Sungchang Lee

Spanning tree based topology configuration for multiple-sink Wireless Sensor Networks

Wireless Sensor Networks (WSNs) collect data (e.g. temperature, moving, humidity) from several energy-constrained sensor nodes and relay it to a single sink node. Therefore, the energy resource of the sensor nodes should be managed efficiently to prolong network lifetime. A single sink node topology is simple to implement and most of the researches assume a single sink node, but, as the number of sensor node increases, it has disadvantages to cope with some problems. For example, unexpected situations such as node failure or irregular power consumption in bottleneck can cause network partitions and energy-hole problems. In this paper, we assume a multiple-sink network, and propose a topology configuration scheme that automatically reconfigure in case of node failures. The performance of the proposed tree configuration scheme is evaluated by simulations.

N-Screen Aware Multicriteria Hybrid Recommender System Using Weight Based Subspace Clustering

This paper presents a recommender system for N-screen services in which users have multiple devices with different capabilities. In N-screen services, a user can use various devices in different locations and time and can change a device while the service is running. N-screen aware recommendation seeks to improve the user experience with recommended content by considering the user N-screen device attributes such as screen resolution, media codec, remaining battery time, and access network and the user temporal usage pattern information that are not considered in existing recommender systems. For N-screen aware recommendation support, this work introduces a user device profile collaboration agent, manager, and N-screen control server to acquire and manage the user N-screen devices profile. Furthermore, a multicriteria hybrid framework is suggested that incorporates the N-screen devices information with user preferences and demographics. In addition, we propose an individual feature and subspace weight based clustering (IFSWC) to assign different weights to each subspace and each feature within a subspace in the hybrid framework. The proposed system improves the accuracy, precision, scalability, sparsity, and cold start issues. The simulation results demonstrate the effectiveness and prove the aforementioned statements.

A Network and Visual Quality Aware N-Screen Content Recommender System Using Joint Matrix Factorization

We propose a network and visual quality aware N-Screen content recommender system. N-Screen provides more ways than ever before to access multimedia content through multiple devices and heterogeneous access networks. The heterogeneity of devices and access networks present new questions of QoS (quality of service) in the realm of user experience with content. We propose, a recommender system that ensures a better visual quality on users N-screen devices and the efficient utilization of available access network bandwidth with user preferences. The proposed system estimates the available bandwidth and visual quality on users N-Screen devices and integrates it with users preferences and contents genre information to personalize his N-Screen content. The objective is to recommend content that the users N-Screen device and access network are capable of displaying and streaming with the user preferences that have not been supported in existing systems. Furthermore, we suggest a joint matrix factorization approach to jointly factorize the users rating matrix with the users N-Screen device similarity and program genres similarity. Finally, the experimental results show that we also enhance the prediction and recommendation accuracy, sparsity, and cold start issues.

Efficient Energy Flight Path Planning Algorithm Using 3-D Visibility Roadmap for Small Unmanned Aerial Vehicle

This paper presents the flight path planning algorithm in a 3-dimensional environment with fixed obstacles for small unmanned aerial vehicles (SUAVs). The emergence of SUAVs for commercial uses with low-altitude flight necessitates efficient flight path planning concerning economical energy consumption. We propose the visibility roadmap based on the visibility graph approach to deal with this uprising problem. The objective is to approximate the collision-free and energy-efficient flight path of SUAVs for flight missions in a considerable time complexity. Stepwise, we describe the construction of the proposed pathfinding algorithm in a convex static obstacle environment. The theoretical analysis and simulation results prove the effectiveness of our method.

Extensible privacy framework for Web of objects based ubiquitous services

The paper presents an extensible privacy framework for Personal Identifiable Information (PII) in Web of Objects (WoO) based ubiquitous services. WoO enables every physical object, communication and web connectivity to produce and consume the information. WoO based ubiquitous services provides efficient control management of smart devices from anywhere and at anytime. The ubiquitous and pervasive services attract users to improve the comfort level of their daily lives, but meanwhile the environment is highly prone to the leakage and breaches of user PII. The paper proposes extensible, interoperable and flexible privacy framework architecture of WoO based ubiquitous services to control the release of user PII to other users and 3rd party service providers. We suggest PII ontology for dynamic adaptation of user PII, privacy settings ontology for extensibility and flexibility of user privacy settings control, and eXtensible Access Control Markup Language (XACML) based privacy policies and consent management to provide the interoperability among different vendors. Furthermore, the architecture is based on REST for lightweight and high performance. We also present the service scenarios of user PII collection, and disclosing to another user or 3rd party service providers.

