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    Wyświetlanie 1-22 z 22
    Tytuł:
    Implementation of Multiple Access Techniques Applicable for Maritime Satellite Communications
    Autorzy:
    Ilcev, S. D.
    Powiązania:
    https://bibliotekanauki.pl/articles/116635.pdf
    Data publikacji:
    2013
    Wydawca:
    Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
    Tematy:
    Global Maritime Distress and Safety System (GMDSS)
    Maritime Mobile Satellite Communications (MMSC)
    Multiple Access (MA)
    Multiple Access Techniques
    Code Division Multiple Access (CDMA)
    Time Division Multiple Access (TDMA)
    Frequency Division Multiple Access (FDMA)
    Random (Packet) Division Multiple Access (RDMA)
    Opis:
    In this paper are introduced fundamentals, characteristics, advantages and disadvantages of Multiple Access (MA) employed as transmission techniques in the Maritime Mobile Satellite Communications (MMSC) between ships and Coast Earth Station (CES) via Geostationary Earth Orbit (GEO) or Not-GEO satellite constellations. In fixed satellite communication, as a rule, especially in MMSC many users are active at the same time. The problem of simultaneous communications between many single or multipoint mobile satellite users can be solved by using MA technique, such as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), Space Division Multiple Access (SDMA) and Random (Packet) Division Multiple Access (RDMA). Since the resources of the systems such as the transmitting power and the bandwidth are limited, it is advisable to use the channels with complete charge and to create a different MA to the channel. This generates a problem of summation and separation of signals in the transmission and reception parts, respectively. Deciding this problem consists in the development of orthogonal channels of transmission in order to divide signals from various users unambiguously on the reception part.
    Źródło:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2013, 7, 4; 529-540
    2083-6473
    2083-6481
    Pojawia się w:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of an LSTM-based NOMA Detector Over Time Selective Nakagami-m Fading Channel Conditions
    Autorzy:
    Shankar, Ravi
    Bangare, Jyoti L.
    Kumar, Ajay
    Gupta, Sandeep
    Mehraj, Haider
    Kulkarni, Shriram S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2142313.pdf
    Data publikacji:
    2022
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    deep learning
    DL
    multiple-input multiple-output
    MIMO
    non-orthogonal multiple access
    NOMA
    orthogonal multiple access
    OMA
    Opis:
    This work examines the efficacy of deep learning (DL) based non-orthogonal multiple access (NOMA) receivers in vehicular communications (VC). Analytical formulations for the outage probability (OP), symbol error rate (SER), and ergodic sum rate for the researched vehicle networks are established Rusing i.i.d. Nakagami-m fading links. Standard receivers, such as least square (LS) and minimum mean square error (MMSE), are outperformed by the stacked long-short term memory (S-LSTM) based DL-NOMA receiver. Under real time propagation circumstances, including the cyclic prefix (CP) and clipping distortion, the simulation curves compare the performance of MMSE and LS receivers with that of the DL-NOMA receiver. According to numerical statistics, NOMA outperforms conventional orthogonal multiple access (OMA) by roughly 20% and has a high sum rate when considering i.i.d. fading links.
    Źródło:
    Journal of Telecommunications and Information Technology; 2022, 3; 17--24
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    CG-SCMA Codebook Design Based on Maximized Euclidian Distance
    Autorzy:
    Mohamed, Sura S.
    Abdullah, Hikmat N.
