Ding-Jung Chiang

Disseminating data with time constraint based on multichannel over ubiquitous computing environments

Time-constrained service plays an important role in ubiquitous services. However, the resource constraints of ubiquitous computing systems make it difficult to satisfy timing requirements of supported strategies. In this study, we study scheduling strategies for mobile data program with timing constraints in the form of deadlines. Unlike previously proposed scheduling algorithms for mobile systems which aim to minimize the mean access time, our goal is to identify scheduling algorithms for ubiquitous systems that ensure requests meet their deadlines. We present a study of the performance of traditional real-time strategies, and demonstrate that traditional real-time algorithms do not always perform the best in a mobile environment. We propose an efficient scheduling algorithm, called scheduling priority of mobile data with time constraint(SPMT), which is designed for timely delivery of data to mobile clients. The experimental results show that our approach outperforms other approaches over performance criteria.

Nurse scheduling with joint normalized shift and day-off preference satisfaction using a genetic algorithm with immigrant scheme

To make a fair and satisfactory nurse shift schedule, this paper proposes a novel preference satisfaction function, in which numbers of the preferred work shifts and days-off of the nursing staff are balanced, and ranks for preferences and number of the preference ranks satisfied so far are also considered. Such a preference function is capable of equivalently and fairly planning the nurse preference schedule to improve the total satisfaction. Additionally, distributed sensors can be applied to collect the information on hospital beds to provide the schedule planner to determine the lowest required amount of manpower for each work shift, to avoid the working overload of the nursing staff. To solve the nursing schedule problem, we propose a genetic algorithm (GA) with an immigrant scheme, in which utilization of the immigrant scheme is helpful in efficiently reducing amount of infeasible solutions due to practical scheduling constraints, so that the GA can efficiently find better solutions for larger-scale problems. Performance of the proposed GA with and without solution recovery scheme is evaluated by conducting a comprehensive experimental analysis on three different-size instances.

Real-Time Data Delivery Using Prediction Mechanism in Mobile Environments

Mobile data delivery is a critical issue in the mobile computing area. One of the most important problems is the efficient access to data. A proposed solution to this problem is the prefetching technique which consists in putting in reserving the information before the users need it. Low bandwidth, unreliable wireless links, and frequent disconnections of mobile environments make it difficult to satisfy the timing requirements of traditional strategies. This paper investigates broadcast scheduling strategies for push-based broadcast with timing constraints in the form of deadlines ,and proposes a prediction algorithm based on Kalman filter theory for this study. The proposed dissemination policy and adaptive bandwidth allocation scheme obtain sufficient conditions such that all the time-bounded traffic sources satisfy their timing constraints to provide various quality of service guarantees in the broadcast period. Our goal is to identify scheduling algorithms for broadcast systems that ensure requests meeting their deadlines. Our approach examines the performance of traditional real-time strategies and mobile broadcasting strategies, and demonstrates that traditional real-time algorithms do not always perform the best in mobile environments. The proposed design indeed achieves good performance in mobile environments.

Scheduling Management for Multiple Real-Time Data over On-Demand Mobile Environments

Many time-constraint applications operate on continuous queries and need real-time data services in on-demand mobile environments. Providing deadline guarantees for queries over dynamic multiple data is a challenging problem due to continuous query rates and time-varying contents. The accurately approximated optimum distributions is used to obtain analytical expressions for performance metrics such as average real-time miss rate and outage probability. The normal probability distribution function of client request to channel hopping is approximated. In the analysis multiple channel model based on currently transmitting is considered over independent and not identically distributed wireless channels. In addition the performance of currently transmitting is compared with the QoS-based management scheme for real-time query processing. The numerical results are validated by linear programming simulations. It is shown that for broadcasting real-time data placement, this contribution is very useful and efficient for exact performance analysis and design of wireless multi-channel links.

