• The Korean Journal of Zoology
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• v.35 no.2
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• pp.226-230
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• 1992

5마리의 안주애기박쥐(Vespenilio superons) 새끼들의 Isolation call에 대해 연구를 하였다. 이들의 소리는 각각의 unit(2-9)로 구성되어 있으며 연결음을 내고 있다. 배음의 unit가운데 기본음의 주파수 범위는 5-23 kHz에 놓여 있다. 주파수 변조 패턴에 따라 대개의 unit들은 2타임으로 분류되나, 개체적 변이가 발견되었다. 새끼들의 소리는 개체마다 특징적으로 나타났다. (unit 수/call, 사용된 unit 유형, 주파수 범위 ); 이들의 전형적인 유형은 발달 과정을 통해 고유한 소리로 나타났다.

• Journal of Distribution Science
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• v.14 no.5
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• pp.91-96
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• 2016

Purpose - Although various studies have been conducted on the stress of service employees, there are still lack of studies regarding job stress and job satisfaction of call center workers. Especially there are quite few studies on the job stress according to employment type. This study focused on job stress and job satisfaction for call center employees and the correlation between the two factors and aimed to provide basic materials for seeking for the plans to reduce job stress and improve job satisfaction. Research design, data, and methodology - Frequency, percentage, and mean value were calculated through descriptive statistics in order to find out demographic characteristics, level of job stress, and job satisfaction. Differences in job stress according to employment type were calculated by using one-way ANOVA. Correlation between job stress and job satisfaction were identified through empirical analysis with Pearson's correlation coefficient. 150 materials were used for final analysis. The collected materials were analyzed to get statistics by using SPSS 20. Results - First, as for the job stress of call center workers, overall mean value was 2.54 in 4-point scales. Among the six sub-factors, job demands had the highest score, which was 2.67. Second, as for the job stress according to employment type, others showed higher score than mean value followed by contract job and full-time job in that order, in terms of job insecurity and organizational system. In terms of inappropriate remuneration, contract job showed higher score than mean value followed by others and full-time job. Third, as for the satisfaction with job, the mean value was 2.37 in 4-point scale and "very much satisfied" was only 3.3%. Lastly, in terms of job stress and job satisfaction, all sub-factors except for job demands showed significant correlation. The more job stress increased, the more job satisfaction decreased. Conclusions - First, as a result of analyzing job stress according to the employment type of call center workers, job stress increased more when the employment type was not full-time. Therefore, it was assumed that self-rescue efforts should be followed for effective employment management of call center business where contract employment takes most part as well as efforts to transfer them to full-time job. Second, decrease in job satisfaction of call center workers may affect the performance of an organization as well as service quality of the company providing the service. Therefore, various supports are required to decrease job stress and increase job satisfaction for call center workers through the expansion of rest area or break time. Third, I could recognize that there were lack of academic research on call center business in the whole service industry. Therefore, further research should be conducted more actively in the future. In particular, this study has special significance in the aspect that there were few studies on the job stress of call center workers according to employment type.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8B
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• pp.681-688
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• 2008

In this paper, we propose a new price-based call admission control algorithm for multi-class communication networks. When a call arrives at the network, it informs the network of the number of requested circuits and the minimum amount of time that it will require. The network provides the optimal price for the arrived call with which it tries to maximize its expected revenue. The optimal price is dynamically adjusted based on the information of the arrived call, and the present and the estimated future congestion level of the network during the reservation time of the call. If the call accepts the price, it is admitted. Otherwise, it is rejected. We compare the performance of our dynamic pricing algorithm with that of the static pricing algorithm by Courcoubetis and Reiman [1], and Paschalidis and Tsitsiklis [2]. By the comparison, we show that our dynamic pricing algorithm has better performance aspects such as higher call admission ratio and lower price than the static pricing algorithm, although these two algorithms result in almost the same revenue as shown in [2]. This implies that, in the competitive situation, the dynamic pricing algorithm can attract more users than the static pricing algorithm, generating more revenue. Moreover, we show that if a certain fixed connection fee is introduced to the price for a call, our dynamic pricing algorithm yields more revenue.

• Journal of KIISE:Information Networking
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• v.30 no.4
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• pp.461-473
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• 2003

Multimedia applications are much more sensitive to QoS(Quality of Service) than text based ones due to their data continuity. In order to provide a fast moving MH(Mobil Host) using multimedia application with a consistent QoS,an efficient call admission mechanism is in need. This paper proposes the 2SCA(2-Step Call Admission) scheme based on cal admission scheme using pripority to guarantee the consistent QoS for mobile multimedia applications. A calls of MH are classified new calls, hand-off calls, and QoS upgrading calls. The 2SCA is composed of the basic call admission and advanced call admission; the former determines the call admission based on bandwidth available in each cell and the latter determines the call admission by applying DTT(Delay Tolerance Time), PQeueu(Priority Queue), and UpQueue(Upgrade Queue) algorithm according to the type of each call blocked at the basic call admission stage. In order to evaluate the performance of our mechanism, we measure the metrics such as the dropping probability of new calls, dropping probability of hand-off calls, and bandwidth utilization. The result shows that the performance of our mechanism is superior to that of existing mechanisms such as CSP(Complete Sharing Policy), GCP(Guard Channel Policy) and AGCP(Adaptive Guard Channel Policy).

