Jammer Blind Estimation of a Third-Party OFDM Channel

Novel, computationally simple and deterministic blind channel estimation schemes for PSK-OFDM and QAM-OFDM are proposed from legitimate transceivers as well as pilot-jammer's perspective. Their effectiveness in formulating the pilot-nulling attacks against OFDM is investigated. The estimators are based on the Least Squares (LS) principle and capitalize on the finite alphabet property of the information symbols. Phase ambiguity resolution requires no reference symbols while scalar ambiguity is resolved at the expense of a single pilot tone. The multipath characteristics of the channel between the target and the jammer are assumed to be Time Division Duplex (TDD) reciprocal. Simulation results are provided to demonstrate the performance of the proposed methods in channel estimation at the pilot locations as well as designing effective pilot-nulling attacks. The proposed methods estimate the jammer channel to the target perfectly to launch precise pilot-nulling attacks on OFDM in very low noise environment. The performance degrades with increasing noise.