Target Throughput Research Articles

Throughput-Optimal Multi-Mode Precoding MIMO System with Per-Substream AMC

In this paper, we study a multi-mode quantized precoding multiple-input multiple-output (MIMO) system with per-substream adaptive modulation and coding under a maximal throughput target. An analytical throughput expression is firstly presented by recurring to Gaussian mixed approximation for block error rate of Turbo codes. An optimal mode-MCS (modulation and coding scheme) selection algorithm is then developed to achieve maximal throughput performance based on throughput criterion. Further, a complexity-reducing selection algorithm with negligible performance loss is proposed by making full use of the information provided by singular value decomposition of the instantaneous channel matrix at the receiver side. Simulation results show that both selection algorithms can achieve good throughput performance in the above mentioned MIMO system.

Cycle-Time Key Factor Identification and Prediction in Semiconductor Manufacturing Using Machine Learning and Data Mining

Within the complex and competitive semiconductor manufacturing industry, lot cycle time (CT) remains one of the key performance indicators. Its reduction is of strategic importance as it contributes to cost decreasing, time-to-market shortening, faster fault detection, achieving throughput targets, and improving production-resource scheduling. To reduce CT, we suggest and investigate a data-driven approach that identifies key factors and predicts their impact on CT. In our novel approach, we first identify the most influential factors using conditional mutual information maximization, and then apply the selective naive Bayesian classifier (SNBC) for further selection of a minimal, most discriminative key-factor set for CT prediction. Applied to a data set representing a simulated fab, our SNBC-based approach improves the accuracy of CT prediction in nearly 40% while narrowing the list of factors from 182 to 20. It shows comparable accuracy to those of other machine learning and statistical models, such as a decision tree, a neural network, and multinomial logistic regression. Compared to them, our approach also demonstrates simplicity and interpretability, as well as speedy and efficient model training. This approach could be implemented relatively easily in the fab promoting new insights to the process of wafer fabrication.

Optimal life-of-mine scheduling for a Bauxite mine

This paper describes a new optimized life-of-mine planning software tool called Bodor (Boddington Optimizer), developed for BHP Billiton’s Boddington Bauxite mine in south Western Australia. Bodor minimizes pre-tax net present cost (capital and operational) over a specified mine life, and is applied to a mine model consisting of bauxite pods pre-designed to a fixed cut-off grade, directly feeding a refinery with bauxite that meets grade and throughput targets in each period over the life-of-mine. Bodor has been very successful in its application to the Boddington mining operation, producing a new life-of-asset mine plan which delivers a significant reduction in net present cost. This value add is achieved primarily through a better timing of ore-body exploitation which optimally trades-off lower haulage costs against some capital costs that are brought forward. A core aspect of Bodor’s utility lies in managing various complex environmental constraints in determining the optimal extraction schedule.

Emptying the Corridors of Shame: Organizational Lessons From England's 4-Hour Emergency Throughput Target

Since 2005, 98% of patients treated in England's emergency departments (EDs) must be discharged or placed in a hospital bed within 4 hours of arrival. Using a qualitative approach, we describe lessons learned from implementing the 4-hour emergency throughput target. This was a qualitative study of EDs in England, purposively sampled for a range of size and performance on the target. Leadership of EDs at 9 Acute Trusts (hospitals) were interviewed between June and August 2008. Using content analysis, we analyzed semistructured interviews to identify salient themes. Twenty-seven interviews were coded. Respondents agreed on the following themes. (1) Interdependency: Even with extensive ED process re-engineering, widespread Trust involvement was essential to meeting the target. Additionally, lack of recognition that it was a "Trust target" contributed to conflicts between staff, concerns for patient safety, and lost opportunity for organizational improvement. (2) Contrasting change management strategies: ED leadership used collaborative strategies, whereas change in the rest of the hospital required a top-down approach. (3) Burden and benefit for staff: Nursing perceived the greatest burden from the target but also acquired enhanced authority, skills, and roles. (4) COSTS: Although most EDs are now within range of the target, consistent performance while balancing patient safety remains tenuous. Achieving the 4-hour target requires hospital-wide support. Lack of organizational ownership contributes to negative effects on staff, incomplete process improvement, and risk to patients. These lessons have widespread implications for all targets and may help explain why some health care targets fail to achieve their aims.

