Publication Date: 2020
Journal Of Medical Signals And Sensors (22287477)10(1)pp. 53-59
Obstructive sleep apnea (OSA) is a common disorder which can cause periodic fluctuations in heart rate. To diagnose sleep apnea, some studies analyze electrocardiogram (ECG) signals by adopting chaos-based analysis. This research is going to specifically focus on whether it is possible to use chaos-based analysis of heart rate variability (HRV) signals rather than using chaotic analysis of ECG signals to diagnose OSA. While conventional studies mostly use chaos-based analysis of ECG signals to detect OSA, here, we apply correlation dimension (CD) as a chaotic index to analyze HRV data in OSA patients. For this purpose, 17 patients with OSA and 9 healthy individuals referred to a sleep clinic in Isfahan/Iran are studied, and their HRV time series were extracted from 1-h ECG signals recorded overnight. The preliminary step to calculate CD is phase-space reconstruction of the system based on HRV time series. Corresponding parameters, including embedding dimension and lag time, are estimated optimally using enhanced related methods, and then CD is calculated using Grassberger-Procaccia algorithm. Moreover, to evaluate our results, detrended fluctuation analysis (DFA), one of the well-known nonlinear methods in HRV analysis to detect OSA, is also applied to our data and the result is compared with those obtained from CD analysis of HRV. CD index with P < 0.005 indicates a significant difference in nonlinear dynamics of HRV signals detected from OSA patients and healthy individuals. © 2020 Isfahan University of Medical Sciences(IUMS). All rights reserved.
Publication Date: 2019
Microelectronic Engineering (01679317)216
This paper presents an ultra-low-power CMOS amplifier for Low-frequency biosignal recording applications, especially for implantable biosensors and wearable or portable devices such as wearable electrocardiogram (ECG) recording microsystems that power consumption and on-chip area are the critical constraints. The proposed amplifier consists of two stages. In the first stage, a current reuse topology is used to achieve a lower input-referred voltage noise power density compared to a normal single-ended common source amplifier. In order to reduce the on-chip area, an inverter based amplifier with high output impedance is used at the output stage of the circuit to reduce the area occupied by the large load capacitance, which is required for having low cut off frequency of 200 Hz. Using this technique, the required load capacitance is decreased to about 2.1 pF. To reduce the power consumption, a ± 0.6 V supply voltage is used, and the transistors are pushed toward sub-threshold region to reduce the bias currents to about 260 nA in the first and the second stages. To validate the design, the proposed amplifier is simulated using 0.18 μm TSMC CMOS technology with Cadence in post-layout level. It is shown that the total power consumption of the proposed amplifier is as low as 640 nW. The proposed amplifier benefits from a CMRR >125 dB, total input-referred noise of 6.1 μVrms in 200 Hz bandwidth for ECG signal recording, and a closed-loop gain of about 35.1 dB. The layout of the circuit occupies a total area of 0.034 mm2. © 2019 Elsevier B.V.
Publication Date: 2019
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS (1557170X)pp. 302-304
Patients with implantable cardioverter-defibrillator (ICD) are at the risk of electrical storm (ES) occurrence associated with mortality and poor quality of life. Cardiac resynchronization therapy with defibrillator (CRT-D) minimizes inappropriate ICD shocks. However, limited reports exist on the impact of CRT-D versus traditional ICD on ES occurrences in real-life cohorts. We evaluated the implanted-device characteristics associated with ES events in a large data based on daily stored device-summaries obtained from remote monitoring data in US.Between 2004 and 2016, 19,935 US patients were implanted. Survival analyses with Cox regression for device-shock therapy were performed between patients who experienced at least one ES and those without ES. CRT-D devices (bi-ventricular) were implanted in 5522 (28%) patients during this period, and their ES events over time were compared to ICD recipients implanted with RV lead. Primary endpoint was the first ES event.ES occurred with the rate of 7.26% for all patients during the period. Cox regression analyses revealed significantly an increase risk in ES occurrences (the p-value < 0.05 and hazard ratio >> 1) with shock therapy. CRT-D implant led to lower ES risk comparing with patients received traditional ICD (RV only). © 2019 IEEE.