    Powiązania:
    https://bibliotekanauki.pl/articles/2200958.pdf
    Data publikacji:
    2023
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    codebook
    Euclidian distance
    MPA
    multiple access
    sparse code
    Opis:
    Sparse code multiple access (SCMA) is a multi-dimensional codebook based on a class of non-orthogonal multiple access (NOMA) technologies enabling the delivery of non-orthogonal resource elements to numerous users in 5G wireless communications without increasing complexity. This paper proposes a computer-generated sparse code multiple access (CG-SCMA) technique, where the minimum Euclidian distance (MED) of a star 16-point quadrature amplitude modulation is maximized by CG-SCMA, thus creating a complex SCMA codebook based on optimizing the difference between the first and other radiuses over rotated constellations. To specify the most suitable values for this constellation, it is divided into four sub-constellations using trellis coded modulation (TCM) in an effort to optimize MED. The new codebook has four sub-constellations with MED values of 3.85, 2.26, 2.26, and 3.85, respectively. Application of the message passing algorithm (MPA) ensures low complexity of the decoding process
    Źródło:
    Journal of Telecommunications and Information Technology; 2023, 1; 18--24
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance improvement of a novel zero cross-correlation code using Pascal’s triangle matrix for SAC-OCDMA systems
    Autorzy:
    Driz, Samia
    Fassi, Benattou
    Kandouci, Chahinaz
    Ghali, Fodil
    Powiązania:
    https://bibliotekanauki.pl/articles/2063900.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    multiple access interference
    pascal’s triangle matrix
    quality of service
    spectral amplitude coding-optical code division multiple access
    zero cross-correlation
    Opis:
    In order to minimize the receiver complexity and improve the performance of the spectral amplitude coding - optical code division multiple access system, a novel one-dimensional zero cross-correlation code using Pascal’s triangle matrix has been suggested. This research article shows that the position of chip “1” in the code sequences is one of the important factors affecting system performance. In fact, mathematical results show that, for the allwavelength direct detection, it is possible to reduce the number of filters without sacrificing system performance. In addition, compared to one-wavelength direct detection, the signalto-noise ratio value is increased with an increasing weight by using wide-bandwidth filters as decoders. Performance of the proposed system in terms of the minimum bit error rate is validated using the OptiSystem software. Compared with the previous systems at 622 Mbps, the suggested system gave the best values of bit error rate of around 10⁻⁴³, 10⁻³⁵, and 10⁻²⁶ for higher, medium, and lower service demand, respectively.
    Źródło:
    Opto-Electronics Review; 2022, 30, 1; 1--7
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Power Allocation for Energy-Harvesting-based Fading Cognitive Multiple Access Channels : with or without Successive Interference Cancellation
    Autorzy:
    Li, Q.
    Xu, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/963855.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    cognitive radio
    power allocation
    multiple access channels
    energy harvesting
    Opis:
    This paper considers a fading cognitive multiple access channel (CMAC), where multiple secondary users (SUs), who share the spectrum with a primary user (PU), transmit to a cognitive base station (CBS). A power station is assumed to harvest energy from the nature and then provide power to the SUs. We investigate the power allocation problems for such a CMAC to maximize the SU sum rate under the interference power constraint, the sum transmit power constraint and the peak transmit power constraint of each individual SU. In particular, two scenarios are considered: with successive interference cancellation (SIC) and without SIC. For the first scenario, the optimal power allocation algorithm is derived. For the second scenario, a heuristic algorithm is proposed. We show that the proposed algorithm with SIC outperforms the algorithm without SIC in terms of the SU sum rate, while the algorithm without SIC outperforms the algorithm with SIC in terms of the number of admitted SUs for a high sum transmit power limit and a low peak transmit power limit of each individual SU.
    Źródło:
    International Journal of Electronics and Telecommunications; 2017, 63, 1; 65-72
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of SHIFTZCC codes for Optical CDMA system
    Autorzy:
    Panda, Satyasen
    Powiązania:
    https://bibliotekanauki.pl/articles/1178705.pdf
    Data publikacji:
    2017
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    cross correlation (CC)
    multiple access interference (MAI)
    optical code division multiple access (OCDMA)
    shift zero cross correlation code (SHIFTZCC) and signal to noise ratio (SNR)
    spectral amplitude coding optical code division multiple access (SAC-OCDMA)
    Opis:
    In this paper, we propose a novel SAC-OCDMA code called Shift Zero Cross Correlation (SHIFTZCC) code with zero cross correlation property to minimize the Multiple Access Interface (MAI), to be more scalable and secure compared to the other existing SAC-OCDMA codes. This SHIFTZCC code is constructed using address segment and data segment. In this work, the proposed SHIFTZCC code is implemented in an optical network using the Opti-System software for the spectral amplitude coded optical code division multiple access (SAC-OCDMA) scheme. The chief advantage of the proposed SHIFTZCC code is the zero cross correlation property, which reduces both the MAI and other noises improving the system performance. The proposed SHIFTZCC code provides flexibility in selecting the code parameters, supports a large number of users with higher data rate and longer fiber length. Simulation results prove that the optical code division multiple access system based on the proposed SHIFTZCC code supports maximum number of simultaneous users with higher transmission rate, lower bit error rates (BER) and longer travelling distance without any signal quality degradation, as compared to the former existing SAC-OCDMA codes.