The Business of Fast ALD Equipment for Depositing Alumina Passivation Layers on Crystalline Silicon Solar Cells.

ABSTRACTAtomic Layer Deposition (ALD) is a gas phase deposition technique for depositing very high quality thin films with an unsurpassed conformality. The main drawback of ALD however is the very low deposition rate (~ 1 nm/min). Recently, record deposition rates for alumina of up to 1 nm/s were reached using spatial ALD, while maintaining the typical assets regarding film quality as obtained by conventional, slow ALD [1]. This allows for ALD at high throughput numbers.One interesting application is passivation of crystalline silicon solar cells. Applying a thin alumina layer is reported to increase solar cell efficiency and enables the use of thinner wafers, thus reducing the main cost factor [2]. In this paper we report on the latest progress made by SoLayTec that delivered a working prototype of a system realizing full area single sided deposition of alumina on 156 x 156 mm2, mono- and multi crystalline silicon wafers for solar cell applications. The alumina layers showed excellent passivation. Based on this concept, a high-throughput ALD deposition tool is being developed targeting throughput numbers of up to 3000 wafers/hr. Finally, we report on the process of commercializing this technology.

High Throughput, Low Cost Deposition of Alumina Passivation Layers by Spatial Atomic Layer Deposition

ABSTRACTAtomic Layer Deposition (ALD) is a gas phase deposition technique for depositing very high quality thin films with an unsurpassed conformality. The main drawback of ALD however is the very low deposition rate (~ 1 nm/min). Recently, record deposition rates for alumina of up to 1 nm/s were reached using spatial ALD, while maintaining the typical assets regarding film quality as obtained by conventional, slow ALD [1]. This allows for ALD at high throughput numbers.One interesting application is passivation of crystalline silicon solar cells. Applying a thin alumina layer is reported to increase solar cell efficiency and enables the use of thinner wafers, thus reducing the main cost factor [2]. In this paper we report on the latest progress made by SoLayTec that delivered a working prototype of a system realizing full area single sided deposition of alumina on 156 x 156 mm2, mono- and multi crystalline silicon wafers for solar cell applications. The alumina layers showed excellent passivation. Based on this concept, a high-throughput ALD deposition tool is being developed targeting throughput numbers of up to 3000 wafers/hr, making ALD ready for mass production. This will bring on new opportunities in other applications.

Throughput analysis and bandwidth allocation for IEEE 802.11 WLAN with hidden terminals

Motivated by observations from real world wireless local area network (WLAN) deployments, we develop in this paper a novel analytical model to characterize the saturation throughput of an IEEE 802.11-based access point (AP) and stations under the influence of hidden terminals. Unlike existing models, our model can accommodate different numbers of hidden nodes without increasing the model complexity. Given any number of hidden nodes, only four constraints are needed to describe the interaction between stations and the AP with the consideration of both uplink and downlink traffic. Simulation evaluation shows that our model predicts network performance accurately over a wide range of network sizes and indicates the existence of a throughput starvation problem. To address this problem, based on our model, we formulate a bandwidth allocation problem to optimize the network throughput and fairness under some predefined requirements by systematically tuning the AP and stations contention windows. Simulation results show that the starvation problem is resolved with our approach, and the target throughput is met.