Publication Date: 2019
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS (1557170X)pp. 4885-4888
Electrical storm (ES) is a life-threatening heart condition for patients with implantable cardioverter defibrillators (ICDs). ICD patients experienced episodes are at higher risk for ES. However, predicting ES using previous episodes' parameters recorded by ICDs have never been developed. This study aims to predict ES using machine learning models based on ICD remote monitoring-summaries during episodes in the anonymized large number of patients.Episode ICD-summaries from 16,022 patients were used to construct and evaluate two models, logistic regression and random forest, for predicting the short-term risk of ES.Episode parameters in this study included the total number of sustained episodes, shocks delivered and the cycle length parameters. The models evaluated on the data sections not used for model development.Random forest performed significantly better than logistic regression (P < 0.01), achieving a test accuracy of 0.99 and an Area Under an ROC Curve (AUC) of 0.93 (vs. an accuracy of 0.98 and an AUC of 0.90). The total number of previous sustained episodes was the most relevant variables in the both models. © 2019 IEEE.
Publication Date: 2017
Computing in Cardiology (2325887X)44pp. 1-4
Hypertension or high blood pressure (BP) is one of the most common worldwide disease leading to heart attack or stroke. Continuous assessment of blood pressure level is key to diagnosing hypertension. In this study, we designed and tested a dedicated cuff-less monitoring system which estimates BP level without need for calibration. We obtained continuous measurements from 40 healthy subjects (30 males and 10 females) ranging from 20-30 years old. Our measurement protocol consisted of 15 minutes simultaneous electrocardiography (ECG) and photoplethysmography (PPG) within three sessions, i.e. rest, bicycle exercise, and recovery. From ECG and PPG signals, we obtained 34 candidate features from which up to 9 features were selected to estimate systolic and diastolic BP levels. We validate our results with three regression models such as linear regression, support vector machines (SVM) regression, and multilayer perceptron (MLP) to obtain the best results. The study provides a promising approach for modern cuff-less BP monitoring devices. © 2017 IEEE Computer Society. All rights reserved.
Publication Date: 2016
Indian Journal of Science and Technology (discontinued) (09746846)9(16)
Neural micro-probing not only allows us to access the brain signals, it is also one of the key tools to achieve a better understanding of the fundamental mechanisms of the brain and nervous system. This knowledge is extremely essential to implement complex neuralprosthetics. Considering the importance of the size, power consumption, and accuracy, in this Paper, a compact, low-power eight-channel implantable neural recording microsystem is presented. To this end, Time Division Multiplexing (TDM) method is used for multiplexing 8 input channels. Thus, only one Analog to Digital Converter (ADC) block is used, resulting in a small circuit size and low power consumption. Also, a new structure of Amplitude-Shift Keying (ASK) modulation technique with simple configuration and low power consumption is proposed and applied. This system is designed in TSMC 0.18 μm CMOS technology with 1.8 V power supply and simulated with HSPICE. The total power consumption of the system is measured to 2 mW. Neural signals recorded from auditory cortex of a guinea pig are used as the inputs of the eight channels of the system. Total RMS error between inputs and outputs caused by the system is 2.8%.
