• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3A
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• pp.129-139
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• 2003

CAC is a very important issue in CDMA system in order to protect the required QoS(quality of service) and increase the system's capacity. In this paper, we proposed and analyzed a call admission control scheme using multiple thresholds, which can provide quick processing time and better performance. There are two effective thresholds used to decide call admission. One is the number of active users, and the other is the signal to interference ratio(SIR). If the threshold of active users are lower than the low number of users threshold, we accept the new call without any other conditions. Otherwise, we check the current SIR to guarantee the quality of our service. System then accepts the new call when the SIR satisfies system requirement. Otherwise, the call will be rejected. Multiple threshold schemes are investigated and their performance is compared with the number of user and power based CAC's. simulation results are provided to evaluate the performance.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.331-333
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• 2004

본 논문에서는 SIP(Session initiation Protocol) 기반의 VoIP(Voice over Internet Protocol) 시스템에 효율적인 call-control을 위해 필요한 헤더와 파라미터를 추가한 Extension SIP를 제안하였다. 또한 이 제시된 Extension SIP에 따르는 SIP Proxy Server와 User Agent(User Agent Client, User Agent Server)를 리눅스 시스템에서 C언어를 통해 구현하였고, 이 구현된 Extension SIP 시스템을 통해 기존의 SIP 시스템과 cail-control을 위한 packet traffic을 비교.분석 함으로써 제안한 Extension SIP의 효율성 을 증명하였다.

• IE interfaces
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• v.17 no.4
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• pp.466-471
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• 2004

In this paper, I develop a simple dynamic resource allocation algorithm that reduces the call blocking rate by improving the resource utilization of the WCDMA (Wideband Code Division Multiple Access) systems under multimedia service environment. Simulation results show that the proposed algorithm significantly reduces the blocking rate of high speed multimedia calls. The algorithm developed in this paper is currently working in the commercial WCDMA IMT-2000 system.

• The Journal of Information Technology
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• v.3 no.2
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• pp.115-126
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• 2000

When a terminal frequently crosses a RA or a call originate in a boundry cell, HLR should be updated or queried. Frequent DB accesses and message transfers may cause the HLR bottleneck and degrade the system performance. This paper propose scheme to solve the HLR bottleneck problem and reduce to call registration cost and call tracking cost in wirless networks.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.05b
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• pp.532-535
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• 2003

아웃바운드(Outbound) 형 콜 센터는 서비스 지향의 인바운드(Inbound) 형 콜 센터와는 달리 전화를 거는 주체가 고객에게 접촉하고자 하는 목적을 뚜렷하게 가진 상태에서 제품 또는 서비스, 정보제공 등을 전화나 기타 커뮤니케이션 채널을 통해 전달하는 업무를 담담한다. 본 논문에서는 아웃바운드 형 콜 센터 시스템을 예측 다이얼링(Predictive Dial Ing) 방식에 기반하여 개선된 콜 전략을 제안한다 개선된 콜 전략은 콜 센터 업무의 중심 역할인 콜링 리스트(Call ing List)를 데이터 추출 모듈을 사용하여 테이블로 구성한 뒤, 시간 활용을 통한 효율적 대응과 다양한 고객들의 정보를 바탕으로 고객과의 접촉확률을 증가시킬 수 있다.

• Journal of Intelligence and Information Systems
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• v.16 no.3
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• pp.99-120
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• 2010

