• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.2096-2105
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• 1998

As there can be coincident bursts which may result in congetsion in a node of ATM network, reactive flow control schemes are required to guarantee user's Quality of Service. But, the high speed characteristics of ATM networks make it difficult to control source transmission rate in reacting to congestions in intermediate nodes. Therefore, flow control in Customer Premise Network may be more efficient than end-to-end flow control. In this paper, we propose a management model for flow ontrol in CPN and new Network Access Flow/Congestsion control scheme to utilize efficiently Virtual Path Connection.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.75-83
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• 2016

In this paper, we propose a multi-channel medium access control (MAC) protocol, named underwater multi-channel MAC protocol (UMMAC), for underwater acoustic networks (UANs). UMMAC is a split phase and reservation based multi-channel MAC protocol which enables hosts to utilize multiple channels via a channel allocation and power control algorithm (CAPC). In UMMAC, channel information of neighboring nodes is gathered via exchange of control packets. With such information, UMMAC allows for as many parallel transmissions as possible while avoiding using extra time slot for channel negotiation. By running CAPC algorithm, which aims at maximizing the network's capacity, users can allocate their transmission power and channels in a distributed way. The advantages of the proposed protocol are threefold: 1) Only one transceiver is needed for each node; 2) based on CAPC, hosts are coordinated to negotiate the channels and control power in a distributed way; 3) comparing with existing RTS/CTS MAC protocols, UMMAC do not introduce new overhead for channel negotiation. Simulation results show that UMMAC outperforms Slotted floor acquisition multiple access (FAMA) and multi-channel MAC (MMAC) in terms of network goodput (50% and 17% respectively in a certain scenario). Furthermore, UMMAC can lower the end-to-end delay and achieves a lower energy consumption compared to Slotted FAMA and MMAC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9A
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• pp.874-881
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• 2010

Acoustic signal, which is a main carrier of underwater communication, attenuates along the traveled path heavily depending on the frequency as well as inter-node distance. In addition, since it has a long propagation delay, the conventional medium access control (MAC) schemes requiring complex signaling procedures and accordingly heavy overhead messages would not be appropriate in underwater communications. In this paper, we propose a code division multiple access (CDMA) scheme as a solution for MAC of underwater communication and evaluate the performance. A hierarchical data-gathering tree topology is considered and a staggered wake-up pattern is employed for the purpose of energy saving. As a performance measure, the data rate at each level of hierarchical topology is derived.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.9
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• pp.461-468
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• 2001

Though shared virtual memory (SVM) system promise low cost solutions for high performance computing they suffer from long memory latencies. These latencies are usually caused by repetitive invalidations on shared data. Since shared data are accessed through synchronization and the patterns by which threads synchronizes are repetitive, a prefetching scheme bases on such repetitiveness would reduce memory latencies. Based on this observation, we propose a prefetching technique which predicts future access behavior by analyzing access history per synchronization variable. Our technique was evaluated on an 8-node SVM system using the SPLASH-2 benchmark. The results show the our technique could achieve 34%~45% reduction in memory access latencies.

• The Journal of the Acoustical Society of Korea
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• v.28 no.6
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• pp.499-505
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• 2009

Main design issues for MAC (Medium Access Control) protocol in underwater sensor networks are long propagation delay caused by the low speed of sound, difficult synchronization, and energy-limited node's life. We aimed to mitigate the problems of strict synchronization and channel inefficiency of TDMA and also the throughput degradation induced by unavoidable collisions in contention based MAC protocols. This proposed protocol improved not only the energy efficiency by adopting a sleep-mode, but also the throughput by reducing collisions and increasing channel efficiency.

• ETRI Journal
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• v.9 no.4
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• pp.26-35
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• 1987

Switching system can be regarded as the key node of Integrated Services Digital Networks(ISDN) because it plays the Important role in realization of ISDN. As ISDN is evolved from the telephony Integrated Digital Network(IDN), the switching system for ISDN will be evolved from the function and structure of telephony digital switching system. At near future, ISDN switching system is expected to implement the integrated access and transparent switching functions for both voice and data. As final goals of switching system, advanced switching methods for information having various traffic characteristics such as voice, data, text and image should be considered. This paper considered. This paper will show some of the fundamental design challenges and architectural trends in ISDN switching system.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1988.10a
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• pp.144-147
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• 1988

대덕망에 Osi 프로토콜을 구현하기 위한 일련의 작업들은 ETRI의 Osi Group 에 의해서 1985년경부터 시작이 되었다. 현재 Osi의 FTAM(File transfer Access and Managenemt) 프로토콜과 ACSE (Association Control Service Element) presentation 계층 session 계층이 상위계층 프로토콜로 구현되었으며, 상위 계층에서 필요한 통신 서비스를 제공하귀 위해서 transport 계층 및 대덕 man의 통신 서비스를 이용하기 위한 intertiace 들이 구혀되었다. 이러한 interface는 순차적으로 jualring optical cable을 control 하여 대덕 man에 위치한 node들 사이에 Osi 상위계층 프로토콜의 서비스를 제공하게 된다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.7
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• pp.1524-1528
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• 2005

In this paper, we analyses of a traffic for authentication signaling in third generation mobile sensor network. In universal mobile telecommunication system, authentication functions are utilized to identify and authentication a mobile station and validate the service request network services. The authenticating parties are the authentication the serving general packet radio service support node access the authentication center to obtain the authentication with the mobile station. In this paper, we propose that the automatic cost-effective solution size of the authentication vector array.

• Communications for Statistical Applications and Methods
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• v.10 no.3
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• pp.795-804
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• 2003

In this article, a tomography for the estimation of the origin-destination(OD) traffic intensities in dynamic routing network is considered. Vardi(1996)'s approach based on fixed route is not directly applicable to dynamic routing protocols, which arises from the fact that we cannot access the route at every observation time. While it uses link-wise traffics as the observations, the proposed method considers the triple of ingress/outgress/relayed traffics data at each node so that we can transform the problem into a routing-independent tomography. An EM algorithm for implementation and some simulated experiments are provided.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.162-167
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• 1999

ATM technology is well developed. Small-scale access node and edge switches are introduced in the network. Large scale ATM core switches are prepared for backbone application. Currently, Internet traffic is increasing so rapidly and we need to consider effective way of accommodating the volume of traffic. In the other hand, QoS and traffic engineering concept is required in the Internet services. Here, in this paper, two technologies are explained and suggested for integration of networks for future ATM based IP network.