Suk Kyu Lee

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.

Poster: A Multi-Drone Platform for Empowering Drones' Teamwork

The rapid development of UAV technology has opened up numerous applications. Further, cooperating drones\footnote{In this paper, we refer to all types of UAVs as drones.} possess a great potential in various areas of applications. Yet, there has not been a platform for a fleet of drones. It is rather difficult to control multiple drones through a single ground control station. In fact, drones need to consistently exchange flight information to maintain the formation of the fleet and follow the commands given from the GCS. Thus, drones need a robust network established among the fleet to provide a fleet control. In this paper, we propose Net-Drone, a multi-drone platform for applications that require cooperation of multiple drones. Net-Drone is equipped with strong network functionalities to provide a control system for a fleet of drones. Through case studies conducted with a prototype implementation, the proposed system is demonstrated. Video of the conducted case study can be found in http://youtu.be/lFaWsEmiQvw.

Enabling location-aware quality-controlled access in wireless networks

Location-based services (LBSs), such as location-specific contents-providing services, presence services, and E-911 locating services, have recently been drawing much attention in wireless network community. Since LBSs rely on the location information in providing services and enhancing their service quality, we need to devise a framework of directly using the location information to provide a different level of service differentiation and/or fairness for them. In this paper, we investigate how to use location information for QoS provisioning in IEEE 802.11-based Hot Spot networks. Location-based service differentiation is different from existing QoS schemes in that it assigns different priority levels to different locations rather than flows or stations and schedules network resources to support the prioritized service levels. In order to realize such the location-based service differentiation, we introduce the concept of per-location target load to simply represent the desirable rate of traffic imposed to the network, which is dynamically changing due to the number of stations. The load consists of per-location load, which directly quantifies per-location usage of link capacity, and network-wide load, which indirectly calibrates the portion of per-location load contributed to the network-wide traffic. We then propose a feedback framework of provisioning service differentiation and/or fairness according to per-location target load. In the proposed framework, the load information is feedback to traffic senders and used to adjust their sending rate, so that per-location load does not deviate from a given per-location share of wireless link capacity and lays only tolerable traffic on the network in cooperation with other locations. We finally implemented the proposed framework in ns-2 simulator and conducted an extensive set of simulation study so as to evaluate its performance and effectiveness. The simulation results indicate that the proposed framework provides location-based service differentiation and/or fairness in IEEE 802.11 Hot Spot networks, regardless of the number of stations in a location, traffic types, or station mobility.

FASE: Fast authentication system for e-health

For the past few decades, it is common to observe the patients paper work at the local hospital. Even though the same personal information is used, a novel way to actually decrement the amount of these paper works does not exist. In this paper, we introduce QR code based e-health authentication system to reduce the redundant paper work and obtain patients health record easily and securely in the local hospital. With our proposed scheme, we believe that it will improve efficiency in terms of the cost and time for both patient and the hospital and protect patients personal information.

Link-Aware Reconfigurable Point-to-Point Video Streaming for Mobile Devices

Even though people of all social standings use current mobile devices in the wide spectrum of purpose from entertainment tools to communication means, some issues with real-time video streaming in hostile wireless environment still exist. In this article, we introduce CoSA, a link-aware real-time video streaming system for mobile devices. The proposed system utilizes a 3D camera to distinguish the region of importance (ROI) and non-ROI region within the video frame. Based on the link-state feedback from the receiver, the proposed system allocates a higher bandwidth for the region that is classified as ROI and a lower bandwidth for non-ROI in the video stream by reducing the videos bit rate. We implemented CoSA in a real test-bed where the IEEE 802.11 is employed as a medium for wireless networking. Furthermore, we verified the effectiveness of the proposed system by conducting a thorough empirical study. The results indicate that the proposed system enables real-time video streaming while maintaining a consistent visual quality by dynamically reconfiguring video coding parameters according to the link quality.

A Collaborative Framework of Enabling Device Participation in Mobile Cloud Computing

Cloud Computing attracts much attention in the community of computer science and information technology because of resource efficiency and cost-effectiveness. It is also evolved to Mobile Cloud Computing to serve nomadic people. However, any service in Cloud Computing System inevitably experiences a network delay to access the computing resource or the data from the system, and entrusting the Cloud server with the entire task makes mobile devices idle. In order to mitigate the deterioration of network performance and improve the overall system performance, we propose a collaborative framework that lets the mobile device participate in the computation of Cloud Computing system by dynamically partitioning the workload across the device and the system. The proposed framework is based on it that the computing capability of the current mobile device is significantly enhanced in recent years and its multi-core CPU can employ threads to process the data in parallel. The empirical experimentation presents that it can be a promising approach to use the computing resource of the mobile device for executing computation-intensive tasks in Cloud Computing system.

