• Journal of electromagnetic engineering and science
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• v.18 no.4
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• pp.254-260
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• 2018

In this study, we suggest an emulator for generating multiple heterogeneous interference signals in the Korean radio frequency identification/ubiquitous sensor network (RFID/USN) frequency band. The proposed emulator uses only one universal software radio peripheral to generate multiple heterogeneous interference signals more economically. Moreover, the physical and media access control parameters can be adjusted in real time using the LabVIEW program, thereby making it possible to create various time-varying interference environments easily. As an example showing the capability of the proposed emulator, multiple interference signals consisting of a frequency-hopping RFID signal and two LoRa signals with different spreading factors were generated. The generated signals were confirmed in both frequency and time domains. From the experimental results, we verified that our emulator could successfully generate multiple heterogeneous interference signals with different frequency and time domain characteristics.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.585-588
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• 2007

With several enhanced access technologies, users have many changes to select their preference access network. There are great differences between access technologies, users' need to handover from one access network to another is getting bigger. As users' need grows there are several works to archive fast handover between heterogeneous and homogeneous access networks. However traditional handover mechanisms work only on L2 or L3 have several limits that prevent fast and heterogeneous handover. To overcome those limits, IEEE 802.21 WG and IRTF MOBOPTS RG are working for developing handover mechanisms that uses L2 information on theupper layers like L3. This paper introduces two new L2 information and properties can be used to archive fast handover of mobile nodes.

• Journal of Communications and Networks
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• v.8 no.4
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• pp.442-450
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• 2006

Inter-operability between heterogeneous radio access technologies (RATs), in the sense of seamless vertical han-dover (VHO) support with common radio resource management (CRRM) functionalities, has recently attracted a significant research attention and has become a prominent issue in standardization fora. In this paper, we formulate the problem of load balancing between cooperative RAT's as a mathematical program and by trading off a pre-defined delay tolerance per request we propose a vertical handover batch processing (VHBP) scheme. To quantify the performance of the proposed VHBP scheme we compare it with a baseline processing scheme, where each VHO request is processed independently under a number of different network scenarios. Numerical investigations reveal significant net benefits of the proposed scheme compared with the baseline, both in terms of achieved load balancing levels but also with regard to the acceptance rate of the VHO requests.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.11
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• pp.5203-5217
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• 2018

In order to increase the capacity and improve the spectrum efficiency of wireless communication systems, this paper proposes a rate-based two-sided many-to-one matching game algorithm for energy-harvesting small cells with non-orthogonal multiple access (NOMA) in heterogeneous cellular networks (HCN). First, we use a heuristic clustering based channel allocation algorithm to assign channels to small cells and manage the interference. Then, aiming at addressing the user access problem, this issue is modeled as a many-to-one matching game with the rate as its utility. Finally, considering externality in the matching game, we propose an algorithm that involves swap-matchings to find the optimal matching and to prove its stability. Simulation results show that this algorithm outperforms the comparing algorithm in efficiency and rate, in addition to improving the spectrum efficiency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.11
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• pp.4595-4610
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• 2020

In the practical communication environment, the accurate channel state information (CSI) is difficult to obtain, which will cause the mismatch of resource and degrade the system performance. In this paper, to account for the channel uncertainties, a robust power allocation scheme for a downlink Non-orthogonal multiple access (NOMA) heterogeneous network (HetNet) is designed to maximize energy efficiency (EE), which can ensure the quality of service (QoS) of users. We conduct the robust optimization model based on worse-case method, in which the channel gains belong to certain ellipsoid sets. To solve the non-convex non-liner optimization, we transform the optimization problem via Dinkelbach method and sequential convex programming, and the power allocation of small cell users (SCUs) is achieved by Lagrange dual approach. Finally, we analysis the convergence performance of proposed scheme. The simulation results demonstrate that the proposed algorithm can improve total EE of SCUs, and has a fast convergence performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.1
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• pp.35-57
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• 2014

Multi-criteria decision making (MCDM) algorithms play an important role in ensuring quality of service in an integrated HetNets (Heterogeneous Networks). The primary objective of this paper is to develop a multi-criteria vertical handoff decision algorithm (VHDA) for best access network selection in an integrated Wireless Local Area Network (WLAN)/Universal Mobile Telecommunications System (UMTS)/Worldwide Interoperability for Microwave Access (WiMAX) system. The proposed design consists of two parts, the first part is the evaluation of an Analytic Hierarchy Process (AHP) to decide the relative weights of handoff decision criteria and the second part computes the final score of the weights to rank network alternatives using Simple Additive Weighting (SAW). SAW ranks the network alternatives in a faster and simpler manner than AHP. The AHP-SAW mathematical model has been designed, evaluated and simulated for streaming video type of traffic. For other traffic type, such as conversational, background and interactive, only simulation results have been discussed and presented in brief. Simulation results reveal that the hierarchical modelling and computing provides optimum solution for access network selection in an integrated environment as obtained results prove to be an acceptable solution to what could be expected in real life scenarios.

