• 인터넷정보학회논문지
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• 제18권6호
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• pp.65-73
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• 2017

Congestion occurring at wireless sensor networks(WSNs) causes packet delay and packet drop, which directly affects overall QoS(Quality of Service) parameters of network. Network congestion is critical when important data is to be transmitted through network. Thus, it is significantly important to effectively control the congestion. In this paper, new mechanism to guarantee reliable transmission for the important data is proposed by considering the importance of packet, configuring packet priority and utilizing the settings in routing process. Using this mechanism, network condition can be maintained without congestion in a way of making packet routed through various routes. Additionally, congestion control using packet service time, packet inter-arrival time and buffer utilization enables to reduce packet delay and prevent packet drop. Performance for the proposed mechanism was evaluated by simulation. The simulation results indicate that the proposed mechanism results to reduction of packet delay and produces positive influence in terms of packet loss rate and network lifetime. It implies that the proposed mechanism contributes to maintaining the network condition to be efficient.

• 인터넷정보학회논문지
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• 제5권6호
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• pp.11-20
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• 2004

Proportional Fair (PF) share policy has been adopted as a downlink scheduling scheme in CDMA2000 l×EV-DO standard. Although It offers optimal performance in aggregate throughput conditioned on equal time share among users, it cannot provide a bandwidth guarantee and a strict delay bound. which is essential requirements of real-time (RT) applications. In this study, we propose a new scheduling policy that provides quality-of-service (QoS) guarantees to a variety of traffic types demanding diverse service requirements. In our policy data traffic is categorized Into three classes, depending on sensitivity of Its performance to delay or throughput. And the primary components of our policy, namely, Proportional Fair (PF), Weighted Fair Queuing (WFQ), and delay-based prioritized scheme are intelligently combined to satisfy QoS requirements of each traffic type. In our policy all the traffic categories run on the PF policy as a basis. However the level of emphasis on each of those ingredient policies is changed in an adaptive manner by taking into account the channel conditions and QoS requirements. Such flexibility of our proposed policy leads to offering QoS guarantees effectively and. at the same time, maximizing the throughput. Simulations are used to verify the performance of the proposed scheduling policy. Experimental results show that our proposal can provide guaranteed throughput and maximum delay bound more efficiently compared to other policies.

• 대한전자공학회논문지TC
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• 제47권9호
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• pp.19-28
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• 2010

IEEE 802.15.4 표준에서는 QoS(Quality-of-Service)를 요구하는 응용프로그램들의 패킷 전송을 보장하기 위해 비경쟁 접근방식에 의한 GTS(Guranted Time Solot) 할당 기법을 지원한다. 그러나 표준에 따른 GTS 할당 기법은 패킷이 도착한 순서에 따라 채널을 할당하는 FIFS(First In First Service) 스케쥴링을 사용해 패킷을 처리함으로서 대역의 낭비가 심하고 채널 사용률을 감소시켜 실질적인 QoS 서비스에 적합하지 못하다. 본 논문에서는 이러한 단점을 개선한 공정 큐잉을 위한 GTS 할당 기법을 제안한다. 제안하는 기법은 각 노드의 GTS 할당 요청 횟수(RC, Request Count)와 최근 할당 여부(RA, Recently Allocation)를 이용해 GTS 할당에 대한 불공정성 문제를 해결함으로서 GTS 요청 처리율을 높이고 지연 시간을 감소시킨다. 제안하는 기법의 타당성 및 성능 분석을 위해 수학적 분석 모델을 수립하고, 시뮬레이션을 통해 제안하는 기법이 표준과 비교해 데이터 처리율과 채널 사용률 측면에서 효율적임을 보였다.

• 인터넷정보학회논문지
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• 제12권4호
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• pp.45-50
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• 2011

본 논문에서는 차량용 다중 카메라시스템에서 무선영상을 전송하기 위해 FH/TDD(Frequency Hopping/Time Division Duplex) 기반의 Motion JPEG 영상압축 코덱의 부호화 지연시간을 분석한다. 또한, Motion JPEG기반으로 FH/TDD에 의한 다중접속을 위해 시분할 시에 상호 동기화된 채널이동 과 접근방식(Synchronized shift & access)이 가능하도록 채널의 상태를 파악한 후, 채널충돌(Channel Collision)을 최소화하기 위한 동기화 연결(Synchronized connection) 방식을 설계한다.