    Źródło:
    World Scientific News; 2017, 67, 2; 365-389
    2392-2192
    Pojawia się w:
    World Scientific News
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Reduction of BER using RSC code for Optical Code Division Multiple Access Networks
    Autorzy:
    Panda, Satyasen
    Powiązania:
    https://bibliotekanauki.pl/articles/1178316.pdf
    Data publikacji:
    2017
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    Cross Correlation (CC)
    Multiple Access Interface (MAI)
    Optical Code Division Multiple Access (OCDMA)
    Random Sparse Code (RSC)
    Wavelength hopping time spreading (WHTS)
    Opis:
    In this study, a two dimensional (2-D) wavelength hopping and time spreading (WHTS) optical code division multiple access (OCDMA) code is designed using Sparse ruler technique. The proposed 64 bit 2-D code is constructed by an algorithm based on random spacing of sparse codes referred in this work as Random Sparse Code (RSC). The performance of the proposed 2-D RSC is evaluated in terms of bit error rate (BER), received signal power and time domain analysis of received signals. The system performance of the OCDMA system utilizing 2-D RSC code improved significantly due to less BER, low cross correlation property and simple encoder/decoder design. The output BER is much lower at a data rate of 1.25 gbps and 2.5 gbps for a distance of 100 km with ITU-T standard single mode fiber with attenuation level of 0.2dB/km.
    Źródło:
    World Scientific News; 2017, 81, 2; 106-120
    2392-2192
    Pojawia się w:
    World Scientific News
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    CDMA wireless system with blind multiuser detector
    Autorzy:
    Leong, W. Y.
    Homer, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/309140.pdf
    Data publikacji:
    2006
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    code division multiple access
    independent component analysis
    blind source separation
    Opis:
    In this paper we present an approach capable of countering the presence of multiple access interference (MAI) in code division multiple access (CDMA) channels. We develop and implement a blind multiuser detector, based on an independent component analysis (ICA) to mitigate both MAI and noise. This algorithm has been utilized in blind source separation (BSS) of unknown sources from their linear mixtures. It can also be used for estimation of the basis vectors of BSS. The aim is to include an ICA algorithm within a wireless receiver in order to reduce the level of interference in CDMA systems. This blind multiuser detector requires less precise knowledge of the channel than does the conventional single-user receiver. The proposed blind multiuser detector is made robust with respect to imprecise knowledge of the received signature waveforms of the user of interest. Several experiments are performed in order to verify the validity of the proposed learning algorithm.
    Źródło:
    Journal of Telecommunications and Information Technology; 2006, 1; 69-75
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optimum double-matched detection and its application to SSMA systems
    Autorzy:
    Pawelec, J.J.
    Powiązania:
    https://bibliotekanauki.pl/articles/309576.pdf
    Data publikacji:
    2001
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    optimum detection
    spread spectrum multiple access systems
    NB interference
    adaptation
    Opis:
    This paper is concerned with the issue of optimum detection of known signal in nonwhite noise and/or narrow-band interferences. The detection is carried out in three steps. First, some function related to the power spectrum of interfering process I(z) is estimated via adaptation. Second, the signal + interference is withened due to I(z). Third, the replica of signal is filtered via I(z) to match it to the deformed signal in the previous step. The simulation of SS reception in presence of NB interference shows a high gain in comparison to classical single-matched detection.
    Źródło:
    Journal of Telecommunications and Information Technology; 2001, 3; 80-85
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Secrecy Rate Region Enhancement in Multiple Access Wiretap Channel
    Autorzy:
    Shah, Shahid Mehraj
    Powiązania:
    https://bibliotekanauki.pl/articles/2142307.pdf
    Data publikacji:
    2022
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    multiple access channels
    physical layer security
    strong secrecy
    wiretap channel
    Opis:
    It is commonly known that physical layer security is achieved with a trade-off in terms of the achievable rate. Hence, security constraints generate rate losses in wiretap channels. To mitigate such rate losses in multi-user channels, we propose a coding/decoding scheme for multi-user multiple access wiretap channel (MAC-WT), where previously transmitted messages are used as a secret key to enhance the secrecy rates of the transmitting users, until the usual Shannon capacity region of a multiple access channel (MAC) is achieved without the secrecy constraint. With this coding scheme, all messages transmitted in the recent past are secure with respect to all the information of the eavesdropper till now. To achieve this goal, we introduce secret key buffers at both the users and the legitimate receiver. Finally, we consider a fading MAC-WT and show that with this coding/decoding scheme, we can achieve the capacity region of a fading MAC channel (in the ergodic sense).
