Study On Pilot Spoofing Attack Detection And Countermeasure In Massive MIMO Systems

Massive multiple-input multiple-output technology,as one of the key technologies of 5G,can significantly improve the throughput of the system.However,massive MIMO systems are vulnerable to pilot spoofing attack(PSA).Especially in a time division duplexing(TDD)system,due to the reciprocity between the uplink and downlink,if the eavesdropper launches the PSA during the uplink training phase,the channel estimation result of the legitimate user will be contaminated by eavesdropping links,leading to changes in the precoding used in the downlink transmission phase.Eventually,the received signal at the eavesdropper will be enhanced during downlink transmission,and the signal quality at the legal user will be reduced.In order to ensure the security of the legal communication of the massive MIMO system,from the perspective of PSA detection and countermeasure,the following work is mainly carried out:(1)Since PSA will change the channel estimation results of legitimate users,this paper proposes a PSA detection method based on channel estimation.Specifically,based on the likelihood ratio test(LRT)principle,three PSA detectors are proposed utilizing least squares(LS)channel estimation.It is worth mentioning that the detection only needs to know the channel statistics and noise variance of legitimate users.In addition,performance analysis on the probability of detection was also conducted,especially the impact of key parameters on it.(2)Considering that the obtaining of legitimate users' channel statistics at the base station under PSA also become unreliable,this paper proposes a PSA detection method based on the retransmission,and the detection is carried out at each user after retransmission.The retransmission is divided into two steps.The first step can obtain an estimate of the channel statistics of the legitimate user,and the second step is used to construct the decision metric.For the detection of each user,only the noise variance is necessary.It is worth mentioning that although the detection process is more complicated,the detection performance is more excellent.(3)Considering the countermeasure of PSA in massive MIMO system,this paper also proposes a PSA detection and countermeasure method based on pilot manipulation to realize the simultaneous PSA detection and PSA countermeasure.The execution of the detection is put back to the base station,and it is necessary to know the channel statistics and noise variance of the legitimate user.Specifically,legitimate users randomly divide the pilot sequence into two parts,the first part remains unchanged,and the second part is multiplied by a diagonal matrix.Although eavesdroppers may employ the same way to send pilots,it is easier to expose themselves.The decision metric is also obtained based on the LRT principle,but the new decision metric no longer contains the part related to the legitimate channel,which has been proven to effectively improve the detection performance.Besides,the possibility of performance enhancement by joint detection is discussed.Finally,based on the pilot manipulation,the eavesdropping link part in the channel estimation result is eliminated,and the PSA countermeasure is realized.