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    Wyświetlanie 1-6 z 6
    Tytuł:
    Resource allocation in MIMO systems specific to radio communication
    Autorzy:
    Ghaderi, Bahar
    Parhizgar, Naser
    Powiązania:
    https://bibliotekanauki.pl/articles/140794.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    spatial modulation
    multi quadrature amplitude modulation
    modulation
    Huffman coding
    MIMO systems
    Opis:
    The performance of the multi-input multi-output (MIMO) systems can be improved by spatial modulation. By using spatial modulation, the transmitter can select the best transmit antenna based on the channel variations using channel state information (CSI). Also, the modulation helps the transmitter to select the best modulation level such that the system has the best performance in all situations. Hence, in this paper, two issues are considered including spatial modulation and information modulation selection. For the spatial modulation, an optimal solution for obtaining the probability of selecting antenna is calculated and then Huffman coding is used such that the transmitter can select the best transmit antenna to maximize the channel capacity. For the information modulation, a multi quadrature amplitude modulation (MQAM) strategy is used. In this modulation, the modulation size is changed based on the channel state variations; therefore, the best modulation index is used for transmitting data in all channel situations. In simulation results, the optimal method is compared with Huffman mapping. In addition, the effect of modulation on channel capacity and a bit error rate (BER) is shown.
    Źródło:
    Archives of Electrical Engineering; 2019, 68, 1; 91-100
    1427-4221
    2300-2506
    Pojawia się w:
    Archives of Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Pilot Based MMSE Channel Estimation for Spatial Modulated OFDM Systems
    Autorzy:
    Soman, Anetha Mary
    Nakkeeran, R.
    Shinu, Mathew John
    Powiązania:
    https://bibliotekanauki.pl/articles/2055222.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    MIMO
    multicarrier modulation
    spatial modulation
    channel estimation
    channel model
    interpolation
    Opis:
    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.
    Źródło:
    International Journal of Electronics and Telecommunications; 2021, 67, 4; 685--691
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance Analysis of SPSK with Dual Polarized Transmit Antennas over Rayleigh Fading Channel
    Autorzy:
    Subramani, M.
    Neduncheran, A. V.
    Ponnusamy, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/307739.pdf
    Data publikacji:
    2018
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    ABER
    dual polarized antenna
    Rayleigh fading
    spatial modulation
    SPSK
    SSK
    Opis:
    In this paper, the Space Polarization Shift Keying (SPSK) system, which is an extended version of Space Shift Keying (SSK) and includes both space and polarization dimensions with dual polarized antennas, is studied. The capacity and error probability analysis of SPSK for different polarization configurations are dealt with over the Rayleigh fading channel with a rich scattering environment. The analysis conducted shows that the SPSK with a dual polarized antenna (DP) offers better results than SPSK with a single orthogonal polarized antenna SPSK(SP), under non-LOS conditions. SPSK(DP) outperforms SSK by 4.2 dB over the correlated Rayleigh fading channel at 3 bits/s/Hz.
    Źródło:
    Journal of Telecommunications and Information Technology; 2018, 1; 58-61
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ergodic Channel Capacity of PPM-Coded Optical MIMO Communications Under Combined Effects
    Autorzy:
    Cao, Minghua
    Zhang, Yue
    Kang, Zhongjiang
    Wang, Huiqin
    Powiązania:
    https://bibliotekanauki.pl/articles/1844525.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    atmospheric channel
    ergodic channel capacity
    pulse position modulation
    spatial correlation
    optical wireless communication
    Opis:
    The ergodic channel capacity of wireless optical multiple-input multiple-output (MIMO) system with pulse position modulation (PPM) is investigated. The combined effects of atmospheric turbulence, atmospheric attenuation, pointing error and channel spatial correlation are taken into consideration. The expression of ergodic channel capacity is derived, and is further performed by Wilkinson approximation method for simplicity. The simulation results indicated that the strong spatial correlation has the greatest influence on the ergodic channel capacity, followed by pointing errors and atmospheric turbulence. Moreover, the ergodic channel capacity growth brought by space diversity only performs well under independent and weakly correlated channels. Properly increasing the size and spacing of the receiving apertures is an effective means of effectively increasing the ergodic channel capacity.
