Sang-Bang Choi

Task scheduling algorithm using minimized duplications in homogeneous systems

For fine grain task graphs, duplication-based scheduling algorithms are generally more efficient than list and cluster-based algorithms. However, most duplication-based heuristics try to duplicate all possible ancestor nodes of a given join node, in order to reduce the earliest start time (EST) of the join node, even though these ancestor nodes have already been allocated in previous steps. Thus, these duplication heuristics inevitably induce redundant duplications, which lead to the superfluous consumption of resources and generally deteriorate the scheduling result in the case of a bounded number of processors. When scheduling algorithms are used on an unbounded number of processors, the required number of processors grows excessively with the size of the task graph, thereby limiting the practicality of these algorithms for large task graphs. In this paper, we propose a novel algorithm designed to allocate join nodes without redundant duplications. In the proposed algorithm, if the ancestor nodes of a join node are duplicated when scheduling the join node, the original allocations of these ancestor nodes are removed using a very efficient method. The performance of the proposed algorithm, in terms of its normalized schedule length and efficiency, is compared with that of some of the recently proposed algorithms. The proposed algorithm generates better or comparable schedules with minimized duplication. Specifically, the simulation results show that it is most useful on a bounded number of processors.

Multi-Sensor Fusion with Interacting Multiple Model Filter for Improved Aircraft Position Accuracy

The International Civil Aviation Organization (ICAO) has decided to adopt Communications, Navigation, and Surveillance/Air Traffic Management (CNS/ATM) as the 21st century standard for navigation. Accordingly, ICAO members have provided an impetus to develop related technology and build sufficient infrastructure. For aviation surveillance with CNS/ATM, Ground-Based Augmentation System (GBAS), Automatic Dependent Surveillance-Broadcast (ADS-B), multilateration (MLAT) and wide-area multilateration (WAM) systems are being established. These sensors can track aircraft positions more accurately than existing radar and can compensate for the blind spots in aircraft surveillance. In this paper, we applied a novel sensor fusion method with Interacting Multiple Model (IMM) filter to GBAS, ADS-B, MLAT, and WAM data in order to improve the reliability of the aircraft position. Results of performance analysis show that the position accuracy is improved by the proposed sensor fusion method with the IMM filter.

Online gaming traffic generator for reproducing gamer behavior

In this paper, we proposed an online gaming traffic generator reflecting user behavior patterns. We analyzed the packet size and inter departure time distributions of a popular FPS game (Left4Dead) and MMORPG (World of Warcraft) for regenerating gaming traffic. The proposed traffic generator generates an inter departure time and gaming packet based on analytical model of the gamer behaviors, then transmits the packet according to the inter departure time. Packet generation results show that generated packets of World of Warcraft is much different with analytical model, unlike Left4Dead. It is caused by Nagle algorithm and Delayed Acknowledgments of TCP. Thus, we disabled the Nagle algorithm in the proposed traffic generator. The generation results show that the revised proposed traffic generator guarantees goodness of fit in the generated traffic distribution.

The implementation of start stop system with the OBD-II interface in the automotive smart key system

Along with the growing needs for the low energy consumption technology and the strengthening vehicle environmental regulations, the researches on the start stop system, which stops the engine on idle, have been briskly carried out around the automobile makers before the appearance of the alternative energy. In addition, the automobile makers are trying to popularize the start stop system by combining the system to the generalized smart key system to not only arouse purchasing but also provide the convenience and reduce the energy consumption as well. In this paper, we designed and implemented the start stop system algorithm for the aftermarket smart key system which uses the OBD-II interface. The implemented start stop system is capable of controlling two independent systems, both an eco-friendly start stop system and a convenient smart key system, on a single ECU. Furthermore, the implemented start sop system standardizes the interface with the vehicles to reduce the time required for installing the start stop system to the various vehicles, and satisfies every standard response time limit for the vehicle status request signals.

Task Scheduling Algorithm with Minimal Redundant Duplications in Homogeneous Multiprocessor System

The performance of a homogeneous multiprocessor system depends on an algorithm which schedules input DAG. Among various task scheduling algorithms, ones that are using full duplication provide superior performance by duplicating tasks recursively. However, redundant duplications lead to increase of total execution time and decrease of processor idle time. In this paper, we propose GDRA which reduces total execution time and increases processor idle time by eliminating redundant duplications. Comparisons with other full duplication algorithms, such as CPFD, SD, and MDJ, show that GDRA provides the better performance as the CCR increases.

MPEG-4 stream transmission and synchronization for parallel servers

Our new multimedia transmission and synchronization scheme for parallel servers in a wireless environment enables servers to store MPEG-4 data according to video-object-plane type. The goal of our research, therefore, was to develop an enhanced multimedia transmission scheme that can cope with load imbalance, congestion, and jitter. Accordingly, we evaluated three issues: data striping, priority queuing, and multimedia synchronization.

A study on ubiquitous intelligent healthcare systems in home service aggregation business model

This study proposes a ubiquitous intelligent healthcare system that can be applied to a Home Service Aggregation business model. This system consists of a wireless network system to collect data and a sensor module, which measures body fat, blood pressure, quantity of exercise, and SPO2. In addition, an HSA server is configured to integrate user certification and security, VOD, and power usage information. A healthcare server collects user health information and sends the data in case of emergency to a doctor or guardian in order to achieve a ubiquitous intelligent healthcare system.

VOD multicast using CIWP and p2p partial stream transfer

Providing VOD in the internet is one of the challenging technologies. When a new client joins an ongoing multicast session for VOD service, the servers using CIWP scheme for the VOD multicast creates an additional unicast channel to serve the partial stream. And, the unicast channel consumes a certain amount of the I/O bandwidth of the server, as well as some of the network resources between the server and clients. This problem can be solved by using p2p local transfer between the clients to deliver the partial stream. In this paper, we propose a new VOD multicast scheme that is based on the CIWP scheme and the p2p transfer of the partial multimedia stream. In the p2p approach, unexpected dropout of a client, due to the failure of the connection or departure from the current session, can disrupt the partial stream transfer for the other clients. Thus, we also propose a procedure to recover from this kind of unexpected dropout. Our simulation results show that the proposed scheme reduces the network bandwidth on the server side dramatically, reduces the average waiting time of the client, and improves the service quality.