共查询到18条相似文献,搜索用时 187 毫秒
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MIMO系统信道容量研究 总被引:2,自引:1,他引:2
针对单用户MIMO系统信道的容量特性展开研究。首先详细推导了无衰落信道下信道容量表达式,然后重点分析了瑞利衰落信道下,接收端已知信道状态信息,发射端已知信道状态分布时的容量特性。最后分别针对瑞利衰落信道下,采用发射分集、接收分集以及BLAST传输结构的系统容量进行仿真。仿真结果表明:给定发射功率,独立的瑞利衰落信道条件下,MIMO系统容量随最小天线数目的增加而线性增加,极大地提高了系统容量。 相似文献
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采用2维射线跟踪法分析了非视距室内环境中天线间隔、天线阵形对MIMO系统容量和互补累积分布函数(CCDF)的影响。结果表明随着天线间隔减小,MIMO系统容量降低。10%中断容量表明,天线间隔相同时,有独立同分布瑞利信道容量大于线性阵容量大于方阵容量或者圆形阵容量的关系。当天线间隔大于等于3 时,不同天线阵列阵形对容量影响非常小,此时i.i.d.瑞利信道理论容量几乎全部实现。当天线间隔小于等于1 时,天线阵列阵形对容量影响较大,矩形阵和圆形阵MIMO系统容量相差较小,但都显著小于线性阵列系统容量。在非视距的室内环境中,要实现最大的MIMO容量增益,设计天线阵列时应该对天线间隔和阵列阵形综合考虑。 相似文献
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基于天线选择的低秩信道MIMO系统容量研究 总被引:1,自引:0,他引:1
最近的研究表明,在衰落信道多天线MIMO系统的容量随发射天线数线性增加.而对于低散射环境,即使信号经历独立的衰落,信道秩的降低也会严重影响系统容量的增加.对于这种低秩环境,选择天线发射或接收可以有效地降低系统的成本.本文研究了天线选择对低秩信道MIMO系统容量的影响.仿真结果表明,对不同的信道条件,适当选择天线发射不仅可以增加信道容量,而且可以降低系统的复杂度和射频成本.适当选择天线接收,在不严重降低系统容量的前提下,也达到了降低系统成本的目的. 相似文献
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针对平坦相关瑞利衰落信道环境下的端到端大规模MIMO系统复杂度过高的问题,提出一种基于离散布谷鸟搜索的低复杂度双层分组天线选择算法。该算法首先基于天线信道相关性对大规模天线阵列进行分组处理,进而利用新型双层算法对分组的天线集合进行优化天线选择。其中,新型双层算法的第一层是每小组天线基于离散布谷鸟搜索的内部选择,第二层是对第一层选择的所有天线利用离散布谷鸟搜索进行最终的选择。提出的新型天线选择算法可有效降低大规模MIMO系统复杂度。仿真结果验证了在平坦相关瑞利衰落信道环境下,提出的天线选择算法能够以较低选择复杂度获得接近最优选择方法的容量性能和较优的BER性能。 相似文献
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Hyundong Shin Win M.Z. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(7):2976-2996
The potential benefits of multiple-antenna systems may be limited by two types of channel degradations-rank deficiency and spatial fading correlation of the channel. In this paper, we assess the effects of these degradations on the diversity performance of multiple-input multiple-output (MIMO) systems, with an emphasis on orthogonal space-time block codes (OSTBC), in terms of the symbol error probability (SEP), the effective fading figure (EFF), and the capacity at low signal-to-noise ratio (SNR). In particular, we consider a general family of MIMO channels known as double-scattering channels-i.e., Rayleigh product MIMO channels-which encompasses a variety of propagation environments from independent and identically distributed (i.i.d.) Rayleigh to degenerate keyhole or pinhole cases by embracing both rank-deficient and spatial correlation effects. It is shown that a MIMO system with transmit and receive antennas achieves the diversity of order in a double-scattering channel with effective scatterers. We also quantify the combined effect of the spatial correlation and the lack of scattering richness on the EFF and the low-SNR capacity in terms of the correlation figures of transmit, receive, and scatterer correlation matrices. We further show the monotonicity properties of these performance measures with respect to the strength of spatial correlation, characterized by the eigenvalue majorization relations of the correlation matrices. 相似文献
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A lower bound on achievable rate of MRT precoding in multicell multiuser massive MIMO networks with Rician flat fading
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Mohammad Kazemi Hassan Aghaeinia 《International Journal of Communication Systems》2016,29(18):2632-2649
A multicell multiuser massive multiple‐input‐multiple‐output (MIMO) network with Rician flat fading is considered. Given channel reciprocity, non‐orthogonal uplink channel training in conjunction with minimum mean square error channel estimation at the base stations are used to acquire channel state information. In the forward link, using maximal ratio transmission precoding, base stations send data to corresponding users. In this paper, first, a closed‐form expression for signal to interference and noise ratio and a lower bound on achievable rate are obtained for arbitrary number of base station antennas. Then, using random matrix theory, a simplified approximate expression for large number of base station antennas (i.e., massive MIMO scenario) are calculated. This simplified expression shows that in a multicell multiuser massive MIMO network with Rician flat fading, like Rayleigh fading, as the number of base station antennas goes to infinity, the effects of uncorrelated noise and intercell and intracell interferences tend to zero. The only factor limiting the performance of system is the correlated intercell interference, that is, pilot contamination, due to non‐orthogonality of channel training sequences in adjacent cells. Numerical results show that our obtained closed‐form expression is a good lower bound on sum‐rate for various system parameters. