• Title/Summary/Keyword: wavelet-based MMSE filter

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Reduction of Speckle Noise in Images Using Homomorphic Wavelet-Based MMSE Filter with Edge Detection (에지 영역을 고려한 호모모르픽 웨이브렛 기반 MMSE 필터를 이용한 영상 신호의 스펙클 잡음 제거)

  • 박원용;장익훈;김남철
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.11C
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    • pp.1098-1110
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    • 2003
  • In this paper, we propose a homomorphic wavelet-based MMSE filter with edge detection to restore images degraded by speckle noise. In the proposed method, a noisy image is first transformed into logarithmic domain. Each pixel in the transformed image is then classified into flat and edge regions by applying DIP operator to the image restored by homomorphic directional MMSE filter. Each pixel in flat region is restored by homomorphic wavelet-based MMSE filter. Each pixel in edge region is restored by the weighted sum of the output of homomorphic wavelet-based MMSE filtering and that of homomorphic directional MMSE filtering. The restored image in spatial domain is finally obtained by applying the exponential function to the restored image in logarithmic domain. Experimental results show that the restored images by the proposed method have ISNR improvement of 3.3-4.0 ㏈ and ${\beta}$, a measurement parameter on edge preservation, improvement of 0.0103-0.0126 and superior subjective image quality over those by conventional methods.

Speckle Noise Reduction for Ultrasonic Images Using Homomorphic Wavelet-based MMSE Filter (호모모르픽 웨이브렛 기반 MMSE 필터를 이용한 초음파영상의 스펙클 잡음 제거)

  • 박원용;장익훈;김남철
    • Proceedings of the IEEK Conference
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    • 2000.09a
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    • pp.679-682
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    • 2000
  • In this paper, a MMSE filter in homomorphic wavelet transform domain is proposed for restoring an ultrasonic images corrupted by speckle noise. In order to remove effectively the speckle noise which is a kind of multiplicative noise, speckle noise is transformed into a form of additive noise and then the additive noise is denoised through the MMSE filter in homomorphic wavelet transform domain. The proposed method shows much higher quality in terms of ISNR and subject quality.

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Performance analysis of WPM-based transmission with equalization-aware bit loading

  • Buddhacharya, Sarbagya;Saengudomlert, Poompat
    • ETRI Journal
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    • v.41 no.2
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    • pp.184-196
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    • 2019
  • Wavelet packet modulation (WPM) is a multicarrier modulation (MCM) technique that has emerged as a potential alternative to the widely used orthogonal frequency-division multiplexing (OFDM) method. Because WPM has overlapped symbols, equalization cannot rely on the use of the cyclic prefix (CP), which is used in OFDM. This study applies linear minimum mean-square error (MMSE) equalization in the time domain instead of in the frequency domain to achieve low computational complexity. With a modest equalizer filter length, the imperfection of MMSE equalization results in subcarrier attenuation and noise amplification, which are considered in the development of a bit-loading algorithm. Analytical expressions for the bit error rate (BER) performance are derived and validated using simulation results. A performance evaluation is carried out in different test scenarios as per Recommendation ITU-R M.1225. Numerical results show that WPM with equalization-aware bit loading outperforms OFDM with bit loading. Because previous comparisons between WPM and OFDM did not include bit loading, the results obtained provide additional evidence of the benefits of WPM over OFDM.