Remote underwater acoustic communication method based on soft-demodulation soft-decoding joint iteration

Abstract

The invention provides a remote underwater acoustic communication method based on soft-demodulation soft-decoding joint iteration. The method comprises the following steps that: a transmitting end performs low density parity check (LDPC) coding on a binary information sequence which is sent by a signal source, performs quaternary phase shift keying (QPSK) modulation and Gray mapping, maps code elements to one of four positions in a constellation diagram by taking two code elements as a group, performs Walsh-m composite sequence spectrum spreading to obtain a signal to be transmitted, and converts a digital signal to be transmitted into an underwater acoustic signal; and an underwater acoustic transducer at a receiving end converts the received underwater acoustic signal, de-spreads by using a composite sequence which is the same as that of the transmitting end to obtain a receiving signal, performs self-adaptation decision feedback equalization to obtain an amplitude fading complex signal, performs soft-demodulation soft-decoding joint iteration on the signal, stops joint iteration after set iteration frequency is reached, performs belief propagation (BP) decoding on an LDPC decoder and outputs a bit value to a sink. By the method provided by the invention, the reliability of remote underwater acoustic communication is improved. The method is applicable to the remote underwater acoustic communication.

Description

technical field [0001] The invention relates to an underwater acoustic communication method. In particular, a long-range underwater acoustic communication method. Background technique [0002] In long-distance underwater acoustic communication systems, the signal-to-noise ratio of received signals directly affects the reliability of communication results. Multi-path extension delay and amplitude attenuation both increase with the increase of communication distance. In order to improve communication reliability, the signal-to-noise ratio of the received signal must be improved. Anti-multi-path interference processing on the signal is an effective method. [0003] At present, anti-multipath processing is widely used in long-distance underwater acoustic communication systems at home and abroad. The method is OFDM (Orthogonal Frequency Division Multiplexing) technology. A large communication distance requires an increase in the transmission power, so the requirements for the l...

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Problems solved by technology

[0003] At present, anti-multipath processing is widely used in long-distance underwater acoustic communication systems at home and abroad. The method is OFDM (Orthogonal Frequency Division Multiplexing) technology. A large communication distance requires an increase in the transmission power, so the requirements for the linear amplification range of the underwater acoustic transducer are very strict

[0004] In 1998, in the article "Spread Spectrum Underwater Acoustic Telemetry", M.Stojanovic proposed the multipath diversity reception technology based on the Rake receiver. The method is: after the Rake receiver compensates the multipath effect of the channel, it highlights the main path components in the signal. Improve the signal-to-noise ratio of the direct sound, so that the impulse response function of the channel approaches the σ function

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