本GPRS终端运输层采用UDP用户数据包协议，网络层采用IP网际协议，链路层采用PPP点对点协议。车台在32秒之内如果没有需向中心回传的信息，自动向中心回传一条网络测试信息，中心在收到此信息后必须自动回传一条确认信息。-the transport layer GPRS terminal users using UDP packet agreement, the network layer using IP Internet Protocol. PPP link layer using point-to-point agreement. Cars in Taiwan within 32 seconds if no need to Return to the Center of information, automatic Return to the Center, a network test information, the center received this information automatically back- a confirmation message.