{'fraction_non_alphanumeric': 0.023065476190476192, 'fraction_numerical': 0.0, 'mean_word_length': 5.529126213592233, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Performance of DSTTD-OFDM system in underwater communications

In this letter, we investigate the symbol error rate(SER) performance of multi-carrier (MC) double space-time transmit diversity (DSTTD) system for the transmission of acoustic signals in underwater communication. In our work, we consider the problems of mitigating the effects of multipath propagation, acoustic interference and ambient noise in underwater communications. We realize DSTTD architecture at the transmitter side and non-linear multi-user detection based on Space-Time Block nulling technique in order to alleviate the effects of acoustic interference and ambient noise. Further, we implement multi-carrier modulation using IFFT block at the transmitter and FFT block at the receiver to mitigate the effects of multi-path propagations. In particular, we investigate the effects of eleven tap delay pertaining to shallow water channel model for our considered DSTTD-OFDM system. Our simulation results reveal that DSTTD-OFDM system with Block-Nulling detection technique provides better SER with less signal-to-noise ratio by alleviating the effects of acoustic interference and ambient noise. Further we observe that our considered system achieve higher throughput with less number of computations at the receivers by mitigating the effects of multipath propagation.