List of Articles
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Open Access Article
1 - Cell Association Combined with Interference Management in Heterogeneous Cellular Networks Using a Distributed Algorithm
Maryam Chinipardaz Seyed Majid NoorhosseiniDue to the growing demand of cellular networks, the need to increase the capacity of these networks has always been a challenge. Heterogeneous cellular networks using small base stations alongside macro base stations are low cost and effective solutions for this problem MoreDue to the growing demand of cellular networks, the need to increase the capacity of these networks has always been a challenge. Heterogeneous cellular networks using small base stations alongside macro base stations are low cost and effective solutions for this problem. However the differences between the various BSs in heterogeneous networks have created new challenges in terms of cell association and interference management compared with the traditional cellular networks. Therefore, the design of new and efficient methods for allocating cells and resources in these networks is an open research topic. This paper addresses the need for an efficient solution to simultaneously allocating cells and subbands in order to prevent interference for all users. The protocol interference model and its modeling methods in cellular networks have been studied. After modeling the system, the problem is formulated as an integer optimization problem. Then, by reformulating the problem and using a one-level dual decomposition, an algorithm with efficient complexity with near-optimal answers is attained. Thereafter, a distributed protocol is presented in which each user and each base station would only require local information for making decisions. The simulation results confirm the effectiveness of the proposed solution. Manuscript profile -
Open Access Article
2 - Performance Analysis of Subband Adaptive Algorithms over Distributed Networks Based on Incremental Strategy
M. S. E. Abadi A. R. Danaee M. S. ShafieeThis paper presents the problem of distributed estimation in an incremental network based on the family of normalized subband adaptive algorithms (NSAAs). The distributed NSAA (dNSAA), the distributed selective partial update NSAA (dSPU-NSAA), the distributed dynamic se MoreThis paper presents the problem of distributed estimation in an incremental network based on the family of normalized subband adaptive algorithms (NSAAs). The distributed NSAA (dNSAA), the distributed selective partial update NSAA (dSPU-NSAA), the distributed dynamic selection NSAA (dDS-NSAA), and the dSPU-DS-NSAA are introduced in a unified way. The dNSAAs have better convergence speed than distributed normalized least mean square (dNLMS) algorithm especially for colored Gaussian input of the nodes. In comparison with dNSAA, the dSPU-NSAA, and dDS-NSAA have lower computational complexity and close performance to dNSAA. Also by combination of these algorithms, the dSPU-DS-NSAA is established which is computationally efficient. In addition, a unified approach for mean-square performance analysis of each individual node is presented. This approach can be used to establish a performance analysis of classical distributed adaptive algorithms as well. The theoretical expressions for transient, and steady-state performance analysis of the various dNSAAs are introduced. The validity of the theoretical results, and the good performance of these algorithms are demonstrated by several computer simulations. Manuscript profile -
Open Access Article
3 - Statistical Analysis and Modeling of CMRR and PSRR Random Variations in a Nano-CMOS Transconductance Amplifier
B. Mahboubi D. DidebanWith advancement of integrated circuit technology and aggressive scaling into nanometer regime, statistical variability in device electrical characteristics caused by discreteness of charge and fabrication process variations has significantly increased. These variations MoreWith advancement of integrated circuit technology and aggressive scaling into nanometer regime, statistical variability in device electrical characteristics caused by discreteness of charge and fabrication process variations has significantly increased. These variations in turn result in fluctuations in output characteristics of important analog building blocks and in particular, amplifiers. In this paper, with the aid of Monte-Carlo simulations for a transconductance amplifier and using 1000 different compact models of MOSFET transistors in 35nm technology node, statistical variations of important circuit parameters are investigated and analyzed based on their statistical distributions. Moreover, statistical correlations between circuit parameters are extracted. Analysis of statistical variations for circuit parameters and their correlations has a direct impact on reduction of cost and time of a design and thus, is of great amount of significance. Manuscript profile -
Open Access Article
4 - Implementation of Pulse Width Modulation Technique for Achieving Increased Voltage Gain and Balanced Voltage Stress in the A-Source Inverter
