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패킷 손실과 순서 어긋남 문제를 해결할 수 있는 새로운 FMIPv6와 HMIPv6 통합 메커니즘
이재훈(Jae-Hwoon Lee),임유진(Yu-Jin Lim) 한국정보과학회 2007 정보과학회논문지 : 정보통신 Vol.34 No.2
Mobile IPv6(MIPv6)는 이동 호스트(mobile node: MN)가 인터넷의 연결 지점을 변경하더라도 임의의 호스트(correspondent node: CN)와 계속 통신을 유지할 수 있도록 하는 기술이다. 기존의 MIPv6 프로토콜에서는 핸드오버 기간 동안 CN이 MN으로 전송하는 트래픽은 손실된다. 이를 방지하기 위하여 HMIPv6 및 FMIPv6와 같은 여러 메커니즘들이 제안되었다. 그렇지만, 이들 메커니즘도 역시 패킷 손실이나 패킷의 순서 어긋남으로 인한 상위 계층의 성능 저하 문제가 발생한다. 본 논문에서는 패킷 손실과 순서 어긋남 문제를 해결할 수 있는 I-FHMIPv6를 제안한다. I-FHMIPv6에서는 홈 에이전트(home agent: HA) 또는 CN에게 MN의 바인딩 캐쉬 엔트리가 갱신된다는 것을 알려주는 Flush 메시지를 새로 정의했다. 이 메시지를 수신한 MN은 이전의 경로를 통한 패킷 전송이 종료된다는 것을 알 수 있으며, 이를 통하여 패킷의 순서 어긋남 문제를 해결할 수 있다. 또한 제안된 알고리즘은 효율적으로 FMIPv6와 HMIPv6를 통합함으로써 패킷 손실을 최소화할 수 있다. 모의실험을 통해 제안된 알고리즘의 성능을 분석하였으며, I-FHMIPv6의 성능이 기존 FMIPv6나 HMIPv6보다 우수함을 알 수 있었다. Mobile IPv6 (MIPv6) enables a mobile node (MN) to maintain its connectivity with a correspondent node (CN) while changing its point of attachment. In MIPv6, packets sent from a CN to a MN during handover are lost. Several mechanisms including FMIPv6 and HMIPv6 have been proposed in order to minimize packet loss. However, such mechanisms still suffer from performance degradation due to not only packet loss but also out-of-sequence packets. In this paper, we propose I-FHMIPv6 to resolve packet loss as well as the out-of-sequence packet problem. In I-FHMIPv6, the flush message is newly defined in order to notify a home agent (HA) or CN of the fact that the binding cache entry of a MN is about to be updated. A MN receiving the flush message can know that there is no more packets transmitted via the previous route, which resolve the out-of-sequence packet problem. Moreover, with the proposed mechanism, we can minimize packet loss by integrating FMIPv6 and HMIPv6 efficiently. I-FHMIPv6 is evaluated by performing simulations, and the simulation results show that I-FHMIPv6 outperforms FMIPv6 and HMIPv6.
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Yun-Bo Zhao,Jongrae Kim,Guo-Ping Liu,David Rees 제어·로봇·시스템학회 2012 International Journal of Control, Automation, and Vol.10 No.5
Data packet disorder is inevitable in discrete-time networked control systems, which however has been ignored in most literature to date. This work investigates the cause and the negative effects of data packet disorder in discrete-time networked control systems, and a compensation scheme is proposed to deal with these negative effects. This analysis shows that most existing works in the related areas have assumed unrealistic characteristics of the communication network and thus further improvements within this new framework are necessary. For this purpose the closed-loop system with the use of the proposed compensation scheme is mathematically modeled as a Markov jump systems, and stochastic stability and stabilization results are then obtained. Numerical examples illustrate the negative effects caused by data packet disorder and also the effectiveness of the proposed approach.
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A Non-Uniform Predictor-Observer for a Networked Control System
Angel Cuenca,Pedro García,Pedro Albertos,Julián Salt 제어·로봇·시스템학회 2011 International Journal of Control, Automation, and Vol.9 No.6
This paper presents a Non-Uniform Predictor-Observer (NUPO) based control approach in order to deal with two of the main problems related to Networked Control Systems (NCS) or Sensor Networks (SN): time-varying delays and packet loss. In addition, if these delays are longer than the sampling period, the packet disordering phenomenon can appear. Due to these issues, a (scarce) non-uniform, delayed measurement signal could be received by the controller. But including the NUPO proposal in the control system, the delay will be compensated by the prediction stage, and the non-available data will be reconstructed by the observer stage. So, a delay-free, uniformly sampled controller design can be adopted. To ensure stability, the predictor must satisfy a feasibility problem based on a time-varying delay-dependent condition expressed in terms of Linear Matrix Inequalities (LMI). Some aspects like the relation between network delay and robustness/performance trade-off are empirically studied. A simulation example shows the benefits (robustness and control performance improvement) of the NU-PO approach by comparison to another similar proposal.
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Yan Song,Jingcheng Wang,Yuanhao Shi,Chuang Li 제어·로봇·시스템학회 2011 International Journal of Control, Automation, and Vol.9 No.5
This paper is concerned with H_∞ control of networked control systems (NCSs) with both network-induced delay and packet disordering taken into account. A switching-based method depends on different cases of prediction numbers is presented to model the NCSs as a switched system. With the application of an improved prediciton-based method to compensate for the time delay and packet disordering, H_∞ controller is designed by solving the linear matrix inequalities (LMIs). The proposed method can be applied variously due to all kinds of prediciton numbers of the consective disordering packet have been considered, which means that our techniques are less conservative than existing lit-eratures. Finally numerical examples and simulations are used to illustrate the effectiveness and valid-ity of the proposed switching-based method and the improved prediction-based H∞ controller design synthesis.
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