• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권3호
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• pp.1599-1610
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• 2019

Intelligent services have expanded as Internet of Things (IoT) technology has evolved and new requirements emerge to accommodate various services. One new requirement is transmitting data over long distances with low-power. Researchers have developed low power wide area (LPWA) network technology to satisfy the requirement; this can improve IoT network infrastructure and increase the range of services. However, network coverage expansion causes several problems. The traffic load is concentrated at a specific gateway, which causes network congestion and leads to decreased transmission efficiency. Therefore, the approach proposed in this paper attempts to recognize and then avoid congestion through gateway channel hopping. The LPWA network employs multiple channels, so wireless channel hopping is available in a gateway. Devices that are not delay sensitive wait for the gateway to reappear on their wireless channel; delay sensitive devices change the wireless channel along the hopping gateway. Thus, the traffic load and congestion in each wireless channel can be reduced improving transmission efficiency. The proposed approach's performance is evaluated by computer simulation and verified in terms of transmission efficiency.

• Journal of Information Processing Systems
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• 제13권6호
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• pp.1544-1553
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• 2017

The network coding mechanism has attracted much attention because of its advantage of enhanced network throughput which is a desirable characteristic especially in a multi-hop wireless network with limited link capacity such as the device-to-device (D2D) communication network of 5G. COPE proposes to use the XOR-based network coding in the two-hop wireless network topology. For multi-hop wireless networks, the Distributed Coding-Aware Routing (DCAR) mechanism was proposed, in which the coding conditions for two flows intersecting at an intermediate node are defined and the routing metric to improve the coding opportunity by preferring those routes with longer queues is designed. Because the routes with longer queues may increase the delay, DCAR is inefficient in delivering real-time multimedia traffic flows. In this paper, we propose a network coding-aware routing protocol for multi-hop wireless networks that enhances DCAR by considering traffic load distribution and link quality. From this, we can achieve higher network throughput and lower end-to-end delay at the same time for the proper delivery of time-sensitive data flow. The Qualnet-based simulation results show that our proposed scheme outperforms DCAR in terms of throughput and delay.

• ETRI Journal
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• 제44권6호
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• pp.1020-1033
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• 2022

In this paper, we propose novel disaggregated memory module (dMM) architecture and memory access control schemes to solve the collision and contention problems of memory disaggregation, reducing the average memory access time to less than 1 ㎲. In the schemes, the distributed scheduler in each dMM determines the order of memory read/write access based on delay-sensitive priority requests in the disaggregated memory access frame (dMAF). We used the memory-intensive first (MIF) algorithm and priority-based MIF (p-MIF) algorithm that prioritize delay-sensitive and/or memory-intensive (MI) traffic over CPU-intensive (CI) traffic. We evaluated the performance of the proposed schemes through simulation using OPNET and hardware implementation. Our results showed that when the offered load was below 0.7 and the payload of dMAF was 256 bytes, the average round trip time (RTT) was the lowest, ~0.676 ㎲. The dMM scheduling algorithms, MIF and p-MIF, achieved delay less than 1 ㎲ for all MI traffic with less than 10% of transmission overhead.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권8호
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• pp.3551-3567
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• 2016

The Low Earth Orbit satellite network has the unique characteristics of the non-uniform and time-variant traffic load distribution, which often causes severe link congestion and thus results in poor performance for delay-sensitive flows, especially when the network is heavily loaded. To solve this problem, a novel adaptive routing algorithm, referred to as the delay-oriented adaptive routing algorithm (DOAR), is proposed. Different from current reactive schemes, DOAR employs Destination-Sequenced Distance-Vector (DSDV) routing algorithm, which is a proactive scheme. DSDV is extended to a multipath QoS version to generate alternative routes in active with real-time delay metric, which leads to two significant advantages. First, the flows can be timely and accurately detected for route adjustment. Second, it enables fast, flexible, and optimized QoS matching between the alternative routes and adjustment requiring flows and meanwhile avoids delay growth caused by increased hop number and diffused congestion range. In addition, a retrospective route adjustment requesting scheme is designed in DOAR to enlarge the alternative routes set in the severe congestion state in a large area. Simulation result suggests that DOAR performs better than typical adaptive routing algorithms in terms of the throughput and the delay in a variety of traffic intensity.

