{'fraction_non_alphanumeric': 0.017699115044247787, 'fraction_numerical': 0.0, 'mean_word_length': 5.711864406779661, '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}}
Multiband FSK with Direct Sequence Spread Spectrum for Underwater Acoustic Communications

This paper presented an efficient multiband FSK signals with direct sequence spread spectrum for maintaining covertness and performance. In aspect to covertness, direct sequence spread spectrum method, which multiplying by PN codes whose rate is much higher than that of data sequence, is employed. In aspect to performance, we applied multiband, turbo equalization, and weighting algorithm. Underwater acoustic communication experiments were conducted in the lake. In the lake experimental results, we confirmed that the performance was improved as the number of bands and chips are increased. Furthermore, the performance of multiband was improved when the proposed weighting algorithm was applied.