S. Salari

Khaje Nasir Toosi University of Technology | KNTU · Faculty of Electrical and Computer Engineering

In this paper, we study the problem of joint carrier frequency offset (CFO) and sparse channel estimation in orthogonal frequency-division multiplexing (OFDM) communication systems, from the perspective of sparse Bayesian learning (SBL) framework. We first consider the problem in the compressed sensing (CS) context and reformulate it as the problem...

In this paper, we propose a new compressive sampling (CS)-based approach to detect a target and obtain its direction-of-arrival (DOA) by using samples collected by a set of sensor nodes. Since these sensors sample at a rate below Nyquist, instead of the Nyquist-rate, the complexity, power consumption, memory requirement, and the volume of data that...

In this paper, we address the problem of radar range-Doppler imaging in the presence of clutter. Specifically, we formulate the range-Doppler imaging problem as that of recovery of a sparse vector contaminated by clutter in addition to noise. We propose a sparse Bayesian learning (SBL)-based algorithm to jointly obtain the range-Doppler image, vari...

We apply the technique of compressive sensing (CS) to multiple-input multiple-output (MIMO) radars to estimate the Direction of Arrival (DOA) of potential targets embedded in cluttered environments using far fewer samples than Nyquist rate. Specifically, incorporating clutter into the sparse Bayesian learning (SBL) methodology, we devise a novel al...

This paper employs a special property of the Hadamard matrix to develop a novel compressive sensing (CS)- based framework that eliminates the complex reconstruction step required by standard CS methods. In particular, time-differenceof- e rrivals (TDOAs) of a signal at different receivers involved in positioning of unknown sources are directly esti...

In this letter, we consider a mobile wireless sensor network (WSN), in which all nodes have some knowledge about their movements. Exploiting the sensor mobility information in the localization process, we develop novel cooperative second order cone programming (SOCP)-based localization algorithms for both time-of-arrival (TOA) and received signal s...

In this paper, we consider an amplify-and-forward (AF)-based two-way relaying network, in which the relays need to harvest energy from the received radio frequency (RF) signals to remain active in the network and assist data exchange between two transceivers. In particular, considering time-switching (TS) architecture, we investigate the problem of...

This paper studies the problem of optimal beamforming and power allocation for an amplify-and-forward (AF)-based two-way relaying network in the presence of interference and channel state information (CSI) uncertainty. In particular, we obtain the beamforming vector as well as the users' transmit powers under two assumptions on the availability of...

Design of effective cooperative jamming (CJ) algorithm is studied in this paper to maximize the achievable secrecy rate when the total transmit power of the source and multiple trusted terminals is constrained. Recently, the same problem was studied in [1] and an optimal algorithm was proposed involving a one-dimensional exhaustive searching. Howev...

Background: Dermatophytosis is the common cutaneous infections in humans and animals, which is caused by the keratinophylic fungus called dermatophytes. In recent years, drugs resistance in pathogenic fungi, including dermatophyte strains to the current antifungals have been increased. Objectives: The aim of this study was to evaluate the antifu...

It is known that use of a random measurement (sensing) matrix usually results in good recovery performance via orthogonal matching pursuit. This paper provides the probability of ensuring the recovery of sparse signals using orthogonal matching pursuit for the case where all entries of the measurement matrix are independently selected from a Gaussi...

In this paper, considering a mobile wireless sensor network, we study the problem of exploiting sensor mobility information in the process of sensor localization under two range measurement models, namely the time-of-arrival (TOA) model and the received signal strength (RSS) model. To do so, for each model, we first derive the maximum likelihood (M...

In this study, the authors consider the problem of cooperative spectrum sensing (CSS) based on linear combination of observations over correlated log-normal shadow-fading channels. To reduce the effects of imperfect reporting channels, a cluster-based CSS framework and a new cluster head selection algorithm are proposed. Using the received energies...

In collaborative spectrum sensing, the presence of the primary user is detected at a central entity, known as the fusion center. This center collects the information from the secondary users and decides on the occupancy of the desired frequency band. In the conventional strategy, the secondary users transmit their initial observations toward the fu...