• 디지털산업정보학회논문지
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• 제16권2호
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• pp.1-9
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• 2020

Many cryptographic and error control coding algorithms rely on finite field GF(2m) arithmetic. Hardware implementation of these algorithms needs an efficient realization of finite field arithmetic operations. Finite field multiplication is complicated among the basic operations, and it is employed in field exponentiation and division operations. Various algorithms and architectures are proposed in the literature for hardware implementation of finite field multiplication to achieve a reduction in area and delay. In this paper, a low area and delay efficient semi-systolic multiplier over finite fields GF(2m) using the modified Montgomery modular multiplication (MMM) is presented. The least significant bit (LSB)-first multiplication and two-level parallel computing scheme are considered to improve the cell delay, latency, and area-time (AT) complexity. The proposed method has the features of regularity, modularity, and unidirectional data flow and offers a considerable improvement in AT complexity compared with related multipliers. The proposed multiplier can be used as a kernel circuit for exponentiation/division and multiplication.

• 전자공학회논문지A
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• 제33A권11호
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• pp.78-87
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• 1996

in urban cross-roads with dense buildings, receiving power and delay spread were computed when doing these, we were able to develope codes to be executed in a very fast time by combining image method and algorithm for propagation paths compairing with ray launching technique. And receiving power and delay spread could be viewed in 3-dimensional picture by virtue of computing electric fields in arbitrary receiving point. For numerical computation, receiving power of wide and anrrow band and delay spread were computed, and extension method of ray numbers was facilitated for handling infinite number of rays.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.1098-1100
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• 2002

Inter-RNC(radio network controller) and inter-BSC(base station center) hard handovers involve rerouting. Thus additional delay time for the new bearer setup and reroute determination should be considered. For theses kinds of handovers we propose a new scheme and coined it as ICHP(Inter-Cluster Handover Prediction). When a call approaches a boundary cell of a cluster, ICHP prepares for the handover by performing resource reservations and reroute computation in advance. Performance analysis shows that ICHP provides faster handover and that it lowers the blocking probability.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권10호
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• pp.4025-4041
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• 2020

Mobile edge computing (MEC) is capable of providing services to smart devices nearby through radio access networks and thus improving service experience of users. In this paper, an offloading strategy for the joint optimization of computing and communication resources in multi-user and multi-MEC overlapping scene was proposed. In addition, under the condition that wireless transmission resources and MEC computing resources were limited and task completion delay was within the maximum tolerance time, the optimization problem of minimizing energy consumption of all users was created, which was then further divided into two subproblems, i.e. offloading strategy and resource allocation. These two subproblems were then solved by the game theory and Lagrangian function to obtain the optimal task offloading strategy and resource allocation plan, and the Nash equilibrium of user offloading strategy games and convex optimization of resource allocation were proved. The simulation results showed that the proposed algorithm could effectively reduce the energy consumption of users.

• 정보처리학회논문지C
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• 제8C권6호
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• pp.815-820
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• 2001

본 논문은 단말의 이동성을 수용하기 위한 분산 이동 구조에 대하여 다루고 있다. 제안된 구조에서는 세가지 분산 객체에 대하여 소개하고 있는데, 무선 이동 사용자가 이용하는 이동 단말(MS：Mobile Station), 유선망에서 이동 단말을 논리적으로 대신하는 이동 에이전트(MA：Mobile Agent), 이동 단말에 서비스를 제공하는 유선용 응용 서버(AS：Application Server)를 이동 환경에서 수용하기 위한 추적 에이전트(TA：Trace Agent)가 그들이다. 이동 에이전트는 이동 단말과 밀접한 관련을 갖고, 추적 에이전트는 응용 서버와 밀접한 관련을 갖는다. 핸드오프 과정에서 패킷 손실이나 순서 변경과 같은 문제점을 처리하기 위한 흐름 제어 기법이 고려되었으며, 제시된 알고리즘을 사용하는 경우의 추가적인 지연 시간에 대한 산술적인 결과를 제시하고 있다. 시뮬레이션을 통하여 알고리즘의 검증과 함께 산술적인 결과와 동일한 지연 시간을 확인하였다.

• Journal of applied mathematics & informatics
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• 제29권1_2호
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• pp.1-22
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• 2011

In this paper, a Lotka-Volterra model with time delays is considered. A set of sufficient conditions for the existence of Hopf bifurcation are obtained via analyzing the associated characteristic transcendental equation. Some explicit formulae for determining the stability and the direction of the Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations are obtained by applying the normal form method and center manifold theory. Finally, the main results are illustrated by some numerical simulations.