File Transfer Protocol Research In Mobile Transparent Computing Based On Cross-Layer Design

:Mobile transparent computing is a kind of computing model in which users only need to concern about the services they need other than the underlying operating system and hardware. In recent years, along with the rapid development of mobile smart devices, mobile transparent computing has gained broad application prospects. File transfer protocols for communications between the clients and servers play a very important role in mobile transparent computing. Research on file transfer protocols focus on how to improve the transmission efficiency and performance at the premise of ensuring easy to use.This thesis analyzes the characteristics of mobile transparent computing systems which use IEEE802.11wireless LAN. Transparent mobile terminals have limited resources and IEEE802.11wireless LAN channel rate varies with time. To solve these problems we improve TFTP (Trivial File Transfer Protocol) and propose a dynamically adaptive window size lightweight file transfer protocol DTFTP (Dynamic Trivial File Transfer Protocol).We introduce sliding window mechanism into TFTP to break its lockstep feature in DTFTP. Further on, we propose a cross-layer design scheme of the IEEE802.11wireless LAN, through sending the rate of the physical channel to upper file transfer protocol. Then, we analyze IEEE802.11data transmission process in detail and conclude the relationship between the underlying channel rate and the size of the sending window. Considering about the mobile transparent clients’feedback, we propose a dynamic adjustment mechanism for our sliding window mechanism. The window size can be adaptive and channel utilization and transmission performance is improved.Furthermore, we propose a window smoothing mechanism to prevent DTFTP from window size fluctuation and data transmission instability because of rate fluctuation of wireless LAN in some special application scenarios. The window smoothing mechanism replace the channel window size calculated by the dynamic adjustment mechanism of sliding window with the moving average of the previous channel window size. The window smoothing mechanism can smooth the paroxysmal change of the window size caused by the channel rate fluctuation. Thus, it can improve the stability of DTFTP.In this paper, we apply DTFTP in a mobile transparent computing system. We conduct a comparative analysis between DTFTP and TFTP in terms of transmission rate and packet loss. The results show that the DTFTP improves data transmission performance of mobile transparent computing system while maintaining low packet loss.