共查询到20条相似文献，搜索用时 15 毫秒
1.
《Journal of The Franklin Institute》2021,358(18):10232-10249
In this paper, we investigate the physical-layer security for an Internet of Things (IoT) relaying network employing non-orthogonal multiple access (NOMA) in the context of non-linear energy harvesting. In particular, a power-constrained source transmits its confidential information to a destination via an IoT device, which first decodes the received signal and then forwards the decoded data together with its own information using the NOMA technique to their respective destinations, while an eavesdropper is overhearing this transmission. Considering the scenario that both the power-constrained source and the IoT device are assumed to work under non-linear energy harvesting modes, and are capable of harvesting energy from a power beacon with a time switching protocol, both analytical and asymptotic expressions for secrecy outage probability as well as the analytical expression for the probability of strictly positive secrecy capacity are derived. In addition, those expressions are also verified with Monte-Carlo simulations. 相似文献
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Cooperative diversity has been widely used in wireless communication systems since they greatly improves and enhances the quality of service as being virtual antennas without physically placing multiple antennas at the transmitter or the receiver sides. In this paper, we consider the amplify and forward (AF) relay-based communication systems under the influence of Nakagami-m multipath fading channels in both channel links. Several performance metrics are considered in this study, including, the bit error rate (BER), the ergodic channel capacity, and the outage capacity. The obtained expressions are in closed-form and can reduce to the Rayleigh channel model, as a special case. Numerical results are also provided for the obtained expressions and some conclusions are drawn. 相似文献
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《Journal of The Franklin Institute》2019,356(12):6741-6756
This paper presents general, closed-form, and exact expressions for cumulative distribution function, probability density function and average value for the ratio of independent η-μ random variables, with arbitrary parameters. More specifically, the outage capacity with peak interference power constraint, the delay-limited capacity, and the ergodic capacity considering constraints on the interference power are derived for non-homogeneous environments containing multipath waves clusters. Numerical curves are presented to evaluate the effects of the general fading variables in spectrum sharing systems. Besides, the results are validated by performing Monte-Carlo simulations. Notably, the provided results find important applications in cognitive radio systems considering the spectrum sharing approach and channels modeled by η-μ distribution. 相似文献
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The performance of a Wideband Code Division Multiple Access (W-CDMA) system using Pseudo Noise (PN) codes and chaotic codes in the presence of a Weibull fading channel is studied in this paper. The W-CDMA system modeled using Gaussian Approximation is analyzed on a Weibull fading channel which fades the amplitude of the transmitted signal randomly according to the Weibull distribution. Closed-form expressions for Bit Error Rate (BER) are derived and expressed in terms of Meijer?s-G function. Performance measures in terms of BER are plotted versus Signal-to-Noise Ratio (SNR) for various values of fading severity, average fading power, and channel memory using PN and chaotic codes. Performance comparison between PN codes and chaotic codes are also analyzed. 相似文献
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Zvezdan M. Marjanović Goran T. Djordjević Gradimir V. Milovanović 《Journal of The Franklin Institute》2018,355(2):965-980
In this paper, we analyze detection of multilevel phase-shift keying (MPSK) signals transmitted over a Gamma shadowed Nakagami-m fading channel. We derive novel analytical expression, in terms of Meijer’s G function, for Fourier coefficients of the probability density function of the received signal composite phase. Under the assumption of the imperfect reference signal extraction in the receiver, which is performed from the pilot signal, the analytical expression is derived for the symbol error probability (SEP) in the form of convergent series. The existence of the error floor is identified, and expression for its computation is provided. Mathematical proofs for convergence of Fourier series are provided for both SEP and SEP floor, and novel expressions of upper bounds for truncation errors are derived in terms of elementary mathematical functions. The convergence rate of the derived expressions is examined. Numerical results are confirmed independently by Monte-Carlo simulations. 相似文献
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Approximate mathematical form expressions were derived for the estimation of the average (ergodic) capacity and the average bit error rate of a log-normal free space optical channel in the cases of weak to moderate atmospheric turbulence conditions. We investigate the average capacity, the average bit error rate and the outage probability of free space optical communication channels using the frequentist and the Bayesian approach. Emphasis is given on the cases of weak to moderate atmospheric turbulence leading to channels modeled by log-normal distributed intensity fading. Furthermore, accurate approximate closed-form expressions and estimation procedures for their achievable capacity as well as their bit error rate and the important parameters of interest are derived. The derived approximate analytical expressions are verified by various numerical examples and simulations. Moreover, each methodology is reviewed in terms of their analytic convenience and their accuracy is also discussed. 相似文献