Publication Date: 2015
Journal of Isfahan Medical School (10277595)33(335)
Background: Neonatal jaundice is a common disease, and has been seen in almost 60% of term and 80% of preterm infants. There are three methods of assessing bilirubin level, visual, cutaneous and serum measurement. Method of measuring serum bilirubin, due to blood sampling from the baby, is not ideal. Visual assessment method is not an accurate criterion. So, the researchers looked for a way to measure bilirubin level non-invasively. In 1980, the first review was done and high correlation was found between the skin bilirubin level and the amount of bilirubin in serum. Some of noninvasive bilirubinmeter devices poorly acted in heterogeneous groups in terms of gestational age and races. Some of the newer methods, for each infant, need an initial correction. The latest method of measuring skin bilirubin uses the reflection of the wide spectrum of visible light. Methods: We intended the designing and construction of a noninvasive neonatal jaundice meter, using newest methods and designs. In this device, light, with five different wavelengths, transmitted to the skin and after measuring the reflection from baby’s skin, the bilirubin concentration in terms of mg/dl could be obtained. Findings: Clinical testing of the device was done on 32 infants; and correlation of 74%, between the transcutaneous (TCB) and the total serum bilirubin (TSB) values was obtained. Conclusion: An acceptable correlation was obtained between the transcutaneous and the total serum bilirubin values. The device can be used to screen newborns for measurement of bilirubin with decreased number of blood samples. © 2015, Isfahan University of Medical Sciences(IUMS). All rights reserved.
Publication Date: 2014
Journal of Isfahan Medical School (10277595)32(283)pp. 558-568
Background: Electroencephalogram (EEG) shows the electrical activity of the brain and is one of the most important diagnostic tools for neurological diseases and disabilities. Dysgraphia is one of the most common learning disabilities occurs regardless of the ability to read and is not due to intellectual impairments. Nonlinear methods are used in recent studies to access the electroencephalogram in children with dysgraphia.
Publication Date: 2012
Noise and Health (14631741)14(59)pp. 135-139
Noise may be defined as any unwanted sound. Sound becomes noise when it is too loud, unexpected, uncontrolled, happens at the wrong time, contains unwanted pure tones or unpleasant. In addition to being annoying, loud noise can cause hearing loss, and, depending on other factors, can affect stress level, sleep patterns and heart rate. The primary object for determining subjective estimations of loudness is to present sounds to a sample of listeners under controlled conditions. In heating, ventilation and air conditioning (HVAC) systems only the ventilation fan industry (e.g., bathroom exhaust and sidewall propeller fans) uses loudness ratings. In order to find satisfaction, percent of exposure to noise is the valuable issue for the personnel who are working in these areas. The room criterion (RC) method has been defined by ANSI standard S12.2, which is based on measured levels of in HVAC systems noise in spaces and is used primarily as a diagnostic tool. The RC method consists of a family of criteria curves and a rating procedure. RC measures background noise in the building over the frequency range of 16-4000 Hz. This rating system requires determination of the mid-frequency average level and determining the perceived balance between high-frequency (HF) sound and low-frequency (LF) sound. The arithmetic average of the sound levels in the 500, 1000 and 2000 Hz octave bands is 44.6 dB; therefore, the RC 45 curve is selected as the reference for spectrum quality evaluation. The spectral deviation factors in the LF, medium-frequency sound and HF regions are 2.9, 7.5 and-2.3, respectively, giving a Quality Assessment Index (QAI) of 9.8. This concludes the QAI is useful in estimating an occupant′s probable reaction when the system design does not produce optimum sound quality. Thus, a QAI between 5 and 10 dB represents a marginal situation in which acceptance by an occupant is questionable. However, when sound pressure levels in the 16 or 31.5 Hz octave bands exceed 65 dB, vibration in lightweight office construction is possible.
Publication Date: 2011
Biomedizinische Technik (1862278X)56(3)pp. 167-173
This paper presents a new modification to the previous model of bone surface remodeling under electric and magnetic loadings. For this study, the thermo-electro-magneto-elastic model of bone surface remodeling is used. This model is modified by considering an important phenomenon occurring in living bone through its adaptation to external loadings called desensitization. In fact, bone cells lose their responsiveness and sensitivity to long-term external loadings, i.e., they become desensitized. Therefore, bone cells need a recovery period, during which they become resensitized. In this work, this phenomenon is considered in the original model. The effects of various electric and magnetic loading conditions, including various frequencies, waveforms and pulse duty cycles, are explored on the modified model and compared to the original model. The modified model is also searched for the optimal frequency and duty cycle, to obtain the best bone growth response under electromagnetic fields. The results of this paper show that the modified model is consistent with experimental observations. In addition, it is indicated that this modified model in contrast to the original model, is sensitive to frequency. It is shown that the optimal frequency of loading for the modified model is 1 Hertz (Hz), and the pulse duty cycles up to 50% are sufficient for bone remodeling to reach its maximum value. © 2011 by Walter de Gruyter Berlin Boston.
