Byung-Bog Lee

Multi-Hop Relay Based Coverage Extension in the IEEE802.16j Based Mobile WiMAX Systems

In this paper, we investigate various issues of cost- effective coverage extension in a multi-hop relay based WiBro/WiMAX systems. Since the coverage extension problem may occur in metropolitan areas as well as suburban or rural areas where user density is relatively low or moderate, we first introduce several topologies and the resulting cost-effective coverage extension methods for each case. Secondly, we propose two cost-effective coverage extension methods using two sectorized cellular approaches, one using the wide-beam tri-sector cell (WBTC) and the other using the narrow-beam tri-sector cell (NBTC). Finally, we present a practical deployment scenario consisting of three phases depending on user traffic density.

Sensor Virtualization Module: virtualizing IoT devices on mobile smartphones for effective sensor data management

The vision of the Internet of Things (IoT) is coming closer to reality as a large number of embedded devices are introduced to our everyday environments. For many commercial IoT devices, ubiquitously connected mobile platforms can provide global connectivity and enable various applications. Nevertheless, the types of IoT resource-utilizing applications are still limited due to the traditional stovepipe software architecture, where the vendors provide supporting software on an end-to-end basis. This paper tries to address this issue by introducing the Sensor Virtualization Module (SVM), which provides a software abstraction for external IoT objects and allows applications to easily utilize various IoT resources through open APIs. We implement the SVM on both Android and iOS and show that the SVM architecture can lead to easy development of applications. We envision that this simplification in application development will catalyze the development of various IoT services.

A Study on Ubiquitous Business Process Management for Real-Time Open USN Mash-Up Services

USN (Ubiquitous Sensor Network) technology is recognized as a next-generation core technology and spreads rapidly through various pilot projects. It is widely used especially in the areas such as BPM (Business Process Management) and home network. Service-oriented architecture based on mobile and web services technology provides a promising platform where the enterprises are allowed to coordinate seamlessly e-Services on the heterogeneous information systems. In this paper, we propose a new ubiquitous BPM system architecture for open USN communication that can guarantee the real-time service and mash-up service in various wireless field networks. We also illustrate the proposed architecture with a case study of a health care based on mash-up methodology.

Cost Effective Coverage Extension in IEEE802.16j Based Mobile WiMAX Systems

Recently, there have been numerous standardization activities for making the IEEE802.16e system highly effective in supporting mobile users based on orthogonal frequency division multiple access (OFDMA) with Time Division Duplex (TDD) mode in (IEEE Standard 802.16e-2005, 2005) and (WiMAX Forum). Standardization activities of the IEEE802.16e system were completed in 2005, and currently enhancements of the IEEE802.16e standard are under discussion. One such enhancement effort is cell coverage extension and link throughput enhancement which was studied in IEEE802.16j TG in (IEEE802.16j-2008, 2008). In order to achieve these goals, the IEEE802.16j TG introduces mobile multi-hop relay technology to the IEEE802.16e system. The other enhancement effort is being discussed in IEEE802.16m TG. The IEEE802.16m system, called the gigabit WiMAX, makinly aims to enhance system throughput up to 1Gbps. Besides, this system aims to support legacy IEEE802.16 standards including the IEEE802.16j, and to interworking with other wireless systems such as 3GPP LTE and IMT-advanced system in (WiMAX Forum) and (Lee et al., 2006).

Designs of a Secure Wireless LAN Access Technique and an Intrusion Detection System for Home Network

IEEE 802.11i standard supports a secure access control for wireless LAN and IEEE 802.1x standard includes various authentication method protocols. It is expected that next generation wireless LAN security techniques will be based on IEEE 802.1x and IEEE 802.11i standards. However, at present users who are not familiar with a computer and an authentication details have difficulty to setup the network security based on IEEE 802.11i. Accordingly, this paper proposes authentication scenarios to minimize the process needed by users, a password method which is changed randomly and periodically, and authentication protocols. The proposed protocols provide convenience for nonprofessional computer users as well as secure the home network environment against the unwanted attacks such as a dictionary attack or a replay attack and it uses SNMP and the system to be able to detect an intrusion it supposes will occur.

Poster abstract: virtualizing external wireless sensors for designing personalized smartphone services

By interacting with external sensors, smartphones can gather high-fidelity data on the surrounding environment to develop various environment-aware, personalized applications. In this work we introduce the sensor virtualization module (SVM) which virtualizes external sensors so that smartphone applications can easily utilize a large number of sensing resources. Implemented on the Android platform, our SVM simplifies the management of external sensors by abstracting them as virtual sensors to provide the capability of resolving conflicting data requests from multiple applications and also mashing-up sensing data from different sensors to create new customized sensors. We envision our SVM to open the possibilities of designing novel personalized smartphone applications.

A Distributed and Intelligent Power Control Scheme in LTE-Advanced Femtocell Networks

In this paper, we propose an energy efficient power control scheme, called the distributed and intelligent power control (DIPC), to increase downlink (DL) system throughput and reduce energy consumption for femtocell base station (fBS) Tx power in the LTE-Advanced femtocell networks. In the DIPC scheme, a scheduler in each fBS allocates resource blocks (RBs) with optimal Tx power obtained by the requested data rate for each femtocell user equipment (fUE). The simulation results show that the DIPC scheme outperforms the conventional fixed power (CFP) scheme which uses fixed Tx power in terms of system throughput for the macro user equipments (mUEs) and fUEs as well as energy consumption for fBS Tx power.

A Low-Power Wakeup-On-Demand Scheme for Wireless Sensor Networks

This paper proposes a wakeup-on-demand scheme based on the idea that a device should be woken just when it has to receive a packet from a neighboring device. To prove this scheme, this paper proposes a mathematical model based on the busy cycle of M/G/1 queuing systems to obtain a battery lifetime of one-hop cluster-topology shaped W-WSN. Also, we estimate the performance based on a more realistic log-normal shadowing channel model to prove the correctness of the mathematical analysis of the W-WSN with parameters such as the number of devices, the value of the wakeup period and communication distance variations.