    Źródło:
    Journal of Telecommunications and Information Technology; 2022, 2; 14--25
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Uplink NOMA Scheme for Wi-Fi Applications
    Autorzy:
    Ghazi, H. S.
    Wesołowski, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/226180.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    5G
    Non-Orthogonal Multiple Access
    NOMA
    Successive Interference Cancellation
    SIC
    Opis:
    Non-Orthogonal Multiple Access (NOMA) with Successive Interference Cancellation (SIC) is one of the promising techniques proposed for 5G systems. It allows multiple users with different channel coefficients to share the same (time/frequency) resources by allocating several levels of (power/code) to them. In this article, a design of a cooperative scheme for the uplink NOMA Wi-Fi transmission (according to IEEE 802.11 standards) is investigated. Various channel models are exploited to examine the system throughput. Convolutional coding in conformance to IEEE 802.11a/g is applied to evaluate the system performance. The simulation results have been addressed to give a clear picture of the performance of the investigated system.
    Źródło:
    International Journal of Electronics and Telecommunications; 2018, 64, 4; 481-485
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analyses of Code Division Multiple Access (CDMA) Schemes for Global Mobile Satellite Communications (GMSC)
    Autorzy:
    Ilcev, D. S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1841573.pdf
    Data publikacji:
    2020
    Wydawca:
    Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
    Tematy:
    Global Mobile Satellite Communications
    Code Division Multiple Access
    Multiple Access Technique
    Satellite Communication Systems
    Mobile Earth Station
    orthogonal channels of transmission
    GMSC Networks
    very small aperture terminals
    Opis:
    This paper describes in particular Code Division Multiple Access (CDMA) applicable in Global Mobile Satellite Communications (GMSC). In satellite communication systems, as a rule, especially in GMSC networks many users are active at the same time. The problem of simultaneous communications between many single or multipoint mobile satellite users, however, can be solved by using Multiple Access Technique (MAT) system. Since the resources of the systems such as the transmitting power and the bandwidth are limited, it is advisable to use the channels with complete charge and to create a different MAT to the channel. This generates a problem of summation and separation of signals in the transmission and reception parts, respectively. Deciding this problem consists in the development of orthogonal channels of transmission in order to divide signals from various users unambiguously on the reception part.
    Źródło:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2020, 14, 4; 805-810
    2083-6473
    2083-6481
    Pojawia się w:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Comparative Analysis of NOMA and OMA Schemes: GSVD-based NOMA Systems and the Role of Mobile Edge Computing
    Autorzy:
    Dursun, Yunus
    Powiązania:
    https://bibliotekanauki.pl/articles/24200752.pdf
    Data publikacji:
    2023
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    generalized singular value decomposition
    MIMO
    mobile edge computing
    non-orthogonal multiple-access
    Opis:
    This paper presents a comprehensive study that examines the fundamental concept of the non-orthogonal multiple access (NOMA) scheme and provides its detailed comparison with the orthogonal multiple access (OMA) technique. Furthermore, the paper explores the application of the generalized singular value decomposition (GSVD) method in conjunction with NOMA, accompanied by a detailed review of GSVD-based NOMA systems. This study also introduces the concept of mobile edge computing (MEC) and extensively discusses its key parameters. Furthermore, a comprehensive analysis of NOMA MEC is presented, shedding light on its potential advantages and challenges. The aims of this study are to provide a comprehensive understanding of the aforementioned topics and contribute to the advancement of MIMO-NOMA systems.
    Źródło:
    Journal of Telecommunications and Information Technology; 2023, 3; 11--20
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Design Low Complexity SCMA Codebook Using Arnold’s Cat Map
    Autorzy:
    Mohamed, Sura S.
    Abdullah, Hikmat N.