Publication Date: 2009
IFMBE Proceedings (16800737)25(4)pp. 1127-1130
In recent decades, bone fracture healing methods have been the subject of many researches. According to many clinical studies, it is proved that bone healing can be promoted by application of electric and electromagnetic field in specific amplitudes, wave shapes and frequencies. In addition to clinical experiments, many mechanical models have been proposed to simulate effects of mechanical loadings on bone healing. But only a few of these models considered the electric properties of bone. In this paper, a model of piezoelectromagnetic bone has been simulated and modified based on electromagnetoelastic theory. The effects of pulsed and sine waveforms, and different constant electric and magnetic loadings on bone are investigated. It is demonstrated that electric and magnetic loadings affect bone surface remodelling. Besides, the effects of pulse width of electric and magnetic fields on bone remodelling were evaluated. Although this model can describe the process of bone surface remodelling under electric and magnetic loadings, it cannot explain some events in bone surface remodelling such as importance of rest durations after each physiotherapeutic procedure.
Publication Date: 2007
Scientia Iranica (23453605)14(6)pp. 571-578
One of the most important challenges in automatic speech recognition is the case of mismatch between training and test data. Conventional methods for improving recognition robustness seek to eliminate or reduce the mismatch, e.g. enhancement of the speech by adapting the statistical models. Training the model in different situations is another example of these methods. The success with these techniques has been moderate compared to human performance. In this paper, an inspiration from human listeners created the motivation to develop and implement a new bidirectional neural network. This network is capable of modeling the phoneme sequence, using bidirectional connections in an isolated word recognition task. This network can correct the phoneme sequence obtained from the acoustic model to what is learned in the training phase. Acoustic feature vectors are enhanced, based on the inversion techniques in neural networks, by cascading the lexical and the acoustic model. Speech enhancement by this method has a remarkable effect in eliminating mismatch between the training and test data. The efficiency of the lexical model and speech enhancement was observed by a 17.3 percent increase in the phoneme recognition correction ratio. © Sharif University of Technology, December 2007.
Publication Date: 2005
Proceedings - International Conference on Tools with Artificial Intelligence, ICTAI (10823409)2005pp. 11-18
Multi-Agent systems has generated lots of excitement in recent years because of its promise as a new paradigm for conceptualizing, designing, and implementing software systems. One of the most important aspects of agent design in AI is the way agent acts or responds to the environment that the agent is acting upon. An effective action selection and behavioral method gives a powerful advantage in overall agent performance. We define a new method of action selection based on probability/priority models in RoboCup Soccer Simulation League[6] and for simulated soccer agents, we thereby introduce an efficient way to determine probabilities and a new priority based system which maps the human knowledge to action selection method. Furthermore, a behavior model is introduced to make the model more flexible. © 2005 IEEE.
Publication Date: 2024
IEEE Transactions on Transportation Electrification (23327782)10(4)pp. 8235-8245
In this article, a transactive-based scheduling approach is proposed to optimize electric vehicle (EV) charging/discharging scheduling taking into account the technical requirements of EVs with different state-of-charge (SOC) levels and EV owners' preferences. In the proposed approach, an EV aggregator (EVA) solves an optimization problem to determine the charging/discharging schedule of each individual EV in the EV Parking Lot (PL) in which the response curves of individual EVs are used to consider the EV owners' charging/discharging preferences. Then, the EVAs provide their optimum day-ahead bids to the corresponding DSO based on calculated distribution locational marginal prices (DLMPs). The DSO's transactive market-clearing procedure is simulated to iteratively calculate DLMPs in the local distribution area (LDA) nodes. The Monte Carlo (MC) scenarios are used to model the uncertainties associated with the EVs' parameters and the driving behavior of the EV owners. Also, the robust optimization method is used to model the uncertainties associated with LMPs of the transmission network (TN) bus, distributed renewable energy resources (DRERs), and load demand. The proposed model is implemented on the modified IEEE-33 node distribution system and the effectiveness of the model is investigated and presented. © 2024 IEEE.
