A Novel Blind Estimation Method of SFO based on QPSK

Author(s):  
Kaiyan Du ◽  
Xiangning Chen ◽  
Miantao Wang
Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3552 ◽  
Author(s):  
Yunda Zheng ◽  
Wei Huang ◽  
Yun Pan ◽  
Mingfei Xu

Simple optical system imaging is a method to simplify optical systems by removing aberrations using image deconvolution. The point spread function (PSF) used in deconvolution is an important factor that affects the image quality. However, it is difficult to obtain optimal PSFs. The blind estimation of PSFs relies heavily on the information in the image. Measured PSFs are often misused because real sensors are wide-band. We present an optimal PSF estimation method based on PSF measurements. Narrow-band PSF measurements at a single depth are used to calibrate the optical system; these enable the simulation of real lenses. Then, we simulate PSFs in the wavelength pass range of each color channel all over the field. The optimal PSFs are computed according to these simulated PSFs. The results indicated that the use of the optimal PSFs significantly reduces the artifacts caused by misuse of PSFs, and enhances the image quality.


Author(s):  
Fenglei Tian ◽  
Xiaoping Qian

The use of a flared tip and bi-directional servo control in some recent atomic force microscopes (AFM) has made it possible for these advanced AFMs to image structures of general shapes with undercuts and reentrant surfaces. Since AFM images are distorted representation of sample surfaces due to the dilation (a.k.a. convolution) produced by the finite size of the probe, it is necessary to obtain the tip shape in order to correct such tip distortion. This paper presents an approach that can for the first time estimate general three-dimensional tip shape from its scanned image in these AFMs. It extends one existing blind tip estimation method to the dexel representation, a computer representation that can represent general 3D shapes. As such, it can estimate general tip shapes, including undercuts or reentrant features.


2021 ◽  
Vol 11 (22) ◽  
pp. 10812
Author(s):  
Jusung Kang ◽  
Younghak Shin ◽  
Hyunku Lee ◽  
Jintae Park ◽  
Heungno Lee

In a frequency hopping spread spectrum (FHSS) network, the hopping pattern plays an important role in user authentication at the physical layer. However, recently, it has been possible to trace the hopping pattern through a blind estimation method for frequency hopping (FH) signals. If the hopping pattern can be reproduced, the attacker can imitate the FH signal and send the fake data to the FHSS system. To prevent this situation, a non-replicable authentication system that targets the physical layer of an FHSS network is required. In this study, a radio frequency fingerprinting-based emitter identification method targeting FH signals was proposed. A signal fingerprint (SF) was extracted and transformed into a spectrogram representing the time–frequency behavior of the SF. This spectrogram was trained on a deep inception network-based classifier, and an ensemble approach utilizing the multimodality of the SFs was applied. A detection algorithm was applied to the output vectors of the ensemble classifier for attacker detection. The results showed that the SF spectrogram can be effectively utilized to identify the emitter with 97% accuracy, and the output vectors of the classifier can be effectively utilized to detect the attacker with an area under the receiver operating characteristic curve of 0.99.


2013 ◽  
Vol 427-429 ◽  
pp. 1258-1262
Author(s):  
Xiao Zhi Liu ◽  
Jing Li ◽  
Liang Ming Wu

To estimate the spreading sequences for DS-CDMA system, a blind estimation method based on improved Fast-ICA is proposed. In this method, the ECA whitening and BAT optimization are introduced into the traditional Fast-ICA firstly, then the improved Fast-ICA is used to obtain spreading sequences matrix, finally, the spreading sequences are extracted from the spreading sequences matrix. Simulation results show the validity and superiority of the new method.


2018 ◽  
pp. 44-53
Author(s):  
Артем Юрьевич Харьков ◽  
Владимир Васильевич Лукин

In many practical situations, signals are corrupted by noise and it is desired to apply filtering to remove it. For most of modern filters, it is needed to know noise variance a priori or to pre-estimate it in a blind manner in the presence of signal component. Requirements to methods of blind estimation are formulated and it is shown that it is difficult to satisfy these requirements. Based on the used model of additive white Gaussian model, a method operting in DCT domain is considered and thoroughly studied. The choice of test signals is motivated. Local estimates obtained on blocks of different size are studied and it is demonstrated that these local estimates, although based on robust estimates of data scale, can be sufficiently influence by signal component that leads to a certain percentage of large amplitude DCT coefficients in data sample. It is then shown that such abnormal local estimates have to be rejected (or their influence on the final estimate should be minimized). This is done by robust processing of local estimates. It is established that block size considerably influences accuracy characterized by bias of estimates and their variance. The role of bias is dominant – noise standard deviation is overestimated - and the main task is to decrease it. According to experiments carried out for ten variants (parameter sets) of estimation method, the best results are, on the average, obtained if block size is equal to 32 and local estimates are processed using sample median. Computational efficiency is analyzed and it is shown that processing can be done quite quickly. This allows expecting real-time implementation for such applications as electrocardiogram and speech processing


2015 ◽  
Vol 713-715 ◽  
pp. 1313-1316
Author(s):  
Shou Zhong Zhang

To further improve the performance of channel estimation by particle filtering, an improved particle filtering method was proposed. The HF channel has multipath、fading and time-varying characteristics, and using the dynamic channel prediction model and the phased semi-blind estimation by improved particle filtering can obtain the tracking performance for the time varying channel. Based on stratified resampling of particle filtering, a criterion is set during the particle choosing process to ensure the valid of the chosen particles. Simulation result shows the effectiveness of the proposed method.


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