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    Fusion of Audio and Visual Occurrences using Fuzzy Logic for Improving Perception Quality of Events

    , Ph.D. Dissertation Sharif University of Technology Faraji, Mohammad Mahdi (Author) ; Bagheri Shouraki, Saeed (Supervisor)
    The ability of human to analyze the environment around them has been an inspiring source for event analysis research. Since human perception of the environment is formed in a multi-modal space, many efforts have been made to fuse information to create an intelligent fusion. In this study, we want to better understand the environment using information fusion. For this purpose, fuzzy fusion of audio and video signals based on ink drop spread operator is performed for recognizing and tracking of the targets using several scenarios of the AV16.3 dataset. We then focused on the fusion of audio data for sound source localization, one of the most important applications in evaluating fusion... 

    A Novel Simultaneous Frequency and Spatial Filtering Methodology for Beam-forming and Null-steering in Integrated Phased-Array Systems Using N-path technique

    , Ph.D. Dissertation Sharif University of Technology Karami, Poorya (Author) ; Atarodi, Mojtaba (Supervisor)
    In the communication systems, there are two types of blockers: in-band and out-of-band. High frequency pre-filters and band-pass filters can be used to suppress the out-of band blockers. However, using these methods does not affect the in-band interferers. Spatial filtering by means of phased array antennas and using frequency filtering can suppress both types of interferers. In a typical phased array receiver, all of the received signals pass through active blocks (such as LNAs, active phase shifters, driver amplifiers, etc.) that amplify the interferers before canceling them. Therefore, because of the high strength of the interferers, the dynamic range of the front-end blocks preceding... 

    Phase Shifter Response Compensation in Microwave Band

    , M.Sc. Thesis Sharif University of Technology Aghaei Saem, Ali (Author) ; Khavasi, Amin (Supervisor) ; Fakharzadeh, Mohammad (Co-Supervisor)
    A phase shifter is a microwave element that changes the phase of the input signal at a specific center frequency and bandwidth and, ideally, produces a signal with the same amplitude and a modified phase at the output. In practice, this phase change in the passive phase shifter is accompanied by a decrease in amplitude due to different factors. Various use cases can be described for phase shifters in telecommunication circuits, but its most important application is in regulating the relative phase of each antenna in a phased array system, which is the most common method of beam steering and forming. A phased array system is one of the leading solutions to achieve beamforming and high... 

    Increasing Operating Range of Wideband Reconnaissance Receivers, by Using Antenna Arrays

    , Ph.D. Dissertation Sharif University of Technology Sobhani, Ghasem (Author) ; Behnia, Fereidoon (Supervisor)
    Passive wideband reconnaissance receivers, listen to the radio and radar signals in the environment and estimate their important parameters such as direction of arrival (DOA). The wideband attribute for these receivers is to refer to their ability to receive wideband signals.Due to the use of processing gain, LPI radars reduce their transmitted signal power to see and not to be seen. On the other hand reconnaissance receivers can not have much processing gain, because they do not know the nature of the transmitted signal; Therefore, to increase the operational range of these systems, it is necessary to increase the signal to noise power ratio (SNR). This thesis examines the use of antenna... 

    Rate adaptation and power allocation for time-correlated MISO Rayleigh fading channel with delay-limited HARQ

    , Article IEEE International Conference on Communications, 10 June 2012 through 15 June 2012 ; 2012 , Pages 3915-3919 ; 15503607 (ISSN) ; 9781457720512 (E-ISBN) Rastegar, S. H ; Vakilinia, S ; Khalaj, B. H ; Sharif University of Technology
    In this paper, we consider the problem of optimum rate adaptation and power allocation to maximize the delay-limited throughput (DLT) in a time-correlated 2×1 MISO Rayleigh fading channel with Hybrid ARQ in Chase-Combining mode (HARQ-CC). To this aim, we have first formulated the DLT equation based on the outage probability for 2×1 MISO-HARQ channel. We show that exact analytical calculation of the outage probability is not tractable. Therefore, we approximate the outage probability using a log-normal approximation approach. Based on such approximation, optimal rate and power allocations are derived. Finally, using Monte-Carlo simulation, we show that the approximation method provides... 