Leveraging Dynamic Spare Capacity in Wireless Systems to Conserve Mobile Terminals' Energy

In this paper, we study several ways in which mobile terminals can backoff on their uplink transmit power in order to extend battery lifetimes. This is particularly effective when a wireless system is underloaded as the degradation in user's perceived quality of service can be negligible. The challenge, however, is developing a mechanism that achieves a good tradeoff among transmit power, idling/circuit power, and the performance customers will see. We consider systems with flow-level dynamics supporting either real-time or best effort (e.g., file transfers) sessions. The energy-optimal transmission strategy for real-time sessions is determined by solving a convex optimization. An iterative approach exhibiting superlinear convergence achieves substantial amount energy savings, e.g., more than 50% when the session blocking probability is 0.1% or less. The case of file transfers is more subtle because power backoff changes the system dynamics. We study energy-efficient transmission strategies that realize energy-delay tradeoff. The proposed mechanism achieves a 35%-75% in energy savings depending on the load and file transfer target throughput. A key insight, relative to previous work focusing on <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">static</i> scenarios, is that idling power has a significant impact on energy-efficiency, while circuit power has limited impact as the load increases.

Stabilizing transport dynamics of control channels over wide-area networks

The next generation large-scale computing applications require network support for interactive visualization, computational steering and instrument control over wide-area networks. In particular, these applications require stable transport streams over wide-area networks, which are not adequately supported by current transport methods. We propose a new class of protocols capable of stabilizing a transport channel at a specified throughput level in the presence of random network dynamics based on the classical Robbins-Monro stochastic approximation approach. These protocols dynamically adjust the window size or sleep time at the source to achieve stable throughput at the destination. The target throughput typically corresponds to a small fraction of the available connection bandwidth. This approach yields provably probabilistically stable protocols as a consequence of carefully adjusted step sizes. The superior and robust stabilization performance of the proposed approach is extensively evaluated in a simulated environment and further verified through real-life implementations and deployments over both Internet and dedicated connections under disparate network conditions in comparison with existing transport methods.

Buffer and throughput trade-offs in M/ G/1/ K queueing networks: A bi-criteria approach

The optimal design of real-life systems modeled as finite queueing networks is a difficult stochastic optimization problem. Besides being non-linear and including integer variables, different objectives often conflict with each other. For example, one conflicting pair of objectives includes first minimizing the overall number of buffers and then maximizing throughput. In this paper, we present an original methodology to solve a buffer allocation and throughput trade-off problem in single server general queueing networks. An approximation of the complete set of all best solutions, known as the Pareto optimal or non-inferior set, is derived by a special version of a multi-objective genetic algorithm (MOGA). The applied MOGA proves to be suitable for the stochastic trade-off problem. A comprehensive set of computational results attest to the efficiency and efficacy of the proposed methodology. We were able to show from a medium-sized mixed network that the squared coefficient of service time variation plays an important role in buffer allocation, which indicates the importance of using a general service model. Moreover, after the analysis of the solutions in the decision variable space, we confirm that the buffer allocation is highly dependent on the target throughput, which sometimes can be sacrificed in favor of using fewer of the usually expensive buffer spaces.

Estimating Surface Facility Throughput during the Preclosure Emplacement Period at Yucca Mountain

This paper focuses on how variations in commercial spent nuclear fuel shipment schedules have the potential to impact preclosure operations at the proposed repository for high-level waste at Yucca Mountain (YM) in Nevada. The analysis employs a simulation tool developed by the authors for modeling the packaging and thermal characteristics of the waste stream arriving at Yucca Mountain and is related to a study on the safety of the surface facilities that was also conducted by the authors using the simulation tool. The objective of the research is to gain a better understanding of how waste-stream variations affect surface facility throughput, defined as the rate at which packages are prepared for aging or emplacement in the surface facilities at YM. The basis for and adequacy of the preliminary surface facility throughput requirements are reviewed by evaluating throughput performance subject to various preclosure operating scenarios.Results indicate that under most scenarios, the preliminary design adequately accommodates the mean demand over the operating lifetime for the canister receipt and closure facility (CRCF) and receipt facility (RF) but not the wet handling facility (WHF). While results indicate that WHF demand is likely to be higher than capacity in many scenarios, it seems reasonable that dual-purpose cask and truck deliveries could be deferred to maintain WHF operations at near-capacity levels.Results also show a high potential for variability in annual throughput demand at the CRCF and RF that might result in system backups. In the event of bottlenecks, the facility with less demand can fulfill functional roles of one that is overburdened. The overlap of functional capability in facilities incorporates flexibility into the system. However, since throughput targets are named per facility, as opposed to functions of the system, the design goals of the system as a whole are obscured. An alternative design is proposed that is based on functional goals within the facilities, along with other recommendations.

