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On the use of compressive sensing for image enhancement
, Article Proceedings - 2016 UKSim-AMSS 18th International Conference on Computer Modelling and Simulation, UKSim 2016, 6 April 2016 through 8 April 2016 ; 2016 , Pages 167-171 ; 9781509008889 (ISBN) ; Ghorshi, S ; Khoshnevis, S. A ; Pourebrahim, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Compressed Sensing (CS), as a new rapidly growing research field, promises to effectively recover a sparse signal at the rate of below Nyquist rate. This revolutionary technology strongly relies on the sparsity of the signal and incoherency between sensing basis and representation basis. Exact recovery of a sparse signal will be occurred in a situation that the signal of interest sensed randomly and the measurements are also taken based on sparsity level and log factor of the signal dimension. In this paper, compressed sensing method is proposed to reduce the noise and reconstruct the image signal. Noise reduction and image reconstruction are formulated in the theoretical framework of...
Improved CT image reconstruction through partial Fourier sampling
, Article Scientia Iranica ; Volume 23, Issue 6 , 2016 , Pages 2908-2916 ; 10263098 (ISSN) ; Kavehvash, Z ; Shabany, M ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
A novel CT imaging structure based on Compressive Sensing (CS) is proposed. The main goal is to mitigate the CT imaging time and, thus, X-ray radiation dosage without compromising the image quality. The utilized compressive sensing approach is based on radial Fourier sampling. Thanks to the intrinsic relation between captured radon samples in a CT imaging process and the radial Fourier samples, partial Fourier sampling could be implemented systematically. This systematic compressive sampling helps in better control of required conditions such as incoherence and sparsity to guarantee adequate image quality in comparison to previous CS-based CT imaging structures. Simulation results prove the...
Technique for order of preference by similarity to ideal solution based predictive handoff for heterogeneous networks
, Article IET Communications ; Volume 10, Issue 13 , 2016 , Pages 1682-1690 ; 17518628 (ISSN) ; Kalbkhani, H ; Lotfollahzadeh, T ; Shayesteh, M. G ; Solouk, V ; Sharif University of Technology
Institution of Engineering and Technology
Abstract
This study presents an efficient handoff algorithm for heterogeneous networks comprising macrocells, microcells, picocells, and femtocells. The proposed algorithm is based on call admission control (CAC) for selecting target base station (BS) from a list of neighbouring candidate BSs, as well as using the technique for order of preference by similarity to ideal solution (TOPSIS) as decision method. The introduced algorithm takes into account multiple criteria including measured received signal strength (RSS) and signal-to-interference-plus noise ratio (SINR), predicted RSS and SINR, and number of free resource blocks of neighbouring BSs. With the use of TOPSIS, neighbouring BSs are ordered...
K-Space aware multi-static millimeter-wave imaging
, Article IEEE Transactions on Image Processing ; Volume 28, Issue 7 , 2019 , Pages 3613-3623 ; 10577149 (ISSN) ; Kavehvash, Z ; Shabany, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
This paper focuses on an efficient approach for designing multi-static arrays for millimeter-wave imaging, based on the k -space or Fourier-spatial domain characteristic of imaging systems. Our goal is to decrease the redundancy of the data measured by each antenna and to improve the resolution of the reconstructed image. The proposed technique is based on determining the role of each transmitter and receiver, in collecting the data from each voxel of the target in k -space domain and then rotating the transmitters' beams to measure the desirable information. The effect of non-uniform redundant k -space domain frequency samples that act as an undesirable filter is compensated using a...
Outage performance in secure cooperative NOMA
, Article 2019 Iran Workshop on Communication and Information Theory, IWCIT 2019, 24 April 2019 through 25 April 2019 ; 2019 ; 9781728105840 (ISBN) ; Mirmohseni, M ; Aref, M. R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Enabling cooperation in a NOMA system is a promising approach to improve its performance. In this paper, we study the cooperation in a secure NOMA system, where the legitimate users are distributed uniformly in the network and the eavesdroppers are distributed according to a homogeneous Poisson point process. We consider a cooperative NOMA scheme (two users are paired as strong and weak users) in two phases: 1) Direct transmission phase, in which the base station broadcasts a superposition of the messages, 2) Cooperation phase, in which the strong user acts as a relay to help in forwarding the messages of the weak user. We study the secrecy outage performance in two cases: (i) security of...
