A Study Of DTU Point-to-point Wireless Communication Based On MC509

DTU(Data Transfer Unit)is a wireless terminal equipment which transfers IP data converted from serial data. With the progress of embedded chip technology and mobile telecommunication technology, DTU technology and application has been developing rapidly in recent years. DTU-related products are widely used in industry, national defense and other situations which require data acquisition, remote wireless data transmission, on-line monitoring etc in various walks of life.A research subject I participated in needs radar plot and track data transmission, which is point-to-point wireless and remote. Combining project requirements, resources, cost, skill and other factors, the research chooses non-embedded DTU wireless communications as the solution, and HUAWEI MC509 as the core hardware module which is compatible with China Telecom 3G CDMA2000 1x. Mainly aiming at the software part, this paper makes a systematic study from the shallower to the deeper step by step. The research covers the contents such as serial communication, DTU functional configurations, and the parsing of data stream. Besides, software frameworks and test methods of wireless transmission are also included.Firstly, this paper follows a basic experimental sample of DTU by a few serial assistant software tools, and master the preliminary configuration method and working process of DTU what lay a good foundation for the further research. As a matter of fact, both using AT instructions to make the functional configuration of 3G module and sending & receiving data are proceeded in serial interface. Therefore a serial communication program is essential. In this paper, it is developed as a Windows C++ forms application by using a Seraial Port class on Dot Net platform, and the way of serial communication processing is status inquery. In order to confront parsing of serial data stream with kinds of complex structures later, a rich functional, flexible and practical class simply named Data Buffer is specifically designed to be called.Next, the research goes through parts of AT instruction, and then extend forward to how to use serial port application automatically interact wiht 3G module by AT instruction. The solutions of it come to be serveral software processes, one of which is general whilethe others are for the special cases. On the basis of the serial communication and AT instructions, the paper made a further study on how to realize the functional configurations of DTU by the integrated use of multiple AT instructions. According to the requirements, the system model steps out the usual practice of multipoint-to-center model, and uses the point-to-point model instead. However, in this case, both of sender’s and receiver’s IP are dynamic, and it accompanies a variety of error circumstances when the two sides establish auto-connection, or needs human invention when manul-connection. Hence, after serveral attampts, this paper adopts the method of request and reply, in which both sides exchanging SMS text messages to establish reliable handshake, and finally establish a TCP/IP connection successfully as the channel of transparent data transmission. Relatedly, the further research also achieves automatic maintenance of DTU’s connection status, which is an extensive function works like reconnection when bearing a dropout.After functional configurations accomplished, immediately following the study of algorithm that parsing of data stream when transmitting and receiving. Actually, it is not in the true sense that TCP/IP transparent transmission mode which mentioned above. On account of the data-stream on the receiver is mixed up with instructions or notification information which needs to be eliminated in the way of parsing. In the process of data-stream parsing, all proceedures in programming are in accordance with the format-agreement of the AT instruction manual. Furthermore, multiple features and problems that have not been mentioned in the manual also are discovered, and the very treatments are given consequently. So far, the core content of DTU solution is completed.At the end of the paper, the basic software framework of DTU configuration and transmission programs in the actual application are given, along with a method of independent data transmission experiment. The entire research contents are realized by software programming, ultimately implemented as a wireless communication submodule for radar main program calling. The conclusions come out after several rounds of independent and joint tests. That is: as lack of flow control in the process, the TCP/IP transparent transmission may give rise to communication interruption when it is in a high rate, and that‘s difficult to detect in time. While the sustained data transfer rate is lower than half of the maximum rate of the serial port, the DTU solution couldachieve long-playing and stable wireless transmission. The probability of data transmission errors is about. This solution has achieved the expected target of the research project on the whole. Throughout the study, it integrates hardware features, software functions and practical applications closely, plays a favourable role in promoting the future DTU research in intelligent functions and system applications, which will be more feature-rich, robust and reliable.