Parametric Estimation of Load for Air Force Datacenters

The Office of Management and Budget (OMB) has tasked Federal agencies to develop a Data Center Consolidation Plan. Effective planning requires a repeatable method to effectively and efficiently size Air Force Base-level data centers. Review of commercial literature on data center design found emphasis in power efficiency, thermal modeling and cooling, and network speed and availability. The topic of sizing data center processing capacity seems undeveloped. This thesis provides a better, pedigreed solution to the data center sizing problem. By analogy, Erlang\u27s formulae for the probability of blocking and queuing should be applicable to cumulative CPU utilization in a data center. Using survey data collected by 38th Engineering Squadron, a simulation is built and correlation between the observed survey measurements and simulation measurements, and the Erlang, Gamma, and Gaussian-Normal distributions is found. For a sample dataset of 70 servers over 14 hours of observation and a supposed .99999 requirement for traffic to be passed or otherwise unimpeded, Erlang distribution predicts 10 CPU cores are required, Gamma distribution predicts 10 CPU cores are required, Gaussian-Normal distribution predicts 9 CPU cores are required, Erlang B formulae predicts 14 CPU cores are required, and Erlang C formulae predicts 15 CPU cores are required

An engineering approximation for the mean waiting time in the M/H2b/s queue

Although the exact solution for the mean waiting time in the M/H2/s queue exists, it requires advanced programming skills and processing capacity. In most engineering problems the offered traffic and its features are known with a certain degree of uncertainty (e.g. traffic is predicted, traffic is not clearly Poisson, etc). In such environments where perfect accuracy is not required, approximations are often used to estimate the performance. For engineering applications, the easiness to compute the estimate is a key factor. The contribution of this paper is a new closed formula to estimate the mean waiting time in the M/H2 b/s queue. The formula is easy to compute and accurate. In contrast with the already existing approximations, the one presented here keeps its validity for mediumhigh coefficients of variation.Peer Reviewe

Kuyruk teorisi : Web of Science indeksinde yayinlanan akademik makalelerin bibliyometrik haritasi

This study aims to determine the articles that are most concerned with the subject of queuing theory in the world, most cited studies, the scientific meetings that related to the topic and the most used keywords based on Web of Science (WOS) bibliographic database. The study is intended a bibliometric mapping and analysis of academic papers that carried out in the field of queuing theory in the international area. The search that made on WOS, includes between 1990 and 2015 November. According to the initial screening result on WOS, it has seen that a total of 59 studies were published since 1990 with the topic of "queuing theory" in social sciences and in operations research indexes. Then these studies were analyzed.peer-reviewe

Performance analysis of cellular networks.

Thesis (Ph.D.)-University of Natal, Durban, 2000.Performance analysis in cellular networks is the determination of customer orientated grade-of-service parameters, such as call blocking and dropping probabilities, using the methods of stochastic theory. This stochastic theory analysis is built on certain assumptions regarding the arrival and service processes of user-offered calls in a network. In the past, cellular networks were analysed using the classical assumptions, Poisson call arrivals and negative exponential channel holding times, borrowed from earlier fixed network analysis. However, cellular networks are markedly different from fixed networks, in that, they afford the user a unique opportunity: the ability to communicate while on the move. User mobility and various other cellular network characteristics, such as customer-billing, cell· layout and hand·off mechanisms, generally invalidate the use of Poisson arrivals and negative exponential holding times. Recent measurements on live networks substantiate this view. Consequently, over the past few years, there has been a noticeable shift towards using more generalised arrival and service distributions in the performance analysis of cellular networks. However, two shortcomings with the resulting models are that they suffer from state space explosion and / or they represent hand off traffic as a state dependent mean arrival rate (thus ignoring the higher moments of the hand-off arrival process). This thesis's contribution to cellular network analysis is a moment-based approach that avoids full state space description but ensures that the hand-off arrival process is modelled beyond the first moment. The thesis considers a performance analysis model that is based on Poisson new call arrivals, generalised hand-off call arrivals and a variety of channel holding times. The thesis shows that the performance analysis of a cellular network may be loosely decomposed into three parts, a generic cell traffic characterising model, a generic cell traffic blocking model and a quality of service evaluation model. The cell traffic characterising model is employed to determine the mean and variance of hand-off traffic offered by a cell to its neighbour. The cell traffic-blocking model is used to detennine the blocking experienced by the various traffic streams offered to each cell. The quality of service evaluation part is essentially afued-point iteration of the cell traffic characterising and cell traffic blocking parts to determine customer orientated grade-of-service parameters such as blocking and dropping probabilities. The thesis also presents detailed mathematical models for user mobility modelling. Finally, the thesis provides extensive results to validate the proposed analysis and to illustrate the accuracy of the proposed analysis when compared to existing methods

