• 제어로봇시스템학회논문지
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• 제3권1호
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• pp.77-88
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• 1997

Fieldbus is the lowest level communication network in factory automation and process control systems. Performance of factory automation and process control systems is directly affected by the data delay induced by network traffic. Data generated from several distributed field devices can be largely divided into three categories: sporadic real-time, periodic real-time and non real-time data. Since these data share one fieldbus network medium, the limited bandwidth of a fieldbus network must be appropriately allocated to the sporadic real-time, periodic real-time and non real-time traffic. This paper introduces a new fieldbus design scheme which allocates the limited bandwidth of fieldbus network to several different kinds of traffic. The design scheme introduced in this study not only satisfies the performance requirements of application systems interconnected into the fieldbus but also fully utilizes the network resources. The design scheme introduced in this study can be applicable to cyclic service protocols operated under single-service discipline. The bandwidth allocation scheme introduced in this study is verified using a discrete-event/continuous-time simulation experiment.

• 방송공학회논문지
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• 제23권6호
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• pp.813-823
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• 2018

끊김 없는 UHD 콘텐츠 스트리밍 서비스를 제공하기 위해서는 많은 가용 대역폭이 필요하다. 기존의 HTTP 적응적 스트리밍 방식은 정상 상태에서 가용 대역폭보다 낮은 품질의 비디오 세그먼트를 주기적으로 요청하여 다운로드 받는다. 정상 상태에서는 가용 대역폭과 콘텐츠의 인코딩 율에 차이에 따라 On-Off 구간의 패턴이 반복되어 발생하고, 반복적인 Off 구간에 의해서 대역폭을 효율적으로 사용하지 못하는 문제점이 있다. 지연과 손실률이 높고 대역폭 변화가 심한 무선 환경에서는 네트워크의 가용대역폭을 부정확하게 측정하기 때문에 문제점이 심화된다. 본 논문에서는 무선 환경에서 UHD 콘텐츠의 효율적인 대역폭 활용을 위한 HTTP 적응적 스트리밍의 세그먼트 스케줄링 기법을 제안한다. 제안하는 기법은 OFF 구간의 빈도수를 줄이기 위해 한 번의 요청 메시지에 여러 세그먼트를 동시에 요청하는 집단 세그먼트 방식이다. 실험을 통해서 제안하는 기법이 대역폭 이용율을 향상시키는 것을 확인 하였다.

• International Journal of Internet, Broadcasting and Communication
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• 제12권4호
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• pp.166-172
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• 2020

Video streaming application such as YouTube is one of the most popular mobile applications. To adjust the quality of video for available network bandwidth, a streaming server provides multiple representations of video of which bit rate has different bandwidth requirements. A streaming client utilizes an adaptive bit rate scheme to select a proper video representation that the network can support. The download behavior of video streaming client player is governed by several parameters such as maximum buffer size. Especially, the size of the maximum playback buffer in the client player can greatly affect the user experience. To tackle this problem, in this paper, we propose the maximum buffer size optimization according to available network bandwidth and buffer status. Our simulation study shows that our proposed buffer size optimization scheme successfully mitigates playback stalls while preserving the similar quality of streaming video compared to existing ABR schemes.

• Journal of electromagnetic engineering and science
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• 제8권2호
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• pp.41-46
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• 2008

A bandwidth and power efficient high speed ubiquitous sensor network(USN) for realizing a ubiquitous society is a great challenge for researcher community. In this paper we incorporate a cooperative transmission protocol within a special type of multi-code modulation to meet these requirements. Multi-code(Mc) modulation has been developed for high-speed data transmission over wireless channels. We proposed a new class of orthogonal codes for multi-code modulation which is an orthogonal subset of orthogonal codes(OSOC). Our proposed OSOC structure allows us to use only one relay to cooperate M nodes that effectively reduces the bandwidth and power requirement. This protocol is similar to spread-spectrum(SS) technique that can reduce both broad and narrow band jamming.

• Journal of Information Processing Systems
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• 제4권2호
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• pp.41-52
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• 2008

In this paper, we discuss a novel reservation-based, asynchronous MAC protocol called 'Multi-rate Multi-hop MAC Protocol' (MMMP) for multi-hop ad hoc networks that provides QoS guarantees for multimedia traffic. MMMP achieves this by providing service differentiation for multirate real-time traffic (both constant and variable bit rate traffic) and guaranteeing a bounded end-to-end delay for the same while still catering to the throughput requirements of non real time traffic. In addition, it administers bandwidth preservation via a feature called 'Smart Drop' and implements efficient bandwidth usage through a mechanism called 'Release Bandwidth'. Simulation results on the QualNet simulator indicate that MMMP outperforms IEEE 802.11 on all performance metrics and can efficiently handle a large range of traffic intensity. It also outperforms other similar state-of-the-art MAC protocols.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2010년도 추계학술발표대회
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• pp.1482-1484
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• 2010

A new TCP protocol can succeed for large bandwidth delay product when it meets network bandwidth utilization efficiency and fair sharing. We introduce a novel congestion control algorithm which employs queueing delay information in order to calculate the amount of congestion window increment in increase phase, and reduces congestion window to optimal estimated bound as packet loss occurs. Combination of such methods guarantees that the proposal utilizes fully network bandwidth, recovers quickly from packet loss in wireless link, and preserves fairness for competing flows mixed short RTT and long RTT. Our simulations show that features of the proposed TCP meet the desired requirements.