• Journal of Communications and Networks
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• v.3 no.4
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• pp.317-323
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• 2001

Traditional configuration management involves complex labor-intensive processes performed by experts. The configuration tasks such as installing or reconfiguring a system, provisioning network services and allocating resources typically involve a large number of activities involving multiple network elements. The network elements may be associated with proprietary configuration management instrumentation and may also be spread across heterogeneous network domains thereby increasing the complexity of configuration management. This paper introduces an architecture for the self-configuration of networks (SELFCON). The proposed architecture involves a directory server, which is uses to maintain configuration information. The configuration information stared in the directory server is modeled using the standard DEN specification thereby allowing effective exchange of network, system and configuration management data among heterogeneous management domains. SELFCON associates configuration intelligence with the components of the network, rather than limit it to a centralized management station. The network elements are notified about related changes in configuration policies, based upon which, they perform self-configuration. SELFCON is able to provide automation of configuration management and also an effective unifying framework for enterprise management.

• Journal of Advanced Navigation Technology
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• v.10 no.1
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• pp.34-40
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• 2006

Multiple wireless devices in wired and wireless heterogeneous networks communicate with counterparts via a single Access Point (AP). In this case, the AP becomes a bottleneck of the network, therefore buffer overflows occur frequently and result in TCP performance degradation. In this paper, the new algorithm that prevents buffer overflows at AP and enhances TCP fairness is proposed. Depending on the buffer usage of AP, the new algorithm adaptively controls each TCP senders' transmission rate, prevents buffer overflows and thus guarantees improved TCP fairness. It is proved that the algorithm makes better of TCP throughput and fairness by preventing buffer overflows.

• Journal of KIISE:Information Networking
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• v.34 no.5
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• pp.405-422
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• 2007

Recently, according to the network environment, there are many researches for home network. Nowadays, in home network, the method that access control policy is managed for each home device by using ACL is popular, and EAM (Extranet access management) is applied as a solution. In addition, the research about secure OS is ongoing based on open operating system and the research of user authentication mechanisms for home network using home server is also in progress. However, these researches have some problems as follows; First, the transmission scope of expected access technology in home network is wide, so unauthenticated outside terminal can access the home network. Second, user is inconvenient because user need to set the necessary information for each device. Third, user privacy and convenience are not considered. OSGi provides a service platform for heterogeneous technologies in home network environment. Here, user access control is one of the core parts which should have no problems such as above items, but there are no concrete researches yet. Thus in this paper, we propose an access control policy management framework and access control operation based on RBAC for user access control in home network environment in which OSGi service platform is operated. First, we list the consideration which is not clearly mentioned in OSGi standard, and then we solve these above problems through new framework. In addition, we propose the effective and economical operation method which reduces the policy change frequency for user access control by using RBAC concept though limited resource of home gateway. Besides, in this paper, these proposed policies are defined separately as user-role assignment policy and permission-role assignment policy, and user decide their own policies. In conclusion, we provide the scheme to enhance the user convenience and to solve the privacy problem.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7B
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• pp.710-720
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• 2009

The Future Generation Networks(FGNs) are proposed to integrate various heterogeneous access technologies, and further expected to support both vertical and seamless handovers. In this motivation, the IEEE 802.21 specifies Media Independent Handover(Mlli) services to enhance the mobile user experience by optimizing handovers between heterogeneous access networks. Additionally, Fast handover for MIPv6(FM1Pv6) is introduced to provide transparent host mobility and to improve handover performance by reducing handover delay as well. This paper focuses on the coordination of FMIPv6 and MIH, and introduces an enhanced mobility management framework suited for FGN. This novel framework replaces handover signaling messages used in wireless networks with novel MIH messages and local primitives. Moreover, Serving Access Router(SAR) performs most of handover processes instead of Mobile Node(MN). Therefore, the proposed mobility management framework reduces handover latency, packet loss, and signaling overhead significantly. We further evaluate the performance of the proposed framework by using both numerical analysis and network simulations.