This paper presets a new algorithm for nonlinear distortion cancellation and channel re-estimation in an iterative manner. Whereas in practical OFDM systems, in which nonlinear amplifiers are used, data as well as pilot symbols are nonlinearly distorted. As perfect channel state information is often assumed in many works and papers, the effect of nonlinear distortion on pilot symbols is often not accounted for, and only data symbols are considered. However, as pilot symbols are used to obtain channel state information, distortion inflicted to pilot symbols by nonlinear amplification is of great importance, and for this reason should be accounted for. To address this issue, simple algorithm will be introduced for joint data recovery and channel re-estimation in an iterative manner. This algorithm iteratively estimates nonlinear distortion and then uses it to compensate this nonlinear distortion present at data and pilot symbols, which are then used for subsequent and more precise channel re-estimation. As it is shown in this paper, proposed algorithm can be used to reduce nonlinear distortions even in a situation, when highly nonlinear amplifiers are applied.
In this paper, we investigate pilot symbol assisted channel estimation in OFDM system. To obtain the consistent estimation of communication channel, it is necessary to perform filtration or interpolation on pilot symbols scattered in an OFDM frame. Different interpolation techniques on pilot symbols are investigated in this paper, concretely linear interpolation, Spline Interpolation, Cubic interpolation, Bezier curve interpolation and Lagrange barycentric interpolation. The performance of studied methods is then evaluated and compared by measuring the bit error rate (BER), mean squared error (MSE), mean absolute error (MAE) and root mean square error (RMSE) in frequency selective multipath Rayleigh fading channel. Results are then compared with perfect channel state information.
The article deals with analytical and experimental solution of vertical oscillations of a mechanical system of bound bodies. The content of the article is to perform an analytical solution of the vertical oscillation of a system of bodies using the computer program MathWorks Matlab and MS Excel. Furthermore, an experimental investigation on a laboratory model of a mechanical system of the same parameters was proved. The aim of the work was to compare the analytical solution with the experimental method and to check the accuracy and applicability of analytical methods for the solved mechanical system.
The article deals with the design of a robotic workplace for laser engraving. The first part of the article describes the importance of introducing robotics to industry 4.0. Custom solutions work is devoted to the implementation of the six-axis robotic arm UR10. This six-axis robotic arm inserts the designed jig with the semi-finished product into the engraving machine. In the engraving machine, the semi-finished product is engraved on the final product. This saves the operator time to pinpoint the position of the semi-finished product inside the engraving machine. The proposed jig is designed to be universal so that the position in the x-axis and in the y-axis can be precisely defined. At the end of the jig there is a bed for placing the semifinished product, which can be replaced by another in the case of other dimensions of the semi-finished product. The conclusion is a comparison of time savings in individual steps and overall engraving time savings for one engraved part.
The article deals with the measurement of conveyor belt noise and vibration. The conveyor belt was supported on six rollers fixed on three plates of stand, return and drive drum. These six rollers were produced in two sets (convectional tube and accurate tube). Rollers were driven by a rubber belt. The noise was measured and evaluated on both sides of the conveyor. Vibration of the conveyor was measured at four locations of the conveyor construction. All measurements were performed in an unloaded condition. In conclusion of the article is a summary and evaluation of all measurements. The vibration of the conveyor is comparable in both cases, however, the rollers from accuracy tube excite the construction less, and this results in a lower total noise. By comparing the acceleration to the dominant frequency, it is obvious that the noise and the vibration of the belt conveyor construction were reduced by using rollers from accuracy tube
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