Response Time Requirements Research Articles

A Ubiquitous Power Management System to Balance Energy Savings and Response Time Based on Device- level Usage Prediction

Power conservation has become a serious concern during people's daily life. Ubiquitous computing technologies clearly provide a potential way to help us realize a more environment-friendly lifestyle. In this paper, we propose a ubiquitous power management system called Gynapse, which uses multi-modal sensors to predict the exact usage of each device, and then switches their power modes based on predicted usage to maximize the total energy saving under the constraint of user required response time. We build a three-level Hierarchical Hidden Markov Model (HHMM) to represent and learn the device level usage patterns from multi-modal sensors. Based on the learned HHMM, we develop our predictive mechanism in Dynamic Bayesian Network (DBN) scheme to precisely predict the usage of each device, with user required response time under consideration. Based on the predicted usage, we follow a four-step process to balance the total energy saving and response time of devices by switching their power modes accordingly. Preliminary results demonstrate that Gynapse has the capability to reduce power consumption while keeping the response time within user's requirement, and provides a complementary approach to previous power management systems.

Embedded systems engineering with the AADL

The SAE Architecture Analysis & Design Language (AADL) is an architecture description language for real-time, fault-tolerant, scalable, embedded, modular multiprocessor systems. It enables the development of highly evolvable systems, early and quantitative analyses of a system's architecture, and evolution of an architecture model for continued analysis throughout the lifecycle. In this tutorial, we provide an overview of the AADL; demonstrate the AADL's capabilities in creating and analyzing component-based models of the task and task interaction architectures of embedded software; discuss interfacing to physical devices; highlight AADL capabilities for predictive analyses of operational characteristics such as meeting deadline, response time, and throughput requirements; and describe how the AADL can discover system integration problems early in a development effort.

Nuclear plant temperature instrumentation

Most critical process temperatures in nuclear power plants are measured using resistance temperature detectors (RTDs) and thermocouples. In addition to excellent reliability and accident survivability, nuclear safety-related RTDs are expected to have good calibration and fast dynamic response time, as these characteristics are important to plant safety and economy. In plants where RTDs are installed in thermowells in the primary coolant pipes, response-time requirements have a range of 4.0–8.0 s versus the direct-immersion RTDs installed in bypass loops which have a required response range of 1.0–3.0 s. The variety of problems that can affect the accuracy and response time of RTDs is extensive: dynamic response problems, failure of extension leads, low-insulation resistance, premature failure, wrong calibration tables, loose or bad connections, large EMF effects, open elements, thinning of the platinum wire, lead-wire imbalance, seeping of chemicals from the connection head into the thermowell, cracking of the thermowell, and erroneous indication. The causes of core-exit thermocouples failure can take the form of large calibration shifts, erratic and noisy output, saturated output, accidental reverse connections, and response-time degradation. Several effective methods for detecting RTD and thermocouple performance failure while the plant is operating are available. To detect accuracy problems, the cross-calibration technique is effective for both RTDs and core-exit thermocouples. It involves recording the readings of redundant online RTDs, averaging these readings, and calculating the deviation of each RTD from the average, less any outliers. To detect response time degradation online, the loop current step response (LCSR) test is the most accurate method. However, the noise analysis technique remains the most popular for detecting response time degradation in core-exit thermocouples.

Efficient index compression in DB2 LUW

In database systems, the cost of data storage and retrieval are important components of the total cost and response time of the system. A popular mechanism to reduce the storage footprint is by compressing the data residing in tables and indexes. Compressing indexes efficiently, while maintaining response time requirements, is known to be challenging. This is especially true when designing for a workload spectrum covering both data warehousing and transaction processing environments. DB2 Linux, UNIX, Windows (LUW) recently introduced index compression for use in both environments. This uses techniques that are able to compress index data efficiently while incurring virtually no performance penalty for query processing. On the contrary, for certain operations, the performance is actually better. In this paper, we detail the design of index compression in DB2 LUW and discuss the challenges that were encountered in meeting the design goals. We also demonstrate its effectiveness by showing performance results on typical customer scenarios.