F. Zohrabi E. Abiri A. RajaeiThe Z-source converter was first introduced as a buck-boost dc-ac single-stage inverter in 2003. Different structures of impedance source inverters have been introduced for improving the performance of power inverters. Due to their specific structure, these inverters us MoreThe Z-source converter was first introduced as a buck-boost dc-ac single-stage inverter in 2003. Different structures of impedance source inverters have been introduced for improving the performance of power inverters. Due to their specific structure, these inverters use shoot-through state in order to increase the output voltage. Therefore, in addition to improving the reliability of systems, they create a single-stage dc-ac inverter capable of reducing and increasing voltage at the same time. Recently, a three-winding network called the A-source network has been introduced. A new Pulse Width Modulation method has been proposed to improve the voltage gain and reduce switching losses. In this new method, duty cycle of the switch is controlled using the third harmonic injection and the new reference voltages in the three-phase A-source inverter. The proposed modulation method reduces the switching losses and increases voltage gain without adding any additional hardware to the inverter structure. In this method, the buck-boost single-stage structure of the inverter is maintained. In this paper, the proposed method is partially analyzed and compared to the conventional Pulse Width Modulation methods. In this method, the third harmonic injection is used to increase the modulation index to 1.15 and thereby reduce the switching losses. The simulation of the proposed and conventional methods and analyzes, demonstrated the ability of the proposed system. Manuscript profile -
Open Access Article
5 - Overcurrent Relay Coordination Using Improved Hyper-Spherical Search Algorithm Considering Different Relay Characteristics and Pickup Current
A. Hassani Ahangar H. Nafisi H. Karami G. GharehpetianMinimization of the discrimination time between the backup and main overcurrent relay is one of the most critical issue in relay coordination of power system. Determination of time setting multipliers (TSMs) using evolutionary algorithms has been studied in previous pap MoreMinimization of the discrimination time between the backup and main overcurrent relay is one of the most critical issue in relay coordination of power system. Determination of time setting multipliers (TSMs) using evolutionary algorithms has been studied in previous papers. In this paper, TSM, various characteristics of the overcurrent relays and pickup currents are simultaneously considered to improve coordination of main and backup overcurrent relays. Furthermore, the coordination problem can also be considered as an optimization problem which can be solved using artificial intelligent methods. Recently, a novel optimization algorithm, called hyper-sphere search (HSS) algorithm, has been introduced. In this paper, Improved HSS (IHSS) is introduced. Based on the problems mentioned in this paper, the IHSS algorithm is more appropriate for obtaining the characteristics of the overcurrent relays, pickup currents and their TSMs. The result of IHSS is compared with HSS algorithm which has been used in previous studies. The simulation results on the test network show the efficiency of using IHSS and considering pickup currents in term of better relays coordination. Manuscript profile -
Open Access Article
6 - Optimal Operation of AC Microgrid in the Presence of Plug-in Electric Vehicles under Demand Side Managemen
A. Mehdizadeh N. Taghizadegan J. SalehiIn the recent years, integrations of renewable energy sources as well as plug-in electric vehicles are increased in the AC microgrid. Also, demand side management can be used to manage peak load in order to improve optimal performance of AC microgrid. Therefore, this pa MoreIn the recent years, integrations of renewable energy sources as well as plug-in electric vehicles are increased in the AC microgrid. Also, demand side management can be used to manage peak load in order to improve optimal performance of AC microgrid. Therefore, this paper proposes optimal operation of AC microgrid in the presence of plug-in electric vehicles under demand side management. The proposed model describes optimal operation of microgrid including the exchange power with the upstream grid, the production of DG units including wind turbines, battery storage, diesel generators, charging and discharging of electric vehicles and the manner of participation of large industrial consumers and aggregators of small consumers in demand side management that minimize the operation cost of microgrid. The proposed formulation is considered the mathematical model of various energy sources in a microgrid and the AC load flow constraints and the bus voltage and feeder current limitations has been considered.In the proposed model, charge and discharge management of plug-in electric vehicles and demand side management are simultaneously proposed to reduce operation cost of AC microgrid subject to technical and economic constraints. A 33-bus microgrid is used as test system in order to investigate effects of plug-in electric vehicles and demand side management on optimal operation of AC microgrid. The proposed model is formulated via mixed-integer non-linear programming which is solved using CPLEX solver under GAMS optimization software. Manuscript profile -