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.6
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• pp.1-13
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• 2018

The number of deaths in Korea is higher than the OECD average. Therefore, an e-Call system is being developed as a vehicle ICT-based emergency rescue system that automatically detects an accident in the event of a vehicle accident and transmits related information to the center. In order to overcome the limitations of social acceptability and function of e-Call system, we propose a model that allows users to be aware of the necessity of service voluntarily. We predicted the market share of e-call services according to the proposed business model and analyzed it through B/C analysis. Benefits are calculated on a penetration basis, and device purchase and communications costs are calculated for each period. B/C analysis shows that pessimistic scenarios are 0.98 in 2025 and 1.01 in 2030. In an optimistic scenario, it is 1.05 in 2025 and 1.20 in 2030, which is more economical.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.71-84
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• 2005

Recently, the expert call center solution has become the center of interest, since finance and tele-marketing system, which is focused on a communication industry, have been increasing, Specially, the call center market is growing up with a supporting Caller-ID for a cellular phone in Korea, In the present, although large size companies are developing expensive solutions and instruments to service only for the big companies, there little solutions for SOHO markets, Therefore, in this paper we have shown a design and an implementation of a CTI system which is capable of in/outbound call processing by using CTI, and providing stable services by linking the customer's DB. And these functionalities have become possible by integrating functions of PBX and the computer control of the PBX. First, we have constructed call flows and analyzed packets for the standard communication through the PBX in call. Then, we have designed and implemented a middleware which linked a call between a client and a customer. Finally, we have constructed a database module for applying the CRM technology to the management of customer's contents.

• Journal of Advanced Navigation Technology
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• v.13 no.2
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• pp.208-213
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• 2009

This paper presents an adaptive call admission control(CAC) algorithm based on a target handoff call dropping probability in mobile wireless environments. This method uses a neural network for predicting and reserving the bandwidth demands for handoff calls and new calls. The amount of bandwidth to be reserved is adaptively adjusted by a target value of handoff call dropping probability(CDP). That is, if the handoff CDP exceeds the a target CDP value, the bandwidth to be reserved should be increased to reduce the handoff dropping probability below a target value. The proposed method is intended to prevent from increasing handoff call dropping probability when bandwidth to be reserved is not enough for handoff calls due to an uncertain prediction. Our simulations compare the handoff CDP in proposed CAC with that of an existing CAC. Results show that the proposed method sustains handoff call dropping probability below our target value.

• Journal of Advanced Navigation Technology
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• v.20 no.5
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• pp.440-445
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• 2016

There is a scheme where secondary users (SU) use predicted spectrum holes for primary users (PU) not to utilize for efficient utilization of the limited spectrum resources in cognitive radio networks. In this paper, we propose an adaptive call admission control framework that minimizes spectrum hopping call dropped probability (SHDP) for satisfying SU quality of service (QoS). The scheme is based on a call admission control (CAC), bandwidth prediction and adaptive bandwidth assignment. The prediction model predicts not only the number of spectrum holes, but requested bandwidth of SU spectrum hopping call, and then the CAC minimizes SHDP via an adaptive bandwidth assignment in resources not being enough for reservation. We bring Wiener prediction model to predict the resources. Simulations are conducted to compare the performance of proposed scheme with an existing, and show its ability of minimizing the SHDP.

• The Transactions of the Korea Information Processing Society
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• v.3 no.5
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• pp.1253-1261
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• 1996

The base station (BS) of CDMA mobile system (CMS) provides mobile call services by controlling call processing functions. The call Processing part of the BS is divided into two components; the base station transceiver subsystem (BTS) and the base station controller (BSC). In this paper, we present the call capacity estimation of the BS about control signals and traffic data of calls by the simulation, and find the bottleneck points and problems which may occur in the BS. In order to estimate the call capacity, first we extract the major parameters for the modeling the BS. Second, we suggest the simulation model for the BS. Third, we estimate the simulation results by finding major objective factors such that the call blocking probability, the utilization ratio and the delay time in the traffic channel elements (TCEs), the BTS interconnection network (BIN)-COMA interconnection network (CIN) trunks, the transcoding channels and the CIN packet router.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.347-352
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• 2014

In this paper, we propose a Markovian queueing model(M/M/1)-based call admission control to reduce forced terminating rate of non-real secondary user's call for Multi-services Cognitive Radio Networks. A existing control has a problem that the forced terminating rate increases because of adopting a policy of spectrum priority allocation to real calls. In our scheme the rate can be reduced as the call that has no useful spectrum waits in a queue until getting an available spectrum. Our scheme use a neural-net based prediction of primary user's reappearance. Through the simulation, we analysis the call forced terminating rate, access delay and spectrum utilization efficiency, and then show that our scheme can more reduce the forced terminating rate of the call, compared to that of the existing algorithm.