共查询到20条相似文献，搜索用时 15 毫秒
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《Journal of The Franklin Institute》2021,358(16):8772-8785
Conventional grant-based random access scheme is inappropriate to massive Internet of Things (IoT) connectivity since massive devices results in large number of collisions. This is unacceptable for the low latency requirement in 5 G and future networks. It is also not possible to assign orthogonal pilot sequences to all users to perform user activity detection (UAD) due to the massive number of devices and limited channel coherence time. In this paper, a novel grant-free (GF) UAD scheme is proposed with extremely low complexity and latency in an IoT network with a massive number of users. We exploit multiple antennas at the base station (BS) to produce spatial filtering by a fixed beamforming network (FBN), there then the inter-beam interference can be mitigated. Moreover, intra-beam interference is removed in temporal domain by orthogonal multiple access (OMA) technology. Joint UAD and multiuser detection (MUD) is realized by a bank of spatial-temporal matched filters at BS. The proposed method is efficient and the complexity is much less than the existing compressed sensing (CS)-based GF non-orthogonal multiple access (GFNOMA) algorithms. Performances of the proposed method is extensively analyzed in terms of the successful activity detection rate (SADR) as well as the Receiver operating characteristic (ROC) based on Neyman-Pearson (NP) decision rule. Numerical results demonstrate that it is comparable to the recently proposed iterative Maximum Likelihood (ML) algorithm, yet the computation load of the proposed scheme is extensively reduced. 相似文献
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马赛克是多年来困扰广电工作者的问题,目前我国大多数无线覆盖台站仍沿用人工监看的方法来监测电视视频的马赛克现象,这一做法显然已不能满足愈来愈高的安全播出要求。文章提出一种基于MATLAB的视频马赛克检测算法,在对视频图像进行canny边缘检测的基础上,通过模板匹配来实现马赛克检测,仿真实验的结果验证了本算法的有效性和实时性。 相似文献
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苏玉欣 《科技成果管理与研究》2011,(8):82-84
在无线网络设计中,与传统基站不同,分布式基站的BBU＋RRU独特架构使其在特殊场景的网络设计中具有更多的灵活性。文章主要介绍了分布式基站基本概念、技术特点,并对其在实际无线网络设计中的应用进行了分析。 相似文献
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This paper proposes four resource (subcarriers-and-bits) allocation methods for OFDMA-based multiuser MIMO system. We employ adaptive modulation according to the channel state information (CSI) of each user to meet the symbol error rate (SER) requirement. The first scheme is based on transmit spatial diversity (TSD), in which the vector channel with the highest gain between the base station and specific antenna at remote terminal is chosen for transmission. The second scheme assigns subcarrier to the best user and employs spatial multiplexing on the MIMO system to further enhance the throughput. The space-division multiple-access (SDMA) scheme assigns single subcarrier simultaneously to the remote terminals with pairwise “nearly orthogonal” spatial signatures. In the fourth scheme, we propose to design the transmit beamformers based on the zero-forcing (ZF) criterion such that the multi-user interference (MUI) is completely removed. Moreover, spatial multiplexing technique is jointly exploited to achieve throughput multiplication. Numerical results demonstrate that all the proposed algorithms are simple and reliable and the fourth scheme is the best since all users are allowed to share single subcarrier. 相似文献
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为了有效的抑制多址干扰,本文提出了一种基于子空间的次分量分析恒模盲多用户检测算法.该方法是将子空间方法与次分量分析恒模算法相结合,有效的消除来自噪声子空间分量的影响.仿真结果表明,在相同的多址干扰情况下,本文建议方法的输出信干噪比比次分量分析恒模算法提高了11dB,比线性约束最小二乘恒模算法提高了17 dB;在不同的多... 相似文献
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在GPS(全球定位系统)、GPRS(通用分组无线服务技术)以及利用GSM电信基站进行辅助定位的A-GPS技术都已经十分成熟的今天,我们可以使用这些定位技术及无线传输技术配合同样十分成熟的WEB应用软件开发技术和强大的SQL SERVER数据库管理系统开发出一套集管理、调度和监控为一体的部队车辆管理系统,以实现高效、低耗、可靠、安全的军用车辆管理目标。 相似文献
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《Information processing & management》2023,60(2):103175
