Adaptive turbo equalization method, equalizer and underwater acoustic communication system

Abstract

The invention relates to an adaptive turbo equalization method, an equalizer and an underwater acoustic communication system. The method comprises the following steps: calculating a primary symbol estimated value (the formula is as shown in the specification) according to a received symbol sequence r (i) and a priori symbol mean vector (the formula is as shown in the specification); calculating a symbol estimated value (the formula is as shown in the specification) fed back by a prior variance according to the primary symbol estimated value (the formula is as shown in the specification) and a prior symbol variance v (i); and calculating an output log likelihood ratio LLR of each symbol according to the symbol estimated value (the formula is as shown in the specification) fed back by the prior variance. The priori symbol information is mapped to obtain a priori symbol mean and a priori symbol variance. According to the adaptive turbo equalization method provided by the invention, the priori symbol information output by an SIOS decoder is better utilized, the communication performance under time-varying multipath is improved, and the signal to noise ratio threshold is reduced.

Description

technical field [0001] The invention relates to the field of underwater acoustic channel communication, in particular to an adaptive turbo equalization method, an equalizer and an underwater acoustic communication system. Background technique [0002] The multipath effect of underwater acoustic channel causes intersymbol interference, which seriously affects the performance of underwater acoustic communication. Generally, an equalizer is used in the receiver to eliminate intersymbol interference. Equalization uses the idea of ​​iterative equalization, and the external information is transmitted to the equalizer through the decoder, which is used as the prior information of the equalizer to make the equalization result more reliable. [0003] The iterative processing of error correction decoding and equalization is performed by using turbo equalization, and the soft information of the information bit sequence is iterated multiple times between the soft-input soft-output (SISO...

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Problems solved by technology

[0004] However, due to the fluctuation of the water surface, the disturbance of the water body and the movement of the communication device, the channel impulse response of the underwater acoustic channel is unknown and time-varying. The existing practical turbo equalization method is an adaptive turbo equalization method. The tap coefficient of the SISO equalizer Obtained by the direct adaptive algorithm, the tap coefficient changes very little between adjacent symbols, thus ignoring the time-varying nature of the prior symbol variance sequence, resulting in the deterioration of turbo equalization performance

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