Cost minimization for unstable concurrent products in multi-stage production line using queueing analysis

This research and resulting contribution are results of Assumption University of Thailand. The university partially supports financially the publication.Purpose: The paper copes with the queueing theory for evaluating a muti-stage production line process with concurrent goods. The intention of this article is to evaluate the efficiency of products assembly in the production line. Design/Methodology/Approach: To elevate the efficiency of the assembly line it is required to control the performance of individual stations. The arrival process of concurrent products is piled up before flowing to each station. All experiments are based on queueing network analysis. Findings: The performance analysis for unstable concurrent sub-items in the production line is discussed. The proposed analysis is based on the improvement of the total sub-production time by lessening the queue time in each station. Practical implications: The collected data are number of workers, incoming and outgoing sub-products, throughput rate, and individual station processing time. The front loading place unpacks product items into concurrent sub-items by an operator and automatically sorts them by RFID tag or bar code identifiers. Experiments of the work based on simulation are compared and validated with results from real approximation. Originality/Value: It is an alternative improvement to increase the efficiency of the operation in each station with minimum costs.peer-reviewe

Maximum Likelihood Estimation of Closed Queueing Network Demands from Queue Length Data

Resource demand estimation is essential for the application of analyical models, such as queueing networks, to real-world systems. In this paper, we investigate maximum likelihood (ML) estimators for service demands in closed queueing networks with load-independent and load-dependent service times. Stemming from a characterization of necessary conditions for ML estimation, we propose new estimators that infer demands from queue-length measurements, which are inexpensive metrics to collect in real systems. One advantage of focusing on queue-length data compared to response times or utilizations is that confidence intervals can be rigorously derived from the equilibrium distribution of the queueing network model. Our estimators and their confidence intervals are validated against simulation and real system measurements for a multi-tier application

Performance improvements to the 802.11 wireless network medium access control sub-layer : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Computer Systems Engineering at Massey University

This thesis presents the outcome into the research and development of improvements to the 802.11 wireless networking medium access control (MAC) sublayer. The main products of the research are three types of improvement that increase the efficiency and throughput of the 802.11 protocol. Beginning with an overview of the original 802.11 physical layer and MAC sub-layer standard, the introductory chapters then cover the many supplements to the original standard (including a brief on the future 802.11n supplement). The current state of the 802.11 MAC sub-layer is presented along with an assessment of the realistic performance available from 802.11. Lastly, the motivations for improving the MAC sub-layer are explained along with a summary of existing research into this area. The main improvement presented within the thesis is that of packet aggregation. The operation of aggregation is explained in detail, along with the reasons for the significant available throughput increase to 802.11 from aggregation. Aggregation is then developed to produce even higher throughput, and to be a more robust mechanism. Additionally, aggregation is formally described in the form of an update to the existing 802.11 standard. Following this, two more improvements are shown that can be used either with or without the aggregation mechanism. Stored frame headers are designed to reduce repetition of control data, and combined acknowledgements are an expansion of the block acknowledgement system introduced in the 802.11e supplement. This is followed by a description of the simulation environment used to test the three improvements presented, such as the settings used and metrics created. The results of the simulations of the improvements are presented along with the discussion. The developments to the basic improvements are also simulated and discussed in the same way. Finally, conclusions about the improvements detailed and the results shown in the simulations are drawn. Also at the end of the thesis, the possible future direction of research into the improvements is given, as well as the aspects and issues of implementing aggregation on a personal computer based platform

Control of Robotic Mobility-On-Demand Systems: a Queueing-Theoretical Perspective

In this paper we present and analyze a queueing-theoretical model for autonomous mobility-on-demand (MOD) systems where robotic, self-driving vehicles transport customers within an urban environment and rebalance themselves to ensure acceptable quality of service throughout the entire network. We cast an autonomous MOD system within a closed Jackson network model with passenger loss. It is shown that an optimal rebalancing algorithm minimizing the number of (autonomously) rebalancing vehicles and keeping vehicles availabilities balanced throughout the network can be found by solving a linear program. The theoretical insights are used to design a robust, real-time rebalancing algorithm, which is applied to a case study of New York City. The case study shows that the current taxi demand in Manhattan can be met with about 8,000 robotic vehicles (roughly 60% of the size of the current taxi fleet). Finally, we extend our queueing-theoretical setup to include congestion effects, and we study the impact of autonomously rebalancing vehicles on overall congestion. Collectively, this paper provides a rigorous approach to the problem of system-wide coordination of autonomously driving vehicles, and provides one of the first characterizations of the sustainability benefits of robotic transportation networks.Comment: 10 pages, To appear at RSS 201

Queueing analysis of opportunistic scheduling with spatially correlated channels

International audienc

Filling the Gap: a Tool to Automate Parameter Estimation for Software Performance Models

© 2015 ACM.Software performance engineering heavily relies on application and resource models that enable the prediction of Quality-of-Service metrics. Critical to these models is the accuracy of their parameters, the value of which can change with the application and the resources where it is deployed. In this paper we introduce the Filling-the-gap (FG) tool, which automates the parameter estimation of application performance models. This tool implements a set of statistical routines to estimate the parameters of performance models, which are automatically executed using monitoring information kept in a local database