    Źródło:
    International Journal of Electronics and Telecommunications; 2021, 67, 3; 431-436
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    LCoS spatial light modulators as active phase elements of full-field measurement systems and sensors
    Autorzy:
    Kujawinska, M.
    Porras-Aguilar, R.
    Zaperty, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/221745.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    spatial light modulators
    liquid crystals on silicon
    phase modulation
    optical metrology
    active interferometry
    active microscopy
    digital holography
    Opis:
    Spatial light modulators (SLM) are devices used to modulate amplitude, phase or polarization of a light wave in space and time. Current SLMs are based either on MEMS (micro-electro-mechanical system) or LCD (liquid crystal display) technology. Here we report on the parameters, trends in development and applications of phase SLMs based on liquid crystal on silicon (LCoS) technology. LCoS technology was developed for front and rear projection systems competing with AMLCD (active matrix LCD) and DMD (Digital Mirror Device) SLM. The reflective arrangement due to silicon backplane allows to put a high number of pixels in a small panel, keeping the fill-factor ratio high even for micron-sized pixels. For coherent photonics applications the most important type of LCoS SLM is a phase modulator. In the paper at first we describe the typical parameters of this device and the methods for its calibration. Later we present a review of applications of phase LCoS SLMs in imaging, metrology and beam manipulation, developed by the authors as well as known from the literature. These include active and adaptive interferometers, a smart holographic camera and holographic display, microscopy modified in illuminating and imaging paths and active sensors.
    Źródło:
    Metrology and Measurement Systems; 2012, 19, 3; 445-458
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Bezpośrednia radiografia cyfrowa
    Digital direct radiography
    Autorzy:
    Jezierski, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/214636.pdf
    Data publikacji:
    2017
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    radiografia cyfrowa
    detektor typu płaski panel
    amorficzny krzem (a-Si:H)
    amorficzny selen
    częstotliwość przestrzenna
    funkcja przenoszenia modulacji (MTF)
    kwantowa wydajność detekcji (DQE)
    digital radiography
    flat panel detector
    amorphous silicon
    amorphous selenium
    spatial resolution
    modulation
    transfer function (MTF)
    detective quantum efficiency (DQE)
    Opis:
    Dynamiczny rozwój radiografii cyfrowej (bazującej na elektronice) jaki obserwujemy w ostatnich latach skutkuje także zastosowaniem tej techniki do badań nieniszczących w przemyśle (NDT). Jednakże biorąc pod uwagę istotne różnice, przede wszystkim znacznie wyższe energie promieniowania rentgenowskiego stosowane do badania różnych obiektów przemysłowych (np. złącza spawane, odlewy, połączenia w elektronice), jak również konieczność dysponowania niekiedy lekkimi, przenośnymi detektorami powoduje, że nie da się bezpośrednio przenieść rozwiązań z medycyny do przemysłu. W niniejszej publikacji przedstawiono współczesne trendy oraz praktyczne rozwiązania detektorów cyfrowych do zastosowań w NDT.
    Application of digital radiography (based on electronics) for imaging in medical practice has been recently dynamically developing, which results in implementation of this technique to industrial non-destructive testing (NDT). However, with respect to significant differences that include, first of all, much higher X-ray energies used for testing various object in industry (e.g. welds, castings, joints in electronic engineering) and often also necessity of using light, portable digital detectors, it is impossible to transfer solutions directly from medicine to industry. In this paper, modern trends and practical solutions of digital detectors designed for NDT are presented.
    Źródło:
    Postępy Techniki Jądrowej; 2017, 2; 37-44
    0551-6846
    Pojawia się w:
    Postępy Techniki Jądrowej
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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