| With the rapid development of wireless and large-scale appearance of 3G network and WiFi network, traditional household cable router has been increasingly unable to meet people's needs. It urgently requires a more portable, more mobile device. With 3G-WiFi router, people can set up wireless local area network and access Internet while moving. 3G-WiFi router provides WiFi network for mobile station at one end and connects to the Internet through the 3G network the other end. In the middle layer 3G data and WiFi data are transferred to each other using network address translation protocol and port address translation protocol. A wireless terminal can get acess to wireless network provided by 3G-WiFi router, and then connect to the Internet.This paper describes the method to finish 3G-WiFi router with Linux in embedded systems environment. The steps are development platform choosing, WiFi design,3G design and routing layer design. Micro2440 with full feature and good performance is selected as hardware platform and Linux-2.6.32.2 is selected as software platform. Access Point is implemented by Hostapd, and then we can change SSID and frequency. Transform from USB to serial is fulfilled by USB_ModeSwitch, and pppd can dial up to 3G network. In the middle layer Iptales finish the work of PAT which makes 3G data and WiFi data conversion. It also describes the cross-compiler environment, bootloader, kernel, root file systems, those are very important part of system.Article also analysis some related technology and protocols, incluing the IEEE 802.11 protocol,3G mobile communications technology, USB protocols and PPP protocols, which can give a more fully guidance in function realization.The system can function as access point. By connecting it, multiple wireless terminals with WiFi share Internet. It can also provide a mobile networking solution and guide the design of mobile devices. |
