Heejae Kim

A VM Reservation-Based Cloud Service Broker and Its Performance Evaluation

We deal with a reservation-based cloud service broker (R-CSB). The main role of the R-CSB is to provide application execution services or Software-as-a-Service. The R-CSB makes a profit by an arbitrage between cloud service consumers and providers, and service fees from the consumers. In this paper, we first present detail concepts and architecture of the R-CSB. Also, to reduce the VM leasing cost, we discuss two schemes. The VM reservation scheme (C-VMR) makes the R-CSB reduce the VM leasing cost via leasing an appropriate number of reserved VMs. In addition to the C-VMR, we also present the VM allocation scheme (C-VMA) to allocate applications to VMs cost-effectively. Performance evaluation results show that the C-VMR has lower cost than other approaches and the C-VMA shows has higher average VM utilization than the conventional methods in most cases.

IsV2C: An Integrated Road Traffic-Network-Cloud Simulator for V2C Connected Car Services

The recent growth of connected car technology encourages IT and vehicle organizations to develop advanced vehicle-to-cloud (V2C) services such as driving assistance, infotainment, and vehicle maintenance. However, since their performances highly depend on the resource configuration and regional characteristics, it is almost impossible to examine the service feasibility in every candidate region by constructing real testbeds. To overcome this problem, we present an integrated road traffic-network-cloud simulator for V2C connected car services (IsV2C) with a user-friendly GUI. The IsV2C aims to evaluate V2C services with the user-specified V2C environment and service scenarios in a particular region. In the IsV2C, road traffic, network, and cloud simulation are intimately linked to reflect both the realistic movement of vehicles and service transactions in real-time. To accurately mimic task execution in both vehicles and the cloud, the IsV2C utilizes a rigorous emulation for evaluated services. Simulation results of the IsV2C show whether each simulated application satisfies the service level objectives regarding service time, cloud cost, and data transmission performance. As for the validation, we evaluated three sample V2C applications in an urban area, and the results proved that the IsV2C could offer useful information to both service providers and cloud providers for their service launching and profit estimation. To the best of our knowledge, the IsV2C is the first work that presents an integrated road traffic-network-cloud simulation framework for an end-to-end V2C service evaluation.

Design and Optimization for Energy-Efficient Cooperative MIMO Transmission in Ad Hoc Networks

The need to reduce energy consumption for lowering operating costs has pushed energy efficiency to become one of the major issues of current research in the field of ad hoc networks. In this paper, a new cooperative strategy of multiple-input–multiple-output (MIMO) based on spatial modulation (SM) for the randomly distributed nodes (CMIMO-SMR) in an ad hoc network is proposed to optimize the whole energy consumption of the network. In this new strategy, the head node and the assistant node are jointly set up using a cooperative technique in each cluster to obtain the diversity. In this strategy, the effect of the amount of nodes on the energy consumption is analyzed. Moreover, the different factors such as number of hops and bit error ratio (BER) for energy savings are investigated in a CMIMO-SMR-based multihop ad hoc network where the optimal number of hops and the BER relationship are derived by taking into account the transmission energy and the circuit energy, as well as the bit-recovery situation. In the simulation, it is demonstrated that CMIMO-SMR is more energy efficient compared with the existing works. Moreover, an adaptive algorithm for choosing the appropriate number of hops to minimize the energy consumption is designed when the end-to-end designated BER is required. The results demonstrate that the minimum energy consumption can be achieved by using the proposed algorithm without compromising the designated BER requirement at the destination.

Effect of hot pressing on the modulated structure of Zr0.98Sn0.02TiO4

Abstract With the use of X-ray diffraction and neutron scattering, the effect of hot pressing on the modulated structure in Zr0.98Sn0.02TiO4 was investigated in order to obtain information concerning the nature of the competing forces that bring about a structural instability at a general wave-vector. It was found that an increase in pressure lowers the normal-to-incommensurate and incommensurate-to-commensurate transitions (dT i/dP i ≈ −7.1K kbar−1 and dT c/dP c ≈ −8.8 K kbar−1 respectively). The latter transition displays a distinct hysteresis.

A Cost-Effective VM Offloading Scheme in Hybrid Cloud Environment

Video streaming service is offered by various content provider with cloud content delivery network like a Netflix, Youtube. In this environment, for content deliver, cache servers need to be placed properly in cost-effective manner with guaranteeing streaming performance. In this paper, as contents providers, to minimize the cost of using public cloud and to maximize performance of video streaming service, we suggest cost-effective VM offloading algorithm in hybrid cloud environment (CVOH). The CVOH considers performance degradation in internal cloud and cost for public cloud using penalty cost model and learning curve model, respectively. As the result of evaluation for CVOH, we got about twice better performance than a maximal consolidation case, and 9.1 % better than a maximal offloading case.

A Prospective Cloud-Connected Vehicle Information System for C-ITS Application Services in Connected Vehicle Environment

In the era of the Internet of Things (IoT), various applications providing people with utilities are rapidly emerging by the needs for people. Recently, combining cloud computing, IoT technologies, and vehicular applications promotes Intelligent Transportation System (ITS). In other words, this is for safety of vehicles and drivers as well as convenience of the drivers. Vehicular Ad-hoc Network (VANET) is an application of Mobile Ad-hoc Network (MANET), which is a networking technology including vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) using wireless communications. In real life, vehicles and infrastructures which have a lot of sensors generate various data for Cooperative-Intelligent Transportation System (C-ITS) application services according to each sensor type. Therefore, collecting, processing, and storing a number of data generated from various sensors built in vehicles and infrastructures require a great computing capacity and storage resources. In this paper, we propose an architecture of prospective cloud-connected vehicle information system for C-ITS application services in connected vehicle environment and describe the procedure of our local and global vehicle information system concerned with case scenario.