Artykuły w czasopismach na temat „Channel access methods”
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Cao, Zhan Mao, i Jian Chao Tang. "Routing Methods and Scheduling Patterns in MIMO WMN Virtual Model". Applied Mechanics and Materials 519-520 (luty 2014): 216–21. http://dx.doi.org/10.4028/www.scientific.net/amm.519-520.216.
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Multi-input multi-output wireless mesh networks (MIMO WMNs) act as backbone broadband networks for ubiquitous access. Topology model is a crucial factor in interference avoidance, simplifying channel allocation, and discussing optimal scheduling and routing. Cartesian product of graphs (CPG) is introduced for MIMO WMN as a virtual topology. By putting orthogonal channels into different channel layer meshes, some conclusions are explored on channel allocation, routing and scheduling. A path coherent realization is composed of combinatorial edges over multiple channels for all hops. Some important property propositions in CPG are also given, such as path hops with node address and path number counting. Practical mesh node addressing scheme and path number counting theorems are useful virtual topology properties.
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Dai, Yuan-Kao, Li-Hsing Yen i Jia-Wei Su. "Toward an Access Infrastructure for Mobile Cloud". International Journal of Grid and High Performance Computing 5, nr 3 (lipiec 2013): 6–19. http://dx.doi.org/10.4018/jghpc.2013070102.
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The provision of mobile cloud service calls for a wireless access infrastructure that offers high bandwidth to mobile users. Among all enabling technologies, wireless mesh networks (WMNs) have the advantage of low deployment cost and widely available user equipments. To provide more bandwidth, access points in WMNs are commonly equipped with multiple wireless interfaces (radios) that can operate on multiple non-overlapping channels in parallel. The objective of channel assignments in a multi-channel, multi-radio MWN is to reduce co-channel interference experienced by links so as to increase network capacity while maintaining network connectivity. Prior studies addressing this issue majorly considered effects of co-channel interference at the link layer. In this study, the authors consider co-channel interference at the physical layer. Furthermore, most existing methods are based on heuristic or game theory. This study applies simulated annealing technique to the channel allocation problem. The objective function for this approach is defined as the total signal-to-interference radio (SIR) experienced by each link. To maintain network connectivity, the proposed approach limits the set of assigned channels for each radio. Experimental results show that, compared with traditional heuristic-based and game-theoretic approaches, the proposed simulated annealing algorithm results in more operative links.
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Hong, Jingxiang, Jose Rodriguez-Pineiro i Xuefeng Yin. "FDD Channel Inference Methods With Experimental Performance Evaluation". IEEE Access 8 (2020): 10491–502. http://dx.doi.org/10.1109/access.2020.2965290.
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Boutalline, Mohammed, Belaid Bouikhalene i Said Safi. "Channel Identification and Equalization based on Kernel Methods for Downlink Multicarrier-CDMA Systems". Journal of Electronic Commerce in Organizations 13, nr 2 (kwiecień 2015): 14–29. http://dx.doi.org/10.4018/jeco.2015040102.
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In this paper the authors are focused on channel identification and equalization for Multi-Carrier Code Division Multiple Access (MC-CDMA) system. For this, they identify the impulse response of two practical selective frequency fading channels called Broadband Radio Access Network (BRAN A and BRAN B) normalized by the European Telecommunications Standards Institute (ETSI). To identify the channel parameters, they have the positive definite kernels to build on algorithm. The simulations show that the presented method confirms the good performance for different SNR values. In part of equalization, the authors use the Zero Forcing (ZF) and Minimum Mean Square Error (MMSE) equalizers.
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Khan, Zaheer, i Janne Lehtomäki. "Adaptive and Autonomous Channel Access Methods for Distributed Cognitive Radios". Wireless Personal Communications 81, nr 2 (7.11.2014): 861–80. http://dx.doi.org/10.1007/s11277-014-2161-9.
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Khan, Zaheer, Janne Lehtomaki, Simon Scott, Zhu Han, Marwan Krunz i Alan Marshall. "Distributed and Coordinated Spectrum Access Methods for Heterogeneous Channel Bonding". IEEE Transactions on Cognitive Communications and Networking 3, nr 3 (wrzesień 2017): 267–81. http://dx.doi.org/10.1109/tccn.2017.2709753.
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Farhan, Ikhlas Mahmoud, Dhafer R. Zaghar i Hadeel Nasrat Abdullah. "Enhancement of code division multiple access system performance using raptor codes". Indonesian Journal of Electrical Engineering and Computer Science 26, nr 3 (1.06.2022): 1460. http://dx.doi.org/10.11591/ijeecs.v26.i3.pp1460-1468.
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Some kinds of communication systems work in very low signal-to-noise (LSNR) environments. For these systems to function reliably, <span>specific techniques and methodologies have to be used to mitigate the degrading effects of the channel. The channel coding method is the key element in most LSNR communication systems, but emphasizing the code division multiple access (CDMA) is a new transmission technique in these channels. To enhance the CDMA scheme's system capacity and reach unprecedented ranges of LSNR values in wireless sensor network. This paper suggests combining CDMA with certain types of channel coding algorithms, such as the raptor codes. The raptor channel encoding technique has improved the CDMA system's performance when using binary phase-shift keying (BPSK) modulation in additive white gaussian noise (AWGN) channels. It has achieved a low bit error rate in range of 10-7 at Eb/No value of (-3) dB and about 10-6 at shannon's limit. The Raptor-coded CDMA scheme works well for channel signal to noise ration (SNR) values of greater than -9 dB, showing an improvement of about 7 dB compared with turbo/convolutional channel coding methods used with the CDMA system bit error rate (BER) and throughput. On the other hand, it has been shown that the convolutional encoder presents the weakest performance compared to both the turbo and raptor codes.</span>
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Gizzini, Abdul Karim, i Marwa Chafii. "Low Complex Methods for Robust Channel Estimation in Doubly Dispersive Environments". IEEE Access 10 (2022): 34321–39. http://dx.doi.org/10.1109/access.2022.3162928.
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Zidane, Mohammed, Said Safi, Mohamed Sabri i Ahmed Boumezzough. "Bit Error Rate Analysis of MC-CDMA Systems with Channel Identification Using Higher Order Cumulants". Indonesian Journal of Electrical Engineering and Computer Science 1, nr 1 (1.01.2016): 138. http://dx.doi.org/10.11591/ijeecs.v1.i1.pp138-152.
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The aim of this paper is to contribute to study the problems of the blind identification and equalization using Higher Order Cumulants (HOC) in downlink Multi-Carrier Code Division Multiple Access (MC-CDMA) systems. For this problem, two blind algorithms based on HOC for Broadband Radio Access Network (BRAN) channel are proposed. In the one hand, to assess the performance of these approaches to identify the parameters of non minimum phase channels, we have considered two theoretical channels, and one practical frequency selective fading channel called BRAN C, driven by non gaussian signal. In the other hand, we use the Minimum Mean Square Error (MMSE) equalizer technique after the channel identification to correct the channel distortion. Theoretical analysis and numerical simulation results, in noisy environment and for different signal to noise ratio (SNR), are presented to illustrate the performance of the proposed methods.
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Abbass, Waseem, Riaz Hussain, Jaroslav Frnda, Nasim Abbas, Muhammad Awais Javed i Shahzad A. Malik. "Resource Allocation in Spectrum Access System Using Multi-Objective Optimization Methods". Sensors 22, nr 4 (9.02.2022): 1318. http://dx.doi.org/10.3390/s22041318.
