• 한국정보과학회논문지:정보통신
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• 제31권5호
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• pp.511-518
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• 2004

DCOM, CORBA 등의 분산객체(distribute object)의 뒤를 이어 등장한 웹 서비스(Web Services) 기술은 SOAP, WSDL, UDDI 둥의 XML 기반의 공개 표준을 바탕으로 하여 웹을 통한 원격 프로시저 호출(Remote Procedure call)의 메커니즘을 제공하여, e-비즈니스에서 통합과 협업의 방법으로 최근 각광을 받고 있다. 특히, UDDI는 웹 서비스를 등록 및 검색을 가능하게 해주는 레지스트리(registry)로, 웹 서비스를 위한 인프라를 제공하는 역할을 담당하고 있다. 하지만 기존 UDDI는 검색 방법이 단순하고, 해당 웹 서비스의 품질을 평가하여 검색할 수 있는 방법을 제공하고 있지 못하다는 문제를 가지고 있다. 본 논문은 웹 서비스의 품질을 평가하여 그에 대한 검색을 가능하게 해줄 수 있는 UDDI 개선 모델을 제안하고자 한다.

• 한국통신학회논문지
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• 제28권3A호
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• pp.129-139
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• 2003

호 수락제어 기법은 CDMA시스템에서 통화중인 호들의 통화품질을 보장하고 시스템의 용량을 증가시킬 수 있는 중요한 기법이다. 본 논문에서는 다중 종류의 문턱치를 사용한 호 수락제어 기법(MCAC : multiple thresholds CAC)을 제시하고 컴퓨터 시뮬레이션을 통하여 그 성능을 분석하였다. 이 기법에서는 두 가지 종류의 문턱치를 이용하여 새로운 호의 호 신청 수락여부를 결정한다. 첫 번째 문턱치는 통화중인 사용자의 수이고 두 번째 문턱치는 기지국에서 측정되는 신호-대-간섭비이다. 통화중인 사용자의 수가 시스템에서 새로운 사용자를 받아들일 수 있는 충분한 여유용량이 있다고 판단하는 문턱치보다 적으면 신호-대-간섭비를 측정하지 않고 직접 새로운 호의 호 신청을 수락하고 통화중인 사용자의 수가 시스템에서 통화품질을 만족할 수 없다고 판단하는 문턱치보다 많으면 새로운 호의 호 신청을 거절하도록 한다. 통화중인 사용자의 수가 두 문턱치사이에 위치하면 측정된 신호-대-간섭비에 근거하여 호 수락여부를 결정한다. 제안된 알고리즘의 성능평가를 위하여 시스템의 통화품질 저하확률(outage probability)과 호 차단확률(call blocking probability) 및 전 처리확률(pre-processing probability)을 이용하며 제안된 알고리즘의 성능을 기존에 제시된 사용자수에 기반한 알고리즘과 신호-대-간섭비에 기반한 알고리즘과 비교하도록 한다. 실험결과는 제안된 알고리즘이 기존의 신호-대-간섭비에 기반한 알고리즘의 우수한 성능을 유지하면서 호 수락 처리속도를 높일 수 있음을 보여준다.

• 유통과학연구
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• 제14권5호
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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.

• ETRI Journal
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• 제29권1호
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• pp.113-115
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• 2007

A dynamic tri-threshold call admission control scheme has been developed. This scheme supports voice, data, and multimedia services and it complies with the universal mobile telecommunications system. The performance of the proposed scheme is evaluated under varying handover rates. The QoS performance-including channel utilization, call dropping probability, and blocking probability-is investigated. The performance of the developed scheme is found to be encouraging.

• Journal of Communications and Networks
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• 제12권6호
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• pp.568-576
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• 2010

The paper presents a control architecture aimed at implementing bandwidth optimization combined with call admission control (CAC) over a digital video broadcasting (DVB) return channel satellite terminal (RCST) under quality of service (QoS) constraints. The approach can be applied in all cases where traffic flows, coming from a terrestrial portion of the network, are merged together within a single DVB flow, which is then forwarded over the satellite channel. The paper introduces the architecture of data and control plane of the RCST at layer 2. The data plane is composed of a set of traffic buffers served with a given bandwidth. The control plane proposed in this paper includes a layer 2 resource manager (L2RM), which is structured into decision makers (DM), one for each traffic buffer of the data plane. Each DM contains a virtual queue, which exactly duplicates the corresponding traffic buffer and performs the actions to compute the minimum bandwidth need to assure the QoS constraints. After computing the minimum bandwidth through a given algorithm (in this view the paper reports some schemes taken in the literature which may be applied), each DM communicates this bandwidth value to the L2RM, which allocates bandwidth to traffic buffers at the data plane. Real bandwidth allocations are driven by the information provided by the DMs. Bandwidth control is linked to a CAC scheme, which uses current bandwidth allocations and peak bandwidth of the call entering the network to decide admission. The performance evaluation is dedicated to show the efficiency of the proposed combined bandwidth allocation and CAC.