Upper bounds on the ergodic and outage capacities of relay networks using UWB links
, Article 40th Asilomar Conference on Signals, Systems, and Computers, ACSSC '06, Pacific Grove, CA, 29 October 2006 through 1 November 2006 ; 2006 , Pages 646-650 ; 10586393 (ISSN); 1424407850 (ISBN); 9781424407859 (ISBN) ; Nasiri Kenari, M ; Wehinger, J ; Mecklenbräuker, C. F ; Sharif University of Technology
2006
Abstract
We derive, evaluate, and discuss upper bounds on ergodic and outage capacities for a three-node relay network. The considered relay network has ultra-wideband (UWB) radio channels between the source, destination, and relay nodes. The derived bounds indicate that ergodic and outage capacities of the considered UWB-linked network increase up to 300% when a relay between the source and the destination is used. Furthermore, the bounds indicate that there is an optimum position for the relay node between the source and the destination, where ergodic capacity is maximized. Our numerical results shows that for the non-line-of-sight (NLOS) scenario, with the same signal to noise ratio on all links,...
Phase-induced intensity noise in digital incoherent all-optical tapped-delay line systems
, Article Journal of Lightwave Technology ; Volume 24, Issue 8 , 2006 , Pages 3059-3072 ; 07338724 (ISSN) ; Salehi, J. A ; Sharif University of Technology
2006
Abstract
In this paper, the authors analyze conditions under which they can be certain on the intensity addition of a given device, such as tapped-delay lines, used in digital incoherent all-optical communication systems. A general expression for phase-induced intensity noise that is applicable to all types of semiconductor lasers is derived by defining an optical self-SNR expression that can be used to analyze and measure phase-induced intensity noise. The result shows that in order to have a minimal phase-induced intensity noise in most digital optical incoherent systems, a large optical self-SNR, e.g., 20 dB or more, is needed. This in turn is shown to place a limit on the maximum rate of...
Fast wavelet-based photoacoustic microscopy
, Article Journal of the Optical Society of America A: Optics and Image Science, and Vision ; Volume 38, Issue 11 , 2021 , Pages 1673-1680 ; 10847529 (ISSN) ; Mostafavi, S. M ; Kavehvash, Z ; Sharif University of Technology
The Optical Society
2021
Abstract
A novel photoacoustic microscopy (PAM) structure, based on Haar wavelet patterns, is proposed in this paper. Its main goal is to mitigate the PAM imaging resolution and thus the time of its sampling process without compromising the image quality. Owing to the intrinsic nature of wavelet transform, this structure collects spatial and spectral components simultaneously, and this feature speeds up the sampling process by 33%. The selection of these patterns helps in better control of required conditions, such as multi-resolution imaging, to guarantee adequate image quality in comparison to previous microscopic structures. Simulation results prove the superior quality of the proposed approach...
Fast wavelet-based photoacoustic microscopy
, Article Journal of the Optical Society of America A: Optics and Image Science, and Vision ; Volume 38, Issue 11 , 2021 , Pages 1673-1680 ; 10847529 (ISSN) ; Mostafavi, S. M ; Kavehvash, Z ; Sharif University of Technology
The Optical Society
2021
Abstract
A novel photoacoustic microscopy (PAM) structure, based on Haar wavelet patterns, is proposed in this paper. Its main goal is to mitigate the PAM imaging resolution and thus the time of its sampling process without compromising the image quality. Owing to the intrinsic nature of wavelet transform, this structure collects spatial and spectral components simultaneously, and this feature speeds up the sampling process by 33%. The selection of these patterns helps in better control of required conditions, such as multi-resolution imaging, to guarantee adequate image quality in comparison to previous microscopic structures. Simulation results prove the superior quality of the proposed approach...
Optimization of higher order pulse shapers used for reduction of noise in amplifier circuits
, Article Scientia Iranica ; Volume 12, Issue 1 , 2005 , Pages 75-82 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology
2005
Abstract
Active components in amplifiers generate noise. Thus, amplifiers too, produce noise at their output and, therefore, increase the input signal to noise ratio. This is an undesirable feature, more particularly when one is dealing with weak input signals already combined with noise. Thus, reducing amplifiers' noise becomes a necessity for some applications. To overcome this problem, one approach consists of improving electronic device technology. Another approach is the use of advanced techniques in designing low noise amplifiers by taking advantage of pulse shapers. Pulse shapers generally consist of calculated filters made of integrator(s) and differentiator(s) that limit properly the...
