• Journal of Sensor Science and Technology
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• v.15 no.4
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• pp.263-268
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• 2006

We have demonstrated a highly sensitive temperature sensor using an etched single mode fiber with a thermally expanded core region. Large core size of thermally expanded core facilitates access to evanescent wave by the wet etching. The etched region was surrounded by a low dispersive external medium with high thermo-optic coefficient. Due to the large difference between the dispersion property of the fiber and that of the external medium, the device reveals a cut-off properties at spectral region. The cut-off wavelength was shifted by the variations of the environmental temperatures because of thermo-optic effect of the external medium. The sensitivity of the fabricated device was found to be $45nm/^{\circ}C$.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.12
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• pp.465-474
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• 2020

This study investigates how financial resources and entrepreneurial orientation (EO) may influence the performance of small- and medium-sized enterprises (SMEs) in the United Arab Emirates (UAE). Twenty-seven interviews were conducted and evaluated using the method of GABEK® (A GAnzheitliche BEwältigung von Komplexität - holistic processing of complexity). The research demonstrated that access to financial resources has significantly mediated EO's effect on the SMEs' performance. The study found that financial autonomy, enhanced through both personal financing and availability of external finance sources, plays a central role in supporting the EO dimension of autonomy and enhancing the SMEs' performance. In particular, the other EO dimension of risk-taking is stymied by lack of funds with which to take commercial and market opportunities. However, when an innovation strategy is pursued and adopted, access to finance can be facilitated, either through financial institutions or through other governmental funding programs attracting high potential innovators. Furthermore, financial barriers, difficulties accessing bank financing, and legal issues have a detrimental impact on SMEs' growth. The study has implications for policy-makers in the UAE, specifically in terms of sending a signal for lending institutions to consider strategies that provide access to affordable financial services to satisfy SMEs' needs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.10
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• pp.3458-3474
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• 2014

The performance of IEEE 802.11e enhanced distributed channel access (EDCA) is influenced by several interactive parameters that make quality of service (QoS) control complex and difficult. In EDCA, the most critical performance influencing parameters are the arbitration interframe space (AIFS) and contention window size (CW) of each access category (AC). The objective of this paper is to provide a scheme for parameter control such that the throughput per station as well as the overall system throughput of the network is maximized and controllable. For this purpose, a simple and accurate analytical model describing the throughput behavior of EDCA networks is presented in this paper. Based on this model, the paper further provides a scheme in which a Pareto optimal system configuration is obtained via an appropriate CW control for a given AIFS value, which is a different approach compared to relevant papers in the literature that deal with CW control only. The simulation results confirm the effectiveness of the proposed method which shows significant performance improvements compared to other existing algorithms.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.275-285
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• 2015

To improve the efficiency of carrier sense multiple access (CSMA)-based medium access control (MAC) protocols, CSMA with collision resolution (CSMA/CR) has been proposed. In the CSMA/CR, a transmitting station can detect a collision by employing additional sensing after the start of a data transmission and then resolve the next collision that might occur by broadcasting a jam signal during a collision detection (CD) period. In this paper, we analyze the delay of a CSMA/CR based on a generic p- persistent CSMA model and obtain the minimum achievable delay of the CSMA/CR by finding the optimal length of the CD period according to the number of contending stations. Through this delay analysis, we also investigate the throughput-delay characteristics of the CSMA/CR protocol according to various parameters. Analysis and simulation results show that the CSMA/CR has a considerably lower delay and its throughput-delay characteristic is significantly improved than the conventional CSMA/CA and wireless CSMA/CD protocols.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.1990-1992
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• 2001

In this paper, a NeuroFuzzy controller (NFC) with enhanced packet reservation multiple access (PRMA) protocol for QoS-guaranteed multimedia communication systems is proposed. The enhanced PRMA protocol adopts mini-slot technique for reducing contention cost, and these minislot are futher partitioned into multiple MAC regions for access requests coming from users with their respective QoS (quality-of-service) requirements. And NFC is designed to properly determine the MAC regions and access probability for enhancing the PRMA efficiency under QoS constraint. It mainly contains voice traffic estimator including the slot information estimator with recurrent neural networks (RNNs) using real-time recurrent learning (RTRL), and fuzzy logic controller with Mandani- and Sugeno-type of fuzzy rules. Simulation results show that the enhanced PRMA protocol with NFC can guarantee QoS requirements for all traffic loads and further achieves higher system utilization and less non real-time packet delay, compared to previously studied PRMA, IPRMA, SIR, HAR, and F2RAC.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.8
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• pp.1420-1426
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• 2008

This paper derives medium access delay of each AC(Access Category) in a stationary station using inter-departure time of IEEE 802.11e WLAN(Wireless LAN). Inter-departure time of IEEE 802.11e WLAN is obtained using saturation throughput of IEEE 802.11e WLAN which was the topic of our prior work. By using a simple queueing model, we evaluate mean queue length and mean delay for each AC on stationary condition. We calculate performance of each AC using this simple model and validate results using simulation.

