Joint power control and beamforming in MIMO relays

2016 ◽  
Vol 35 (1) ◽  
pp. 102-116 ◽  
Author(s):  
Shahriar Shirvani Moghaddam ◽  
Maryam Alibeigi
Keyword(s):  
Power Consumption ◽  
Optimization Problem ◽  
Performance Comparison ◽  
Constant Factor ◽  
Amplify And Forward ◽  
Efficiency Criterion ◽  
Joint Power ◽  
Transmit Power ◽  
Content Type ◽  
Sum Rate

Purpose – In this paper, a wireless network consisting of multiple source-destination pairs, which communicate peer-to-peer with the help of multiple Amplify-and-Forward relays is considered. The purpose of this paper is to minimize the total relay transmit power subject to a sum rate threshold. Design/methodology/approach – It is shown that finding a beamforming matrix which satisfies the investigation’s goal is a non-convex optimization problem. Therefore, a semidefinite relaxation technique is used to turn it into a semidefinite programming problem. Thus, it can be effectively solved by interior point methods. Findings – Simulation results show that the total relay transmit power decreases with the number of relays. In addition, it is shown that relays’ power consumption decreases when the quality of uplink and/or downlink channels improves. In order to compare the proposed optimization algorithm to two conventional approaches, energy efficiency criterion used for performance comparison and complexity order for evaluating computational complexity. Although the proposed algorithm does not change the order of complexity, it needs a few more iterations to find the best result which leads to a double the processing time compared to existing approaches. Originality/value – In the present optimization problem, coefficient ß is used instead of a constant factor 2 in the original optimization problem. It is shown that by changing parameter ß between 1 and 2, a lower power consumption for a target sum rate can be achieved.

scholarly journals Joint Power Allocation and Beamforming in Amplify-and-Forward Relay Networks under Per-Node Power Constraint

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Farzin Azami ◽  
Seyed Mostafa Safavi Hemami ◽  
Abbas Akbarpour-Kasgari
Keyword(s):  
Power Consumption ◽  
Relay Networks ◽  
Critical Issue ◽  
Total Power ◽  
Amplify And Forward ◽  
Joint Power ◽  
Total Power Consumption ◽  
Quadratically Constrained ◽  
Required Quality

Two-way relay networks (TWRN) have been intensively investigated over the past decade due to their ability to enhance the performance assessment of networks in terms of cellular coverage and spectral efficiency. Yet, power control in such systems is a nontrivial issue, particularly in multirelay networks where relays are deployed to ensure a required Quality of Service (QoS). In this paper, we envision to address this critical issue by minimizing the sum-power with respect to per-node power consumption and acceptable users’ rates. To tackle this, we employ a variable transformation to turn the fractional quadratically constrained quadratic problem (QCQP) into semidefinite programming (SDP). This algorithm is also extended to a distributed format. Simulation results of deploying 10 relay stations reveal that the total power consumption will decrease to approximately 8 dBW for 6 bps/Hz sum-rate.

A practical approach to improve product of energy efficiency and capacity rate in MU-MIMO systems

2020 ◽  
Vol 16 (2) ◽  
pp. 183-202
Author(s):  
Ashu Taneja ◽  
Nitin Saluja
Keyword(s):  
Energy Efficiency ◽  
Power Consumption ◽  
Communication Systems ◽  
Mimo Systems ◽  
Mimo System ◽  
Practical Approach ◽  
System Capacity ◽  
Content Type ◽  
Channel Interference ◽  
Sum Rate

Purpose The major challenges in the modern-day wireless communication systems are increased co-channel interference owing to large number of users and the increased energy consumption owing to high circuit and/or hardware power consumption. Hence, the purpose of this paper is to present a practical approach involving linear precoding, channel estimation, user selection (US) and transmit antenna selection (AS) for enhanced reliability in multiuser multiple-input multiple output (MU-MIMO) system. Design/methodology/approach The proposed technique considers systematic and optimum deployment of users and transmits antennas for each selected user which enhances the sum rate or the system capacity. The comparison of algorithms, namely, norm-based and capacity-based US is presented with its implementation with precoding techniques, namely, block-diagonalization (BD) and zero-forcing with combining (ZFC) which is used to minimize co-channel interference. In this paper, a power consumption model is proposed for energy efficiency calculation in MU-MIMO system. Also, post analysis, the variant of US and AS algorithms optimizing the performance of BD and ZFC precoding technique is proposed. Findings It is seen that the proposed MU-MIMO system with norm-based US and norm-based AS improves over existing US-based systems by 43% in terms of sum rate and 19% in terms of energy efficiency for 100 users. Originality/value It is seen that the proposed MU-MIMO system with norm-based US and norm-based AS improves over existing US-based systems by 43% in terms of sum rate and 19% in terms of energy efficiency for 100 users.

