• IE interfaces
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• v.12 no.1
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• pp.19-25
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• 1999

The time slot scheduling problem for a satellite cluster with an arbitrary number of satellite is considered, which is one of the most interesting problems in the satellite communication scheduling area. This problem is known to be NP-complete, and several heuristic algorithms have been proposed. In this paper, a new efficient algorithm is suggested, which has lower computational complexity and provides much better solution than other existing algorithms.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.753-756
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• 2001

Automatic Identification System(ALS) employed SOTDMA for the multiple access method. In SOTDMA systems, slot reuse may result in discrimination or garbling. Especially Gaussian Minimum Shift Keying(GMSK) Co-Channel Interference(CCI) resulted from the slot reuse in the Aloha zone degrades the system performance such as capacity In this paper we introduce some useful techniques to cancel the CCI and discuss the methodology which is applicable to AIS-SOTDMA

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1653-1658
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• 2009

SoC(System on a Chip) has several masters, slaves, arbiter and decoder in bus architecture. Master initiates the data transactions like CPU, DMA and DSP and slave responses the data transactions like SRAM, SDRAM and register. Furthermore, as multiple masters can't use a bus concurrently, arbiter plays an role in bus arbitration. In compliance with the selection of arbitration method, SoC performance can be changed definitely. In this study, we compare the characteristics of various arbitration policies using TLM(Transaction Level Model) method. Fixed priority, round-robin, TDMA and Lottery bus policies are used in general arbitration method. We analyze the merit and demerit of these arbitration policies.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.744-748
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• 2003

Developing an interactive satellite multi­media system, such as a digital video broadcasting (DVB) return channel via satellite (RCS) system, is gaining popularity over the world To accommodate the increasing traffic demand we are motivated to investigate an alternative for improving return channel utilization We develop an efficient method for optimal packet scheduling in an interactive satellite multimedia system using hybrid CDMA/TDMA channels. We formulate the timeslot-code assignment problem as a binary integer programming (BIP) problem, where the throughput maximization is the objective, and decompose this BIP problem into two sub-problems for the purpose of solution efficiency. With this decomposition, we promote the computational efficiency in finding the optimal solution of the original BIP problem Since 2001, ETRI has been involved in a development project where we have successfully completed an initial system integration test on broadband mobile Internet access via Ku-band channels using the proposed resource allocation algorithm.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.4
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• pp.450-456
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• 2010

In the high-speed packet service, next generation mobile communication system has emerged as a major feature. If the fire of these high-speed kit services and non-continuous transmission of data due to the symmetrical nature of daeyiteo traffic for D-CDMA system has been actively studied. Small amounts of data moving in the uplink, but the real-time video downlink transmission, such as downloading large files to move data and services to those with asymmetric traffic characteristics, a system that can efficiently handle the data requirements be. Of 3GPP TDD(Time Division Duplex) scheme based on CDMA and TDMA in a way by introducing the concept through the proper allocation of time slots that can handle asymmetric traffic efficiently, has an advantage. TD-CDMA system by considering the characteristics of the frame configuration of transmission methods, such as physical channel structure and channel coding has been investigated. In addition, the HARQ scheme TD-CDMA system performance is analyzed by comparing them.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2002.11a
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• pp.303-306
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• 2002

본 논문에서는 ATM(Asynchronous Transfer Mode) 기반의 Ka 대역 초고속 위성 TDMA(Time Division Multiple Access) 지구국 시스템인 HiSTARS (High-Speed Satellite TDMA Ground System )시스템에서 망 전체의 형상 및 자원 정보를 관리하며, 장애상태 및 사용 채널에 대한 과금 정보를 관리하며, 장애와 망 전체에서의 망 운용성능과 관련된 통계 정보를 운용자에게 알려주는 망운용관리시스템(Network Management System)을 소개한다. NMS는 운용자의 요구사항을 HiSTARS 시스템의 기준지구국에 위치한 중앙처리시스템과의 빠르고, 정확한 메시지 통신을 통해 즉각적으로 처리하며, 모듈별로 독립적으로 기능들이 구현되어 있으며. 이들 모듈간의 원활한 통신 및 데이터베이스를 통한 데이터 관리를 통해 HiSTARS 시스템의 망 전체를 효과적으로 관리하고 운용할 수 있도록 한다. 본 논문에서는 이러한 NMS의 디자인 및 구현 방법을 구체적으로 보이겠다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.7
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• pp.303-312
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• 2006

