• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2007년도 춘계학술발표대회
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• pp.1096-1097
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• 2007

We address the data confidentiality for wireless broadband (WiBro) networks. In WiBro, as the channel is wireless in nature, it suffers from passive and active attack. Passive attack, for example is to decrypt traffic based on statistical analysis and active attack is to modify traffic or inject new traffic from unauthorized mobile stations. Due to high mobility, frequent session key distribution is a bottleneck for the mobile stations. In aspect of WiBro, there is a communication between mobile station to base station, and also in mobile station to mobile station. It is expected to ensure data confidentiality while maintaining minimum overhead for the resource constrained mobile stations. In this paper, we proposed a security framework based on the concept of hyper-encryption to provide data confidentiality for wireless broadband networks.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.25-28
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• 1999

Consider connection-oriented wireless cellular net-works. To establish a circuit or virtual circuit in such a network, a paging message is broadcast over a region at which the destined mobile station is presumed to reside, (identified as a paging area). For an effective paging mechanism, it is desirable to provide the location information of mobile stations to the network. In this paper, we consider a mobile controlled location update scheme under which each mobile station periodically reports its current location information to the network by using an inherent timer (without measuring the power of signals transmitted from base stations). Based on the latest information about a mobile station's location, a paging area is selected to page the mobile station. Note that under this scheme, a mobile station may not yet have reported its location change while sojourning out of the current paging area. In such situation, the mobile station can not receive a paging message destined to it. Frequent location updates can reduce the paging failure rate incurred by mobile stations'sojourning out of the paging area. However, larger bandwidth is needed for location update as the location update rate is increased. On the other hand, as the size of the paging area is increased, the paging failure rate is decreased, while larger bandwidth is required for paging. Thus, we first present a model for mobility, paging and location update processes, and secondly investigate the effect of network parameters on the paging failure rate and the amount of bandwidth used for paging and location update. Finally, we formulate problems to find proper values for the location update rate and paging area size under the constraints on the bandwidth usage levels for location update and paging.

• ETRI Journal
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• 제26권5호
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• pp.493-496
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• 2004

An effective paging strategy is essential for improving the utility of radio channels. This paper proposes a two-step paging strategy which involves using base station paging agents to page a single cell at each paging. An analytical model is used to evaluate the performance of the proposed strategy. The proposed strategy is compared with the traditional simultaneous paging strategy and a recent proposal using the base station paging agents. The numerical results showed that the proposed strategy proficiently reduces paging cost on radio channels compared with other paging strategies.

• 한국통신학회논문지
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• 제27권1B호
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• pp.13-23
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• 2002

이동 호스트는 무선 통신망의 낮은 대역폭과 호스트들의 이동성, 부족한 저장장치와 배터리 수명 등으로 인하여 결함 발생 가능성이 높다. 이동 호스트의 결함에 효율적으로 대처하기 위한 결함 허용 기법에 관한 연구가 많이 진행되어 왔다. 셀룰라 네트워크에서는 이동 호스트이외에도 이동 호스트를 연결시키는 기지국은 보다 높은 수준의 가용도를 요구하므로 기지국의 결함에 대한 연구도 필수적이다. 본 논문에서는 이동 호스트 결함 복구를 위한 체크포인팅 기법을 기반으로 기지국 결함 복구를 위한 체크포인팅 이중화 기법을 제안하고 성능을 분석하였다. 또한 이동 호스트의 결함 복구를 위해 체크포인트가 존재하는 기지국의 복구를 기다리는 방법과 다른 기지국의 체크포인트를 이용하는 방법의 성능을 비교 분석하였다.

• 한국지능시스템학회논문지
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• 제22권5호
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• pp.577-582
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• 2012

이동통신망에서는 이동국에서 채널할당 요청이 있을 때 교환국에서 각 기지국에 속한 이동국에 채널을 할당한다. 채널을 할당하는 방식에는 고정채널할당방식과 동적채널할당방식이 있으며 이를 조합한 하이브리드방식이 주류를 이룬다. 주파수를 잘 할당한다는 것은 그만큼 자원을 효율적으로 사용하고 고객에게 양질의 서비스를 제공하는 길이기도 하다. 본 논문에서는 채널을 할당할 때 채널간 간섭을 최소로 하고 채널을 할당하기까지의 시간과 횟수를 최소화하는 방안을 적용한 방식을 제안한다. 이를 구현하기 위해 유전 알고리즘의 프로세서 단계인 검증단계를 통하여 재생산 단계를 거치므로 제안 방식의 정확성과 효율성을 나타낸다. 또한 시뮬레이션을 통해 다른 방식과 비교 검토하여 제안 방식의 효율성을 검증한다.