Publication Date: 2023
IEEE Transactions on Power Systems (0885-8950)38(2)pp. 1894-1905
In this paper, a robust distribution system expansion planning (DSP) approach is presented to supply the load growth locally and move toward nearly zero energy local distribution areas (LDAs). In the proposed approach, a distribution system operator (DSO) is responsible for secure and optimum operation of LDAs. Therefore, investors on distribution system upgrades use this approach to maximize the profit on investments by determining the installation year of new distribution feeders and energy resources, distributed energy resource (DER) placements and sizes considered by corresponding DSOs. The accurate AC power flow solution is used and mathematical methods are developed to model the DSP as a quadratically constrained programming (QCP) problem. The Benders decomposition is applied to investigate the reliability and the optimality of the proposed plan and correspondingly modify the investment plan as required. The uncertainty of renewable DER forecast errors, locational marginal price (LMP) of an LDA at a transmission bus, and transactive power associated with a load bus is modeled using robust optimization. The proposed transactive DSP (TDSP) approach is implemented on the IEEE 33-bus distribution test system and the results are analyzed and validated. The proposed numerical results show the optimality and the robustness of the proposed approach. © 1969-2012 IEEE.
Publication Date: 2022
IET Renewable Power Generation (17521416)16(15)pp. 3368-3383
The electric industry is developing towards a more efficient, reliable, and resilient electric power network. In this way, utilizing distributed energy resources (DERs), especially renewable DERs (RDERs) are a paradigm change. DERs offer many advantages in power systems, including transmission loss reduction, environmental benefits of RDERs, and enhancement of security, reliability, and resiliency of the network. However, high penetration of DERs increases uncertainty and challenges the efficient and reliable operation of the power system. This paper provides a thorough review of the transactive distribution platform which is essential to address the aforementioned challenges. This distribution platform includes a transactive distribution system operator providing a seamless and coordinated control to dynamically balance supply and demand and follow uncertain generations of RDERs. Indeed, this review paper highlights the capability of transactive energy (TE) by considering its key aspect in providing energy sharing opportunities for the integration of DERs into smart grids (SGs). TE is acombination of economic and control methods that enable optimum, reliable, sustainable, and efficient operation of SGs. Furthermore, a fully transactive framework offers more choices for DERs to control and manage the energy transactions in the retail market, as well as improves the inter operability among various market players. © 2022 The Authors. IET Renewable Power Generation published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
Publication Date: 2019
IET Generation, Transmission and Distribution (17518687)13(21)pp. 4987-4997
The main motivation of this study is to address the challenges due to high penetration of renewable distributed energy resources (DERs) and efficiently benefit from DERs in distribution system planning (DSP). This paper considers a decentralized enhanced platform for DSP which is coordinated with bulk power system planning (PSP) to keep the optimality and security of the whole power system. In the proposed coordinated approach, distribution system operators (DSOs) plan and operate DERs to upgrade their local distribution areas (LDAs), supply forecasting local load growth, and avoid or defer costly generation and transmission expansion planning at the bulk power system. The proposed DSP model consists of two main loops pertaining to the DSO's planning and operation in the first loop and the ISO's simulated operation in the second loop. The Benders decomposition (BD) is employed to iteratively solve the problems. The robust and stochastic programming are used for modelling uncertainties. The DSP problem is modelled as a mixed-integer linear problem (MILP). The CPLEX solver in GAMS is applied to the modified 24-bus IEEE RTS in a 10-year horizon for numerical validation. The results show the performance of the proposed approach in reducing the total cost of supplying growing loads. © The Institution of Engineering and Technology 2019.
