• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.58-58
• /
• 2000

As many sensors and actuators are used in various automated systems, the application of network system to real-time distributed control is gaining acceptance in many industries. In order to take advantages of the network technique. however, network implementation should be carefully designed to satisfy real-time constraints and to consider network delays. This paper presents the implementation of feedback control system in Profibus-DP. Profibus-DP is a type of fieldbus protocols that are specifically designed to interconnect simple devices with fast I/O data exchange. As feedback control in profibus-DP is implemented, Network delays is found with influence of system performance. We analyze network delays in Profibus-DP into 3 reasons - dead time in Profibus interface, protocol delay, delay by asynchronization. In order to compensate the network delays, we introduce control algorithms with time delay concept. The results show that network delay can be compensated.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.22 no.1
• /
• pp.139-150
• /
• 1997

For high-speed networks, a new ring protocal is proposed in this paper. A ring network combined with destination removal can achieve much higher network throughput than the channel transmission rate. However, such a network exhibits fairness problems. Over a past few years, global fairness algorithms such as ATMR and Metaring have been proposed to solve such problems. But the ring access time delay and fairness in such networks are sensitive to the network parameters such as network size and traffic distribution. In addition to guaranteeing fair ring access to all nodes, there are several other important performance aspects in such networks. The one is that fairness is enforced while node throughputs are kept as high as possible. And another performance measure is access delay and more specifically Head-Of-Line(HOL) delay, i.e., the amount of time the first cell in the transmission buffer of a node has to wait before it accesses the ring. HOL delay is a mijor component in the transmission jitter of the synchronous traffic transmission. A key idea of the proposed ring protocol is to find the nodes that have much more chances to access the ring than any other nodes in the independently distributed node architecture. Since destined by many cells need to share a part of the bandwidths with the next node for the fairness in as much as performance degradation does not become critical. To investigate the performance behavior of the proposed ring protocol for various network condition,s several performance parameters wuch as ring access time delay, and throughput are compared with those of the ATMR and Metaring protocols using simulation package, SIMAN.

• Journal of the Korean Society of Radiology
• /
• v.15 no.5
• /
• pp.575-584
• /
• 2021

The aim of this study was to achieve optimal portal phase while reducing contrast medium by applying weight-based dose protocol compared to standard fixed dose protocol to performing of pediatric abdominal CT examination. Discovery 750HD (General Electric Medical Systems, Milwaukee, USA) was used, and a total of 167 children consisting of 85 men and 82 women under the age of 18 were studied. The group in which the 300 mgI/ml(Xenetix, Guerbet, France) contrast medium was fixedly injected at twice body weight and the group injected with physiological saline while gradually decreasing the injection amount by 10% while applying the weight-based protocol were distinguished. Also, the CT number and SNR of abdominal organs were compared and evaluated while changing the scan delay time. Subjective image quality of enhancement and beam-hardening artifacts of around the heart was assessed with five-point criterion. The group adapted weight-based protocol with 20% reduction in contrast medium was most similar in contrast enhancement in the group with fixed injection at twice body weight. Furthermore, the group with a delay time of 20% had the highest contrast enhancement effect, and the difference in CT attenuation coefficient from the group scanned immediately after injection of the contrast media. Therefore, the appropriate delay time after injection of the contrast agent increased the contrast enhancement of the parenchymal organ. In addition, the weight-based injection protocol with normal saline reduced artifacts around the heart, and the effect of contrast enhancement could be maintained. In conclusion, it is possible to reduce dosage of contrast media through the application of weight-based injection protocols and appropriate latency, and to characterize optimal portal phase imaging on pediatric abdominal CT.

• Proceedings of the Korean Information Science Society Conference
• /
• 2000.10c
• /
• pp.111-113
• /
• 2000

We discuss the problem of resource reservation, such as bandwidth, for delay sensitive application in wireless networking environment. As multimedia application is becoming a critical role of the current mobile network, the resource reservation become very important to support the real-time service. In this paper, we propose and evaluate a new resource reservation protocol, called Split Reservation Protocol, in wireless network. The simulation results show that our proposed protocol outperforms an existing protocol called MPSVP in terms of network overhead.

• Proceedings of the IEEK Conference
• /
• 2003.07a
• /
• pp.133-136
• /
• 2003

In this paper, we propose a multicast routing protocol for the seamless delivery of multicast data to mobile hosts through the optimal route in IP based mobile networks. The proposed multicast routing protocol is a hybrid method employing the merits of the bi-directional tunneling and the remote subscription by considering the mobility of mobile hosts. The proposed protocol satisfies the bound of end-to-end delay and supports the seamless handoff. The simulation results show that the proposed protocol has better performance in the number of multicast tree reconstruction and tunneling length and packet loss time than the previous protocols.

