Data Transfer Unit Work Process and Application Area

The data transfer unit DTU (Data Transfer Unit) is a wireless terminal device specially used to convert serial port data into IP data or convert IP data into serial port data for transmission through a wireless communication network.

After the GPRS DTU is powered on, it first reads the working parameters stored in the internal FLASH (including GPRS dialing parameters, serial port baud rate, data center IP address, etc., which have been configured in advance).

GPRS DTU logs on to the GSM network, and then performs GPRS PPP dialing. After dialing is successful, GPRS DTU will obtain an internal IP address randomly assigned by the mobile (usually 10.X.X.X). In other words, GPRS DTU is in the mobile intranet, and its intranet IP address is usually not fixed, and changes with each dial-up. We can understand that GPRS DTU is a mobile device in the internal LAN at this time, through the mobile gateway to realize the communication with the external Internet public network. This is similar to the way that computers in the local area network access the external network through the gateway.

GPRS DTU actively initiates a communication connection with the data center and keeps the communication connection always present. Because GPRS DTU is in the mobile intranet, and the IP address is not fixed. Therefore, only the GPRS DTU can actively connect to the data center, and the data center cannot actively connect to the GPRS DTU. This requires the data center to have a fixed public IP address or a fixed domain name. The public IP address or fixed domain name of the data center is stored as a parameter in the GPRS DTU, so that once the GPRS DTU is successfully dialed up, it can actively connect to the data center.

Specifically, GPRS DTU initiates a TCP or UDP communication request to the data center through the data center’s IP address (if the center domain name is used, the center IP address is first resolved through the center domain name) and port number and other parameters. After receiving the response from the center, the GPRS DTU considers that the handshake with the center is successful, and then keeps the communication connection in existence. If the communication connection is interrupted, the GPRS DTU will immediately re-handshake with the center.

Since the TCP/UDP communication connection has been established, two-way data communication can be carried out.

For DTU, as long as the two-way communication with the data center is established, it is relatively simple to complete the conversion between user serial port data and GPRS network data packets. Once the user’s serial port data is received, DTU immediately encapsulates the serial port data in a TCP/UDP packet and sends it to the data center. Conversely, when DTU receives a TCP/UDP packet from the data center, it takes out the data content and sends it to the user device through the serial port immediately.

Through the wired data acquisition center, it can communicate with many GPRS DTUs simultaneously. This is the most commonly used method in GPRS DTU application systems.

The main function of DTU is to wirelessly transmit data from remote devices back to the back-end center. As shown in the figure on the right, to complete the data transmission, a complete data transmission system needs to be established. In this system include: DTU, customer equipment, mobile network, back-office center. At the front end, DTU and customer equipment are connected through 232 or 485 interface. After DTU is powered on and running, first register to the mobile GPRS network, and then go to establish a SOCKET connection with the background center set in DTU. The back-end center is the server of SOCKET, and DTU is the client of SOCKET connection. Therefore, only DTU cannot complete the wireless transmission of data, and it needs to be used with the cooperation of background software. After the connection is established, the front-end equipment and the back-end center can carry out wireless data transmission through DTU, and it is two-way transmission.

DTU has been widely used in power, environmental protection, LED information release, logistics, hydrology, meteorology and other industries. As shown in the figure above, although the application industries are different, the principles of application are the same. Most of the DTUs are connected to industrial equipment, such as PLCs, microcontrollers and other automation products, and then establish a wireless communication connection with the background. Today, with the increasing development of the Internet, the use of DTU has become more and more widespread. It provides help for various industries and the integration of information and industries among various industries.

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