• 한국통신학회논문지
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• 제23권4호
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• pp.957-966
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• 1998

본 논문에서는 OS-COMA 셀룰라 시스템에서 추정된 SIR (signal-to-interference ratio) 값을 기반으로 하는 개선된 호 수락 제어(call admission control) 알고리즘을 제안하고 성능을 분석하였다. 제안된 알고리즘은 기지국에서 추정된 역방향 SIR 값에 따라 알고리즘에 의해 계산된 여유용량(residual capacity)을 호 수락 제어의 기준으로 하며, 여유용량은 시스탬의 통화품질 저하 확률(outage probability)을 일정 수준 이하로 유지하면서 추가로 허용 가능한 호의 수로 계산한다. 여유용량 계산 시 자기 셀 뿐만 아니라 인접 셀의 SIR 값을 참조하며 이때 인접 셀 간섭 결합계수 $\beta$를 사용한다. 본 논문에서는 자기 셀의 통화 부하량에 따라 $\beta$값을 가변한 개선된 알고리즘을 제안하고, 시스템의 통화 부하량에 따른 호차단확률(call blocking probability) 및 통화품질저하확률 성능을 시뮬레이션을 통해 분석하였다, 성능 평가를 위해 동일 부하(homogeneous load) 빛 밀집 부하(hot spot load) 조건을 고려했으며 개선된 알고리즘이 모든 부하량에서 기존의 알고리즘에 비해 성능이 우수함을 알았다. 특히 과부하 상황에서 통화품질저하확률이 일정한 값 이하로 유지되어 QoS(quality of service)를 확보할 수 있는 효과를 얻었다.

• 한국통신학회논문지
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• 제21권6호
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• pp.1480-1489
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• 1996

In ATM networks there are two methods in traffic control as schemes advancing the quality of service. One is reactive control after congestion and the other which is generally recommended, is preventive control before congestion, including connection admission control on call leel and usage parameter control, network parameter control, priority control and congestion control on cell level. In particular, usage parameter control is required for restricting the peak cell rate of bursy tracffic to the parameter negotiated at call set-up phase since the peak cell rate significantly influences the network quality of service. The scheme for progressing quality of service by usage parameter control is themethod using VSA(Virtual Scheduling Algorlithm) recommended ITU-T. The method using VSSA(Virtual Scheduling Suggested Algorlithm) in this paper is suggested by considering cell delay variation and token rate of leaky bucket, compared VSA and VSANT(Virtual Scheduling Algolithm with No Tolerance) with VSSA which polices violated cell probability of conformed peak cell rate and intentionally excessive peak cell rate. VSSA method using IPP(Interruped Poisson Process) model of input traffic source showed more quality of service than VSA and VSANT methods as usage parameter control because the suggested method reduced the violated cell probability of contformed peak cell rate and intentionally excessive peak cell rate.

• ETRI Journal
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• 제19권3호
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• pp.242-258
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• 1997

The Qualcomm code excited linear prediction (QCELP) speech coder was adopted to increase the capacity of the CDMA Mobile System (CMS). In this paper, we implemented the QCELP speech coding algorithm by using TMS320C50 fixed point DSP chip. Also the fixed point simulation was done with C language. The computation complexity of QCELP on TMS320C50 was 10k words and data memory was 4k words. In the normal call test on the CMS, where mobile to mobile call test was done in the bypass mode without double vocoding, mean opinion score for the speech quality was he Qualcomm code excited linear prediction (QCELP) speech quality was 3.11.

• 한국정보시스템학회지:정보시스템연구
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• 제8권1호
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• pp.93-108
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• 1999

The switching system is designed and developed to satisfy the performance design objectives recommended by ITU for call processing capacity and quality of service(QOS), etc. When the results by actual measurement at the system testing phase do not satisfy the performance design objectives, however, an effort is required to improve the performance. This paper presents a method for improving QOS by modifying the application programs for the switching system. In the proposed method, the sequence chart related to a delay time for call connection is modelled using PERT(Program Evaluation and Review Technique) network. Then, the criticality index of a message is calculated using Monte Carlo simulation to evaluate which message's processing time to decrease in order to decrease the delay time and thus to improve QOS. The criticality index of a block is also calculated to identify those software blocks that significantly contribute to the delay time.

• Journal of Information Processing Systems
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• 제11권4호
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• pp.616-629
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• 2015

A mobile terminal will expect a number of handoffs within its call duration. In the event of a mobile call, when a mobile node moves from one cell to another, it should connect to another access point within its range. In case there is a lack of support of its own network, it must changeover to another base station. In the event of moving on to another network, quality of service parameters need to be considered. In our study we have used the Markov decision process approach for a seamless handoff as it gives the optimum results for selecting a network when compared to other multiple attribute decision making processes. We have used the network cost function for selecting the network for handoff and the connection reward function, which is based on the values of the quality of service parameters. We have also examined the constant bit rate and transmission control protocol packet delivery ratio. We used the policy iteration algorithm for determining the optimal policy. Our enhanced handoff algorithm outperforms other previous multiple attribute decision making methods.