    Powiązania:
    https://bibliotekanauki.pl/articles/2174447.pdf
    Data publikacji:
    2022
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    chaotic interleaving
    codebook design
    dimension rotation
    Euclidean distance
    sparse code multiple access
    Opis:
    In 5G wireless communications, sparse code multiple access (SCMA) – a multi-dimensional codebook based on a specific category of the non-orthogonal multiple access (NOMA) technique - enables many users to share non-orthogonal resource components with a low level of detection complexity. The multi-dimensional SCMA (MD-SCMA) codebook design presented in this study is based on the constellation rotation and interleaving method. Initially, a subset of the lattice Z 2 is used to form the mother constellation’s initial dimension. The first dimension is then rotated to produce other dimensions. Additionally, interleaving is employed for even dimensions to enhance fading channel performance. Arnold’s chaotic cat map is proposed as the interleaving method to reduce computational complexity. Performance of the SCMA codebook based on interleaving is evaluated by comparing it with selected codebooks for SCMA multiplexing. The metrics used for performance evaluation purposes include bit error rate (BER), peak to average power ratio (PAPR), and minimum Euclidean distance (MED), as well as complexity. The results demonstrate that the suggested codebook with chaotic interleaving offers performance that is equivalent to that of the conventional codebook based on interleaving. It is characterized by lower MED and higher BER compared to computer-generated and 16-star QAM codebook design approaches, but its complexity is lower than that of the conventional codebook based on interleaving.
    Źródło:
    Journal of Telecommunications and Information Technology; 2022, 4; 13--20
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Three dimensional optical CDMA framework with direct detection technique
    Autorzy:
    Panda, Satyasen
    Powiązania:
    https://bibliotekanauki.pl/articles/1178377.pdf
    Data publikacji:
    2017
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    Cross correlation (CC)
    Multiple access interference (MAI)
    Phase induced intensity noise (PIIN)
    Spectral amplitude coding optical code division multiple access (SAC-OCDMA)
    Three dimensional modified quadratic congruence/prime hop code (3-D MQC/PHC)
    Three dimensional optical code division multiple access (3-D OCDMA)
    Opis:
    In this paper, a three-dimensional (3-D) wavelength/time/space code is developed for optical code division multiple access (OCDMA) networks with direct detection technique in the receiver side. The 3-D codes are developed by mixing two-dimensional modified quadratic congruence (MQC) code and one-dimensional prime hop code (PHC) code. The encoders and decoders are constructed using fiber Bragg gratings and delay lines to minimize the bit error rate (BER). The performance analysis of the 3-D OCDMA system is based on measurement of signal to noise ratio (SNR), BER, received power and eye diagram for different numbers of simultaneous users. Also, in the analysis, various types of noises and multiple access interference (MAI) effects are considered. The received optical power is also measured at various levels of BER to analyze the effect of attenuation.
    Źródło:
    World Scientific News; 2017, 77, 2; 337-353
    2392-2192
    Pojawia się w:
    World Scientific News
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Underwater Acoustic Sensor Node Scheduling using an Evolutionary Memetic Algorithm
    Autorzy:
    Sivakumar, V.
    Rekha, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/307911.pdf
    Data publikacji:
    2018
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    broadcast UASN scheduling
    memetic algorithm
    time division multiple access
    underwater acoustic sensor network
    Opis:
    Underwater Acoustic Sensor Networks (UWASNs) play an important role in monitoring the aqueous environment which has created a lot of interest for researchers and scientists. Utilization of underwater acoustic sensor node (UASN) scheduling for transmission remains, due to the limited acoustic bandwidth available, a challenge in such an environment. One of the methods to overcome this problem is to efficiently schedule UASN data using time division multiple access (TDMA) protocols the parallel transmissions, simultaneously avoiding interference. The paper shows how to optimize the utilization of acoustic sensor node bandwidth by maximizing the possible node transmissions in the TDMA frame and also by minimizing the node's turnaround wait time for its subsequent transmissions by using an evolutionary memetic algorithm (MA). The simulation of MA-TDMA proves that as the size of the network increases, every node in UWASN transmits with an average minimal turnaround transmission time. It also proves that as the TDMA cycle repeats, the overall network throughput gets maximized by increasing the possible node transmissions in the MA-TDMA frame.
