  Pilot contamination attack is an important kind of active eavesdropping
activity conducted by a malicious user during channel training phase. In this
paper, motivated by the fact that frequency asynchronism could introduce
divergence of the transmitted pilot signals between intended user and attacker,
we propose a new uncoordinated frequency shift (UFS) scheme for detection of
pilot contamination attack in multiple antenna system. An attack detection
algorithm is further developed based on source enumeration method. Both the
asymptotic detection performance analysis and numerical results are provided to
verify the proposed studies. The results demonstrate that the proposed UFS
scheme can achieve comparable detection performance as the existing
superimposed random sequence based scheme, without sacrifice of legitimate
channel estimation performance.
