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1.
The system receives a stream of tasks which arrive according to some random processes. A new availability measure, random-request availability, is proposed. This stochastic model provides closed-form mathematical expressions which incorporate the 3 basic elements: random task arrivals; system state; and operational requirements of the system. An analytic model is derived and illustrated by numerical examples  相似文献   

2.
Some constructions and bounds for authentication codes   总被引:4,自引:0,他引:4  
We investigate authentication codes, using the model described by Simmons. We review and generalize bounds on the probability that an opponent can deceive the transmitter/receiver by means of impersonation or substitution. Also, we give several constructions for authentication codes that meet one or more of these bounds with equality. These constructions use combinatorial designs, such as transversal designs, group-divisible designs, and BIBDs (balanced incomplete block designs).  相似文献   

3.
光纤骨干通信网中,一条光纤的断裂会引起大量业务中断.因此,对于每一条工作光路可配置一条链路分离的保护光路.采用共享通路保护时光路连接的可用性计算是网络设计时的重要问题.现对共享通路保护方式下光路连接可用性的计算给出了推导过程和一种明显的计算公式.最后给出实例,通过与仿真结果的比较验证了计算方法的正确性.  相似文献   

4.
This is an expository paper which seeks to fill some gaps in the theory of the availability of a two-state system modelled by an alternating renewal process. A discussion of point availability and average availability complements the results of Baxter, J. appl. Prob.18, 227–235, 1981. This is followed by some remarks on equilibrium alternating renewal processes, the Haynes-Davis waiting-time theorem and the correlated alternating renewal process.  相似文献   

5.
The authors report on experiences in validating complex computer-system availability models. A validation process, the availability models, and the data-collection process are described. An iteration of the model validation process emphasizing discrepancies between observed system behavior from data and from the model assumptions is presented. Analysis of data from five sites revealed that interruption dependencies on a device and across devices within a system exist. Furthermore, the frequency of, dependencies between, and downtime of device interruptions constitute differentiating characteristics of the causes of device interruptions. Data on partially available machine states, nonexponentially distributed machine downtimes, and nonstationarity of the machine interruption process are included. Validating the model assumptions is essential to model interpretation. Model accuracy is assessed. Exponentially distributed times between interruptions on a device and exponentially distributed device downtimes are not significant with respect to average measures of availability. The benefits of and issues for availability-model validation are summarized  相似文献   

6.
Neural networks are employed to realize an availability model of the TMR hardware with fault-coverage and repair. The failure rate and repair rate of the system that satisfy a target pointwise availability are extracted from the weights of the neural network. The structure and results of the simulation algorithm are presented.  相似文献   

7.
A new technique for applying fault tolerance to modulus replication RNS computations by adding redundancy to the independent computational channels is introduced. This technique provides a low-overhead solution to fault tolerant large inner product computations  相似文献   

8.
New bounds are presented for the maximum accuracy with which parameters of signals imbedded in white noise can be estimated. The bounds are derived by comparing the estimation problem with related optimal detection problems. They are, with few exceptions, independent of the bias and include explicitly the dependence on the a priori interval. The new results are compared with previously known results.  相似文献   

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As computer and communication systems become more complex it becomes increasingly more difficult to analyze their hardware reliability, because simple models can fail to adequately-capture subtle but important features. This paper describes several ways the authors have addressed this problem for analyses based upon White's SURE theorem. They show: how reliability analysis based on SURE mathematics can attack very large problems by accepting recomputation in order to reduce memory usage; how such analysis can be parallelized both on multiprocessors and on networks of ordinary workstations, and obtain excellent performance gains by doing so; how the SURE theorem supports efficient Monte Carlo based estimation of reliability; and the advantages of the method. Empirical studies of large models solved using these methods show that they are effective in reducing the solution-time of large complex problems  相似文献   

11.
We present new exponential bounds for the Gaussian Q function (one- and two-dimensional) and its inverse, and for M-ary phase-shift-keying (MPSK), M-ary differential phase-shift-keying (MDPSK) error probabilities over additive white Gaussian noise channels. More precisely, the new bounds are in the form of the sum of exponential functions that, in the limit, approach the exact value. Then, a quite accurate and simple approximate expression given by the sum of two exponential functions is reported. The results are applied to the general problem of evaluating the average error probability in fading channels. Some examples of applications are also presented for the computation of the pairwise error probability of space-time codes and the average error probability of MPSK and MDPSK in fading channels.  相似文献   

