Anti-Jamming Technologies Of Cognitive Radio Communication In The ISM Band

With the development of wireless communication technology,the problem of scarcity of spectrum resources is becoming more and more serious.Communications on unlicensed bands also become crowded.The application of cognitive radio technology can effectively improve the utilization of spectrum resources.The ISM band which belongs to unlicensed bands can be used without an application,it mainly includes the 2.4 GHz band and the 5 GHz band.The typical communication equipments in ISM band are bluetooth,ZigBee and WiFi devices,among which WiFi devices are the most widely used,thus WiFi signal is considered as the main interference in this thesis.The anti-jamming technologis of the ISM band proposed in this thesis can be used in the interference suppression in the communications,which can improve the communication environment and provide better communication quality.The main work are as follows:1.The space-time joint anti-jamming technology is analyzed and simulated,and the space-time joint signal model is established.Under the consideration that the computational process will bring great complexity,researches for a variety of dimensionality reduction methods and adaptive filtering principles of space-time joint signal are performed.Through the simulation experiments with Matlab,ICSA-MWF method,which has the best performance at present,is capable of restraining the interference,and at the same time,it has a relatively low complexity in the calculation process.Besides,wideband and narrowband interferences can be effectively reduced.2.Suppression methods for WiFi signal are proposed.Based on the 802.11 protocol,the methods under virtual carrier sensing principle and physical carrier sensing principle are raised.The method under virtual carrier sensing principle refers to periodically sending a WiFi suppression signal frame on a communication channel to notify the WiFi devices to perform a corresponding back-off.The method under physical carrier sensing principle refers to using energy detection function of WiFi devices,by sending signals on the overlapping channels continuously,WiFi devices on the target channels will perform back-off.3.Interference suppression model of WiFi signal of ISM band is established,which represents the propagation of WiFi signal.Simulations are perfomed with Matlab especially for the interference power before and after suppression.Suppression effect of WiFi devices is simulated and comparisons are made for the interference power before and after suppression.