• Title/Summary/Keyword: SNR Estimation

Search Result 297, Processing Time 0.02 seconds

Adaptive Antenna Array for DOA Estimation Utilizing Orthogonal Weight Searching (직교가중치 탐색방법을 이용한 도착방향 추정 적응어레이 안테나)

  • 오정호;최승원;이현배;황영준
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.8 no.2
    • /
    • pp.116-125
    • /
    • 1997
  • This paper presents a novel method, entitled Orthogonal Weights Searching(OWS), for the Direction-Of-Arrival(DOA) estimation. Utilizing the modified Conjugate Gradient Method(MCGM), the weight vector which is orthogonal to the signal subspace is directly computed from the signal matrix. The proposed method does not require the computation of the eigenvalues and eigenvectors. In addition, the new technique excludes the procedure for the detection of the number of signals under the assumption that the number of weights in the array is greater than the number of input signals. Since the proposed technique can be performed independently of the detection procedure, it shows a good performance in adverse signal environments in which the detection of the number of array inputs cannot be obtained successfully. The performance of the proposed technique is compared with that of the convectional eigen-decomposition method in terms of angle resolution for a given signal-to-noise ratio(SNR) and a required amount of computations.

  • PDF

Blind Frequency offset Estimation for Radio Resource Saving in OFDM (OFDM에서 무선자원 절약을 위한 블라인드 주파수 옵셋 추정 방식)

  • Jeon, Hyoung-Goo;Kim, Kyoung-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.34 no.10C
    • /
    • pp.1001-1009
    • /
    • 2009
  • In this paper, an efficient blind frequency offset estimation method for radio resource saving in orthogonal frequency division multiplexing (OFDM) systems is proposed. In the proposed method, we obtain two time different received OFDM signal blocks by using the cyclic prefix and define the cost function by using the two OFDM signal blocks. We show that the cost function can be approximately expressed as a closed form cosine function. The approximated cosine function can be obtained from three independent cost function values calculated at three different frequency offsets. In the proposed method, the frequency offset can be estimated by calculating a frequency offset minimizing the approximated cosine function without searching all the frequency offset range. Unlike the conventional methods such as MUSIC method, the accuracy of the proposed method is independent of the searching resolution since the closed form solution exists. The computer simulation shows that the performance of the proposed method is superior to those of the MUSIC and the oversampling method.

Effect of Imperfect Channel Knowledge on M-QAM SER Performance of Space-Time Block Codes (불완전한 채널 정보가 시공간 블록 부호의 M-QAM 심볼에러율 성능에 미치는 영향)

  • 고은석;강창언;홍대식
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.27 no.2A
    • /
    • pp.99-108
    • /
    • 2002
  • In this paper, we discuss the effect of imperfect knowledge of the transmission channel on the M-QAM SER performance of space-time block codes. Because the channel knowledge is used for decoding of space-time block codes, the imperfect channel knowledge can degrade the performance of space-time block codes. In this paper, the channel mismatch error is modeled as errors in the estimation of the channel due to noise and errors due to the variation of the channel. We derive the analytic expression for the symbol error rate (SER) as a function of the average signal to interference ratio (SIR) per channel including the terms of channel mismatch errors. Simulation results show that the acceptable levels of channel estimation error is 10$\^$-3/ and that of channel variation is f$\_$d/T$\_$B/=0.001 at SNR=20dB in space-time block codes.

Weighted polynomial fitting method for estimating shape of acoustic sensor array (음향 센서 배열 형상 추정을 위한 가중 다항 근사화 기법)

  • Kim, Dong Gwan;Kim, Yong Guk;Choi, Chang-ho
    • The Journal of the Acoustical Society of Korea
    • /
    • v.39 no.4
    • /
    • pp.255-262
    • /
    • 2020
  • In modern passive sonar systems, a towed array sensor is used to minimize the effects of own ship noise and to get a higher SNR. The thin and long towed array sensor can be guided in a non-linear form according to the maneuvering of tow-ship. If this change of the array shape is not considered, the performance of beamformer may deteriorate. In order to properly beamform the elements in the array, an accurate estimate of the array shape is required. Various techniques exist for estimating the shape of the linear array. In the case of a method using a heading sensor, the estimation performance may be degraded due to the effect of heading sensor noise. As means of removing this potential error, weighted polynomial fitting technique for estimating array shape is developed here. In order to evaluate the performance of proposed method, we conducted computer simulation. From the experiments, it was confirmed that the proposed method is more robust to noise than the conventional method.

