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Orthogonal signal-division multiplexing (OSDM) is one of the generalized modulation schemes that bring the gap between orthogonal frequency division multiplexing (OFDM) and single carrier frequency domain equalization (SC-FDE). By performing encoding upon subvectors of each interleaved block, it enjoys a flexible resource management with low peakto- average power ratio (PAPR). Meanwhile, the OSDM induces the intervector interference (IVI) inherently, which requires a more powerful equalizer. By deriving the input and output system model, this paper proposes a time domain soft decision feedback equalizer (SDFE) on per vector equalization with successful soft interference cancellation (SSIC). In addition, this paper takes the whole OSDM block to perform the channel encoding rather than on each vector of the OSDM. Simulation and experimental results demonstrate that the proposed SDFE with SSIC structure outperforms the conventional minimum mean square error (MMSE) equalizer and the block encoding (BE) scheme outperforms the vector encoding (VE) scheme, because theoretically the longer the encoded bit stream is, the more stable and more confident the maximum a posteriori probability (MAP) decoder will be.
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This content will become publicly available on February 1, 2026
Orthogonal time-frequency space modulation for underwater mobile acoustic communications
This paper presents a new turbo decision feedback equalizer and decoder (TDFED) for the orthogonal time-frequency space (OTFS) system of underwater mobile acoustic communications where the communication channel suffers from severe multipath and Doppler effects simultaneously. The proposed TDFED employs a set of feedforward and feedback filters in the time domain instead of the common approach that employs a normalized least mean square equalizer in the delay-Doppler domain. The receiver also utilizes low-complexity improved proportionate normalized least mean square channel estimation in the delay-Doppler domain. Practical OTFS modulation schemes are designed for acoustic transmission at a center frequency of 115 kHz and a symbol rate of 11.5 ksps (kilo-symbols-per-second). Several lake experiments in mobile communication scenarios are conducted to evaluate the proposed OTFS in comparison to the single-carrier coherent modulation (SCCM) and the orthogonal frequency division modulation (OFDM) schemes. The experimental results demonstrate that the proposed OTFS receiver effectively reduces the accuracy requirements of the Doppler compensation algorithm compared to the SCCM and OFDM schemes. The proposed TDFED algorithm achieves a much better bit error rate against long-multipath fading and severe Doppler shift than the existing delay-Doppler domain equalizers.
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- PAR ID:
- 10641501
- Publisher / Repository:
- J. Acoustic Society of America
- Date Published:
- Journal Name:
- The Journal of the Acoustical Society of America
- Volume:
- 157
- Issue:
- 2
- ISSN:
- 0001-4966
- Page Range / eLocation ID:
- 1378 to 1390
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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