Quality of Service Provisioning Scheme for Data Dissemination with Time Constraints in Ubiquitous Environments

This paper considers the support of time-constraint services to mobile users in a ubiquitous environment. The challenge for a database with time constraint services becomes more important in a ubiquitous computing environment. Low bandwidth, unreliable wireless links, and frequent disconnections of ubiquitous environments make it difficult to satisfy the timing requirements of supported strategies. This study investigates broadcast scheduling strategies for push-based broadcast with timing constraints in the form of deadlines, and proposes a multichannel scheduling algorithm for push-based broadcast with timing constraints. Under such a scheme, modifying the access method in the broadcast period supports data allocation on multiple channels, allowing time-constraint property to be satisfied in ubiquitous environments. The proposed dissemination policy and adaptive bandwidth allocation scheme obtain sufficient conditions such that all the time-bounded traffic sources satisfy their timing constraints to provide various quality-of-service (QoS) guarantees in the broadcast period. Our goal is to identify scheduling algorithms for broadcast systems that ensure requests meet their deadlines. This study examines the performance of traditional real-time strategies and mobile broadcasting strategies, and demonstrates that traditional real-time algorithms do not always perform the best in a mobile environment. The proposed design indeed achieves good performance in ubiquitous environments.

Intuitive Projection Display System Supporting the Manipulation of Dual Laser Pens

The combined use of computers and projectors in delivering multimedia presentations and in teaching is very common. However, the common operating tools used to deliver presentations such as presentation pens or mice either have limited manipulation functionality or are less convenient, and it is difficult to perform functions such as zooming, rotating images, and writing. In addition to allowing users to move freely in space to remotely perform functions, the laser pen manipulation system proposed in this paper can also perform the writing functions of a laser pen. Moreover, the system can also support the simultaneous use of two laser pens to realize a touch mode similar to that of a tablet computer, thus achieving an intuitive projection display manipulation experience.

Unified Performance Analysis of Multihop Wireless Communication Link over Multi-channels

With the rapid increasing of wireless request, user mobility is a critical influence on system performance of mobile environments. Unlike conventional distributed systems, the mobility of users is the major characteristic in a mobile computing environment so that the value of data may depend on location, and processing of a query at one site may give different results than that at another. In this paper, we present the broadcast-based location dependent data delivery scheme for location-based queries. In the approach, broadcasted data objects are dynamically adjusted based on their locations, and the server broadcasts the location dependent data along with access popularity. Then, we present a data evaluation scheme, designed to reduce the query response time. Simulation experiments are conducted to compare the performance of our method with other issues. The results show that our schemes outperform the conventional strategies.

Broadcasting Data Items with Time Constraints Based on On-Demand Multichannel in Ubiquitous Environments

This study proposes mobile services with time constraints in ubiquitous computing environments based on on-demand multichannel broadcasting. For real-time mobile service, the need of mobile service for a real-time database management model is strong and providing real-time response to mobile transaction has became basic strategies in mobile data management. However, the resource constraints of ubiquitous computing systems make it difficult to satisfy timing requirements of supported strategies. This study provides on-line scheduling strategies for mobile data with timing constraint on multichannel broadcasting environments based on on-demand mode. The goal of this study ensures the most requests meeting their deadlines, which differs from previously proposed scheduling algorithms that aim to minimize the mean access time. The study presents a study of the performance of traditional real-time strategies and demonstrates traditional real-time algorithms which do not always perform the best in a mobile environment. The experimental results show the proposed algorithm, called on-demand broadcast program with time constraint (BPTC), outperforms miss rate for data timely delivery to mobile clients.

Valid Location Measuring in Location Dependent Data for Mobile Environments

Data caching is a crucial issue to improve systemperformance for service centers and increase access efficiencyfor mobile clients in mobile environments. Unlike conventionaldistributed systems, the mobility of users is the major characteristicin a mobile computing environment so that the valueof data may depend on location, and processing of a queryat one site may give different results than that at another. In this paper, we study issues on the efficiency of temporaldependentand spatial-dependent for location-dependent data ina mobile computing environment. We provide the method calledvalid location measuring (VLM) for representing the impacts onsystem performance with data valid scope and time-stamp oflocation-dependent data over wireless environments. Simulationexperiments are conducted to compare the performance of ourmethod with other issues. The results show that our schemesoutperform the conventional strategies.