Spectrum Sensing-Based Dynamic TDMA Network Access Scheme

With the rising status of modern information technology in the military war, the control of spectrum resources has a significant impact on the communication quality of the battlefield to some extent. Fortunately, the hot wireless technology, cognitive radio, has supplied an effective way to make good use of the spectrum sources, and it has also gradually penetrated into military applications in recent years. However, the multiple access protocols in existed data link network are simplex and fixed. If the enemy beams malicious and powerful jamming, they cannot make timely and flexible channel switches according to the surrounding electromagnetic environment, which leads to some bad consequences such as communication outage, message delay, large fluctuation of end to end delay etc. Aided by the cognitive radio technology, this thesis aims to enable the data link system to sense the environment and strengthen anti-jamming capability of the network in order to ensure stability and reliability of battlefield communications momently.On the basis of TDMA protocol of Link-16 data link, this thesis designs a novel dynamic TDMA protocol with spectrum detection technology and MAC layer sensing strategy to tackle issues such as the battlefield electromagnetic environment variation, the lack of spectrum resource, the imbalanced network load etc. Firstly, the designed spectrum sensing algorithm in the physical layer deals with collected data from the battlefield electromagnetic environment and makes accurate judgments on the current channel state, based on which a reliable ground of decision to switch channels can be provided. Secondly, the sensing strategy in the MAC layer focuses on details upon the mode and duration of sensing. It aims to reduce the extra overhead cost by spectrum sensing and find out the idle and available channel efficiently. Minimizing the impact on network traffic performance is also expected as one goal. Thirdly, this thesis designs a dynamic slot allocation algorithm, which can avoid spectrum waste in the TDMA protocol of the Link-16 data link, meet the demand of military communications, and effectively improve spectrum utilization and network throughput in presence of imbalanced load. And its aim is to provide good tolerance for different source traffic conditions.According to the above, this thesis first introduces the key technology of Link-16, after which a spectrum sensing-based dynamic access protocol of the TDMA network is designed, including the slot structure of the designed dynamic TDMA network, the spectrum sensing strategy, the flexible dynamic slot allocation algorithm, and the random access mechanism. In addition, the theoretical analysis of the scheme is given in detail. At last, network simulations on the platform of OPNET Modeler are conducted to evaluate the spectrum sensing-based dynamic TDMA network. Both analytical and simulation results have verified the correctness, validity and performance breakthrough of our scheme.