• Journal of Information Processing Systems
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• v.10 no.2
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• pp.300-313
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• 2014

Various Time Synchronization protocols for a Wireless Sensor Network (WSN) have been developed since time synchronization is important in many time-critical WSN applications. Aside from synchronization accuracy, energy constraint should also be considered seriously for time synchronization protocols in WSNs, which typically have limited power environments. This paper performs analysis of prominent WSN time synchronization protocols in terms of power consumption and test by simulation. In the analysis and simulation tests, each protocol shows different performance in terms of power consumption. This result is helpful in choosing or developing an appropriate time synchronization protocol that meets the requirements of synchronization accuracy and power consumption (or network lifetime) for a specific WSN application.

• Journal of the Korea Society of Computer and Information
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• v.19 no.6
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• pp.61-69
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• 2014

Various Time Synchronization protocols considering for the characteristics of WSN(Wireless Sensor Network) have been developed, because a time relationship plays an important role in many WSN applications, as well. Synchronization accuracy as well as constraints of energy should be considered for WSN Time Synchronization protocols, especially. In this paper, I analyze Time Synchronization protocols for WSN after classifying these protocols with a new criteria (i.e. power consumption). So, this method will contribute to evaluating and comparing WSN Time Synchronization protocols in respect of power consumption.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.722-728
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• 2011

Most services need to have authentication protocols to verify users' eligibility in the network environment. For this, a lot of user authentication protocols have been researched and developed. Two of them, SPMA and I-SPMA protocols, introduced the lack of mutual authentication and vulnerability to the reply attack of the prior protocols and suggested revised protocols. Nevertheless, these protocols did not mention about the critical problem caused when the server and the client lose synchronization on the secret information between them. Therefore, in this paper, we analyze the security characteristics of the existing protocols and prove the vulnerability to the synchronization of the protocols.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.10
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• pp.3361-3377
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• 2014

Synchronous computing models provided by real-time synchrony protocols, such as TTA [1] and PALS [2], greatly simplify the design, implementation, and verification of real-time distributed systems. However, their application to real systems has been limited since their assumptions on underlying systems are hard to satisfy. In particular, most previous real-time synchrony protocols hypothesize the existence of underlying fault tolerant real-time networks. This, however, might not be true in most soft real-time applications. In this paper, we propose a practical approach to a synchrony protocol, called Quality-Aware PALS (qPALS), which provides the benefits of a synchronous computing model in environments where no fault-tolerant real-time network is available. qPALS supports two flexible global synchronization protocols: one tailored for the performance and the other for the correctness of synchronization. Hence, applications can make a negotiation flexibly between performance and correctness. In qPALS, the Quality-of-Service (QoS) on synchronization and consistency is specified in a probabilistic manner, and the specified QoS is supported under dynamic and unpredictable network environments via a control-theoretic approach. Our simulation results show that qPALS supports highly reliable synchronization for critical events while still supporting the efficiency and performance even when the underlying network is not stable.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.12
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• pp.1099-1105
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• 2000

The interactive bicycle simulator presented in this paper consists of a Stewart platform manipulator, magneto-rheological steering and braking devices, and a visual simulator. To provide a rider with reality, these devices should be controlled in real-time and motions of the devices and the visual should be also synchronized. If any of the devices and the visual gets unsynchronized due to significant blocking of control signals, the reality of the simulator is no longer secured. This paper presents communication protocols that minimize the blocked time of the control processes to guarantee the synchronization. The protocols are designed based on IPC (InterProcess Communications) of QNX, TCP/IP, and serial communication. The performance of the designed communication protocols is evaluated with the implemented bicycle simulator, and found satisfactory.

