Wyniki wyszukiwania - BazTech

1

Efficient Iterative Detection Based on Conjugate Gradient and Successive Over-Relaxation Methods for Uplink Massive MIMO Systems

Labed Smail, Aounallah Naceur

Journal of Telecommunications and Information Technology

|

2023

|

nr 2

1--9

EN

Being a crucial aspect of ﬁfth-generation (5G) mobile communications systems, massively multiple-input multipleoutput (mMIMO) architectures are expected to help achieve the highest key performance indicators. However, the huge numbers of antennas used in such systems make it diﬃcult to determine the inversion of the signal channel matrix relied upon by several detection methods, hence posing a problem with accurate estimation of the symbols sent. In this paper, conjugate gradient (CG) and successive over-relaxation (SOR) methods are selected to construct a new iterative approach that avoids the matrix inversion computation issue. This suggested approach for uplink mMIMO detection is based on a joint cascade structure of both iterative methods. The CG method is ﬁrst applied and adjusted for the initial solution, followed by the SOR method in the ﬁnal iterations for terminal computations, resulting in an algorithm with robust performance and low computational complexity. Furthermore, the new hybrid scheme operates based on the relaxation parameter, whose value has a great impact on error performance and, whose optimal determination is necessary. Numerical simulations reveal that the proposed scheme is capable of signiﬁcantly improving signal detection accuracy with minimum complexity. The simulation results indicated that the proposed detector outperforms CG and SOR detectors, achieves close to optimal performance, requires fewer iterations, and reduces complexity.

2

Using total variation method to estimate the permeability model of a gas fingering area in an Iranian carbonate reservoir

Hosseini Mohammad

Acta Geophysica

|

2021

|

Vol. 69, no. 3

821--839

EN

A dozen of inversion methods are applied and tested to estimate the permeability of the area where gas-fngering event has taken place in an Iranian carbonate reservoir located southwest of Iran. In a previous work, the gas-fingering event was detected by inverting the 3D seismic data and in this study the permeability model in that area is estimated. Because the lateral area of the gas-fingering event is narrow, the whole system conducting the injected gas can be considered as one rock unit system and therefore the assumption of horizontal linear steady-state fow can be applied. Inversion methods are exploited to determine the permeability in the interval of interest. The interval of interest is located at the crest and involves four wells among which one is the gas-injection well. To investigate the feasibility of such an approach and select the best possible inversion method, frst a controlled experiment for the system is designed and studied. The porosity values of the system are known from seismic data inversion and the permeability values are the desired parameters. The permeability values at well locations are known via well-test data and are used as constraints in the inversion procedure. The interval of interest is discretized and a simulator is used to simulate the fuid fow in the controlled system in order to apply and validate the inversion methods. All calculations are performed in the MATLAB environment. According to the results from the controlled experiment, the Maximum Entropy and Total Variation methods were found to be the best two inversion methods which were successful in retrieving the true permeability model. Similar comparative study using diferent inversion methods is performed for the real case for which the results retrieved by the Total Variation method is most reliable as it suggests the best recovery of the permeability value for the check-well. An estimation of the fracture permeabilities for the area under study also indicated that the inverted permeability values are most representing the fracture permeabilities rather than the matrix. The results of this study will be used to tune the feld simulation model in terms of rock and fuid properties, consider the inverted permeability model as further constraints for the reservoir history-matching of the oil feld, reconsider the factors involving the gas injection plan for the oil feld, and obtain insights for further feld development plans in other nearby oil felds.

3

Computational and Statistical Aspects of Determining Ship's Position

Drapella A., Morgaś W.

Annual of Navigation

|

2017

|

No. 24

5--18

EN

In its mathematical essence, the task of determining ship’s position coordinates, is to minimize appropriately defined goal function. This paper proposes to use the method of conjugate gradient for this purpose. The reason is that calculations may be performed in some seconds time because Microsoft and Apache implemented the conjugate gradient method as a tool called the Solver and embedded this tool in their widely offered and popular spreadsheets, namely Excel and the Open Office Calc, respectively. Further in this paper it is shown how to precisely assess errors of ship’s position coordinates with the Monte Carlo method that employs the Solver.

PL

Matematyczna istota wyznaczania współrzędnych pozycji okrętu to minimalizacja odpowiednio zdefiniowanej funkcji celu. Artykuł proponuje wykorzystanie do tego metody gradientu sprzężonego. Dzięki niej obliczenia mogą być wykonane w kilka sekund, ponieważ Microsoft i Apache zaimplementowały metodę gradientu sprzężonego jako narzędzie nazwane Solver i umieściły je w swych szeroko oferowanych i popularnych arkuszach kalkulacyjnych: Excelu i Open Office Calc. W artykule pokazano także, jak precyzyjnie określić błędy oszacowania współrzędnych pozycji okrętu metodą Monte Carlo.

4

Preconditioned Conjugate Gradient Method for Solution of Large Finite Element Problems on CPU and GPU

Fialko S. Y., Zeglen F.

Journal of Telecommunications and Information Technology

|

2016

|

nr 2

26--33

EN

In this article the preconditioned conjugate gradient (PCG) method, realized on GPU and intended to solution of large finite element problems of structural mechanics, is considered. The mathematical formulation of problem results in solution of linear equation sets with sparse symmetrical positive definite matrices. The authors use incomplete Cholesky factorization by value approach, based on technique of sparse matrices, for creation of efficient preconditioning, which ensures a stable convergence for weakly conditioned problems mentioned above. The research focuses on realization of PCG solver on GPU with using of CUBLAS and CUSPARSE libraries. Taking into account a restricted amount of GPU core memory, the efficiency and reliability of GPU PCG solver are checked and these factors are compared with data obtained with using of CPU version of this solver, working on large amount of RAM. The real-life large problems, taken from SCAD Soft collection, are considered for such a comparison.

5

A PCG-PSO Image Reconstruction Algorithm For Electrical Capacitance Tomography System

Chen Y., Cao J., Chen D.

Przegląd Elektrotechniczny

|

2012

|

R. 88, nr 9b

37-41

EN

To solve the ‘soft-field’ nature and the ill-posed problem in electrical capacitance tomography (ECT) technology, this paper first presents a preconditioned conjugate gradient iterative algorithm for electrical capacitance tomography (PCG), Then, the results of the PCG algorithm using PSO method for imaging gray scale compensation.

PL

Artykuł przedstawia algorytm PCG (preconditioned conjugate gradient) do rekonstrukcji obrazu w elektrycznej pojemnościowe tomografii. Skala szarosci jest rekonstruowanoa przy wykorzystanoiu algorytmu PSO (particle swarm optimization).

6

Operator-splitting and Lagrange multiplier domain decomposition methods for numerical simulation of two coupled Navier-Stokes fluids

Bresch D., Koko J.

International Journal of Applied Mathematics and Computer Science

|

2006

|

Vol. 16, no 4

419-429

EN

We present a numerical simulation of two coupled Navier-Stokes flows, using operator-splitting and optimization-based nonoverlapping domain decomposition methods. The model problem consists of two Navier-Stokes fluids coupled, through a common interface, by a nonlinear transmission condition. Numerical experiments are carried out with two coupled fluids; one with an initial linear profile and the other in rest. As expected, the transmission condition generates a recirculation within the fluid in rest.