Consistent blind synchronization of OFDM transmissions using null sub-carriers with distinct spacings

The ability of orthogonal frequency division multiplexing systems to mitigate frequency-selective channels is impaired by the presence of carrier frequency offsets (CFO). We investigate identifiability issues involving high-resolution techniques that have been proposed for blind CFO estimation based on null subcarriers. We also propose new approaches that do not suffer from the lack of identifiability problems and channel-dependent performance.