A cooperative bidirectional relaying scheme based on relay beamforming is proposed for an underlay cognitive relay network (CRN) which consists of two secondary transceivers and K cognitive relay nodes and a primary network (PN) with a transmitter and receiver, all equipped with single antenna. The result of incoordination between PN and SN is that...

In this paper, based on two different signal models, two different maximum-likelihood (ML) schemes for joint carrier frequency offset (CFO), timing ambiguity, and channel estimation in multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems have been proposed. The first scheme jointly estimates the timing off...

In this paper, we investigate the problem of carrier frequency-offset (CFO) synchronization and channel estimation in multiple-input multiple-output orthogonal frequency-division multiplexing systems operating over unknown frequency-selective fading channels. We first propose a novel joint CFO and channel estimator, assuming time-domain training bl...

In this study, the authors consider the problem of distributed relay beamforming in an underlay-based cognitive relay network in which a secondary network transmits its data using multiple relays under an amplify-and-forward protocol simultaneously with a primary network over the same spectrum. For such a network, assuming that the partial channel...

In this paper, we study the design of expectation-maximization (EM)-based iterative receivers for low-density parity check -coded multiple-input multiple-output orthogonal frequency-division multiplexing systems with the presence of carrier-frequency offset (CFO). First, starting from the maximum-likelihood principle, we devise a novel EM-based pil...

In this paper we considered a non-redundant linear precoding blind channel estimation method for orthogonal frequency-division multiplexing (OFDM) system and proposed an improved algorithm to achieve better performance. A wide range of blind channel estimation methods are based on the covariance matrix of received symbols. In practice, the covarian...

In this paper we considered a non-redundant linear precoding blind channel estimation method for orthogonal frequency-division multiplexing (OFDM) system and proposed an improved algorithm to achieve better performance. A wide range of blind channel estimation methods are based on the covariance matrix of received symbols. In practice, the covarian...

In this paper we considered a non-redundant linear precoding blind channel estimation method for orthogonal frequency-division multiplexing (OFDM) system and proposed an improved algorithm to achieve better performance. A wide range of blind channel estimation methods are based on the covariance matrix of received symbols. In practice, the covarian...

In this paper, two novel approaches to filter-and-forward beamforming (FF-BF) in an underlay based relay-assisted cognitive network with frequency-selective channels are proposed. In our scheme, secondary users are allowed to transmit through multiple relays simultaneously with primary users over the same spectrum. Such a network suffers from both...

In this paper, we investigate the problem of carrier frequency-offset (CFO) synchronization and channel estimation in orthogonal frequency-division multiple access (OFDMA) systems operating over unknown frequency-selective fading channels. We first devise a novel iterative method for joint CFO and channel estimation, based on the time-domain traini...

In this paper, a novel approach to filter-and-forward relay beamforming in an underlay based cognitive two-way relay network with frequency selective channels is proposed. In our scheme, two secondary transceivers communicate which other through multiple relays simultaneously with the primary network transmission over same spectrum. Such a network...

In this paper, we propose a distributed relay beam-forming design in an underlay based cognitive relay network. In the proposed approach, beamforming coefficients of the secondary relays are obtained through minimization of the peak interference power inflicted on the primary receiver subject to the signal to noise-interference ratio (SINR) constra...

In this paper, we propose an Amplify-and-Forward (AF) Orthogonal Frequency Division Multiplexing (OFDM) relay scheme that each relay superimposes its own pilot symbol (PS) such that, individual relay channels can be estimated at the destination. We derive optimal PS designs including both Modification Diagonal Matrix (MDM) and superimposed PS at ea...

In this study, the authors consider a multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing system operating over unknown frequency-selective fading channels. Based on two different signal models, two maximum-likelihood schemes for joint carrier frequency offset (CFO) and MIMO channel estimation under timing ambiguity hav...

This paper investigates the problem of interference minimization which restricts the secondary users (SUs) quality of service (QoS) while coexisting the primary users (PUs), using distributed beamforming for a bidirectional cognitive relay network. We consider a network which consists of two secondary transceivers and K cognitive relay nodes and a...