Improving OLTP scalability using speculative lock inheritance

Transaction processing workloads provide ample request level concurrency which highly parallel architectures can exploit. However, the resulting heavy utilization of core database services also causes resource contention within the database engine itself and limits scalability. Meanwhile, many database workloads consist of short transactions which access only a few database records each, often with stringent response time requirements. Performance of these short transactions is determined largely by the amount of overhead the database engine imposes for services such as logging, locking, and transaction management. This paper highlights the negative scalability impact of database locking, an effect which is especially severe for short transactions running on highly concurrent multicore hardware. We propose and evaluate Speculative Lock Inheritance, a technique where hot database locks pass directly from transaction to transaction, bypassing the lock manager bottleneck. We implement SLI in the Shore-MT storage manager and show that lock inheritance fundamentally improves scalability by decoupling the number of simultaneous requests for popular locks from the number of threads in the system, eliminating contention within the lock manager even as core counts continue to increase. We achieve this effect with only minor changes to the lock manager and without changes to consistency or other application-visible effects.

Efficient top-k processing over query-dependent functions

We study the efficient evaluation of top-k queries over data items, where the score of each item is dynamically computed by applying an item-specific function whose parameter value is specified in the query. For example, online retail stores rank items by price, which may be a function of the quantity being queried: "Stay 3 nights, get a 15% discount on double-bed rooms." Similarly, while ranking possible routes in online maps by predicted congestion level, the score (congestion) is a function of the time being queried, e.g., "At 5PM on a Friday in Palo Alto, the congestion level on 101 North is high." Since the parameter---the number of nights or the time the online map is queried, in the above examples---is only known at query time, and online applications have stringent response-time requirements, it is infeasible to evaluate every item-specific function to determine the item scores, especially when the number of items is large. Further, space considerations make it infeasible to pre-compute and store the score of each item for each value of the input parameter. In this paper, we develop a novel technique that compresses the (large) set of item scores for all parameter values by dividing the parameter range into intervals, taking into account the expected query workload. This compressed representation is then used to do top-k pruning of query results. Our experiments show that the proposed techniques are scalable and efficient.

Cloaking locations for anonymous location based services: a hybrid approach

An important privacy issue in Location Based Services is to hide a user’s identity while still provide quality location based services. Previous work has addressed the problem of locational \(\mathcal{K}\)-anonymity either based on centralized or decentralized schemes. However, a centralized scheme relies on an anonymizing server (AS) for location cloaking, which may become the performance bottleneck when there are large number of clients. More importantly, holding information in a centralized place is more vulnerable to malicious attacks. A decentralized scheme depends on peer communication to cloak locations and is more scalable. However, it may pose too much computation and communication overhead to the clients. The service fulfillment rate may also be unsatisfied especially when there are not enough peers nearby. This paper proposes a new hybrid framework called HiSC that balances the load between the AS and mobile clients. HiSC partitions the space into base cells and a mobile client claims a surrounding area consisting of base cells. The number of mobile clients in the surrounding cells is kept and updated at both client and AS sides. A mobile client can either request cloaking service from the centralized AS or use a peer-to-peer approach for spatial cloaking based on personalized privacy, response time, and service quality requirements. HiSC can elegantly distribute the work load between the AS and the mobile clients by tuning one system parameter base cell size and two client parameters - surrounding cell size and tolerance count. By integrating salient features of two schemes, HiSC successfully preserves query anonymity and provides more scalable and consistent service. Both the AS and the clients can enjoy much less work load. Additionally, we propose a simple yet effective random range shifting algorithm to prevent possible privacy leakage that would exist in the original P2P approach. Our experiments show that HiSC can elegantly balance the work load based on privacy requirements and client distribution. HiSC provides close to optimal service quality. Meanwhile, it reduces the response time by more than an order of magnitude from both the P2P scheme and the centralized scheme when anonymity level(value of \(\mathcal{K}\)) or number of clients is large. It also reduces the update message cost of the AS by nearly 6 times and the peer searching message cost of the clients by more than an order of magnitude.

Geographic Analysis of Ambulance Availability in Arkansas

In keeping with emergency medical services (EMS) industry standards, response time requirements of EMS units in Arkansas are temporally based and reflect traditionally accepted concepts of reasonable access to emergency care services. However, time-centric response standards may be unrealistic and may place ambulance staff and patients at risk, particularly during mass casualty events. In view of the availability of current technology to efficiently re-route EMS units on the basis of geographic realities, traditional 4-minute and 8-minute response time standards should be reevaluated and replaced by or added to standards that emphasize spatially based objectives.

