Seamless Handover Between WIFI And3G Based On Android System

With the development of wireless communication and the improvement ofvarious functions of the mobile equipment，the user’s demand for wireless mobilenetwork experience has been increasing. Nowadays, the data rate of wirelessbroadband network and cellular mobile network have reached a very high level, whilethe interoperability between wireless broadband (WIFI) and cellular mobile (3G)needs to be improved.For mobile device users, when changes happen in network environment,network switching which means the user IP address changing will happen, and thiswill impact user’s network fluency and degrade user experience. Therefore, a virtualnetwork card is added inside the device between true network card and the user plane,so that the user can communicate directly with the virtual NIC, and when networkswitches, the virtual IP address for the user plane remains unchanged, to successfullycomplete seamlessly switching.In addition, the source IP address within a packet transmitted to the Internet bythe virtual NIC is a virtual address which does not exist, so it cannot be normallyparsed for the Internet. This will lead to the interruption of communication. Therefore,a sever is added between client and the Internet to act as a gateway providingNetwork Address Translation (NAT) function to transfer virtual IP address into theaddress of the server, which could be successfully resolved in the Internet. And afterreceiving the returned information, the sever will send the information back to theclient to complete the communication process. In addition, to identify differentprocesses in multiple client, recognition function is added at sever side to easilyhandle multiple customer information.This scheme uses Android system as the software platform and Intel Medfieldsmartphone as hardware platform to study seamlessly switching between WIFI and3G network. First it introduces the development of wireless communication, and thendescribes the current leader technology in wireless communication, including WIFI、3G and Long Term Evolution LTE. And a brief description of the software platform-Android system architecture and building blocks is given. For seamless switchingtopics, First it proposes the overall system program, including the transmissionprocess and reception process, and then focuses on the client and server side todiscuss the main solution and system configuration. Finally it uses Wireshark tool tograsp package, and the system transmission process is showed through screenshots.