  In this paper, we investigate the carrier frequency offset (CFO)
identifiability problem in orthogonal chirp division multiplexing (OCDM)
systems. We propose a transmission scheme by inserting consecutive null
subchirps. A CFO estimator is accordingly developed to achieve a full
acquisition range.
  We further demonstrate that the proposed transmission scheme not only help to
resolve CFO identifiability issues but also enable multipath diversity for OCDM
systems. Simulation results corroborate our theoretical findings.