Power Efficient Implementation of Low Noise CMOS LC VCO using 32nm Technology for RF Applications

2018 ◽  
Vol 6 (8) ◽  
pp. 53
Author(s):  
Shitesh Tiwari ◽  
Sumant Katiyal ◽  
Parag Parandkar
Keyword(s):  
Power Consumption ◽  
Phase Noise ◽  
Tuning Range ◽  
Low Voltage ◽  
Performance Comparison ◽  
Low Noise ◽  
Center Frequency ◽  
Voltage Controlled Oscillator ◽  
Low Phase Noise ◽  
Lc Vco

Voltage Controlled Oscillator (VCO) is an integral component of most of the receivers such as GSM, GPS etc. As name indicates, oscillation is controlled by varying the voltage at the capacitor of LC tank. By varying the voltage, VCO can generate variable frequency of oscillation. Different VCO Parameters are contrasted on the basis of phase noise, tuning range, power consumption and FOM. Out of these phase noise is dependent on quality factor, power consumption, oscillation frequency and current. So, design of LC VCO at low power, low phase noise can be obtained with low bias current at low voltage.  Nanosize transistors are also contributes towards low phase noise. This paper demonstrates the design of low phase noise LC VCO with 4.89 GHz tuning range from 7.33-11.22 GHz with center frequency at 7 GHz. The design uses 32nm technology with tuning voltage of 0-1.2 V. A very effective Phase noise of -114 dBc / Hz is obtained with FOM of -181 dBc/Hz. The proposed work has been compared with five peer LC VCO designs working at higher feature sizes and outcome of this performance comparison dictates that the proposed work working at better 32 nm technology outperformed amongst others in terms of achieving low Tuning voltage and moderate FoM, overshadowed by a little expense of power dissipation. 

Sum-Rate Optimization Constrained by Consumed Power for Multi- Antenna Non-Regenerative Relay Network

2020 ◽  
Vol 10 (2) ◽  
pp. 143-152 ◽  
Author(s):  
Maryam Alibeigi ◽  
Shahriar S. Moghaddam
Keyword(s):  
Relay Network ◽  
Minimization Algorithm ◽  
Amplify And Forward ◽  
Relay Nodes ◽  
Convex Problem ◽  
Semidefinite Programming Problem ◽  
Total Leakage ◽  
Sum Rate ◽  
Rate Optimization ◽  
Novel Algorithm

Background & Objective: This paper considers a multi-pair wireless network, which communicates peer-to-peer using some multi-antenna amplify-and-forward relays. Maximizing the throughput supposing that the total relay nodes’ power consumption is constrained, is the main objective of this investigation. We prove that finding the beamforming matrix is not a convex problem. Methods: Therefore, by using a semidefinite relaxation technique we find a semidefinite programming problem. Moreover, we propose a novel algorithm for maximizing the total signal to the total leakage ratio. Numerical analyses show the effectiveness of the proposed algorithm which offers higher throughput compared to the existing total leakage minimization algorithm, with much less complexity. Results and Conclusion: Furthermore, the effect of different parameters such as, the number of relays, the number of antennas in each relay, the number of transmitter/receiver pairs and uplink and downlink channel gains are investigated.

