• Journal of Intelligence and Information Systems
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• v.11 no.3
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• pp.83-101
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• 2005

Customer retention is one of the major issues in life insurance industry, in which competition is increasingly fierce. There are many things for the life insurers to do many things to retain the customers. One of those things is to make sure to keep in touch with all customers. When an insurance-planner resigned, his/her customers must be taken care of by some planner-assistants. This article outlines the design of Contact Scheduling System (CSS) that supports planner-assistants for contacting the customers. Planner-assistants are unable to share the resigned insurance-planner's experience and knowledge regarding the customer relationship management. The CSS developed by employing both Classification And Regression Tree (CART) technique and Sequential Pattern Mining (SPM) technique has a two-stage process. In the first stage, it segments the customers into eight groups by CART model. Then it generates contact scheduling information consisting of contact-purpose, contact-interval and contact-channel, according to the segment's typical contact pattern. Contact-purpose is derived by schedule-driven, event-driven, or business-rule-driven. Schedule-driven contact is determined by SPM model. In the operation of CSS in a realistic situation, it shows a practicality in supporting planner-assistants to keep in touch with the customers efficiently and effectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.546-551
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• 2014

This paper proposes an opportunistic subchannel allocation (OSA) scheme for relay-based marine communication networks to improve a sum-rate capacity. In most previous works for relay-based networks, each RS delivers the data received from the BS immediately to the corresponding ships in each frame. The achievable data-rate of the two-hop transmission (BS-RS and RS-ship links) is thus limited by the channel quality between BS-RS and RS-ship links. Hence, the radio resources can be wasted according to the difference in the channel quality between the BS-RS link and the RS-ship link. The proposed OSA scheme reduces the waste of radio resources by efficiently and independently allocating the radio resources at the BS-RS link and at the RS-ship link according to the channel quality of each link. The proposed OSA scheme, however, increases the computational complexity, because the BS finds the optimal OFDMA resource by checking the channel quality of all BS-RS links and RS-ship links. The simulation results show that the sum-rate capacity of the proposed OSA scheme improves maximum 14.0% compared with the conventional scheme.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.421-425
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• 2005

The increasing number of wireless subscribers who can use internet service any time and any place have caused wireless communications networks to flourish. However, since total communication channel bandwidth for wireless communications is limited, it is very important to find the solution for maximizing the channel utilization. Thus, in this work we propose a QoS packet scheduler for IEEE 802.11e EDCA scheme which is able to maximize the channel throughput with changing the CW value considering wireless channel condition. This proposed scheme is evaluated with NS-2 network simulator under various environments and it is easily shown from the numerical results that the proposed scheme provides better performance than that of the original IEEE 802.11e scheme.

• Journal of Convergence for Information Technology
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• v.12 no.3
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• pp.280-285
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• 2022

In order to ensure maximum capacity at a given frequency resource, the number of antennas must be increased. The increase in antennas means that such guaranteed channel resources can be used as an increase in channel capacity by aquiring another channel resource. In order to aggregate antennas in such a situation where there are a plurality of antennas, a problem of miniaturizing and integrating antennas must be accompanied. In this situation, in order to efficiently allocate channel resources and antenna resources in limited device resources, the problem of antenna selection and user scheduling was considered and solved together. By numerical simulation results, the proposed algorithm was proven to effectively reduce 34 % power consumption in averagewith increase in antennas.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.332-340
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• 2010

In this paper, we deal with multi-user diversity scheduling methods that transmit simultaneously signals from multiple users using superposition coding multiplexing. These methods can make various scheduling methods be obtained, according to strategies for user selection priority from the first user to the first-following users, strategies for per-user power allocation, and resulting combining strategies. For the first user selection, we consider three strategies such as 1) higher priority for a user with a better channel state, 2) following the proportional fair scheduling (PFS) priority, 3) higher priority for a user with a lower average serving rate. For selection of the first-following users, we consider the identical strategies for the first user selection. However, in the second strategy, we can decide user priorities according to the original PFS ordering, or only once an additional user for power allocation according to the PFS criterion by considering a residual power and inter-user interference. In the strategies for power allocation, we consider two strategies as follows. In the first strategy, it allocates a power to provide a permissible per-user maximum rate. In the second strategy, it allocates a power to provide a required per-user minimum rate, and then it reallocates the residual power to respective users with a rate greater than the required minimum and less than the permissible maximum. We consider three directions for scheduling such as maximizing the sum rate, maximizing the fairness, and maximizing the sum rate while maintaining the PFS fairness. We select the max CIR, max-min fair, and PF scheduling methods as their corresponding reference methods [1 and references therein], and then we choose candidate scheduling methods which performances are similar to or better than those of the corresponding reference methods in terms of the sum rate or the fairness while being better than their corresponding performances in terms of the alternative metric (fairness or sum rate). Through computer simulations, we evaluate the sum rate and Jain’s fairness index (JFI) performances of various scheduling methods according to the number of users.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.336-339
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• 2011

