Ki-Sook Chung

Adaptive Resource Balancing for Serviceability Maximization in Fog Radio Access Networks

Serviceability is the ability of a network to serve user equipments (UEs) within desired requirements (e.g., throughput, delay, and packet loss). High serviceability is considered as one of the key foundational criteria toward a successful fog radio access infrastructure satisfying the Internet of Things paradigm in the 5G era. In this paper, we propose an adaptive resource balancing (ARB) scheme for serviceability maximization in fog radio access networks wherein the resource block (RB) utilization among remote radio heads (RRHs) are balanced using the backpressure algorithm with respect to a time-varying network topology issued by potential RRH mobilities. The optimal UE selection for service migration from a high-RB-utilization RRH to its neighboring low-RB-utilization RRHs is determined by the Hungarian method to minimize RB occupation after moving the service. Analytical results reveal that the proposed ARB scheme provides substantial gains compared with the standalone capacity-aware, max-rate, and cache-aware UE association approaches in terms of serviceability, availability, and throughput.

Communication and Collaboration Service Components for Ubiquitous Communication Applications

Over the past decades we have undergone a series of significant evolution in the computing and communication technologies and have experienced better quality of life. Among these evolutions, the mobile device technology has changed the life-style of people significantly and made new business opportunities. Especially, the widespread use of smartphones accelerates to make ubiquitous communication world. It is needed to apply new technology to the legacy system rapidly and to introduce new applications to the market based on the new functions quickly. This paper describes the Converged Service Platform which provides a playground of applications for application providers, and introduces service components for a ubiquitous communication and collaboration working environment. The Converged Service Platform is designed to support the process of service delivery mechanism which consists of service creation, service execution, and service management based on the Service-Oriented Architecture. The platform focused on supporting communication and collaboration functionalities in the form of service components to make ubiquitous working environment. The service components utilize various communication means such as e-mail, short message, messengers, wired or wireless telephone call and even social network services, and give knowledge sharing functionalities such as file cloud, wiki and etc.

An Interworking Mechanism between SCFs and Protocols in the Open Service Gateway

One of the important key aspects of NGN is the separation of service control and provision from the underlying network. Considering the evolution of customer requirements for converged services, opening up the network capabilities is inevitable. Open interfaces such as Parlay/OSA and Parlay X API enable third party service providers to develop communication services without specific knowledge of the underlying network. Open service gateway provides open APIs which abstract network capabilities such as call control, presence, terminal location, multimedia messaging, and etc for application developers. Each interface is implemented in the form of SCF (service feature capability) in the gateway. Since open service gateway interacts with NGN which is broadband convergence network, it should process more than one network protocol. During processing a protocol message in the gateway, it is necessary to find the target SCF which is supposed to receive that message. In this paper, a mechanism including appropriate data structure to find and dispatch protocol messages, especially SS no.7 protocol messages, from the underlying network in the open service gateway is proposed

Performance analysis of manifold learning methods for radio map construction

Wifi fingerprinting is an appealing method for indoor positioning as it can utilizes available wireless infrastructures while retaining an acceptable level of accuracy. For the method to work, radio map of target environment has to be constructed in advance. The process is laborious and time consuming as signal strength has to be collected from mobile devices at a large number of reference locations. An attractive idea is to harness unlabeled wireless signal data from crowd to help construct the radio map. Various manifold learning methods have been employed for this purpose. However, results are not comparable as they are highly dependent on experiment environment. In this works, we implement four different manifold learning methods for the radio map construction task and report the localization performance of the resulting map on a simulated data and a public real dataset.

