Wen Xu
ABSTRACT
Underwater acoustic channels, which exhibit dispersion both in time and frequency, are referred to as doubly spread channels. The newest time reversal (TR) receivers applied on those channels are based on the sparse spreading function estimation to compensate both delays and Doppler shifts for individual paths. In this paper, a new cross-ambiguity function (CAF) based approach is developed to handle the doubly spread channels. The proposed method identifies the spreading function by computing the CAF, and selects the delay and Doppler factors for each individual path sequentially. Unlike existing approaches of sparse channel estimation, the approach here determines the number of paths simply by thresholding CAF based on the noise power, thus no need to estimate the channel sparsity level; moreover, it has lower computational complexity and less memory requirement to support frequent channel update. Simulation results validate the effectiveness of the proposed approach. Using experimental data collected in shallow water with a mobile transmitter, processing results show a robust performance of the proposed TR receiver combined with block processing against rapid channel fluctuations.
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Index Terms
- A New Approach for Time Reversal Communication over Doubly Spread Channels
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