    Źródło:
    Journal of Telecommunications and Information Technology; 2018, 1; 88-94
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance Analysis of Filtered OFDM Based Downlink and Uplink NOMA System over Nakagami-m Fading Channel
    Autorzy:
    Mukhtar, Shaika
    Begh, Gh. Rasool
    Powiązania:
    https://bibliotekanauki.pl/articles/1839342.pdf
    Data publikacji:
    2021
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    bit error rate
    orthogonal multiple access
    out-of-band emission
    successive interference cancellation
    Opis:
    Efficient consumption of available resources and fulfillment of increasing demands are the two main challenges which are addressed by exploring advanced multiple access schemes along with efficient modulation techniques. To this end, non-orthogonal multiple access (NOMA) is discussed as a promising scheme for future 5G traffic. NOMA enables the users to share same resource block, permitting certain level of interference. In this paper, we propose filtered OFDM (F-OFDM) as a transmission waveform for NOMA systems, as it offers all the advantages of OFDM with the additional provision of sub-band filtering to satisfy the diverse services of the users. We examine F-OFDM in both downlink and uplink NOMA systems. Error-related performances of both downlink and uplink F-OFDM NOMA systems are analyzed and compared with conventional OFDM NOMA system over Nakagami-m fading channel. The results show that the error performance of F-OFDM NOMA is better than that of OFDM NOMA. An improvement of about 2 dB and 1 dB in bit error rate is achieved in downlink and uplink F-OFDM NOMA, respectively. Monte Carlo simulations are conducted for different values of fading parameter m, supporting the obtained analytical results.
    Źródło:
    Journal of Telecommunications and Information Technology; 2021, 2; 11-23
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An Approximate Evaluation of BER Performance for Downlink GSVD-NOMA with Joint Maximum-likelihood Detector
    Autorzy:
    Hai, Ngo Thanh
    Khoa, Dang Le
    Powiązania:
    https://bibliotekanauki.pl/articles/2142315.pdf
    Data publikacji:
    2022
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    generalized singular value decomposition
    GSVD
    joint maximum-likelihood
    joint modulation
    MIMO
    non-orthogonal multiple access
    NOMA
    Opis:
    Generalized Singular Value Decomposition (GSVD) is the enabling linear precoding scheme for multiple-input multiple-output (MIMO) non-orthogonal multiple access (NOMA) systems. In this paper, we extend research concerning downlink MIMO-NOMA systems with GSVD to cover bit terror rate (BER) performance and to derive an approximate evaluation of the average BER performance. Specifically, we deploy, AT the base station, the well-known technique of joint-modulation to generate NOMAsymbols and joint maximum-likelihood (ML) to recover the transmitted data at end user locations. Consequently, the joint ML detector offers almost the same performance, In terms of average BER as ideal successive interference cancellation. Next, we also investigate BER performance of other precoding schemes, such as zero-forcing, block diagonalization, and simultaneous triangularization, comparing them with GSVD. Furthermore, BER performance is verified in different configurations in relation to the number of antennas. In cases where the number of transmit antennas is greater than twice the number of receive antennas, average BER performance is superior.
    Źródło:
    Journal of Telecommunications and Information Technology; 2022, 3; 25--37
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Suitable Spreading Sequences for Asynchronous MC-CDMA Systems
    Autorzy:
    Addad, M.
    Djebbari, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/307793.pdf
    Data publikacji:
    2018
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    BER
    crest factor
    multiple access interference
    MC-CDMA
    peak-to-average power ratio
    zero correlation zone
    Opis:
    In order to meet the demand of high data rate transmission with good quality maintained, the multi-carrier code division multiple access (MC-CDMA) technology is considered for the next generation wireless communication systems. However, their high crest factor (CF) is one of the major drawbacks of multi-carrier transmission systems. Thus, CF reduction is one of the most important research areas in MC-CDMA systems. In addition, asynchronous MC-CDMA suffers from the effect of multiple access interference (MAI), caused by all users active in the system. Degradation of the system’s bit error rate (BER) caused by MAI must be taken into consideration as well. The aim of this paper is to provide a comparative study on the enhancement of performance of an MC-CDMA system. The spreading sequences used in CDMA play an important role in CF and interference reduction. Hence, spreading sequences should be selected to simultaneously ensure low CF and low BER values. Therefore, the effect that correlation properties of sequences exert on CF values is investigated in this study. Furthermore, a numerical BER evaluation, as a function of the signal-to-noise ratio (SNR) and the number of users, is provided. The results obtained indicate that a trade-off between the two criteria is necessary to ensure good performance. It was concluded that zero correlation zone (ZCZ) sequences are the most suitable spreading sequences as far as the satisfaction of the above criteria is concerned.