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The paradigm of dynamic shared access aims to provide flexible spectrum usage. Recently, Federal Communications Commission (FCC) has proposed a new dynamic spectrum management framework for the sharing of a 3.5 GHz (3550–3700 MHz) federal band, called a citizen broadband radio service (CBRS) band, which is governed by spectrum access system (SAS). It is the responsibility of SAS to manage the set of CBRS-SAS users. The set of users are classified in three tiers: incumbent access (IA) users, primary access license (PAL) users and the general authorized access (GAA) users. In this article, dynamic channel assignment algorithm for PAL and GAA users is designed with the goal of maximizing the transmission rate and minimizing the total cost of GAA users accessing PAL reserved channels. We proposed a new mathematical model based on multi-objective optimization for the selection of PAL operators and idle PAL reserved channels allocation to GAA users considering the diversity of PAL reserved channels’ attributes and the diversification of GAA users’ business needs. The proposed model is estimated and validated on various performance metrics through extensive simulations and compared with existing algorithms such as Hungarian algorithm, auction algorithm and Gale–Shapley algorithm. The proposed model results indicate that overall transmission rate, net cost and data-rate per unit cost remain the same in comparison to the classical Hungarian method and auction algorithm. However, the improved model solves the resource allocation problem approximately up to four times faster with better load management, which validates the efficiency of our model.
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Chan, Chiu Chun, Bassel Al Homssi i Akram Al-Hourani. "Performance Evaluation of Random Access Methods for IoT-over-Satellite". Remote Sensing 14, nr 17 (27.08.2022): 4232. http://dx.doi.org/10.3390/rs14174232.
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Low Earth orbit (LEO) satellite constellations are currently being explored to provide global and seamless coverage for IoT-over-Satellite applications. Random access techniques require low transmission overhead providing a compatible route for IoT-over-Satellite applications, however, coming at the expense of the offered quality-of-service. In this paper, we develop a realistic uplink performance framework that incorporates many practical parameters such as the satellite availability, packet collision and interference, Doppler shift, and impairments experienced in a typical Satellite-to-Ground channel. The framework is capable of assessing multiple key performance indicators of the overall IoT-over-Satellite random access system. The performance is presented in terms of the bit error rate, packet error rate, and the energy wasted per IoT device. To emulate a realistic IoT-over-Satellite network, LoRa modulated traffic is first generated and injected into the Satellite-to-Ground channel. The results indicate high resistance to Doppler shifts even without any Doppler correction and provide some resistance to highly congested environments.
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Borodin, Vyacheslav V., Valentin E. Kolesnichenko i Vyacheslav A. Shevtsov. "Analysis of the Efficiency of Various Receipting Multiple Access Methods with Acknowledgement in IoT Networks". Inventions 8, nr 4 (18.08.2023): 105. http://dx.doi.org/10.3390/inventions8040105.
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An Internet of things (IoT) network is a distributed set of “smart” sensors, interconnected via a radio channel. The basic method of accessing the radio channels for these networks is Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA), in which access is carried out on the basis of contention, and confirmation of the correct reception of the packet is achieved using a receipt. If the sizes of information packets are small and comparable to the sizes of receipts, then the transmission of receipts requires a significant bandwidth of the channel, which reduces the efficiency of the network. This problem exists not only for IoT networks but also for monitoring systems, operational management of fast processes, telemetry, short messaging and many other applications. Therefore, an urgent task is to develop effective methods of multiple random access in the transmission of short information packets, the size of which is comparable to the size of receipts. To solve this problem, the authors proposed modifications of CSMA/CA random access in which, when packet collisions are detected, a diagnostic message (DM) is generated and transmitted in the broadcast mode. Based on simulation modeling, it is shown that in a wide range of network loads, the proposed random access options provide an increase in network capacity (the number of connected subscribers) of 1.5–2 times compared to the basic CSMA/CA access method when the size of the information packet is an order of magnitude larger than the size of receipts. The variant of access without acknowledgment is also considered, in which, as shown by the simulation results, at sufficiently large loads, the network can go into an unstable state.
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Findlay, N., i GP Findlay. "Single Ion Channel Current Data from the Plasmalemma of Cytoplasmic Fragments of the Green Alga, Hydrodictyon africanum". Functional Plant Biology 22, nr 4 (1995): 571. http://dx.doi.org/10.1071/pp9950571.
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To measure, by patch clamping, electric current through ion channels in the plasmalemma of plant cells, access to the membrane surface is required. In higher plants, this access is gained by the preparation of protoplasts by enzymic methods. In plants such as the freshwater alga Hydrodictyon africanum, which have large cells, the preparation of protoplasts by enzymic methods is not possible. In this paper we describe a non-enzymic method for gaining access to the plasmalemma of Hydrodictyon. Our initial attempts to gain access to the plasmalemma of these cells by first plasmolysing the cells, and then cutting a window in the wall, so exposing the plasmalemma, were not successful. It was possible, however, after drying the cells in air, to cut them open and obtain fragments of the cytoplasm which maintain their original curvature. Standard patch clamping methods were then used to measure currents through single ion channels in the membrane, presumed to be the plasmalemma, bounding the outer surface of the fragments, although the success rate was low. Two types of channels were observed: (a) a multistate channel whose ion specificity was not established, and which in attached patches behaved as an outward current rectifier, and in a detached patch, as both inward and outward rectifier; and (b) a Cl- channel.
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Lai, Lianyou, Zhongzhe Song i Weijian Xu. "A Novel Framed Slotted Aloha Medium Access Control Protocol Based on Capture Effect in Vehicular Ad Hoc Networks". Sensors 24, nr 3 (3.02.2024): 992. http://dx.doi.org/10.3390/s24030992.
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The capture effect is a frequently observed phenomenon in vehicular ad hoc networks (VANETs) communication. When conflicts arise during time slot access, failure to access does not necessarily occur; instead, successful access may still be achieved. The capture effect can enhance the likelihood of multiple access and improve communication efficiency. The security of VANETs communication is undoubtedly the primary concern. One crucial approach to enhance security involves the design of an efficient and reliable medium access control (MAC) protocol. Taking into account both aspects, we propose a novel framed slotted Aloha (FSA) MAC protocol model. Firstly, we derive the closed-form expression for the capture probability in the Rician fading channel in this paper. Subsequently, we analyze how the number of vehicles and time slots influence the success probability of vehicle access channels as well as examine the impact of the capture effect on this success probability. Then, under constraints regarding vehicle access channel success probability, we derive optimal values for slot numbers, access times, and transmission power while proposing a comprehensive implementation method to ensure high access channel success probabilities. We verify both theoretical derivations and proposed methods through simulation experiments.
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Tomović, Slavica, i Igor Radusinović. "Dynamic spectrum access with deep Q-learning in densely occupied and partially observable environments". Telfor Journal 13, nr 1 (2021): 1–6. http://dx.doi.org/10.5937/telfor2101001t.
