Antenna location design for generalized distributed antenna systems

A squared distance criterion for antenna location design in generalized distributed antenna systems (GDAS) is proposed to maximize the cell averaged ergodic capacity. The criterion requires the antenna port locations minimize the expectation of the squared distance between a randomly distributed user and the nearest antenna port. This is equivalent to codebook design in vector quantization. For uniform user distribution, we can easily derive analytical expressions for antenna locations. For more general user distribution, we can obtain numerical results using the codebook design algorithm. Applying the proposed criterion to circular-layout GDAS with uniform user distribution and linear cell with non-uniform user distribution, we achieve near optimal performance.     

A fully distributed location registration strategy for universalpersonal communication systems

The universal personal communication system (UPCS) is a system that enables anyone to communicate instantly with anyone else anywhere in the world. One of the crucial problems of such a system is locating hundreds of millions of moving portables in an efficient manner. The location registration strategy described is able to locate active portables automatically in the system with a small overhead in a distributed fashion. The system knows the exact position of an active portable in its service areas. The connection is set up by the system directly to its destination using the direct (shortest) path. The system capacity, efficiency, and inquiry time delay have been improved greatly compared to the leading existing techniques. It is shown that in the proposed system, the maximum database size is 0.51% and the database updating cost is 6.86% of that needed by a central database system under a specified scenario     

Switched-capacitor high-speed emulator for real-time fault location in electrical power systems

This research presents a discrete-time transmission line model based on the propagation of travelling waves. In this approach, the transmission line is emulated by means of many interconnected unit delay cells implemented with switched-capacitor (SC) circuits. The accuracy and limitations of this method is compared to existing transconductance–capacitor solutions and is evaluated in the frame of a novel power network fault location method based on the electromagnetic time-reversal principle. The impact of the non-ideal effects associated to analog CMOS SC circuits, such as amplifier finite gain, offset and switch charge injection is evaluated in the same context. A possible application of the model for the simulation of interconnected or multi-conductor lines is also discussed. After an AMS 0.35 µm process implementation, it is shown that the present method allows a fault location within 1% resolution and is a hundred times faster than nowadays digital solutions. This speed improvement allows a fault location within 160 ms, making thus real-time applications realistic.     

基于激光光斑定位的分布异构网络微小故障识别方法

受到分布异构网络信道窃听用户的影响,现有微小故障识别方法得到的故障指标过少,导致实际识别出的微小故障数量过少的问题,研究一种基于激光光斑定位的分布异构网络微小故障识别方法。以城市密集环境的微基站位置分布作为异构网络的分布形式,以计数异构网络点作为网络故障指标,联合独立散射参数,控制窃听用户的影响,采用激光光斑定位微小故障位置,设定故障定位过程为一个网络场景,采用时序特征不断匹配监测程序的参数,最终实现微小故障识别方法的构建。采用已知参数的实验元件,组装激光光斑装置,设定装置参数后,分别使用文献16中的故障识别方法、文献8中的故障识别方法、传统故障识别方法以及文中设计的故障识别方法进行实验,结果表明:文中设计的故障识别方法识别微小故障数量最多。     

A tutorial on fault tolerance issues with applications in distributed systems

Fault tolerance is the ability of a system to perform its function reliably in the presence of faulty hardware or software components. For a system to have this property, many separate issues are involved: fault confinement, fault detection, fault masking, retry, diagnosis, reconfiguration, recovery, restart, repair, and reintegration. These issues are discussed, and are applied to two well-known fault tolerance distributed systems.     

Line fault prediction and location in echo cancelling data transmission systems

Theoretical and practical results are presented which show that the tap coefficients of an echo cancelling modem can be used as an aid to line fault prediction and location. It is indicated that in some cases it is possible to identify a line fault before the transmission performance is seriously impaired.     

Neuristor analysis techniques for nonlinear distributed electronic systems

Neuristor propagation analysis techniques apply to a wide variety of nonlinear distributed electronic devices and wave propagation phenomena. This paper brings together and reviews these techniques. A specific example, the superconductive tunnel junction stripline, is modeled by a distributed equivalent circuit described by nonlinear parabolic partial differential equations. The neuristor pulse propagates at constant velocity with a fixed waveshape; mathematically, this reduces the partial differential equations to ordinary differential equations which are solved by phase-plane topology analysis. Poincaré's index rule and Bendixson's negative criterion prescribe the pulse velocity and waveform. Analytical results agree with experiment. Pulse waveform stability is studied using eigenfunction expansion of the perturbation equations and Lyapunov theory, but complete results are not obtained. Lyapunov theory provides estimates of excitation thresholds for launching a neuristor pulse, which are consistent with experiment. Determining the nature of pulse interactions may for some systems be accomplished using the Bäcklund transformation or perturbation series techniques, but generally requires complete computer solution of the dynamical equations.     

