Research On Embedded Remote Display System

As a graphical interface based remote control platform, remote display system is widely used in remote application systems, such as, management, assistance, treatment, and education. Recent years, the rise of mobile computing brings remote display system a new opportunity. People began to think that how to utilize the advantage of remote display system in embedded system and mobile computing to provide more and better services. However, most of the remote display systems can only work well on LAN or other networks with good connections and bandwidth. When the conditions are not satisfied, such as, on WAN or wireless networks, the systems'performance will decrease rapidly with the decrease of connections and bandwidth, or even fails. To embedded system, the cost of communication is a considerable part of the whole energy cost. And most of the remote display systems are designed for PC without consideration of energy efficiency. All these make the design and development of embedded remote display system more complex and difficult. We analyzed some representative remote display systems'key technologies of remote display mode, update mechanism, compression, cache design, and evaluation method, and abstracted a work model from them. We also built an embedded system environment with graphical interface by porting Nucleus OS and its graphics package onto Linkup 7210 system developing board. Depending on our analysis, we chose VNC as our research prototype system. We upgraded its communication module to support serial communication, which is mostly used in embedded system and our evaluation. In porting its client program onto the embedded system, we designed "single task round robin"work mode instead of the original "two threads parallel"one to make the communication more energy efficient. Finally, to reduce the communication traffic and computing of embedded system, we redesigned the gathering method of screen update and, correspondingly, preprocessing and compressing algorithms. The new method gets screen update area from the graphics driver layer, which makes the area more precise. And the new algorithms reduce and divide the screen update area into some small pieces which contain only one type of text, icon, GUI graphics and bitmap, and compress these pieces separately. The evaluation shows that our design's communication traffic is about 10% to 20% lower than the original one. And since the area handled by client program is also reduced, and our decoding algorithm in client is very simple, the computing of embedded system is also reduced.