• 정보학연구
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• 제7권4호
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• pp.21-30
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• 2004

VPN은 공중망을 이용하여 전용선을 구축할 수 있는 기술로서, 전송되는 데이터에 대한 보안기능을 제공한다. 또한 권한을 가진 사용자만이 접근할 수 있도록 암호 및 보안 알고리즘을 사용한다. 본 논문에서는 IPsec과 VPN에 관한 기술을 정리하고, 원격접속 VPN 성능분석을 위한 파이럿 시스템을 구축하였다. 그리고 단일사용자에 대한 원격접속 VPN의 성능을 분석하고, 5명의 사용자가 동시 사용하는 경우에 대하여 원격접속 VPN의 성능을 분석하였다.

• Journal of Communications and Networks
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• 제11권1호
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• pp.1-10
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• 2009

In this paper, we propose a chip-level detection and a spectral-slice scheme for the tunable-transmitter/fixed-receiver (TTFR)-based asynchronous spectral phase-encoded optical codedivision multiple-access (CDMA) system combined with timeencoding. The chip-level detection can enhance the tolerance of multiple access interference (MAI) because the channel collision does not occur as long as there is at least one weighted position without MAI. Moreover, the spectral-slice scheme can reduce the interference probability because the MAI with the different frequency has no adverse effects on the channel collision rate. As a result, these techniques mitigate channel collisions. We analyze the channel collision rate theoretically, and show that the proposed system can achieve a lower channel collision rate in comparison to both conventional systems with and without the time-encoding method.

• 산업기술연구
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• 제28권B호
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• pp.245-250
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• 2008

Recently, mobile devices have supported wireless LAN as well as bluetooth, where the services such as heterogeneous network access and seamless mobility connection are important. Even though the mobility and physical network might be varied, an efficient communication mechanism for the network access and a robust mobility management of mobile devices are needed. In this paper, we design and implement a Bluetooth system with mobile LAN access capability. The proposed system has the following features; 1) IP connection is enabled by BENP in the link layer, 2) The networks devices of heterogeneous mobile devices are integrated into a single virtual network interface, 3) IP mobility between the bluetooth and wireless LAN is supported by mobile IP. The experimented results show that the packet loss and delay time during the handover duration is reduced by predicting the handover among different networks followed by the setup of any required parameters in advance.

• 한국정보통신학회논문지
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• 제1권1호
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• pp.105-111
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• 1997

This Paper Proposes a new efficient system design strategies for the acoustic-based underwater multiple modem and media access control protocol. The system aims to establish the acoustic-based communication network of an underwater vehicles for deep sea mining, which ensures a certain level of maximum throughput regardless of the propagation delay of acoustic and allows fast data transmission through the acoustic-based multiple channel. A media access control protocol for integrated communication network and it's acoustic-based communication modems that allows 'peer-to-peer' communication between a surface mining plant multiple underwater system is designed, and the proposed media access control protocol is implemented for its verification. Furthermore, a proposed design strategies which make it possible to control the multiple vehicle for an underwater mining is presented in this paper.

• 전기학회논문지P
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• 제60권1호
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• pp.37-44
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• 2011

HSPA(High Speed Packet Access)/HSPA+ is a combined 3GPP(Third Generation Partnership Project) standard of HSDPA(High Speed Downlink Packet Access) and HSUPA(High Speed Uplink Packet Access). The standard can provide the high speed multimedia service against the 3GPP release 99 standard. In order to test the 3GPP HSPA/HSPA+ terminal performance, the measurement hardware is required for the evaluate the transmitted signal of HSPA/HSPA+ terminals. Agilent Technologies and Innowireless produce the measurement equipments for HSPA/HSPA+ terminals. Generally speaking, the receiving algorithms in normal modems cannot be used directly to the measurement system due to the lack of the algorithm accuracy. In this paper, we propose the new receiver algorithm for precise measurement of 3GPP HSPA/HSPA+ terminal signal, and implement measurement functionality for performance measurement of the 3GPP HSPA/HSPA+ terminal by using software. The proposed 3GPP HSPA/HSPA+ signal measurement algorithm can be used for the commercial system through code execution speed optimization.

• 정보통신설비학회논문지
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• 제8권4호
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• pp.201-206
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• 2009

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference (ISI) or Multiple Access Interference (MAI) to degrade the performance of W-CDMA (Code Division Multiple Access) system. Constant Modulus Algorithm (CMA) which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. Consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.

• Journal of Communications and Networks
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• 제7권2호
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• pp.135-143
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• 2005

This paper presents an investigation of satellite radio access technology for beyond IMT-2000 systems. Although we could not see any active role of a satellite system in the 3G networks, satellite system will provide strong advantages in future systems for certain applications. Because a satellite link has longer round trip delay than a terrestrial link, we need technologies that would make the satellite component especially efficient. After presenting the satellite radio interface of the 3G system, we suggest several points which need to be considered in the beyond 3G systems. We also suggest a few candidate technologies with various simulation results.

• 대한임베디드공학회논문지
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• 제8권5호
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• pp.255-264
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• 2013

Resolving of memory access latency is one of the most important problems in modern embedded system design. Recently, tons of studies are presented to reduce and hide the access latency. Burst/page data transfer modes are representative hardware techniques for achieving such purpose. The burst data transfer capability offers an average access time reduction of more than 65 percent for an eight-word sequential transfer. However, solution of utilizing such burst data transfer to improve memory performance has not been accomplished at commercial level. Therefore, this paper presents a new technique that provides the maximum utilization of burst transfer for memory accesses with local variables in code by reorganizing variables placement.

• 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.

• 전자공학회논문지
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• 제53권2호
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• pp.3-9
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• 2016

본 논문에서는 무선 및 이동통신을 위한 클라우드 무선 가입자 네트워크를 지원하는 프론트홀에서 무선 라디오파의 광섬유 전송망의 기술을 제안하고 구현한다. 하향 링크는 OFMD (orthogonal frequency division multiplexing) (O기법을 사용하였고 상향방향의 전송은 SC-FDMA (single carrier-frequency multiple access) 방식으로 구현하였다. 64, QAM, 16QAM, QPSK 등 다양한 변조 방식에 대해 시스템 파라메터를 도출하고 측정치를 기반으로 성능을 분석하였다.