    Precoding in relay networks with frequency selective channels

    , Article Conference Record - Asilomar Conference on Signals, Systems and Computers ; 2012 , Pages 537-541 ; 10586393 (ISSN) ; 9781467350518 (ISBN) Schad, A ; Khalaj, B ; Pesavento, M ; Sharif University of Technology
    We consider a wireless network with one source, multiple relays and multiple destinations. The source and the relays are assumed to utilize multiple antennas. To reduce the effects of the frequency selective source-to-relay and relay-to-destination channels, and to compensate for the different delays of the various signal paths in the network and for multi-user interference and noise, the source, the relays and the destinations apply linear filtering to their signals. The proposed scheme generalizes the recently proposed filter-and-forward relaying scheme. We propose an iterative algorithm to solve the problem of maximizing the quality-of-service at the destinations. Simulation results... 

    Analytical power allocation for a full duplex decode-and-forward relay channel

    , Article 2013 Iran Workshop on Communication and Information Theory ; 2013 ; 9781467350235 (ISBN) Golami Davoodi, A ; Emadi, M. J ; Aref, M. R ; Sharif University of Technology
    For a Rayleigh fading full-duplex decode-and-forward relay channel, we analytically derive optimum power allocation schemes subject to individual power constraints for the source and the relay. The optimization problem is taken over the source power and the relay power. It is proven that the optimization problem is concave for this scenario, and optimum power allocations are derived in a closed-form. Finally, the implications of the theoretical results are discussed through the graphs  

    Large Array Null Steering Using Compressed Sensing

    , Article IEEE Signal Processing Letters ; Volume 23, Issue 8 , 2016 , Pages 1032-1036 ; 10709908 (ISSN) Khosravi, M ; Fakharzadeh, M ; Bastani, M. H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    In this letter, array null steering is formulated as a sparse recovery problem. In addition, a novel null steering scheme for large arrays by perturbing only a few elements is presented. To achieve this goal, compressed sensing (CS) is used to exploit the sparsity of the perturbed elements. The advantages of the proposed scheme are a significant reduction in hardware cost and lower power consumption, as well as less aging of the elements and faster response. Simulation results show that the CS-based method could be efficiently used to generate wide nulls using at least two elements. The interference rejection ratio achieved by the proposed method is 10-20 dB better than the existing... 

    A figure of merit in a time-modulated array

    , Article IEEE Antennas and Wireless Propagation Letters ; Volume 18, Issue 10 , 2019 , Pages 2086-2089 ; 15361225 (ISSN) Mazaheri, M. H ; Fakharzadeh, M ; Akbari, M ; Safavi Naeini, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    In this letter, we use G/T as a figure of merit to evaluate the performance of time-modulated arrays (TMA). The noise performance of a receiver, which is periodically switched on and off, is quite different from that of a conventional receiver. We analytically investigate the noise performance of a TMA. Based on this analysis, the figure of merit, G/T, of the TMA structure is investigated, including the details of the receiver hardware. Moreover, the G/T of the TMA is compared with that of a phased array. The comparison indicates that the TMA structure provides the same or even better performance compared to a phased array system, which demonstrates the capability of TMA in providing... 

    Beamforming in SAR satellites for nadir echo suppression

    , Article IET Radar, Sonar and Navigation ; Volume 13, Issue 3 , 2019 , Pages 420-427 ; 17518784 (ISSN) Khosravi, M ; Fakharzadeh, M ; Bastani, M. H ; Sharif University of Technology
    Institution of Engineering and Technology  2019
    Here, nadir echo suppression (NES) in synthetic aperture radar (SAR) satellites is studied in detail. Moreover, advantages of suppressing the nadir echo in space domain, by beamforming, rather than in time domain, which imposes stringent restrictions on radar timing, are addressed. Performing NES in time domain restricts the swath width, as well as the selection of the pulse repetition frequency (PRF). It is shown that the spatial NES could increase the swath width by ∼25%. It also increases the freedom in PRF selection, which is useful in multiple-swath imaging modes and high-resolution wide-swath satellites. Furthermore, it is useful in confining the operating PRF range of SAR satellites,... 

