共查询到19条相似文献,搜索用时 93 毫秒
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为了适应高速率大色散光纤信道对链路色散的精确补偿要求,研究并提出了一种基于射频信号2阶零功率点的信道色散测量方案。采用信号两边带的位相差来测量光纤链路中的色散值,通过在发射端加载射频信号,可以得到接收端射频信号功率大小随链路色散值的周期性变化关系,从仿真光纤链路色散随射频信号频率的变化曲线获得接收端射频信号2阶零功率点位置。结果表明,基于射频信号2阶零功率的信号测量方案色散测量误差可控制在±10ps/nm范围内。相较于1阶零功率点,基于射频信号2阶零功率点信道色散测量方案可满足高速率、长距离大色散光纤信道对色散值的精确测量需求。 相似文献
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传统的合作频谱感知一般将感知环境建模为单级信道,且次用户一般都以相同的发射功率向数据融合中心报告感知数据,难以体现并利用不同次用户感知数据之间的空间分集差异。为解决此问题并有效地设置次用户在感知数据上报阶段的发射功率,该文提出了3种最优功率控制方案,以获得相应设计准则下参与合作感知的次用户最优发射功率。在融合中心理想具备感知信道和报告信道的统计特性时,通过理论推导获得了基于信道统计特性的功率控制闭式解方案;当信道统计特性难以现实具备时,分别获得了基于联合信道统计特性估计的最大特征功率矢量及盲加权多特征功率矢量方案。理论分析和仿真实验表明,在不同的先验信息条件下,3种方案的性能皆远优于缺少功率控制的合作感知方案。 相似文献
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本文研究了在移动信道中,码分多址系统的功率控制策略对单个用户信号功率控制所能达到的精度问题,分析了不同的功率控制策略和参数对传播损耗、慢衰落以及快衰落损耗补偿效果的影响,文中给出了具体的仿真结果,并针对当前码分多址系统功率控制的不完善之处,提出了进一步研究的方向。 相似文献
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为消除过时信道状态信息(CSI)对分布式无线多跳网络环境下跨层资源分配效率的影响,提高跨层联合资源分配的准确性,基于信道相关性提出了一种补偿式跨层联合资源分配算法。利用瞬时和过时信道状态信息之间的条件概率密度函数,基于瑞利衰落信道模型求得信噪比(SINR) 模型下条件容量的闭式解。为补偿部分网络性能的损失,提出了一种考虑过时信道状态信息的联合拥塞控制、信道分配和功率控制的算法,在此过程中网络被建模成一个NUM 问题,可变的链路数据率和功率等资源限制作为约束条件。运用拉格朗日对偶分解技术,NUM问题被分布式求解。实验对比分析表明:在确保较低复杂度的前提下,该算法有效改善了分布式多跳网络资源分配的合理性,使其网络总体效用得到提升,降低了能耗。 相似文献
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该文基于对多用户多速率正交频分复用(OFDM)系统性能的分析,提出了子载波分配和功率控制方案。在采用P-QAM调制的下行链路中,如已知所有子信道的信息状态(CSI),在满足每一个用户的服务质量的前提下,先给固定速率的用户分配最优子信道,再给变速率的用户按照子信道链路增益最大化分配剩余的子信道;每一个用户分配的子信道数目,由链路增益的取值区间决定。信号发射功率则按照注水法则分配:链路增益大的子信道分配的功率大,链路增益小的子信道分配的功率小,则系统的总传输速率可达最大。仿真结果证明了该文提出的分配方案优于Jang的分配方案。 相似文献
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蜂窝车用无线通信(cellular vehicle-to-everything,C-V2X)系统中,基于V2V(vehicle-to-vehicle)车载通信采用复用蜂窝用户(cellular user,CUE)的频谱资源减轻基站负载实现部分近场V2V通信,在提高系统传输速率的同时也产生了同频干扰的问题。针对该问题,提出基于信道反转的动态功率控制方案,在非截断区内对V2V用户(V2V user,VUE)进行信道反转功率控制,补偿因发射功率有限造成的截断中断,通过动态功率控制解决蜂窝用户和V2V用户间的同频干扰。在此基础上,通过拉格朗日乘子法得到目标函数的最优对偶解,利用二分法确定CUE和VUE的最优功率,满足蜂窝用户传输速率要求的同时最大化V2V用户的总传输速率。数值仿真结果表明,当VUE总中断概率为0.866时,该方案使系统性能提升了48%。 相似文献
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在密集小区的认知无线电非正交多址(cognitive radio non-orthogonal multiple access, CRNOMA)网络场景下,针对用户采取Underlay方式复用时信道频带利用率低的问题,提出了一种基于能效的组合用户动态功率分配算法.该算法在保证主用户服务质量前提下,基于用户之间的干扰和信干噪比,优化了组合多用户的接入方案,使信道接入用户数量最大且提高了频带利用率.同时,根据增益排序下的功率差额配比改进了剩余功率再分配方案,使空闲功率重新利用更加合理和有效.仿真结果表明,本文算法可以有效实现接入用户数量最大化的同时提高了频谱利用率. 相似文献
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ZHANG Pei-ling ;ZHANG Hong-xin ;LIU Hong-da ;ZHANG Yu-jing ;HE Peng-fei ;PANG Xue-li 《中国邮电高校学报(英文版)》2014,21(5):24-30
Particle filtering (PF) algorithm has the powerful potential for coping with difficult non-linear and non-Gaussian problems. Aiming at non-linear, non-Gaussian and time-varying characteristics of power line channel, a time-varying channel estimation scheme combined PF algorithm with decision feedback method is proposed. In the proposed scheme, firstly the indoor power line channel is measured using the pseudo-noise (PN) correlation method, and a first-order dynamic autoregressive (AR) model is set up to describe the measured channel, then, the channel states are estimated dynamically from the received signals by exploiting the proposed scheme. Meanwhile, due to the complex noise distribution of power line channel, the performance of channel estimation based on the proposed scheme under the Middleton class A impulsive noise environment is analyzed. Comparisons are made with the channel estimation scheme respectively based on least square (LS), Kalman filtering (KF) and the proposed algorithm. Simulation indicates that PF algorithm dealing with this power line channel estimation difficult non-linear and non-Gaussian problems performance is superior to those of LS and KF respectively, so the proposed scheme achieves higher estimation accuracy. Therefore, it is confirmed that PF algorithm has its own unique advantage for power line channel estimation. 相似文献