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An integrated base station assignment, diversity and power control algorithm is proposed to realize the base station sharing, in which primary users (PUs) and secondary users (SUs) can connect to any base station by the variable base station assignment, so that the radio resource is efficiently utilized for cognitive radio networks. We show that this algorithm reduces SU's outage rate (for failing to meet the requirement of SINR per bit) while always meeting the requirement of SINR per bit for all PUs. 相似文献
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In this paper, a study on the end-to-end performance of dual-hop non-regenerative relaying over independent generalized-K (KG) fading channels is presented. Using a suitable upper bound for the end-to-end signal-to-noise ratio (SNR), novel closed-form expressions for the cumulative distribution function (CDF), probability density function (PDF) and the moments of this bounded SNR are derived. These results can be afterwards used to obtain important performance metrics of the considered system such as the outage probability and the error performance of digital modulation schemes. In the case of independent but non-necessarily identical fading channels, lower bounds for the average bit error probability (ABEP) for different modulation schemes are determined by using the Padé approximants method. For the case of identical fading channels, closed-form lower bounds for the ABEP are derived. Various numerical and computer simulation results illustrate the proposed analysis. 相似文献
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《Information processing & management》2020,57(2):102153
Social applications foster the involvement of end users in Web content creation, as a result of which a new source of vast amounts of data about users and their likes and dislikes has become available. Having access to users’ contributions to social sites and gaining insights into the consumers’ needs is of the utmost importance for marketing decision making in general, and to advertisement recommendation in particular. By analyzing this information, advertisement recommendation systems can attain a better understanding of the users’ interests and preferences, thus allowing these solutions to provide more precise ad suggestions. However, in addition to the already complex challenges that hamper the performance of recommender systems (i.e., data sparsity, cold-start, diversity, accuracy and scalability), new issues that should be considered have also emerged from the need to deal with heterogeneous data gathered from disparate sources. The technologies surrounding Linked Data and the Semantic Web have proved effective for knowledge management and data integration. In this work, an ontology-based advertisement recommendation system that leverages the data produced by users in social networking sites is proposed, and this approach is substantiated by a shared ontology model with which to represent both users’ profiles and the content of advertisements. Both users and advertisement are represented by means of vectors generated using natural language processing techniques, which collect ontological entities from textual content. The ad recommender framework has been extensively validated in a simulated environment, obtaining an aggregated f-measure of 79.2% and a Mean Average Precision at 3 (MAP@3) of 85.6%. 相似文献
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This paper investigates the joint design of power control and beamforming codebooks for limited-feedback multiple-input single-output (MISO) wireless systems. The problem is formulated as the minimization of the outage probability subject to the transmit power constraint and cardinality constraints on the beamforming and power codebooks. We show that the two codebooks need to be designed jointly in this setup, and provide a numerical method for the joint optimization. For independent and identically distributed (i.i.d.) Rayleigh channel, we also propose a low-complexity approach of fixing a uniform beamforming codebook and optimizing the power codebook for that particular beamformer, and show that it performs very close to the optimum. Further, this paper investigates the optimal tradeoffs between beamforming and power codebook sizes. We show that as the outage probability decreases, optimal joint design should use more feedback bits for power control and fewer feedback bits for beamforming. The jointly optimized beamforming and power control modules combine the power gain of beamforming and diversity gain of power control, which enable it to approach the performance of the system with perfect channel state information as the feedback link capacity increases—something that is not possible with either beamforming or power control alone. 相似文献
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Diomidis S. Michalopoulos George K. Karagiannidis 《Journal of The Franklin Institute》2008,345(7):723-728
In this paper, we provide closed-form expressions for the symbol error probability of decode and forward cooperative diversity systems, when operating over independent but not necessarily identically distributed Nakagami-m fading channels. The results hold for arbitrary number of relays, and refer to the M-ary QAM and M-ary PSK modulations. 相似文献