    A novel algorithm in a linear phased array system for side lobe and grating lobe level reduction with large element spacing

    , Article Analog Integrated Circuits and Signal Processing ; Volume 104, Issue 3 , 13 March , 2020 , Pages 265-275 Khalilpour, J ; Ranjbar, J ; Karami, P ; Sharif University of Technology
    Springer  2020
    Phased array antennas are generally used for the inherent flexibility to beamforming and null-steering electronically. In the phased arrays the side lobes level (SLL) level is main problem which causes waste of energy or saturation of the receiver in the case of presence of the strong spatial blockers. In this paper, a weighting method was first used to reduce the level of SLL. However, this method increased the beam width and reduced resolution, which is not suitable for track applications. In next step hoping to increase the resolution, the distance between the antennas increased. But in this way, grating lobes appeared in the final beam. In fact, the main idea of the article is to solve... 

    Co channel interference cancellation by the use of iterative digital beam forming method

    , Article Progress in Electromagnetics Research ; Volume 87 , 2008 , Pages 89-103 ; 10704698 (ISSN) Emadi, M ; Sadeghi, K. H ; Jafargholi, A ; Marvasti, F ; Sharif University of Technology
    Electromagnetics Academy  2008
    This paper deals with the possibilities of cancellation of unwanted signals by steering nulls of the pattern in the direction of arrival of signal while keeping the main beam to the desired direction. New iterative adaptive digital beam forming technique is presented here to enhance the conventional effectiveness of beam forming in common commercial application. Simulation and measurement results confirm that this algorithm can achieve effective Co-Channel Interference (CCI) suppression, while increasing the strength of the desired signal  

    Secrecy rate maximization for hardware impaired untrusted relaying network with deep learning

    , Article Physical Communication ; Volume 49 , 2021 ; 18744907 (ISSN) Bastami, H ; Moradikia, M ; Behroozi, H ; de Lamare, R. C ; Abdelhadi, A ; Ding, Z ; Sharif University of Technology
    Elsevier B.V  2021
    This paper investigates the physical layer security (PLS) design of an untrusted relaying network where the source node coexists with a multi-antenna eavesdropper (Eve). While the communication relies on untrustworthy relay nodes to increase reliability, we aim to protect the confidentiality of information against combined eavesdropping attacks performed by both untrusted relay nodes and Eve. Considering the hardware impairments (HIs), both total power budget constraint for the whole network and the individual power constraint at each node, this paper presents a novel approach to jointly optimize relay beamformer and transmit powers aiming at maximizing average secrecy rate (ASR). To... 

    Diversity and Error Probability Analysis and Determining the Effect of Non-Ideal Phase Estimation in Amplify-and-Forward and Beamforming Techniques

    , M.Sc. Thesis Sharif University of Technology Safavi, Ebrahim (Author) ; Hossein Khalaj, Babak (Supervisor)
    In this study we investigate the performance of amplify-and-forward (AF) and beamforming schemes in wireless networks. In our study we consider a general cooperative network consisting one transmit-receive pair and an arbitrary number of relays in which each relay has a separate power constraint. A two-step master-slave protocol is deployed in which at the first stage, relays listen to the transmitter and at the second stage, relays forward the recently received signal coherently. Main contributions of this dissertation are providing the exact closed-form of bit error rate analysis in the case of general AF networks, providing an integral-form upper bound of error probability of network... 

    Secure Communication via Cooperation and Cooperative Jamming

    , M.Sc. Thesis Sharif University of Technology Hatami, Mohammad (Author) ; Behroozi, Hamid (Supervisor)
    The broadcast nature of wireless communications makes the propagation medium vulnerable to security attacks such as eavesdropping and jamming from adversarial or unauthorized users. Applying physical layer secrecy approaches will enable the exchange of confidential messages over a wireless medium in the presence of unauthorized eavesdroppers, without using any secret keys. However, physical layer security approaches are typically feasible only when the source-eavesdropper channel is weaker than the source-destination channel. Cooperative jamming can be used to overcome this challenge and increase the secrecy rate. In this thesis, the security of two-phase relaying system with multiple... 