Hierarchical control structure for provisioning N-screen services in mobile operator network

In this paper, we propose hierarchical control architecture and request routing mechanisms to support N-Screen services and mobility of both sources and devices in heterogeneous networks. N-Screen services enable users to manage their active sessions among multiple devices having different capabilities, access networks and locations. To support N-Screen services in mobile operator networks, we introduce new functions that maintain the list of active devices with their sessions and network parameters for efficient N-Screen session management. The system supports the terminal and personal mobility of both the sources and devices without affecting the overall multicast connections and minimizes the service disruption. We propose a hierarchical structure for request routing and content sharing that tries to add a user to an active session locally first. The system offloads the backhaul and core networks traffic by localized session adaptation and sharing and improves the scalability issue of existing centralized mobile network architecture. We focus on the physical placement of the new nodes and mechanisms for request routing. Simulation results show that the use of hierarchical adaptation nodes in mobile operator networks can significantly reduce network latency and traffic, and improve the system throughput.

N-Screen Smart TV contents personalization system using adaptive hybrid similarity approach

In this paper, we propose N-Screen Smart TV contents personalization system. The N-Screen Smart TV provides contents to user multiple devices having different Codec, bit rate and display format at the different location and time. The proposed system considers user N-Screen device attributes and current access network speed for visual perceptual quality on the user device, and ensure that user device is capable to display with his preferences. Furthermore, we present a novel similarity method using user rating variation to improve the accuracy of the collaborative filtering. In addition, we suggest a weight-based adaptive hybrid similarity to combine collaborative and content-based filtering. The proposed system ensures that current access network is capable to stream and recommended contents have high visual quality on the user device, and improve the accuracy, cold start issue and sparsity.

A multicriteria adaptive opportunistic treecast routing protocol for multimedia dissemination in vehicle-to-vehicle telescreen

This paper presents vehicle-to-vehicle telescreen (VVT) and a multicast scheme to disseminate digital signage multimedia services to vehicular ad hoc networks (VANETs). Multimedia dissemination in VANETs is challenging because of the high packet losses (PLs), delays and longer disconnection times, which degrade the network quality of service (QoS) and user quality of experience (QoE). To reduce the PLs and delays, most existing multimedia multicast schemes in VANETs primarily select routes based on longer route expiration times (RET) or lowest path delays. The RET-based schemes suffer less from PLs when there are fewer active multicastings in the network. When the number of active multicastings increases, delay-based schemes suffer less from PLs comparatively. This tradeoff implies to design an adaptive mechanism by mutually complementing the RET-based and delay-based schemes to reduce PLs and delays. In this paper, we propose a multicriteria adaptive opportunistic treecast routing protocol (MAOTRP), which adapts the route selection mechanism according to active multicastings for efficient multimedia dissemination in VVT. The MAOTRP adjusts the weights of route selection parameters, including RET and delays, by considering their contribution in improving packet delivery ratio. MAOTRP extends a tree-based multicast protocol to provide robustness through alternate routes for link failures to reduce PLs. Through several experimental evaluations, we show that the proposed dissemination scheme improves QoS and QoE, and reduces the average disconnection time.

A MOGA-Markov chain optimized ranking algorithm for wireless access networks in heterogeneous environment

The mounting customer demands for bandwidth-desirous services are deriving for a cost effective, robust, and high capacity wireless access network. The end users expect a satisfactory and economical delivery of “Quad-play” applications (voice, video, data, and mobility) and rich-media applications (multimedia, interactive gaming, and meta-verse) over the wireless network. In last two decades, a remarkable evolution of wireless networks is observed. Moreover, after the advent of software defined radio enabled wireless sets, the selection of the optimum wireless access network for different applications (live video streaming, online gaming voice calling and browsing) is gaining vital importance. In this paper, a ranking algorithm based on Markov chain optimized learning approach is formulated for the heterogeneous environment. The algorithm is designed on the basis of most important Quality of Service (QoS) parameters like throughput, delay/error and cost. The proposed technique is robust against the change in number of available networks where, previously proposed techniques TOPSIS, VIKOR and RafoQ are unable to handle the change in available networks adequately. The Simulation results verify the selection of optimal access network for varying applications conforming to defined ranking algorithm.

Session Management and Control Architecture for N-Screen Services

Abstract In this paper, we propose a session management and control architecture for N-Screen services, which enable users to change devices and transfer contents among user’s devices during service by session transfer and split. In N-Screen services, users may have multiple devices with different attribute such as screen resolution, CPU capability and access network interfaces. Also, since users may change devices during service, or one user may use multiple stream, N-Screen services need to enable the user to share and transfer contents across N-Screen devices. We introduce the management and control servers to provide session split over user multiple devices and session continuity while changing device. Furthermore, the proposed architecture provides the device capabilities aware session continuity. In addition, the proposed scheme minimizes the session transfer delay and content server processing load. We present results that show the effectiveness and usefulness of proposed architecture.