 MCJT scheme, respectively. In the experiment, ignoring preamble and CP overhead, the data rate of mirror-mapping-based schemes and OFDM-B is 4.27 kbps. For time synchronization, the received signal is correlated with the preamble and the postamble to obtain the starting and ending time of the received data frame. Then, the resampling factor is calculated by comparing the received signal length and the transmitted signal length. Finally, to remove the major Doppler effect, the received signal is resampled according to the resampling factor [16]. The CFR of each subcarrier can be estimated via the received signals on the pilot sub- carriers. The CFRs on the pilot subcarriers are estimated first. Then the CFRs on the data subcarriers can be obtained through the piecewise cubic spline interpolation. To combat the time-varying feature of UWA channels, channel estimation is done for each OFDM symbol. 1.5.2 Experiment Results To obtain the BER results and enable a fair comparison of different schemes, the packages with indices "M0000043.DAT," "M0000044.DAT," "M0000046.DAT," "M0000047.DAT," "M0000049.DAT," "M0000050.DAT," "M0000052.DAT," and "M0000053.DAT" are uti- lized with their information provided in Table 1.2. They are transmitted consecutively with similar receive SNR levels and through the same transmitter-receiver (T-R) pair. Figure 1.14 illustrates the BER performance of OFDM-B, the mirror-mapping-based ICI cancellation schemes, and the plain OFDM with QPSK modulation (OFDM-Q). The BER of OFDM-Q is calculated by directly decoding the mirror-mapping-based schemes without combining data subcarrier pairs, and thus ICI is not suppressed. As expected, all mirror-mapping-based schemes have lower BER than OFDM-B and OFDM-Q for all hydrophones. This confirms that mirror-mapping-based schemes can achieve superior ICI mitigation in OFDM UWA communications. Unlike with the CIR results, it is observed that all four schemes have similar BER performance. This is not surprising since the CIR performance is not directly relat