Wyniki wyszukiwania - BazTech

1

Performance analysis of MPPM FSO transmission over Gamma–Chi-square strong atmospheric turbulence

Todorovic Jelena, Spalevic Petar, Panic Stefan, Abdullah Majid Hamid, Pantelic Ivan

Optica Applicata

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2023

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Vol. 53, nr 1

111--126

EN

In this paper, performance analysis of free space optical (FSO) system operating in conditions of strong atmospheric turbulence over Gamma–Chi-square turbulence model, has been carried out. We have observed reception over multi-pulse pulse-position (MPPM) modulation format for the case of strong atmospheric turbulence conditions modeled with Gamma–Chi-square turbulence model and have compared it with turbulence modeling distributions such are: Gamma–Gamma distribution, K-distribution, negative exponential distribution, log–normal distribution. First, we have provided closed-form analytical expressions for average bit error rate (ABER) at the reception for each observed case and then based on them, we have obtained numerical and Monte Carlo simulation results in order to observe turbulence level impact on system performance.

2

Pilot Based MMSE Channel Estimation for Spatial Modulated OFDM Systems

Soman Anetha Mary, Nakkeeran R., Shinu Mathew John

International Journal of Electronics and Telecommunications

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2021

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Vol. 67, No. 4

685--691

EN

Due to the multifold growth in demands of multimedia services and mobile data, the request for increased channel capacity in mobile and wireless communication has been quickly increasing. Developing a wireless system with more spectral efficiency under varying channel condition is a key challenge to provide more bit rates with limited spectrum. Multiple Input Multiple Output(MIMO) system with Orthogonal Frequency Division Multiplexing (OFDM) gives higher gain by using the direct and the reflected signals, thus facilitating the transmission at high data rate. An integration of Spatial Modulation (SM) with OFDM (SM OFDM) is a newly evolved transmission technique and has been suggested as a replacement for MIMO -OFDM transmission. In practical scenarios, channel estimation is significant for detecting transmitted data coherently. This paper proposes pilot based, Minimum Mean Square Error (MMSE) channel estimation for the SM OFDM communication system. We have focused on analyzing Symbol Error Rate (SER) and Mean Square error (MSE) under Rayleigh channel employing International Telecommunication Union (ITU) specified Vehicular model of Pilot based MMSE channel estimator using windowed Discrete Fourier Transform (DFT) and MMSE weighting function. Simulation output shows that proposed estimator’s SER performance lies close to that of the MMSE optimal estimator in minimizing aliasing error and suppressing channel noise by using frequency domain data windowing and time domain weighting function. Usage of the Hanning window eliminates error floor and has a compact side lobe level compared to Hamming window and Rectangular window. Hanning window has a larger MSE at low Signal to Noise Ratio (SNR) values and decreases with high SNR values. It is concluded that data windowing technique can minimize the side lobe level and accordingly minimize channel estimation error when interpolation is done. MMSE weighting suppresses channel noise and improves estimation performance. Since Inverse Discrete Fourier Transform(IDFT)/DFT transforms can be implemented with fast algorithms Inverse Fast Fourier Transform( IFFT)/Fast Fourier Transform(FFT) computational complexity can be remarkably reduced.

3

Modele symulacyjne kanałów w systemach radiokomunikacyjnych i ich charakterystyki

Noga K. M.

Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej

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2017

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Nr 57

71--76

PL

W artykule przedstawiono wybrane zagadnienia z zakresu symulacji kanałów radiokomunikacyjnych, tj. matematyczne modele propagacyjne, statystyczny opis szybkich zaników i powolnych fluktuacji. W artykule omówiono kanał wielodrogowy, mobilny Rayleigha oraz Wattersona. Jako narzędzie symulacyjne wybrano pakiet Vissim.

EN

The wireless channel can be described as a function of time and space. The received signal is the combinations of many replicas of the original signal. Multipath propagation produces several effects on the received signal, like time and frequency dispersion, amplitude fluctuation. The use of mathematical models describing the propagation of radio waves allows to simulate the propagation of different environment. In this paper fast and slow fading models and their characteristics are presented. A Rayleigh, mobile multipath and Watterson channel model are also described in this paper.

4

Modelowanie zaników sygnału jako skutku efektu Dopplera w dyspersyjnym środowisku propagacji

Kelner J. M., Ziółkowski C.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2016

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nr 6

443--446, CD

PL

Celem niniejszego artykułu jest ocena wpływu parametrów transmisyjnych środowiska propagacji na właściwości statystyczne zaników sygnału. Ocena ta jest pokazana na podstawie badań symulacyjnych, w których wykorzystany został wieloeliptyczny model propagacji. Jako miary intensywności zaników wykorzystano takie parametry jak częstość przekroczenia poziomu przez obwiednię sygnału i średnia długość zaniku. W zakresie właściwości statystycznych obwiedni uzyskane wyniki pokazują zgodność symulacji z wynikami analizy teoretycznej.

EN

The purpose of this paper is to assess the impact of the transmission parameters of propagation environment on the properties of statistical fading. Assessment is shown on the basis of simulation studies that multi-elliptical propagation model is used. Such parameters as level crossing rates and average fade durations are applied as a measure of intensity fading. In terms of statistical properties envelope, the obtained results show compliance of simulation results with a theoretical analysis.

5

Galvanic coupling intra-body communication channel model based on anisotropic muscular tissue

Shuang Z., Yuping Q., Pengun M., Siohang P., Mangi V.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 7

74--76

EN

Background: Characteristics of human tissues have direct effects on transmission property of the current signal in human tissues. It is learned from anatomy that, characteristics of all human tissues are not identical, and some like skin and fat are isotropic, while others like muscle are anisotropic. Muscular tissue has a great effect on transmission and distribution of the current signal in human body. Method: based on human tissue’s characteristics and boundary conditions under the quasi-static condition, the channel model based on human tissue’s characteristics is built in the cylindrical coordinate system by means of Maxwell equation. Furthermore, the model is verified through model calculation and experiments on human body. Results: in combination with electric parameters of human anisotropic tissue (muscle), the derived channel model is used to obtain computed results of the channel model with human tissue’s characteristics and the one without human tissue’s characteristics in MATLAB2010a. Next, these results are compared with the data obtained from measurement on human right forearm. It can be found from comparison that the gain curve of the channel model with human tissue’s characteristics is highly consistent with experimental data. Conclusion: The model with human tissue’s characteristics can show characteristics of the intra-body communication channel more accurately. On one hand, the channel precision is improved; on the other hand, it provides reference for building the implantable intra-body communication channel model with the transmission signal from inside to outside.

PL

Bazując na charakterystyce ludzkiego ciała i warunkach zewnętrznych określono model kanałowy wykorzystujący równani a Maxwella. Model weryfikowano eksperymentalnie.