Wavelet synopsis for hierarchical range queries with workloads

Synopses structures and approximate query answering have become increasingly important in DSS/ OLAP applications with stringent response time requirements. Range queries are an important class of problems in this domain, and have a wide variety of applications and have been studied in the context of histograms. However, wavelets have been shown to be quite useful in several scenarios and in fact their multi-resolution structure makes them especially appealing for hierarchical domains. Furthermore the fact that the Haar wavelet basis has a linear time algorithm for the computation of coefficients has made the Haar basis one of the important and widely used synopsis structures. Very recently optimal algorithms were proposed for the wavelet synopsis construction problem for equality/point queries. In this paper we investigate the problem of optimum Haar wavelet synopsis construction for range queries with workloads. We provide optimum algorithms as well as approximation heuristics and demonstrate the effectiveness of these algorithms with our extensive experimental evaluation using synthetic and real-life data sets.

Gas jet disruption mitigation studies on Alcator C-Mod and DIII-D

High-pressure noble gas jet injection is a mitigation technique which potentially satisfies the requirements of fast response time and reliability, without degrading subsequent discharges. Previously reported gas jet experiments on DIII-D showed good success at reducing deleterious disruption effects. In this paper, results of recent gas jet disruption mitigation experiments on Alcator C-Mod and DIII-D are reported. Jointly, these experiments have greatly improved the understanding of gas jet dynamics and the processes involved in mitigating disruption effects. In both machines, the sequence of events following gas injection is observed to be quite similar: the jet neutrals stop near the plasma edge, the edge temperature collapses and large MHD modes are quickly destabilized, mixing the hot plasma core with the edge impurity ions and radiating away the plasma thermal energy. High radiated power fractions are achieved, thus reducing the conducted heat loads to the chamber walls and divertor. A significant (2 × or more) reduction in halo current is also observed. Runaway electron generation is small or absent. These similar results in two quite different tokamaks are encouraging for the applicability of this disruption mitigation technique to ITER.

A course in real-time embedded software

Embedded systems are increasingly pervasive, and the creation of reliable controlling software offers unique challenges. Embedded software must interact directly with hardware, it must respond to events in a time-critical fashion, and it typically employs concurrency to meet response time requirements. This paper describes an innovative course that gives students in-depth exposure to the challenges of writing reliable, time-critical, concurrent code. Students design and implement a real-time operating system (RTOS), and they write application code that uses the RTOS they construct. Code development and debugging take place in a simulation environment that offers visibility into the system and strictly repeatable execution while maintaining hardware compatibility. We describe the structure of the class, the custom tools used, and the laboratory sequence that results in a functional RTOS. We discuss the development of the class and its impact on our students.

Server Allocation Algorithms for Tiered Systems

Many web-based systems have a tiered application architecture, in which a request needs to transverse all the tiers before finishing its processing. One of the most important QoS metrics for these applications is the expected response time for the user. Since the expected response time in any tier depends upon the number of servers allocated to this tier, and a request's total response time is the sum of the response times over all the tiers, many different configurations (number of servers allocated to each tier) can satisfy the expected response-time requirement. Naturally, one would like to find the configuration that minimizes the total system cost while satisfying the total response-time requirement. This is modeled as a non-linear optimization problem using an open-queuing network model of response time, which we call the server allocation problem for tiered systems (SAPTS). In this paper we study the computational complexity of SAPTS and design efficient algorithms to solve it. For a variable number of tiers, we show that the decision version of SAPTS is NP-complete. Then we design a simple two-approximation algorithm and a fully polynomial-time approximation scheme (FPTAS). If the number of tiers is a constant, we show that SAPTS is polynomial-time solvable. Furthermore, we design a fast polynomial-time exact algorithm to solve the important two-tier case. Most of our results extend to the general case in which each tier has an arbitrary response-time function.

Queuing Analysis of Power Management in the IEEE 802.11 Based Wireless LANs

Energy efficiency is an important aspect in wireless networks and power management is a technique that can save energy. We investigate the power management in the IEEE 802.11 based infrastructure mode wireless LANs and seek the optimal power management parameters that can achieve good energy efficiency without degrading other performances. We propose two models for the power management scheme: the M/G/1 queue with bulk service model and the D/G/1 queue model. From the models, we obtain the analytical results for the energy efficiency and the response time performance metrics, which are controlled by a listen interval. Our simulation results are in good agreement with the analysis. Based on the analytical models and simulation, we propose to select the largest listen interval with the satisfaction of response time requirement. The analytical models can be used to predict system performance if system configurations are given. This can help system deployment and system optimization.