Publication Date: 2018
IEEE Transactions on Smart Grid (1949-3053)9(6)pp. 6692-6701
Distribution system operator (DSO) has traditionally been responsible for the reliable operation of power distribution systems. The advent of distributed energy resources (DERs) and microgrids in distribution networks has required a new platform for DSOs. The new DSO, which is for the most part an independent agent, is responsible for aggregating a widely dispersed DERs (which include small thermal generation units, energy storage, and demand response) and flexible loads in electricity markets. DSO coordinates and balances the transactive dispatch of supply and demand at the distribution level and links wholesale and retail electricity markets. In this paper, a framework for the day-ahead transactive market is proposed which includes end-to-end power system participants starting from the bulk power ISO and ending at DSO, which includes the management of retail customers with small loads. In this paper, DERs are considered in a local distribution area (LDA). The day-ahead transactive scheduling of LDA is modeled as an MILP and solved using the CPLEX solver. This paper offers numerical results considering a DSO that is responsible for the optimal and secure operation of LDA with microgrids. The simulation results show that the proposed DSO framework in a transactive market can efficiently reduce the supply cost of LDA and increase the GenCos' payoff considering the optimal power exchange with the ISO. © 2010-2012 IEEE.
Publication Date: 2010
Advances in Electrical and Computer Engineering (18447600)10(4)pp. 143-148
Development of distribution network and power consumption growth, increase voltage drop on the line impedance and therefore voltage drop in system buses. In some cases consumption is so high that voltage in some buses exceed from standard. In this paper, effect of the fuel cell and photovoltaic hybrid system on distribution network for solving expressed problem is studied. For determining the capacity of each distributed generation source, voltage limitation on the bus voltages under different conditions is considered. Simulation is done by using DIgSILENT software on the part of the 20 kV real life Sirjan distribution system. In this article, optimum location with regard to system and environmental conditions are studied in two different viewpoints. © 2010 AECE.
Publication Date: 2021
IEEE Communications Letters (10897798)25(12)pp. 3970-3974
In this letter, we modify the multi-threshold detector (MTD) for detection of downlink non-orthogonal multiple access (NOMA) signals in the Rician fading channel with statistical knowledge of channel state information (CSI). First, the error probability (Pe) for both MTD and successive interference cancellation (SIC) with statistical CSI is calculated. Then, we use the obtained Pe expression to fairly allocate power to different users in the sense that the maximum Pe of the users is minimized. Finally, computer simulations are performed, which show that MTD outperforms the SIC in the case that error propagation happens in the noise-free SIC. © 1997-2012 IEEE.
Publication Date: 2021
Vehicular Communications (22142096)29
In this paper, we derive an analytical expression for the bit error probability of a multi-threshold (MTh) detector in the downlink three-user non-orthogonal multiple access (NOMA) based vehicular communication system with unknown noise. The MTh detector directly detects the signal of vehicle user with the highest channel gain without detecting the signals of weaker users and removing their effects. It is shown that the bit error probability performance of the MTh detector is superior to that of the successive interference cancellation (SIC) detector in a special case. Then, we propose a blind empirical characteristic function (ECF) based method to estimate the signal levels of vehicle users, required to implement the MTh detector, in unknown noise. Next, we derive an analytical expression for the variance of the proposed ECF-based estimator which is validated via computer simulations. It is shown that the ECF-based estimator is asymptotically unbiased and consistent. Furthermore, we obtain the normalized Cramér-Rao lower bound (NCRLB) for the estimators of signal levels which shows that the ECF-based estimator is almost efficient in small generalized signal-to-noise ratio (GSNR) values. Numerical results show that the ECF-based MTh detector outperforms the absolute median-based SIC detector in the mixture of Gaussian and α-stable noise. © 2020 Elsevier Inc.
