• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권10호
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• pp.2376-2394
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• 2013

In order to ensure both of the whole system capacity and users QoS requirements in heterogeneous wireless networks, admission control mechanism should be well designed. In this paper, Multi-agent Q-learning based Admission Control Mechanism (MQACM) is proposed to handle new and handoff call access problems appropriately. MQACM obtains the optimal decision policy by using an improved form of single-agent Q-learning method, Multi-agent Q-learning (MQ) method. MQ method is creatively introduced to solve the admission control problem in heterogeneous wireless networks in this paper. In addition, different priorities are allocated to multiple services aiming to make MQACM perform even well in congested network scenarios. It can be observed from both analysis and simulation results that our proposed method not only outperforms existing schemes with enhanced call blocking probability and handoff dropping probability performance, but also has better network universality and stability than other schemes.

• Journal of Information Processing Systems
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• 제18권6호
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• pp.803-812
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• 2022

With the increasing number of mobile device users worldwide, utilizing mobile edge computing (MEC) devices close to users for content caching can reduce transmission latency than receiving content from a server or cloud. However, because MEC has limited storage capacity, it is necessary to determine the content types and sizes to be cached. In this study, we investigate a caching strategy that increases the hit ratio from small base stations (SBSs) for mobile users in a heterogeneous network consisting of one macro base station (MBS) and multiple SBSs. If there are several SBSs that users can access, the hit ratio can be improved by reducing duplicate content and increasing the diversity of content in SBSs. We propose a Deep Q-Network (DQN)-based caching strategy that considers time-varying content popularity and content redundancy in multiple SBSs. Content is stored in the SBS in a divided form using maximum distance separable (MDS) codes to enhance the diversity of the content. Experiments in various environments show that the proposed caching strategy outperforms the other methods in terms of hit ratio.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.448-450
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• 2005

A ubiquitous network allows all users to access and exchange information of any kind freely at any time, from anywhere, and from any appliance through the use of broadband and mobile access. Bluetooth commincation can provide the missing wireless extension to the heterogeneous network, allowing a more ubiquitous access. In this point of view, the BT specifications define ways for which each BT device can set up multiple connections with neighboring devices to communicate in a multi-hop fashion. this paper provides insights on the Bluetooth technology and on some limitations of the scatternet formations. so that, we describe a new multi-hop routing protocol for the establishment of scatternets. this protocol defines rules for forming a multi-hop topology in two phases. the first phase, topology discovery, concerns the discovery of the node's depth from a root node initiating inquiry process. the second phase forms scatternet topology based on the result of topology discovery.

• Journal of Communications and Networks
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• 제16권2호
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• pp.202-208
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• 2014

Wireless network information services allow end systems to discover heterogeneous networks and spectrum available for secondary use at or near their current location, helping them to cope with increasing traffic and finite spectrum resources. We propose a unified architecture that allows end systems to find nearby base stations that are using either licensed, shared or unlicensed spectrum across multiple network operators. Our study evaluates the performance and scalability of spatial databases storing base station coverage area geometries. The measurement results indicate that the current spatial databases perform well even when the number of coverage areas is very large. A single logical spatial database would likely be able to satisfy the query load for a large national cellular network. We also observe that coarse geographic divisions can significantly improve query performance.

• ETRI Journal
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• 제35권2호
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• pp.234-244
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• 2013

Internet protocol television (IPTV) service depends on the network quality of service (QoS) and bandwidth of the broadband service provider. IEEE 802.16j mobile multihop relay Worldwide Interoperability for Microwave Access networks have the opportunity to offer high bandwidth capacity by introducing relay stations. However, to actually satisfy QoS requirements for offering IPTV services (HDTV, SDTV, Web TV, and mobile TV) for heterogeneous users' requests, providers must use a video server for each IPTV service type, which increases the network load, especially bandwidth consumption and forwarding time. In this paper, we present a solution for forwarding IPTV video streaming to diverse subscribers via an 802.16j broadband wireless access network. In particular, we propose a new multicast tree construction and aggregation mechanism based on the unique property of prime numbers. Performance evaluation results show that the proposed scheme reduces both bandwidth consumption and forwarding time.

