• Journal of KIISE:Computer Systems and Theory
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• v.26 no.11
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• pp.1391-1400
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• 1999

이동 통신은 대기를 전달매체로 하고 이동단말기를 사용하기 때문에 가로채기나 불법사용과 같은 공격에 취약하다. 이를 극복하기 위해, 이동 통신 환경에서 이동단말기와 기지국 사이에 안전한 통신을 제공하기 위한 많은 프로토콜들이 제안되어왔다. 그러나 이동단말기의 부족한 계산능력과 전력량 때문에 공개키를 이용한 프로토콜들은 많은 장점에도 불구하고 충분히 활용되지 못했다. 본 논문에서는 이동 통신 환경에서 기지국과 이동단말기 사이의 상호인증 및 세션키 공유 프로토콜들의 성능을 향상시킬 수 있는 기법을 제안한다. 본 논문에서 제안하는 기법은 이동단말기의 비밀 정보를 기지국에게 드러나게 하지 않으면서 많은 계산을 기지국으로 하여금 대신 수행하도록 하는 것이다. 제안된 기법은 기존의 프로토콜들을 최대 5배까지 성능을 향상시키며 해당하는 만큼 이동단말기의 전력량 소모를 감소시킬 수있다.Abstract Mobile communication is more vulnerable to security attacks such as interception and unauthorized access than fixed network communication. To overcome these problems, many protocols have been proposed to provide a secure channel between a mobile station and a base station. However, these public-key based protocols have not been fully utilized due to the poor computing power and small battery capacity of mobile stations. In this paper, we propose techniques for accelerating public-key based key establishment protocols between a mobile station and a base station. The proposed techniques enable a mobile station to borrow computing power from a base station without revealing its secret information. The proposed schemes accelerate the previous protocols up to five times and reduce the amount of power consumption of mobile stations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.5
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• pp.921-927
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• 2006

The current DGPS technique is many problems that is permission of radio station using RF Wireless Modem, that is influence of geographic obstacle using radio wave, that is frequency interference, that is finiteness of frequency resources. In this paper, we are solved many elements, IM(Interface Module) replaces RF Wireless Modem, we suggest transmission technique of correction message using mobile phone, we researched Interface Module development which is linkage of DGPS receiver and mobile phone. IM can transmit correction message passing RS-232 port and modem communication control. IM of base station is initialized RS-232 port and modem to move station for correction message transmission, IM waited response mode. IM of move station is initialized RS-232 port and modem, IM requests hand shaking to base station, completed connection establishment. Users are worked Differential surveying using receiving correction message between mobile phones.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8C
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• pp.605-612
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• 2008

This paper researches the estimating location using repeater effect adjustment method in CDMA based system. Repeaters are commonly used by commercial and amateur radio operators to extend signals in the radio frequency range from one receiver to another. The repeater signals are increasing arrival time from base station to mobile station. So if we calculates the mobile station using repeater signals, the estimating position error is increased. However nobody researched about adjusting repeater effects. This paper proposes repeater effect adjustment algorithm. For adjusting repeater effects, we make the triangle using mobile station, reference base station and neighbor base station, and then detect the repeater effects using the triangle characteristic. The proposed method system showed the improved performance in estimating parameters and locating positions by computer simulations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1998.05a
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• pp.126-131
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• 1998

DECT는 기존의 사설 교환시스템에 이동통신 서비스를 제공하기 위한 디지탈 방식의 무선통신 규약으로 ETSI에 의해 표준화되었다. 본 논문에서는 사설교환기에 이동통신 서비스를 제공하기 위해 ETSI에 의해 권고된 DECT 표준안을 기초로 DECT 교환국과 기지국을 개발하였으며, 이의 구현 방법에 관하여 서술하였다. DECT 시스템의 호제어타스크를 구현함으로써 이동중 착발신이 가능하도록 하였고, 부분해제 기능을 구현함으로써 효율적인 트랜젝션의 처리가 가능하도록 하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.7-9
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• 2003

기존의 VOD 서비스는 일반적으로 단일 서버 모델을 사용하여 서비스 되어왔다. 그렇지만 단일 서버 모델의 VOD 서비스는 서버 용량의 확장에 따른 오버헤드가 크며 서버 고장시 VOD 서비스를 실시할 수 없는 문제점이 있다. 따라서 이런 문제점들을 해결하고자 병렬 서버 구조에 기반을 둔 VOD 서비스에 대한 연구가 이루어지고 있다. 기존의 유선 네트워크에서의 병렬 서버 구조에 기반을 둔 스트림 전송에 관한 연구가 일부 진행되어 왔지만 무선 네트워크와 관련해선 그러한 연구가 거의 없으며 있어도 아주 이상적인 경우를 가정하였다. 이동통신의 급속한 발전으로 현재 이동국들은 멀티미디어 서비스를 받을 수 있게 되었으며 앞으로는 이동국들에 제공되는 멀티미디어 서비스 역시 QoS가 보장되어야 한다. 따라서 본 논문에서는 무선 모바일 환경에서 병렬 서버 구조를 사용하여 멀티미디어 스트림을 전송함으로서 기지국외 혼잡 상황에도 이동국에서 QoS를 보장할 수 있는 방법을 제시한다. 시뮬레이션 분석 결과를 보면 기지국의 혼잡 상황에서 병렬 서버 구조에 기반을 두고 멀티미디어 스트림을 전송하게 되면 단일 서버로 멀티미디어 스트림을 전송할 때보다 이동국의 수신 상태가 42% 향상됨을 알 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.13-23
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• 2002