Task assignment, the core problem of Spatial Crowdsourcing (SC), is often modeled as an optimization problem with multiple constraints, and the quality and efficiency of its solution determines how well the SC system works. Fairness is a critical aspect of task assignment that affects worker participation and satisfaction. Although the existing studies on SC have noticed the fairness problem, they mainly focus on fairness at the individual level rather than at the group level. However, differences among groups in certain attributes (e.g. race, gender, age) can easily lead to discrimination in task assignment, which triggers ethical issues and even deteriorates the quality of the SC system. Therefore, we study the problem of task assignment with group fairness for SC. According to the principle of fair budget allocation, we define a well-designed constraint that can be considered in the task assignment problem of SC systems, resulting in assignment with group fairness. We mainly consider the task assignment problem in a common One-to-One SC system (O2-SC), and our goal is to maximize the quality of the task assignment while satisfying group fairness and other constraints such as budget and spatial constraints. Specifically, we first give the formal definition of task assignment with group fairness constraint for O2-SC. Then, we prove that it is essentially an NP-hard combinatorial optimization problem. Next, we provide a novel fast algorithm with theoretical guarantees to solve it. Finally, we conduct extensive experiments using both synthetic and real datasets. The experimental results show that the proposed constraint can significantly improve the group fairness level of algorithms, even for a completely random algorithm. The results also show that our algorithm can efficiently and effectively complete the task assignment of SC systems while ensuring group fairness. 相似文献
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This paper presents a new method for the performance evaluation of bit decoding algorithms. The method is based on estimating the probability density function (pdf) of the bit log likelihood ratio (LLR) by using an exponential model. It is widely known that the pdf of the bit LLR is close to the normal density. The proposed approach takes advantage of this property to present an efficient algorithm for the pdf estimation. The moment matching method is combined with the maximum entropy principle to estimate the underlying parameters. We present a simple method for computing the probabilities of the point estimates for the estimated parameters, as well as for the bit error rate. The corresponding results are used to compute the number of samples that are required for a given precision of the estimated values. It is demonstrated that this method requires significantly fewer samples as compared to the conventional Monte-Carlo simulation. 相似文献
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刘田茜 《科技成果管理与研究》2009,(7):36-39
本文在考虑满足不同的性能指标或某种实际要求时的基础上,提出了一种基于优化理论的有源电力滤波器的控制算法。该算法针对满足一定约束要求下来设计有源滤波器（APF：Active Power Filter）补偿性能,其补偿电流在a-b-c坐标系内确定,无需坐标变换．APF控制电路的实现比起传统方法相对简单,并通过仿真实验证明此算法有很好的滤波效果。 相似文献
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多用户MIMO-OFDM系统中基于迫零波束成型的自适应资源分配算法 总被引：2，自引：0，他引：2
针对多用户环境下的多天线正交频分复用下行系统,提出了2种有效的基于迫零波束成型的自适应资源分配算法.所提算法在保证每个用户的速率要求的情况下,通过自适应的功率、子载波和比特分配,最小化系统的发送功率.仿真结果表明,提出的2种次优的分配算法在满足用户的速率要求下能达到很好的系统性能. 相似文献
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电视台的核心工作之一就是确保广播电视节目的安全播出。而机房作为广播电视台的“硬件核心”所在,其维护与管理是保障广播电视安全播出的前置条件。基于此认识,本文着力阐述电视台安全播出的含义、机房的维护技术,并结合工作实际,对县级广播电视台安全播出方面存在的问题,提出可行的改进措施,以期提高广播电视台机房的维护管理水平、保证电视节目的安全播出,为广大受众提供更为优质的视听服务。 相似文献
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传统的基站温度控制主要依靠空调无间隙的工作模式来实现。这种工作模式造成了能量的大量消耗且只能被动控制基站室内温度对基站维修工作造成影响。本文提出一种基于智能变频技术的通信基站节能方法,利用室外的冷空气代替空调进行节能室内温度降低,结合历史数据使用非线性优化的方法对风机的变换频率进行智能控制。实验结果表明,这种方法能有效避免风机与空调的过度切换,使空调工作在最优的时间段,能使通信基站的能量消耗有效降低。 相似文献
