共查询到20条相似文献,搜索用时 171 毫秒
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高俊磊 《数字社区&智能家居》2007,(10):146-147,153
提出了一种改进的OFDM系统中自适应比特功率分配算法。该算法可适用于多径频率选择性衰落信道,根据信道特征,动态地为OFDM系统的各子信道分配比特和发送功率。该算法在一定的误比特率和信息速率的情况下,使得总发送功率最小化。仿真结果表明,该算法在相同误比特率的情况下比不采用自适应技术的OFDM系统节省了发送功率。 相似文献
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高俊磊 《数字社区&智能家居》2007,(19)
提出了一种改进的OFDM系统中自适应比特功率分配算法.该算法可适用于多径频率选择性衰落信道,根据信道特征,动态地为OFDM系统的各子信道分配比特和发送功率.该算法在一定的误比特率和信息速率的情况下,使得总发送功率最小化.仿真结果表明,算法在相同误比特率的情况下比不采用自适应技术的OFDM系统节省了发送功率. 相似文献
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自适应功率分配技术可以最大限度提高OFDM传输系统的信道容量和传输质量.是多用户OFDM系统中的关键技术.分析和比较了非理想信道估计情况下,信道估计误差对当前三种主要OFDM适应功率分配算法性能的影响.仿真结果表明,无论是理想信道估计还是存在误差的非理想信道估计条件下.理想频谱平衡算法和迭代频谱平衡算法的性能总是优于迭代注水算法.但是,随着信道估计误差的不断增大,迭代注水算法的性能具有较好的稳健性.对设计实际系统有重要的指导意义. 相似文献
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自适应OFDM算法及其在煤矿井下无线通信系统中的应用 总被引:1,自引:0,他引:1
由于频率选择性衰落,OFDM的每个子信道的频率响应各不相同,为了保证系统的误码率性能,OFDM只能根据衰减最大的子信道来决定比特和功率的分配,造成很大的浪费。因此,文章提出了一种自适应OFDM(AOFDM)算法,该算法使得OFDM的每个子载波都能根据信道特性动态的变化选择调制方式和功率分配,最好地匹配信道容量。文章详细介绍了AOFDM的比特、功率算法,并详细分析了煤矿井下无线通信系统的特点,指出AOFDM算法非常适用于煤矿井下无线通信系统,并给出了基于AOFDM的矿井无线通信系统的组成框图,仿真结果表明使用效果良好。 相似文献
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《计算机应用与软件》2016,(2)
针对正交频分复用(OFDM)系统利用传统压缩感知算法进行信道估计需要已知信道稀疏度等消息,且算法复杂度高,重构时间长的问题,提出改进贝叶斯压缩感知算法进行OFDM信道估计。该算法将正交频分复用系统的信道估计转化为贝叶斯压缩感知重构问题,在不需要预先知道信道稀疏度信息的情况下,通过优化重构过程中的基函数选择方法,将基函数从1个开始逐渐增加,而不是删除,进而得到信道估计值以及误差范围,使该算法具有更快的收敛速度。仿真结果表明,与传统信道估计算法相比,该算法不需要信道的稀疏度信息,并且重构精度更高,在低信噪比的情况下估计效果更好,提高了运算速度,降低了复杂度。 相似文献
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提出一种具有全局优化能力的改进粒子群算法,将信道分配和比特功率分配问题相结合,实现电力线信道下多用户自适应OFDM比特功率分配。在典型低压电力线通信信道环境下的matlab仿真结果表明:本文提出的算法可行且有效,适合多用户通信环境,节省了多用户自适应OFDM系统的运算时间,降低了发射功率,且算法简单易操作,有望应用于更广泛的优化问题。 相似文献
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简要介绍几种OFDM同步算法,在此基础上提出一种基于短训练序列的联合CP的时频同步算法,这种算法可以在多径衰落信道的情况下提高OFDM系统的定时和频偏估计的准确性,同时减小系统的误码率,最后利用软件对联合算法在多径信道情况下进行仿真与分析,并且获得良好的仿真结果. 相似文献
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MIMO/OFDM是未来宽带无线通信接口的有效架构。本文提出了一种自适应跨层空间子信道分配算法,在多用户MIMO/OFDM系统中,联合链路层截短ARQ(T-ARQ)技术,以获取物理层最大的系统吞吐量为目标,推导了子载波分配准则,并给出了相应的算法流程。仿真结果表明,该算法具有良好的性能,有效地提高了系统的传输速率。 相似文献
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针对正交频分复用(OFDM)信号的高峰均功率比问题,提出了一种基于优化功率分配的OFDM峰均功率比抑制机制OPAR。在考虑功率放大器转化效率的前提下,分析了功率转化效率与峰均功率比之间的关系,推导了叠加的导频信号与数据信号功率分配的闭环表达关系式。在给定子载波数与峰均功率比概率阈值的条件下,OPAR能快速优化导频信号与数据信号的最佳功率分配。实验结果及与现有的机制比较表明,提出的OPAR机制可以获得更好的峰均功率比改善性能。 相似文献
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In wireless communication reception, the reliability of orthogonal frequency division multiplexing (OFDM) is limited because of the time-varying nature of the channel. This causes inter-carrier interference (ICI) and increases inaccuracies in channel tracking. This can effectively be avoided at the cost of power loss and bandwidth expansion by inserting a cyclic prefix guard interval before each block of parallel data symbols. However, this guard interval decreases the spectral efficiency of the OFDM system as the corresponding amount. Recently, it was found that based on Haar-orthonormal wavelets, discrete wavelet-based OFDM (DWT-OFDM) is capable of reducing the inter symbol interference (ISI) and ICI, which are caused by the loss in orthogonality between the carriers. DWT-OFDM can also support much higher spectrum efficiency than discrete Fourier-based OFDM (DFT-OFDM). In this paper the DFT-OFDM is replaced by Multiwavelets OFDM (DMWT-OFDM) in order to further reduce the level of interference and increase spectral efficiency. It is found that proposed Multiwavelet design achieves much lower bit error rates, increases signal to noise power ratio (SNR), and can be used as an alternative to the conventional OFDM. The proposed OFDM system was modeled tested, and its performance was found under different channel conditions. 相似文献