Empowering Drones’ Teamwork with Airborne Network

We propose a unified platform for multiple unmanned aerial vehicles (UAV). Recently, the UAV technology has seen a great development. However, the capability of single drone is yet limited by its physical features. To better enhance the capability of drones, we have devised and implemented a fleet based multi-UAV platform. Our proposed platform consists of powerful network functions and enhanced control and sensing algorithms, so that a unified fleet control can be accomplished. Further, it provides a platform for applications that require multiple UAVs working together. The network functions of the proposed platform achieves a strong connectivity and robustness, and a precise relative and absolute localization enables a fleet based control system. With the help of core modules, the proposed platform achieves a well controlled fleet flight and network management.

MACoD: Mobile Device-Centric Approach for Identifying Access Point Congestion

These days, since many mobile devices support Wi-Fi, the number of Wi-Fi hotspots are increasing. At the same time, the number of places where users can use wireless LAN are increasing. Unlike the cellular network, the traffic of wireless LAN may not be distributed evenly because there is no supervisor to control the network traffic. In addition, due to the low throughput and the high packet error rate in wireless communication, the network traffic may converge at some Access Points (APs) which take a role of connecting wired and wireless communication interfaces. Therefore, congestion can easily happen at APs in wireless LAN. However, received signal strength indicator (RSSI) frequently used does not mean the network state of AP, and existing sender-based congestion detection and control protocols cannot recognize accurately where the congestion occurs. Therefore, current mobile devices continuously use the connected AP even if it is congested after the association. In this paper, we propose MACoD, the low power AP congestion detection system for mobile devices, in order to resolve aforementioned problems. Furthermore, by conducting diverse simulations, actual experiments, and power consumption analysis, we validate that MACoD can detect congestion effectively and that it is suitable for mobile devices.

CoSA: Adaptive link-aware real-time streaming for mobile devices

Programmable wireless devices which can perceive the current radio environment, decide available spectra, and dynamically change the radio access method, and networking protocols have been proposed to improve spectrum usage, interference mitigation, and connectivity. However, these transitions are currently lacking at upper layers. In this paper, we propose an upper layer cognitive system beyond channel sensing effectiveness and spectrum utilization achieved in adjusting PHY and MAC parameter settings. The proposed cognitive video streaming system achieves end-to-end goals at an upper video layer: quality of experience, service continuity, and survivability. Based on the link state of the receiver, the proposed system identifies areas of importance in the image stream, allocates higher bandwidth for the important areas compared to the other areas which is adjusted to use the less bandwidth with CoSA encoder and decoder, and receive the link state feedback from the receiver. To further understand the CoSAs benefit, we implemented two real test-beds for the cognitive video streaming system where the one uses conventional IEEE 802.11 networking technologies and the other employs a software defined radio platform, and performed a performance evaluation study in order to see the effectiveness of the proposed scheme. The results indicate that the proposed system can dynamically change actual data rates according to SINR feedback, which results in at least 180% improvement of transmission time compared to conventional method, while maintaining PSNR range between 30 to 40 dB with eminently reduced data size.

Provisioning QoS for WiFi-enabled Portable Devices in Home Networks

Wi-Fi-enabled portable devices have recently been introduced into the consumer electronics market. These devices download or upload content, from or to a host machine, such as a personal computer, a laptop, a home gateway, or a media server. This paper investigates the fairness among multiple Wi-Fi-enabled portable devices in a home network when they are simultaneously communicated with the host machine. First, we present that, a simple IEEE 802.11-based home network suffers from unfairness, and the fairness is exaggerated by the wireless link errors. This unfairness is due to the asymmetric response of the TCP to data-packet loss and to acknowledgment-packet loss, and the wireless link errors that occur in the proximity of any node; the errors affect other wireless devices through the interaction at the interface queue of the home gateway. We propose a QoS-provisioning framework in order to achieve per-device fairness and service differentiation. For this purpose, we introduce the medium access price, which denotes an aggregate value of network-wide traffic load, per-device link usage, and per-device link error rate. We implemented the proposed framework in the ns-2 simulator, and carried out a simulation study to evaluate its performance with respect to fairness, service differentiation, loss and delay. The simulation results indicate that the proposed method enforces the per-device fairness, regardless of the number of devices present and regardless of the level of wireless link errors; furthermore it achieves high link utilization with only a small amount of frame losses.