A mobile host is prone to failure due to lack of stable storage, low bandwidth of wireless channel, high mobility, and limited battery life on the wireless network. Many researchers have studied to overcome these problems. For high level Availability in the cellular networks, it is necessary to consider recovery from the failures of mobile support stations as well as mobile as mobile hosts. In this paper, we present modified trickle scheme for recovery from failures of Mobile Support Station based on checkpointing scheme and analyze and compare the performance. We propose and analyze the performance of two schemes : one is waiting recovery scheme for the mobile support station having the last checkpoint and the other is searching the new path to the another mobile support station having the checkpoint.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4C
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• pp.333-341
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• 2002

This article is written to make a foundation for effective radio network engineering by enabling the accurate traffic assumption between Base Station (BTS : Base Station Transceiver Subsystem) md Repeater through the scientific and systematic analysis of mobile traffic dealt within CDMA Base Station. Among these, Repeater, having direct physical connection with BTS, simply does the remote relay function but the volume of the traffic flowed into the repeater is not accountable. The total BTS traffic is the sum of traffic dealt by the BTS and multiple Repeaters. In this article, we tried traffic analysis of this kind by adopting RTD (Round Trip Delay) which is specially designed to measure distribution of the distance between the Base Station and the Mobile station by differentiating the traffic dealt by BTS from traffic dealt by Repeaters. The fact that the connection between mobile station and BTS via Repeater (which is located remotely) yields far more delay than the direct connection between mobile station and BTS is the clue of this article. Based on this fact, Time Delay equipment was put at the receiving side of the Repeater to add certain amount of delay to the traffic to BTS and the result showed that the 99.78% of the traffic can be identified.

• The Journal of the Korea Contents Association
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• v.2 no.1
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• pp.104-112
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• 2002

Dynamic Handoff Control Scheme (DHCS), which is propose d in this paper, suggests the method to request handoff at the optimal time. To accomplish this, DHCS measures the speed of the mobile station and sets the pilot strength for handoff request. When the pilot strength of the current base station is bigg or than the pilot strength for handoff request, which means the pilot strength of the current base station is big enough so the possibility of the call to be disconnected is low, DHCS doesn't request for the handoff even though the pilot strength of the adjacent base station is bigger than the pilot strength of the curent base station. DHCS guarantees the QoS (Quality of Service) by processing the handoff calls prior to new calls at the base station and providing continuous service for the mobile station by setting the priorities for the calls according to the queue waiting time transmitted from the mobile stations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.1 no.1
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• pp.47-54
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• 1997

New algorithms for frequency channel assignment in small cellular mobile radio system are proposed. The algorithms are for a channel assignment method which control the transmitter power level based on the distance between the cell site and the mobile unit. These algorithms are such that any channel can be used by any cell site and mobile unit, as long as a required threshold level of carrier to interference ratio is maintained. As the cochannel reuse distance decreases, the proposed algorithms have given an increase in capacity in comparison to a fixed channel assignment.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.10a
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• pp.12-17
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• 1999

WATM(Wireless ATM)에서의 매체접근제어(Medium Access Control)는 QoS를 보장하기 위해 다양한 방식들이 제안되어 왔다. 현재까지 제안되어 온 매체접근제어 방식들은 시분할 다중화 방식 (TDMA)과 예약경쟁방식을 주로 사용하고 있다. 이때 활용되는 기능에는 QoS를 보장하기 위해 통계적 다중화, 스케쥴링 또는 예약 방식 등이 있는데 경쟁 방식은 아직까지 slotted-ALOHA를 그대로 사용하고 있다. Slotted-ALOHA방식의 단점을 개선하기 위하여 통계적 방식으로 경쟁을 제어하거나 물리적 방식으로 경쟁을 분리시켜 그 효율을 향상 시켜왔으나 우선 순위가 같은 이동국들이 많을 경우에는 해결할 방법이 없었다. 이러한 문제점들은 기지국 중심의 경쟁방식이라는 점이 그 문제를 해결하는데 있어서의 걸림돌이다. 본 논문에서는 이미 슬롯을 할당받은 동료 이동국에게 예약요청을 피기백킹(piggybacking)함으로써 신속하게 슬롯을 할당을 받을 수 있는 분산 경쟁방식을 제안한다.