Research On Physical Layer Security Communication Method Based On Adaptive Technology

Security problem is becoming a great challenge to the wireless communication networks which facilitated people daily life.Encryption technology is a traditional method that can effectively improve the security of communication systems,but with the advent of supercomputers and the development of quantum computing technology,the security of encryption which is proved to be broken in theory is gradually reduced.Meanwhile,the physical layer security technology that uses the randomness of the wireless channel to realize the information "absolute security" is widely concerned recently because it can be used with the upper encryption method as a complement.The research on theoretical limit of the secrecy transmission rate is the fundamental problem in the physical layer security field,and how to approach the limit is the current research hotspot.Adaptive secrecy technology is one of the methods that can effectively improve the secrecy throughput over the fading wireless channel.However,the existing adaptive methods are based on the ideal physical layer technology in the "perfect secrecy" theory system whose results do not reflect the confidentiality of real communication systems.So this paper studies the security performance of the actual coded modulation communication system that adopt adaptive method.The main work is as follows:1.A simple and feasible semi-adaptive transmission method is proposed to solve the problem that classical adaptive secure transmission methods cannot be applied to real system.The method realize the optimization of the security performance under the constraint of communication performance by adjusting the transmission rate and the transmission power according to the finite code length coding method and the discrete constellation size modulation method,which is widely used in the commercial communication system,and only 1 bit of channel feedback information is needed to achieve adaptive coding modulation.So this method not only has high application value but also with a low complexity.The simulation results show that the performance of the proposed method is lower than that of the S-ADP method since the constraint of BER,but it is a reflection of the security performance in the real communication system.And the performance can be improved by adopting different transmission schemes.So the proposed method is a low-cost adaptive secure transmission scheme for applications where security performance is not high.2.A discrete semi-adaptive transmission method based on the "local secrecy"theory system is proposed to solve the problem that the semi-adaptive method of the fixed transmission scheme has a low safety performance.The fading channel is divided into a numbers of adjacent but non-overlapping fading sub-regions and each fading sub-regions has a fixed coding modulation transmission scheme,it is succeed in converting the adaptive design in the fading channel into a combined semi-adaptive design problem for multiple fading subfields.Although the method is more complex than simple semi-adaptive transmission method because complete and real-time channel state information is need to feedback to the transmitter,the improvement in performance can be seen obviously since the transmission rate is freer.The simulation results show that compared with the simple semi-adaptive transmission method,this method is more superior,and more than 1dB improvement of secrecy throughput can be achieved at low transmit power.With the security outage probability increasing,the amplitude of the enhancement is further expanded.And the better performance than S-ADP method can be obtained under the condition of loose security outage probability.