Hwantae Kim

Implementing home energy management system with UPnP and mobile applications

The power grid is undergoing a revolution and modernization through integrating information and communication technologies with the power system and also installing new electricity system technologies. Distributed controls in a certain self-reliant power-service area are critical means to modernize the power system to be the Smart Grid. Since the self-reliant area is assumed to perform physical and/or expert-engineered operations that should be integrated, monitored and controlled by a computational cyber system, the area is one area where the cyber and physical systems interact together, and home in the Smart Grid is one example for the area. In this paper, we propose a home energy management system (HEMS) to realize full automation combining computational and physical systems in a home area, which excludes operator-based control and management. The proposed system is designed to be built on the Universal Plug-and-Play architecture, and it can be accessed remotely over the Internet via mobile applications that work in Apple iPhone. Based on the design, we actually implemented the HEMS and constructed an empirical testbed that consists of networked personal computers, home appliances, and portable wireless devices. With the empirical testbed, we verified the monitoring and controlling functions of the HEMS. Additionally we carried out an extensive simulation study with the measured data of power consumption and the collected data of power price in order to see the effectiveness of the proposed HEMS. We also discuss about some limitations and challenges that we have encountered in designing and implementing the HEMS.

AFAR: A robust and delay-constrained communication framework for smart grid applications

Abstract The existing electrical grid is now experiencing a revolutionary change to a new paradigm, i.e., smart grid, due to the development of information and communication technologies. Communications among smart grid components such as sensors, intelligent electronic devices (IED), and smart meters of automatic metering infrastructure (AMI) are some of the key components to successfully build smart grid. To reduce installation costs and spatial limits, wireless communications are considered as effective communication techniques in smart grid. However, severe wireless interference due to the electromagnetic wave generated by electronic devices, and strict requirements of smart grid applications such as delay-constraint, short delay, reliability, and scalability are making existing network protocols inappropriate for smart grid applications. In this paper, we propose AFAR to provide robust and delay-constrained communication services to smart grid applications while satisfying their requirements successfully. This paper includes a detailed description of the framework, mathematical modeling, OPNET simulation, and co-simulation between OpenDSS and OPNET to evaluate AFAR under the specific smart grid application scenario.

A simulation study on Map/Reduce framework in wireless data center environment

Big data has different characteristics from the traditional data. It has large volume and various type and requires real-time processing. To process the big data, cluster based parallel and distributed computing model, Map/Reduce has been introduced. The Map/Reduce is basically designed for the cluster where the processing units are connected to each other with wired network, called data center. However, in the future, the wireless data center would be introduced since it has low installation and management complexity and cost. To introduce the wireless data center, we need to answer the fundamental question, “How does Map/Reduce framework would operate in the wireless data center?” To answer the question, in this paper, we perform simulation study of the Map/Reduce application in the wireless environment. We introduce the basic simulation model and the results of the simulation study to verify the potential of the wireless data center.

Microscale Analysis on Sensing Devices and Its Impact on Assessing User Mobility

Popular location-based services through smart-phones and other portable devices have brought the tracking of user mobility to the attention in wireless community and have increased its importance continuously. Although the incremental development of GPS technology made the measurement of speed and location of the device more accurate, speed itself cannot fully express the mobility and therefore limits its use in Human and Computer Interaction (HCI). HCI makes user-oriented services possible by interacting computing devices with an user through certain types of I/Os such as keyboards, touch pads and various sensors. It is true that the location and speed of user provides fundamental mobility information for service generators in the world of HCI, but now it is time to give a little deeper aspect of giving user mobility beyond the term speed. In this paper, we scrutinize sensing device motility resulted from human motion and its impact on user mobility estimation, called mobility state, in order to provide conceptual and comprehensive means of mobility including speed. Then we propose Device & User mobility Tracking Algorithm (DUTA) that accurately assess the mobility state without incurring unnecessary power consumption.

Towards cosimulating network and electrical systems for performance evaluation in smart grid

In this paper, we construct a novel simulation framework OOCoSim which can simulate the distribution domain of Smart Grid. OOCoSim consists of OPNET, OpenDSS and CoSim module and it can perform dynamic and organic cosimulation. In order to present the effectiveness of OOCoSim, we firstly define a simulation model and then conduct a simulation study with the OOCoSim. The simulation results shows that OOCoSim can successfully simulate the integrated scenario of the power and network systems.

ReMA: Real-time 3D video streaming system for mobile devices

Users multimedia interaction is facing a paradigm shift from 2D to 3D videos. Nonetheless, it is still difficult to watch 3D videos with a mobile device. With current technological barrier in wireless networking, it is hardly imagined that the timely transmission for a 3D video streaming could be feasible with the mobile device. In this paper, we propose ReMA, a novel 3D video distribution system based on a lightweight compression, a linkadaptive transmission scheme, and a network-side assistance for processing capability. ReMA consists of a 3D data transmitter, a receiver, and an infrastructure for generating and distributing 3D videos. We implemented the proposed system in a real testbed and conducted a thorough empirical evaluation study. Based on the empirical results, the proposed system presents a great promise in streaming 3D video in real-time to the mobile device.

Protecting Download Traffic from Upload Traffic over Asymmetric Wireless Links

Many varied mobile device networks have been developed with the advancement of communication and network technologies. Cellular data networks are currently the most widely used, and the number of cellular network subscriptions has increased steadily. Most recent wireless access technologies employ asymmetric uplinks and downlinks because mobile subscribers usually download contents from the Internet. Therefore, most cellular network service providers allocate more bandwidth to downlinks than uplinks for mobile subscribers. However, this asymmetry can have unexpected influence on network performance, particularly TCP performance. When the uplink interface is congested, TCP ACK packets are delayed by TCP data packets on the uplink, causing considerable TCP retransmissions on the downlink channel. Thus, downlink bandwidth cannot be fully utilized, which results in significantly degraded downlink throughput. To resolve this problem, this paper proposes a feedback scheme, network traffic chunk regulator (NCR). We analyzed the aforementioned problem through the empirical study, and we designed and implemented NCR based on the analysis. NCR adaptively controls TCP according to the degree of link usage asymmetry. We evaluate NCR performance through simulations and experiments with real devices. We verify that the proposed scheme allows the downlink traffic to not interfere with the aggressive uplink traffic. Thus, NCR increases total link utilization and aggregated throughput significantly, without imposing additional overhead on base or mobile stations.

Self-configuring topology switch in smart home network

Smart home technology frees us from all the hard work in the home and enables us to live in an efficient and convenient residential environment. To fully take advantage of smart home, various household information, especially home environment information and users living patterns, are collected, processed and exploited at the environment. A sensor and actuator network, which is usually constructed in a mesh topology, has been usually deployed to collect these information. In this paper, we propose a self-configuring, self-regulating topology switch algorithm for such the network, so that the resulting network provides a personalized environment for users. To construct this algorithm, we selected some parameters that reflect homes environmental property and users propensity. We then conducted a simulation study with some scenarios which can be observed in real smart home to verify the proposed algorithm. Simulation results show that the algorithm can improve both the network connectivity and efficiency, and provide personalized home environment for users.