Publication Date: 2021
IEEE Signal Processing Letters (10709908)28pp. 1868-1872
In this paper, an empirical characteristic function (ECF) based estimator of the line-of-sight (LOS) power for the near user in an uplink non-orthogonal multiple access (NOMA) system with unknown impulsive noise is proposed. The channels between the users and the base station (BS) are assumed to have Rician fading. The performance of the proposed estimator is analytically evaluated, which demonstrates the asymptotic unbiasedness and consistency of the estimator. Furthermore, the approximate expression derived for the variance is confirmed through computer simulations. Numerical results show that the proposed estimator outperforms the previous estimator for the LOS power in the mixture of Gaussian and α-stable noise. © 1994-2012 IEEE.
Publication Date: 2020
Wireless Networks (10220038)26(5)pp. 3521-3537
Vehicular ad hoc networks (VANETs) are able to facilitate data exchange among vehicles and provide diverse data services. The benefits of cooperative communications are such as to make it a proper idea to improve the achievable rate and diversity in VANETs. We investigate a dual-hop relay vehicular network with different transmit powers in vehicles on non-uniform shadowed double Nakagami-m fading channels in the presence of non-uniform co-channel interferers. In this paper, we investigate the diversity-multiplexing tradeoff (DMT) in such a network for three different schemes, namely, dynamic decode and forward (DDF), dynamic quantize map and forward and static quantize map and forward and prove that the DDF strategy has the optimal DMT. Also, the optimal listening and transmitting time of vehicles in various strategies as a function of the channel conditions in vehicles are determined. Finally, we extend our results to a general multi-hop relay vehicular network model with multiple half-duplex relay terminals and different average SNRs over links. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
This paper studies the diversity-multiplexing trade-off (DMT) of half-duplex diamond relay channels. Diversity and multiplexing gains usually evaluate the performance of any relaying strategy, in wireless relay networks with fading channels. DMT captures the fundamental trade-off between these two gains, for communications at high signal to noise ratios (SNR). In this paper, we propose an efficient algorithm that computes the DMT of static-QMF communication strategy in half-duplex diamond relay channels. To find DMT of static QMF, one needs to solve a cumbersome optimization problem. The proposed algorithm, breaks the given optimization to finite1 number of sub-optimization problems, each one of which is a quasi-concave optimization problem. Then, using a binary search method, each sub-optimization problem is solved efficiently and the results of sub-optimization problems are combined to find DMT of the static QMF communication in the network. © 2016 IEEE.
Publication Date: 2015
IEEE Communications Letters (10897798)19(8)pp. 1295-1298
A simple asymptotic bound on the error of the ordinary normal approximation (ONA) to the Student's t-distribution is derived. The proposed bound provides a quick calculation of the minimum number of degrees of freedom required to ensure a given approximation error. Then, the application of the ONA is investigated in confidence interval determination and detection theory. Finally, using the proposed bound, further simple bounds on the approximation error of the confidence level and the false-Alarm probability are obtained. © 1997-2012 IEEE.
Publication Date: 2014
IET Communications (17518628)8(9)pp. 1527-1533
In this study, monomials with odd integer powers are proposed for blind multiuser detection of code-division multiple access signals with long spreading codes, in the near-far situation. The performance of the new non-linear detectors are substantiated asymptotically and confirmed via simulations. It is demonstrated that the proposed non-linear detectors significantly outperform the matched filter detector in the block fading and Ricean fading channels, at the cost of a small increase in computational complexity. The optimum integer power value for the block fading channel with a limited interferer level, the Ricean channel with a given K factor and asynchronous channel is determined. The proposed multiuser detectors are blind in the sense that they require neither training nor the spreading code of the interferers. The detectors also do not require long convergence time for decision making in contrast to conventional blind multiuser detectors. © The Institution of Engineering and Technology 2014.
