• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권11호
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• pp.5229-5252
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• 2016

With proliferation of diverse network access technologies, users demands are also increasing and service providers are offering a Quality of Service (QoS) to satisfy their customers. In roaming, a mobile node (MN) traverses number of available networks in the heterogeneous wireless networks environment and a single operator is not capable to fulfill the demands of user. It is crucial task for MN for selecting a best network from the list of networks at any time anywhere. A MN undergoes a network selection situation frequently when it is becoming away from the home network. Multiple Attribute Group Decision (MAGD) method will be one of the best ways for selecting target network in heterogeneous wireless networks (4G). MAGD network selection process is predominantly dependent on two steps, i.e., attribute weight, decision maker's (DM's) weight and aggregation of opinion of DMs. This paper proposes Multi-Attribute Intuitionistic Fuzzy Group Decision Method (MAIFGDM) using TOPSIS for the selection of the suitable candidate network. It is scalable and is able to handle any number of networks with large set of attributes. This is a method of lower complexity and is useful for real time applications. It gives more accurate result because it uses Intuitionistic Fuzzy Sets (IFS) with an additional parameter intuitionistic fuzzy index or hesitant degree. MAIFGDM is simulated in MATLAB for its evaluation. A comparative study of MAIFDGM is also made with TOPSIS and Fuzzy-TOPSIS in respect to decision delay. It is observed that MAIFDGM have low values of decision time in comparison to TOPSIS and Fuzzy-TOPSIS methods.

• 한국통신학회논문지
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• 제39A권1호
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• pp.62-64
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• 2014

본 논문에서는 이종망 환경에서 펨토셀에 전력제어를 적용하면서도 매크로셀 단말이 받는 간섭의 영향을 완화하도록 펨토셀에 ABSF(Almost Blank Subframes)를 추가적으로 적용하는 경우의 성능을 분석하였다. 모의실험을 통해 제안하는 방법으로 펨토셀의 용량 증대 등 설치 목적은 달성하면서도 매크로셀 단말에 미치는 간섭의 영향을 크게 줄일 수 있음을 확인하였다. 단, 전체 네트워크의 용량은 가능한 최대 용량에 비해 소폭 감소하였다.

• 인터넷정보학회논문지
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• 제10권2호
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• pp.143-151
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• 2009

본 논문에서는 유무선 혼합 네트워크상에서 TCP 스킴을 평가하기 위해 굿풋, 굿풋 인덱스, 정규화된 굿풋 인덱스 등을 정의하였다. 이러한 메트릭스들은 주로 TCP 스킴을 측정하기 위해 사용된 성능 메트릭스와는 달리 주어진 네트워크 상황에서 목적을 달성할 수 있는 능력인 성취도 개념을 포함하고 있다.

• 한국정보기술학회 영문논문지
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• 제8권2호
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• pp.13-25
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• 2018

The paper analyzes the sum spectral efficiency (SE) for a heterogeneous cellular network (HetNet) which has the backhaul, provided with wireless full-duplex massive multiple-input multiple-out (MIMO) with hardware distortions. We derive approximate expressions to obtain the uplink/downlink sum SE of the backhaul. The analytic results have been shown to be exact when compared to Monte Carlo simulations. From the analysis, it is shown that the desired signal and the hardware distortion noise have the same order. The sum SE generally improves when the number of receive antennas increases but degrades when the hardware quality reduces. A sum SE performance ceiling is introduced by the hardware quality level.

• 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.

• 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.

• Journal of Communications and Networks
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• 제18권4호
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• pp.619-628
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• 2016

This paper describes a theoretical framework for rate allocation to maximize the power efficiency of overall heterogeneous wireless networks whose users are assumed to have multihoming capabilities. Therefore, the paper first presents a power consumption model considering the circuit power and radio transmission power of each wireless network. Using this model, two novel power efficient rate allocation schemes (PERAS) for multihoming services are proposed. In this paper, the convex optimization problem for maximizing the power efficiency over wireless networks is formulated and solved while guaranteeing the required quality of service (QoS). Here, both constant bit rate and variable bit rate services are considered. Furthermore, we extend our theoretical framework by considering the sleep-operation management of wireless networks. The performance results obtained from numerical analysis reveal that the two proposed schemes offer superior performance over the existing rate allocation schemes for multihoming services and guarantee the required QoS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권4호
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• pp.1471-1488
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• 2018

Interference mitigation is a significant issue in the cognitive heterogeneous networks, this paper studied how to reduce the interference to macrocell users (MU) and improve system throughput. Establish the interference model with imperfect spectrum sensing by analyzing the source of interference complexity. Based on the user topology, the optimize problem was built to maximize the downlink throughput under given interference constraint and the total power constraint. We decompose the resource allocation problem into subcarrier allocation and power allocation. In the subcarrier assignment step, the allocated number of subcarriers satisfies the requirement of the femtocell users (FU).Then, we designed the power allocation algorithm based on the Lagrange multiplier method and the improved water filling method. Simulation results and performance analyses show that the proposed algorithm causes less interference to MU than the algorithm without considering imperfect spectrum sensing, and the system achieves better throughput performance.

• 인터넷정보학회논문지
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• 제16권6호
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• pp.1-9
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• 2015

본 논문에서는 이기종 네트워크를 구성하는 대표 무선접속 기술인 WiMAX, CDMA, 무선랜 간의 주파수 공유 분석을 수행하였다. 3가지 접속기술은 각기 다른 주파수 대역을 사용하지만 대역외 방사특성으로 인해 타 무선접속 기술에 간섭을 일으킬 수 있다. 따라서 간섭 허용기준을 만족하기 위한 최소 인접채널 간섭률을 산출하고 이를 바탕으로 간섭/피간섭 시스템간의 최소 주파수 이격(보호대역)을 산출하였다. 분석 결과 WiMAX와 무선랜 간에는 적어도 20 MHz의 보호대역, WiMAX와 CDMA시스템 간에는 적어도 15 MHz의 보호대역이 필요함을 확인하였다.

• 한국정보과학회논문지:정보통신
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• 제36권1호
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• pp.43-49
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• 2009

표준 Mobile IPv6(MIPv6)는 이종 접속 망간 호스트 이동성을 지원할 때, 핸드오프(handoff) 시 발생하는 링크 단절과 터널 변경시점의 차이로 인해 패킷 손실을 유발한다. 다시 말해, 새로운 터널 생성과 라우팅 갱신 과정에서 추가적인 패킷 손실이 발생하게 된다. 본 논문은 이 때 발생하는 상 하향 패킷 손실을 최소화하는 Mobile IPv6기반 이원적 터널 기법을 제안한다. 그래서, UMTS 광대역 망과 WLAN 협대역 망을 이종 접속 망 모델로 설정하고, 사이에서 Mobile IPv6기반 핸드오프 시 발생하는 패킷 손실을 정량적 분석과 컴퓨터 모의실험 측정을 통해 제안 기법의 성능 향상을 입증한다.