Capacity analysis in CDMA distributed antenna systems

In this letter, the effect of maximal ratio combining (MRC)-based macrodiversity on the reverse-link and forward-link capacity in code division multiple access (CDMA)-distributed antenna systems is analyzed. The concept of virtual cell is illustrated, and the analytical outage probability expressions are derived. The present investigation shows that on the reverse link, the interference can be suppressed greatly with macrodiversity, which leads to a significant increase in capacity. However, on the forward-link, it is proven that if simulcasting is used in CDMA-distributed antenna systems, the forward-link capacity cannot increase with macrodiversity whatever power allocation scheme is adopted. Based on the analysis of the cause of capacity loss, a new transmission scheme is further presented and the optimal power allocation scheme is derived. It is shown that, in this case, the forward-link capacity increases rapidly with the number of involved distributed antennas.     

分布式天线系统中的下行容量分析

针对分布式天线系统(DAS)的下行容量问题展开研究。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,基于该信道模型,分别对各态历经容量和中断容量进行了分析。考虑到小区内移动台的分布特点,在选择分集传输策略下,推导了各态历经容量和中断容量的近似解析表达式。仿真结果表明,所推导的2个近似解析表达式均能准确地评估分布式天线系统的系统性能。     

A distributed architecture for online power systems security analysis

Phenomena that can compromise power systems operation need to be carefully analyzed in order to evaluate their impact on the security and reliability levels of the electrical networks. The real-time assessment of the system's security and reliability levels, especially under unforeseen contingencies, is known as online power system security analysis. For complex networks this process requires large computational efforts whereas computation times should be less than a few minutes for the information to be useful. To address this problem a distributed architecture based on the Web is proposed. The architecture integrates a network of remotely controlled units distributed in the most critical sections of the electrical network for fields data acquisition and safety check violations, a distributed solution engine for the online analysis of the system security, and a Web-based interface for graphical synoptic and reporting development. The results obtained from an intensive experimentation demonstrate the validity of the architecture and stimulate the enhancement of the solution engine through the use of a computational grid able to dynamically acquire the needed resources.     

Fault management: analysis of fault location algorithm in optical network

cessible when solving the multifailure location problem. For multifailures, the proposed mechanism using time-stamps is more efficient in locating the fault and decreasing computational complexity.     

分布式MIMO系统小区平均遍历容量分析

针对分布式MIMO系统的圆形小区平均遍历容量展开研究.文章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,对分布式天线采用覆盖式（BT）传输策略,并在高信噪比条件下,导出给定移动台位置时,区上、下行点对点链路遍历容量表达式.最后,考虑移动台在小区内任意分布特点,进一步推导出小区平均遍历容量闭合近似表达式.仿真结果表明,所推导的近似表达式可很好的反应系统的实际性能.导的近似表达式可很好的反应系统的实际性能.     

Adaptive minimum bit feedback for sum-rate analysis in multi-user distributed antenna systems

The paper mainly studies the sum-rate performance of limited feedback (LFB) block-diagonalization (BD) in multi-user distributed antenna system (DAS). As the channel state information (CSI) fed back to base station (BS) is limited, multi-user interference (MUI) is caused inevitably because of the quantization error. Considering the influence of the MUI to the capacity of DAS, we propose a parameter of effective sum-rate ratio (ESRR) to denote the capacity offset under the condition of the BS can get perfect CSI and limited CSI first, then we confirm that the approximated ESRR is very close to actual ESRR got through simulations. After that, based on the approximated ESRR, an adaptive minimum bit feedback scheme which can effectively reduce the overhead of feedback channel and the complexity of the system is proposed. Simulation results show the effectiveness of the proposed scheme.     