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In this paper, we propose a new Dynamic Spectrum Access (DSA) method for multi-channel wireless networks. We assume that DSA nodes do not have prior knowledge of the system dynamics, and have only partial observability of the channels. Thus, the problem is formulated as a Partially Observable Markov Decision Process (POMDP) with exponential time complexity. We have developed a novel Deep Reinforcement Learning (DRL) based DSA method which combines a double deep Q-learning architecture with a recurrent neural network and takes advantage of a prioritized experience buffer. The simulation analysis shows that the proposed method accurately predicts a channel state based on the fixed-length history of partial observations. Compared with other DRL methods for DSA, the proposed solution can find a near-optimal policy in a smaller number of iterations and suits a wider range of communication environments, including dynamic ones, where channel occupancy pattern changes over time. The performance improvement increases with the number of channels and with a channel state transition uncertainty. To boost the performance of the algorithm in densely occupied environments, multiple DRL exploration strategies are examined and evaluation results are presented in the paper.
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Carrera, Diego Fernando, Cesar Vargas-Rosales, Noe M. Yungaicela-Naula i Leyre Azpilicueta. "Comparative Study of Artificial Neural Network Based Channel Equalization Methods for mmWave Communications". IEEE Access 9 (2021): 41678–87. http://dx.doi.org/10.1109/access.2021.3065337.
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Sun, Hui, i Han Han. "Analysis of Spectrum Selection Methods Based on Platform-Qualnet in Cognitive Radio Networks". International Journal of Online and Biomedical Engineering (iJOE) 15, nr 03 (14.02.2019): 124. http://dx.doi.org/10.3991/ijoe.v15i03.9517.
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Dynamic spectrum Access （DSA）is used to make use of the spectrum in wireless network. In most situations, control channel is a common approach to negotiation between secondary users. But, based on this feature, the attacker can destroy the communication network only influence the control center. So, in this paper, two methods without control channel are simulated in Qualent platform. The results prove that those methods are available, and the Receiver-directed channel selection is more match to the regular control channel standards in throughput.
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N. Thakre, Prasheel, Sanjay Pokle, Radhika Deshpande, Samruddhi Paraskar, Shashwat Sinha i Yash Lalwani. "Performance analysis of NOMA in Rayleigh and Nakagami Fading channel". 3C TIC: Cuadernos de desarrollo aplicados a las TIC 11, nr 2 (29.12.2022): 183–93. http://dx.doi.org/10.17993/3ctic.2022.112.183-193.
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Cellular connectivity is expanding rapidly in the modern world. The multiple access strategy is one of the highly used methods for allocating the range of users in cellular network. Spectrum allocation is a crucial element to take into account since cellular communication is becoming more and more popular. NOMA is a channel access mechanism used in 5G mobile communication. It is also known as non-orthogonal multiple access. NOMA is a potential strategy for enhancing spectral efficiency and sum rate. Using the NOMA method, we evaluated the BER versus transmitted power of two users in rayleigh and nakagami fading channels. In this NOMA setup, a single antenna is shared by two users. Two users can accept the same frequency using 5G NOMA technology, but at different power levels. The results of the MATLAB simulation show that the two user NOMA in the Nakagami channel performs better than the Rayleigh channel in terms of Bit Error Rate vs. Transmitted Power.
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Yang, Xu, Athman Bouguettaya i Xumin Liu. "Semantic-Based Access to Composite Mobile Services". International Journal of Web Services Research 8, nr 3 (lipiec 2011): 70–100. http://dx.doi.org/10.4018/jwsr.2011070104.
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In this paper, the authors propose novel access methods and a multi-channel organization for mobile users to effectively access composite M-services in wireless broadcast networks. The authors first propose a broadcast-based infrastructure to address the challenges of efficient usages of composite M-services. They then define a few semantics for accessing broadcast based M-services and discuss the strategies of efficiently accessing M-services based on the semantics. The authors also propose several channel organization that are suitable for the broadcast-based M-service structure and provide analytical models for them. They conduct a comprehensive experimental study on the proposed access methods.
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Musaev, Alexey, i Sergey Zinkin. "Theoretical analysis of interference in satellite communication systems when using multistation access with code division of channels". Informatization and communication 4 (listopad 2020): 7–12. http://dx.doi.org/10.34219/2078-8320-2020-11-4-7-12.
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Abstract. To ensure the most effective use of the limited radio resource of the repeater, various methods of multistation access of earth stations to the repeater are developed and applied, based on one or another method of channel separation. The article presents a theoretical analysis of the occurrence of mutual and combination interference in satellite communication systems when using multi -station access with code separation of channels. Recommendations for further experimental studies are proposed.
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Xu, Yangzhou, Jia Lou, Tiantian Wang, Junxiao Shi, Tao Zhang, Agyemang Paul i Zhefu Wu. "Multiple Access for Heterogeneous Wireless Networks with Imperfect Channels Based on Deep Reinforcement Learning". Electronics 12, nr 23 (30.11.2023): 4845. http://dx.doi.org/10.3390/electronics12234845.
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In heterogeneous wireless networks, when multiple nodes need to share the same wireless channel, they face the issue of multiple access, which necessitates a Medium Access Control (MAC) protocol to coordinate the data transmission of multiple nodes on the shared communication channel. This paper presents Proximal Policy Optimization-based Multiple Access (PPOMA), a novel multiple access protocol for heterogeneous wireless networks based on the Proximal Policy Optimization (PPO) algorithm from deep reinforcement learning (DRL). Specifically, we explore a network scenario where multiple nodes employ different MAC protocols to access an Access Point (AP). The novel PPOMA approach, leveraging deep reinforcement learning, adapts dynamically to coexist with other nodes. Without prior knowledge, it learns an optimal channel access strategy, aiming to maximize overall network throughput. We conduct simulation analyses using PPOMA in two scenarios: perfect channel and imperfect channel. Experimental results demonstrate that our proposed PPOMA continuously learns and refines its channel access strategy, achieving an optimal performance level in both perfect and imperfect channel scenarios. Even when faced with suboptimal channel conditions, PPOMA outperforms alternative methods by achieving higher overall network throughput and faster convergence rates. In a perfect channel scenario, PPOMA’s advantage over other algorithms is primarily evident in its convergence speed, reaching convergence on average 500 iterations faster. In an imperfect channel scenario, PPOMA’s advantage is mainly reflected in its higher overall network throughput, with an approximate increase of 0.04.
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Tonin, Jean Marcel Faria, i Taufik Abrao. "Linear detectors and precoding methods for massive MIMO". Semina: Ciências Exatas e Tecnológicas 42, nr 2 (2.12.2021): 209. http://dx.doi.org/10.5433/1679-0375.2021v42n2p209.
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Detection in multiple-input-multiple-output (MIMO) wireless communication systems is a crucial procedure in receivers since the multiple access transmission schemes generate interference due to the simultaneous transmission along with the several antennas, unlike single-input-single-output (SISO) transmission schemes. Precoding is a technique in MIMO systems used to mitigate the effects of the channel over the received signal. Hence, it is possible to adjust continuously the transmitted information to reverse the effect of the wireless channel at the receiver side. In this work, linear sub-optimal detectors and precoders for massive MIMO (M-MIMO) systems are implemented, analyzed, and compared in terms of performance-complexity trade-off. It is also being considered numerical results in both channel scenarios: a) receiver and transmitter have perfect channel state information (CSI); b) complex channel coefficients are estimated with different levels of inaccuracy. Monte-Carlo simulations (MCS) reveal that linear zero-forcing (ZF) and minimum mean squared error (MMSE) massive MIMO detectors result in a certain robustness against multi-user interference when operating under low and medium system loading, L = K/M, thanks to the favourable propagation phenomenon arising in massive MIMO systems.
