Because in the GPS_GPRS positioning system, involves the GPS satellite positioning technology and GPRS general packet wireless service related applications, so in the system composition, GPS and GPRS is undoubtedly the core department of the whole system, the following on the GPS system and GPRS system, based on the application as the premise of the following brief introduction. 

　　The Global Positioning System (GPS) is a new generation of satellite navigation and positioning system developed by the United States from the 1970s, which took 20 years and cost 20 billion US dollars and was fully completed in 1994. It has the ability to carry out all-round real-time three-dimensional navigation and positioning in the sea, land and air. 

　　GPRS is the standard for packet data in the GSM system of the European Telecommunications Association. It USES channel bundles (at present the design of the GPRS can be realized in a carrier frequency or eight channel bundling) and enhanced data rates improved to realize high-speed access, in theory, can provide up to 115 KBPS air interface transmission rate, made a number of mobile users can share a wireless channel at the same time, a mobile user can also use multiple wireless channel. Users who do not actually send or receive packets account for only a small part of network resources, and network capacity is occupied only for actual transmission.

　　In order to implement GPRS, three new logical network entities need to be introduced into the existing GSM network: Service GPRS Support Node (SGSN), Gateway GPRS Support Node (GGSN) and Packet Control Unit (PCU). The most fundamental difference between GPRS and the existing GSM voice system is that GSM is a circuit switched system, while GPRS is a packet switched system. Therefore, GPRS is especially suitable for intermittent, burst or frequent, small amount of data transmission, but also for the occasional large amount of data transmission. This feature is suitable for most mobile Internet applications. 

　　Based on the above brief introduction of GPS system and GPRS system, the composition and characteristics of the vehicle terminal of GPS_GPRS positioning system can be obtained. The block diagram of the system structure is shown in Figure 1. The system workflow is as follows: the vehicle terminal of the GPS_GPRS positioning system uplows the current GPS geographic location information obtained by it to the system server through GPRS. The client may, by way of special GIS software or Internet explorer to browse for the current monitor vehicle location, speed and direction for real-time monitoring, and can through the network to control vehicle terminal, mobile vehicles and monitoring center of two-way data transmission, complete the vehicle running state monitoring, security, technical state.

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