共查询到19条相似文献,搜索用时 671 毫秒
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针对非理想定时同步对协作多点传输的负面影响,提出了多模协作多点传输算法。通过推导协作波束成形模式和联合处理模式在非理想定时同步条件下的平均可达速率,得到模式选择变量和模式选择门限。在多模协作多点传输算法中,用户首先对定时同步误差进行估计,并计算其模式选择变量和模式选择门限。然后用户选择协作多点传输的下行传输模式,并将其选择结果反馈给协作基站。最后,根据各用户的反馈,协作基站以最大化平均可达传输速率为准则,自适应地在协作波束成形模式和联合处理模式之间切换。仿真结果表明多模协作多点传输算法在定时同步误差较小时,采用联合处理模式,以保持空间复用增益,在定时同步误差较大时,采用协作波束成形模式,以避免用户间的额外干扰。因此,在非理想定时同步误差条件下,多模协作多点传输算法比仅采用协作波束成形模式或联合处理模式的传统协作多点传输算法具有更好的性能。 相似文献
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本文主要研究了基于最小化均方误差和准则的MIMO放大转发双向中继信道中的波束成形向量(矩阵)的设计.我们分别在集中式与分布式两种应用环境中提出了一套解决方案.在集中式方案中,多个中继之间完全协作,因此将多个单天线中继等效成一个多天线的中继节点,设计了基于所有中继天线的总功率控制的波束成形向量(矩阵).在分布式方案中,中继节点之间无协作,分别设计了基于所有中继总功率控制波束成形向量(矩阵)和基于单个中继功率控制的波束成形向量(矩阵).仿真表明,通过波束成形设计,可以显著提高通信节点平均误码率.由于中继节点之间的完全协作,集中式方案要优于分布式方案.但是,由于中继结构简单,分布式方案更易于在实践中应用. 相似文献
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针对无人机(UAV)辅助的卫星通信系统下行链路,该文研究了基于多天线波束成形和协作非正交多址(NOMA)技术相结合的多用户传输系统。首先,在UAV采用多天线和NOMA技术服务多个用户的情况下,基于用户平均信干噪比最大化准则,提出一种利用角度信息的波束成形方案。其次,在卫星-UAV链路服从相关阴影莱斯分布,而UAV-地面用户链路服从Nakagami-m分布的条件下,推导出系统的中断概率闭合表达式。然后,为了进一步分析系统性能,还推导了高信噪比条件下系统的中断概率近似表达式。最后,计算机仿真验证了理论分析的正确性和所提方案的优越性。 相似文献
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本文基于OFDM调制系统,提出一种应用于宽带多天线场景下的发射端频域波束成形算法.首先仿真验证传统的窄带波束成形算法应用于宽带通信系统时,由于频率不匹配而造成的波束方向图失配,从而导致通信系统性能下降的问题.然后从发射端的角度考量,以预补偿的方式对OFDM调制的星座图映射之后,IFFT之前的频域信号进行宽带波束成形处理,仿真了在莱斯信道环境下的系统模型,并以误码率为衡量标准对提出的算法进行性能评估.结果表明,发射端应用频域宽带波束成形算法能够有效的降低接收端的误码率,改善通信系统性能. 相似文献
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分布式无线Ad Hoc传感器网络中的合作式波束形成的性能分析是建立在随机阵理论和移动通信波束形成的基础上的。在分布式Ad Hoc传感器网络中,每个传感器节点有一个全向天线,且在簇中的节点传输同一信号,使信号在远区场的目标方向上叠加。波束的方向的随机性是由无线Ad Hoc网络结构决定的。介绍了随机阵理论和移动通信波束形成,接着介绍了系统模型,分析了波束的方向特性,着重讨论了平均方向性增益,推导出平均方向性增益的近似公式。 相似文献
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Ahmed Mohammed F. A. Vorobyov Sergiy A. 《Wireless Communications, IEEE Transactions on》2009,8(2):638-643
Collaborative beamforming has been recently introduced in the context of wireless sensor networks (WSNs) to increase the transmission range of individual sensor nodes. The challenge in using collaborative beamforming in WSNs is the uncertainty regarding the sensor node locations. However, the actual sensor node spatial distribution can be modeled by a properly selected probability density function (pdf). In this paper, we model the spatial distribution of sensor nodes in a cluster of WSN using Gaussian pdf. Gaussian pdf is more suitable in many WSN applications than, for example, uniform pdf which is commonly used for flat ad hoc networks. The average beampattern and its characteristics, the distribution of the beampattern level in the sidelobe region, and the distribution of the maximum sidelobe peak are derived using the theory of random arrays. We show that both the uniform and Gaussian sensor node deployments behave qualitatively in a similar way with respect to the beamwidths and sidelobe levels, while the Gaussian deployment gives wider mainlobe and has lower chance of large sidelobes. 相似文献
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Ochiai H. Mitran P. Poor H.V. Tarokh V. 《Signal Processing, IEEE Transactions on》2005,53(11):4110-4124
The performance of collaborative beamforming is analyzed using the theory of random arrays. The statistical average and distribution of the beampattern of randomly generated phased arrays is derived in the framework of wireless ad hoc sensor networks. Each sensor node is assumed to have a single isotropic antenna and nodes in the cluster collaboratively transmit the signal such that the signal in the target direction is coherently added in the far-field region. It is shown that with N sensor nodes uniformly distributed over a disk, the directivity can approach N, provided that the nodes are located sparsely enough. The distribution of the maximum sidelobe peak is also studied. With the application to ad hoc networks in mind, two scenarios (closed-loop and open-loop) are considered. Associated with these scenarios, the effects of phase jitter and location estimation errors on the average beampattern are also analyzed. 相似文献
