OFDM demodulation using virtual time reversal processing in underwater acoustic communication
This addresses a specific problem in underwater acoustic communication by improving demodulation for time-invariant channels, representing an incremental advance over existing methods.
The paper tackles severe inter-symbol interference in underwater acoustic OFDM systems caused by long channel delay spreads by proposing virtual time reversal processing, which uses reversed estimated channels instead of probe signals to reduce interference, achieving outstanding performance in time-invariant channels as shown through simulations and pool experiments.
The extremely long underwater channel delay spread causes severe inter-symbol interference (ISI) for underwater acoustic communications. Passive time reversal processing (PTRP) can effectively reduce the channel time dispersion in a simple way via convolving the received packet with a time reversed probe signal. However the probe signal itself may introduce extra noise and interference (self-correlation of the probe signal). In this paper, we propose a virtual time reversal processing (VTRP) for single input single output (SISO) Orthogonal Frequency Division Multiplexing (OFDM) systems. It convolves the received packet with the reversed estimated channel, instead of the probe signal to reduce the interference. Two sparse channel estimation methods, matching pursuit (MP), and basis pursuit de-noising (BPDN), are adopted to estimate the channel impulse response (CIR). We compare the performance of VTRP with the PTRP and without any time reversal processing through MATLAB simulations and the pool experiments. The results reveal that VTRP has outstanding performance over time-invariant channels.