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    Wyświetlanie 1-6 z 6
    Tytuł:
    A model of OFDM based maritime VHF communication system for data exchange
    Autorzy:
    Valčić, S.
    Pogány, T.
    Mrak, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/260386.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    maritime VHF communications
    OFDM modulation
    AWGN
    SNR
    BER
    Opis:
    In the maritime Very High Frequency (VHF) band, there are no systems for transmitting large amounts of data. Therefore, it is necessary to develop new systems that would modernize the Global Maritime Distress and Safety System (GMDSS), significantly relieve the Automatic Identification System’s (AIS) communication channels, and set guidelines for the development of communication infrastructure of the e-Navigation. In line with this, analytical and simulation models of the maritime VHF data transmission communication system using Orthogonal Frequency Division Multiplexing (OFDM) modulation are worked out in this paper. The achieved data rate, the spectral efficiency and the bit error rate (BER) represent validation parameters on which the results of the analytical and simulation models are evaluated. It is concluded that the application of the digital OFDM modulation in the maritime VHF band may improve the GMDSS system by achieving higher data rates compared to the current terrestrial mandatory systems for data exchange, i.e. Digital Selective Calling (DSC) and AIS.
    Źródło:
    Polish Maritime Research; 2018, 2; 27-36
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dynamic RSA Problem for Time-Varying Traffic in Spectrum Sliced Elastic Optical Path Network
    Autorzy:
    Olszewski, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/226545.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    time-varying traffic
    dynamic RSA problem
    optical path
    OFDM modulation
    Opis:
    Service time-varying traffic flexible optical networks require a dynamic bandwidth allocation in order to follow the source transmission rate. The problem of service time-varying traffic, assuming that the set of connection requests is not known in advance, is considered in this work. Connection requests arrive randomly and have random durations. The considered dynamic RSA problem involves minimizing the probability of future connections blocking while maintaining spectrum continuity constraints and non-overlapping spectrum assignment constraints between spectrum-adjacent connections on the network links. The proposed algorithm determines the path with the required number of slots around the reference frequency for a connection request. An analysis of the network with time-varying traffic on the network connections was carried out on the basis of spectrum expansion/contraction schemes which allow to determine average blocking probability of the additional slot requests on these connections. The obtained results have been compared with those obtained by a well known algorithm that solves the dynamic RSA problem.
    Źródło:
    International Journal of Electronics and Telecommunications; 2015, 61, 2; 179-184
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Wymagania na rozdzielczość i nieliniowość przetwornika C/A dla sygnału OFDM
    Autorzy:
    Rudziński, A.
    Kozłowski, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/317702.pdf
    Data publikacji:
    2010
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    przetwornik cyfrowo-analogowy
    modulacja OFDM
    szum kwantyzacji
    nieliniowość całkowa
    nieliniowość różniczkowa
    digital-to-analog converter
    OFDM modulation
    quantization noise
    integral nonlinearity
    differential nonlinearity
    Opis:
    Przedstawiono model analityczny, umożliwiający wyznaczenie błędów wnoszonych do sygnału OFDM w procesie przetwarzania cyfrowo-analogowego. Zaproponowano wyrażenia do oszacowania wymaganej rozdzielczości i dopuszczalnych nieliniowości przetwornika C/A, gwarantujących utrzymanie zniekształceń sygnału poniżej założonego poziomu.
