Research On Random Access Technology Of Data Link

The existing data link network has many shortcomings in the complex electromagnetic environment. On the one hand, the existing data link MAC protocol cannot change the channel in time according to the surrounding environment when the working channel is completely blocked, which easily leads to communication interruption, network delay, the increasing number of data retransmission etc. On the other hand, mobile terminals can't find the data link network to access the network flexibly and fast because of the high speed of mobile terminal and the dramatic changes in network topology. Currently, widely used data links include link11 and link16, which have fixed spectrum access mode, poor ability of anti-disturbance, and low transmission rate. Therefore, mobile terminals cannot be quickly deployed, dynamically routed, flexibly joined in and quitted the network aiming at the specific operational tasks.In view of the above problems, cognitive radio provides an effective way to solve the problem. Cognitive radio technology can identify and judge the current network environment, search the data link network and the available frequency point dynamically, adjust the working parameters(such as modulation mode, transmission power and antenna pattern) automatically. Therefore, mobile terminals can be accessed into the data link network flexibly to choose spare frequency point for reliable communication, which can solve the problem of unreliable communication, frequent network interruption, dramatic changes of topology, and dynamic processes of joining in and quitting network effectively in battlefield environment, enhancing the flexibility and ability to resist interference of data link communication. Moreover, mobile terminals are required to move between different types of data link network to perform the corresponding operational tasks because of the difference of the coverage, communication ability and technology system among data link networks in battlefield environment. Consequently, the application of cognitive radio technology makes mobile terminals have the ability to access into a variety of different data link network.According to cognitive radio, Link11 and Link16 system, we propose random access technology based on spectrum sensing, whose innovation is anti-interference mechanism and random access mechanism in single transceiver mode which can satisfy different mission requirements. The thesis illustrates polling network, TDMA network, and random access mechanism in detail, especially focusing on slot structure, spectrum sensing, data transmission, channel switching, processes of joining in and quitting network etc. In addition, simulation study of polling network, TDMA network and random access mechanism is made to the scheme with the OPNET simulation software. We analyze the feasibility and performance of the mentioned MAC protocol and random access mechanism.