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In this paper,we study the problem of optimal resource allocation for lifetime maximization in an orthogonal-frequencydivision multiplexing(OFDM)system with decode-and-forward relay.The goal is to minimize total energy cost of the system by jointly optimizing power allocation,subcarrier pairing and relay selection.We present a heuristic solution that is composed of two parts.The first part is an optimal power allocation approach to allocate power to a subcarrier pair of the source and the relay.The second part is a modified Hungarian algorithm to make subcarrier pairing and relay selection.Evaluations show that the presented scheme outperforms other schemes in the total transmitted data and the network lifetime. 相似文献
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Ho-Lung Hung 《Computers & Electrical Engineering》2011,37(1):57-70
A low-complexity partial transmit sequence (PTS) technique for reducing the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) system is presented. However, PTS technique requires an exhaustive search over all combinations of allowed phase weighting factors, and the search complexity increases exponentially with the number of sub-blocks in OFDM system. Hence, there has been a trade-off between performance PAPR reduction and computational complexity in PTS OFDM system. The proposed is a sub-optimum PTS for PAPR reduction of OFDM system. Simulation results demonstrate that the superiority of evolutionary computation technique-particle swarm optimization (PSO) based on PTS which can be utilized for finding the optimum phase weighting factors, and can achieve the lower PAPR and computational complexity of OFDM systems. In addition, our evolutionary computation technique can be used to reduce reduction PAPR with comparable performance to genetic algorithm-based PTS, with much less computation cost. 相似文献
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In this contribution, we present a survey on the radio resource allocation techniques in orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division multiple access (OFDMA) systems. This problem goes back to 1960s and that is related to properly and efficiently allocate the radio resources, namely subcarriers and power. We start by overviewing the main open issues in OFDM. Then, we describe the problem formulation in OFDMA, and we review the existing solutions to allocate the radio resources. The goal is to discuss the fundamental concepts and relevant features of different radio resource management criteria, including water-filling, max–min fairness, proportional fairness, cross-layer optimization, utility maximization, and game theory, also including a toy example with two terminals to compare the performance of the different schemes. We conclude the survey with a review of the state-of-the-art in resource allocation for next-generation wireless networks, including multicellular systems, cognitive radio, and relay-assisted communications, and we summarize advantages and common problems of the existing solutions available in the literature. The distinguishing feature of this contribution is a tutorial-style introduction to the fundamental problems in this area of research, intended for beginners on this topic. 相似文献
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针对OFDM信号功率降额问题,提出了一种新的子载波预留方法。该方法利用谷值补偿算法改善OFDM信号的立方度量性能,并使用动态峰值削减算法降低OFDM信号的峰均功率比,同时对原有迭代过程进行简化,合理地控制计算开销。仿真结果表明,与传统的功率降额处理方法相比,该方法可更为有效地降低系统峰均功率比和改善OFDM信号的立方度量性能。 相似文献
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