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    Wyświetlanie 1-8 z 8
    Tytuł:
    Performance Improvements in SNR of a Multipath Channel Using OFDM-MIMO
    Autorzy:
    Enoch, Sharmini
    Otung, Ifiok
    Powiązania:
    https://bibliotekanauki.pl/articles/27311959.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    WiMAX
    fade mitigation
    OFDM
    MIMO
    cyclic prefix
    guard time
    Opis:
    The Non Line of Sight (NLOS) broadband wireless access provided by Worldwide Interoperability for Microwave Access (WiMAX) operating in 2-11 GHz frequency is susceptible to the effects of multipath propagation, diffraction fading, vegetation attenuation, shadowing loss etc. In order to overcome these effects effective fade mitigation techniques, have to be implemented. The Orthogonal Frequency Division Multiplexing- Multiple Input Multiple Output (OFDM-MIMO) is an efficient method that helps in combatting the fading and providing higher SNR to the WiMAX system. According to the IEEE 802.16 specification, for QPSK modulation, a threshold SNR of 6 dB is required for the link to operate. In the present work the use of OFDM-MIMO achieves a SNR above this operating threshold.
    Źródło:
    International Journal of Electronics and Telecommunications; 2023, 69, 4; 770--773
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigation of Vehicular S-LSTM NOMA Over Time Selective Nakagami-m Fading with Imperfect CSI
    Autorzy:
    Shankar, Ravi
    Chaudhary, Bhanu Pratap
    Mishra, Ritesh Kumar
    Powiązania:
    https://bibliotekanauki.pl/articles/2174454.pdf
    Data publikacji:
    2022
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    inter-symbol interference
    MIMO
    NOMA
    orthogonal frequency division multiplexing
    OFDM
    S-LSTM
    zero-mean circularly symmetric complex Gaussian
    ZM-CSCG
    Opis:
    In this paper, the performance of a deep learningbased multiple-input multiple-output (MIMO) non-orthogonal multiple access (NOMA) system is investigated for 5G radio communication networks. We consider independent and identically distributed (i.i.d.) Nakagami-m fading links to prove that when using MIMO with the NOMA system, the outage probability (OP) and end-to-end symbol error rate (SER) improve, even in the presence of imperfect channel state information (CSI) and successive interference cancellation (SIC) errors. Furthermore, the stacked long short-term memory (S-LSTM) algorithm is employed to improve the system’s performance, even under time-selective channel conditions and in the presence of terminal’s mobility. For vehicular NOMA networks, OP, SER, and ergodic sum rate have been formulated. Simulations show that an S-LSTM-based DL-NOMA receiver outperforms least square (LS) and minimum mean square error (MMSE) receivers. Furthermore, it has been discovered that the performance of the end-to-end system degrades with the growing amount of node mobility, or if CSI knowledge remains poor. Simulated curves are in close agreement with the analytical results.
    Źródło:
    Journal of Telecommunications and Information Technology; 2022, 4; 47--59
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance Improvement for Vehicular Communications Using Alamouti Scheme with High Mobility
    Autorzy:
    Youssefi, My Abdelkader
    Mouhsen, Ahmed
    Powiązania:
    https://bibliotekanauki.pl/articles/308551.pdf
    Data publikacji:
    2020
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    IEEE 802.11p
    MIMO
    MISO
    OFDM
    SFBC
    STBC
    vehicular channel
    Opis:
    The IEEE 802.11p standard is the basic protocol for wireless access in a vehicular environment (WAVE), providing high throughput for multimedia and high quality for vehicular transmissions. However, IEEE 802.11p fails to offer any multi-antenna approaches. In this paper, a multipleinput single-output (MISO) implementation with orthogonal frequency division multiplexing (OFDM), aiming to improve the performance of IEEE 802.11p, is proposed. The authors investigate the impact of time-varying channel on the performance of Alamouti space-time block codes (STBC) in OFDM systems. The Alamouti STBC approach shows good performance in slow time-varying environments, while its Alamouti space frequency block codes (SFBC) counterpart performs better over fast time-varying environments. An adaptive switching scheme is proposed to select appropriate spaceblock coding (STBC or SFBC) in vehicular channels with high mobility levels. It is shown that the proposed adaptive scheme provides better performance compared with traditional spaceblock codes.
    Źródło:
    Journal of Telecommunications and Information Technology; 2020, 3; 47-56
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    New OSTBC for Blind Channel Estimation and Tracking in MIMO-OFDM Systems
    Autorzy:
    Tami, Abdelkader
    Keche, Mokhtar
    Bouazza, Boubaker S.
    Powiązania:
    https://bibliotekanauki.pl/articles/958059.pdf
    Data publikacji:
    2019
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    MIMO
    OFDM
    blind channel estimation
    OSTBC
    SS-KCE
    Opis:
    Applying orthogonal space time block coding (OSTBC) to multiple-input multiple-output (MIMO) systems helps reduce receiver complexity. However, this approach has been applied only to flat fading channels, as when the channel is a frequency selective fading MIMO channel, OSTBC cannot be used directly since its orthogonal propriety may be lost. Furthermore, the MIMO channel is not always known. To deal with this problem, many techniques were proposed to estimate the channel using a training sequence. Unfortunately, these techniques reduce the useful spectral bandwidth. This paper proposes OSTBC for blind channel estimation and data detection in the case of a MIMO frequency selective channel. The aim of this new OSTBC is twofold: to solve the ambiguity of channel estimation and to reduce the complexity of the detector. By exploiting the well-known technique of orthogonal frequency division multiplexing (OFDM), the frequency selective fading MIMO channel is split into a set of flat fading subchannels. Moreover, to accommodate the fact that a MIMO channel can be time varying, the steady state Kalman channel estimator (SS-KCE) is extended to track the channel’s fast variations. The performance of the proposed blind algorithm is related by the adequate choice of the number of subcarriers and it is compared with other existing approaches by means of Monte Carlo simulations.