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Zhu, Guohun, Fangrong Zong, Hua Zhang, Bizhong Wei i Feng Liu. "Cognitive Load During Multitasking Can Be Accurately Assessed Based on Single Channel Electroencephalography Using Graph Methods". IEEE Access 9 (2021): 33102–9. http://dx.doi.org/10.1109/access.2021.3058271.
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Zhang, Yan, Ammar Ghazal, Cheng-Xiang Wang, Hongrui Zhou, Weiming Duan i El-Hadi M. Aggoune. "Accuracy-Complexity Tradeoff Analysis and Complexity Reduction Methods for Non-Stationary IMT-A MIMO Channel Models". IEEE Access 7 (2019): 178047–62. http://dx.doi.org/10.1109/access.2019.2957820.
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Li, Guoyan, Tian Li, Xinwei Yue, Tianwei Hou i Bin Dai. "High Reliable Uplink Transmission Methods in GEO–LEO Heterogeneous Satellite Network". Applied Sciences 13, nr 15 (26.07.2023): 8611. http://dx.doi.org/10.3390/app13158611.
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As a significant component of non-terrestrial networks, satellite communication has gradually evolved into a heterogeneous topology where the network nodes are classified as low Earth orbit (LEO) and geostationary Earth orbit (GEO) nodes. Considering the advantage of low transmission delay of LEO satellites in a heterogeneous network, ground users are arranged to access LEO satellites in the first priority. By fully understanding the equivalent channel gain difference in the beam-edge and beam-center users, we develop non-orthogonal multiple access (NOMA) in an LEO network where different users are allocated in the same resource block. As a complementary strategy, the beam-edge user has the ability to connect the GEO satellite if the LEO links are not available. That is, the two users are served cooperatively by LEO and GEO satellites in an orthogonal manner. In this paper, we provide deep insights for the uplink transmission performance of NOMA and cooperative orthogonal multiple access methods. As a general metric, the analytical expressions of outage probability are derived and the diversity orders are also provided. The simulation results show that NOMA is capable of providing remarkable performance in low signal-to-noise ratio regions and is more promising when the channels are assumed to be ordered.
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Wang, Xiaoyan, Yuto Teraki, Masahiro Umehira, Hao Zhou i Yusheng Ji. "A Usage Aware Dynamic Spectrum Access Scheme for Interweave Cognitive Radio Network by Exploiting Deep Reinforcement Learning". Sensors 22, nr 18 (14.09.2022): 6949. http://dx.doi.org/10.3390/s22186949.
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Future-generation wireless networks should accommodate surging growth in mobile data traffic and support an increasingly high density of wireless devices. Consequently, as the demand for spectrum continues to skyrocket, a severe shortage of spectrum resources for wireless networks will reach unprecedented levels of challenge in the near future. To deal with the emerging spectrum-shortage problem, dynamic spectrum access techniques have attracted a great deal of attention in both academia and industry. By exploiting the cognitive radio techniques, secondary users (SUs) are capable of accessing the underutilized spectrum holes of the primary users (PUs) to increase the whole system’s spectral efficiency with minimum interference violations. In this paper, we mathematically formulate the spectrum access problem for interweave cognitive radio networks, and propose a usage-aware deep reinforcement learning based scheme to solve it, which exploits the historical channel usage data to learn the time correlation and channel correlation of the PU channels. We evaluated the performance of the proposed approach by extensive simulations in both uncorrelated and correlated PU channel usage cases. The evaluation results validate the superiority of the proposed scheme in terms of channel access success probability and SU-PU interference probability, by comparing it with ideal results and existing methods.
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Du, Chenglin, Ran Ye, Xiaolong Cai, Xiangyang Duan, Haijun Liu, Yu Zhang, Gang Qiu i Minhan Mi. "A review on GaN HEMTs: nonlinear mechanisms and improvement methods". Journal of Semiconductors 44, nr 12 (1.12.2023): 121801. http://dx.doi.org/10.1088/1674-4926/44/12/121801.
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Abstract The GaN HEMT is a potential candidate for RF applications due to the high frequency and large power handling capability. To ensure the quality of the communication signal, linearity is a key parameter during the system design. However, the GaN HEMT usually suffers from the nonlinearity problems induced by the nonlinear parasitic capacitance, transconductance, channel transconductance etc. Among them, the transconductance reduction is the main contributor for the nonlinearity and is mostly attributed to the scattering effect, the increasing resistance of access region, the self-heating effect and the trapping effects. Based on the mechanisms, device-level improvement methods of transconductance including the trapping suppression, the nanowire channel, the graded channel, the double channel, the transconductance compensation and the new material structures have been proposed recently. The features of each method are reviewed and compared to provide an overview perspective on the linearity of the GaN HEMT at the device level.
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Rogozhnikov, Eugeniy, Yakov Kryukov, Dmitriy Pokamestov, Edgar Dmitriev i Renat Abenov. "Analysis of factors affecting the operation of the communication system with nonorthogonal multiple access". ITM Web of Conferences 30 (2019): 04003. http://dx.doi.org/10.1051/itmconf/20193004003.
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NOMA is a group of non-orthogonal multiple access methods [1]. In this article, we talk about the Power Domain (Division) NOMA method. It is a non-orthogonal multiple access method with channel separation by power [2]. NOMA compaction uses controlled inter-channel interference, which is removed in the receiver when channel separation using special algorithms. PD-NOMA can be used in conjunction with various types of modulation, including OFDM.
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Lai, Junyu, James C. F. Li, Alireza Abdollahpouri, Jianhua Zhang i Ming Lei. "A Fairness-Based Access Control Scheme to Optimize IPTV Fast Channel Changing". Mathematical Problems in Engineering 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/207402.
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IPTV services are typically featured with a longer channel changing delay compared to the conventional TV systems. The major contributor to this lies in the time spent on intraframe (I-frame) acquisition during channel changing. Currently, most widely adopted fast channel changing (FCC) methods rely on promptly transmitting to the client (conducting the channel changing) a retained I-frame of the targeted channel as a separate unicasting stream. However, this I-frame acceleration mechanism has an inherent scalability problem due to the explosions of channel changing requests during commercial breaks. In this paper, we propose a fairness-based admission control (FAC) scheme for the original I-frame acceleration mechanism to enhance its scalability by decreasing the bandwidth demands. Based on the channel changing history of every client, the FAC scheme can intelligently decide whether or not to conduct the I-frame acceleration for each channel change request. Comprehensive simulation experiments demonstrate the potential of our proposed FAC scheme to effectively optimize the scalability of the I-frame acceleration mechanism, particularly in commercial breaks. Meanwhile, the FAC scheme only slightly increases the average channel changing delay by temporarily disabling FCC (i.e., I-frame acceleration) for the clients who are addicted to frequent channel zapping.
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Narasu, Krishnamoorthy Raghavan, Immanuel Rajkumar, Jerry Alexander i Marshiana Devaerakkam. "Impact of Equalizer step size in Underwater Acoustic Communication Channel". International Journal of Computer Network and Information Security 13, nr 1 (8.02.2021): 29–38. http://dx.doi.org/10.5815/ijcnis.2021.01.03.
