S.M.H. Andargoli

Babol Noshirvani University of Technology, Barfrush, Māzandarān, Iran

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Publications (14)4.22 Total impact

  • S.M. Hosseini Andargoli, K. Mohamed-pour
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    ABSTRACT: This study addresses subcarrier allocation and power distribution in a sectorised two-cell downlink orthogonal frequency-division multiple access system impaired by multicell interference. The objective is to maximise the sum spectral efficiency in a way that the signal-to-interference plus noise ratio (SINR) of the transmitted data substream on each subcarrier meets a target SINR. In cellular systems because of intercell interference, it may not be possible to guarantee the target SINR in all cells simultaneously; therefore the authors have suggested a cooperative resource allocation algorithm which tries to provide the target SINR per subcarrier in all cells through cooperation in the interference control. For a considered subcarrier, if achieving the target SINR is impossible by the interference reduction, one base station avoids transmission on the considered subcarrier so that another base station can meet the target SINR. For complexity reduction, a simplified resource allocation algorithm is then provided based on the separation of subcarrier allocation and power control. Simulation results show that the proposed algorithms not only guarantee the target SINR but achieve more sum spectral efficiency than benchmark algorithms in many practical situations.
    IET Communications 01/2014; 8(9):1488-1498. · 0.64 Impact Factor
  • M. Najimi, A. Ebrahimzadeh, S.M.H. Andargoli, A. Fallahi
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    ABSTRACT: This paper proposes two methods for maximizing the lifetime of the cognitive sensor networks by focusing on node selection criteria for spectrum sensing in such networks. We maximize the network lifetime with constraints on the detection performance by determining the sensors, which sense the spectrum. This is a NP-complete problem and cannot be solved by standard methods. Therefore, we relax it to a more tractable form. Based on convex optimization framework, the optimal conditions are obtained and the sensors, which sense the spectrum, are determined. Simulation results show that our proposed algorithm is very efficient in terms of network lifetime maximization.
    IEEE Sensors Journal 01/2014; 14(7):2376-2383. · 1.48 Impact Factor
  • M. Najimi, A. Ebrahimzadeh, S.M.H. Andargoli, A. Fallahi
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    ABSTRACT: In this paper, we address the problem of sensor selection for energy efficient spectrum sensing in cognitive sensor networks. We consider minimizing energy consumption and improving spectrum sensing performance simultaneously. For this purpose, we employ the energy detector for spectrum sensing and formulate the problem of sensor selection in order to achieve energy efficiency in spectrum sensing while reducing complexity. Due to the NP-complete nature of the problem, we simplify the problem to a more tractable form through mapping assignment indices from integer to the real domain. Based on the standard optimization techniques, the optimal conditions are obtained and a closed-form equation is expressed to determine the priority of nodes for spectrum sensing. In the next step, to save more energy, the decision node (DN) selection procedure is proposed to address the problem of direct transmissions to fusion center. Then, the problem of joint sensing node selection and DN selection is analyzed and an efficient solution is extracted based on the convex optimization framework. The novelty of the proposed work is to address the selection of the best sensing nodes while minimizing energy consumption. Simulation results show that significant energy is saved due to the proposed schemes in different scenarios.
    IEEE Sensors Journal 01/2013; 13(5):1610-1621. · 1.48 Impact Factor
  • S.H. Hojjati, A. Ebrahimzadeh, S.M. Hosseini Andargoli, M. Najimi
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    ABSTRACT: In this paper we address sensor selection problem for spectrum sensing in cognitive radio network. The limited sensor's energy is an important issue which has attracted more attention in recent years. We propose an energy efficient cooperative spectrum sensing when Multi-Input Multi-Output (MIMO) sensors are used. Two decision techniques for combination of antennas signals were used in each sensor: hard decision and soft decision. The OR rule is used for hard decision and Selection Combining (SC) and Equal Gain Combining (EGC). In each combination scheme, the problem was the sensor selection so that the energy consumption was minimized while detection performance was satisfied. The problem was solved based on the standard convex optimization method. Simulation results show that significant energy saving is achieved in comparison with the networks using Single-Input Single-Output (SISO) sensors specifically in low Signal to Noise Ratio (SNR) regime. Among of all methods, EGC combining has the least energy consumption while satisfy desired detection performance.