    Źródło:
    Journal of Telecommunications and Information Technology; 2019, 3; 49-57
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Improvement of LTE Downlink Channel Estimation Performance by Using an Adaptive Pilot Pattern
    Autorzy:
    Youssefi, M. A.
    Abbadi, J. E.
    Powiązania:
    https://bibliotekanauki.pl/articles/307570.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    channel estimation
    LTE
    MIMO
    OFDM
    pilot pattern
    Opis:
    This paper proposes an adaptive pilot pattern to improve channel estimation performance for LTE downlink system with high mobility. The downlink pilot positions are predefined in the time and frequency domain with fixed pilot pattern in LTE standard. However, that pilot structure is not efficient in a fast time varying channel, and leads to a decrease of channel estimation performance. The authors propose and evaluate the performance of LTE downlink channel estimation using an adaptive pilot scheme to optimally use pilot tones over time varying channels. It is shown that only seven bits of additional wide-band feedback per frame and per user are required to optimally support adaptive pilot pattern. Simulation results show that the proposed method allows high performance in terms of throughput and channel estimation error. This analysis shows that LTE downlink throughput could be increased over 4%.
    Źródło:
    Journal of Telecommunications and Information Technology; 2015, 2; 59-63
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the Comparison of Various Overhead Arrangements for Massive MIMO-OFDM Channel Estimation
    Autorzy:
    Sure, P.
    Bhuma, C. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/226978.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Massive MIMO-OFDM
    time domain synchronous
    comb type with cyclic prefix
    grid type with cyclic prefix
    denoising threshold
    LS channel estimation
    Opis:
    Massive multi input multi output (MIMO) systems incorporate orthogonal frequency division multiplexing (OFDM) technology to render high data rate services for future wireless communication applications. The channel estimator (CE) employed by a reliable massive MIMO-OFDM system requires huge amount of overhead in the form of known and null data transmissions, hence limiting the system spectral efficiency (SE). Often, CE design is a tradeoff between SE and system reliability. In this paper, CE with three different overhead arrangements, namely time domain synchronous (TDS), comb type with cyclic prefix (CTCP), 2D grid type with cyclic prefix (GTCP) are investigated and a GTCP based CE is proposed which offers both high SE and improved system reliability. The proposed CE uses autocorrelation based denoising threshold for channel impulse response (CIR) estimation and does not require any knowledge of channel statistics (KCS). A416 MIMO-OFDM system is simulated in a rayleigh fading channel environment with U-shaped doppler spectrum. From the bit error rate (BER) performance results in WiMax SUI-4, Advanced Television Technology Center (ATTC) and Brazil A channel environments, it is verified that the proposed CE with GTCP overhead and proposed denoising scheme, indeed improves both SE and system reliability. Hence it is suitable for application in all massive MIMO-OFDM systems.
    Źródło:
    International Journal of Electronics and Telecommunications; 2014, 60, 2; 173-179
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    MIMO versus SISO : simulation results
    Efektywność systemu MIMO względem SISO : wyniki badań symulacyjnych
    Autorzy:
    Michalak, J.
    Ziółkowski, C.
    Uljasz, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/210912.pdf
    Data publikacji:
    2012
    Wydawca:
    Wojskowa Akademia Techniczna im. Jarosława Dąbrowskiego
    Tematy:
    MIMO
    Alamouti
    OFDM
    SISO
    STBC
    Opis:
    Results of computer simulation tests of the STBC Alamouti MIMO 2×2 system in comparison to SISO were presented in this paper. The aim was to assess effectiveness of MIMO versus SISO in assumed propagation conditions. Depending on subscriber motion, propagation conditions as well as antenna system configuration, different results were received. In each configuration, MIMO system was not worse than SISO and many times it is significantly better than SISO with gain from a few to a dozen or so dB.
    W artykule zaprezentowano wyniki symulacji komputerowej systemu wieloantenowego MIMO 2×2 (ang. Multiple Input Multiple Output) z koderem STBC (ang. Space Time Block Coding) Alamoutiego w porównaniu do systemu SISO (ang. Single Input Single Output). Celem badania było określenie stopnia efektywności układu MIMO zależnie od prędkości i kierunku ruchu korespondenta, warunków propagacji oraz konfiguracji anten. Zależnie od założeń symulacyjnych uzyskano wyniki potwierdzające przewagę MIMO nad SISO w zakresie od kilku do kilkunastu dB.
    Źródło:
    Biuletyn Wojskowej Akademii Technicznej; 2012, 61, 1; 223-239
    1234-5865
    Pojawia się w:
    Biuletyn Wojskowej Akademii Technicznej
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Simulation Model of the Radio Frequency MIMO-OFDM System
    Autorzy:
    Kowal, M.
    Kubal, S.
    Piotrowski, P.
    Zieliński, R. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/226276.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    MIMO-OFDM
    Simulink
    simulator
    Opis:
    The paper presents a simulation model of the radio frequency MIMO-OFDM system. The simulation model was made in Matlab Simulink environment. It contains the transmitter, the receiver and the telecommunication channel models. The telecommunication channel model consists of models used during development of technical documentation of IEEE 802.11n. Signals generated at the transmitter output are fully compatible with signals described in IEEE 802.11n [1]. Simulations are conducted on a radio frequency, so they can be compared with results of measurements of real systems.
    Źródło:
    International Journal of Electronics and Telecommunications; 2011, 57, 3; 323-328
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-8 z 8

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