• Electronics and Telecommunications Trends
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• v.13 no.5 s.53
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• pp.65-78
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• 1998

B-ISDN은 다양한 속도의 영상, 음성, 데이터 등에 의한 멀티미디어 통신서비스를 실현하기 위해, Asynchronous Transfer Mode (ATM)를 전송방식으로 채용하고 있으며, ITU--T 등 국제표준화 기구에서 표준화가 진행되고 있다. 본 고에서는 B-ISDN의 서비스품질에 대해 ATM 셀 전송품질(ATM Layer Cell Transfer Performance), 접속품질(Call Processing Performance), 안정품질(Availability Performance)로 나누어 고찰하고, 이들을 반영한 ITU--T의 서비스품질 표준화 동향에 대해 ATM Forum의 동향과 연관지어 기술하였다. 특히, ATM 셀 전송품질을 사용자가 지정한 Quality of Service (QoS) 클래스 방식과 QoS 파라미터 방식의 제공에 대해 고찰하였으며, B-ISDN을 기반으로 한 Internet Protocol (IP) 망과 세계정보통신기반 Global information Infrastructure (GII)의 품질표준화 동향에 대해서도 소개하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.408-413
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• 2003

The frequency response function(FRF) of each substructure is used for the transfer function synthesis method(TFS). The dynamic characteristics of the full system are obtained by synthesizing FRFs of each substructure. The validation of TFS depends on accuracy for FRF of each substructure. Impact hammer testing Is widely used to obtain the modal characteristics of structures However. the FRF obtained from impact hammer testing contains bias errors, such as finite record length error and leakage error of which characteristic depends on data acquisition time which we call record length. In this paper, a method to remove hose errors is proposed so as to enhance results of TFS. Numerical and experimental examples show that the FRF of full structure can be predicted nearly exactly by the method proposed in this paper.

• Annual Conference of KIPS
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• 2013.11a
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• pp.301-302
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• 2013

LTE is the outstanding technology to transfer the data and voice. LTE consists of several nodes to transfer data. In case of the failure in the node of LTE, it could not support the service. So telecommunication-providers set up the back-up system for the simultaneous service-provision. But there is still the problem it comes to the network. Even though there is a back-up system, it would be useless the network is down. We propose the scheme to support the service in the case of this network problem in the LTE network. This scheme reduces 23% load in the LTE network in the case of the HSS node's failure or the network to the HSS nodes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4B
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• pp.397-402
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• 2004

In this paper, we have designed and simulated a new file transmission method. This method restricts memory copy and context switching happened in traditional file transmission. This method shows an improved performance than traditional method in network environment. When the UNIX/LINUX system that uses the existing file transfer technique transmits a packet to the remote system, a memory copy between the user and kernel space occurs over twice at least. Memory copy between the user and kernel space increase a file transmission time and the number of context switching. As a result, the existing file transfer technique has a problem of deteriorating the performance of file transmission. We propose a new algorithm for solving these problems. It doesn't perform memory copy between the user and kernel space. Hence, the number of memory copy and context switching is limited to the minimum. We have modified the network related source code of LINUX kernel 2.6.0 to analyzing the performance of proposed algorithm and implement new network system calls.

• The Transactions of the Korea Information Processing Society
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• v.4 no.1
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• pp.195-208
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• 1997

ISDN is network which has been developed to integrate and transfer some information(data, video, voice). In the ISDN, security problem that threat and intrusion about important information resource increase because every information is transferred in the form of digital and access of network has patiency. In this paper, for protect important information resource, studied that apply application method and encryption system to ISDN, and system structure, ITU-T Q.931 protocol were analyzed, and proposable encryption key distribution protocol, call control with hybrid encryption system for user information privacy to provide security service.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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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.

• Journal of Communications and Networks
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• v.6 no.1
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• pp.68-77
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• 2004

In the near future packet networks should support applications which can not predict their traffic requirements in advance, but still have tight quality of service requirements, e.g., guaranteed bandwidth, jitter, and packet loss. These dynamic characteristics mean that the sources can be made to modify their data transfer rates according to network conditions. Depending on the customer&; needs, network operator can differentiate incoming connections and handle those in the buffers and the interfaces in different ways. In this paper, dynamic QoS-aware scheduling algorithm is presented and investigated in the single node case. The purpose of the algorithm is in addition to fair resource sharing to different types of traffic classes with different priorities ?to maximize revenue of the service provider. It is derived from the linear type of revenue target function, and closed form globally optimal formula is presented. The method is computationally inexpensive, while still producing maximal revenue. Due to the simplicity of the algorithm, it can operate in the highly nonstationary environments. In addition, it is nonparametric and deterministic in the sense that it uses only the information about the number of users and their traffic classes, not about call density functions or duration distributions. Also, Call Admission Control (CAC) mechanism is used by hypothesis testing.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2399-2404
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• 2009

In cellular network systems one of the most significant quality metrics to measure quality of performance is the average number of call drops in a system. It ensures that the active calls in the system are successfully completed without being dropped in the mid communication for ultimate customer satisfaction. Hand-off mechanism increases cellular system reliability by seamless continuation of active calls by transferring active calls from one base station to another. In this paper, we study and propose a simple hand-off mechanism using game theory. We conclude that using the simple QoS utility function proposed in this paper, our optimal deterministic hand-off strategy is to transfer the active calls to the base station with greater signal-to-interference ratio (SIR) and greater number of available channels.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.11
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• pp.25-33
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• 1997

The end-to-end rate-based control mechanism is used for the flow control of the ABR service to allow much more flexibility in ATM switching system. To accommodate the ABR service effciently many algorithms such as EFCI, EPRCA, ERICA, and CAPC2 have been proposed for the switch algorithm. ABR cells and related RM cells are received at the ATM switch fabric transparently without any processing. And then cells received from the traffic source are queued in the ABR buffer of switching system. The ABR buffer usually has some thresholds for easy congestion control signal transmission. Whatever we use, therefore, these can be many ABR traffic control algorithms to implement the ABR transfer capability. The genertion of congestion indicate signal for ABR control algorithms is determined by ABR buffer satus. And ABR buffer status is determined by ABR cells transfer ratio in ATM switch fabrics. In this paper, we presented the functional structures for control of the ABR traffic capability, proposed the readout scheduling, cell slot allocation of output link and the buffer allocation model for effective ABR traffic guranteeing with considering CBR/VBR traffics in ATM switch. Since the proposed readout scheduling scheme can provide more avaliable space to ABR buffer than existing readout scheduling scheme, generation rate of a SEND signal, that is, BCN signal in destination node can be increased for ABR call connection. Therefore, the proposed scheme, in this paper, can be appropriate as algorithm for effective ABR traffic service on output link of ATM switching node.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.682-685
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• 2002

VoIP(Voice over IP) Technology is highlighted because of easy adopting the value added services related voice In this paper, we described the Internet telephony service based on SIP. Especially, we described the extension for re-INVITE function. Re-INVITE function is useful for cail transfer service or conference service.