Dynamic output feedback control for nonlinear large-scale interconnected systems

2020 ◽  
Vol 39 (4) ◽  
pp. 801-821
Author(s):  
Ezzeddine Touti ◽  
Ali Sghaier Tlili ◽  
Muhannad Almutiry
Keyword(s):  
Decentralized Control ◽  
Output Feedback ◽  
Large Scale ◽  
Optimization Problem ◽  
Lyapunov Theory ◽  
Interconnected Systems ◽  
Dynamic Output Feedback ◽  
Content Type ◽  
Dynamic Output ◽  
Control Scheme

Purpose This paper aims to focus on the design of a decentralized observation and control method for a class of large-scale systems characterized by nonlinear interconnected functions that are assumed to be uncertain but quadratically bounded. Design/methodology/approach Sufficient conditions, under which the designed control scheme can achieve the asymptotic stabilization of the augmented system, are developed within the Lyapunov theory in the framework of linear matrix inequalities (LMIs). Findings The derived LMIs are formulated under the form of an optimization problem whose resolution allows the concurrent computation of the decentralized control and observation gains and the maximization of the nonlinearity coverage tolerated by the system without becoming unstable. The reliable performances of the designed control scheme, compared to a distinguished decentralized guaranteed cost control strategy issued from the literature, are demonstrated by numerical simulations on an extensive application of a three-generator infinite bus power system. Originality/value The developed optimization problem subject to LMI constraints is efficiently solved by a one-step procedure to analyze the asymptotic stability and to synthesize all the control and observation parameters. Therefore, such a procedure enables to cope with the conservatism and suboptimal solutions procreated by optimization problems based on iterative algorithms with multi-step procedures usually used in the problem of dynamic output feedback decentralized control of nonlinear interconnected systems.

Workspace, dexterity and dimensional optimization of microhexapod

2015 ◽  
Vol 35 (4) ◽  
pp. 341-347 ◽  
Author(s):  
E. Rouhani ◽  
M. J. Nategh
Keyword(s):  
Degrees Of Freedom ◽  
Optimization Problem ◽  
Screw Theory ◽  
Design Parameters ◽  
Dimensional Synthesis ◽  
Content Type ◽  
Workspace Analysis ◽  
The Difference ◽  
Flexure Joints ◽  
6 Degrees Of Freedom

Purpose – The purpose of this paper is to study the workspace and dexterity of a microhexapod which is a 6-degrees of freedom (DOF) parallel compliant manipulator, and also to investigate its dimensional synthesis to maximize the workspace and the global dexterity index at the same time. Microassembly is so essential in the current industry for manufacturing complicated structures. Most of the micromanipulators suffer from their restricted workspace because of using flexure joints compared to the conventional ones. In addition, the controllability of micromanipulators inside the whole workspace is very vital. Thus, it is very important to select the design parameters in a way that not only maximize the workspace but also its global dexterity index. Design/methodology/approach – Microassembly is so essential in the current industry for manufacturing complicated structures. Most of the micromanipulators suffer from their restricted workspace because of using flexure joints compared to the conventional ones. In addition, the controllability of micromanipulators inside the whole workspace is very vital. Thus, it is very important to select the design parameters in a way that not only maximize the workspace but also its global dexterity index. Findings – It has been shown that the proposed procedure for the workspace calculation can considerably speed the required calculations. The optimization results show that a converged-diverged configuration of pods and an increase in the difference between the moving and the stationary platforms’ radii cause the global dexterity index to increase and the workspace to decrease. Originality/value – The proposed algorithm for the workspace analysis is very important, especially when it is an objective function of an optimization problem based on the search method. In addition, using screw theory can simply construct the homogeneous Jacobian matrix. The proposed methodology can be used for any other micromanipulator.

An improved sparrow search algorithm based on levy flight and opposition-based learning

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Danni Chen ◽  
JianDong Zhao ◽  
Peng Huang ◽  
Xiongna Deng ◽  
Tingting Lu
Keyword(s):  
Parameter Optimization ◽  
Optimization Problem ◽  
Heuristic Algorithms ◽  
Search Algorithm ◽  
Convergence Speed ◽  
Support Vector ◽  
Lévy Flight ◽  
Levy Flight ◽  
Content Type ◽  
Opposition Based Learning

