• Journal of Communications and Networks
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• v.11 no.2
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• pp.187-195
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• 2009

The application of mathematical analysis to the study of wireless ad hoc networks has met with limited success due to the complexity of mobility, traffic models and the dynamic topology. A scenario based universal mobile telecommunications system (UMTS) time division duplex (TDD) opportunistic cellular system with an ad hoc behaviour that operates over UMTS frequency division duplex (FDD) licensed cellular network is considered. In this paper, we present a new routing metric which overall improves system performance in terms of interference and routing which operate in an ad hoc network in an opportunistic manner. Therefore we develop a simulation tool that addresses the goal of analysis and assessment of UMTS TDD opportunistic radio system with ad hoc behavior in coexistence with a UMTS FDD primary cellular networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.8
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• pp.924-927
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• 2016

In this paper, we consider a cumulative distribution function (CDF)-based opportunistic scheduling for downlink transmission in a cellular network consisting of a base station and multiple mobile stations. We present a closed-form formula for the average starvation period of each mobile station (i.e., the length of the time interval between two successive scheduling points of a mobile station) over Markov time-varying channels. Based on our formula, we investigate the starvation period of the CDF-based scheduling for various system parameters.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1994.10a
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• pp.57-63
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• 1994

• Journal of Korea Multimedia Society
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• v.16 no.5
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• pp.601-609
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• 2013

One of the most serious factors constraining the next generation cellular mobile consumer communication systems will be the severe co-channel interference experienced at the cell edge. Such a capacity-degrading impairment combined with the limited available spectrum resource makes it essential to develop more spectrally efficient solutions to enhance the system performance and enrich the mobile user's application services. This paper proposes a unique hybrid method of frequency hopping (FH) and subcarrier-reuse-partitioning that can maximize the system capacity by efficiently utilizing the available spectrum while at the same time reduce the co-channel interference effect. The main feature of the proposed method is that it applies an optimal combination of different frequency reuse factors (FRF) and FH-subcarrier allocation patterns into the partitioned cell regions. From the simulation results, it is shown that the proposed method can achieve the optimum number of subcarrier subsets according to the frequency-reuse distance and results in better performance than the fixed FRF methods, for a given partitioning arrangement. The results are presented in the context of both blocking probability and BER performances. It will also be shown how the proposed scheme is well suited to FH-OFDMA based cellular systems aiming at low co-channel interference performance and optimized number of subcarriers.

• Journal of the Korea Computer Industry Society
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• v.5 no.9
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• pp.1095-1100
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• 2004

The computer system is gradually complicated because of explosive growth of computer system and IT technology. For efficient management of complicated system, system load monitoring technology is essential. In this paper, we is implemented the real-time load monitoring system based mobile than the traditional methods that are used load-related commands in system manager or specific load application programs based connected wire. Advantage of implemented load monitoring system in this paper is freely saw load information in time and space though mobile method like as PDA, cellular phone, more than traditional methods intime and space.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.345-347
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• 2008

실제 휴대폰 환경에서 쓰이고 있는 전력 시스템이 어떻게 되어 있는지 고찰해보고, 어떤 것들이 문제가 되고 있으며, 그 해결방안으로는 어떤 것들이 있는지 알아본다. 각 regulator의 정의와 그 spec에 대하여 장단점 분석과 함께 실무적으로 어떻게 응용되고 있으며 미래의 발전방향은 어떻게 될 것인지 고찰한다. SoC(System on Chip)의 결정체인 휴대폰에서 전력 시스템 디자인이 차지하는 그 영향에 대해 논하고 그 application 관점에서 체크리스트를 만들어보기로 한다.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.85-90
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• 2005

The advance of mobile and telematics technologies has produced vehicles with various convenient services for drivers. Specifically lots of researches and several technologies have been developed to provide services of a remote vehicle diagnosis and control. The existing and representative product for a vehicle control is a RCS (remote control system), but it has a problem of short control distance and fragile security. In this paper, a telematics terminal embedded with CDMA and GPS is designed, which can be connected to the Internet. It allows a driver with a cellular phone to remotely diagnosis and control a vehicle via wireless network and SMS.

• ETRI Journal
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• v.19 no.3
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• pp.259-280
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• 1997

This paper briefly explains the configuration of CDMA Mobile System (CMS) test bed. The measured fading and delay results of CDMA signal in Taejon area are shown. In comparison to other cellular systems, there are more parameters in the CDMA systems that affect system performance and capacity. We performed the optimization test of the selected parameters and present the effect of each parameter on the performance. This paper presents the capacity and performance test results of CMS. The capacity test was performed on ETRI site of three sectors in Taejon area. The performance tests include call completion rate, busy hour call attempt, and the delay characteristics of voice.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.126-129
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• 1999

In this paper, it is assumed that a mobile radio channel is a Rayleigh distributed multipath fading channel and Erlang capacity and equivalent channel numbers are calculated for the reverse link of a imperfect power controlled DS/CDMA cellular system considering both shadowing and multipath fading. The DS/CDMA blocking probability is calculated based on a new analysis method that considers Erlang capacity and ICF(interference correction factor) using the median value of $E_{b(i)}$/ $I_{o}$ corresponding to each reverse link user. It is showed that the effect of multipath fading must not be ignored in Erlang capacity of the IS-95 DS/CDMA cellular system and the Erlang capacity is decreased according to the increase of the deviation of the imperfect power control, to the decrease of the processing gain, to the increase of the voice activity.y.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.297-300
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• 2004

In cellular communication, subscriber authentication is an essential technique. The mobile station should operate in conjunction with the base station to authenticate the identity. In CDMA system, authentication is the process by which information is exchanged between a mobile station and base station for the purpose of confirming the mobile station. A successful authentication process means that the mobile station and base station process identical sets of shared secret data(SSD). SSD can be generated by authentication algorithms. The cryptographic hash function is a practical way of authentication algorithms. In this paper, we propose and implement MD5 and SHA-1 with modified structure.