Reduced complexity 1-bit high-order digital delta-sigma modulator for low-voltage fractional-N frequency synthesis applications
, Article IEE Proceedings: Circuits, Devices and Systems ; Volume 152, Issue 5 , 2005 , Pages 471-477 ; 13502409 (ISSN) ; Afzali Kusha, A ; Dehghani, R ; Mehrara, M ; Atarodi, S. M ; Nourani, M ; Sharif University of Technology
2005
Abstract
A reduced complexity third-order digital delta-sigma modulator for fractional-N frequency synthesis is presented. The high-performance modulator, which consists of two subblocks, has a single-bit output making it best for this sort of application. A good shaping of quantisation noise is achieved using a new architecture for a digital third-order delta-sigma modulator. The hardware required for this modulator is considerably less than that in previously reported leading to lower power and area consumption and a higher operating frequency. The field programmable gate array (FPGA) implementation of the whole system shows an SNR of at least 94 dB and an operating input range of 0.7 of the full...
Investigation of the Photonic Scattering Error in Radiography of Pipes and its Evaluation by Mote- carlo Simulation
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Nasser (Supervisor) ; Movafeghi, Amir (Co-Advisor) ; Kermani, Abotaleb (Co-Advisor)
Abstract
Non-destructive testing method is for detect specimen flaws such as (crack, porosity, impure, welding defects, corrosion etc.) without destruction the specimen under inspection. Particular characteristic of radiography is an image product from specimen inside under testing where help to identity and better comprehend at flaw nature. Photon scattering is one of important factor to reduce image quality and signal to noise ratio. Scattered photons can due toexistent ingredient in the radiography environment and curvature of material transmission pipe where cause the disorder creation in the radiography images. In this research, pipe radiography simulated using the TIC and TIR radiography...
Design and Optimization of Magnetic Resonance Signal Detector to Enhancement of Sensitivity and SNR in Proton Precession Sensor
, M.Sc. Thesis Sharif University of Technology ; Fardmanesh, Mahdi (Supervisor)
Abstract
Proton precession is used in measurement of scalar magnetic field intensity. In this sensor, the magnetic field intensity is calculated through Larmor frequency using the proton precession frequency around the magnetic field. The accuracy of this sensor is in the range of picoTesla which is used for magnetic field measurement as well as the calibration of vector magnetic sensors. The signal to noise ratio in this sensor is due to the dimension and resistances of the wires and is a kind of RMS random noise. Although, changing the dimension of the wires for noise reduction and increasing the signal amplitude requires the fabrication of a bulky sensor with low power consumption. Therefore, it...
On the capacity of signal dependent noise channels
, Article IWCIT 2017 - Iran Workshop on Communication and Information Theory, 3 May 2017 through 4 May 2017 ; 2017 ; 9781509047833 (ISBN) ; Ghourchian, H ; Gohari, A ; Mirmohseni, M ; Nasiri Kenari, M ; Sharif University of Technology
Abstract
In some applications, the variance of measurement noise depends on the signal that we aim to measure. For instance, additive Gaussian signal-dependent noise (AGSDN) channel models are used in molecular and optical communication. Herein we provide lower and upper bounds on the capacity of additive signal dependent noise (ASDN) channels. We also provide sufficient conditions under which the capacity becomes infinity. © 2017 IEEE
LPRE: Lost speech packet recovery withenhancement
, Article 2007 IEEE International Conference on Communications, ICC'07, Glasgow, Scotland, 24 June 2007 through 28 June 2007 ; August , 2007 , Pages 1778-1783 ; 05361486 (ISSN); 1424403537 (ISBN); 9781424403530 (ISBN) ; Manzuri Shalmani, M. T ; Sharif University of Technology
2007
Abstract
In the internet telephony, loss of IP packets causes instantaneous discontinuities in the received speech. In this paper, we have focused on finding an error resilient method for this problem. Our proposed method creates artificial correlation between speech samples that pre-distorts the speech signal. The receiver uses this correlation to reconstruct the lost speech packets. An appropriate speech enhancement technique is designed for the reduction of the processing error in the recovered speech caused by the speech codecs. The SegSNR results show the superiority of our proposed speech enhancement method over a recently proposed one. © 2007 IEEE
On a decentralized deterministic transmission power level selection algorithm in large aloha networks under saturation
, Article 2006 IEEE International Conference on Communications, ICC 2006, Istanbul, 11 July 2006 through 15 July 2006 ; Volume 12 , 2006 , Pages 5732-5737 ; 05361486 (ISSN); 1424403553 (ISBN); 9781424403554 (ISBN) ; Khalaj, B. H ; Sharif University of Technology
2006
Abstract
In this paper, we will analyze a decentralized transmission power level selection algorithm in conjunction with Binary Exponential Back-off retransmission scheme, in large slotted-Aloha networks under saturation condition. In this algorithm, the transmission power is steadily increased by an amount called power step, until the packet is successfully transmitted. We will use SIR-based capture model to study the performance of this algorithm with small and large power steps. Our analysis proves that, although small power steps may seem favorable for power saving purposes, these power steps face throughput collapse under high load conditions (large number of nodes), while properly chosen large...