• 한국통신학회논문지
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• 제22권4호
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• pp.804-811
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• 1997

In the CDMA mobile communication system, reverse power control can be used to minimize the interference level for a good quality of the voice channel, and used to maxmize the system capacity. In this paper, we have analyed the environment of the K-parameter and the access procedure for the mobile station, and proposed a new algorithm for the access probe procedure of the station. K-parameter is determined according to the environment of the base station and access probe can adaptively control the power according to the position changes of the mobile station or the rapid and various state changes of the channel. Simulation results in the limited test environment show that it can increase the system capacity and decrease the power comsumption of the mobile station while maintaining the good and stable quality of the voice channel.

• 한국통신학회논문지
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• 제35권4A호
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• pp.394-400
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• 2010

Mobile Multi-hop Relay (MMR) 시스템은 커버리지 확장과 Base Station (BS) 내의 전송률 증대에 의해 무선 액세스 네트워크의 처리량을 증가시킬 수 있다. 넌-트랜스패런트 모드 (non-transparent mode) Relay Station (RS) 를 갖는 MMR 시스템의 기존 연구에서는 Mobile Station (MS)의 채널 선택 과정, 동일 채널 간섭, 그리고 Multi-hop Relay Base Station (MR-BS)과 RS의 커버리지 비율은 고려하지 않았다. 본 논문에서는 다양한 토폴로지를 갖는 멀티셀 환경에서 MMR 상향링크 시스템의 성능을 분석한다. 성능은 호 발생률에 따른 호 차단 확률, 채널 사용률, outage 확률 그리고 시스템 처리량으로 나타낸다. 결과를 통해 MR-BS와 RS의 커버리지 비율이 7 대 1일 때 시스템 처리량이 가장 높음을 알 수 있다.

• 한국수소및신에너지학회논문집
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• 제31권6호
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• pp.605-613
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• 2020

In July and October of this year, the government announced the 'Green new deal plan within the Korean new deal policy' and 'Strategies for proliferation of future vehicles and market preoccupation'. And, in response to changes in the global climate agreement, it has decided to expand green mobility such as electric vehicles and hydrogen electric vehicles with the aim of a "net-zero" society. Accordingly, the goal is to build 310 hydrogen refueling stations along with the supply of 60,000 hydrogen vehicles in 2022, and the hydrogen infrastructure is being expanded. however, it is difficult to secure hydrogen infrastructure due to expensive construction costs and difficulty the selection of a site. In Korea, it is possible to build a mobile hydrogen station according to the safety standards covering special case of the Ministry of Industry. Since the mobile hydrogen station can be charged while moving between authorized place, it has the advantage of being able to meet a large number of demands with only one hydrogen refueling station, so it is proposed as a model suitable for the early market of hydrogen infrastructure. This study demonstrates the establishment of a hydrogen refueling station by deriving a virtual accident scenario for leakage and catastrupture for each facility for the risk factors in a mobile hydrogen station, and performing a quantitative risk assessment through the derived scenario. Through the virtual accident scenario, direction of demonstration and implications for the construction of a mobile hydrogen refueling station were derived.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.461-464
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• 2003

This paper explains the impact of frequency error on the performance of WCDMA mobile communication systems and what brings about the frequency error between the base station and the mobile station, and then presents automatic frequency error correction method in mobile receiver. On the basis of system requirement related to frequency stability, the integration test between the base station and the mobile station was accomplished. After applying automatic frequency error correction to mobile receiver, 4 Hz of frequency error at transmitting frequency was obtained. The result met frequency error requirement of 0.1ppm(about 200 Hz). Performance degradation due to frequency error was measured by means of Error Vector Magnitude (EVM)

• ETRI Journal
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• 제19권3호
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• pp.116-140
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• 1997

The base station transceiver subsystem (BTS) of the CDMA Mobile System is interfaced to mobile stations over the air and to the wired network through a packet switched interconnection network. The potential benefits of CDMA technology are achieved when the transmitter and the receiver are properly designed and implemented. The physical layer of the interface at the base station is implemented with the CDMA ASICs and control circuits in channel card of the BTS. We present the design perspectives and structural illustration of the BTS. Base station modem ASICs and their control to implement the CDMA receiver, Baseband and RF signal processing blocks, and BTS controller are described. Elaborate power control is essential to ensure the high capacity which is one of advantages of the CDMA technology. The closed loop reverse link power control and the forward link power control operated in the BTS are described.