• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.1 s.12
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• pp.47-57
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• 2007

In this paper, optimal parameters of a hopping pilot beacon are analyzed in a CDMA mobile cellular network. The hopping pilot beacon is used for inter-frequency handoff. It can reduce the number of pilot beacons needed for the inter-frequency handoff by transmitting neighbor frequency pilots periodically through a pilot beacon. The optimal parameters for transmission time and period of the hopping pilot bacon are derived by mathematical approach. It is highly recommended that the optimal values for the hopping pilot beacon under various operation environments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.8
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• pp.1380-1385
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• 2006

A Pipelined Tone Wakeup(PTW) scheme(1) was proposed to support energy saving and end-to-end delay for sensor networks by providing an asynchronous wakeup pipeline to overlap the wakeup procedures with the packet transmission. But the scheme uses two radios and assumes error-free environments. In this paper, we propose a modified PTW scheme for wireless sensor networks. The proposed scheme is based on the PTW. The difference is that next hop information will be included in the ack packet from receiver node to sender node, So all the other neighbor nodes can stay in sleep mode long enough to save energy. Also ore get enhanced delay performance.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.11a
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• pp.375-378
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• 2009

The Spectrum Sensing Technology is the core technology of the Cognitive Radio (CR) System that is one of the future wireless communication technologies. This is the technology that temporarily allocates the frequency bandwidth by scanning surrounding wireless environments to keep licensed terminals and search the unused frequency bandwidth. In this paper, we proposed the efficient Spectrum Sensing Method using the Short Time Fourier Transform (STFT). The Cosine and DVB-H signal with the 6MHz bandwidth is used as the Input Signal. And we confirm the Spectrum Sensing result using Modified Periodogram Method, Welch's Method for compared with Short Time Fourier Transform Algorithm.

• Journal of Astronomy and Space Sciences
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• v.32 no.2
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• pp.101-112
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• 2015

Magnetic reconnection is a fundamental process occurring in a wide range of astrophysical, heliospheric and laboratory plasmas. This process alters magnetic topology and triggers rapid conversion of magnetic energy into thermal heating and nonthermal particle acceleration. Efforts to understand the physics of magnetic reconnection have been made across multiple disciplines using remote observations of solar flares and in-situ measurements of geomagnetic storms and substorms as well as laboratory and numerical experiments. This review focuses on the progress achieved with solar flare observations in which most reconnection-related signatures could be resolved in both space and time. The emphasis is on various observable emission features in the low solar atmosphere which manifest the coronal magnetic reconnection because these two regions are magnetically connected to each other. The research and application perspectives of solar magnetic reconnection are briefly discussed and compared with those in other plasma environments.

• Journal of Astronomy and Space Sciences
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• v.29 no.1
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• pp.63-67
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• 2012

Observations with milliarsecond resolution using the Navy Optical Interferometer have been obtained for a number of stellar systems which include high-mass binaries, eclipsing binaries, and radio stars. These observations also reveal the previously unseen companions in single-lined spectroscopic binaries via directly measured flux ratios. We will present examples of published and ongoing research efforts of these systems to illustrate how an optical interferometer contributes to our knowledge of stars, their environment, and companions. These studies include a conclusive revealing of the previously unseen companion in the single-lined binary ${\Phi}$ Herculis, the direct determination of orbital parameters in the wide and close orbits of Algol, and revealing the orbit of ${\beta}$ Lyrae with spatially resolved images of the $H{\alpha}$ emission.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.505-508
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• 2001

Remote Sensing is one of effective methods for collecting, analyzing information and predicting the change of agricultural environments. The RS technique is based on the principle that the object reflects a peculiar radio wave according to types and environmental conditions. For collection RS base data, used spectroradiometer which measures reflection characteristics between $300{\sim}1,100nm$ and measured the reflection of Mi-ho stream's water resources which is located thong-won, Chung-buk province, Korea. The difference of reflectance represents the characteristic of bottom soil, water color and matters in water.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.248-253
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• 1999

The content of this paper is concerned with the revision of technical specifications for the wireless microphone used in domestic. In order to revise the technical specifications at present, this paper analyzes radio interference to other station used adjacent band and introduces RF specifications of wireless microphone in worldwide. And the paper proposes draft revision of technical specifications for wireless microphone in accordance with domestic frequency environments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.379-382
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• 2007

In ubiquitous sensor networks(USNs), various sensing devices deployed in wireless sensor networks collect meaningful data from physical environments and the data are delivered to neighbor node through radio interfaces for further processing. In this processing, efficiently using of the limited source of low power and low cost is USNs on the point of energy consumption. In this paper, we measure and analyze the power consumption of LR-WPAN.

• Journal of information and communication convergence engineering
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• v.15 no.1
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• pp.28-36
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• 2017

The medium access control (MAC) protocol based on dynamic time division multiple access/time division duplex (TDMA/TDD) is responsible for random access control and radio resource allocation in dynamic traffic environments. These functions of random access and resource allocation are very important to prevent wastage of resources and improve MAC performance according to various network conditions. In this paper, we propose new random access and resource allocation schemes to guarantee quality of service (QoS) and provide priority services in a dynamic TDMA/TDD system. First, for the QoS guarantee, we propose an adaptive random access and resource allocation scheme by introducing an access probability. Second, for providing priority service, we propose a priority-based random access and resource allocation scheme by extending the first adaptive scheme in both a centralized and a distributed manner. The analysis and simulation results show that the proposed MAC protocol outperforms the legacy MAC protocol using a simple binary exponential backoff algorithm, and provides good differential performance according to priorities with respect to the throughput and delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8B
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• pp.657-666
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• 2008

The intersection collision avoidance service among various telematics application services is regarded as one of the most critical services with regard to safety. In such safety applications, real-time, correct transmission of service is required. In this paper, we study on efficient infrastructure architecture for intersection collision avoidance using a cooperative mechanism between vehicles and wireless infrastructure. In particular, we propose an infrastructure, called CISN (Cooperative Infrastructure associated with Sensor Networks), in which proper numbers of sensor nodes are deployed on each road, surrounding the intersection. In the proposed architecture, overall service performance is influenced by various parameters consisting of the infrastructure, such as the number of deployed sensor nodes, radio range and broadcast interval of base station, and so on. In order to test the feasibility of the CISN model in advance, and to evaluate the correctness and real-time transmission ability, an intersection sensor deployment simulator is developed. Through various simulations on several environments, we identify optimal points of some critical parameters to build the most desirable CISN.