System Capacity Analysis and Antenna Placement Optimization for Downlink Transmission in Distributed Antenna Systems

System capacity and antenna placement play crucial roles in wireless communication systems, and they are of great value to network planning. In this paper, we are motivated to analyze the system capacity and optimize the antenna placement in distributed antenna systems. This paper establishes a composite channel model which takes path loss, lognormal shadowing and Rayleigh fading into consideration. To reduce the computational complexity, an approximate theoretical expression of system capacity is derived with selective transmission at the transmitter and maximal ratio combining at the receiver. An antenna placement optimization problem is formulated, and then a genetic algorithm (GA) based searching scheme is proposed to solve the proposed optimization problem. The computational complexity analysis indicates that the proposed GA-based searching scheme is computationally efficient in terms of both running time and storage space. Numerical results show that the approximate theoretical expression of system capacity can provide a very good approximation to the simulation results, and the proposed GA-based searching scheme for solving the antenna placement optimization problem can consistently offer a large capacity gain over other existing schemes.     

分布式天线系统中的系统下行中断概率分析

本文针对分布式天线系统的系统下行中断概率问题展开研究.文章首先建立了包含路径损耗、阴影衰落和瑞利衰落的复合信道模型.接着,在接收端采用最大比合并的方式接收信号,并运用矩生成函数推导出输出信噪比的概率密度函数.然后,对分布式天线采用选择传输策略,并分析出给定移动台位置时的中断概率的表达式.最后,考虑小区内移动台任意分布特...     

多蜂窝分布式系统下行链路性能分析

在多蜂窝分布式通信系统中,当移动用户在蜂窝内运动时,该文研究其下行链路的系统容量变化情况,并且推导出容量的闭合表达式。多数文献采用中心极限定理(CLT)把干扰加噪声项看作高斯白噪声来进行性能分析,其前提条件是干扰项足够多。当干扰项较少时,此种方法存在一定的误差。该文在放宽此限制条件的前提下,利用矩生成函数(MGF)对系统性能重新进行分析并且解决了存在重根时系统容量闭合表达式的推导问题。理论分析和数值仿真表明,此分析方法能更确切地体现信道衰落对干扰信号的影响,进而能更好地描述系统的性能。     

分布式天线系统中的系统上行中断概率分析

中断概率是无线通信系统的一个重要指标。该文针对分布式天线系统中的系统中断概率问题进行了研究。首先,建立了包含路径损耗、阴影衰落和瑞利衰落的复合信道模型;然后,在该信道模型下推导出给定移动台位置时的信噪比;接着,基于选择合并策略,分析出给定移动台位置时系统上行传输的中断概率表达式;最后,考虑到小区内移动台任意分布特点,文章给出系统上行中断概率闭合理论表达式。仿真结果表明,所提的系统上行中断概率理论表达式与仿真结果十分吻合。     

波束成形下DMIMO系统下行小区平均遍历容量分析

主要对波束成形下分布式MIMO系统下行小区平均遍历容量展开分析。首先建立了包含快衰落、阴影衰落和路径损耗的复合衰落信道模型。然后,在分布式基站功率受限条件下,推导各基站权重向量即最优波束;并基于ST-MRT传输策略,推导特定移动台位置条件下,小区下行点对点遍历容量表达式。最后,考虑移动台在小区内任意分布的特征,进一步推导出波束成形下小区平均遍历容量理论近似表达式。结果表明所推导的理论近似表达式可很好地反应系统的实际性能。     

室内分布式天线系统信道测量及容量分析

分布式天线系统通过在地理位置上分布式放置天线,增强了系统的覆盖性能,也提高了系统的分集增益和容量性能。通过自主搭建的信道测量平台,对室内分布式天线系统信道进行了测量,其中发端天线分布式放置,接收端天线集中放置,对数据分析表明,在不存在视距传输或者视距传输分量不明显的情况下,各发天线到收端的信道解相关特性良好,容量性能提高较大;反之则容量性能下降。系统容量与天线是否均匀放置也密切相关,天线均匀放置时,容量提高且分布更为均匀。     

On the Ergodic Capacity of Distributed MIMO Antenna Systems

We consider distributed multiple-input–multiple-output (MIMO) antenna systems, along with their certain generalizations. We show that distributed MIMO configuration can be mapped to a semicorrelated (one side correlated) Wishart model. For a given set of large-scale fading parameters, associated with the path loss and shadow fading, we derive exact and closed-form results for the marginal density of eigenvalues of \(\mathbf{H}^\dag \mathbf{H}\) (or \(\mathbf{H} \mathbf{H} ^\dag\)), where \(\mathbf{H}\) is the channel matrix. We also obtain exact and closed-form expressions for the ergodic channel capacity with the aid of Meijer G-function. The ergodic capacity of semicorrelated Rayleigh fading channel follows as a special case. All analytical results are validated by comparison with Monte-Carlo simulations.     