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The Underwater Acoustic Channel (UAC) is a time variant channel and its multipath effects create ISI. This is one of the most important obstacles in the UAC channel which reduces the transmission rate. To remove this obstacle, a proper filter has to be designed in the receiver section. In this article, optimal step size for equalizer is computed and compared the results with the known techniques namely Decision Feedback Equalizer with interleave division multiple access (DFE IDMA) and Cyclic Prefix - Orthogonal Frequency Division Multiplexing (CP-OFDM) Equalizer. Channels are modeled using ray tracing methods. The various factors considered are ambient noise, attenuation loss, bottom and surface loss. The overall path loss for channels is computed by summing up the attenuation loss, surface and bottom loss. Simulation results evident that for short range UAC channel, the BER in the order of 10-2 is achieved using proposed methodology with least Eb/No compared to standard DFE method.
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Pokamestov, Dmitriy, Yakov Kryukov, Eugeniy Rogozhnikov, Georgiy Shalin, Artem Shinkevich i Serafim Novichkov. "Adaptation of Signal with NOMA and Polar Codes to the Rayleigh Channel". Symmetry 14, nr 10 (10.10.2022): 2103. http://dx.doi.org/10.3390/sym14102103.
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Polar codes are one of the most effective methods of error correction coding. Currently, these codes are used in 5G communication systems and are the main candidate for 6G. Symmetry plays an important role in coding and decoding algorithms for polar codes. Modulation and multiple access methods are the basis for a physical layer along with error correction codes. Non-Orthogonal Multiple Access (NOMA) methods are a promising technology for future telecommunication systems. They allow the increase of both spectral efficiency and the quantity of subscribers of a communication system. In this paper, we consider a communication system with polar codes, traditional orthogonal multiple access (OMA), and NOMA. The channel with multipath propagation, which can be defined by the Rayleigh channel model, is especially difficult to transmit. We propose a method for adapting signals with polar codes to a channel state based on the analysis of channel matrix and permutation of logical subchannels. The results obtained demonstrate efficiency compared to classical solutions and do not really increase the computational complexity of signal processing and decoding.
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Бабурин, Александр Вильямович, Лариса Александровна Глущенко, Борис Николаевич Добряков, Григорий Александрович Остапенко i Андрей Петрович Преображенский. "PROTECTION AGAINST UNAUTHORIZED ACCESS TO INFORMATION CIRCULATING IN WIRELESS INFRARED CHANNELS OF DATA TRANSMISSION". ИНФОРМАЦИЯ И БЕЗОПАСНОСТЬ, nr 4(-) (25.12.2020): 511–18. http://dx.doi.org/10.36622/vstu.2020.23.4.003.
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Цель исследования состоит в разработке методов защиты от несанкционированного доступа информации, циркулирующей в беспроводных ИК-каналах передачи данных. Показаны возможные способы несанкционированного доступа к каналу передачи данных от ИК-клавиатуры к компьютеру. Основной способ несанкционированного доступа к ИК-каналу передачи данных - это регистрация диффузно-отраженного от элементов интерьера излучения. Проведены теоретические оценки, подтверждающие возможность получения информации, циркулирующей в беспроводных ИК-каналах передачи данных при несанкционированном доступе. Рассмотрен типичный случай распространения излучения в помещении при использовании ИК-канала передачи данных при несанкционированном доступе. Неуполномоченный наблюдатель может регистрировать через оконный проем диффузно-отраженное излучение, используя специальную оптико-электронную систему. Для расчетов были приняты типовые фотометрические характеристики интерьера помещения и предельно достижимые на современном уровне техники характеристики фотоприемных устройств. Размер диаметра входного зрачка оптической системы принят не слишком большим из того соображения, что он не должен привлекать внимание (служить демаскирующим признаком). Предложен метод защиты информации, циркулирующей в беспроводных ИК-каналах передачи данных, основанный на формировании засветочных помех. Приведены схемы формирования засветочных помех. Для помехи может быть использовано диффузно-отраженной излучение или специально сформированное излучение, направленное на оконный проем помещения. The purpose of the research is to develop methods of protection against unauthorized access to information circulating in wireless infrared channels of data transmission. Possible ways of unauthorized access to the data transmission channel from the IR keyboard to the computer are shown. The main method of unauthorized access to the IR data transmission channel is the registration of radiation diffusely reflected from interior elements. Theoretical estimates have been carried out confirming the possibility of obtaining information circulating in wireless infrared channels of data transmission under unauthorized access. A typical case of propagation of radiation in room when using an IR data transmission channel with unauthorized access to information is considerd. An unauthorized observer can register diffusely reflected radiation through a window opening using a special optoelectronic system. For the calculations, the standard photometric characteristics of the interior of the room and the maximum achievable at the modern level of technology characteristics of photodetectors were taken. The size of the diameter of the entrance pupil of the optical system is taken not too large for the reason that optoelectronic system should not attract attention (serve as a unmasking feature). The method for protecting of information ciculating in optical wireless channels of data transmission, based on the formation of optical intentional noise, is proposed. It provides a brief overview of methods for generating pseudorandom sequences, wich can serv as a basis for the formation of an illumination noise channel. For optical intentional noise can be used diffusely reflected radiation or specially formed radiation, directed at the window opening of the room.
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Zhu, Feng Xia, Zai Yu Zhang i Ma Jia Wu. "Broadband Self-Organizing Network Channel Allocation". Applied Mechanics and Materials 631-632 (wrzesień 2014): 910–13. http://dx.doi.org/10.4028/www.scientific.net/amm.631-632.910.
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This paper discussed the current variety of effective multi-channel self-organizing network channel allocation techniques and proposed a combination of two access methods CSMA and TDMA. By using broadband wireless self-organizing network channel and OPNET simulation tools,the methods can build self-organizing network simulation scenarios that proposed network protocols performance analysis. This self-organizing network channel allocation can effectively transmit information and avoid the conflict of different communication node distribution of the corresponding channel.
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Matveev, Nikolay, i Andrey Turlikov. "Review of random multiple access methods for massive machine type communication". Information and Control Systems, nr 6 (16.01.2020): 54–67. http://dx.doi.org/10.31799/1684-8853-2019-6-54-67.
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Introduction: Intensive research is currently underway in the field of data transmission systems for the Internet of Things in relation to various scenarios of Massive Machine Type Communication. The presence of a large number of devices in such systems necessitates the use the methods of random multiple access to a common communication channel. It is proposed in some works to increase the channel utilization efficiency by the use of error correction coding methods for conflict resolution (Coded Random Access). The vast variety of options for using such communication systems has made it impossible to compare algorithms implementing this approach under the same conditions. This is a problem that restrains the development of both the theory and practice of using error correction code methods for conflict resolution. Purpose: Developing a unified approach to the description of random multiple access algorithms; performing, on the base on this approach, a review and comparative analysis of algorithms in which error correction code methods are used for conflict resolution. Results: A model of a random multiple access system is formulated in the form of a set of assumptions that reflect both the features of various scenarios of Massive Machine Type Communication and the main features of random multiple access algorithms, including Coded Random Access approaches. The system models are classified by the following features: 1) a finite or infinite number of subscribers; 2) stable, unstable or metastable systems; 3) systems with retransmissions or without them; 4) systems with losses or without them. For a lossy system, the main characteristics are Throughput (the proportion of successfully delivered messages) and Packet Loss Rate (probability of a message loss). For a lossless system, the basic characteristics are the algorithm speed and the average delay. A systematic review and comparative analysis of Coded Random Access algorithms have been carried out. The result of the comparative analysis is presented in a visual tabular form. Practical relevance: The proposed model of a random multiple access system can be used as a methodological basis for research and development of random multiple access algorithms for both existing and new scenarios of Massive Machine Type Communication. The systematic results of the review allow us to identify the promising areas of research in the field of data transmission systems for the Internet of Things.
