Arjun Thottappilly and A.A. (Louis) Beex
Acoustic Communication, Wideband Doppler Correction, Time Warp, Orthogonal Frequency Division Multiplexing
A time warp based technique is introduced and analyzed for the modeling of time-varying wideband Doppler effects, such as may be observed in an underwater acoustic (UWA) channel. A corresponding procedure for the estimation of the parameters required for inverting the effect of the time warp, based on observed data, is proposed also. The proposed method is compared to the existing uniform resampling based Doppler correction technique which corrects for the average Doppler-caused expansion or contraction over the correction interval by restoration of the length of the received signal. The time warp based method is demonstrated using Orthogonal Frequency Division Multiplexing (OFDM) signals, but will in principle work for other kinds of wideband signals as well. The presented results – obtained from an over-the-air proxy experiment, performed in such a way as to introduce a time-varying Doppler effect in the received signals – illustrate the improvements that can be obtained by using the proposed time warp based Doppler modeling and correction method.
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