天线选择对分布式多入多出系统的容量影响研究

通过天线选择可以提高多输入多输出(MIMO)系统的容量,并能有效地降低MIMO系统的复杂度和射频成本.基于连续选择使MIMO系统容量增加最大的天线的方法,用矩阵及行列式运算导出了一种新的接收天线选择算法.将该算法用于分布式MIMO系统的容量研究,通过计算机仿真,结合Rice因子K及不同视距传播条件等因素对分布式MIMO系统上行信道容量的影响进行了研究.仿真结果在分布式无线通信组网及网络优化中具有指导意义.     

Downlink Capacity Analysis of Collaborative Crossed Timeslots in CDMA TDD Systems

Traffic asymmetry between uplink and downlink is expected to be a remarkable 3G characteristic in cellular mobile multimedia communications. CDMA system with TDD is a good solution to this traffic asymmetry. However, the level of traffic asymmetry may be significantly different from a cell to another cell. To tackle this problem and to support the traffic hot spot, crossed slots are examined. The use of crossed slots is restricted within a certain range of a cell by investigating the inter-cell interference and the maximum planned load factor. We examine the radius of inner zone and discuss the capacity of downlink crossed slots for various neighbor cell environments. Computational results show that the capacity increase in the target cell is outstanding by reducing the service range of neighbor cells. When all six neighbors reduce their service range by 20%, the capacity at target cell crossed slot is increased by 35%. Monte Carlo simulation is performed with large scale fading to verify the numerical analysis.

Downlink SINR Study in Multiuser Large Scale Antenna Systems

In this paper, the downlink signal-to-interference-plus-noise ratio (SINR) performance in multiuser large scale antenna systems with matched filter (MF) and regularized zero-forcing (RZF) precoding is investigated. The probability density function (PDF) for MF is derived and the distribution in high signal-to-noise ratio (SNR) regime is studied. Results indicate that the PDF of downlink SINR for MF converges to \(\mathcal F\) distribution when the interference is dominant over noise. For MF, the asymptotic SINR is just the reciprocal of the ratio of the number of users \(U\) to the number of transmit antennas \(N\) , and is irrelevant to the average transmit power when \(N\) and \(U\) grow with fixed ratio. However, when \(U\) is a large constant, the transmit power could be proportional to \(\ln N \big /N \) to maintain a specified quality of service, as a result of the large scale antenna system effect. In addition, the closed form of asymptotic SINR for RZF is derived by solving two mathematical expectations related to eigenvalues of large dimensional random matrices. Simulation results validate the derived PDF and analytical results.     

机舱内分布式MIMO系统信道容量分析

采用自主搭建的信道测量平台测得了机舱环境下分布式MIMO系统的信道冲击响应矩阵。根据实测的信道矩阵分别计算了4种具有不同收发天线数目的分布式MIMO系统的信道容量。为了便于比较,SISO系统的信道容量也通过实测数据进行了计算。计算结果表明：在机舱环境下,采用分布式MIMO系统和采用SISO系统相比能够显著提高系统信道容量,说明分布式MIMO系统可以充分满足未来机舱内无线通信高速率数据传输的需求。     

阵列天线在OFDM系统下行链路中的应用

正交频分多址(OFDM:orthogonal frequency division multiplexing)技术由于其在多径环境下克服码间干扰的固有特点,在移动通信中已得到广泛地应用。利用阵列天线上行链路信号到达角估计实时信息,计算OFDM系统下行链路阵列天线权重,将阵列天线应用于下行链路中,最后给出系统误码率性能的计算机仿真结果。     

ALOHA/TDM Systems with Multiple Downlink Capacity

The concept of a processing satellite with multiple slotted ALOHA uplinks to efficiently fill a TDM downlink is extended to include multiple downlinks. Throughput is derived for a general configuration withnALOHA uplinks andmTDM downlinks. An optimization procedure is described to select thenandmwhich maximize throughput for a given bandwidth constraint. The ALOHA/TDM system with multiple downlink capacity is found to be up to 32% more spectrum-efficient than the conventional slotted ALOHA system. The ALOHA/TDM system also has the potential for payload power and weight savings and decreased passive intermodulation problems.     

