Recent investigations have revealed the susceptibility of phasor measurement units (PMUs) to the time synchronization attack by spoofing its global positioning system (GPS). This paper proposes a cross-layer detection mechanism to fight against simul- taneous attacks toward multiple PMUs. In the physical layer, we propose a GPS carrier-to-noise ratio (C/No) based spoofing detec- tion technique. We apply the patch-monopole hybrid antenna to two GPS receivers and compute the difference between the stan- dard deviation of each receiver’s C/No. The priori probability of spoofing is calculated from the distributions of the difference. A counter is embedded in the physical layer to identify the most suspicious PMU. In the upper layer, the spoofing attack is consid- ered similarly to the bad data injection toward the power system. A trustworthiness evaluation, which is based on both the phys- ical layer information and power grid measurements, is applied to identify the PMU being attacked. An experiment has been carried to validate the proposed algorithm.
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