    Źródło:
    Journal of Telecommunications and Information Technology; 2018, 3; 9-13
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Full-duplex Cognitive Radio NOMA Networks : Outage and Throughput Performance Analysis
    Autorzy:
    Tran, Thanh-Nam
    Do, Dinh-Thuan
    Voznak, Miroslav
    Powiązania:
    https://bibliotekanauki.pl/articles/226091.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Non-Orthogonal Multiple Access (NOMA)
    Cognitive Radio (CR)
    full-duplex (FD)
    outage probability
    system throughput
    achievabe bit rate
    Opis:
    A novel non-orthogonal multiple access (NOMA) scheme is proposed to improve the throughput and the outage probability of the cognitive radio (CR) inspired system which has been implemented to adapt multiple services in the next-generation network (5G). In the proposed scheme, the primary source (PS) had sent a superposition code symbol with a predefined power allocation to relays, it decoded and forwarded (DF) a new superposition coded symbol to the destination with the other power allocation. By using a dual antenna at relays, it will be improved the bandwidth efficiency in such CR NOMA scheme. The performance of the system is evaluated based on the outage probability and the throughput with the assumption of the Rayleigh fading channels. According to the results obtained, it is shown that the outage probability and throughput of the proposed full-duplex (FD) in CR-NOMA with reasonable parameters can be able deploy in practical design as illustration in numerical results section.
    Źródło:
    International Journal of Electronics and Telecommunications; 2019, 65, 1; 103-109
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ranking of LTE cells based on key performance indicators using MCDM methods
    Autorzy:
    Lopes Neto, Pedro Nunes
    Freire Junior, José Celso
    Tuna, Celso Eduardo
    Powiązania:
    https://bibliotekanauki.pl/articles/2211970.pdf
    Data publikacji:
    2022
    Wydawca:
    Uniwersytet Ekonomiczny w Katowicach
    Tematy:
    long-term evolution
    multiple criteria methods
    radio access network performance management
    self-organizing networks
    Opis:
    The growth in worldwide data traffic and user subscriptions in mobile telecommunication networks makes it increasingly difficult to manage network performance in an environment already containing multiple radio access technologies. Despite the rise of 5G, LTE remains the dominant technology, and new cells are installed daily to support traffic growth and new services such as voice over LTE. Detecting faulty cells in the network is one of the main concerns of operators. Self organizing networks have been introduced to deal with this problem, and their self healing functionality has improved cell fault management. Nonetheless, faulty cell detection remains challenging, and most of the tasks involved are still done manually. This paper introduces a new method of faulty cell detection in an LTE radio access network, applying multiple criteria methods to this problem. The cells are ranked based on selected key performance indicators, using the multi attribute utility theory to construct a utility function. The analytic hierarchy process is used to define weights for the criteria.
    Źródło:
    Multiple Criteria Decision Making; 2022, 17; 46-68
    2084-1531
    Pojawia się w:
    Multiple Criteria Decision Making
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Network Selection in Wireless Heterogeneous Networks: a Survey
    Autorzy:
    Bendaoud, F.
    Abdennebi, M.
    Didi, F.
    Powiązania:
    https://bibliotekanauki.pl/articles/309296.pdf
    Data publikacji:
    2018
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    always best connected
    fuzzy logic
    game theory
    multiple attribute decision making
    quality of service
    radio access technologies
    Opis:
    Heterogeneous wireless networks is a term referring to networks combining different radio access technologies with the aim of establishing the best connection possible. In this case, users with multi-mode terminals can connect via different wireless technologies, such as 802.16, 802.11, UMTS, HSPA and LTE, all at the same time. The problem consists in the selection of the most suitable from all radio access technologies available. The decision process is called network selection, and depends on several parameters, such as quality of service, mobility, cost, energy, battery life, etc. Several methods and approaches have been proposed in this context, with their objective being to offer the best QoS to the users, and/or to maximize re-usability of the networks. This paper represents a survey of the network selection methods used. Multiple attribute-dependent decision-making methods are presented. Furthermore, the game theory concept is illustrated, the use of the fuzzy logic is presented, and the utility functions defining the network selection process are discussed.
    Źródło:
    Journal of Telecommunications and Information Technology; 2018, 4; 64-74
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-22 z 22

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