Purpose Sparrow search algorithm (SSA) is a novel global optimization method, but it is easy to fall into local optimization, which leads to its poor search accuracy and stability. The purpose of this study is to propose an improved SSA algorithm, called levy flight and opposition-based learning (LOSSA), based on LOSSA strategy. The LOSSA shows better search accuracy, faster convergence speed and stronger stability. Design/methodology/approach To further enhance the optimization performance of the algorithm, The Levy flight operation is introduced into the producers search process of the original SSA to enhance the ability of the algorithm to jump out of the local optimum. The opposition-based learning strategy generates better solutions for SSA, which is beneficial to accelerate the convergence speed of the algorithm. On the one hand, the performance of the LOSSA is evaluated by a set of numerical experiments based on classical benchmark functions. On the other hand, the hyper-parameter optimization problem of the Support Vector Machine (SVM) is also used to test the ability of LOSSA to solve practical problems. Findings First of all, the effectiveness of the two improved methods is verified by Wilcoxon signed rank test. Second, the statistical results of the numerical experiment show the significant improvement of the LOSSA compared with the original algorithm and other natural heuristic algorithms. Finally, the feasibility and effectiveness of the LOSSA in solving the hyper-parameter optimization problem of machine learning algorithms are demonstrated. Originality/value An improved SSA based on LOSSA is proposed in this paper. The experimental results show that the overall performance of the LOSSA is satisfactory. Compared with the SSA and other natural heuristic algorithms, the LOSSA shows better search accuracy, faster convergence speed and stronger stability. Moreover, the LOSSA also showed great optimization performance in the hyper-parameter optimization of the SVM model.

Evaluating disaster-related tweet credibility using content-based and user-based features

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nasser Assery ◽  
Yuan (Dorothy) Xiaohong ◽  
Qu Xiuli ◽  
Roy Kaushik ◽  
Sultan Almalki
Keyword(s):  
Machine Learning ◽  
Unsupervised Learning ◽  
Supervised Learning ◽  
Emergency Response ◽  
Learning Model ◽  
Performance Comparison ◽  
Supervised Machine Learning ◽  
Learning Methods ◽  
Content Type ◽  
Machine Learning Classification

Purpose This study aims to propose an unsupervised learning model to evaluate the credibility of disaster-related Twitter data and present a performance comparison with commonly used supervised machine learning models. Design/methodology/approach First historical tweets on two recent hurricane events are collected via Twitter API. Then a credibility scoring system is implemented in which the tweet features are analyzed to give a credibility score and credibility label to the tweet. After that, supervised machine learning classification is implemented using various classification algorithms and their performances are compared. Findings The proposed unsupervised learning model could enhance the emergency response by providing a fast way to determine the credibility of disaster-related tweets. Additionally, the comparison of the supervised classification models reveals that the Random Forest classifier performs significantly better than the SVM and Logistic Regression classifiers in classifying the credibility of disaster-related tweets. Originality/value In this paper, an unsupervised 10-point scoring model is proposed to evaluate the tweets’ credibility based on the user-based and content-based features. This technique could be used to evaluate the credibility of disaster-related tweets on future hurricanes and would have the potential to enhance emergency response during critical events. The comparative study of different supervised learning methods has revealed effective supervised learning methods for evaluating the credibility of Tweeter data.

Design optimization of helicopter rotor using kriging

2018 ◽  
Vol 90 (6) ◽  
pp. 937-945 ◽  
Author(s):  
Saijal Kizhakke Kodakkattu ◽  
Prabhakaran Nair ◽  
Joy M.L.
Keyword(s):  
Rotor Blade ◽  
Optimization Problem ◽  
Torsional Stiffness ◽  
Helicopter Rotor ◽  
Vibration Level ◽  
Content Type ◽  
Aeroelastic Analysis ◽  
Kriging Metamodel ◽  
Helicopter Rotor Blade ◽  
Trailing Edge Flaps

Purpose The purpose of this study is to obtain optimum locations, peak deflection and chord of the twin trailing-edge flaps and optimum torsional stiffness of the helicopter rotor blade to minimize the vibration in the rotor hub with minimum requirement of flap control power. Design/methodology/approach Kriging metamodel with three-level five variable orthogonal array-based data points is used to decouple the optimization problem and actual aeroelastic analysis. Findings Some very good design solutions are obtained using this model. The best design point in minimizing vibration gives about 81 per cent reduction in the hub vibration with a penalization of increased flap power requirement, at normal cruise speed of rotor-craft flight. Practical implications One of the major challenges in the helicopters is the high vibration level in comparison with fixed wing aircraft. The reduction in vibration level in the helicopter improves passenger and crew comfort and reduces maintenance cost. Originality/value This paper presents design optimization of the helicopter rotor blade combining five design variables, such as the locations of twin trailing-edge flaps, peak deflection and flap chord and torsional stiffness of the rotor. Also, this study uses kriging metamodel to decouple the complex aeroelastic analysis and optimization problem.

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