Outage Capacity Study of the Distributed MIMO System with Antenna Cooperation

This letter analyzes the outage capacity of the distributed multi-input multi-output (D-MIMO) systm with antenna cooperation over the Rayleigh-Log-normal fading channel. Firstly, an analytical expression of outage capacity is derived under the cooperative transmission scheme (CTS). Moreover, to optimize the system performance, an adaptive CTS (ACTS) is proposed, and a theoretical expression is derived to perform the ACTS. Simulation results are presented to verify the theoretical outcome.     

分布式天线系统在移动通信中的应用

移动通信在中国的发展势头未减,2G网络的优化以及3G网络的规划都对技术创新提出了更高的要求。分布式天线解决方案是当前和未来移动通信网络中无线资源管理的有效方式之一。介绍了分布式天线系统的种类和发展,探讨了分布式天线系统为移动通信运营商带来的好处。     

Joint User Scheduling and Antenna Selection in Distributed Massive MIMO Systems with Limited Backhaul Capacity

Massive MIMO systems offer a high spatial resolution that can drastically increase the spectral and/or energy efficiency by employing a large number of antennas at the base station（BS）.In a distributed massive MIMO system,the capacity of fiber backhaul that links base station and remote radio heads is usually limited,which becomes a bottleneck for realizing the potential performance gain of both downlink and uplink.To solve this problem,we propose a joint antenna selection and user scheduling which is able to achieve a large portion of the potential gain provided by the massive MIMO array with only limited backhaul capacity.Three sub-optimal iterative algorithms with the objective of sumrate maximization are proposed for the joint optimization of antenna selection and user scheduling,either based on greedy fashion or Frobenius-norm criteria.Convergence and complexity analysis are presented for the algorithms.The provided Monte Carlo simulations show that,one of our algorithms achieves a good tradeoff between complexity and performance and thus is especially fit for massive MIMO systems.     

分布式多天线技术研究

在基于多输入多输出-正交频分复用(MIMO-OFDM)技术的下一代宽频无线通信系统中,为了提高频谱利用率,一般采用同频组网,这就在小区边缘引入了同频干扰,影响了系统覆盖范围、容量以及边缘用户的切换体验。分布式多天线系统可以有效地解决上述问题,它通过拉远天线的距离,充分利用多输入多输出(MIMO)技术的空间分集和宏分集优势,通过集中式的预编码、用户调度、功率控制等策略较好地控制基站内不同小区间的干扰,尤其适合于增强数据热点地区的覆盖,减少用户的切换次数,提升小区边缘用户的服务质量。     

分布式OFDMA系统下行资源分配算法

针对正交频分复用（OFDM）分布式天线系统（DAS）的下行链路,在发送端采用最大比发送（MRT）并且单天线功率受限、所有发射天线的总功率受限,考虑用户最低速率要求时,丈中提出一种最大化和速率容量的次优资源分配策略。仿真结果表明,动态天线选择策略下DAS比集中式天线系统（CAS）获得更大的和速率容量,并且更容易达到最低速率的要求。     

The Downlink Capacity of Single-User SA-MIMO System

In this paper, a novel multiple antenna system framework, which combines smart antennas (SA) with multiple-input-multiple-output (MIMO) at the transmitter, is proposed. The downlink capacity of the single-user SA-MIMO wireless systems is investigated. The joint optimization problem corresponding to the capacity is deduced. After that, upper bounds of the capacity are given in general case and in the case of equal power allocation, respectively. Furthermore, in the case of equal power allocation and the same direction of departure from one transmit smart antenna to all antenna arrays at the receiver the closed-form expression of the capacity is obtained. Some numerical results are given to show that smart antennas can bring significant capacity gain for the MIMO systems due to the smart antennas gain, without additional spatial degrees of freedom, especially at high SNR with strong correlation among the MIMO channel links or at low SNR.     

Forward Link Performance Analysis in CDMA Distributed Antenna Systems with Imperfect Channel Estimation

1　Introduction　The Distributed Antenna (DA) system has been proposedas a promising antenna architecture for the future wirelesscommunication systems[1~10].　In the DA systems, with remote antennas, the presentcellular structure is removed and cells are not divided geo graphically, but according to the user needs. That is, ac cording to the channel estimates computed via pilot signals,the Processing Node (PN) continuously measures the chan nels between the mobiles and the remote ante…