• 전자공학회논문지CI
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• 제41권4호
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• pp.73-83
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• 2004

제한된 도로에서 증가되는 차량으로 인해서, 평균주행속도가 떨어지고 교차로의 대기 손실이 많아지고 있다. 본 논문은 10개 교차로를 연동 제어를 할 수 있는 새로운 교통체제 개념을 제안한다. 예를 들어서 오늘 야구경기가 8시경에 열린다고 하면 야구경기가 시작하기 전 1시간 혹은 1시간 30분전에 교통량이 증가할 것이다. 이럴 때에는 아무리 우수한 전자 신호등 시스템도 최적녹색시간을 예측할 수 없다. 그러므로 본 논문에서는 평균 승용차 대기시간을 최소화하고 평균 주행속도를 향상하기 위해서 전처리로써 퍼지규칙 및 신경망을 이용한다. 또한 후처리로써 예기치 못한 상황을 지능적으로 제어할 수 있는 지능적인 소프트웨어 PLC(Programmable Logic Controller)를 구현하였다. 시뮬레이션결과 제안된 연동 녹색시간이 연동 녹색시간을 고려하지 않은 전자신호등보다 평균 승용차 대기시간을 줄일 수 있음을 입증했다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.281-284
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• 2001

In this paper, we design the Sorting-Banyan network with an efficient buffer and sorting management schema that makes switch be capable of supporting delay sensitive as well as loss sensitive. The proposed switching network is remodeled that based on Batcher-banyan network that have eight input and output ports The structure of designed switching network is constructed of modified banyan network with 2-way routing paths and two plane sorting networks. we have analysed the maximum throughput of the switch, under the uniform random traffic load, the FIFO discipline has increased by about 11% when we compare the switching system with the input buffering system.

• Journal of applied mathematics & informatics
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• 제5권3호
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• pp.643-658
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• 1998

In this paper we analyze the performance of a statistical ATM multiplexer with bursty input traffic and two thresholds in the buffer by using queueing model. Two priority levels are considered for source traffic which is modeled by Markov Modulated Poisson Process to represent the bursty characteristics. Service time distributions of two priority sources are assumed to be same and deterministic for ATM environment. The partial buffer sharing scheme with one threshold may experience a sensitive state change around the threshold. But the proposed multiplexer with two thresholds avoids this hysterical phenominon to improve the system operation.

• ETRI Journal
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• 제29권5호
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• pp.685-687
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• 2007

In this letter, we propose a new online buffer management algorithm to simultaneously provide diverse multimedia traffic services and enhance network performance. Our online approach exhibits dynamic adaptability and responsiveness to the current traffic conditions in multimedia networks. This approach can provide high buffer utilization and thereby improve packet loss performance at the time of congestion.

• 대한전자공학회논문지TC
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• 제39권12호
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• pp.539-546
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• 2002

본 논문에서의 패킷 스케줄러는 무선 채널 환경에서 실시간 비디오 트래픽과 비실시간 인터넷 트래픽을 동시에 서비스한다. 그리고 실시간 트래픽에 대한 지연을 감소 시기키 위하여 누적카운터와 SIR값을 동시에 고려하는 새로운 패킷 스케줄링 알고리즘을 제안한다. 본 알고리즘에서는 실시간 트래픽을 비실시간 트래픽에 비하여 우선적으로 처리한다. 시뮬레이션 결과를 고찰할 때, 실시간 비디오 트래픽과 같이 지연성능에 민감한 서비스의 경우에는 AC(Accumulation Counter) 방식이 기존의 M-LWDF방식보다 더 적합한 알고리즘으로 관찰되었다. 본 논문에서는 HSDPA 시스템과 유사한 구조를 채택하여 시간 축으로는 프레임 주기를 가지며 동시에 코드 축으로는 OVSF 코드를 사용할 수 있는 구조를 채택하여 모의 실험을 수행하였다.

• 한국컴퓨터산업학회논문지
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• 제5권9호
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• pp.1005-1016
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• 2004

기존 교통신호등은 최적 교통신호주기기능을 상실했다. 기존 교통신호주기는 현시 교통주기와 30% -45% 가 일치하지 않고 있다. 본 논문에서는 평균 주행속도를 개선하고 평균 승용차 대기시간을 단축하기위해서 전자 교통신호등을 본 논문에서 제안한다. 본 논문에서는 실제 교통상황의 교통량, 출발 지연시간, 자동차속도 등의 40가지 센서 입력조건들을 저장하는 방법을 연구 중이다. 지능형 퍼지 기법을 이용하면, 서로 다른 10개의 교차로에 서 최 적의 녹색시간을 예측할 수 있다. 컴퓨터 모의실험 결과, 자동차 길이를 고려하지 않은 기존 교통신호등보다 . 오프셋 및 평균 자동차 대기시간을 줄일 수 있음이 입증되었다.