Remote underwater sound communication method

Abstract

The invention aims to provide a remote underwater sound communication method and belongs to the technical field of underwater sound communication. The method is based on demodulation and decoding combined iterative detection of differential encoding. A transmitter resists multi-path interference by using spread spectrum communication, the problem of phase jump and loop cycle skipping is solved by using differential modulation quadrature differential phase shift keying with high frequency spectrum utilization rate, and the transmitter adopts demodulation and decoding combined iterative technology to eliminate inter-code interference. The method has the beneficial effects that 1) the error bit rate performance of a remote underwater sound communication system is improved by the demodulation and decoding combined iterative technology; 2) the technical requirement on a non-linear amplifier is reduced by differential modulation, and differential modulation has engineering feasibility; and 3) the multi-path interference of a remote underwater sound channel is overcome by spread spectrum communication.

Description

Technical field: [0001] The invention relates to a remote underwater acoustic communication method, which is based on differential coding, demodulation, decoding, joint iterative detection, and belongs to the field of underwater acoustic communication. Background technique: [0002] In long-distance underwater acoustic communication systems, inter-symbol interference directly affects the reliability of communication results. The multipath interference of the remote underwater acoustic channel is serious. In order to improve the communication reliability, the anti-interference ability must be improved. It is an effective means to demodulate, decode and iteratively process the signal. [0003] At present, the long-distance underwater acoustic communication system at home and abroad widely adopts the combined iterative processing of demodulation and decoding. The disadvantages of underwater acoustic communication are: due to the frequency difference between the carrier frequen...

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Problems solved by technology

[0003] At present, the long-distance underwater acoustic communication system at home and abroad widely adopts the combined iterative processing of demodulation and decoding. The disadvantages of underwater acoustic communication are: due to the frequency difference between the carrier frequency at the two ends of the transceiver, and the relative movement of the two ends of the transceiver, Doppler frequency shift occurs, resulting in phase ambiguity of the received signal. very sensitive

[0004] In the article "Bit-interleaved Coded Modulation with Iterative Decoding and 8PSK Signaling" in 2002, the joint iterative technology of 8PSK modulation and convolutional code decoding was proposed. The method is to use ideal interleaving to reduce the correlation of bits in the received symbols, and use convolutional codes The probability information fed back by the decoder reduces the ambiguity of 8PSK demodulation, and the probability information output by the 8PSK demodulator is used to reduce the bit error rate. The disadvantage of using it in long-distance underwater acoustic communication is: due to the The noise generated by fluctuations is a common burst noise, and the ability of convolutional codes and RS codes to correct random errors is very good, but the ability to correct burst errors in underwater acoustic channels is not good, so there is still a high bit error rate after decoding

[0005] In 2010, Xue Rui proposed the combined iterative technology of continuous phase modulation (CPM) demodulation and LDPC decoding in the article "LDPCC-CPM System Receiver Design Based on Turbo Iterative Algorithm". The demodulator and LDPC decoder constitute a soft-input and soft-output module. The disadvantages of using it in long-distance underwater acoustic communication are: the underwater acoustic channel is a frequency selective fading channel, and the intersymbol interference is serious. Lattice equalization is an effective means to eliminate intersymbol interference in the LDPCC-CPM system, but its complexity increases exponentially with the number of states in the hypergrid, and it is difficult to realize it in real time and apply it in engineering practice.

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