    Beamforming in SAR Satellites for Nadir Echo Suppression

    , Ph.D. Dissertation Sharif University of Technology Khosravi, Mahdi (Author) ; Bastani, Mohammad Hassan (Supervisor) ; Fakharzadeh, Mohammad (Supervisor)
    In synthetic aperture radar (SAR) satellites, the nadir echo is defined as the backscattered signal from the point directly below the satellite on the earth surface. If the timing of the radar is such that the nadir echo arrives at the receiver while the receiver is turned on for receiving the desired signal, it could damage the receiver or disrupt the resulting SAR image, unless it is suppressed enough by proper design of antenna radiation pattern. In current SAR satellites, ”avoiding” this phenomenon is associated with two problems: 1) limiting the swath width, 2) imposing stringent restrictions on the selection of pulse repeatition frequency (PRF). Therefore, ”suppressing” the nadir echo,... 

    Design of a Phased Array Receiver for 5G Applications

    , M.Sc. Thesis Sharif University of Technology Tahbaz Alli, Parsa (Author) ; Sharif Bakhtiar, Mehrdad (Supervisor)
    Next-generation wireless communication requires phased-array systems to ensure Gb/s data communication. This work demonstrates a four-element phased array receiver based on N-path filters for the 5G-FR1 frequency band. The behaviour of the circuit including non-idealities and effects due to mismatch in the paths is modeled and verified via simulations. As the time-variant nature of the N-path filter introduces multiple frequency translations, third harmonic selection of the switching frequency rather than the fundamental helps to reduce the input frequency of the multiphase clock generator by a factor of three. Therefore, the proposed structure is capable of third harmonic reception as well... 

    Non-coherent DOA Estimation Via Majorization-Minimization Using Sign Information

    , M.Sc. Thesis Sharif University of Technology Delbari, Mohamad Reza (Author) ; Marvasti, Farrokh (Supervisor)
    Direction of arrival (DOA) estimation has various applications in different areas such as wireless communication and signal processing in medical applications. Most of the previous methods were not based on digitalization, but the advantages of digitalized methods have been proved in recent decades. Furthermore, because of existing the phase error, we need to use the algorithms to find the solution with amplitude measurements. A solution method to this problem was introduced in 2015 for the first time, and then newer algorithms were proposed. However, most of them need reference signals to resolve the inherent ambiguity of the problem. By contrast, this dissertation not only does not use... 

    Optimal Scheduling in Wirelessly-powered Communication Networks

    , Ph.D. Dissertation Sharif University of Technology Movahednasab, Mohammad (Author) ; Pakravan, Mohammad Reza (Supervisor)
    In this thesis, we study optimal scheduling in a multi-hop wirelessly-powered network. We propose an online control policy for energy transfer from the energy access point to the wireless nodes and for data transfer among the nodes. With our proposed control policy, all data queues of the nodes are stable, while the average energy consumption of the network is shown to be within a bounded gap of the minimum energy required for stabilizing the network. Our proposed policy is designed using a quadratic Lyapunov function to capture the limitations on the energy consumption of the nodes imposed by their bachery levels. We show that under the proposed control policy, the bachlog level in the data... 

    Distributed synchronization and beamforming in uplink relay asynchronous OFDMA CoMP networks

    , Article IEEE Transactions on Wireless Communications ; Volume 14, Issue 6 , 2015 , Pages 3471-3480 ; 15361276 (ISSN) Pilaram, H ; Kiamari, M ; Khalaj, B. H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    In this paper, we use delay-amplify-and-forward relays in the uplink direction of a coordinated multi-point network based on orthogonal frequency division multiplexing. The key novelty is that we assume delay from users to different base stations (BSs), in general, may exceed cyclic prefix (CP) length as might be the case in large cells and cannot be completely compensated by traditional timing advance strategies. Consequently, interchannel interference and intersymbol interference may arise under such assumptions. We first optimize the adjustable delays added at users, relays and BS nodes in order to reduce the effective delay spread at the receive sites, then we optimize relays' weights...