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《Information processing & management》2022,59(5):103028
Assigning paper to suitable reviewers is of great significance to ensure the accuracy and fairness of peer review results. In the past three decades, many researchers have made a wealth of achievements on the reviewer assignment problem (RAP). In this survey, we provide a comprehensive review of the primary research achievements on reviewer assignment algorithm from 1992 to 2022. Specially, this survey first discusses the background and necessity of automatic reviewer assignment, and then systematically summarize the existing research work from three aspects, i.e., construction of candidate reviewer database, computation of matching degree between reviewers and papers, and reviewer assignment optimization algorithm, with objective comments on the advantages and disadvantages of the current algorithms. Afterwards, the evaluation metrics and datasets of reviewer assignment algorithm are summarized. To conclude, we prospect the potential research directions of RAP. Since there are few comprehensive survey papers on reviewer assignment algorithm in the past ten years, this survey can serve as a valuable reference for the related researchers and peer review organizers. 相似文献
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The goal of the study presented in this article is to investigate to what extent the classification of a web page by a single genre matches the users’ perspective. The extent of agreement on a single genre label for a web page can help understand whether there is a need for a different classification scheme that overrides the single-genre labelling. My hypothesis is that a single genre label does not account for the users’ perspective. In order to test this hypothesis, I submitted a restricted number of web pages (25 web pages) to a large number of web users (135 subjects) asking them to assign only a single genre label to each of the web pages. Users could choose from a list of 21 genre labels, or select one of the two ‘escape’ options, i.e. ‘Add a label’ and ‘I don’t know’. The rationale was to observe the level of agreement on a single genre label per web page, and draw some conclusions about the appropriateness of limiting the assignment to only a single label when doing genre classification of web pages. Results show that users largely disagree on the label to be assigned to a web page. 相似文献
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率失真优化技术在视频优化编码中起着重要的作用，广泛地应用于宏块模式决策，优化量化等编码模块中。本文将率失真优化编码与码率控制结合起来进行研究，通过对率失真关系的分析，提出了基于率失真优化的复杂度可分级码率控制算法，并根据缓冲区操作模型的位分配约束条件调整码率控制的位分配过程，从而使得该算法能够在达到码率控制的同时也能取得较高的编码效率，并能保证缓冲区不会发生溢出，然后结合场景变换、图像内容分类等主观质量问题研究，提出一种恒定质量码率控制编码算法。 相似文献
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This paper considers the problem of the leader-following consensus of generally nonlinear discrete-time multi-agent systems with limited communication channel capacity over directed fixed communication networks. The leader agent and all follower agents are with multi-dimensional nonlinear dynamics. We propose a novel kind of consensus algorithm for each follower agent based on dynamic encoding and decoding algorithms and conduct a rigorous analysis for consensus convergence. It is proved that under the consensus algorithm designed, the leader-following consensus is achievable and the quantizers equipped for the multi-agent systems can never be saturated. Furthermore, we give the explicit forms of the data transmission rate for the connected communication channel. By properly designing the system parameters according to restriction conditions, we can ensure the consensus and communication efficiency with merely one bit information exchanging between each pair of adjacent agents per step. Finally, simulation example is presented to verify the validity of results obtained. 相似文献