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针对Distance Vector-Hop (DV-Hop) 定位算法存在较大定位误差的问题,该文提出了一种基于误差距离加权与跳段算法选择的遗传优化DV-Hop定位算法,即WSGDV-Hop定位算法。改进算法用基于误差与距离的权值处理锚节点的平均每跳距离;根据判断的位置关系选择适合的跳段距离计算方法;用改进的遗传算法优化未知节点坐标。仿真结果表明,WSGDV-Hop定位算法的性能明显优于Distance Vector-Hop (DV-Hop) 定位算法,减小了节点定位误差、提高了算法定位精度。 相似文献
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Da Wang Chen Chen Lin Bai Jianhua He Ye Jin Ying Li 《Wireless Communications and Mobile Computing》2014,14(15):1484-1499
With careful calculation of signal forwarding weights, relay nodes can be used to work collaboratively to enhance downlink transmission performance by forming a virtual multiple‐input multiple‐output beamforming system. Although collaborative relay beamforming schemes for single user have been widely investigated for cellular systems in previous literatures, there are few studies on the relay beamforming for multiusers. In this paper, we study the collaborative downlink signal transmission with multiple amplify‐and‐forward relay nodes for multiusers in cellular systems. We propose two new algorithms to determine the beamforming weights with the same objective of minimizing power consumption of the relay nodes. In the first algorithm, we aim to guarantee the received signal‐to‐noise ratio at multiusers for the relay beamforming with orthogonal channels. We prove that the solution obtained by a semidefinite relaxation technology is optimal. In the second algorithm, we propose an iterative algorithm that jointly selects the base station antennas and optimizes the relay beamforming weights to reach the target signal‐to‐interference‐and‐noise ratio at multiusers with nonorthogonal channels. Numerical results validate our theoretical analysis and demonstrate that the proposed optimal schemes can effectively reduce the relay power consumption compared with several other beamforming approaches. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Least-Square Collaborative Beamforming Linear Array for Steering Capability in Green Wireless Sensor Networks 下载免费PDF全文
This paper presents a collaborative beamforming (CB) technique to organize the sensor node's location in a linear array for green wireless sensor network (WSN) applications. In this method, only selected clusters and active CB nodes are needed each time to perform CB in WSNs. The proposed least-square linear array (LSLA) manages to select nodes to perform as a linear antenna array (LAA), which is similar to and as outstanding as the conventional uniform linear array (ULA). The LSLA technique is also able to solve positioning error problems that exist in the random nodes deployment. The beampattern fluctuations have been analyzed due to the random positions of sensor nodes. Performances in terms of normalized power gains are given. It is demonstrated by a simulation that the proposed technique gives similar performances to the conventional ULA and at the same time exhibits lower complexity. 相似文献
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现有的向量加权稳健波束形成方法只有在指向误差较小的情况下才能有效估计目标的信号功率;矩阵加权波束形成方法在指向误差较大时,虽然可以估计目标的信号功率,但是它的系统实现复杂度与向量加权稳健波束形成方法相比较大。针对以上问题,该文提出基于半正定秩松弛(SDR)方法的稳健波束形成,该方法优化模型中的目标函数与Capon算法的目标函数相同,优化变量为加权向量的协方差矩阵,并约束方向图的主瓣幅度波动范围、旁瓣电平,协方差矩阵的秩为1。应用SDR方法求得加权向量的协方差矩阵,将该矩阵中的每一行(列)转化为加权向量,然后选择使得方向图主瓣与0 dB之间失真最大值最小的一个加权向量。该方法的系统实现复杂度与传统向量加权方法一致,对信号功率的估计性能与矩阵加权方法相当。仿真实验验证了该文方法可以得到理想的方向图形状,并且可以在大指向误差条件下有效估计信号功率。 相似文献