| With the wide application of MIMO technology in wireless communication, there havebeen extensive studies on MIMO system physical layer secure transmission. The technology ofphysical layer secure transmission takes the advantage of the variety and time-variant charactersof wireless channels, along with the uniqueness and exchangeability of bilateral channels. Themain problems of current MIMO system physical layer secure transmission are summarized asbelow.1) While lacking of nullspace redundancy, the existing artificial-noise-based algorithm forphysical layer transmission, could introduce lots of noise into legitimate users and impair theirnormal reception.2) Eavesdroppers might be able to steal more information from the weakchannel users, impacting the entire system’s safety performance.3) Under the condition ofpartial CSI, there could be estimation errors in the safety performance evaluation, and theleaking noise could affect legitimate users’ reception.To begin with, this paper defined an MIMO system physical layer secure transmissionmodel. Then based on this model, to solve the first main problem stated above, two algorithmswere explored for non-nullspace-redundancy MIMO system secure transmission. Secondly, toaddress the second main problem as mentioned above, two algorithms based on jointinterferences were provided for MIMO system secure transmission. Thirdly, in response to thethird main problem raised in last paragraph, a safety mechanism for MIMO system under partialCSI was developed. The chief detailed content of this article is followed.1) Proposed two algorithms for non-nullspace-redundancy MIMO system securetransmissionProposed a secure transmission algorithm based on joint channels state matrix. To achievethis, establish a joint channel state matrix first, then do singular value decomposition, and lastlyprecode to suppress artificial noise. The simulation analysis showed that when the multi-userMIMO system had no nullspace redundancy, the algorithm could increase the system secrecycapacity by0.1bit/s/Hz on average.In addition, proposed a physical layer secure transmission algorithm based on multiplicativenoise. This algorithm doesn’t apply any extra artificial noise, but randomly changes precode fastand meanwhile keeps the randomly changing elements transparent to legitimate users,equivalently resulting in adding multiplicative noise to eavesdroppers. The simulation analysisshowed that when the multi-user MIMO system had no nullspace redundancy, the algorithmcould increase the system secrecy capacity by0.15bit/s/Hz on average.2) Proposed two algorithms based on joint interferences for MIMO system securetransmissionProposed an algorithm based on multi-user joint interference. Accordingly, three solutionsincluding Max SINR, Max SF and PFBS, were developed to meet users’ different security needsand to impose joint interference onto eavesdroppers. The simulation showed that the algorithmcould enhance the system secrecy capacity by2.4bit/s/Hz at maximum.Also, proposed an algorithm based on multi-base station interference, in which adjacent bases could dispatch flexibly uplink and downlink transmissions to undermine eavesdroppers.The simulation showed that the secure transmission rate could reach the upper limit when thebase sent out Gaussian noises.3) Developed a safety mechanism for MIMO system under partial CSIProposed a joint power allocation algorithm. This algorithm reduces the estimation errors insafety performance through adjusting artificial noise power distribution ratio. The simulationanalysis showed that the algorithm could improve the MIMO system secrecy capacity by1.5bit/s/Hz under partial CSI.Then lastly, proposed a beamforming adjustment algorithm. The algorithm applysprewhitening interference and noise, and re-designs the sending and receiving terminalsbeamforming according to the equivalent channels, so as to improve legitimate users’ receivingperformance. The simulation showed that the algorithm could raise the SINR by12dB forMIMO system legitimate users under partial CSI. |
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