    Computer and Knowledge Engineering (ICCKE), 2013 3th International eConference on; 01/2013
  • A. Kasaeyan, K. Mohamed-pour, S.M.H. Andargoli
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    ABSTRACT: In this paper, we aim to formulate the coordinated beam-forming problem for a multi-cell MIMO-OFDMA system by an optimization method. The formulation has been done for downlink channel, using double layer pre-coder and post-coder matrices in both transmitter and receiver. We have proposed an iterative algorithm to find the proper beam-forming matrices in such a way that minimizes the mean square error (MMSE) in internal layer and maximizes the total system throughput in external layer. Our proposed algorithm guarantees the MMSE at each user in each subcarrier and also maximizes the sum rate of multi-cell system. The simulation results show that the proposed method leads to a greater throughput in comparison with conventional algorithms and provides substantial performance gains compared to single-cell optimization.
    Electrical Engineering (ICEE), 2013 21st Iranian Conference on; 01/2013
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    ABSTRACT: This paper aims to formulate power and sub-channel allocation problem in a multi-cell Orthogonal Frequency Division Multiple Access (OFDMA) half-duplex decode-and-forward (DF) relay assisted network in the presence of multi-cell interference. This formulation takes into account multi-cell co-channel interference as one of the critical factors in multi-cell processing. The resulting non-convex optimization problem has been solved by dual decomposition and, an iterative resource allocation algorithm is proposed to find solutions which satisfy Karush-Kuhn-Tucker (KKT) conditions. Two resource allocation strategies based on centralized and distributed policy are derived which maximize the average system throughput (bit/sec/Hz). Simulation results show that the proposed algorithm approach the maximum achievable throughput in comparison with conventional algorithms and provides substantial performance gains compared to single-cell optimization.
    International Symposium on Telecommunication Technologies (ISTT), 2012, Kuala Lumpur, Malaysia; 11/2012
  • M. Najimi, A. Ebrahimzadeh, S.M.H. Andargoli, A. Fallahi
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    ABSTRACT: In this paper, we propose an energy-efficient technique for cooperative spectrum sensing in cognitive sensor networks. In cooperative spectrum sensing, information is collected from different sensors to make a final decision. We use an "on/off" method for cognitive wireless sensor networks and also formulate the determination of the number of sensing nodes, such that energy consumption in spectrum sensing reduces and satisfies the constraint on the detection performance. The constraint on the detection performance is given by a minimum global probability of detection and a maximum global probability of false alarm. We use the energy detector as the spectrum sensing technique and solve the problem using the convex optimization methods while consider the computational complexity. Simulation results show that our proposed technique saves significant energy in different conditions.
    Telecommunications (IST), 2012 Sixth International Symposium on; 01/2012
  • S.M.H. Andargoli, K. Mohamed-pour
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    ABSTRACT: This study addresses resource allocation for weighted sum throughput maximisation (WSTM) in a sectorised two-cell downlink orthogonal frequency-division multiple access systems impaired by multicell interference. It is well known that the optimisation problem for this scenario is NP-hard and combinational, which is here converted to a novel WSTM problem based on the intercell interference limitation. In the new problem, we use a lower bound of throughout as a cost function which is convex, and so it simplifies the power allocation algorithm and offers a better convergence. Then, two subclasses of this new problem are solved based on the dual Lagrange framework. By the first subclass, on the assumption that subcarrier allocation parameters are fixed, an algorithm for optimal power allocation (OPA) is obtained. However, the optimal resource allocation requires an exhaustive search, including the OPA which cannot be implemented in practice because of its high complexity. By the second subclass, the joint subcarrier allocation and power distribution for two adjacent cells as a general problem is solved. Here, the algorithm allocates simultaneously the subcarriers and the power of the considered two cells while the resource allocation parameters of both cells are coupled mutually. After that, we propose a new centralised algorithm which combines the proposed power allocation with the non-convex subcarrier allocation without increase in the complexity. Simulation results show that the proposed algorithms achieve efficient performance in many practical situations.