AFSO: An Adaptative Frame Size Optimization Mechanism for 802.11 Networks

In this paper, we analyze the impact of different frame types on self-similarity and burstiness characteristics of the aggregated frame traffic from a real 802.11 wireless local area network. We find that characteristics of aggregated frame traffic are affected by both mean frame size and the proportion of specified frame types. Based on this new knowledge, an adaptative frame size optimization (AFSO) mechanism is proposed to improve the transmission efficiency by adaptively adjusting data frame size according to the proportions of different frame types. Simulation results show that our proposed mechanism can effectively regulate the burstiness of aggregated frame traffic and improve the successful delivery rate of data frames when a fixed throughput target is set for 802.11 wireless networks.

Dynamic card number adjusting strategy in card-based production system

In a production line, throughput rate changes according to WIP (work in process) level and WIP is controlled through the number of production cards in a card-based production system. This paper presents a fast tuning card adjusting procedure using the CONWIP system, which can adjust the number of production cards to ensure desirable throughput rate. The method, termed DTC (difference throughput control), is based on the concept of classic automatic control theory. Whenever a TTH (target throughput value) is set, the difference between TTH and RTH (real time throughput value) is used to adjusting the number of cards. We test this procedure with an existing one in a variety of scenarios; the results show that the proposed procedure is competitive. We also analyse how processing time impacts on the performance of CONWIP system through simulation data.

A cross-layer approach to energy efficiency for adaptive MIMO systems exploiting spare capacity

In this paper, we propose a mechanism to switch between multiple-input multiple-output (MIMO) with two transmit antennas and single-input multiple-output (SIMO) to conserve mobile terminals' energy. We focus on saving uplink RF transmission energy of mobile terminals in cellular systems supporting best effort traffic. The key idea is to judiciously slow down transmission rates when a base station is underutilized. We show that there exists a crossover point on the transmission rate below which SIMO consumes less power than MIMO when circuit power is included. The crossover point is an increasing function of the circuit power, the number of receive antennas and channel correlation, all of which increase the potential energy savings resulting from mode switching. We propose an adaptive mode switching algorithm combined with rate selection to maintain a user's target throughput while achieving energy efficiency. Extensive flow-level simulations under dynamic loads confirm that the proposed technique can reduce the transmission energy by more than 50% and enables an effective tradeoff between file transfer delay and energy conservation.

An analysis of the ceiling height requirement for a large-scale semiconductor fab

This paper proposes the proposition that the fab ceiling height may become a bottleneck for throughput in a large-scale semiconductor fab. To justify the proposition, we propose a systematic approach for the design of the fab ceiling height. In this approach, we develop a queuing network model to evaluate the cycle time performance of a fab design under a target throughput. This queuing network model is adapted from Connor et al. [1996. A queueing network model for semiconductor manufacturing. IEEE Transactions on Semiconductor Manufacturing, 9 (3), 412–427] by additionally treating the transportation facilities as finite-capacity resources. Numerical experiments were carried out. The results indicate that a large-scale fab with an inappropriate ceiling height may limit the installation of transportation capacity, which, in turn, limits the utilisation of tool capacity, and thus lowers the fab throughput that can be achieved.

Filter preconditioning enables representative scaled-down modelling of filter capacity and viral clearance by mitigating the impact of virus spike impurities.