In this paper, we propose a multiple relay selection scheme, which allocates the global power optimally to best relays which are selected to maximize signal to noise (SNR) ratio. First, all available relays are sorted from the highest priority to the lowest priority to cooperate in transmission by using the idea of relay ordering. Then, the total r...

Cooperative diversity has been recently proposed as a technique to form virtual antenna arrays in systems with single-antenna nodes. The Amplify-and-Forward (AF) relaying strategy is one of the most popular cooperative diversity schemes due to its low complexity. Selection AF (SAF) relaying, single or multiple relay selection, has recently been pro...

Energy detection has been adopted as an alternative spectrum sensing method for cognitive radios due to its low computational complexity and not requiring a priori information of the signal to be detected [1]. However, different channel condition and noise power estimation in low Signal-to-noise ratio (SNR), make energy detection practically challe...

Several Challenges like low signal-to-noise ratio (SNR), fading and inaccuracy in noise power estimation make spectrum sensing techniques not reliable enough to sense the presence of primary signals accurately. These challenges substantiate the application of more robust algorithms by multiple cognitive users. Recently, Cooperative spectrum sensing...

In this paper, the problem of cooperative spectrum sensing in cognitive radio networks based on linear combination of local observations is considered. In particular, log-normal shadow-fading is considered in both sensing and reporting channels. To reduce the effects of imperfect channel conditions, a clustering algorithm is suggested in which fina...

In this paper, we consider the cooperative spectrum sensing when the links between primary user and CRs are subject to log-normal shadow fading and there is also noise uncertainty which is modeled as log-normal. The objective is to evaluate the performance of Equal Gain Combining (EGC) of local observations and propose a novel cluster-based algorit...

The problem of joint carrier frequency offset (CFO) and channel estimation in orthogonal frequency division multiplexing (OFDM) systems is investigated in this study. The exact solution to this problem turns out to be too complex for practical purposes. To overcome this difficulty, we resort to the recursive least square (RLS) algorithm and propose...

New method for equalization and symbol detection for 8-PSK EDGE system is investigated in this study. The exact solution to this problem, Maximum Likelihood Sequence Estimation (MLSE) turns out to be too complex for practical purposes, but this method introduce a new version of Delayed Decision Feedback Sequence Estimation (DDFSE) equalizer that ha...

The problem of blind channel estimation in Multiple-Input-Multiple-Output (MIMO) Orthogonal Frequency-Division Multiplexing (OFDM) systems is investigated in this study, assuming that the transmitted symbols are independent and identically distributed. In particular, by utilizing a generalized linear non-redundant precoder, a simple blind channel e...

The objective of cooperative spectrum sensing is to collaboratively detect the presence of the primary user by the aid of multiple secondary users. It is known that the performance of such a framework substantially depends on the fading assumption. In this paper, we propose an advanced framework for linear cooperative spectrum sensing in cognitive...

In this paper, we propose a multiple relay selection scheme, which allocates the global power optimally to best relays which are selected to maximize signal to noise (SNR) ratio. First, all available relays are sorted from the highest priority to the lowest priority to cooperate in transmission by using the idea of relay ordering. Then, the total r...

In this study, the problem of blind channel estimation for single-input single-output (SISO) orthogonal frequency-division multiplexing (OFDM) systems, is considered. Based on auto-correlation matrix, we develop a precoding-assisted blind channel estimation algorithm which is suitable for practical SISO-OFDM applications. Compared to the popular su...

The key enabling functionality of a cognitive radio is to ensure that it would not interfere with primary users, by reliably detecting primary user signals. Due to the low computational complexity, Energy detector is a widely used spectrum sensing method. The performance of energy detector in fading channels has been previously analyzed in some pap...

In this paper, we consider design optimization of low-density parity-check (LDPC) coded multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems for high data rate wireless transmission. First, starting from the maximum-likelihood (ML) principle, we devise a novel expectation-maximization (EM)-based scheme for...

In this paper, we consider a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system operating over unknown frequency-selective fading channels. Joint maximum-likelihood (ML) estimation of carrier frequency offset (CFO) and MIMO channel coefficients is prohibitively complex for practical purposes. To overcome...

