Combined super-exponential iteration blind equalization algorithm based on orthogonal wavelet transform

Abstract

The invention discloses a super-exponential interative combined blind equalization method based on orthogonal wavelet transformation (WT-CSEI). The WT-CSEI algorithm is implemented by incorporating the orthogonal wavelet transformation in the super-exponential interative (SEI) algorithm, correcting by use of the weight vector iterative formula of the orthogonal wavelet transformation relative to the SEI algorithm, simultaneously combining the decision directed (DD) algorithm with the soft-switching method, and introducing a phase-locked loop (PLL) technique with regard to the characteristics of time-variable Doppler frequency shift of under acoustic channel. The WT-CSEI algorithm corrects the phase rotation by means of the PLL technique, accelerates the convergence rate by means of the orthogonal wavelet transformation, reduces the steady-state error by means of the combination of the soft switching method and the DD algorithm, can effectively track the time varying characteristics of the channel, and is applied to the blind equalization of the time-variable multipath fading underwater acoustic channel.

Description

technical field [0001] The invention relates to a super-exponential iterative joint blind equalization method, in particular to a super-exponential iterative joint blind equalization method based on orthogonal wavelet transform. Background technique [0002] In underwater communication systems, limited bandwidth and multipath propagation will lead to serious inter-symbol interference (Inter-Symbol Interference, ISI), which needs to be eliminated by equalization technology at the receiving end. Compared with traditional adaptive equalization, blind equalization does not need to transmit training sequences periodically, and has high channel utilization, so it is suitable for underwater acoustic channel equalization. Among various blind equalization algorithms, Shalvi and Weinstein directly use high-order statistics to propose a super-exponential iterative blind equalization (Super-ExponentialIterative, SEI) algorithm with almost super-exponential convergence (see literature: O...

AI Technical Summary

Problems solved by technology

However, the algorithm can only work when the phase rotation is constant, and the phase rotation cannot be corrected quickly in the non-stationary underwater acoustic channel, and the hard switching method used by it will cause the algorithm to be unstable.

Literature (see: De CASTRO F C C, De CASTRO M C F. Concurrent blind deconvolution for channel equali-zation [C] Proc ICC'2001, 2: 366-371) proposed a soft handover CMA+DD algorithm, the CMA It is used together with the DD algorithm to adjust the weight vector of the equalizer. Only when the judgment output of the equalizer before and after the CMA adjustment is consistent, the DD algorithm participates in the weight vector adjustment. This algorithm avoids the adverse effects of hard switching, but the algorithm Does not change the autocorrelation of the input signal to the equalizer, which is one of the main factors affecting the algorithm

Images