• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2003년도 춘계종합학술대회논문집
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• pp.449-453
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• 2003

In this paper, we evaluate the performance of zone-based registration, distance-based registration and distance-based registration considering call arrival. We propose the mobility model, which can be used to analyze the performance of three registration schemes. Numerical results show that zone-based registration needs less number of registration than distance-based registration. On the other hand, the registration load of the distance-based registration is equally distributed to all cells in a location area. However, the registration load of the distance-based registration considering call arrival is similar to that of zone-based registration and equally distributed to all cells in a location am Therefore, the proposed scheme can be effectively used restricted radio resources.

• Journal of information and communication convergence engineering
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• 제15권1호
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• pp.28-36
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• 2017

The medium access control (MAC) protocol based on dynamic time division multiple access/time division duplex (TDMA/TDD) is responsible for random access control and radio resource allocation in dynamic traffic environments. These functions of random access and resource allocation are very important to prevent wastage of resources and improve MAC performance according to various network conditions. In this paper, we propose new random access and resource allocation schemes to guarantee quality of service (QoS) and provide priority services in a dynamic TDMA/TDD system. First, for the QoS guarantee, we propose an adaptive random access and resource allocation scheme by introducing an access probability. Second, for providing priority service, we propose a priority-based random access and resource allocation scheme by extending the first adaptive scheme in both a centralized and a distributed manner. The analysis and simulation results show that the proposed MAC protocol outperforms the legacy MAC protocol using a simple binary exponential backoff algorithm, and provides good differential performance according to priorities with respect to the throughput and delay.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.261-262
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• 2008

TD-SCDMA is considered as an innovative Chinese 3G technology adopted by the ITU for the IMT-2000 family. TD-SCDMA combines TDMA and CDMA components to provide more efficient use of radio resources. However, the downlink scheduler of TD-SCDMA should transmit data packets with the initial configuration and cannot change the configuration dynamically. Therefore, in this paper, we propose an enhanced channel allocation, by which mobile terminals can share the downlink channelization codes dynamically.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.269-270
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• 2008

TD-SCDMA combines TDMA and CDMA components to provide more efficient use of radio resources, and includes a new feature called HSDPA (high-speed downlink packet access) in the R5 stage. The TD-HSDPA supports high-speed traffic with a shared channel, but the adopted mechanism causes feedback problem for scheduling. In this paper, we propose an improved mechanism that transmits channel quality indicator (CQI) more frequently, so that the TD-HSDPA scheduler can utilize all possible information about the downlink channel status.

• ETRI Journal
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• 제22권1호
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• pp.1-11
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• 2000

The Satellite Operation System (SOS) has been developed for a low earth orbiting remote sensing satellite, Korea Multipurpose Satellite-I, to monitor and control the spacecraft as well as to perform the mission operation. SOS was designed to operate on UNIX in the HP workstations. In the design of SOS, flexibility, reliability, expandability and interoperability were the main objectives. In order to achieve these objectives, a CASE tool, a database management system, consultative committee for space data systems recommendation, and a real-time distributed processing middle-ware have been integrated into the system. A database driven structure was adopted as the baseline architecture for a generic machine-independent, mission specific database. Also a logical address based inter-process communication scheme was introduced for a distributed allocation of the network resources. Specifically, a hotstandby redundancy scheme was highlighted in the design seeking for higher system reliability and uninterrupted service required in a real-time fashion during the satellite passes. Through various tests, SOS had been verified its functional, performance, and inter-face requirements. Design, implementation, and testing of the SOS for KOMPSAT-I is presented in this paper.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.68-86
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• 2015

Future wireless network aims to integrate different radio access networks (RANs) to provide a seamless access and service continuity. In this paper, a new resource denotation method is proposed in the WLAN and LTE heterogeneous networks based on a concept of spectral bandwidth mapping. This method simplifies the denotation of system resources and makes it possible to calculate system residual capacity, upon which an economic model-based network selection algorithm is designed in both under-loaded and over-loaded scenarios in the heterogeneous networks. The simulation results show that this algorithm achieves better performance than the utility function-based access selection (UFAS) method proposed in [12] in increasing system capacity and system revenue, achieving load balancing and reducing the new call blocking probability in the heterogeneous networks.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2005년도 추계 종합학술대회 논문집
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• pp.596-600
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• 2005

In High-speed Portable Internet system to improve performance of whole system, adaptive modulation and coding technology is used, this technology changes modulation and encoding techniques depending on wireless channel environment. Modulation technology that is used in High-speed Portable Internet system is BPSK, QPSK, 16QAMs and 64QAMs. If terminal is distant from base station transceiver system, BPSK or QPSK technology Is used and 16QAMs or 64QAM technology is used if is near in the base station transceiver system. In this paper, number of sub-channel in each modulation technology minimized total transmitting number of PDU is analyzed for efficient radio resources usage. For this, simulation is conducted and the results are presented at High-speed Portable Internet system environments.

• Journal of Communications and Networks
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• 제7권2호
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• pp.222-230
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• 2005

This article presents a field evaluation of an IP-based architecture for heterogeneous environments that has been developed under the aegis of the Moby Dick project, covering UMTS-like (universal mobile telecommunications system) TD-CDMA (time division-code division multiple access) wireless access technology, wireless and wired LANs. The architecture treats all transmission capabilities as basic physical and data-link layers, and replaces all higher-level tasks by IP-based strategies. The Moby Dick architecture incorporates mobile IPv6, fast handovers, AAA-control (authentication, authorisation, accounting), charging and quality of service (QoS) in an integrated framework. The architecture further allows for optimised control on the radio link layer resources. It has been implemented and tested by expert users, and evaluated by real users on field trials with multiple services available.

• 전자통신동향분석
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• 제21권4호통권100호
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• pp.70-79
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• 2006

통신서비스의 확대에 따른 주파수 수요가 점차 증대함에 따라 효율적인 주파수 이용기술에 대한 필요성이 인식되고 있으며, 서비스 확대에 대응할 수 있는 간섭 회피 및 주파수 공유 기술과 관련한 새로운 주파수 이용 기술에 대한 중요성이 증대되고 있다. 이러한 주파수 부족 현상을 기술적인 측면에서 해결하고자 주파수 공유 기술의 개발이 활발히 이루어지고 있다. 또한 이를 뒷바침하기 위해 유연한 주파수 사용이 가능하도록 제도적인 개선이 필요하다. 본 논고에서는 전파자원의 효율적 이용을 위한 스펙트럼 공유 방식과 관련한 기술적 개요를 설명하고 제도적 진행 방향에 대해 논하였다.

• 대한전자공학회논문지TC
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• 제45권2호
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• pp.26-36
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• 2008

현재 우리나라에는 최첨단의 정보통신 서비스를 제공을 목적으로 ubiquitous city(u-City)가 건설 중에 있다. 이들 도시에서 ITS(Intelligent Transportation Systems)는 도시거주민들에게 적절한 교통정보를 제공하는 동시에 최적으로 도시교통을 제어하는 방안이다. ITS의 한 부분으로서 교통흐름에 적합한 교통신호제어가 필요하며 이를 위해 많은 교통정보를 실시간으로 수집하여야 한다. 이러한 교통정보의 수집은 도시운영을 위하여 최첨단 정보통신 서비스가 제공되는 u-City에서는 어렵지 않을 것이다. 이러한 미래지향적인u-City의 ITS 교통제어에 적합한 새로운 시스템에 대하여 이 논문에서는 연구하였다.