12.
Telecommunication systems are large and complex, consisting of multiple intelligent modules in shelves, multiple shelves in frames, and multiple frames to compose a single network element. In the availability and performability analysis of such a complex system, combinatorial models are computationally efficient but have limited expressive power. State-based models are expressive but computationally complex. Furthermore, this complexity grows exponentially with the size of the model. This state-space explosion problem must be solved in order to model complex-systems using state-based models. The solution, in this paper, is to partition complex models into a hierarchy of submodels, to transform lower-level n-state, m-transition Markov reward models and stochastic reward nets into equivalent (with respect to their steady-state behavior) 2-state, 2-transition models, and then to back-substitute the equivalent submodels into the higher-level models. This paper also proposes a canonical form for the equivalent submodels. This technique is defined for availability models, where the state of the system is either up of down, and for performability models, where the state of the system may be up, down, or partially-up/partially-down. This paper also shows how this technique can be used to obtain common availability measures for telecommunication systems, and when to apply it to availability models and when to use it in performability models. For future work, it would be interesting to more tightly integrate this technique with modeling tools, perhaps coupled with a graphic front-end to facilitate the navigation of the model hierarchy.  相似文献   

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自相似过程的几种模型   总被引:3,自引:2,他引:3  
张强  许进 《通信学报》2001,22(2):106-112
本文综述了目前在自相似过程建模研究方面所获得的主要成果,分析了各自的优缺点,这对于自相似信号的处理具有一定的指导意义。  相似文献   

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17.
徐云学  龚书喜 《电波科学学报》2007,22(2):266-270,291
在分析物理光学法(PO)、等效电磁流法(MEC)、几何光学物理光学法(GOPO)等算法的基础上开发了基于MATLAB的电大尺寸目标RCS计算软件系统.应用MATLAB外部接口与FORTRAN语言混合编程提高了计算效率.最后利用该软件系统计算了典型目标和某大型舰艇的RCS,典型目标的RCS计算结果与测量值比较,吻合良好.某大型舰艇目标的RCS计算结果经分析,计算结果合理.  相似文献   

18.
电特大复杂目标电磁特性的高效精确并行计算   总被引:2,自引:0,他引:2  
在不同层间采用不同的并行方式来处理多层快速多极子中的平面波和转移矩阵后,并行算法的效率非常高.但当目标尺寸达到几百个电波长时,计算多极子中盒子的距离信息非常消耗计算资源,成为进一步提升并行多层快速多极子仿真能力的瓶颈.为此,提出了一种并行的递归相邻中心算法来高效处理盒子间距离信息.通过计算超过2,300万个未知数模拟的直径达到200个波长金属球的散射,检验了本文并行算法的精度和效率,充分说明本文方案消除了上述瓶颈极大提高了并行算法的仿真能力.为进一步证明算法的通用和高效,还计算了尺寸接近500个电波长的飞机模型电磁特性,这是目前国际上公开报道的用MLFMA所能求解的尺寸最大的问题.  相似文献   

19.
A new, infinite series representation for the error function is developed. It is especially suitable for computing erfc(x) for large x. For instance, for any x⩾4, the error function can be evaluated with a relative error less than 10-10 by using only eight terms. Similarly, the error function can be evaluated with a relative error less than 8×10-7 for any x⩾2 using just six terms. An analytical bound is derived to show that the total error due to series truncation and undersampling rapidly decreases as x increases. Comparisons with two other series are provided  相似文献   

20.
Evaluates various proposed VLSI models of computation. While there is a consensus on the appraisal of chip area, controversy remains with regard to computation time. Thus, the authors have analyzed in detail the propagation of signals on disperse lines. The results are expressed in terms of adimensional parameters characteristic of any given fabrication technology. The conclusion is that both current and projected silicon technologies fall within the realm of the capacitive model where a dispersive line can be replaced by a capacitance proportional to its length. Diffusion phenomena therefore appear to exceed the present VLSI horizon.  相似文献   

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