Due to the wide spread of customers' frequent access of non face-to-face services, there have been many attempts to improve customer satisfaction using huge amounts of data accumulated throughnon face-to-face channels. Usually, a call center is regarded to be one of the most representative non-faced channels. Therefore, it is important that a call center has enough agents to offer high level customer satisfaction. However, managing too many agents would increase the operational costs of a call center by increasing labor costs. Therefore, predicting and calculating the appropriate size of human resources of a call center is one of the most critical success factors of call center management. For this reason, most call centers are currently establishing a department of WFM(Work Force Management) to estimate the appropriate number of agents and to direct much effort to predict the volume of inbound calls. In real world applications, inbound call prediction is usually performed based on the intuition and experience of a domain expert. In other words, a domain expert usually predicts the volume of calls by calculating the average call of some periods and adjusting the average according tohis/her subjective estimation. However, this kind of approach has radical limitations in that the result of prediction might be strongly affected by the expert's personal experience and competence. It is often the case that a domain expert may predict inbound calls quite differently from anotherif the two experts have mutually different opinions on selecting influential variables and priorities among the variables. Moreover, it is almost impossible to logically clarify the process of expert's subjective prediction. Currently, to overcome the limitations of subjective call prediction, most call centers are adopting a WFMS(Workforce Management System) package in which expert's best practices are systemized. With WFMS, a user can predict the volume of calls by calculating the average call of each day of the week, excluding some eventful days. However, WFMS costs too much capital during the early stage of system establishment. Moreover, it is hard to reflect new information ontothe system when some factors affecting the amount of calls have been changed. In this paper, we attempt to devise a new model for predicting inbound calls that is not only based on theoretical background but also easily applicable to real world applications. Our model was mainly developed by the interactive decision tree technique, one of the most popular techniques in data mining. Therefore, we expect that our model can predict inbound calls automatically based on historical data, and it can utilize expert's domain knowledge during the process of tree construction. To analyze the accuracy of our model, we performed intensive experiments on a real case of one of the largest car insurance companies in Korea. In the case study, the prediction accuracy of the devised two models and traditional WFMS are analyzed with respect to the various error rates allowable. The experiments reveal that our data mining-based two models outperform WFMS in terms of predicting the amount of accident calls and fault calls in most experimental situations examined.

• ETRI Journal
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• v.25 no.1
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• pp.34-40
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• 2003

This paper considers a TMN-based management system for the management of public ATM switching networks using a four-level hierarchical structure consisting of one network management system, several element management systems, and several agent-ATM switch pairs. Using Jackson's queuing model, we analyze the effects of one TMN command on the performance of the component ATM switch in processing local calls. The TMN command considered is the permanent virtual call connection. We analyze four performance measures of ATM switches- utilization, mean queue length and mean waiting time for the processor directly interfacing with the subscriber lines and trunks, and the call setup delay of the ATM switch- and compare the results with those from Jackson's queuing model.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1533-1536
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• 2001

This paper considers the TMN system for management of public ATM switching network which has the four-level hierarchical structure consisting of one network management system, a few element management system and several agent-ATM switch pairs, respectively. The effects of one TMN command on the local call processing performance of the component ATM switch an analyzed using Jackson's queueing model. The TMN command considered is the permanent virtual call connection, and the performance measures of ATM switch are the utilization, mean queue length and mean waiting time for the processor interfacing the subscriber lines and trunks directly, and the call setup delay of the ATM switch.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.4
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• pp.952-960
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• 1996

In this paper, a new overload control scheme is proposed for a control system in ATM switching system. The proposed control scheme includes a counter that conunts the number of accepted calls and is decreased at cach D time interval. In overload condition of call processor, the control scheme detects over load condition when the counter value reaches a certain threshold value. Under overload condition, processor utilization is measured and the value of the D is updataed according to the difference between measured processor utilization and target utilization. A new call is accepted accepted only if the value of the counter is less than the threshold value. In overflow condition of cell traffic, accept probability of new call is reduced exponetially according to the elapsed time. The results of simulation show that the proposed overload contorl scheme maintains the target utilization very well under the various processor overload conditions and reduces the cell loss probability under the cell overflow conditions.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.4
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• pp.445-459
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• 2008

This paper addresses a call admission control(CAC) scheme giving handoff calls a priority over new calls for OFDMA wireless communication systems. The characteristics of OFDMA system and a variety of user QoS (Quality of Service) requirements are incorporated into the proposed CAC scheme which consists of several optimization modules for the system resource(subcarriers and power) allocations. The mathematical models and its solution methods for the embedded resource allocation problems are proposed. Some extensive computational experiments are conducted to illustrate the superiority of our CAC.