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Rahayu, Heni Sulistyawati Purwaning, Mardiana Dewi i Muhammad Abid. "Analysis of Marketing Margins and Farmers’ Shares on Corn in Sigi Regency, Central Sulawesi, Indonesia". Caraka Tani: Journal of Sustainable Agriculture 36, nr 2 (31.08.2021): 355. http://dx.doi.org/10.20961/carakatani.v36i2.49409.
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<p>An increase in corn productivity is not always followed by an increase in farmer income and welfare. The sustainability of farms must be supported by its economic viability including the marketing aspect. This study aimed to analyze the marketing of corn in Sigi Regency, Central Sulawesi Province. This research applied qualitative and quantitative methods. Marketing channel and marketing margin were analyzed descriptively, while farmer share was analyzed quantitatively using variance analysis (ANOVA). The results have shown three types of corn marketing channels, namely: 1) channel I, consisting of farmers-consumers, 2) channel II, covering farmers-collectors, traders-retailers and traders-consumers and 3) channel III, including farmers-collectors and traders- feed industries. Channel II has the highest marketing margin, followed by channel III and I, respectively. The intermediaries determine marketing costs that affect marketing margin and farmers’ shares. Channel I has the highest farmers’ shares, followed by channel III and channel II, respectively. The results of the significant difference test have revealed a difference in farmers’ shares in the marketing channels; and hence, the choice of marketing channel significantly determines the farmers’ shares. Therefore, farmers should shorten the marketing chain and strengthen their bargaining position by activating groups. Meanwhile, the government can play an active role so that farmers can have an access to strengthening capital and marketing.</p>
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Hussain, Syed Aamer, Norulhusna Ahmad, Ibraheem Shayea, Hazilah Mad Kaidi, Liza Abdul Latiff, Norliza Mohamed i Suriani Mohd Sam. "A review of codebook design methods for sparse code multiple access". Indonesian Journal of Electrical Engineering and Computer Science 22, nr 2 (1.05.2021): 927. http://dx.doi.org/10.11591/ijeecs.v22.i2.pp927-935.
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<span lang="EN-GB">The progressions in telecommunication beyond the 5<sup>th</sup> generation have created a need to improve research drifts. The current 5G study has an important focus on non-orthogonal multiple access (NOMA) technology. sparse code multiple access (SCMA) is a promising technique within NOMA, enhancing the multi-user handling capability of next-generation communication. In the SCMA sphere, codebook designing and optimisation are essential research matters. This study conversed with different codebook design practises existing in the literature, analysing them for numerous parameters, including bit error rate (BER), an optimisation technique, and channel settings. From the analysis, the paper presents the efficiency of different approaches. The article also discusses the prospects and challenges of SCMA optimisation in practical implementation in various domains.</span>
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Anwar, Huda, Ahmed A. Alabdel Abass i Rawaa Kadhim. "Performance of Relaying System with NOMA over Symmetric a-Stable Noise Channels". Indian Journal Of Science And Technology 17, nr 17 (14.04.2024): 1745–54. http://dx.doi.org/10.17485/ijst/v17i17.432.
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Objectives: This paper investigates the performance of a candidate 5G transmission system technique that is Non-Orthogonal Multiple Access (NOMA) over α-stable channels. This type of channel gets more attention in the research community because of its ability to model new IoT scenarios. However, there is a research gap in applying this type of channel to different wireless communications scenarios. In this work, we envision a scenario where users employ NOMA communications in the presence of an obstacle. As our mathematical analysis and simulation results show, there is a significant difference in performance when considering α-stable channels. Methods: To characterize the performance of the proposed noise channel, performance metrics such as outage probability and achievable rate are discussed. More particularly, we derive expressions for both outage probability and achievable rate for three NOMA users, considering the near user as a relay. In this paper, we consider additive symmetric α-stable noise channels with alpha α ∈ (1, 2). We present expressions for achievable rate and outage probability for each user (near, middle, and far) and investigate its behavior for different values of alpha (α). Findings: Based on the simulation results, it is shown that the high achievable rate observed for low alpha values while reduced as alpha is increased. Also, due to the influence of alpha, the outage probability is highly affected by α for small rate thresholds (Ro). In an envisioned scenario of three users with only one user forwarding the transmission to the other two, our results show that the near and middle users’ outage probability decreases as alpha α increases. Novelty: Despite this extensive study of the NOMA on individual channels, transmission under α-stable channel is not considered to the best of the authors’ knowledge. Keywords: NOMA, relaying, Cooperative Non-Orthogonal Multiple Access, Symmetric α-Stable Noise Channels, Achievable rate
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Pokamestov, Dmitriy, Yakov Kryukov, Eugeniy Rogozhnikov, Islam Kanatbekuli i Edgar Dmitriyev. "SCMA-MIMO system with adaptation to the channel state". Journal of Physics: Conference Series 2134, nr 1 (1.12.2021): 012025. http://dx.doi.org/10.1088/1742-6596/2134/1/012025.
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Abstract Sparse code multiple access (SCMA) is one of the promising implementations of non-orthogonal multiple access (NOMA) methods. SCMA provides high spectral efficiency and a large number of network resources. We describe a communication system with SCMA, space-time block coding (STBC), multiple input multiple output (MIMO) technology, and orthogonal frequency division multiplexing (OFDM). The architecture of such systems, including algorithms of formation and processing of signals is considered. A method for adapting signals to the state of the spatial channel transmission based on information about the matrix of channel coefficients is proposed. The application of such adaptation allows to compensate the influence of the channel and to reduce the probability of bit errors. We consider the bit error rate (BER) performance of the communication system in different channel models and show the effectiveness of the proposed methods.
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van Dijk, Wout M., Jana R. Cox, Jasper R. F. W. Leuven, Jelmer Cleveringa, Marcel Taal, Matthew R. Hiatt, Willem Sonke, Kevin Verbeek, Bettina Speckmann i Maarten G. Kleinhans. "The vulnerability of tidal flats and multi-channel estuaries to dredging and disposal". Anthropocene Coasts 4, nr 1 (1.01.2021): 36–60. http://dx.doi.org/10.1139/anc-2020-0006.
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Shipping fairways in estuaries are continuously dredged to maintain access for large vessels to major ports. However, several estuaries worldwide show adverse side effects to dredging activities, in particular affecting morphology and ecologically valuable habitats. We used physical scale experiments, field assessments of the Western Scheldt estuary (the Netherlands), and morphodynamic model runs to analyse the effects of dredging and future stresses (climate and sediment management) on a multi-channel system and its ecologically valuable intertidal flats. All methods indicate that dredging and disposal strategies are unfavourable to long-term morphology because dredging creates and propagates the imbalance between shallow and deeper parts of the estuary, causing a loss of valuable connecting channels and fixation of the tidal flats and main channel positions, while countering adverse effects by disposal strategy has limited effectiveness. Changing the disposal strategy towards main channel scour disposal can be economically and ecologically beneficial for the preservation of the multi-channel system. Further channel deepening will accelerate the adverse side effects, whereas future sea-level rise may revive the multi-channel system.
