Study And Simulation Of Air-ground Data Link Protocol

The ground-to-air data transmission technology is first used in the civil aviation, but at present, as one kind of ground-to-air Data Link, it is more and more used in military. In this paper, a data link based on the ground-to-air data transmission is studied. The main characteristic of the Data Link is that the information transmits and exchanges in the stipulated form, in encryption and in real-time automatically. Thus the information resource sharing is realized, and the mutual coordination ability and the whole transmission potency are maximized.According to the methods of the wireless networking and some basic network models, based on the research of the general wireless communications, networks and Data Link, a new ground-to-air data transmission protocol is proposed in this paper, with the detailed overall project design, including system design principle, system design diagram, system performance, function module design and flow design. The transmission models of the physical layer, the data link layer, the network layer, the transmission layer and the application layer are also proposed based on the research of the structure and function of the network system.In view of the special characteristics of the Data Link network, the capacities, the advantages and disadvantages of the commonly used multiple access methods are analyzed to propose the multiple access and allocation methods suitable for the Data Link used in the tactical communication. A dynamic time slot assignment strategy -- polling protocol, is also studied. In the point-to-point mode, these all may enhance the channel transmission efficiency.In the paper, the key technologies used in the system elaborated, such as the time slot division and the network address allocation, a number issues of the traditional TCP protocol in wireless transmission environment are discussed, some measures in the physical layer and the transmission layer are proposed to improve the wireless link usage. Also the error control algorithm of the link layer is studied.Finally the network topology is established in OPNET, with the relatively standardized level node model to complete the flow-based simulation so that the performance index could be obtained and the accuracy, the validity and the fault tolerance of the protocol could be comprehensively verified. According to the simulation results, the data link protocol proposed in the paper has implemented the basic features of the air-to-ground data transmission and reached satisifiable effect in the simulation scenes.