Wifi Fingerprint Calibration Using Semi-Supervised Self Organizing Map

무선 RSSI fingerprinting 방식은 기존 무선 인프라를 이용하면서 적정수준의 정확도를 얻을 수 있는 실내위치 인식 방법 중의 하나이다. 하지만 라디오 맵 구성( fingerprint calibration) 과정에서 목표 환경의 다양한 위치에서 정확한 물리적 좌표와 무선 신호를 측정해야 하므로 시간과 노력이 많이 소요된다. 이 논문은 이러한 방식으로 위치 정보를 수집하지 않고 반지도식 자기조직화지도 학습 알고리즘을 사용하여 labeled RSSI를 얻고 RSSI 조합으로부터 맵을 구성하는 방법을 제안한다. 모의 데이터에 대한 실험을 통해 제안 방법이 fingerprint 데이터베이스로 부터 1%의 RSSI 샘플을 가지고 효과적인 전체 맵을 얻을 수 있다는 결론을 얻었다.

A design of smart docent service using hybrid recommenders

E-commerce companies such as Amazon.com and Netflix have been introducing recommendation techniques to attract their customers on their web sites. At Amazon.com, they use recommendation algorithms to personalize the online store for each customer. Many applications collect customers interests to generate a list of recommended items. We introduce recommendation algorithms to smart docent service which guides the visitor considering his preference and other conditions such as his location in museums or art galleries. We use a hybrid approach which combines item-item collaborative filtering and demographical recommendation.

Design of dynamic SNS on the high-speed railway: Virtual crew service

In the high-speed train, passengers want infotainment services which provide users with useful information about the area they are passing by, or information about their destination. This paper introduces dynamic SNS for train application which enriches user experiences with ad-hoc group chatting, contents sharing, recommendation based on user preference and location, and train environment information. The virtual crew service is one example of the dynamic SNS. Users can query about train environment and get information about location the train is passing by through the virtual crew accessed from their smartphones. To provide virtual crew service we need communication infrastructure for high-speed train. The train communication infrastructure can be one of the wireless communications technology or high-speed railway.

Mobile data offloading service using file cloud in small cells

Recently, lots of mobile operators have deployed small cells in their 3G/4G mobile networks for network densification to deal with the exponential mobile traffic growth. This paper shows a way to provide file data offloading service to mobile users by utilizing the small cell system. Users can handle files of big size on their phones interacting with the file cloud server of the near small cell. Therefore, mobile data can be offloaded from mobile core network to the small cell. In addition, the file cloud service has file expiration mechanism due to nomadic characteristics of small cell users. This paper describes how to provide file data offloading to mobile phone users through the file cloud services on small cells.

Access control management of the cloud service platform

One of the design goals of the Cloud Service Platform was to help application developers to create their applications easier by providing reusable service components in the form of web services, such as, RESTful web services or web services based on SOAP. The Cloud Service Platform is designed to target to the communication and collaboration domain so that it provides service components having functionalities such as Email, short messaging, file cloud, third-party call, wiki, and etc. Therefore application developers can utilize these service functionalities by requesting the resources using HTTP methods outside the Cloud Service Platform (CSP). Therefore, the access to service components plugged into the CSP should be managed and the authorization process for the requesting applications is needed. We specify the relationship between applications and service components using service key, which is the unique identifier for an application and a service component. In addition, we define additional HTTP headers for authorization of the requesting application and utilize these headers for access control to service components. In this paper, we introduce the Cloud Service Platform and describe the mechanism of the access control management for service components on the Cloud Service Platform.

Service Components for Unified Communication and Collaboration of an SOA-Based Converged Service Platform

Since there are lots of communication means and devices such as e-mail, short messaging, messengers, wired or wireless telephone and even social network services, we need some unified communication environment for the smarter work place. We introduce a converged service platform with open service components for the unified communication and collaboration in this paper. Using the converged service platform, the third party service providers can create applications easily by composing the open service components and execute their applications since the CSP covers the entire lifecycle of services. The CSP provides UCC (Unified Communication and Collaboration) components in the form of web services. The UCC components of the CSP cover basic communication functionalities as well as social collaboration functionalities and can be mashed up into various applications for the smart collaboration in a company.