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研究了DF多跳OFDM通信系统的功率分配优化.在总发射功率受限的条件下,提出了一种双向优化功率分配算法(D-OPA):先优化单个子载波上各中继节点的功率分配,使该子载波上的信道容量最大;再优化各个子载波间的功率分配,使单跳的信道容量最大,从而最大化系统的信道容量.仿真结果表明:提出的算法与自适应功率分配算法、平均功率分配算法相比,信道容量明显提高. 相似文献
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Kin-Kwong Leung Chi Wan Sung 《Networking, IEEE/ACM Transactions on》2006,14(3):470-478
We propose an opportunistic power control algorithm, which exploits channel fluctuation in order to maximize system throughput. The basic idea is that it instructs a transmitter to increase its power when the channel is good and to decrease its power when the channel is bad. The transmission rate is adjusted according to the received signal-to-interference ratio. The proposed algorithm is distributed and can be applied to systems in which the transmitters are connected to different receivers. We prove that the algorithm always converge to a unique fixed point and thus is stable. Simulation results show that a tremendous increase in system capacity can be achieved, when compared with other power control algorithms. Furthermore, the algorithm works well for nonreal-time terminals when other real-time terminals employ the target-tracking power control. It can also be extended to cases where maximum power constraint is imposed and soft handoff is executed. 相似文献
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针对OFDM系统中难以实时获取时变信道统计信息的问题,提出了一种基于期望最大化(EM, expectation maximization)迭代的多符号联合信道估计和数据检测算法。为了获取合适的迭代初始值,利用梳状导频的信息,设计了基于最小二乘算法的低复杂度的初始化方案。通过分析算法中的信道统计量与信噪比的关系,提出了忽略信道自相关矩阵的简化算法,避免了获取信道统计信息的操作。仿真结果表明,提出的算法对信道的功率延迟分布和多普勒功率谱等统计信息不敏感,在未知信道多普勒功率谱的条件下,仍然具有较低的估计误差和误码率。 相似文献
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针对反射、散射影响下的非对称无线协作通信网络,提出了一种时变功率分配(Time Variant Power Allocation, TVPA)算法。根据无线协作网络中,各节点之间信道条件实时变化且不对称的特点,在信号传输过程中对信源节点和中继节点的发送信号功率进行优化分配。借助信道编码定理,将系统错误概率最小的非凸优化问题转化为最大化系统容量的凸优化问题来解。与固定功率分配(Fixed Power Allocation, FXPA)算法和平均功率分配(Average Power Allocation, AVPA)算法相比,该算法能充分利用无线信道的时变特性,重新分配功率以降低系统错误概率。在多种网络模型中的仿真结果表明,准静态瑞利衰落信道下,相比于FXPA算法,TVPA算法可获得多达5.5dB的比特错误概率性能增益。随着网络质量的进一步改善,该性能优势也逐步增大。 相似文献
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Berggren F. Jantti R. Seong-Lyun Kim 《Vehicular Technology, IEEE Transactions on》2001,50(6):1604-1612
The distributed constrained power control algorithm (DCPC) (Grandhi et al. 1995) has become one of the most widely accepted quality-based power control algorithms by the academic community. The DCPC has a property that the power may reach the maximum level when a user is experiencing degradation of channel quality. Unfortunately, using maximum transmitter power may not lead to sufficient improvement of channel quality and will thereto generate severe interference, affecting other users. This undesirable phenomenon happens more often when the system is congested. In this paper, we revisit and generalize the DCPC algorithm in order not to necessarily utilize the maximum power when the channel quality is poor. Under poor quality conditions, rather than combating the interference by maximizing power, we propose the concept of reducing the powers and temporarily removing users from the channel. We show that the energy consumption can be reduced through our generalized algorithm and we prove its convergence properties. Because of the decreased interference power, the capacity of the system is expected to increase. To validate this, we made computational experiments suggesting that the proposed algorithm can support more users in a congested system as compared to the previously suggested distributed removal algorithm gradual removals restricted (GRR)-DCPC (Andersin et al. 1996) 相似文献