• 정보화사회
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• s.129
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• pp.42-49
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• 1999

디지털 비디오의 혁명이 가시화 되면서 가정의 각 Consumer기기들 간의 고속 Digital Interface가 요구되어져 왔다. 이러한 요구의 예는 MPEG-2 Transport Stream을 이용한 Set-Top Bx, Digital Television, DVCR 또는 Camcorder간의 Interface와 Interactive Games, Computers 및 주변기기간의 Control/Data Interface를 포함하고 있다. 엄밀히 말해 Data의 일반적인 전송을 지원하는 Interface가 요구되어지며, IEEE1394 Standard는 이에 대한 최적의 Solution을 제공해 준다. 본 기술은 IEEE1394를 기반으로 MPEG-2 Transport Stream을 주고받을 수 있는 방법을 제공하기 위한 Hardware를 개발하는 기술인 MPEG2용 IEEE1394 Link Chip Set 개발 기술에 대하여 설명한다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.5
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• pp.91-99
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• 2019

Existing node-to-node based optimal path searching is built on the assumption that all destination nodes can be arrived at from an origin node. However, the recent appearance of the adaptive path search algorithm has meant that the optimal path solution cannot be derived in node-to-node path search. In order to reflect transportation data at the links in real-time, the necessity of the node-to-link (or link-to-node; NL) problem is being recognized. This research assumes existence of a network with link-label and non-additive path costs as a solution to the node-to-link optimal path problem. At the intersections in which the link-label has a turn penalty, the network retains its shape. Non-additive path cost requires that M-similar paths be enumerated so that the ideal path can be ascertained. In this, the research proposes direction deletion and turn restriction so that regulation of the loop in the link-label entry-link-based network transformation method will ensure that an optimal solution is derived up until the final link. Using this method on a case study shows that the proposed method derives the optimal solution through learning. The research concludes by bringing to light the necessity of verification in large-scale networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.868-878
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• 2004

In this paper, we analyse feasibility of Zone-based Power Control (ZPC) scheme introduced for CDMA forward link(1) in the reverse link. To operate ZPC scheme in the CDMA systems the maximum power level that can be allocated to each traffic channel should be determined. Because all the service channels share the whole power resource in the forward lint a specific mechanism that determines Maximum power resource to each traffic channel is required to operate ZPC scheme in the forward link. However, ZPC scheme can be easily adopted to the reverse link, because of the fact that the whole power resource of service terminal is only confined to its traffic channel. In other words, we need not to determine the maximum power resource to be allocated in the reverse traffic channel. Simulation results show that ZPC scheme adopted to the reverse link yields a significant performance improvement compared with the conventional TPC(IS-95 TPC) scheme in terms of the power consumption and the traffic capacity of Portables, especially with the increasing number of high-rate data traffics. With the proposed scheme, not only be extended the service coverage of high-rate data traffic to the entire cell service coverage, but also the QoS of low-rate traffic can keep going through the service time, especially, in the situation that the incoming interference is much larger.

• Journal of Astronomy and Space Sciences
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• v.28 no.4
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• pp.299-304
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• 2011

As more satellites are designed to downlink their observed image data through the X-band frequency band, it is inevitable that the occupied bandwidth of a target satellite will overlap with that of other X-band downlink satellites. For sun-synchronized low earth orbit satellites, in particular, it can be expected that two or more satellites be placed within the looking angle of a ground station antenna at the same time. Due to the overlapping in the frequency band, signals transmitted from the adjacent satellites act as interferers, leading to degraded link performance between target satellite and ground station. In this paper, link analysis was initiated by modeling the radiation pattern of ground station antenna through a validated Jet Propulsion Laboratory peak envelope model. From the relative antenna gain depending on the offset angle from center axis of maximum antenna directivity, the ratio of received interference signal level to the target signal level was calculated. As a result, it was found that the degradation increased when the offset angle was within the first point of radiation pattern. For a 7.3 m antenna, serious link degradation began at an offset angle of 0.4 degrees. From this analysis, the link performance of the coming satellite passes can be recognized, which is helpful to establish an operating procedure that will prevent the ground station from receiving corrupted image data in the event of a degraded link.