    Źródło:
    Telekomunikacja i Techniki Informacyjne; 2010, 3-4; 78-93
    1640-1549
    1899-8933
    Pojawia się w:
    Telekomunikacja i Techniki Informacyjne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    OFDM for Cognitive Radio Systems : Novel Power Allocation and Bit Loading Algorithms
    Autorzy:
    Razmi, Shirin
    Parhizgar, Naser
    Powiązania:
    https://bibliotekanauki.pl/articles/227256.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    cognitive radio
    OFDM
    interference constraints
    power allocation
    adaptive modulation
    bit loading
    Opis:
    A novel method to improve the performance of the frequency band is cognitive radio that was introduced in 1999. Due to a lot of advantages of the OFDM, adaptive OFDM method, this technique is used in cognitive radio (CR) systems, widely. In adaptive OFDM, transmission rate and power of subcarriers are allocated based on the channel variations to improve the system performance. This paper investigates adaptive resource allocation in the CR systems that are used OFDM technique to transmit data. The aim of this paper is to maximize the achievable transmission rate for the CR system by considering the interference constraint. Although secondary users can be aware form channel information between each other, but in some wireless standards, it is impossible for secondary user to be aware from channel information between itself and a primary user. Therefore, due to practical limitation, statistical interference channel is considered in this paper. This paper introduces a novel suboptimal power allocation algorithm. Also, this paper introduces a novel bit loading algorithm. In the numerical results sections, the performance of our algorithm is compared by optimal and conventional algorithms. Numerical results indicate our algorithm has better performance than conventional algorithms while its complexity is less than optimal algorithm.
    Źródło:
    International Journal of Electronics and Telecommunications; 2019, 65, 1; 139-145
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of hybrid PDM-4QAM-OFDM for inter-satellite/mechatronic telecommunication using FSO system
    Autorzy:
    Singh, Shivmanmeet
    Grewal, Narwant Singh
    Kaur, Baljeet
    Powiązania:
    https://bibliotekanauki.pl/articles/27315699.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    inter-satellite optical wireless communication
    IsOWC
    mechatronic telecommunication
    polarisation division multiplexing-quadrature amplitude modulation-orthogonal frequency division multiplexing
    PDM-4QAM-OFDM
    Opis:
    In this paper, the designing and simulation of 400 Gbps polarisation division multiplexingquadrature amplitude modulation-orthogonal frequency division multiplexing (PDM- 4QAM-OFDM)-based inter-satellite optical wireless communication (IsOWC)/mechatronic telecommunication system for improving the link information carrying capacity was carried out. With quadrature amplitude modulation (QAM) encoding, the performance of the executed system has been addressed using metrics such as signal to noise ratio (SNR) and total received power (RP). The performance with suggested system has been examined in relation to the effects of various factors such as operating wavelength, transmission power, and receiving pointing error angle. Moreover, a better identification method for improving connection reach between mechatronic devices/satellites has been revealed in this study. A performance comparison of the proposed system with other implemented approaches has been made in the final step.
    Źródło:
    Opto-Electronics Review; 2023, 31, 3; art. no. e147036
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evaluation of a high-speed hybrid OAM-OFDM-MDM multiplexed coherent FSO system under desert conditions
    Autorzy:
    Sinha, Shivaji
    Kumar, Chakresh
    Powiązania:
    https://bibliotekanauki.pl/articles/27310107.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    atmospheric attenuation
    bit error rate
    BER
    orbital angular momentum
    OAM
    optical signal-to-noise ratio
    OSNR
    orthogonal frequency division multiplexing
    OFDM
    quadrature amplitude modulation
    QAM
    transmission range
    Opis:
    To meet the needs of future wireless optical networks, this paper introduces a high-speed, hybrid multiplexed, coherent free-space optical (FSO) communication system that integrates an orbital angular momentum (OAM) multiplexed signal with an orthogonal frequency division multiplexing (OFDM) technique. Two independent QAM polarized beams, each carrying in-phase and quadrature (I/Q) phase 16-QAM-OFDM modulated data, are combined using mode division multiplexing (MDM) to increase the capacity of the proposed system. The reason of choosing OFDM is its capability to support higher data rate, and mitigating intersymbol interference (ISI). The signal is detected using a coherent detection-based digital signal processing (DSP) algorithm at the receiver end. The proposed hybrid FSO system is evaluated in low and heavy dust environments using bit error rate (BER), link distance, optical signal-to-noise ratio (OSNR), and received optical power performance matrices. The simulation results demonstrate the successful transmission of a 120 Gb/s single carrier over the longest link ranges of 1.5 and 0.40 km, respectively, under low and heavy dust weather environments below the signal degradation threshold value (forward error correction (FEC) limit) of BER 2.2 × 10–3 in strong turbulent conditions.
    Źródło:
    Optica Applicata; 2023, 53, 3; 431--445
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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