Research On Security Transmission Mechanism Of Space Hopping Communication Based On Time Reversal

With the rapid development of wireless communication technology,the security of wireless communication information transmission is increasingly demanded.In the wireless signal transmission process,the reflection and refraction of electromagnetic waves makes wireless channel have unique airspace characteristics,which provides a research basis for solving some wireless communication security problems at the physical layer.Time reversal technology can collect the signal energy scattered on every multipath,and then make the multipath signals coherently added at the target receiver,so as to achieve the temporal and spatial focusing of the signal.Space hopping communication technology uses the spatial uncertainty of the transmission channels generated by the airspace channels switching,which can keep the key of the encrypted information constantly changing,and this will realize the security of information transmission.Therefore,combining the above two technologies can not only make full use of multipath in the wireless environment,but also help ensure the security of information transmission.Based on these,the main work of this thesis are as follows:Firstly,aiming at the problem of eavesdropper using blind estimation algorithm to eavesdrop information,a secure transmission scheme combined time reversal with space hopping communication is proposed.In this scheme,the time reversal technology,which has the spatial and temporal focusing characteristics,is used in the classic wiretap channel model to reduce the risk of information eavesdropped.Then,using the spatial uncertainty of space hopping communication,the artificial noise and space hopping communication is combined to change the null space of artificial noise constantly,which makes it more difficult for the eavesdropper to eavesdrop information.Theoretical analysis and simulation results show that this scheme can increase the secrecy-signal to interference plus noise ratio of the system and the bit error rate of the eavesdropper,and reduce the probability that the eavesdropper can successfully eavesdrop confidential information by using blind estimation algorithm.Secondly,for the case of how to select the space hopping pattern in time reversal combined with space hopping communication system,which aims at reducing the impact of channel estimation error at the transmitting end on system performance,a multi-armed bandit algorithm generating space hopping pattern is proposed.First,thisalgorithm based on the time reversal technology uses the multi-armed bandit algorithm to optimize the generation process of the space hopping pattern.Second,utilizing the spatial and temporal focusing characteristics of time reversal,combining with symmetric encryption and space hopping communication technology,it can increase the difficulty for eavesdropper to crack confidential information without affecting legitimate receiver.Theoretical analysis and simulation results show that this algorithm can not only effectively reduce the impact of channel estimation error on system capacity,but also reduce the interference with legitimate receiver during anti-eavesdropping.