• Journal of Veterinary Clinics
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• v.31 no.5
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• pp.382-388
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• 2014

The objective of this study was to determine the risk factors associated with pregnancy following 3 synchronization protocols in dairy cows. Data were collected on 1,952 cows from 22 dairy farms, including synchronization protocols ($PGF_{2{\alpha}}$ + estradiol benzoate [PG+EB], Ovsynch, and CIDR-ovsynch), cow parity, body condition score (BCS), and dates of previous calving, insemination and conception. The odds ratio (OR) for pregnancy were analyzed by logistic regression using the LOGISTIC procedure in SAS. The analysis revealed that farm (p = 0.005), cow parity (p = 0.0001), BCS (p < 0.005), and AI season (p < 0.05) significantly affected and calving to AI interval tended to affect (p < 0.1) the probability for pregnancy. Although synchronization protocols did not affect the probability for pregnancy (p > 0.05), cow parity and synchronization protocols showed a significant interaction (p < 0.005); the OR (0.60) was significantly lower (p < 0.0001) for multiparous cows compared to primiparous cows using PG+EB, whereas the OR (1.44) tended to be higher (p < 0.1) for multiparous cows compared to primiparous cows using the Ovsynch, and the probability for pregnancy did not differ between multiparous and primiparous cows using the CIDR-ovsynch (p > 0.05). Cows with BCS ${\geq}$ 3.00 were more likely pregnant (OR: 1.41) compared with cows having BCS ${\leq}$ 2.75, whereas cows inseminated during summer had a lower OR (0.73) compared with those inseminated during spring. Cows with a calving to AI interval > 150 days were more likely to be pregnant (OR: 1.20) compared with cows with a calving to AI interval ${\leq}$ 150 days. In conclusion, the OR for pregnancy following synchronization protocols in dairy cows was affected by farm, parity, BCS, calving to AI interval of the cow, and AI season, and there was a significant interaction between cow parity and synchronization protocols; the OR for pregnancy was lower for multiparous cows compared with primiparous cows using the PG+EB protocol.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.84-86
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• 2010

Time information and time synchronization are fundamental building blocks in wireless sensor networks since many sensor network applications need time information for object tracking, consistent state updates, duplicate detection and temporal order delivery. Various time synchronization protocols have been proposed for sensor networks because of the characteristics of sensor networks which have limited computing power and resources. However, none of these protocols have been designed with time representation scheme in mind. Global time format such as UTC TOD (Universal Time Coordinated, Time Of Day) is very useful in sensor network applications. In this paper we propose time keeping and synchronization method for global time presentation in wireless sensor networks.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.415-417
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• 2005

Core operations (e.9. TDMA scheduler, synchronized sleep period, data aggregation) of many proposed protocols for different layer of sensor network necessitate clock synchronization. Our Paper mingles the scheme of dynamic clustering and diffusion based asynchronous averaging algorithm for clock synchronization in sensor network. Our proposed algorithm takes the advantage of dynamic clustering and then applies asynchronous averaging algorithm for synchronization to reduce number of rounds and operations required for converging time which in turn save energy significantly than energy required in diffusion based asynchronous averaging algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.264-274
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• 2014

Time synchronization becomes a critical issue in underwater acoustic networks (UANets) because nodes cooperate together or individually work by communicating each other in diverse underwater applications. Compared with the time synchronization approaches in terrestrial networks, several intrinsic limitations of UANets (e.g., the unavailability of GPS, long propagation delay, mobility due to currents, limited energy consumption, or low data rate) need to be considered in synchronizing the timing among underwater nodes. For the purpose of developing more efficient time synchronization protocols for UANets, we review the existing approaches, which estimate both the clock offset and the clock skew of underwater nodes. Finally, we outline the state-of-the art time synchronization protocols for UANets by comparing and summarizing them according to their synchronization characteristics.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.4
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• pp.103-113
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• 2007

In this paper, we present a security analysis of Lightweight RFID Mutual Authentication Protocols-LMAP[10], $M^2AP$[11], EMAP[12]. Based on simple logic operations, the protocols were designed to be suitable for lightweight environments such as RFID systems. In [8,9], it is shown that these protocols are vulnerable to do-synchronization attacks with a high probability. The authors also presented an active attack that partially reveals a tag's secret values including its ID. In this paper, we point out an error from [9] and show that their do-synchronization attack would always succeed. We also improve the active attack in [9] to show an adversary can compute a tag's ID as well as certain secret keys in a deterministic way. As for $M^2AP$ and EMAP, we show that eavesdropping $2{\sim}3$ consecutive sessions is sufficient to reveal a tag's essential secret values including its ID that allows for tracing, do-synchronization and/or subsequent impersonations.