• Journal of Korean Library and Information Science Society
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• v.49 no.4
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• pp.147-166
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• 2018

This study is to suggest the considerations in the rules for authorized access points for collocation of music work by figuring out the directions of authorized access points in FRBR, LRM, ICP 2016, RDA, and BIBFRAME, and by analyzing RDA rules for attributes and authorized access points of music works and expression and VIAF examples. First, an aggregated authorized access points were suggested as the direction of authorized access points, and original title may be selected as preferred title and the authorized access point may be based on forms in one of the languages suited to the users, if the original title is not normally suited. Second, music works's authorized access points is consisted of composer authorized access point and preferred title, and of adapter's authorized access point and preferred title in case of lacks of responsibility in composer. Also, the authorized access point of Korean traditional music work must be reviewed according to work types considering the responsibility of composer. Third, the controlled vocabularies for name of music type, medium of performance, and key could be considered for describing the attributes of work and expression. This study would be the foundation study for the authorized access point of music work, and additional research should be completed through surveying music user's need.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.1
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• pp.97-105
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• 2010

This paper proposes an effective medium access mechanism which is based on IEEE 802.11 to transmit an urgent message, The main features of the proposed mechanism are as follows. First, when it comes to channel access to have high priority, it has a shorter interval between frames than that specified in standard document. Second, we use fixed window size instead of back-off window with an exponential increase. Performance evaluation of proposed mechanism is executed by simulation and compare with the node using the specified mechanism in standard document. Performance evaluation results show that according to increasing competition the nodes using proposed method have less accessing time than the conventional methods. Also, the proposed method can improve processing time because of the decreasing transmission delay.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2636-2656
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• 2013

To improve the cooperative efficiency of node cooperation and multiple access performance for multihop wireless networks, a priority-differentiated cooperative medium access control protocol with contention resolution (CRP-CMAC) is proposed. In the protocol, the helper selection process is divided into the priority differentiation phase and the contention resolution phase for the helpers with the same priority. A higher priority helper can choose an earlier minislot in the priority differentiation phase to send a busy tone. As a result, the protocol promptly selects all the highest priority helpers. The contention resolution phase of the same priority helpers consists of k round contention resolution procedures. The helpers that had sent the first busy tone and are now sending the longest busy tone can continue to the next round, and then the other helpers that sense the busy tone withdraw from the contention. Therefore, it can select the unique best helper from the highest priority helpers with high probability. A packet piggyback mechanism is also adopted to make the high data rate helper with packet to send transmit its data packets to its recipient without reservation. It can significantly decrease the reservation overhead and effectively improve the cooperation efficiency and channel utilization. Simulation results show that the maximum throughput of CRP-CMAC is 74%, 36.1% and 15% higher than those of the 802.11 DCF, CoopMACA and 2rcMAC protocols in a wireless local area network (WLAN) environment, and 82.6%, 37.6% and 46.3% higher in an ad hoc network environment, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.5
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• pp.1249-1259
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• 1998

This paper proposes an efficient channel assignment method for real-time service in the IEEE 802.11 Wireless LAN system, and analyzes the supportability to real-time service and the channel utilzation of that through computer simulations. The improved MAC(Medium Access Control) protocol employing the proposed channel assignment method achieved good throughput over contention period as well as contention-free period by making real-time terminals transmit the information about their desiring value before starts of data transmissions. For performance evaluation of the proposed method, a simulation analyzing the variation of allocated bandwidths to terminals using real-time service and their buffer sizes wasexecuted. Real-time data traffics was modeled s 7-stae transition VBR sources, and asynchronous data traffics modeled as Poisson processes. In the simulation, the proposed method showed smaller variation of the bandwidth of each terminal and samller buffer size than the existing method, and also recorded good throughput over contention period.