In the RTLS(Real Time Location Based System), in case of existing a number of moving target, extremely complecated data flow is can be occurred. In the network where single gateway exists, various data which was collected from sensor node is transmitted along the simple route as time goes by. In case of multi-gateway configuration, the collected data is transmitted through diverse routes rather than simple route. This kind of data causes jams on nodes and this brings down the performance of the network. Different from existing studies, in this thesis, MAC (Media Access Control) protocol which minimizes data collision between nodes and guarantees QoS(Quality of Service) is suggested, in order to communicate efficiently in multi-gateway underwater sensor network environment. In the suggested protocol, source node which wants to transmit data makes a channel reservation to a number of destination node using a RTS packet. Source node reserves a channel without collision, by scheduling CTS response time using expected delay information from neighbor nodes. Once the reservation is made, source node transmit data packet without collision. This protocol analyzes/estimates the performance compared to a method provided from existing studies via simulation. As a results of the analysis, it was comfirmed that the suggested method has better performance, such as efficiency and delay.

• Journal of Broadcast Engineering
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• v.16 no.5
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• pp.834-845
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• 2011

Massive broadcasting contents such as UHD(Ultra High Definition) TV which requires multi-channel capacity for transmission has been introduced in recent years. A transmission scheme with channel bonding has been considered for transmission of massive broadcasting contents. In HFC(Hybrid Fiber Coaxial) networks, DOCSIS 3.0(Data Over Cable Service Interface Specification 3.0) has already applied channel bonding schemes for up/downstream of data service. A method unlike DOCSIS 3.0 is required to introduce a channel bonding scheme in the broadcasting service having unidirectional transmission with a downstream. Since a massive broadcasting content requires several channels for transmission, VBR(Variable Bit Rate) transmission has been emerging for the bandwidth efficiency. In addition, research on channel allocation and resource scheduling is required to guarantee QoS(Quality of Service) for the broadcasting service based on VBR. In this paper, we propose a transmission method for mass broadcasting service in HFC network and show the UHD transmission simulator developed to evaluate the performance. In order to evaluate the performance, we define various scenarios. Using the simulator, we assess the possibility of channel bonding and VBR transmission for UHD broadcasting system to provide mass broadcasting service efficiently. The developed simulator is expected to contribute to the efficient transmission system development of mass broadcasting service.

• Journal of Communications and Networks
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• v.10 no.3
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• pp.258-267
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• 2008

In this paper, we examine what changes the next-generation wireless communication systems will experience in terms of the technologies, services, and networks and, based on that, we investigate how the inter-cell interference management should evolve in various aspects. We identify that the main driving forces of the future changes involve the data-centric services, new dynamic service scenarios, all-IP core access networks, new physical-layer technologies, and heavy upload traffic. We establish that in order to cope with the changes, the next-generation inter-cell interference management should evolve to 1) set the objective of providing a maximal data rate, 2) take the form of joint management of power allocation and user scheduling, 3) operate in a fully distributed manner, 4) handle the time-varying channel conditions in mobile environment, 5) deal with the changes in interference mechanism triggered by the new physical-layer technologies, and 6) increase the spectral efficiency while avoiding centralized coordination of resource allocation of the users in the uplink channel.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1311-1317
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• 2010

In this paper, for a uplink space division multiple access system named cooperative spatial multiplexing(CSM), radio resource management(RRM) algorithms are proposed based on sharing uplink channel information among a serving base station(BS) and interfering BSs in a uplink coordinated wireless communication system. A constrained maximum transmit power algorithm is proposed for mobile station(MS) to limit uplink inter-cell interference(ICI). And joint scheduling algorithm among coordinated BSs is proposed to enhance uplink capacity through ICI mitigation by using channel information from interfering BSs. It is shown that the proposed RRM algorithm provides a considerable uplink capacity enhancement by effective ICI mitigation only with moderate complexity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.9
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• pp.2154-2172
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• 2013

A centralized cognitive radio (CR) network is proposed and its system capacity is studied. The CR network is designed with power control and multi-user scheduling schemes to support best-effort traffics under peak interference power constraints. We provide an analytical framework to quantify its system capacity, taking into account various key factors such as interference constraints, density of primary users, cell radius, the number of CR users, and propagations effects. Furthermore, closed-form formulas are derived for its capacities when only path loss is considered in the channel model. Semi-analytical expressions for the capacities are also given when more realistic channel models that include path loss, shadowing, and small-scale fading are used. The accuracy of the proposed analytical framework is validated by Monte Carlo simulations. Illustrated with a practical example, the provided analytical framework is shown to be useful for the strategic planning of centralized CR networks.