A low voltage, high speed, high resolution class AB switched current sample and hold
, Article ISCAS 2006: 2006 IEEE International Symposium on Circuits and Systems, Kos, 21 May 2006 through 24 May 2006 ; 2006 , Pages 1039-1042 ; 02714310 (ISSN); 0780393902 (ISBN); 9780780393905 (ISBN) ; Jahanian, A ; Sharif Bakhtiar, M ; Sharif University of Technology
2006
Abstract
A high speed, high resolution switched-current sample and hold (SI S/H) based on a new class AB transconductance stage is presented. Simulations performed on the SI S/H in standard 0.18um CMOS technology with 1.5v supply voltage indicate low power dissipation, high sampling speed and high SNR. © 2006 IEEE
A new adaptive lifting scheme transform for robust object detection
, Article 2006 IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP 2006, Toulouse, 14 May 2006 through 19 May 2006 ; Volume 2 , 2006 , Pages II749-II752 ; 15206149 (ISSN); 142440469X (ISBN); 9781424404698 (ISBN) ; Rabiee, H. R ; Sharif University of Technology
2006
Abstract
This paper presents a new adaptive lifting scheme transform for detecting user-selected objects in a sequence of images. In our algorithm, we first select a set of object features in the wavelet transform domain and then build an adaptive transform by using the selected features. The adaptive transform is constructed based on adaptive prediction in a lifting scheme procedure. Adaptive prediction is performed such that, the large coefficients in the high-pass component of the non-adaptive transform vanishes in the high-pass component of the adaptive transform. Finally, both the non-adaptive and adaptive transforms are applied to a given test image and the transform domain coefficients are...
Power control for multirate CDMA systems with imperfect successive interference cancellation
, Article 2004 IEEE Wireless Communications and Networking Conference, WCNC 2004, Atlanta, GA, 21 March 2004 through 25 March 2004 ; Volume 3 , 2004 , Pages 1388-1393 ; 0780383443 (ISBN) ; Khalaj, B. H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2004
Abstract
In this paper, we will address the issue of power distribution and decoding order in the uplink side of a multirate code division multiple access (CDMA) system based on linear successive interference cancellation (SIC). First, the closed form expressions for the required received powers at the base station, in order to achieve the users bit rate and Quality of Service (QoS) requirements, will be derived. Then, we will investigate the problem of optimal decoding order of the users under imperfect interference cancellation condition and will show that optimum decoding order of users, unlike the case of perfect SIC, is a function of their requested SINR values in addition to their path gains....
A novel two frequency MTI radar
, Article Proceedings of the IEEE Radar Conference, Philadelphia, PA, 26 April 2004 through 29 April 2004 ; 2004 , Pages 589-591 ; Norouzi, Y ; Nayebi, M. M ; Sharif University of Technology
2004
Abstract
The paper introduced a new design for two-frequency MTI radar is introduced. The suggested system can change its frequencies, in each pulse. Therefore, the system is very resistive to electronic war. The analytical results of our calculation show that the system has very high blind speed and in realistic situations, it increases signal to noise ratio, although it widens clutter bandwidth and detects some spurious targets