Studying And Realizing Wireless One-way Transmission System Based On USB Interface

As the country promotes Government Online Project and realizes the office automation of the government bodies in a more cost-effective manner, more and more departments at all levels of party and government have all set up computer network internally. Because these network keep large number of secret, so during the process of the government's setting up the project of the internal network, security always play a very important role in projects. Meanwhile, because the need of transmitting data between internal network and external network exist, the security of guaranteeing data transmission between the internal and external networks seems especially important.The traditional method is that physics separates two different networks. While needing the data to transmit, adopt the artificial way to transmit through the floppy disk or the magnetic disc, etc. But this kind of method is not very convenient, and may dip in and catch virus. The prevalent method is to implement the safe floodgate, the safe and effective one-way data transmission method, but the safe cost is too high and the hardware costs too expensive. Based on this the paper has studied the method to change the driver of wireless network adapter, make the data between different networks keep one-way to transmit.In the thesis I have researched IEEE 802.11 wireless LAN protocol and USB 1.1 protocol in detail, and analyze the physics layer and chain layer of the wireless LAN. And because the ATMEL wireless network adapter adopt Direct Sequence Spread Spectrum (DSSS), the paper described the protocol especially and describe its physical layer convergence protocol (PLCP) sub layers of frame structure and general MAC data frame format. And describe the USB system and its character; analyze the data transmission and the USB diagraph format. According to some source codes, the structure and workflow of Linux USB subsystem have been researched. I have analyzed the key data structure, and carry on exhaustive analysis to USB kernel.Because Linux system has such performance as open source codes, outstandingdependability and support multi-user, etc, the research approaches of this text are all based on Linux platform. The focal point of this text lies in adopting the module method , use such tools as Emacs , Gcc , Gdb , Kdb ,etc, join to Linux kernel to run after compiling the driver into the module, and have realized the one-way transmission of the data. The send end and receive end have different software support respectively, after finishing install it, it support heat to insert and pull out, and one-way transmitting etc. The process of data transmission, the important method of the driver, and the important sub modules in the driver have been carried on exhaustive analysis. And after finishing in all modules, detailed test have been performed in each unit and the whole, including the transmission speed, the one-way performance and the security performance.