Method for accurately estimating underwater sound OFDM Doppler factor
A technology for accurate estimation of Doppler factor, applied in the field of accurate estimation of underwater acoustic OFDM Doppler factor, can solve the problems of underutilization of synchronization code characteristics and inaccurate estimation results, so as to reduce implementation complexity and improve multiplexing. The effect of improving the estimation accuracy
Inactive Publication Date: 2014-03-05
JIANGSU UNIV OF SCI & TECH
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[0007] The object of the present invention is to provide a method for accurately estimating the underwater acoustic OFDM Doppler factor. Aiming at the characteristics of the preamble designed by the present invention, a method for accurately estimating Doppler is proposed based on the traditional estimation method based on correlation processing. The factor method solves the shortcomings of the traditional correlation method that the estimation results are inaccurate and the characteristics of the synchronization code are not fully utilized.
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[0033] The present invention will be further described below in conjunction with the drawings and specific embodiments.
[0034] To facilitate the understanding of the basic principles and specific methods of the present invention, the system model adopted by the present invention is first given.
[0035] 1. OFDM modulation model
[0036] Attached here figure 2 The preamble in the description.
[0037] Suppose the number of OFDM subcarriers in the preamble is K, and the frequency of the kth subcarrier is f k = F c +kΔf, Δf=1 / T is the subcarrier spacing, T is the symbol duration, f c Is the carrier frequency. As attached figure 2 As shown, let T cp Be the length of the cyclic prefix in the preamble, and let
[0038]
[0039] Then the baseband form of the preamble can be expressed as
[0040] s ( t ) = Re { X k = 1 K s [ k ] e j 2 πkΔft q ( t ) } - - - ( 2 )
[0041] In the above formula, s[k] are the k...
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The invention discloses a method for accurately estimating an underwater sound OFDM Doppler factor. The method includes the steps that an OFDM frame format is designed, a preamble with a cyclic prefix and a CW simple-frequency signal are added, Doppler estimation is carried on a received signal three times, the range is narrowed step by step, the accuracy is improved step by step, and fairly high estimating accuracy is reached. The CW signal is used for performing the Doppler coarse estimation for the first time, and with the result of the first-time estimation combined with a preamble structure as the characteristic, the second-time Doppler estimation is performed through a self-correlation method. The characteristic that the preamble is known for a receiving end is further used, the estimation range of the Doppler factor is narrowed on the basis of the second-time Doppler estimation, and the third-time Doppler estimation is performed through a cross-correlation method. All characteristics of the preamble are used comprehensively, and the estimation accuracy of the Doppler factor is greatly improved on the premise that complexity is not increased.
Description
Technical field [0001] The invention relates to a method for accurately estimating the Doppler factor of an underwater acoustic OFDM, and belongs to the technical field of underwater acoustic communication. Background technique [0002] With the frequent marine development activities, people's requirements for high-speed underwater acoustic communication have become inevitable. As a form of multi-carrier modulation, Orthogonal Frequency Division Multiplexing (OFDM) technology is more and more popular due to its low complexity, resistance to multipath fading, high frequency band utilization and transmission speed. People's favor. Compared with land-based radio communication, due to the low propagation rate of sound waves in water (about 1500m / s) and the inherent complexity of underwater acoustic channels, underwater acoustic OFDM faces severe Doppler spread, and the inter-OFDM subcarrier Orthogonality is destroyed, causing Inter-Carrier Interference (ICI), resulting in deteriora...
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Inventor 王彪支志福朱志宇戴跃伟
Owner JIANGSU UNIV OF SCI & TECH