Sharif Digital Repository

Most of the energy efficient routing algorithms proposed for sensor networks are reactive routing algorithms. By definition, reactive algorithms are those in which routes are constructed whenever there is data transmission. In such algorithms, to transmit data packets from a certain transmitter to the corresponding receiver, efficient route will be constructed using RREQ delivery. This delivery is performed via flooding and modified flooding algorithms. One of the most important criteria of such flooding algorithm is not to miss the best final route during RREQ delivery. Most of major algorithms ignored this fact and instead tried to minimize energy consumption during flooding algorithm. But... 

In this paper, we introduce a new cost function for SIR-Based uplink power control algorithms that takes into account transmission power level as well as target Signal-to-Interference Ratio (SIR) deviation. Existence of Nash equilibrium point, its uniqueness and the algorithm convergence are proved in the framework of so-called standard power control schemes. As shown through simulations, the proposed method results in significant transmit power reduction while achieving almost the same average SIR level. In addition, it is shown that the new scheme results in improved overall network fairness in comparison with another algorithm  

Crosstalk is the major limiting factor in DSL systems in terms of bit-rate or service coverage. Multiuser power control algorithms can be used to combat crosstalk degrading effects. The best ever known distributed power control solution is Iterative Water-filling (IWF). In this paper the performance of IWF in an ADSL system is considered in terms of offered rate-region and convergence speed. Then two novel modifications are proposed to accelerate convergence (usually 100-400%) without any performance loss. Therefore it suits better in practical applications, since each iteration needs re-initialization of the modem. © 2004IEEE  

This article describes an automatic reactor power control system for VVER-1000 reactor and reports simulation analysis results for a typical daily load follow operation. The associated reactor control algorithm is called `mode G' that uses a heavy-worth bank (H-bank) dedicated to axial power shape control and the light-gray banks (G-banks) for reactor power change and reactivity compensation. The simulation results for daily load follow operation in three burnup states of first cycle illustrate that the load follow capability of VVER-1000 reactors using this algorithm will be improved  

Massive multiple-input multiple-output (M-MIMO) is recognized as a promising technology for the next generation of wireless networks because of its potential to increase the spectral efficiency. In initial studies of M-MIMO, the system has been considered to be perfectly synchronized throughout the entire cells. However, perfect synchronization may be hard to attain in practice. Therefore, we study a M-MIMO system whose cells are not synchronous to each other, while transmissions in a cell are still synchronous. We analyze an asynchronous downlink M-MIMO system in terms of the coverage probability and the ergodic rate by means of the stochastic geometry tool. For comparison, we also obtain... 

we study the uplink performance of wireless infrared code-division multiple access (CDMA) networks using OOK with optical orthogonal codes (OOC's). The analysis is performed in two cases assuming a cellular network architecture, in which all users are uniformly distributed in the cell's area. The first case is when all users transmit with the same power and no power control mechanism is used. Then, the system that deploys power control mechanism is analyzed and the performance improvements are demonstrated. The impact of imperfect power control which is caused by errors in channel estimation is also analyzed and the analytical and numerical results for all cases are included. The results... 

This article presents a comprehensive small signal model for a virtual synchronous generator (VSG) integrated into a microgrid. In the developed state-space, active and reactive power control loops of the VSG as well as resistances, and reactances of the lines are considered. Based on this model, the robust D-stable region in terms of different values of inertia constant $(M)$, and damping coefficient $(D)$ values of the VSG is obtained. To enhance both transient performance as well as guarantee the robust D-stable operation of VSG, an optimization problem is also proposed. Moreover, a new control method is suggested to damp frequency oscillations of the microgrid. The proposed controller is... 