In this study, we present a new reduced-complexity scheme for maximum-likelihood (ML) estimate of both carrier-frequency offset (CFO) and channel coefficients in multi antenna OFDM transmission, assuming that a training sequence is available. Our scheme is also capable to accommodate any space-time coded (STC) transmission. Moreover, to benchmark t...

In this chapter, we propose a new scheme for maximum-likelihood (ML) estimation of both carrier-frequency offset (CFO) and channel coefficients in multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems, assuming that a training sequence is available. Our scheme is also capable to accommodate any space–time c...

Fusarium species have been frequently reported as etiologic agents of opportunistic infections such as onychomycosis in humans. We report a case of a distal onychomycosis due to Fusarium spp. in the region of Kerman in Iran. The infection occurred in a man with finger squamous cell carcinoma. Nail specimen was examined by direct microscopy, culture...

In this paper, we consider a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system operating over frequency-selective fading channels. We propose a novel scheme for joint carrier-frequency offset (CFO) and channel estimation based on the expectation–maximization (EM) algorithm. Furthermore, the Cramer-Rao bo...

The problem of joint maximum-likelihood estimation of the carrier-frequency offset (CFO) and channel coefficients in multiple-input multiple-output orthogonal frequency-division multiplexing systems is investigated, assuming that a training sequence is available. The exact solution to this problem turns out to be too complex for practical purposes....

In this study, we present a new reduced-complexity scheme for Maximum-Likelihood (ML) estimate of both Carrier-Frequency Offset (CFO) and channel coefficients in multi antenna OFDM transmission, assuming that a training sequence is available. Our scheme is also capable to accommodate any Space-Time Coded (STC) transmission. Moreover, to benchmark t...

The design of expectation-maximisation (EM)-based turbo receivers for low-density parity-check-coded multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems with the presence of carrier-frequency offset (CFO) is studied. First, starting from the maximum-likelihood principle, a novel EM-based CFO estimator for...

Repeat of preamble is a usual method for time and frequency synchronization in a large group of multicarrier systems. The essential drawback of this method is reduction of maximum estimated frequency offset range with increasing the length of preamble. Recently, Zhang et al. proposed a method for joint frame synchronization and carrier frequency of...

In this paper, we propose a new scheme for joint maximum- likelihood (ML) estimation of carrier-frequency offset (CFO) and channel coefficients in multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. To reduce the prohibitive computational complexity of joint ML estimation problems, the expectation- maxim...

A maximum-likelihood estimator (MLE) based on the expectation-maximization (EM) algorithm is presented to estimate the carrier frequency offset (CFO) in multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. This MLE estimator is also capable to accommodate any space-time coded (STC)-OFDM transmission. Then...

In this paper, we propose a new scheme for maximum-likelihood (ML) estimation of both carrier- frequency offset (CFO) and channel coefficients in multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. To reduce the prohibitive complexity of ML estimate, the expectation-maximization (EM) algorithm is employe...

In this paper, we consider carrier-frequency offset (CFO) estimation issue in a multiple-input multipleoutput (MIMO) orthogonal frequency division multiplexing (OFDM) system using low-density paritycheck (LDPC) codes at transmitter and iterative detection based on the maximum a posteriori expectation-maximization (MAP-EM) demodulator and a soft LDP...

Multiple-input multiple-output (MIMO) systems combined with orthogonal frequency division multiplexing (OFDM), can improve communication quality and capacity. In this paper, we consider channel estimation issue in a MIMO-OFDM system using low-density parity-check (LDPC) codes at transmitter and iterative detection based on a maximum a posteriori (M...

In this paper, we consider a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system operating over unknown frequency selective fading channels. We propose a novel scheme to obtain frequency synchronization together with multi-antenna channel estimation. Computer simulation results are provided to demonstrate...

This paper proposes an iterative maximum a posteriori probability (MAP) receiver for low-density parity-check (LDPC)-coded multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems with the presence of carrier-frequency offset (CFO). The turbo receiver employs the expectation maximization (EM) algorithm so as t...