This paper proposes the architecture and protocol of a data communication network for the safety system in nuclear power plants. First, we establish four design criteria with respect to determinability, reliability, separation and isolation, and verification/validation. Next we construct the architecture of the safety network for the following systems: PPS (Plant Protection System), ESF-CCS (Engineered Safety Features-Component Control System) and CPCS (Core Protection Calculator System). The safety network consists of 12 sub-networks and takes the form of a hierarchical star. Among 163 communication nodes are about 1600 origin-destination (OD) pairs created on their traffic demands. The OD pairs are allowed to exchange data only during the pre-assigned time slots. Finally, the communication protocol is designed in consideration of design factors for the safety network. The design factors include a network topology of star, fiber-optic transmission media, synchronous data transfer mode, point-to-point link configuration, and a periodic transmission schedule etc. The resulting protocol is the modification of IEEE 802.15.4 (LR-WPAN) MAC combined with IEEE 802.3 (Fast Ethernet) PHY. The MAC layer of IEEE 802.15.4 is simplified by eliminating some unnecessary (unctions. Most importantly, the optional TDMA-like scheme called the guaranteed time slot (GTS) is changed to be mandatory to guarantee the periodic data transfer. The proposed protocol is formally specified using the SDL. By performing simulations and validations using Telelogic Tau SDL Suite, we find that the proposed safety protocol fits well with the characteristics and the requirements of the safety system in nuclear power plants.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.555-564
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• 2016

This paper proposes a time slot allocation scheme for military patrol environments. This proposal comes from analysis of traffic properties in a military patrol environment. In the near future, robots are expected to explore enemy grounds and measure threat, taking the place of human patrol. In order to control such robots, control messages must be extremely accurate. One mistake from the control center could cause a tragedy. Thus, high reliability must be guaranteed. Another goal is to maintain a continual flow of multimedia data sent from patrol robots. That is, QoS (Quality of Service) must be guaranteed. In order to transmit data while fulfilling both attributes, the per-path based centralized TDMA slot allocation scheme is recommended. The control center allocates slots to robots allowing synchronization among robots. Slot allocation collisions can also be avoided. The proposed scheme was verified through the ns-3 simulator. The scheme showed a higher packet delivery ratio than the algorithm in comparison. It also performed with shorter delay time in the downlink traffic transmission scenario than the algorithm in comparison.

• The Transactions of the Korea Information Processing Society
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• v.7 no.9
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• pp.2980-2993
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• 2000

In order to achieve the rapid deployment of services. B-ISON network is being combined with terrestrial ATM and satellite network. Cell delay variation (CDV) generated by the difference of transfer mode between TOMA and ATM deteriorates transmission quality of the network system. We proposed the Partial Timestamps algorithm to supplement the problems of existing COV compensation methods. To minimize CDV and to utilize the satellite channels efficiently. only the optimized timestamps of a few cells within a control unit time of TDMA are selected and transmitted to the receiving earth station. The COV compensating efficiency of Partial Timestamps is evaluated by simulation. It is confirmed that CDV compensation capability of the proposed mechanism is superior to the other methods.

• Journal of Environmental Science International
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• v.16 no.7
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• pp.793-798
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• 2007

During May of 2003, smoke from fires in the Yucatan Peninsula was transported across the Gulf of Mexico and into Texas where it caused significant enhancement in measured aerosol concentrations and reduced visibility. During this event, the formation and growth of aerosol particles has been observed by a differential mobility analyzer (DMA) / tandem differential mobility analyzer (TDMA) system to characterize the size distribution and size-resolved hygroscopicity of the aerosol. The most number concentration is by the particles smaller than 100 nm, but the integrated number concentrations for over 100 nm increased due to the aerosol growth. Hygroscopic growth factor increase from 1.2 to 1.4 for 25, 50, and 100 nm particles during the nucleating period. This distribution and the aerosol properties derived from the TDMA data were used to calculate the growth rate. Particle growth rates were in the range 1-12 nm/hr.