• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.237-241
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• 2008

Femtocells are cellular access points that connect to a mobile operator's network using residential DSL or cable broadband connections. They have been developed to work with a range of different cellular standards including CDMA, GSM and UMTS. Like legacy base station, the frequency accuracy and phase alignment is necessary for ensuring the quality of service (QoS) for applications such as voice, real-time video, wireless hand-off, and data over a converged access medium at the femtocell. But, the GPS has some problem to be used at the femtocell, because it is difficult to set-up, depends on the satellite condition, and very expensive. So, some techniques are discussed to alternate with the legacy GPS system. NTP, PTP, Synchronous Ethernet use the ethernet to synchronize distributed clocks in packet networks. AGPS support reliable position information than the legacy GPS in poor signal conditions. But, These method also have some problems. So, hybrid timing method like A-GPS+PTP and TV+GPS was developed to make up the weak point of GPS. This paper introduces the each method and compare each other and y propose much better solution for timing synchronization at the Femtocell

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.141-144
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• 2005

Contents of this paper strengthen security of data by applying encryption algorithm to use cellular phone and settlement by Mobile that is used synchronization method and quotes and prevent damage of bar-code peculation etc.. If divide system step by step to execute this, step that create Mobile bar-code and transmits by individual terminal after encryption, step displaying to individual Mobile terminal, step that above individual Mobile terminal and main server form assimilation and these are consisted of step that quote confirming above information confirmation and motive availability. For the actual example, confirm effectiveness of certification system through simulation.

• Journal of Digital Contents Society
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• v.8 no.1
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• pp.17-25
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• 2007

Recently, the ubiquitous computing environment being able to connect all kinds of computing elements at anytime anywhere becomes widespread in human life. In this paper, we focus on a PC remote control system using cellular phones. Especially, we design and implement an mobile e-mail transmission system using PC remote control technique. By using our remote controller, cellular phone users can login into their own PC, and then send any file to others by e-mail attachment. To show the correct running of our system, real demonstration results are presented. We are sure that by opening our source code to the public our results can play an important role to encourage development of the various mobile remote control functionalities.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.29 no.4
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• pp.100-106
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• 2006

We analyze a voice/data integrated traffic model of the cellular mobile communication system with hybrid guard channels for voice and handoff calls. In a multi-service integrated wireless environment, quality of service guarantee is crucial for smooth transportation of real time information. Real time voice traffic requires a guaranteed upper bounded on both delay and packet error rate, whereas data traffic does not. Voice traffic has high transmission priority over data packets. Thus one of the important problems is the design of admission control schemes which can efficiently accommodate the differential quality of service requirements. In this paper, a hybrid guard channel scheme is considered in which arriving calls are assigned channels as long as the number of busy channels in the cell is below a predetermined first threshold. When the number of busy channels reaches the first threshold, new originating data calls are queued in the infinite data buffer. Then reaches second threshold, only handoff calls are assigned the remaining channels and new originating voice calls are blocked. We evaluate the system by a two-dimensional Markov chain approach and generating function method and obtain performance measures included blocking probability and forced termination probability.

• Proceedings of the Korean Society for Quality Management Conference
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• 2010.04a
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• pp.151-156
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• 2010

As well as the development of the measurement of service quality, various kinds of service measurements are also being developed. Especially the mobile telecommunication service being representative to the mobile telecommunication company would be the mostly developed area. Its development can be understood along with the development of the telecommumication companies as well as cellular companies, not only the service alone. It is a differentiated phenomenon in the current research, such as the organic influence between the service quality and product. Of course there are such products placed on sale and enjoyed the common service, but at present there is another case that the product is on the market exclusively with the mobile company in here.

• Journal of Communications and Networks
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• v.2 no.1
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• pp.18-34
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• 2000

The evolution of mobile communications is inducting several new issues belonging to the system engineering disciplines. this paper tires to underline some of the most important problems staring room the novel requirements and the application characteristics expected for Third Generation Mobile System. Based on these new service peculiarities. the radio resource control and the architectural solutions to be chosen for the Mobile core network are becoming key issues to be investigated for the forthcoming configurations. Particularly. the service acceptance control and the perspective of integration with the IP (internet Protocol) context are of great importance for the definition of the radio control functions and the specification of the switching and nobility control features respectively．The paper presents some basic considerations on the cellular planning issues arising in W-CDMA ( wideband -code division Multiple access) systems. by underlying the most significant innovative elements that are to be introduced in the planning process form the mobile operator viewpoint..

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2093-2095
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• 2002

Nowadays, there are actually lots of changes in wireless communications of Korea. But it is not an exact PTP(Peer to Peer) Communication. In other words, a mobile station which can find fixed station can be connected with wireless internet server or other services, oppositely fixed station cannot approach to mobile station. Even though it exists, it is difficult to communicate with full duplex. We can service using CDMA 1X techniques such as cellular based SMS (Short Message Service) service or very simple MPRG Services. In this paper, we propose a system, using DirectX based mobile/fixed station stand alone program, depending on bandwidth of wireless service provider, tranceiving high resolution moving picture or reliable data regularly by a fixed connection each other.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.661-667
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• 2001

This paper proposes a Truncated Type-II Hybrid ARQ scheme using an adaptive modulation system to achieve high throughput data transmission systems for DS-CDMA cellular mobile communication systems. In this paper, the adaptive modulation system analyzed in Nakagami (m-distribution) fading channel environment. The adaptive modulation system controls the modulation level and symbol rate according to the Nakagami fading parameter( m). When the received Eb/No is high or the Nakagami fading parameter m is high, the propose system selects higher modulation level and higher symbol rate to increase throughput. On the other hand, this system selects lower modulation level and lower symbol rate to prevent throughput performance degradation when the received Eb/No is low. The modulation method have been adopted QPSK 16QAM, 64QAM, 256QAM. Therefore, adaptive modulation systems with Truncated Type II Hybrid ARQ Scheme is proper for mobile and radio data communication system that require high reliability and delay-limited applications.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.10
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• pp.86-94
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• 1993

This paper presents the two-stage neural network method for efficient channel assignment of cellular mobile radio network. The first stage decomposes the region into non-adjacent groups of cells and the second stage assigns channels to the decomposed groups. The neural network model is tested with an experimental system of eighteen channels dedicated for nineteen hexagonal-cell region. When radom call requests of average density of 2 Erl/Cell to 8 Erl/Cell are presented, the real-time channel assignment method reduces the call-blocking rate up to 16% against the existing SCA(Static Channel Assignment) method.

• Journal of the Korean Operations Research and Management Science Society
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• v.25 no.1
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• pp.85-92
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• 2000

Channel management is critical in designing a cellular mobile system that offers high capacity and high quality. In this paper, an integrated channel management scheme is proposed, which consists of a dynamic channel allocation scheme and an admission control scheme. The dynamic channel allocation scheme allocates a call request the channel which minimizes the impact on its interfering cell, and consists of two types of channel allocation strategies : nominal channel allocation strategy and non-nominal channel allocation strategy. The admission control scheme named the variable cutoff priority scheme reserves some frequency channels for handoff cells in each cell the number of which varies according to the blocking probability of handoff class in that cell. Computationl tests are performed to evaluate the performance of the proposed scheme in terms of overall blocking probability, defined by the weighted value of the blocking probabilities of new calls and handoff calls. The results show that the proposed scheme yields better performance than other compared schemes.