Research On Acceleration Of Virtual Desktop Display In Thin Terminal Based On RDP Protocol

With the development of distributed technology and virtualization technology,human society has already entered the era of Cloud computing,desktop virtualization service is a typical application of the current Cloud computing services,but the current desktop virtualization service still have some problems that can’t be ignored.On the one hand,thin client in market almost consist of customized thin client,smart phone and tablet,It is costly for users to upgrade from traditional PC devices to thin clients;On the other hand,the user’s experience quality of thin clients depend on network bandwidth conditions.In the low bandwidth condition,there is some delay in the interaction between the client and server,which seriously reduces the quality of the user experience.Aiming at the problems existing in desktop virtualization services,Silicon Motion Company Limited had designed a lightweight thin client based on SM768 graphics card.In order to reduce the use cost,the client only retains the two basic functions: communication with the server and virtual desktop display.In the development of the thin client software layer,the work of this study mainly finishes two aspects,the first is the development of the client remote desktop protocol application,and the second is the development of virtual desktop display driver.In this study,Remote Desktop Protocol(RDP)was selected as the thin terminal Protocol for supports multi-channel communication and has good system compatibility.Linux specifically provides the frame buffer driver interface for Graphics card,and a frame buffer based RDP display driver was designed in this study.In order to improve the user experience on thin client platform,this study researches the display acceleration of virtual desktop.Firstly,according to the characteristics of the desktop image data slicing,compression and retransmission of the RDP protocol,this study designed a new RDP client by adding Ping-Pong buffer to the client and separating the data buffering process and data decompression process into two threads with multi-thread technology,so as to increase data throughput and speed up data processing.Although caching mechanism had increased the client’s data throughput,but unable to solve the low transmission speed of the network bandwidth,this study designed a virtual desktop acceleration method based on Markov chain forecast model,we add the JPEG decoding module in the RDP protocol and use the Markov chain to predict the complexity of next screen image update,in this way,the high complexity of image using lossy encoding,and the color simple image use lossless encoding.Simulation in Spyder IDE show that the proposed scheme can meet the user’s image quality requirements and significantly reduce the display delay of the virtual desktop.This method also has good flexibility by adjusting the complexity threshold,hence the improved RDP client could be expected to be applied in different network bandwidth conditions in Cloud computing.