Open Access Article
7 - Close Loop Identification for Combustion System by Recurrent Adaptive Neuro-Fuzzy Inference System and Network with Exogenous Inputs
E. Aghadavoodi G. ShahgholianBoiler-turbine is a multi-variable and complicated system in steam power plants including combustion, temperature and drum water level. Selecting control loops as a unique loop in order to identify and control the boiler as a whole unit is a difficult and complicated ta MoreBoiler-turbine is a multi-variable and complicated system in steam power plants including combustion, temperature and drum water level. Selecting control loops as a unique loop in order to identify and control the boiler as a whole unit is a difficult and complicated task, because of nonlinear time variant dynamic characteristics of the boiler. It is necessary to identify each control group in order to accomplish a realistic and effective model, appropriate for designing an efficient controller. Both the effective and efficient performance of the identified model during the load change is of major importance. Here, not all parts of the system should be considered as a unit part, if determining and effective and realistic model is sought. The combustion loop of the 320 MW steam power plant of Islam Abad, Isfahan is the subject. Due to the sensitivity and complexity of the system, with respect to its nonlinear and closed loop characteristics, the identification of the system is conducted through intelligent procedures like recurrent adaptive neuro-fuzzy inference system (RANFIS) and nonlinear autoregressive model with exogenous input (NARX). The comparisons of the findings with actual data collected from the plant are presented and the accuracy of the procedures is determined. Manuscript profile -
Open Access Article
8 - Design of Parity Preserving Reversible Signed Multiplier Circuit
M. Haghparast A. BolhassaniOne of the major challenges and constraints in designing very large integrated circuits is the power dissipation of transistors. Reversible logic is one of the new paradigm in reducing the power consumption of digital circuits in the quantum computing field. In this pap MoreOne of the major challenges and constraints in designing very large integrated circuits is the power dissipation of transistors. Reversible logic is one of the new paradigm in reducing the power consumption of digital circuits in the quantum computing field. In this paper, an improved design of a parallel 5-bit parity preserving reversible signed multiplier circuit is presented. Reversible circuit designs with parity preserving property are an important issue for the implementation of fault tolerant systems in nanotechnology area. To design of the proposed multiplier, the reversible full adder circuit using 5×5 reversible HBF block with low quantum cost, and the 4×4 reversible HBL gate, with parity preserving property are proposed. The structure of the multiplier circuit consists of two parts of the partial product generation (PPG) and multi-operand addition (MOA). This structure is based on Baugh-Wooley and Wallace-Tree algorithms, which results in improved speed of operation in a 5-bit multiplier for signed digits. The proposed circuits are optimized based on important evaluation issues such as quantum cost, garbage outputs and constant inputs, and also are compared with the existing circuits. The main goal is to reduce the quantum cost, the number of constant inputs and garbage outputs in the design of the proposed multiplier circuit. The results of the final evaluation and comparison shows that the proposed multiplier in this study is improved by 26% in quantum cost, 9% in garbage outputs and 9% in constant inputs relative to the best existing designs. Manuscript profile -
Open Access Article
9 - Design, Simulation and Implementation of a Compact, 6-Way Wilkinson Power Divider Using Composite Lines
M. Heydari S. RoshaniIn this paper a novel compact 6-way Wilkinson power divider coupler (WPD) using composite lines is proposed, simulated and fabricated. The proposed structure consists of a 2-way divider and two 3-way dividers. The applied dividers have equal division ratios. In the pro MoreIn this paper a novel compact 6-way Wilkinson power divider coupler (WPD) using composite lines is proposed, simulated and fabricated. The proposed structure consists of a 2-way divider and two 3-way dividers. The applied dividers have equal division ratios. In the proposed structure long quadrature wavelength lines are replaced with small composite lines, which results in size reduction and harmonics suppression. Moreover for improved output ports isolations a resistor and a capacitor are used together. The designed device correctly works on 5.1 GHz Manuscript profile