A performance comparison of distance-based query algorithms using R-trees in spatial databases

Efficient processing of distance-based queries (DBQs) is of great importance in spatial databases due to the wide area of applications that may address such queries. The most representative and known DBQs are the K Nearest Neighbors Query (KNNQ), ρ Distance Range Query ( ρDRQ), K Closest Pairs Query (KCPQ) and ρ Distance Join Query ( ρDJQ). In this paper, we propose new pruning mechanism to apply them in the design of new Recursive Best-First Search (RBFS) algorithms for DBQs between spatial objects indexed in R-trees. RBFS is a general search algorithm that runs in linear space and expands nodes in best-first order, but it can suffer from node re-expansion overhead (i.e. to expand nodes in best-first order, some nodes can be considered more than once). The R-tree and its variations are commonly cited spatial access methods that can be used for answering such spatial queries. Moreover, an exhaustive experimental study was also included using R-trees, which resulted to several conclusions about the efficiency of proposed RBFS algorithm and its comparison with respect to other search algorithms (Best-First Search (BFS) and Depth-First Branch-and-Bound (DFBnB)), in terms of disk accesses, response time and main memory requirements, taking into account several important parameters as maximum branching factor ( Cmax), cardinality of the final query result ( K), distance threshold ( ρ) and size of a global LRU buffer ( B). In general RBFS is competitive for KNNQ and KCPQ where the maximum branching factor ( Cmax) is large enough (even better than DFBnB and very close to BFS), and it is a good alternative when we have main memory limitations in our computer due to high process overload in our system, since it is linear space consuming with respect to the height of the R-trees. Nevertheless, RBFS is the worst alternative for ρDRQ and ρDJQ. DFBnB is also a linear space algorithm and it obtains the same behavior as BFS for ρDRQ and ρDJQ; and it is the best when an LRU buffer was included. Finally, we have been able to check experimentally that BFS is the best for all DBQs, but it can consume many main memory resources to perform spatial queries.

Gas jet disruption mitigation studies on Alcator C-Mod

Damaging effects of disruptions are a major concern for Alcator C-Mod, ITER and future tokamak reactors. High-pressure noble gas jet injection is a mitigation technique which potentially satisfies the operational requirements of fast response time and reliability, while still being benign to subsequent discharges. Disruption mitigation experiments using an optimized gas jet injection system are being carried out on Alcator C-Mod to study the physics of gas jet penetration into high pressure plasmas, as well as the ability of the gas jet impurities to convert plasma energy into radiation on timescales consistent with C-Mod's fast quench times, and to reduce halo currents given C-Mod's high-current density. The dependence of impurity penetration and effectiveness on noble gas species (He, Ne, Ar, Kr) is also being studied. It is found that the high-pressure neutral gas jet does not penetrate deeply into the C-Mod plasma, and yet prompt core thermal quenches are observed on all gas jet shots. 3D MHD modelling of the disruption physics with NIMROD shows that edge cooling of the plasma triggers fast growing tearing modes which rapidly produce a stochastic region in the core of the plasma and loss of thermal energy. This may explain the apparent effectiveness of the gas jet in C-Mod despite its limited penetration. The higher-Z gases (Ne, Ar, Kr) also proved effective at reducing halo currents and decreasing thermal deposition to the divertor surfaces. In addition, noble gas jet injection proved to be benign for plasma operation with C-Mod's metal (Mo) wall, actually improving the reliability of the startup in the following discharge.