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This paper is aimed to investigate the operating characteristics of a static synchronous compensator (STATCOM) integrated with superconducting magnetic energy storage (SMES) for high power applications in the transmission network level. The STATCOM controller topology comprises multi-level multi-pulse neutral-point clamped-type (NPC) voltage source inverters (VSIs) using the harmonics cancellation technique, and incorporates a SMES coil. An innovative two-quadrant multi-level dc-dc converter is proposed to effectively interface the STATCOM with the superconducting coil using a buck-boost topology with neutral point voltage control capabilities; thus enabling to simultaneously control both active and reactive power exchange with the high voltage power system. A detailed analysis of major system variables is presented, including analytical results and digital simulations using the MATLAB/Simulink environment. Moreover, a three-level control scheme is designed, including a full decoupled current control strategy in the d-q reference frame with a novel controller to prevent the STATCOM dc bus capacitors voltage drift/imbalance and an enhanced power system frequency controller. 相似文献
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In this paper, a new source selection algorithm for uncooperative distributed information retrieval environments is presented. The algorithm functions by modeling each information source as an integral, using the relevance score and the intra-collection position of its sampled documents in reference to a centralized sample index and selects the collections that cover the largest area in the rank-relevance space. Based on the above novel metric, the algorithm explicitly focuses on addressing the two goals of source selection; high-recall, which is important for source recommendation applications and high-precision which is important for distributed information retrieval, aiming to produce a high-precision final merged list. 相似文献
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News source evaluations based on fact-checking can help curb the consumption and spread of fake news on social media. Prior research has primarily considered source evaluations with intuitive icons that indicate whether or not news sources are reputable. But can we increase the power of these icons by adding more detailed information about the evaluation that explains the reasons for the icon? What additional benefit would such evaluation details bring? Would they have the same effect for both positive and negative evaluations? We conducted two online experiments to understand the effects of a source evaluation icon (a positive or negative summary of the evaluation) and more detailed evaluation information explaining the reasons for the icon. Our results show an asymmetric effect of positive and negative icons and details. Negative icons reduced the believability of the articles, but adding evaluation details supporting the icon had no additional effect. In contrast, positive icons had no significant effects, but adding evaluation details significantly increased believability. We also found that users were more likely to view the evaluation details when the content of the article aligned with their pre-existing opinions, but the valence of the icon (positive or negative) did not affect this decision. 相似文献
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针对无线协作多播网络中的能量效率问题,设计了一种基于功率控制的能效优化策略。通过采用功率控制因子来限制系统总的能耗,按照最小信噪比原则进行中继节点选择,来增加系统吞吐量。该策略合理分配了基站和中继节点的功率,扩大了系统的覆盖范围,提高了发射效率。仿真结果表明了,与传统传输机制相比,完全搜索算法和变功率中继选择算法在效率方面有了较大提高,而时间分配算法则找到了最优的转发时间比例。 相似文献
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作为新一代宽带业务的国际标准(4G时代),LTE网络采用了许多新技术。它采用扁平化网络构架的方式进行设计,包括一些聚合多载波、异构网络、中继、多点发送、MIMO和先进的抗干扰管理等技术。这些技术极大地提高了小区边缘用户的一些性能,使小区的信息传输速率和系统容量得以增加。 相似文献
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用户参与企业创新是提高新产品开发绩效的重要手段,但在吸纳用户参与自身创新过程时,企业需要在开放式创新的价值共创之利与管理复杂性之弊之间进行权衡。不同类型用户参与对企业NPD效应的差异及影响机理仍未得到充分揭示。基于创新理论与组织理论,采用444份国内企业样本,探索用户作为企业外部能动的创新源参与到企业创新过程中,对企业的组织协调机制及技术创新绩效的影响。发现：企业吸纳用户参与创新将有利于提升NPD绩效,但不同模式的用户参与提升企业NPD绩效的组织过程存在差异;用户以信息提供的方式参与企业创新,对企业NPD提升效应最强;组织跨界协调在用户参与提升企业NPD绩效的过程中起中介作用,特别是,对于用户作为独立创新者的参与方式,企业须经由正式设计的跨职能沟通机制,才能真正利用其有效贡献于企业NPD绩效的提升,否则用户独立创新可能对企业NPD绩效造成损害。文章最后讨论了理论贡献、管理意义与研究局限。 相似文献
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Wireless communication channels can be complex and exhibit unpredictable behavior. This behavior can be successfully represented by stochastic processes undergoing random perturbation due to shifts in the underlying physical state of the channel. These state transitions manifest themselves as changes in channel power level measurements taken over time from a remote reference beacon. In this paper, we expand the application of switched process theory to develop models of maritime and land satellite communications using generalized switched Fokker-Planck equation techniques. This application yields a broad class of models that may be treated analytically and numerically. These models are ideal for system-level simulation due to high numerical efficiency and limited maintenance calculation requirements. 相似文献
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A qualitative study of user information needs is reported, based on a purposive sample of users and potential users of the Vaughan Williams Memorial Library, a small specialist folk music library in North London. The study set out to establish what the users’ (both existing and potential) information needs are, so that the library’s online service may take them into account with its design. The information needs framework proposed by Nicholas [Nicholas, D. (2000) Assessing information needs: tools, techniques and concepts for the internet age. London: ASLIB] is used as an analytical tool to achieve this end. The demographics of the users were examined in order to establish four user groups: Performer, Academic, Professional and Enthusiast. Important information needs were found to be based on social interaction, and key resources of the library were its staff, the concentration of the collection and the library’s social nature. A collection of broad design requirements are proposed based on the analysis and this study also provides some insights into the issue of musical relevance, which are discussed. 相似文献