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Generally, the channel capacity of a MIMO system is closely related to its Channel Characteristic Matrix (CCM). In most current studies, the CCMs are formed by an independent identical distribution (i.i.d) model with Rayleigh or Rice distribution and nevertheless incomplete and inaccurate to describe a Broadband Dual-orthogonal Polarized MIMO Land Mobile Satellite (BDM-LMS) channel. In this paper, we build up the BDM-LMS channel model combining a 4-states broadband LMS channel model, time selective fading features, Channel Covariance Information (CCI) model and polarization correlation between antennas. Modeling steps of the channel model are introduced. The main emphasis is placed on the effects of the factors on the channel capacity in BDM-LMS system, such as antenna numbers, temporal correlations, terminal environments, elevation angles and polarization correlations between the DPAs. We provide simulation results to illustrate the effects of these factors through comparisons of the transmit rate, Ergodic Capacity and Outage Capacity. Moreover, the MIMO outage capacity advantages, indicating the benefits of MIMO compared with SISO systems under the same channel condition, are also studied under i.i.d and BDM-LMS channel. 相似文献
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Xudong Cheng Yejun He Li Zhang Jian Qiao 《International Journal of Communication Systems》2018,31(12)
In this paper, we use the multipolarized antennas in massive multiple‐input multiple‐output (MIMO) systems to decline the channel orthogonality and enhance the system performance. We propose 3 multipolarized massive MIMO system schemes according to antenna structures of 3 widely used massive MIMO systems and establish 3‐D geometrical channel models. Simulation results show that the multipolarized massive MIMO systems outperform the unipolarized massive MIMO systems in many situations. The multipolarized antennas would be the best choice for massive MIMO systems if the space efficiency and the miniaturization of equipments are of primary concern. 相似文献
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Hermosilla C. Feick R. Valenzuela R.A. Ahumada L. 《Wireless Communications, IEEE Transactions on》2009,8(5):2177-2181
MIMO systems are usually associated with high scattering isotropic propagation while the use of directive antennas is associated with free space conditions. We found outdoor-indoor channels to be in between these two extremes, in the sense that we observed directivity - and - MIMO gain, for the same ensemble of channels. Our observation is based on measurements with directive (8 dB) and dipole antennas. Median MIMO capacities were found to be about 80% of the ideal (Rayleigh i.i.d.), at 5 dB Signal to Noise Ratio (SNR), for both types of antennas. Using properly aimed directive antennas, the SNR was found on average to be 5.4 dB above that obtainable with dipoles, somewhat less than the 7 dB antenna gain difference. Thus, isotropic propagation, which would have negated directivity gains, cannot be justified in general. We empirically established that aiming for largest received power is the best array pointing strategy with directive antennas. Combining MIMO processing and angular search resulted on average in gains of 70% over the median capacities obtained with dipoles. Therefore it may in some cases be convenient to arrange subgroups of antennas for beamforming, and then process the thus reduced number of radio channels for MIMO gain. 相似文献
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Multiple-input multiple output (MIMO) communication architecture has recently emerged as a new paradigm for wireless communications in rich multipath environment, which has spectral efficiencies far beyond those offered by conventional techniques. The channel capacity of the MIMO architecture in independent Rayleigh channels scales linearly as the number of antennas. However, the correlation of a real-world wireless channel may result in a substantial degradation of the MIMO architecture performance. In this letter, we investigate the MIMO channel capacity in correlated channels using the exponential correlation matrix model. We prove that, for this model, an increase in correlation is equivalent to a decrease in signal-to-noise ratio (SNR). For example, r=0.7 is the same as 3-dB decrease in SNR 相似文献
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It is well known that multiple input multiple output (MIMO) systems offer the promise of achieving very high spectrum efficiencies (many tens of bit/s/Hz) in a mobile environment. The gains in MIMO capacity are sensitive to the type of channel encountered in the radio environment. To date most analytical work has concentrated on Rayleigh fading channels. Hence, in this letter we consider the capacity outage performance of MIMO systems in Ricean channels. Due to analytical complexity we concentrate on dual antenna systems (either two transmit or two receive antennas) and derive exact densities and distribution functions for the capacity. 相似文献