A distributed location system for the active office

Distributed systems for locating people and equipment will be at the heart of tomorrow's active offices. Computer and communications systems continue to proliferate in the office and home. Systems are varied and complex, involving wireless networks and mobile computers. However, systems are underused because the choices of control mechanisms and application interfaces are too diverse. It is therefore pertinent to consider which mechanisms might allow the user to manipulate systems in simple and ubiquitous ways, and how computers can be made more aware of the facilities in their surroundings. Knowledge of the location of people and equipment within an organization is such a mechanism. Annotating a resource database with location information allows location-based heuristics for control and interaction to be constructed. This approach is particularly attractive because location techniques can be devised that are physically unobtrusive and do not rely on explicit user action. The article describes the technology of a system for locating people and equipment, and the design of a distributed system service supporting access to that information. The application interfaces made possible by or that benefit from this facility are presented     

双分布孔径红外系统的协同定位与精度分析

针对城市防空背景下利用两个分布孔径红外系统(DAIRS)对目标进行测距的问题,从目标成像的角度,构建了双DAIRS协同定位模型,推导了定位误差公式。误差分析除了考虑目标投影点的测量误差外,还增加了红外告警单元标定不准确等原因造成的系统误差。当目标在不同传感器上依次成像时,通过对定位误差延续性的分析表明在忽略视场限制的情况下,可以用其中的一个配对组来对处于不同视场交叠区的目标进行误差分析。最后,仿真分析了影响目标定位的主要因素,结果表明:减少组成DAIRS传感器数目对定位精度影响较少,该方面可以在一定程度上降低系统的高成本,另外当两个DAIRS之间的距离增加1/3时,定位误差可以降低一半。     

分布式天线系统中的系统下行误符号率分析

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,对分布式天线采用覆盖式（BT）传输策略,推导出给定移动台位置的小区下行点对点链路误符号率表达式.并在高信噪比条件下,通过给出移动台在小区的任意分布图,推导出小区下行平均误符号率的近似闭合表达式.仿真结果表明,所推导的近似表达式可很好地反应系统的实际性能.     

分布式天线系统中的系统下行误符号率分析

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,对分布式天线采用覆盖式(BT)传输策略,推导出给定移动台位置的小区下行点对点链路误符号率表达式。并在高信噪比条件下,通过给出移动台在小区的任意分布图,推导出小区下行平均误符号率的近似闭合表达式。仿真结果表明,所推导的近似表达式可很好地反应系统的实际性能。     

Three-step impedance criterion for small-signal stability analysis in two-stage DC distributed power systems

Small-signal stability analysis methods based on an impedance criterion originate from the minor loop gain method and are gradually utilized in two-stage DC distributed power systems. In this paper, we conclude that the impedance criterion directly dependent on output impedance Z/sub o/(s) of the source subsystem and input impedance Z/sub i/(s) of the load subsystem is possible but gives an incorrect stability analysis for systems with a regulated source subsystem. Through introducing a mapped pure impedance of the load subsystems and the preliminary system, we develop a general three-step impedance criterion, with which a correct small-signal stability analysis can be guaranteed, regardless of the type of source subsystem. Furthermore, we introduce the application of the three-step impedance criterion in two small-signal stability analysis cases and utilize it in an example system to predict the stability shift process arising from the variation on the load resistance and input voltage value.     

Capacity analysis for distributed antenna systems using cooperative transmission schemes in fading channels

Wireless systems equipped with distributed antennas can provide enhanced data throughput as well as improved signal quality when appropriate cooperative transmission schemes among antennas are employed. In this paper, the performance of distributed antenna systems (DAS) under the influence of Rayleigh fading and log-normal shadowing effects is investigated for different cooperation strategies, and corresponding statistical distributions for both the signal-to-interference ratio (SIR) and the capacity are presented. Specifically, the ergodic capacity per remote antenna (RA) is determined when n RAs cooperatively transmit the desired signal to the target receiver, which is compared with the non-cooperative single-antenna transmission (SAT) case. Using the results, a preferable mode of operation for given geographic locations of the receiver is determined. We further propose to perform an adaptive operation between the cooperative and non-cooperative modes under the capacity maximization criteria, and quantify exact amounts of capacity gain over individual transmission modes.     

10 kV配电线路单相接地故障分析与故障查找

文章分析了10 kV配电网频发单相接地故障以及其带来的危害,造成了大量的生产设备损坏和变电设备的损坏,加剧了线损程度。由此,亟需要找到查找故障的解决方法,分析原因,寻找解决故障的防范与处理措施,保障能够高效完成10 kV配电线路单相接地故障,提高其查找效率。