• Journal of information and communication convergence engineering
• /
• v.10 no.3
• /
• pp.237-241
• /
• 2012

In wireless sensor networks, the importance of transporting data correctly with reliability is increasing gradually along with the need to support communications between the nodes and sink. Data flow from the sink to the nodes requires reliability for control or management that is very sensitive and intolerant of error; however, data flow from the nodes to the sink is relatively tolerant. In this paper, with emphasis on the data flow from the sink to the nodes, we propose a mechanism that considers accurate transport with reliability hop-by-hop. During the process of sending the data, if errors occur or data is missing, the proposed mechanism supports error recovery using a fixed window with selective acknowledgment. In addition, this mechanism supports congestion control depending on the buffer condition. Through the simulation, we show that this mechanism is accurate, reliable, and proper for transport in wireless sensor networks.

• Journal of KIISE:Computer Systems and Theory
• /
• v.26 no.7
• /
• pp.827-838
• /
• 1999

멀티미디어 통신에서 통신 성능에 관련된 요구 사항들은 QoS 매개 변수들로서 서술된다. QoS매개 변수들에서 중요한 매개 변수 중의 하나가 전송 신뢰성이다. QoS 매개 변수로서의 신뢰성은 오류 감지, 보고 그리고 정정 기법으로 정의된다. 하지만 기존의 오류 제어 기법들은 멀티미디어 데이타의 통합된 관점을 고려하지 않았다. 그래서 우리는 MEC(multimedia-oriented error control)라고 명명된 오류 제어 기법을 제안하였다. 1 본 논문에서는 MEC기법의 성능을 조사 하였다. 성능평가 결과는 MEC기법이 기존의 오류 제어 기법보다도 낮은 전송지연(lower delay)과 호손율(blocking probability) 을 갖는다는 것을 볼 수 있었다. 결국 제안된 MEC기법은 수송 프로토콜에게 유연성과 높은 성능을 갖도록 해준다.Abstract Communication performance requirements are described as QoS parameters in multimedia communication. One of the important QoS parameters is the reliability of the transfer. As a QoS parameter, the reliability defines error detection, report and correction mechanisms. Conventional error control mechanisms, however, do not consider the integrated viewpoint of multimedia data. So we have proposed the MEC(multimedia-oriented error control). 1 In this paper, we have investigated the performance evaluation of the MEC. The results show that the MEC mechanism provides lower transfer delay and blocking probability than those of the conventional error recovery mechanism. Therefore, the proposed MEC mechanism makes the transport protocol have the flexibility and high performance.

• Journal of KIISE:Computer Systems and Theory
• /
• v.26 no.10
• /
• pp.1225-1236
• /
• 1999

기존의 오류 제어 방법들은 실시간 특성과 신축적인 신뢰성을 가지는 멀티미디어 통신 응용의 특징을 충분히 반영하지 못하고 있다. 본 연구는 기존의 재전송을 기반으로 하는 방법에 두 가지 기법을 추가하여 이 문제에 접근하였다. 첫째, 실시간 데이타의 마감 시간을 고려하여 미리 재전송을 실시하는 사전 재전송과 시간적으로 불가능하다고 판단될 때 복구를 포기하는 재전송 포기를 통한 적시 재전송 기법이다. 둘째, 요구되는 신뢰성에 근접하도록 오류가 많이 발생하였을 때만 재전송을 하는 선택적 오류 제어 기법이다. 본 연구는 두 기법을 적용한 오류 제어 프로토콜을 구현하고 네트워크 환경을 바꾸어 가며 성능을 검사하였다. 실험 결과, 제안된 오류 제어 방법은 전체적인 오류 제어 부하는 감소시키면서 오류 복구율을 높인다는 점을 확인하였다.Abstract The current error control schemes do not fit well to the characteristics of multimedia communications: real-time transmission and flexible reliability requirements. This research proposes a new error control scheme, which extends the retransmission-based error control with the following two mechanisms. First, error recovery is performed in two timely fashions: one is retransmission in advance where a retransmission is performed early enough for the deadline if an error is suspected, and the other is retransmission abort where a retransmission is given up if its recovery within the deadline seems to be impossible. Second, error control is selectively performed only when an actual error rate approaches to the threshold on a given reliability requirement. The proposed scheme has been implemented and experimented in various network environments. The performance results show that it has lower control overhead and higher error recovery than the existing schemes.