• 한국통신학회논문지
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• 제35권7B호
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• pp.1009-1017
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• 2010

Offering of different attractive opportunities by different wireless technologies trends the convergence of heterogeneous networks for the future wireless communication system. To make a seamless handover among the heterogeneous networks, the optimization of the power consumption, and optimal selection of interface are the challenging issues. The access of multi interfaces simultaneously reduces the handover latency and data loss in heterogeneous handover. The mobile node (MN) maintains one interface connection while other interface is used for handover process. However, it causes much battery power consumption. In this paper we propose an efficient interface selection scheme including interface selection algorithms, interface selection procedures considering battery power consumption and user mobility with other existing parameters for overlaying networks. We also propose a priority based network selection scheme according to the service types. MN‘s battery power level, provision of QoS/QoE and our proposed priority parameters are considered as more important parameters for our interface selection algorithm. The performances of the proposed scheme are verified using numerical analysis.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권6호
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• pp.1979-1995
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• 2015

Network convergence is regarded as the development tendency of the future wireless networks, for which self-organization paradigms provide a promising solution to alleviate the upgrading capital expenditures (CAPEX) and operating expenditures (OPEX). Self-optimization, as a critical functionality of self-organization, employs a decentralized paradigm to dynamically adapt the varying environmental circumstances while without relying on centralized control or human intervention. In this paper, we present comprehensive surveys of heterogeneous networks (HetNets) and investigate the enhanced self-optimization models. Self-optimization approaches such as dynamic mobile access network selection, spectrum resource allocation and power control for HetNets, etc., are surveyed and compared, with possible methodologies to achieve self-optimization summarized. We hope this survey paper can provide the insight and the roadmap for future research efforts in the self-optimization of convergence networks.

• 대한전자공학회논문지TC
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• 제46권5호
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• pp.146-153
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• 2009

현재, 3GPP, IETF 등에서 차세대 네트워크(NGN, Next Generation Network)에 대한 연구가 활발히 진행되고 있다. 다양한 생활 패턴에 따른 빈번한 이동성에도 불구하고, 원하는 서비스를 항상 원하는 시간, 장소에 구애받지 않고 자기가 소유하고 있는 단말을 이용하여 서비스를 받기를 원하는 사용자의 요구사항을 반영하기 위해 차세대 네트워크(NGN)는 다양해지는 어플리케이션 개발에 대응하기 위해 IMS(IP Multimedia Subsystem)가 구축되고 있으며, 또한 펨토셀/WiBro/3G등의 다양한 무선 억세스 네트워크로 구성된 계층적 네트워크 구축되고 있다. 이와 같이 무선 멀티 억세스 네트워크로 구성된 계층적 네트워크에서의 사용자가 네트워크 선택하기 위해서는 기존 무선품질 이외에 사용자 프로파일과 네트워크 부하량 등을 고려한 최적의 네트워크 선택 기준이 필요하다. 또한 핸드오버의 판단을 멀티모드 단말에서 수행하는 기존 방법 사용할 경우 발생할 수 있는 핸드오버 핑퐁현상을 억제하고, 보다 정확한 계층적 핸드오버를 수행하기 위한 방법이 필요하다. 본 논문에서는 멀티모드 단말 개발의 용이성과 다양한 억세스 네트워크의 선택 및 등록에 관한 고려사항을 검토하여, 사용자 프로파일을 반영하여 IMS를 포함한 계층적 네트워크에서의 SIP-MIH(Session Initiation Protocol-Media Independent Handover)를 기반으로 하는 무선 멀티 억세스 네트워크의 선택 기법과 계층적 핸드오버 절차에 대해 제안한다.

• 한국산학기술학회논문지
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• 제14권9호
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• pp.4492-4497
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• 2013

차세대 무선 네트워크 시스템에서 이동 단말은 다수의 무선 액세스 네트워크를 접속할 수 있는 능력을 갖는다. 이런 이기종 환경에서 네트워크 선택 메커니즘은 사용자에게 QoS를 보장해주기 위한 중요한 역할을 담당한다. 본 연구에서는 최적의 네트워크 선택을 위해 AHP 기법을 그룹결정방법에 적용한다. 특정 QoS를 요구하는 사용자들과 유사한 특성을 갖는 액세스 네트워크들을 각각 그룹으로 생각한다. 이 경우 비슷한 특성을 갖는 네트워크들을 그룹으로 묶어, 일차적으로 그룹간의 판별을 통해 적합한 그룹을 선택한 후, 그 그룹에서 네트워크 선택 알고리즘에 의한 네트워크 순위를 통해 최적의 네트워크를 선택해 주는 방법이다. 여기서 네트워크 선택 알고리즘은 결정요소의 가중치를 계산하는 AHP와 접근 네트워크의 등급을 결정하는 GRA 방법을 이용한다. MATLAB 시뮬레이션 결과, 제안된 시스템은 각 서비스 내 모든 사용자들이 0.9 이상의 높은 판정값으로 동일한 네트워크를 선택함을 알 수 있었다. 결과적으로 제안된 시스템은 WLAN과 UMTS의 통합망에서 기존시스템에 비해 효과적인 네트워크 선택 알고리즘임을 알 수 있다.

• 한국통신학회:학술대회논문집
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• 한국통신학회 2004년도 추계종합학술대회 논문 초록집
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• pp.323-323
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• 2004