DAWN: an efficient framework of DCT for data with error estimation

On-line analytical processing (OLAP) has become an important component in most data warehouse systems and decision support systems in recent years. In order to deal with the huge amount of data, highly complex queries and increasingly strict response time requirements, approximate query processing has been deemed a viable solution. Most works in this area, however, focus on the space efficiency and are unable to provide quality-guaranteed answers to queries. To remedy this, in this paper, we propose an efficient framework of DCT for dAta With error estimatioN, called DAWN, which focuses on answering range-sum queries from compressed OP-cubes transformed by DCT. Specifically, utilizing the techniques of Geometric series and Euler's formula, we devise a robust summation function, called the GE function, to answer range queries in constant time, regardless of the number of data cells involved. Note that the GE function can estimate the summation of cosine functions precisely; thus the quality of the answers is superior to that of previous works. Furthermore, an estimator of errors based on the Brown noise assumption (BNA) is devised to provide tight bounds for answering range-sum queries. Our experiment results show that the DAWN framework is scalable to the selectivity of queries and the available storage space. With GE functions and the BNA method, the DAWN framework not only delivers high quality answers for range-sum queries, but also leads to shorter query response time due to its effectiveness in error estimation.

PERFORMANCE ANALYSIS FOR QOS PROVISIONING IN MPLS/DIFFSERV- BASED IP NETWORKS WITH NON-PREEMPTIVE PRIORITY QUEUING SYSTEM

A typical operating environment of a packet switching (store-and-forward) computer communication network is that it is shared by many users with different classes of packets. Packets may be classified in a very general fashion by types of users, messages, applications, transactions, response time requirements, packet parameters such as packet rate and length, and by network parameters such as source-destination and path length. A well-designed network must provide access and performance assurance to all packet classes. An architecture for designing such a communication network is presented in [1]. This architecture is based on MPLS as an underlying technology used for IP transport and DiffServ-like mechanisms for QoS provision which use simple priority queuing to differentiate several traffic classes by assigning them different delay targets. In this paper, we introduce a mathematical model for performance evaluation for QoS Provisioning in MPLS/DiffServ-Based IP Networks. This mathematical model is formulated to evaluate the performance of the proposed architecture described in [1]. Two parts are considered in the evaluation. One, is the analysis of the proposed QoS routing algorithms that are used in the proposed architecture, the other is the analysis of the average packet delay over the network. An M/G/1 Non-preemptive priority queuing system is used as the evaluation model to analyze the average packet delay over the network. Relative MPLS/DiffServ with Non-Preemptive Priority Queuing system performance compared to MPLS/DiffServ without priority (FIFO)[2] is evaluated. The results indicate that for well-designed MPLS/DiffServ equipments, original IP packet delay can be reduced by 39% or more with FIFO queuing system [2] and 42% or more with Nonpreemptive priority queuing system

A reference model of fire detection and monitoring system using BACnet

The objective of this paper is to introduce a reference model of BACnet-based fire detection and monitoring system using MS/TP and ARCNET protocols. The reference model is designed to satisfy the requirements of response time, survivability and flexibility. The reference model is operated on the basis of BACnet, a standard communication protocol for building automation systems. In this study, a simulator for the reference model of fire detection and monitoring system was developed. Using the simulator, this study examined the validity of the reference model proposed in this study. This study also evaluated the performance of the BACnet-based fire detection and monitoring system in terms of network-induced delay. Simulation results show that the reference model satisfies the requirements of fire detection and monitoring system.

Data sharing between ada and C/C++

The En Route Automation Modernization (ERAM) program is a real-time Air Traffic Control (ATC) program being developed by Lockheed Martin Corporation. The ERAM program has high availability requirements, mission critical applications, and stringent response time requirements. The estimated size of the ERAM program is 1,300 KSLOC and includes primarily Ada, C, and C++ code. Legacy code being reused in ERAM is both Ada and C. This resulted in the need for several cross-language interfaces. Standard methods for passing binary data structures between the languages have been developed and will be discussed in this paper.

63.3: Automated System for Response Time Optimization and Flicker Reduction In LCD Manufacturing

In order to meet the important requirement of fast response time for LCD-TV applications, the so-called Response Time Compensation (RTC) technique has been widely used. Defining an optimum look-up table (LUT) is a key process step for the application of this technology, but deriving optimized table entries is difficult to do and historically has taken excessive time. Expanding on our algorithmic development work presented at SID'04, we have created a fully automated system for obtaining an optimal LUT. Without requiring any operator involvement, this system quickly and objectively measures the panel under test, calculates optimized LUT values, and programs those values into the panel's non-volatile memory. Additionally, a new flicker minimization algorithm has been developed and implemented in this same system by using a digital potentiometer to set Vcom. Using this system, it is possible to optimize panel parameters for all products in the production line, resulting in very uniform image quality for all LCD-TV panels in spite of variations in process conditions.