共查询到19条相似文献,搜索用时 78 毫秒
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机会波束成形(Opportunistic Beamforming,OBF)技术通过加大、加快信道的波动来提高多用户分集增益,将之使用在正交频分复用多址接入(OFDMA)系统中,可以使得系统的吞吐量最大化。在OFDMA系统中,通过对所有子载波进行分簇,可以实现在牺牲系统性能很少的情况下,大大降低系统反馈量。研究了对分簇OFDMA系统使用OBF技术来提高系统吞吐量,并进一步研究了在训练阶段使用多个随机加权向量进行多波束成形,然后从中选择最好的一个来实现数据阶段的波束成形。仿真证明,采用多波束机会波束成形技术能提高OFDMA系统吞吐量。 相似文献
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MIMO—OFDM系统具有空间、时间和频率三维的自由度,结合自适应资源分配技术,使得系统的传输速率、频谱效率及功率利用率等性能进一步优化,同时可以结合波束成形技术进一步提高系统的性能。文章介绍了MIMO—OFDM系统中资源分配的几种方式,分析比较了几种方式的特点和存在的不足,提出进一步研究的内容。 相似文献
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OFDM具有高频谱利用率和抗多径衰落的优点,已被公认为第三代移动通信系统长期演进标准以及第四代移动通信系统的核心技术。OFDMA是基于OFDM的一种多用户接入技术,在OFDMA系统中,各用户在不同的子载波上同时传输数据。主要研究了OFDMA系统中的跨层资源分配算法。详细分析了保证速率比例公平的非实时业务跨层资源分配算法,仿真结果说明该算法能够较好地保证用户之间的公平性,并能够获得较大的系统吞吐量和较小的业务延时。 相似文献
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基于goodput优化的OFDMA系统资源分配算法 总被引:1,自引:1,他引:0
资源分配是OFDMA系统资源调度中的一个重要研究问题。针对OFDMA下行链路信道知识获取的现实误差问题,提出了一种基于实际吞吐量优化的资源分配算法。重点研究了功率和数据率在用户之间的分配问题,以往的很多分配算法通常是假设下行链路发射端具有理想信道信息,这与实际状况不符,同时根据部分信道信息得到的速率分配不被真实的信道支持,会造成传输的中断事件。算法考虑了信道估计的误差问题,将实际吞吐量goodput作为分配算法优化的依据。仿真结果表明,该算法获得了较好的多用户分集增益和实际吞吐量性能。 相似文献
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为了克服MIMO空间各子信道相互干扰,论文对多天线波束成形的MIMO-OFDM跨层自适应资源算法进行了研究。在层资源自适应算法模式下,对于各空间信道相互不独立,存有干扰情况时,利用空频块码SFBC算法,以此来对抗信道干扰,而在各空间信道相互独立的情况下,采用空间波束发送多重性模式,以此来提高系统的数据传输速率。仿真验证表明,采用层资源自适应算法模式,在满足信号质量要求的情况下达到了非常高的传输速率。 相似文献
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MIMO-OFDM系统下的自适应迭代比特分配算法 总被引:1,自引:0,他引:1
针对多输入多输出正交频分复用(MIMO—OFDM)系统提出了一种自适应迭代的调制方案。考虑实际通信系统的要求,在通信上层传输速率和误码率要求一定的情况下,以最小化发射功率为目标,在发射端采用自适应迭代的方法给每个空间子信道分配传输比特、发射功率。在满足用户要求的同时,获得了好的频谱效率,节省了发射功率。并且,采用迭代的方法解决了因发射比特必须取整引起的误差。相比与同类算法,可大大降低计算复杂度。计算机仿真表明提出的方法可以用低的发射功率达到用户要求。 相似文献
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Hiep H. Nguyen Suk‐Hwan Lee Won‐Joo Hwang 《International Journal of Communication Systems》2015,28(14):2020-2034
Because energy efficiency (EE) is inevitable in future wireless cellular networks, in this paper, we focus on improving the number of bits delivered to users for each unit energy consumption in the downlink of orthogonal frequency‐division multiple access cellular networks with base stations (BSs) coordination. Specifically, each BS shares the channel qualities of users with others and jointly choose the set of co‐channel users and the transmit power allocated to maximize the EE of the system subject to the transmit power ceiling of each BS and minimum required data rate. We formulate the problem as a nonlinear fractional optimization problem, using nonlinear fractional programming, the original hard‐to‐solve problem is transferred to a new one that has the same optimal solution and is easier to solve, this enables two iterative algorithms that achieve nearly the same maximum EE. Numerical results are provided to show the convergence and superiority of the two proposed. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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1 Introduction Next-generation wireless communication systems (systems beyond 3G) will be required to provide flexible and easy deployment solution to high-speed communications and to support a variety of services utilizing advanced multiple access techni… 相似文献