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Min, Moonsik, Jae-Ik Kong i Tae-Kyoung Kim. "Non-Orthogonal Multiple Access with One-Bit Analog-to-Digital Converters Using Threshold Adaptation". Sensors 23, nr 13 (28.06.2023): 6004. http://dx.doi.org/10.3390/s23136004.
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In digital communication systems featuring high-resolution analog-to-digital converters (ADCs), the utilization of successive interference cancellation and detection can enhance the capacity of a Gaussian multiple access channel (MAC) by combining signals from multiple transmitters in a non-orthogonal manner. Conversely, in systems employing one-bit ADCs, it is exceedingly difficult to eliminate non-orthogonal interference using digital signal processing due to the considerable distortion present in the received signal when employing such ADCs. As a result, the Gaussian MAC does not yield significant capacity gains in such cases. To address this issue, we demonstrate that, under a given deterministic interference, the capacity of a one-bit-quantized channel becomes equivalent to the capacity without interference when an appropriate threshold value is chosen. This finding suggests the potential for indirect interference cancellation in the analog domain, facilitating the proposition of an efficient successive interference cancellation and detection scheme. We analyze the achievable rate of the proposed scheme by deriving the mutual information between the transmitted and received signals at each detection stage. The obtained results indicate that the sum rate of the proposed scheme generally outperforms conventional methods, with the achievable upper bound being twice as high as that of the conventional methods. Additionally, we have developed an optimal transmit power allocation algorithm to maximize the sum rate in fading channels.
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Mykhalevskiy, D. V. "TECHNICAL DIAGNOSIS OF WIRELESS CHANNELS OF 802.11 STANDARD". Proceedings of the O.S. Popov ОNAT 1, nr 2 (31.12.2020): 111–20. http://dx.doi.org/10.33243/2518-7139-2020-1-2-111-120.
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The main task when designing 802.11 wireless networks is to create access with the highest possible channel bandwidth for an individual subscriber. This problem is solved in two ways: calculation and test diagnostics of networks at the design stage; optimization of networks during operation based on technical diagnostics and monitoring. This paper investigates and clarifies the existing terminology for technical diagnostics and control for 802.11 wireless channels. As a result, it is established that radio monitoring is the first stage of technical diagnostics on the basis of which it is possible to obtain statistical characteristics about the change of channel parameters over time. The second stage includes models and methods of analysis and evaluation of channel parameters, considering the influence of various destabilizing factors with control operations. Based on the obtained terminology, a structural-consequential diagnostic model was proposed for the 802.11 wireless channel, which provides a formalized description of the object needed to solve the problems of diagnosis and control. The model uses the general structure of the channel and physical layer of the 802.11 standard and energy and information diagnostic parameters, which is valid for any wireless channel. The level of reliability of technical diagnostics of wireless channels is provided due to the built-in means of monitoring of subscriber devices, the number of input parameters and the observation period. In addition, an assessment of the suitability of the channel for traffic transmission is provided, which involves comparing the bit rate with the obtained technical diagnostic data. This is relevant in the current trends of improving the quality of modern infocommunication services, which significantly increases the bandwidth requirements of channels. The proposed model of technical diagnostics is a concept of methodology. It includes the use of: improved and new developed by the author's own methodological approaches to conducting research on wireless channels; acquired new knowledge about the operation of these channels under the influence of phenomena existing in the transmission medium; new models and methods for estimating energy and information parameters and the relationships between them; methods of evaluation and statistical processing of theoretical and empirical research.
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Assiimwe, Eva, i Yihenew Wondie Marye. "A Stochastic Confocal Elliptic-Cylinder Channel Model for 3D MIMO in Millimeter-Wave High-Speed Train Communication System". Electronics 11, nr 13 (22.06.2022): 1948. http://dx.doi.org/10.3390/electronics11131948.
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Massive MIMO technology is among the most promising solutions for achieving higher gain in 5G millimeter-wave (mmWave) channel models for high-speed train (HST) communication systems. Based on stochastic geometry methods, it is fundamental to accurately develop the associated MIMO channel model to access system performance. These MIMO channel models could be extended to massive MIMO with antenna arrays in more than one plane. In this paper, the proposed MIMO 3D geometry-based stochastic model (GBSM) is composed of the line of sight component (LOS), one sphere, and multiple confocal elliptic cylinders. By considering the proposed GBSM, the local channel statistical properties are derived and investigated. The impacts of the distance between the confocal points of the elliptic cylinder, mmWave frequencies of 28 GHz and 60 GHz, and non-stationarity on channel statistics are studied. Results show that the proposed 3D simulation model closely approximates the measured results in terms of stationary time. Consequently, findings show that the proposed 3D non-wide-sense stationary (WSS) model is better for describing mmWave HST channels in an open space environment.
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Wang, Ju, i Jonathan Liu. "Interference Minimization and Dynamic Sub-Carrier Allocation in Broadband Wireless Networks". International Journal of Wireless Networks and Broadband Technologies 3, nr 3 (lipiec 2014): 1–15. http://dx.doi.org/10.4018/ijwnbt.2014070101.
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Efficient channel allocation is the key to fully exploit the signal diversity presented in the multi-carrier physical link in today's broadband wireless access networks. There are mounting evidences that the 4G and future-generation systems will take advantage of two opposite types of access methods, one using centralized control method and the other using a distributed approach. The authors study the distributed channel allocation problem in this article, formulated as a non-linear optimization problem, in broadband wireless networks. The signal properties of the multi-carrier radio interface in 3G and 4G networks are discussed to comprehend the complexity of the channel allocation problem. The authors propose a novel distributed heuristic algorithm based on the particle-swarm searching method. The distributed approach allows user stations to quickly switch sub-carriers with minimum intervention from the base station. The work presented in this paper shows an effective method to allocate a large number of channels while minimizing the possible interference. Extensive numerical experiments are conducted to evaluate several versions of distributed channel allocation algorithm for these new problem settings. The authors' results show that PSO-based method converges quickly in all our numerical experiments despite the high-dimensional searching space. The proposed technologies will eventually allow the true mobile steaming video/audio experience anywhere and anytime, which will have the huge impact to business, entertainment and people's quality of life.
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Alsewaidi, Fatemah, Angela Doufexi i Dritan Kaleshi. "Enhancing Radio Access Network Performance over LTE-A for Machine-to-Machine Communications under Massive Access". Mobile Information Systems 2016 (2016): 1–16. http://dx.doi.org/10.1155/2016/5187303.
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The expected tremendous growth of machine-to-machine (M2M) devices will require solutions to improve random access channel (RACH) performance. Recent studies have shown that radio access network (RAN) performance is degraded under the high density of devices. In this paper, we propose three methods to enhance RAN performance for M2M communications over the LTE-A standard. The first method employs a different value for the physical RACH configuration index to increase random access opportunities. The second method addresses a heterogeneous network by using a number of picocells to increase resources and offload control traffic from the macro base station. The third method involves aggregation points and addresses their effect on RAN performance. Based on evaluation results, our methods improved RACH performance in terms of the access success probability and average access delay.
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Mukubwa, Emmanuel, i Oludare Sokoya. "Efficient Channel Estimation in Massive MIMO Partially Centralized Cloud-Radio Access Network Systems". International Journal of Embedded and Real-Time Communication Systems 12, nr 1 (styczeń 2021): 64–86. http://dx.doi.org/10.4018/ijertcs.20210101.oa4.