In this paper the direct power control methods of doubly fed induction generator in wind turbine applications are studied. In the methods under study, the proper voltage space vector of the rotor side converter is selected using a switching table which is derived from flux position and the difference between the measured and reference stator active and reactive powers. Various simulations are performed in Matlab/Simulink software on a DFIG system in order to investigate the dynamic performance and robustness of the proposed control methods against machine internal parameters variations  

Wireless infrared optical code-division multiple access (W-OCDMA) is a new developing technique with many useful applications. Noting the limitation on power consumption and eye-safety requirements, wireless optical systems are power limited. Therefore control and efficient use of optical power is a key issue in analysis and design of these systems. Also, multi-user interference is the major source of impairment in these systems and power control is required to control and reduce this interference. Power control and the inevitable errors in its algorithms play an important role in design and implementation of these systems. In this article the authors study the uplink performance of W-OCDMA... 

Wireless infrared optical code-division multiple access (W-OCDMA) is a new developing technique with many useful applications. Noting the limitation on power consumption and eye-safety requirements, wireless optical systems are power limited. Therefore control and efficient use of optical power is a key issue in analysis and design of these systems. Also, multi-user interference is the major source of impairment in these systems and power control is required to control and reduce this interference. Power control and the inevitable errors in its algorithms play an important role in design and implementation of these systems. In this article the authors study the uplink performance of W-OCDMA... 

In this paper, by extending Space Vector Modulation (SVM) technique to three-phase four-wire systems, a new strategy is developed for the control of Active Power Filters (APFs). It is shown that the conventional SVM method cannot compensate for the current in the neutral wire in a three-phase four wire system. Simulations have been performed using PSCAD/EMTDC software. Simulation results are provided to prove the ability of the proposed technique in compensating the zero-sequence current. ©2006 IEEE  

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.... 

Power control mechanisms play a critical role in underlay cognitive radio networks where primary users' quality of service should not be degraded by the secondary users transmission. Consequently, the inflicted interference power of the secondary transmitters on the primary receivers should be less than certain threshold levels that is required to be considered in designing power control algorithms for such networks. In this paper, we first propose a power reduction algorithm for the set of secondary transmitting links in order to guarantee that the members of this set do not violate the interference constraints set by primary users while maintaining their specific SINR quality of service... 

Proliferation of grid-connected photovoltaic systems (PVSs) causes technical problems due to their variable and non-dispatchable generated power. High penetration of PVS in distribution networks can result in overvoltage in some operating conditions. Although this situation occurs rarely, it limits the installed capacity of PVS. In this paper, adaptive droop-based control algorithms are presented to regulate active and reactive power of PVS, with the objectives of loss minimization and increasing the PVS capacity installation without unallowable overvoltage. Operating voltage range of the PVS is divided into several intervals, and a specific control algorithm is presented for each of them.... 

In this paper, joint dynamic frequency selection and transmit power control problem with the goal of power minimization for a target SINR is investigated for cognitive radio networks. The optimization problem is formulated and three algorithms are proposed: A centralized algorithm based on graph coloring, and two distributed algorithms based on game theory; one for coordinated and the other for non-coordinated scenarios. Performance of the proposed algorithms in terms of power minimization and convergence speed is evaluated through simulations. Comparing the performance with the optimum solution, all three algorithms show near-optimum power minimization performance for the simulated... 

Owing to the local nature of voltage and reactive power control, the voltage control is managed in a zonal or regional basis. A new comprehensive scheme for optimal selection of pilot points is proposed in this study. The uncertainties of operational and topological disturbances of the power system are included to provide the robustness of the pilot node set. To reduce the huge number of probable states (i.e. combined states of load and topological changes), a scenario reduction technique is used. The resulted optimal control problem is solved using a new immune-based genetic algorithm. The performance of the proposed method is verified over IEEE 118-bus and realistic Iranian 1274-bus... 

The impact of an interline power-flow controller (IPFC) on composite system delivery point and overall system reliability indices is examined in this paper. In this application, the IPFC with dc transmission lines is employed in a system for coordinated control of line impedances of two, distance away, transmission lines with the objective of managing power flows on the two lines. It is also used to balance the real power being transferred between the compensated lines. For this purpose, the reliability model associated with a converter station has been developed and incorporated in an IPFC reliability model. A number of reliability indices are calculated at both the loadpoint and system...