• Journal of Communications and Networks
• /
• v.15 no.4
• /
• pp.422-429
• /
• 2013

Advances in wireless sensor network (WSN) technology have enabled small and low-cost sensors with the capability of sensing various types of physical and environmental conditions, data processing, and wireless communication. In the WSN, the sensor nodes have a limited transmission range and their processing and storage capabilities as well as their energy resources are limited. A triple umpiring system has already been proved for its better performance in WSNs. The clustering technique is effective in prolonging the lifetime of the WSN. In this study, we have modified the ad-hoc on demand distance vector routing by incorporating signal-to-noise ratio (SNR) based dynamic clustering. The proposed scheme, which is an efficient and secure routing protocol for wireless sensor networks through SNR-based dynamic clustering (ESRPSDC) mechanisms, can partition the nodes into clusters and select the cluster head (CH) among the nodes based on the energy, and non CH nodes join with a specific CH based on the SNR values. Error recovery has been implemented during the inter-cluster routing in order to avoid end-to-end error recovery. Security has been achieved by isolating the malicious nodes using sink-based routing pattern analysis. Extensive investigation studies using a global mobile simulator have shown that this hybrid ESRP significantly improves the energy efficiency and packet reception rate as compared with the SNR unaware routing algorithms such as the low energy aware adaptive clustering hierarchy and power efficient gathering in sensor information systems.

• BMB Reports
• /
• v.51 no.9
• /
• pp.437-443
• /
• 2018

Non-homologous end joining (NHEJ), and to a lesser extent, the error-free pathway known as homology-directed repair (HDR) are cellular mechanisms for recovery from double-strand DNA breaks (DSB) induced by RNA-guided programmable nuclease CRISPR/Cas. Since NHEJ is equivalent to using a duck tape to stick two pieces of metals together, the outcome of this repair mechanism is prone to error. Any out-of-frame mutations or premature stop codons resulting from NHEJ repair mechanism are extremely handy for loss-of-function studies. Substitution of a mutation on the genome with the correct exogenous repair DNA requires coordination via an error-free HDR, for targeted transgenesis. However, several practical limitations exist in harnessing the potential of HDR to replace a faulty mutation for therapeutic purposes in all cell types and more so in somatic cells. In germ cells after the DSB, copying occurs from the homologous chromosome, which increases the chances of incorporation of exogenous DNA with some degree of homology into the genome compared with somatic cells where copying from the identical sister chromatid is always preferred. This review summarizes several strategies that have been implemented to increase the frequency of HDR with a focus on somatic cells. It also highlights the limitations of this technology in gene therapy and suggests specific solutions to circumvent those barriers.

• Journal of Internet Computing and Services
• /
• v.8 no.5
• /
• pp.125-132
• /
• 2007

Transmission mechanisms that include an available bandwidth estimation algorithm and a packet loss differentiation scheme, in general, exhibit higher TCP performance in wireless networks. TCP New Jersey, known as the best existing scheme in terms of goodput, improves wireless TCP performance using the available bandwidth estimation at the sender and the congestion warning at intermediate routers. Although TCP New Jersey achieves 17% and 85% improvements in goodput over TCP Westwood and TCP Reno, respectively, we further improve TCP New Jersey by exploring improved available bandwidth estimation, retransmission timeout, and recovery mechanisms. Hence, we propose TCP New Jersey PLUS (shortly TCP NJ+), showing that under 1% packet loss rate, it outperforms 3% by TCP New Jersey and 5% by TCP Wes1wood. In 5% packet loss rate, a characteristic of high bit-error-rate wireless network, it outperforms other TCP variants by 19% to 104% in terms of goodput even when the network is in bi-directional congestion.

• Journal of KIISE:Information Networking
• /
• v.30 no.4
• /
• pp.513-519
• /
• 2003

In order to deliver multicast traffic efficiently, multicast routing and reliable transmission mechanisms are required. The reliable delivery implies that lost packets must be retransmitted, which in turn requires that transmitted packets be stored in a retransmission buffer. Therefore how to manage a retransmission buffer is important and, in this paper, we try to solve the problem of how many packets should be maintained in the buffer. Our proposed scheme, the timer-based buffer management (TBM), maintains only necessary amount of buffer based on the timer value calculated from the NAKs between the replier and receivers on a multicast tree and can adjust to the dynamic network conditions. By performing simulations, we show that TBM manages the buffer efficiently regardless of the error situation, network size, and so on.

• The Transactions of the Korea Information Processing Society
• /
• v.6 no.8
• /
• pp.2233-2244
• /
• 1999

It is essential to guarantee high reliability of embedded real-time systems since the failure of such systems may result in large financial damage or threaten human life. Though many researches have devoted to fault tolerant mechanisms, most of them are object-level fault tolerant mechanisms that can detect errors occurred in a single object and treat the errors in object-level. As embedded real-time systems become more complex and larger, there exist faults that cannot be detected by or tolerated with object-level fault tolerance. Hence, system-level fault tolerance is needed. System-level fault tolerance examines the status of a system whether the system is normal or not by analyzing the status of objects. When an error is detected it should be capable of locating the fault and performing an appropriate recovery and reconfiguration action. In this paper, we propose RobustRTO(Robust Real-Time Object) that provides object-level fault tolerance capability and RMO(Region Monitor real-time Object) that offers system-level fault tolerance capability. Then we show how highly dependable fault tolerant systems can be modeled by RobustRTO and RMO. The model is presented based on real-time objects.