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This article investigates channel estimation problem in massive MIMO partially centralized cloud-RAN (MPC-RAN). The channel estimation was realized through compressed data method to minimize the huge pilot overhead, then combined with parallel Givens data projection method (PGDPM) to form a semi-blind estimator. Comparison and analysis of improved minimum mean square error (MMSE), fast data projection method (FDPM), compressed data, and PGDPM techniques was evaluated for achievable normalized mean square error (NMSE) in MPC-RAN. The PGDPM-based estimator had the lowest normalized mean square error. The FDPM and PGDPM based methods are comparable in performance with PGDPM based estimator having a slight edge over FDPM-based estimator. This vindicates PGDPM-based estimator as a method to be utilized in channel estimation since it compresses the massive MIMO channel information, hence mitigating the fronthaul finite capacity problem, and at the same time, it is geared towards efficient parallelization for optimal BBU resource utilization.
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Al-Wasity, Salim M. "New E-Learning opportunities based Artificial Neural Networks for Mobility impairments". Journal of Kufa for Mathematics and Computer 1, nr 8 (30.12.2013): 37–47. http://dx.doi.org/10.31642/jokmc/2018/010806.
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E-learning is becoming globally widespread and more common. The usefulness of interactive systems in e-learning lies not in performing the processing task itself but in communicating requests and results between the system and its user. Therefor the E-Learning can offer great chances to students with disabilities that can access its application through an alternative channel using Human- Computer interaction (HCI) methods. This paper tries to review the various methods of (HCI) used for mobility disabilities and implement one of these methods using Electrooculography (EOG) signals to write using a virtual keyboard.
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Fateh, Rachid, Anouar Darif i Said Safi. "An Extended Version of the Proportional Adaptive Algorithm Based on Kernel Methods for Channel Identification with Binary Measurements". Journal of Telecommunications and Information Technology 3, nr 2022 (29.09.2022): 47–58. http://dx.doi.org/10.26636/jtit.2022.161122.
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In recent years, kernel methods have provided an important alternative solution, as they offer a simple way of expanding linear algorithms to cover the non-linear mode as well. In this paper, we propose a novel recursive kernel approach allowing to identify the finite impulse response (FIR) in non-linear systems, with binary value output observations. This approach employs a kernel function to perform implicit data mapping. The transformation is performed by changing the basis of the data In a high-dimensional feature space in which the relations between the different variables become linearized. To assess the performance of the proposed approach, we have compared it with two other algorithms, such as proportionate normalized least-meansquare (PNLMS) and improved PNLMS (IPNLMS). For this purpose, we used three measurable frequency-selective fading radio channels, known as the broadband radio access Network (BRAN C, BRAN D, and BRAN E), which are standardized by the European Telecommunications Standards Institute (ETSI), and one theoretical frequency selective channel, known as the Macchi’s channel. Simulation results show that the proposed algorithm offers better results, even in high noise environments, and generates a lower mean square error (MSE) compared with PNLMS and IPNLMS.
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Chen, Yini, i Ting Chi. "How Does Channel Integration Affect Consumers’ Selection of Omni-Channel Shopping Methods? An Empirical Study of U.S. Consumers". Sustainability 13, nr 16 (11.08.2021): 8983. http://dx.doi.org/10.3390/su13168983.
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In recent years, fashion brands and retailers have been advancing rapidly to provide U.S. consumers more seamless omni-channel shopping experiences. The pandemic has further accelerated the growth of omni-channel shopping. This study aimed to explore the effects of channel integration in six aspects (i.e., promotion, product and price, transaction information, information access, order fulfillment, and customer service) on the U.S. consumers’ intentions to use three omni-channel shopping methods: buy online pick-up in-store (BOPI), buy online curbside pickup (BOCP), and buy in-store home delivery (BIHD). We proposed a mediation model to test the effects through consumer perceived values (hedonic value, utilitarian value), perceived risk, and perceived behavioral control. Furthermore, this study explored the moderating effect of perceived COVID-19 vulnerability on the relationships between consumers’ internal evaluations of channel integration and their shopping method selection intentions. A total of 516 eligible responses were gathered through a survey of U.S. consumers. Multiple regressions were applied to test the hypotheses. Six types of channel integration showed significant effects on the U.S. consumers’ internal evaluations, which in turn influence their intentions to use certain types of omni-channel shopping methods. Overall, the proposed model exhibits a satisfactory explanatory power.
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Yu, Wenbin, Fei Chen, Zeyu Xu, Yifan Zhang, Alex X. Liu i Chengjun Zhang. "Multi-Access Channel Based on Quantum Detection in Wireless Optical Communication". Entropy 24, nr 8 (29.07.2022): 1044. http://dx.doi.org/10.3390/e24081044.
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In this paper, we propose a novel multi-user access in wireless optical communication based on the quantum detection of the coherent state. In this case, the coherent states are used as the signal carrier and a technique of quantum detection is applied to distinguish between signals from different users. To accomplish this task, two main quantum measurement methods are introduced; one is minimum error discrimination (MED), and the other is unambiguous state discrimination (USD). The theoretical derivation implies that the two methods can both distinguish between the signals from different users efficiently when the average photon number is large enough. Typically, the numerical result shows that in the two-user case, the channel capacity will approach the theoretical maximum limit when the average photon number is greater than 2.5 for MED and 5 for USD in the absence of noise. The MED gains more channel capacity than the USD at the same average photon number. However, the USD wins the error-correction scene with its free-error capability. Furthermore, the detection error probability and channel capacity for the USD with the thermal noise are examined. The result shows that increasing the signal average photon number can continue the USD’s advantage of error-free detection even if in the presence of thermal noise. In addition, compared with non-orthogonal multiple access (NOMA), the bit error rate (BER) against signal-to-noise rate (SNR) performance of USD has been improved.
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Sinyuk, A. D., i O. A. Ostroumov. "UNAUTHORIZED INFORMATION RECOVERY CHANNEL MODEL". H&ES Research 13, nr 3 (2021): 60–67. http://dx.doi.org/10.36724/2409-5419-2021-13-3-60-67.
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Large amounts of information are stored in hard disk drives. In modern information systems. Deleting files using the operating system or reformatting the magnetic drive does not delete the data. There is an opportunity to recover the data by the violator in the conditions of moving the drive from the controlled premises for disposal, sending for repair, theft, replacement, substitution, donation, etc. The known information destruction methods are not always economical and do not fully meet the reliability requirement. The modern methods selection of information recovery is carried out. During the implementation of software methods for destroying information, the overwriting of the masking sequence above deleted information is carried out. This does not guarantee its destruction, because the motion path of the hard disk recording head does not exactly coincide with the magnetic track, and residual magnetization regions carrying information about previous records are formed at the edges. It is assumed that the intruder owns one of the most advanced high-resolution information recovery technologies for studying the areas of residual magnetization. The technology of magnetic scanning microscopy is proposed, which is closely associated with an increase in the recording density of information on storage devices. The carried out operating principles analysis of modern magnetic scanning microscopes made it possible to create conditions for the model development of an unauthorized information recovery channel that includes an information source representing the drive surface and the intruder’s equipment for access to residual information. A source with an intruder connects an information transmission channel, which is proposed to be described by a model of a binary symmetric channel without memory. The erroneous recovery probability estimates of deleted information block and the errors average number in an information block are given. The results can be recommended to specialists in the field of building subsystems to protect information from unauthorized access to information systems for the synthesis of an adequate model of the intruder, development and selection, as well as assessing the developed methods reliability for the confidential information destruction.