potential of a static cache. This is a cache for graphical updates, that is filled before the thin client computing session starts. When the user logs in, the cache is loaded both at client and server side, and does not get altered during this session.