• 한국정보처리학회논문지
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• 제4권6호
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• pp.1433-1442
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• 1997

멀티미디어 서비스를 위한 ATM 망에서 다양한 트래픽 클래스의 Qos 요구를 만족하기 위한 최적화된 대역폭의 알고리즘 설계가 필요하다. ATM망은 다양한 트래픽 성질 즉, 버스트 비트율과 버스트 길이로 분류되는 트래픽의 Qos 요구를 보장하여야 한다. QoS는 셀손실 가능성과 최대 셀 대기에 의하여 측정되는데, 본 논문에서는 가상경로에서 MMDP 방법을 적용하여 On-Off 자원의 다중 클래스가 하나의 가상경로 망에서 다중 송신할 때 모든 QoS 필요성을 만족하게 요구하는 최소 용량을 계산한다. 위 결과를 이용해서 개별적인 QoS를 요구하는 총 용량에서 가장 최적에 이르는 가상경로를 결정하는 알고리즘을 제안한다. 동일하게 다중 전송되는 트래픽 클래스가 최대 대역폭 효율에 따라 요구되는 최적의 용량과 비교하여 제안된 알고리즘 성능이 우수함을 증명한다.

• 한국통신학회논문지
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• 제29권1B호
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• pp.64-72
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• 2004

Multiprotocol Label Switching (MPLS) has been developed as a key technology to enhance the reliability, manageability and overall quality of service of core If networks with connection-oriented tunnel LSP and traffic engineering such as constraint-based routing, explicit routing, and restoration. In this paper, we propose a control bandwidth borrowing scheme that maximizes the utilization of tunnel LSPs or physical links by an extension to the RSVP-TE label distribution protocol. MPLS-based core switching network and VPN services rely on the establishment of connection-oriented tunneled LSPs that are configured or predefined by network management systems. The mechanism of network management system varies from (i) a relatively static LSP establishment accounting, to (ii) a dynamic QoS routing mechanisms. With the use of hierarchical LSPs, the extra bandwidth that is unused by the trunk (outer) LSPs should be fully allocated to their constituent end-to-end user traffic (inner) LSPs in order to maximize their utilization. In order to find out the unused extra bandwidth in tunnel LSP or physical link and redistribute these resources to constituent LSPs, we expend the functionality of RSVP-TE and the found unused extra bandwidth is redistributed with a weight-based recursive redistribution scheme. By the extended RSVP-TE and proposed recursive redistributed scheme, we could achieve the instantaneous maximized utilization of tunnel LSP or physical link suffering from the potential under-utilization problem and guarantee the end-to-end QoS requirements. With the proposed scheme, network manager can manage more effectively the extra available bandwidth of hierarchical LSPs and maximize the instantaneous utilization of the tunneled LSP resources.

• 한국정보통신학회논문지
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• 제6권2호
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• pp.228-235
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• 2002

차별 서비스 네트워크는 유사한 서비스 품질에 대한 요구조건을 갖는 연결 집합에 대해 동일한 서비스를 제공한다. 트래픽 조절 메커니즘은 차별 서비스 네트워크를 실현시키는 핵심 기능 중의 하나이다. 본 논문은 예약 대역폭의 크기에 따른 처리율의 편향성을 완화시키는 트래픽 조절 메커니즘을 제안한다. 시뮬레이션 방법에 의한 분석을 통해, 제안된 메커니즘은 적절히 배치되거나 과잉 배치된 네트워크 상황에서도 예약 전송률의 크기에 따른 민감성을 완화시켰고, 모든 소스가 예약 대역폭을 달성하고, 초과되는 대역폭에 대해 비교적 공평 히 분배하는 것으로 나타났다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 1998년도 추계종합학술대회
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• pp.408-413
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• 1998

Electromagnetic wave absorbers for anechoic chamber are needed to broaden the useful frequency bandwidth, reduce the thickness, and decrease the weight. There are various absorbers proposed for the above conditions, but they could not decisively solve it the alone requirements. The Electromagnetic wave absorber made by a conventional ferrite tile has, for example, broadened the useful frequency bandwidth by the way of forming air layer(practically use urethane foam, etc.) on the ferrite tile. Therefore, an air layer is formed between a reflection plate and a sintered Ni-Zn ferrite tile of 7 mm in thickness, which has reflectivity less than -20 dB from 30 MHz to 600 MHz in bandwidth. Accordingly, in this paper, a broadened electromagnetic wave absorber will be designed, which has the reflection characteristics less than -20 dB from 30 MHz to 6000 MHz in the bandwidth. Then we will design a super broadband electromagnetic wave absorber by inserting square Ferrite Cylinders Type with the thickness less than 11 m and with the frequency band from 30 MHz to 6000 MHz under the above tolerance limits. The purpose of this research is on the development of a universal anechoic chamber for measuring radiated electromagnetic wave or immunity of electronic equipments, GTEM-cell, wall material for prevention TV ghost, etc.