Performance Analysis with Imperfect Channel Estimation in Cooperative Diversity (공조 다이버시티에서의 부정확한 채널 추정을 고려한 성능 분석에 관한 연구)

  • Ro Sang-Min;Hong Dae-Sik
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.31 no.7A
    • /
    • pp.689-695
    • /
    • 2006
  • This paper focuses on the accurate performance evaluation of cooperative diversity technique with imperfect channel estimates. The channel environment for simulations and performance evaluation is supposed to be the slowly time-varying Rayleigh fading channel. The framework of the performance evaluation is based on the Moment Generating Function(MGF) approach. To apply the effect of this channel estimation error into the performance evaluation, we import an useful Gaussian approximation in formulating the effective noise component and the additive noise. The average BER performance of cooperative diversity with M-PSK and M-QAM is computed as a function of the ratio of the signal to the effective noise based on the approximation. The verification of computed performance is provided with simulations. The evaluated performance matches up to simulation results even in a low SNR region.

Quantitative Conductivity Estimation Error due to Statistical Noise in Complex $B_1{^+}$ Map (정량적 도전율측정의 오차와 $B_1{^+}$ map의 노이즈에 관한 분석)

  • Shin, Jaewook;Lee, Joonsung;Kim, Min-Oh;Choi, Narae;Seo, Jin Keun;Kim, Dong-Hyun
    • Investigative Magnetic Resonance Imaging
    • /
    • v.18 no.4
    • /
    • pp.303-313
    • /
    • 2014
  • Purpose : In-vivo conductivity reconstruction using transmit field ($B_1{^+}$) information of MRI was proposed. We assessed the accuracy of conductivity reconstruction in the presence of statistical noise in complex $B_1{^+}$ map and provided a parametric model of the conductivity-to-noise ratio value. Materials and Methods: The $B_1{^+}$ distribution was simulated for a cylindrical phantom model. By adding complex Gaussian noise to the simulated $B_1{^+}$ map, quantitative conductivity estimation error was evaluated. The quantitative evaluation process was repeated over several different parameters such as Larmor frequency, object radius and SNR of $B_1{^+}$ map. A parametric model for the conductivity-to-noise ratio was developed according to these various parameters. Results: According to the simulation results, conductivity estimation is more sensitive to statistical noise in $B_1{^+}$ phase than to noise in $B_1{^+}$ magnitude. The conductivity estimate of the object of interest does not depend on the external object surrounding it. The conductivity-to-noise ratio is proportional to the signal-to-noise ratio of the $B_1{^+}$ map, Larmor frequency, the conductivity value itself and the number of averaged pixels. To estimate accurate conductivity value of the targeted tissue, SNR of $B_1{^+}$ map and adequate filtering size have to be taken into account for conductivity reconstruction process. In addition, the simulation result was verified at 3T conventional MRI scanner. Conclusion: Through all these relationships, quantitative conductivity estimation error due to statistical noise in $B_1{^+}$ map is modeled. By using this model, further issues regarding filtering and reconstruction algorithms can be investigated for MREPT.

