• International Journal of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.22-30
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• 2023

The portable mobile devices with high performance and high speed 5G network activate and explode the demands for ubiquitous information services that remove the limitations of time for the communication and places to request for the information. NN (Nearest Neighbor) search is one of the most important types of queries to be processed efficiently in the information services. Various indexes have been proposed to support efficient NN search in the wireless broadcast system. The indexes adopting Hilbert curve, grid partition or Voronoi diagram enable the clients to search for NN quickly in the wireless broadcast channel. It is necessary that an efficient means to evaluate the performances of various indexes. In this paper, we propose an open framework that can adopt a variety of indexing schemes and evaluate and compare the performances of them. The proposed framework is organized with open and flexible structure that can adopt hybrid indexing schemes extensible to Voronoi diagram as well as simple indexing schemes. With the implemented framework, we demonstrate the efficiency and scalability and flexibility of the proposed framework by evaluating various indexing schemes for NN query.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.25-30
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• 2012

It is important to detect dangerous objects which are intentionally abandoned in public places. Nowadays visual surveillance system is required to enhance the performance in two ways : high resolution and wireless linking ability. In this study the design of visual surveillance system is newly proposed to detect abandoned objects for social security purpose based on wireless high resolution image transmission technology. Also, to enhance PED, PAT performance, the tracking algorithm is included in the previous visual surveillance software scheme. By implementing proposed design scheme on the real wireless high resolution image transmission system, the effectiveness of the overall system is shown with the transmission performance of 4.0 Gbps speed.

• Journal of information and communication convergence engineering
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• v.10 no.3
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• pp.220-224
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• 2012

We report an experimental demonstration of $4{\times}4$ multiple-input multiple-output (MIMO) wireless visible light communications (VLC) using a charge-coupled device image sensor receiver instead of a photodiode receiver. An image sensor is a kind of digital camera, which is used in most mobile devices such as smart phones or laptop computers and a promising commercial candidate for a VLC receiver. The transmission distance of the experimental result is over 10 m, enough for most indoor communication applications. We expect that the MIMO VLC technique based on image sensor receivers can be widely used with the development of high-speed image sensors.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.4
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• pp.489-495
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• 2018

In this paper, we designed and fabricated WLAN / UWB communication antennas operating at 3.3 [GHz] and 5 [GHz] bands in order to effectively use the high-speed communication network system that improved antenna miniaturization, gain and radiation pattern. Microstrip patch antennas were chosen to improve the bandwidth. The slot width, length, and transmission line width were calculated using the theoretical formula for each step. Simulation results show that the return loss is -14.053 [dB] at 3.3 [GHz] and -13.118 [dB] at 5 [GHz]. The gain showed a value of 2.479 [dBi] at 3.3 [GHz] and a value of 3.317 [dBi] at 5 [GHz]. After optimizing it with the CST Microwave Studio 2014 program, which can be 3D-designed, Based on these results, we investigated the performance of antennas by measuring their characteristics. In recent years, WLAN, which is a variety of wireless technologies that are continuously developing, and UWB, which is a communication technology which is increasing in frequency band due to an increase in demand of the technology users, is used for a high speed wireless communication system. Communication seems to be possible.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.1
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• pp.42-49
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• 2003

OFDM should be used for the fourth generation communication for high speed communication. Because of high spectral efficiency and high tolerance to fading channel, OFDM is applied to many high speed wire and wireless communication such as DAB (Digital Audio Broadcast), DVB(Digital Video Broadcast), IMT 2000 etc. Inter-modulation, however, is derived from PAR(Peak to Average Power Ratio) of OFDM signals. The paper describes PTS(Partial Transmit Sequence) and SLM(Select Mapping) of an existing methods which can reduce PAR. And then this papers proposed the new method that is called "Combine method". The method proposed in this paper is to combine PTS and SLM. As a result of the simulation, Combine PAR method is better than the existing methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1571-1578
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• 2014

Binary CDMA is a new standard technology for wireless communication developed by our country that makes high speed communications and good quality of services for multimedia data such as voice and video. In this paper we researched the design and implementation of a wireless Video Transmitter and Video Server - the main devices for the Automobile Wireless Camera System - based on the Binary-CDMA technology that makes them freely installed in any place without wired cables restriction.

• Journal of the Korean Society for Railway
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• v.16 no.4
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• pp.262-271
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• 2013

Wireless communication networks are recently taking an important role in railroad systems as railways now require high speed and high density operation with the aid of advanced information technology to improve maintenance efficiency and to handle passenger service growth. Train control systems are consequently changing from track circuitbased systems to communication-based systems. This paper analyses the role of wireless communication networks in recent railroad systems, reviews foreign cases, and then suggests a communication network constructing policy for increased transport capacity increase, securement of safety, and efficient train control.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.35-40
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• 2012

Since the opening of Korean high-speed rail, KTX in 2004, the use of trains in Korea soared. Improved rail technology, as well as the speed of the train was developed. However, the development of the train speed raised new issues of Doppler effect and this effect compensation. Depending on the speed of communication target, Doppler effect generates frequency shifting and this effect leads to a distortion of the signal. For this reason, the Doppler effect adversely affect the communication performance. Therefore, the Doppler effect problem must be solved for the railway wireless communication. In this paper, we present technique of compensation for the Doppler effect that occurs in high-speed railway communication and simulation result.

• Journal of IKEEE
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• v.4 no.2 s.7
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• pp.274-280
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• 2000

The fact that error probability is higher in wireless communication environment than the one in a fixed network makes it inappropriate to apply the same DLC (Data Link Control) protocol used in a wireline network to a wireless network. And since the existing DLC protocol for wireless network was optimized for low-rate data service, it is not suitable for a wireless network environment which should support high-speed and multimedia traffic. Therefore it is desperate to have a new DLC protocol for todays wireless mobile communication environment. In this paper, we propose an error control scheme in WATM (Wireless Asynchronous Transfer Mode) environment. which supportsmultiple traffic attributes, high-speed, multimedia data service. In this paper we modified the existing ASR ARQ (Adaptive Selective Repeat Automatic Repeat Request) protocol where cells exceeding maximum allowable delay range are discarded. And adding FEC (Forward Error Correction) for delay-sensitive traffic resulted in smaller increase of transmission delay.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.425-430
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• 2013

Robust and high speed underwater communication is severely limited when compared to communications in terrestial. In free space, RF communication operates over long distances at high data rates. However, the obstacle in seawater is the severe attenuation due to the conducting nature. Acoustic modems are capable of long range communication up to several tens of kilometers, but it has low data-rate, high power consumption and low propagation speed. An alternative means of underwater communication is based on optics, wherein high data rates are possible. In this paper, the characteristics of underwater channel in the range of visible wavelength is investigated. And the possibility of optical wireless communication in underwater is also described. The LED-based transceiver and CMOS sensor module are integrated in the system, and the performance of image transmission was demonstrated.