Abstract
A seamless 3G (3rd generation) access system was designed and implemented to meet the remote video monitoring and remote equipment control requirement in facility agriculture without a wired connection to the Internet. The system consists of a wireless communication module including 3G SIM card and wireless router and a VPN (virtual private network) module, and uses L2TP (layer 2 tunneling protocol) and IP security to borrow lines from VPN server to solve the problem of determining a private 3G NAT (network address transaction) address. It provides sufficient video bandwidth and cheap wireless network access solutions, has characteristics of low cost, high universality, good extensibility and can be easily implemented. This system has now been put into operation in the school base, whereby we can monitor environmental parameters remotely, control the base server device, and watch smooth, clear, real-time video (video server uses H.264 format for video compression and code rate for 256-800Kbps preset).