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Mixed Carrier Method for Underwater Communication Based on Weighted Fractional Fourier Transform

A fractional-order Fourier and underwater communication technology, which is applied to multi-carrier systems, baseband system components, electrical components, etc., to achieve the effects of improved applicability, low system bit error rate, and good performance

Active Publication Date: 2019-02-22
XIAMEN UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] It can be seen that the two modulation systems, OFDM and SC-FDE, have their own advantages and disadvantages, and there is complementarity in transmission performance, which is also the root cause of the coexistence of the two systems in the current actual system.

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  • Mixed Carrier Method for Underwater Communication Based on Weighted Fractional Fourier Transform
  • Mixed Carrier Method for Underwater Communication Based on Weighted Fractional Fourier Transform
  • Mixed Carrier Method for Underwater Communication Based on Weighted Fractional Fourier Transform

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Embodiment Construction

[0024] The present invention will be further described below in conjunction with embodiment and accompanying drawing.

[0025] First, let’s take a look at the periodic characteristics of the Fourier transform. The period of the traditional Fourier transform is 4. Let g(x) be a time-domain signal that satisfies the mean square integrability, and four consecutive Fourier transforms are performed on it. Transformation, the results obtained at each step are as follows:

[0026] g(x)→G(x)→g(-x)→G(-x)→g(x)

[0027] Among them, G(x) represents the frequency domain form of the signal, and g(-x) and G(-x) are the inversions of the time domain form and the frequency domain form of the signal, respectively.

[0028] In the definition of C.C.Shih, the four basic state functions correspond to the results of the 0-3 integer-order Fourier transform of the original signal, that is, g(x), G(x), g(-x) and G (-x) The specific expression of the four-item weighted fractional Fourier transform wh...

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Abstract

The invention provides an underwater communication hybrid carrier method based on weighted fractional order Fourier transform, and relates to underwater communication carrier systems. The underwater communication hybrid carrier method comprises: before sending a signal S, firstly sending a string of known sequence X having the same length and the same structure as the signal, and obtaining a receiving signal Y after S passes through a channel; selecting an optimal order alpha opt, feeding back the alpha opt to a sending end, and then sending the signal S; modulating baseband data on a weighted fractional Fourier transform domain with a transform order of alpha order, and transforming the modulated data to a time domain by using -alpha order fractional Fourier transform, and sending the modulated data into the channel; and transforming the data to a corresponding fractional domain according to the order rotation additivity of the fractional Fourier transform, namely the unitary property of the fractional Fourier transform for demodulation. The underwater communication hybrid carrier method can be used for effectively solving the problem that underwater target recognition requirements under new circumstances cannot be met due to a low recognition rate, poor robustness and low reliability of an underwater target recognition system.

Description

technical field [0001] The invention relates to an underwater communication carrier system, in particular to an underwater communication mixed carrier method based on weighted fractional Fourier transform. Background technique [0002] Because the underwater acoustic channel has the characteristics of large multipath delay and large Doppler frequency shift, it is necessary to improve the system performance in the fading channel environment. In order to cope with the above-mentioned complex and changeable underwater acoustic environment, the carrier systems currently used in the underwater acoustic communication system mainly include two types: Multi-carrier (Multiple Carrier, MC) Orthogonal Frequency Division Multiplexing (OFDM) Technology and Single Carrier-Frequency Domain Equalization (SingleCarrier-Frequency Domain Equalization, SC-FDE). Both have pros and cons: [0003] OFDM can effectively resist frequency selective fading and improve spectrum utilization. Ideally, ...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04B13/02H04L27/32H04L25/02
Inventor 齐洁孙伟涛孙海信周小平曹政
Owner XIAMEN UNIV