• Journal of KIISE:Information Networking
• /
• v.34 no.6
• /
• pp.483-492
• /
• 2007

In this paper, we propose a new hybrid approach based on query tree protocol to arbitrate tag collisions in RFID systems. The hybrid query tree protocol that combines a tree based query protocol with a slotted backoff mechanism. The proposed protocol decreases the average identification delay by reducing collisions and idle time. To reduce collisions, we use a 4-ary query tree instead of a binary query tree. To reduce idle time, we introduce a slotted backoff mechanism to reduce the number of unnecessary Query commands. Simulation and numerical analysis reveal that the proposed protocol achieves lower identification delay than existing tag collision arbitration protocols.

• Proceedings of the IEEK Conference
• /
• 2003.11c
• /
• pp.157-163
• /
• 2003

IEEE 802.11a Distributed Coordination Function(DCF) Protocol을 사용하여 Real-Time MultiMedia Data의 전송을 수행할 경우, DCF Protocol의 적합하지 못한 Mechanism에 의하여, Data 전송의 극대화를 이루지 못한다. Retransmission이 반복되는 경우, Binary Slotted Exponential Backoff Mechanism은 거대한 Packet Delay와 Jitter의 원인이 되며 Automatic Repeat Request(ARQ) 방식의 Ack Mechanism은 MultiMedia Data를 전송하기에 적합하지 못하다. 본 논문은 위와 같은 문제점을 해결하기 위하여 Real-Time MultiMedia Data을 주로 전송하는 STA에 따른 Real-Time/Non-Real-Time(RT/NRT) Station(STA)의 구분과 보내고자 하는 Real-Time MultiMedia Data의 Network Traffic Load(The Required Bandwidth)를 고려하여, Modified DCF(mDCF) Protocol의 Modified Backoff(mBackOff), Modified BlockAck(mBlockAck) Mechanism을 제시함으로서, Data 전송의 극대화를 제공하며, 또한 IEEE 802.11a와의 호환성을 제공한다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.1
• /
• pp.331-343
• /
• 2015

We propose a distributed medium access control protocol for cognitive radio networks to opportunistically utilize multiple channels. Under the proposed protocol, cognitive radio nodes forecast and rank channel availability observing primary users' activities on the channels for a period of time by time series analyzing using smoothing models for seasonal data by Winters' method. The proposed approach protects primary users, mitigates channel access delay, and increases network performance. We analyze the optimal time to sense channels to avoid conflict with the primary users. We simulate and compare the proposed protocol with the existing protocol. The results show that the proposed approach utilizes channels more efficiently.

• Journal of Korean Neurosurgical Society
• /
• v.65 no.2
• /
• pp.224-235
• /
• 2022

Objective : Since the outbreak of the coronavirus disease 2019 (COVID-19) pandemic, neurointerventionists have been increasingly concerned regarding the prevention of infection and time delay in performing emergency thrombectomy procedures in patients with acute stroke. This study aimed to analyze the effects of changes in mechanical thrombectomy protocol before and after the COVID-19 pandemic on procedure time and patient outcomes and to identify factors that significantly impact procedure time. Methods : The last-normal-to-door, first-abnormal-to-door, door-to-imaging, door-to-puncture, and puncture-to-recanalization times of 88 patients (45 treated with conventional pre-COVID-19 protocol and 43 with COVID-19 protection protocol) were retrospectively analyzed. The recanalization time, success rate of mechanical thrombectomy, and modified Rankin score of patients at discharge were assessed. A multivariate analysis was conducted to identify variables that significantly influenced the time delay in the door-to-puncture time and total procedure time. Results : The door-to-imaging time significantly increased under the COVID-19 protection protocol (p=0.0257) compared to that with the conventional pre-COVID-19 protocol. This increase was even more pronounced in patients who were suspected to be COVID-19-positive than in those who were negative. The door-to-puncture time showed no statistical difference between the conventional and COVID-19 protocol groups (p=0.5042). However, in the multivariate analysis, the last-normal-to-door time and door-to-imaging time were shown to affect the door-to-puncture time (p=0.0068 and 0.0097). The total procedure time was affected by the occlusion site, last-normal-to-door time, door-to-imaging time, and type of anesthesia (p=0.0001, 0.0231, 0.0103, and 0.0207, respectively). Conclusion : The COVID-19 protection protocol significantly impacted the door-to-imaging time. Shortening the door-to-imaging time and performing the procedure under local anesthesia, if possible, may be required to reduce the door-to-puncture and door-to-recanalization times. The effect of various aspects of the protection protocol on emergency thrombectomy should be further studied.

• Journal of Korea Multimedia Society
• /
• v.19 no.8
• /
• pp.1460-1465
• /
• 2016

In this paper, we propose an energy efficient and multimedia traffic friendly MAC protocol (EEMF-MAC) that controls sender's wakeup period based on the data packet's transmission urgency and the receiver's wakeup periods based on the received data packet traffic loads. The protocol is useful for applications such as object tracking, real time data gathering, in which priority-based packet transmission is required. The basic idea of EEMF-MAC is that it uses the priority concept with transmission urgency of sender's data packet to reduce the transmission delay of the urgent data and it also uses duty cycling technique in order to achieve energy efficiency. EEMF-MAC showed a better performance in energy efficiency and packet transmission delay compared to existing protocols, RI-MAC and EE-RI-MAC.