Endogenous and adventitious virus removal by size-exclusion membrane filtration is a critical dedicated step in an overall viral clearance strategy employed by biologics manufacturers as required by industry regulators. However, the addition of impurities from virus spike preparations used in validation studies can significantly reduce filter capacity, resulting in an oversized and suboptimal virus filtration step. The hydraulic filter performance and virus retention observed in conventional scaled-downed validation models may not necessarily represent performance observed during process development, nor be predictive of manufacturing performance. Using filter flow decay as a relevant processing endpoint, an alternative and more comprehensive approach to virus filter validation has been developed to overcome the limitations imposed by virus spike impurities. With a model feedstream, we have demonstrated comparable virus removal using the conventional virus spiking approach and a complementary preconditioned virus challenge. Similar to a currently accepted method used in the validation of sterilizing-grade filters, this method entails processing non-spiked feed to a volumetric throughput target, followed by processing virus-spiked feed to a final flow decay endpoint to determine viral clearance. This comprehensive approach yields predictive virus retention data under protein-dominant fouling conditions that better model the hydraulic performance of the manufacturing-scale virus filtration operation.

Cross layer dynamic resource allocation with targeted throughput for WCDMA data

We consider resource allocation for elastic wireless applications that measure utility by target connection average throughput and achieved throughput. We construct a framework for connection access control and rate scheduling that supports this class of applications by maximizing long term average utility. We present a decomposition of the problem into connection access control and rate scheduling layers. The connection access control layer considers current commitments and decides whether to admit new sessions. For admitted users, the layer sets a target throughput to be achieved of the lifetime of the session. The rate scheduling layer adjusts the instantaneous rates of each connection on the basis of how well it is achieving each performance goal and on the relative strength of each connectionpsilas current channel. We illustrate how commonly used connection access control and rate scheduling techniques can be applied to design these two layers using an exchange of information regarding future target throughputs and achieved throughputs. Through numerical analysis, we show how wireless channel time diversity and multi-user diversity can be exploited to construct a rate scheduling algorithm that is superior to proportional fairness. Finally, this utility-based framework is compared to a method that does not use utility.

Bit and Power Loading for OFDM-Based Three-Node Relaying Communications

Bit and power loading (BPL) techniques have been intensively investigated for the single-link communications. In this paper, we propose a margin-adaptive BPL approach for orthogonal frequency-division multiplexing (OFDM) systems assisted by a single cooperative relay. This orthogonal half-duplex relay operates either in the selection detection-and-forward (SDF) mode or in the amplify-and-forward (AF) mode. Maximum-ratio combining is employed at the destination to attain the achievable distributed spatial diversity-gain. Assuming perfect channel knowledge is available at all nodes, the proposed approach is to minimize the transmit-power consumption at the target throughput (average number of bits/symbol) and the target link performance. With respect to various power-constraint conditions, we investigate two distributed resource-allocation strategies, namely flexible power ratio (FLPR) and fixed power ratio (FIPR). The FLPR strategy is proposed for scenarios without individual local power constraint. The source power and relay power have a flexible ratio for each subcarrier. The FIPR strategy is proposed for scenarios with individual local power constraint. The source power and relay power have a fixed ratio for each subcarrier. Computer simulations are carried out to evaluate the proposed approach with respect to the relay location. Significant performance improvement is observed in terms of both the symbol-error-rate and the transmit-power efficiency.

Proportional and Deterministic Differentiation Methods of Multi-Class QoS in IEEE 802.11e Wireless LAN

Recently, wireless LAN is achieving remarkable growth and maturity. On the other hand, by the advance of the Internet, the demand for multimedia communication services which include video and voice will be expected to grow. Therefore, in the future, the mechanism of QoS guarantee must be realized even in wireless LAN environment. So far, IEEE 802.11e EDCF has been proposed, which is a contention based channel access method to achieve the QoS guarantee in wireless LAN. However, this cannot realize the desired throughput ratio or deterministic target throughput in principle. In this paper, we expand the EDCF to solve such QoS issues and enable more flexible QoS control. Moreover, we show the effectiveness of our proposal by computer simulation.

Simulation Tools for Glass Forming Processes by Drawing

In glass manufacturing a variety of different forming processes is used to meet product requirements like shape and quality but also throughput and cost targets might influence the decision for the optimal forming process. Out of these variety one can select a group of forming processes that have in some respects similar forming principles but then also some very different physics. The present paper focuses on similarities and differences of drawing processes and its requirements to modeling.