Queueing Networks for Vertical Handover

PhDIt is widely expected that next-generation wireless communication systems will be heterogeneous, integrating a wide variety of wireless access networks. Of particular interest recently is a mix of cellular networks (GSM/GPRS and WCDMA) and wireless local area networks (WLANs) to provide complementary features in terms of coverage, capacity and mobility support. If cellular/ WLAN interworking is to be the basis for a heterogeneous network then the analysis of complex handover traffic rates in the system (especially vertical handover) is one of the most essential issues to be considered. This thesis describes the application of queueing-network theory to the modelling of this heterogeneous wireless overlay system. A network of queues (or queueing network) is a powerful mathematical tool in the performance evaluation of many large-scale engineering systems. It has been used in the modelling of hierarchically structured cellular wireless networks with much success, including queueing network modelling in the study of cellular/ WLAN interworking systems. In the process of queueing network modelling, obtaining the network topology of a system is usually the first step in the construction of a good model, but this topology analysis has never before been used in the handover traffic study in heterogeneous overlay wireless networks. In this thesis, a new topology scheme to facilitate the analysis of handover traffic is proposed. The structural similarity between hierarchical cellular structure and heterogeneous wireless overlay networks is also compared. By replacing the microcells with WLANs in a hierarchical structure, the interworking system is modelled as an open network of Erlang loss systems and with the new topology, the performance measures of blocking probabilities and dropping probabilities can be determined. Both homogeneous and non-homogeneous traffic have been considered, circuit switched and packet-switched. Example scenarios have been used to validate the models, the numerical results showing clear agreement with the known validation scenarios

Using Actors to Implement Sequential Simulations

This thesis investigates using an approach based on the Actors paradigm for implementing a discrete event simulation system and comparing the results with more traditional approaches. The goal of this work is to determine if using Actors for sequential programming is viable. If Actors are viable for this type of programming, then it follows that they would be usable for general programming. One potential advantage of using Actors instead of traditional paradigms for general programming would be the elimination of a distinction between designing for a sequential environment and a concurrent/distributed one. Using Actors for general programming may also allow for a single implementation that can be deployed on both single core and multiple core systems. Most of the existing discussions about the Actors model focus on its strengths in distributed environments and its ability to scale with the amount of available computing resources. The chosen system for implementation is intentionally sequential to allow for examination of the behaviour of existing Actors implementations where managing concurrency complexity is not the primary task. Multiple implementations of the simulation system were built using different languages (C++, Erlang, and Java) and different paradigms, including traditional ones and Actors. These different implementations were compared quantitatively, based on their execution time, memory usage, and code complexity. The analysis of these comparisons indicates that for certain existing development environments, Erlang/OTP, following the Actors paradigm, produces a comparable or better implementation than traditional paradigms. Further research is suggested to solidify the validity of the results presented in this research and to extend their applicability

Application of advanced on-board processing concepts to future satellite communications systems

An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development

Advanced data management system analysis techniques study

The state of the art of system analysis is reviewed, emphasizing data management. Analytic, hardware, and software techniques are described