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This article investigates two fairness criteria with regard to adaptive resource allocation for uplink orthogonal frequency division multiple access (OFDMA) systems. Nash bargaining solution (NBS) fairness and proportional fairness (PF) are two suitable candidates for fairness consideration, and both can provide attractive trade-offs between total throughput and each user's capacity. Utilizing Karush-Kuhn- Tucker (KKT) condition and iterative method, two effective algorithms are designed, to achieve NBS fairness and proportional fairness, respectively. Simulation results show that the proposed resource allocation algorithms achieve good tradeoff between the overall rate and fairness, with little performance loss from the total capacity. 相似文献
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Dionysis Xenakis Dimitris Tsolkas Nikos Passas Nancy Alonistioti Lazaros Merakos 《Wireless Communications and Mobile Computing》2012,12(11):985-998
Modern wireless orthogonal frequency division multiple access (OFDMA) systems incorporate dynamic resource allocation (DRA), adaptive modulation and coding (AMC), and power control (PC) to exploit multiuser diversity and achieve higher system throughput. In the literature, only a few proposed algorithms deal with the contiguous DRA problem according to which a contiguous collection of resources can be allocated to each user. This paper formulates this high complexity problem, provides a suitable decision metric and a simple yet efficient solution. The proposed algorithm allocates in each step a contiguous collection of resources to the pending user that leads to the highest estimated correctly received number of bits. Simulation results show that, in this way, considerably improved performance can be achieved in terms of overall system throughput, spectral efficiency, and served traffic. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Efficient radio resource allocation is essential to provide quality of service (QoS) for wireless networks. In this article, a cross-layer resource allocation scheme is presented with the objective of maximizing system throughput, while providing guaranteed QoS for users. With the assumption of a finite queue for arrival packets, the proposed scheme dynamically a/locates radio resources based on user's channel characteristic and QoS metrics derived from a queuing model, which considers a packet arrival process modeled by discrete Markov modulated Poisson process (dMMPP), and a multirate transmission scheme achieved through adaptive modulation. The cross-layer resource allocation scheme operates over two steps. Specifically, the amount of bandwidth allocated to each user is first derived from a queuing analytical model, and then the algorithm finds the best subcarrier assignment for users. Simulation results show that the proposed scheme maximizes the system throughput while guaranteeing QoS for users. 相似文献
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提出了一种用于正交频分多址(OFDMA)通信系统下行链路的多小区功率协调分配算法,协调相邻小区在同频子信道上的发送功率,抑制小区间干扰,提高信道容量.将博弈论引入到多小区功率分配中,给出基于定价的多小区非合作功率分配博弈模型,并分析了该博弈的纳什均衡解的存在性和惟一性,给出了该模型的分布式求解算法.通过仿真分别给出了单小区场景与多小区场景下算法性能,讨论了定价因子对系统性能的影响.仿真结果表明,提出的多小区功率协调分配算法可以充分利用无线资源,提高系统吞吐量,降低平均发送功率. 相似文献
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针对多用户OFDM系统自适应比特功率分配优化问题,由于信道的时变性,为更好地分配资源,改进了一种人工免疫的OFDM算法,此算法通过抗体与抗原的亲和来消除抗原的原理,由选定种群数量、编码方式,计算亲和度、浓度、激励度,选择免疫体,抗体保护克隆变异保护,克隆变异,克隆抑制,抗体刷新这些步骤达到优化OFDM系统的目的。选定适应度函数,在误比特率和速率一定的情况下,使得总功率最小,即在某个总功率下,速率达到最大。通过和遗传算法、人工鱼群算法进行仿真比较,证明人工免疫算法是最优的。 相似文献