    IET Communications 01/2012; 6(6):628-637. · 0.64 Impact Factor
  • S.M.H. Andargoli, K. Mohamed-pour
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    ABSTRACT: This paper addresses subcarrier allocation and power distribution in a sectorized two-cell downlink OFDMA system impaired by multicell interference. The objective is to maximize the sum throughput in a way that the SINR of the transmitted data substream on each subcarrier meets a target SINR. In cellular systems due to intercell interference, it may not be possible to guarantee the target SINR in all cells simultaneously; therefore, we have suggested a cooperative resource allocation algorithm which tries to provide the target SINR in all cells through cooperation in the interference control. Simulation results show that the proposed algorithm not only guarantee the target SINR but achieve an efficient sum throughput in many practical situations.
    Telecommunications (IST), 2012 Sixth International Symposium on; 01/2012
  • M.H. Moghaddam, K. Mohamed-pour, S.M.H. Andargoli
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    ABSTRACT: This paper aims to formulate an optimization problem for power allocation in multi-cell half-duplex decode-and-forward (DF) relay assisted networks in the presence of interference channel. This formulation takes into account multi-cell cochannel interference. The resulting non-convex optimization problem has been solved by dual decomposition and, an iterative resource allocation algorithm. A closed-form power allocation policy is derived which maximize the average system throughput (bit/sec/Hz). Simulation results are shown that the proposed algorithm approaches the maximum achievable throughput in comparison with conventional algorithms and provides substantial performance gains compared to single-cell optimization.
    Telecommunications (IST), 2012 Sixth International Symposium on; 01/2012
  • M.S. Googhari, K. Mohamed-pour, S.M.H. Andargoli
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    ABSTRACT: In this paper, the resource allocation for OFDMA-based cognitive radio (CR) system is considered. We propose a two-step resource allocation algorithm that maximizes the sum throughput of the system while satisfying the quality of service (QoS) requirements for guaranteed users (GUs). By the first step, the sum power of the guaranteed users is minimized as the guaranteed rate is provided. By the second step, the remaining resources are distributed among all users so that the sum throughput is maximized. In both steps, power allocation is performed in a way that the adverse interference on the primary users (PUs) is avoided. Simulation results show that the proposed algorithm is highly efficient in terms of rate guarantee for GUs and sum throughput maximization.
    Telecommunications (IST), 2012 Sixth International Symposium on; 01/2012
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    ABSTRACT: In this paper, we propose a new channel estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems. For fast fading environment, we introduce a new method which is extended to the Alamouti Coded OFDM case. At the first stage of this algorithm, the channel response is estimated for pilot sub-carriers and then, the channel response for data sub-carriers are interpolated by Gaussian Radial Basis function as it is an efficient nonlinear interpolator. The post-processing and filtering on the estimated channel taps energy are proposed to improve the estimation performance and reduce the noise effects of primary estimation, which is caused by LS estimation at pilot data. The accuracy of our channel estimation algorithm is improved by using iterative decision feedback. The decision feedback method is used to update channel parameters in each OFDM symbol. The effectiveness of new techniques is demonstrated through the simulation of an Alamouti coded OFDM system with two-transmit and two-receive antennas. Finally, the results are analyzed and compared with previous algorithms which show performance enhancement.
    Wireless Telecommunications Symposium (WTS), 2010; 05/2010
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    ABSTRACT: A dual-hop transmission in Rayleigh fading channels is presented where the relay uses Amplify and Forward (AF) protocol and Selection Combining (SC) technique. A closed-form expression is derived for outage probability of the overall received SNR at the destination. Also, the performance analysis is presented in terms of the Average Bit Error Rate (ABER) and expressions are derived for its upper and lower bounds. Finally, comparison between DF and AF systems are presented. We use simulation to verify the analytical results. Numerical results show that the proposed relaying system outperform the conventional relaying which use a single antenna in receiver and transmitter.
    Wireless Telecommunications Symposium (WTS), 2010; 05/2010
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    ABSTRACT: In this paper, we propose the new channel estimation algorithm for orthogonal frequency division multiplexing (OFDM) system in fast fading channels. It is two-step procedure. In the first step, we obtain an initial estimation of channel response at pilot subcarriers by least square method, then we employ the Gaussian radial basis function as a efficient nonlinear interpolator to estimate the channel response at the data symbol position. In the second step, we use the processing and filtering on the estimated channel taps based on magnitude or energy of channel coefficients. This step of algorithm is very effective in removing the LS estimation error.
    Advanced Communication Technology, 2009. ICACT 2009. 11th International Conference on; 03/2009