Research On Intrinsic Security Transmission Technology For Massive MIMO

With the popularization of intelligent terminals and the popularization of the Internet of things,wireless communication has gradually penetrated into every corner of modern society."Information follows,everything connects" becomes the good vision of the next generation mobile communication network(5G).Massive MIMO technology is considered to be the key technology of 5G because of its unprecedented spectrum utilization and energy efficiency.It is expected to be applied to many new scenes,such as heterogeneous networks,millimeter wave networks,car networking and so on.At the same time,massive MIMO technology has the ability to resist the potential eavesdropper in the system.Although large-scale MIMO has intrinsic security to wireless communication systems,but the current research on this security is very inadequate,which causes two problems.First,the current physical layer security technology takes power for security,failure to make full use of the internal security of massive MIMO,causing serious waste of resources,and the security algorithms designed without considering the endogenous security of massive MIMO are not necessarily in perfect agreement with the system.Second,the current study doesn't establish a link between theoretical indicators and measurable indicators,and cannot evaluate the actual safety performance of the communication system.To solve the above problems,this paper starts with the structural characteristics of massive MIMO,analyzes the natural security factors caused by the multi-antenna gain and the multi-user gain respectively.Afterwards,from the perspective of physical layer security,based on the intrinsic security of the system,using techniques such as beam-forming,artificial noise,and user collaboration,an adaptive security transmission algorithm is proposed for situations in which the intrinsic security capabilities of the system are insufficient,and verifies the proposed algorithm on the actual 32 antennas communication platform.The specific research content and conclusions of this article are as follows:1.We study the natural security gains of the multi-user downlink signals,and the multi-user adaptive security transmission algorithm is proposed.Based on stochastic geometry theory,a massive MIMO physical layer security system model with multi-user and multi-eavesdropper is built.The effect of multi-user downlink concurrency on the eavesdropper on the same time frequency resource block under the condition of space division multiple access is considered.The intrinsic security performance of the system is analyzed,and an adaptive security transmission algorithm is proposed for the case that the security of system is weak.When the number of access users is small,a beam scrambling strategy is proposed.When the number of access users is large,a location-based user scheduling strategy is proposed,and on the basis of utilizing intrinsic security of the system,the security rate and the security energy efficiency of the system are further improved.Simulation analysis shows that multi-user signals bring high security gain to the system.The proposed strategy can ensure the secure communication when the system's intrinsic security capability is insufficient.2.We study the natural security gain brought by 2D beam focusing of 3D-MIMO,and the directional scrambling algorithm based on security threat region is proposed.In particular,first,according to the mechanism of the physical layer security is based on the user's location,the concept of the security threat zone is proposed.After that,taking 3D-MIMO as an example,we analyze the security threat capabilities of the system when the eavesdropper is located everywhere,and the influence of system parameters on the security threat area is deduced.Finally,the scrambling is concentrated in the area to improve system security.Simulation analysis shows that 3D-MIMO can achieve user-location-based security by using beam focusing.The proposed strategy can further reduce the security threat area and reduce the eavesdropping ability of illegal users in where non-user is located.3.The relationship between the bit error rate of the measurable indicator and the safety distance is established,and the physical layer security algorithm and experimental test method are designed to verify the beam scrambling and security threat area.In particular,in the traditional LTE communication process,the maximum ratio combining pre-coding and the matrix scrambling physical layer security coding are added in the coding modulation stage,and the space scrambling algorithm is added before the digital-to-analog conversion to create a signal-to-noise ratio advantage for legitimate user,deteriorate the eavesdropping channel at the same time.The experiment of rich scattering environment is carried out indoors and the effectiveness of N-beam scrambling strategy in chapter 3 is verified.And the safety distance test experiment is conducted outdoors to verify the correctness of the theory of the safe threat region in chapter 4.Experimental results show that the use of physical layer security technology can achieve security based on user's location,and the proposed algorithm and experimental testing method have high engineering reference value.