• ETRI Journal
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• v.19 no.3
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• pp.83-97
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• 1997

The CDMA Mobile System (CMS) has been developed by Electronics and Telecommunications Research Institute (ETRI) and field-tested for commercial service deployment in Korea. The project was started in 1989 and completed in 1995 with the CMS commercial test. During the course of development, there had been active technical cooperation with Qualcomm, Inc. and Korean manufacturers. The CMS adopted the basic CDMA concepts conforming to Korean CDMA system which was derived form IS-95. The CMS functions are allocated to subsystems by considering efficiency and expandability. The CMS consists of mobile stations and the infrastructure which is composed of base stations, mobile exchanges and home location register/authentication center. The commercial field tests performed both in Taejon and Seoul have indicated that the CMS capacity is 10 to 15 times larger than that of AMPS. This paper overviews the development history, system characteristics, architecture and test results.

• Electronics and Telecommunications Trends
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• v.22 no.3 s.105
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• pp.1-11
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• 2007

USN 기반 텔레매틱스 서비스는 텔레매틱스 시장의 성숙, 유비쿼터스 사회에 대한 열망 및 u-City 사업의 가속화 등에 기인하여, 도로 교통 인프라에 USN 기술을 적용함으로써 대두하게 된 새로운 개념의 서비스이다. 본 고에서는 USN 기반 텔레매틱스 서비스 및 시장 동향, 해외사례, 관련 특허 및 국내기술개발 동향을 살펴보고자 한다. 현재 중점을 두는 구체적인 서비스는 도로 및 교차로 환경에서의 상황정보 제공 서비스로 도로 위에 설치된 T-센서노드를 이용하여 시간 및 방향에 따라 진입하는 차량의 실시간 위치, 속도, 시간 정보를 수집한 뒤 센서 네트워크를 통해 T-베이스스테이션으로 관련 정보를 전달하고 차량 충돌이라는 교통사고를 미연에 방지하기 위한 상황인지적 서비스를 제공하는 것이다. 이를 위한 핵심 기술로 T-센서노드 기술, 센서노드 네트워크 기술 및 T-베이스스테이션 기술이 있으며 중점적으로 개발하고 있다.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.6
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• pp.9-17
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• 1994

ATM (Asynchronous Transfer Mode) has a fixed-length packet transport scheme. It is one of the promising proposals in B-ISDN.Since the packet length is fixed, it can be potentially to perform the various service to users. In this paper, a queueing model for an ATM multip`exer loaded by CBR and ON/OFF input sources is considered, and the two-queue system which each type of input sources has a queue with a finite capacity is analyzed. The cell loss probabilities for a performance measures of ATM multiplexer are derived, and are also evaluated through numerical examples. As a result, the cell loss probability of ON/OFF sources for the queue size is rapidly decreased when the multiplexed number and burstiness are increased. Since cells of the CBR source have lower priority than cells of the ON/OFF source, cell loss probabilities of CBR sources are accordingly high independently of CBR cell arrival rate when the number of CBR sources is large.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.8
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• pp.1-10
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• 1994

In this paper load redistribution algorithm to allow fault-tolerance by redistributing the workload of n failure nodes to the remaining good nodes in distributed systems are investigated. To evaluate the efficiency of the algorithms a simulation model of algorithms is developed using SLAM II simulation language. The job arrival rate service rate failure and repair rate of nodes and communication delay time due to load migraion are used as parameters. The result of the simulation shows that the job arrival rate failure and repair rate of nodes do not affected on the relative efficiency of algorithms. If the communication delay time is greater than average job processing time algorithm B is better. Otherwise algorithm C is superior to the others.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.3
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• pp.47-54
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• 1996

In this paper we propose a new timing recovery method by means of utilizing service data filling rate instead of timing information of transmitter. A proposed algorithm controls the phase locked loop in the opposite direction ot data filling rate of FIFO in receiver, and it is based on the fact that average of cell jitters is zero. The proposed method is simple compared with timing information method of transmitter. It can be utilized for timing recovery in synchronous digital hierarchy as well as in plesiochronous digial hierarchy without common reference clocks in end-to-end erminals. We implement the interactive video communication system and test the proposed algorithm. As a result, we hav econfirmed that it yields good perfomrnces in terms of jitters characteristics and hardware complexity.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.7
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• pp.11-20
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• 1996

In this paper, the performance of the IeEE 802.4 token-passing is analyzed under the assumption that all nodes have finite buffers and finite THT (token tolding time). The loads generated at nodes are assumed to be asymmetric. The priority mechanism is not considered. This paper derives an approximate matrix equation of the queue length distributin in terms of the number of nodes, frame arrival rate and mean service time of a frame in steady state. Based on the matrix equation, the mean token rotation time, the mean waiting time and the blocking probability are derived analytically. the analytic results are compared with simulation results in order to show that the deviations are small.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.8
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• pp.1-9
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• 1997

Soft handoff provided in CDMA cellular system has much advantage such as better service quality, interference control and low call dropping probability. In this paepr, we propose an optimum resource reservationscheme for handoff calls in the CDMA cellular system to increase the soft handoff probability in handoff. In the proposed scheme, resources of each frquency channel are reserved for handoff according to the number of its neighbot cells serving the same frequency channel. A performance analysis shows that the soft handoff probability of the proposed scheme is higher than that of conventional scheme disregarding the condition of frquency assignment of neighbot cells, and that ever frequency channel served by neighbor cells should reserve more than one traffic channel for handoff to get good performance.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.8
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• pp.27-36
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• 1997

In this paper, we propose a locating strategy using a cache based on the distributed call processing stucture. In our stategy, each originating call server, withc is responsible for call setup, has a cache to memorize the service ratio of call server which serves the called terminal.We present performance comparison of the proposed strategy with the existing strategy via simulation. We can reduce the cost for call setup because the originating call server can simpley establish a call without tracing the location of the called terminal. The proposed strategy also reduceds network loads caused by signaling at call setup time and lessens the frequency of queries for the database systems which can be a bottleneck when it serves many subscriber.

• Journal of information and communication convergence engineering
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• v.9 no.1
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• pp.6-10
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• 2011

In Korea, overall disaster prevention system or 119 emergency rescue system has been established to protect life and fortune of citizens. This system supports command & control operation, emergency 119 caller location indicator, automatic formation of fire troops and dispatch, and emergency management. To do this, various new information technologies such as GIS, telematics, CTI and TTS are applied to implement the system. In the future, however, it is not impossible to prevent a large scale disasters caused by world climate environment change and complication of city culture using the current system. In this paper, we propose enhancement plan for overall disaster prevention system to solve this problem.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.5
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• pp.17-26
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• 1998

B-ISDN has many advantages to provide multimedia, image transfer, etc. Recently, ABR service has been proposed in order to satisfy user's various requirements in it. In this paper, we propose a new ABR flow control algorithm called CAPRO. This algorithm uses the buffer proportional to propagation delay and controls the traffic on a link-by-link basis in order to minimize the effect of propagation delay. In order to use buffer more efficienctly, we define the request cell and the control cell. Then, we analyze our algorithm using mathematical model, simulate it using SLAM system, and compare to the existing EPRCA. As a result, our algorithm has the benifit of the throughput, cell loss probability, and fairness.