• Journal of KIISE:Information Networking
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• v.36 no.5
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• pp.456-469
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• 2009

We develop a new wireless link quality metric, ECOT(Estimated Channel Occupancy Time) that enables a high throughput route setup in wireless mesh networks. The key feature of ECOT is to be applicable to diverse mesh network environments where IEEE 802.11 MAC (Medium Access Control) variants are used. We take into account the exact operational features of 802.11 MAC protocols, such as 802.11 DCF(Distributed Coordination Function), 802.11e EDCA(Enhanced Distributed Channel Access) with BACK (Block Acknowledgement), and 802.11n A-MPDU(Aggregate MAC Protocol Data Unit), and derive the integrated link metric based on which a high throughput end-to-end path is established. Through extensive simulation in random-topology settings, we evaluate the performance of proposed link metric and present that ECOT shows 8.5 to 354.4% throughput gain over existing link metrics.

• Journal of Aerospace System Engineering
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• v.6 no.4
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• pp.34-39
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• 2012

CubeSats classified as pico-class satellite require a ground station to track the satellite, transmit a command, and receive an on-orbit data such as SOH (State-of-Health) and mission data according to the operation plan. For this, ground station system has to be properly designed to perform a communication to with the satellite with enough up- and down-link budgets. In this study, a conceptual design of the ground station has been performed for the CubeSat named as STEP Cube Lab. (Cube Laboratory for Space Technology Experimental Project). The paper includes a ground station hardware interface design, link budget analysis and a ground station software realization. In addition, the operation plan of the ground station has been established considering the STEP Cube Lab. mission requirements.

• Journal of Astronomy and Space Sciences
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• v.27 no.1
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• pp.11-20
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• 2010

This paper designs a data link between a Lunar Orbiter (LO) and an Earth Station (ES), and analyzes the downlink performance of a space communications system for lunar exploration, conforming to the recommendations by the Consultative Committee for Space Data Systems (CCSDS). The results provided in the paper can be useful references for the design of reliable communication link for the Korean lunar exploration in the near future.

• Journal of Information Technology Applications and Management
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• v.23 no.2
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• pp.61-80
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• 2016

The wireless mesh network (WMN) is a next-generation technology for data networking that has the advantage in cost and the flexibility in its construction because of not requiring the infra-structure such as the ethernet. This paper focuses on the optimal link scheduling problem under the wireless mesh network to effectuate real-time streaming by using the constraint programming. In particular, Under the limitation of half-duplex transmission in wireless nodes, this paper proposes a solution method to minimize the makespan in scheduling packet transmission from wireless nodes to the gateway in a WMN with no packet transmission conflicts due to the half-duplex transmission. It discusses the conflicts in packet transmission and deduces the condition of feasible schedules, which defines the model for the constraint programming. Finally it comparatively shows and discusses the results using two constraint programming solvers, Gecode and the IBM ILOG CP solver.

• Journal of Korean Institute of Industrial Engineers
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• v.31 no.3
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• pp.219-227
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• 2005

In this paper, an optimal power and rate allocation model is mathematically formulated on the forward link of multicell CDMA mobile systems. The model maximizes total utility considering data rates and fairness among cells under delay and PRER (Post RPL Error Rate) constraints. The two-level power and rate allocation scheme is suggested to solve the proposed model. Experimental results show that the proposed scheme provides a good solution in a fast time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9B
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• pp.771-777
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• 2004

In a COMA system, the capacity is variable and mainly depends on multiple access interference. The multiple access interference has a deep relationship with transmitted or received power. The capacity of COMA2000 system is considered to be limited by the forward link capacity. In this paper, we show that the forward link cell load can be represented by the total transmitted power of base station and we propose a forward link call admission control (CAC) strategy for COMA2000 system. The proposed call admission scheme adopts the rate control algorithm for data call. This call admission scheme enables the system to utilize radio resource dynamically by controlling data rate according to the cell load status, and enhance the system throughput and grade of service (GoS). quality of service(QoS) such as blocking and outage probability.