An Efficient Peak Detection Algorithm in Magnitude Spectrum for M-FSK Signal Classification (M-FSK 변조 신호 분류를 위한 효율적인 진폭 스펙트럼의 첨두 검출 방법)

  • Ahn, Woo-Hyun;Seo, Bo-Seok
    • Journal of Broadcast Engineering
    • /
    • v.19 no.6
    • /
    • pp.967-970
    • /
    • 2014
  • An efficient peak detection algorithm in magnitude spectrum is proposed to distinguish the M-frequency shift keying(FSK) signals from other digitally modulated signal. In addition, recognition of the modulation order estimation of FSK signals is also studied based on the fact that the magnitude spectrum of FSK signals reveals the number of peaks equal to the modulation order. When no a priori information about the signals, we utilize the histogram of the magnitude spectrum to determine the threshold which is important factor in peak detection algorithm. The simulation results show high probability of classification under 500 symbols and signal-to-noise ratio(SNR) higher than 4dB.

High-Resolution Algorithm for Direction Finding of Multiple Incoherent Plane Waves (다중 인코히어런트 평면파의 도래각 추정을 위한 고분해능 알고리즘)

  • 김영수;이성윤
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.24 no.9A
    • /
    • pp.1322-1328
    • /
    • 1999
  • In this paper, we propose a Multiple Signal Classification(MUSIC) in conjunction with signal enhancement (SE-MUSIC) for solving the direction-of-arrival estimation problem of multiple incoherent plane waves incident on a uniform linear array. The proposed SE-MUSIC algorithms involve the following main two-step procedure : ( i )to find the enhanced matrix that possesses the prescribed properties and which lies closest to a given covariance matrix estimate in the Frobenius norm sense and (ii) to apply the MUSIC to the enhanced matrix. Simulation results are illustrated to demonstrate the better resolution and statistical performance of the proposed method than MUSIC at lower SNR.

  • PDF

Automatic threshold selection for edge detection using a noise estimation scheme and its application (잡음추측을 이용한 자동적인 에지검출 문턱값 선택과 그 응용)

  • 김형수;오승준
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.21 no.3
    • /
    • pp.553-563
    • /
    • 1996
  • Detecting edges is one of issues with essentialimprotance in the area of image analysis. An edge in an image is a boundary or contour at which a significant change occurs in image intensity. Edge detection has been studied in many addlications such as imagesegmentation, robot vision, and image compression. In this paper, we propose an automatic threshold selection scheme for edge detection and show its application to noise elimination. The scheme suggested here applied statistical properties of the noise estimated from a noisy image to threshold selection. Since a selected threshold value in the scheme depends on not the characgreistic of an orginal image but the statistical feature of added noise, we can remove ad-hoc manners used for selecting the threshold value as well as decide the value theoretically. Furthermore, that shceme can reduce the number of edge pixels either generated or lost by noise. an application of the scheme to noise elimination is shown here. Noise in the input image can be eliminated with considering the direction of each edge pixedl on the edge map obtained by applying the threshold selection scheme proposed in this paper. Achieving significantly improved results in terms of SNR as well as subjective quality, we can claim that the suggested method works well.

  • PDF

Evaluation of an Efficient Channel Estimator for the STTD Schemes

  • Kim, Seong-Hwan;Na, Cheol-Hun;Ryoo, Sang-Jin;Hwang, In-Tae
    • Journal of information and communication convergence engineering
    • /
    • v.5 no.3
    • /
    • pp.185-193
    • /
    • 2007
  • This paper evaluates the performance combining space-time transmit diversity (STTD) and an efficient channel estimator (ECE) for wideband code division multiple access (WCDMA) systems in various mobile channels. Using decision variable (DV), we also derive the analytic bit error rate (BER) and mean square error (MSE) for WCDMA applying ECE for STTD schemes. The simulation results show that the ECE performance is superior to the previous works in [1] as because we use additional pilot diversity which is so called secondary common control physical channel (S-CCPCH). The performance in case of the channel estimator using only one-channel or two-channel is worse than that of an ECE as about the maximum 4 dB at BER 1.0E-3 satisfying voice service over Rician fading channel. Our results show that, even with ICE, an ECE algorithm are effective in improving the output SNR and significantly reduce the error floor. In addition, the simulation results investigated in this paper also reveal that WCDMA combining an ECE and the STTD scheme could provide appreciable performance improvements in Rayleigh fading channel.