• Journal of the Optical Society of Korea
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• v.19 no.4
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• pp.351-356
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• 2015

Visible light communication (VLC) is considered to be an attractive scheme to realize the broadband wireless communication for an indoor environment. We present a room division multiplexing (RDM) mechanism for an indoor multi-room VLC network, which utilizes the spatial position of the LED lamp in different rooms as a novel dimension of network resource for multiplexing, and thus the network capacity is increased. In such a network, the service interruption caused by user cross-room movement is an important problem, and we propose a double-area-positioning based cross-room switch solution. An experimental platform demonstrates the RDM-deployed VLC network, and validates the performance of the presented switch mechanism.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.5
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• pp.1317-1340
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• 2024

With the rapid development of information technology, people's demands on precise indoor positioning are increasing. Wireless sensor network, as the most commonly used indoor positioning sensor, performs a vital part for precise indoor positioning. However, in indoor positioning, obstacles and other uncontrollable factors make the localization precision not very accurate. Ultra-wide band (UWB) can achieve high precision centimeter-level positioning capability. Inertial navigation system (INS), which is a totally independent system of guidance, has high positioning accuracy. The combination of UWB and INS can not only decrease the impact of non-line-of-sight (NLOS) on localization, but also solve the accumulated error problem of inertial navigation system. In the paper, a fused UWB and INS positioning method is presented. The UWB data is firstly clustered using the Fuzzy C-means (FCM). And the Z hypothesis testing is proposed to determine whether there is a NLOS distance on a link where a beacon node is located. If there is, then the beacon node is removed, and conversely used to localize the mobile node using Least Squares localization. When the number of remaining beacon nodes is less than three, a robust extended Kalman filter with M-estimation would be utilized for localizing mobile nodes. The UWB is merged with the INS data by using the extended Kalman filter to acquire the final location estimate. Simulation and experimental results indicate that the proposed method has superior localization precision in comparison with the current algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5C
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• pp.472-478
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• 2010

In the environment of wireless communication system of IEEE 802.15.3a UWB standard, the angle of arrival(AOA) estimation technique for the indoor wireless positioning algorithms, based on the AOA parameter estimation which fits well for the wireless communication channel and shows high estimation accuracy, is proposed. After the UWB signal model, based on the IEEE 802.1.3a standard, is constructed, the average weighted MUSIC technique is proposed, which shows better estimation accuracy than those of conventional estimation technique. Through the simulation studies, the environment of the indoor wireless positioning system including the IEEE 802.15.3a channel is configured and we demonstrate better estimation results by the proposed AOA estimation technique than those from the conventional method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2382-2388
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• 2014

To provide network reliability in indoor wireless communication systems, we should resolve the problem of unexpected network failure rapidly. In this paper, we propose an adaptive resource management (ARM) scheme to support seamless connectivity to users. In consideration of system throughput and user fairness simultaneously, the ARM scheme adaptively determines the set of healing channels, and performs scheduling and power allocation iteratively based on a constrained non-convex optimization technique. Through intensive simulations, we demonstrate the superior performance results of the proposed ARM scheme in terms of the average cell capacity and user fairness.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.872-878
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• 2003

In this paper, we developed a simulator which can generate the polarization waves for the indoor wireless communications based on three dimensional ray tracing technique and verified the simulation results comparing with the measured data in indoor wireless propagation environments. Using the developed simulator, we analyzed the channel characteristic and polarization diversity reception characteristic for the vertical, horizontal and circularly polarized waves. From the analysis results, in the case of using circularly polarized wave it can be clearly seen that the multipath fading is markedly reduced compared to the vertical and horizontal polarized waves due to the reception characteristic of removing the odd time reflected waves.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.586-591
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• 2015

In recent years, along with the rapid development of LED technology, indoor positioning systems based on visible light communication (VLC) have been researched. In this paper, we propose an accurate indoor positioning method using white-light LEDs and a dual image sensor. Indoor LED lights are located at the ceiling in a room and broadcast information on their positions using VLC technology. A mobile device with a dual image sensor receives LED position information by VLC and estimates its position and azimuth angle. Simulation and experimental results are given to show the performance of the proposed indoor positioning system.

• Journal of electromagnetic engineering and science
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• v.10 no.4
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• pp.263-269
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• 2010

Multiple input multiple output (MIMO) has been considered one of the key enablers of broadband wireless communications. The indoor environment is known to be favorable to ensure both high rank property and high signal-to-interference/noise ratio (SINR) to fully exploit MIMO spatial multiplexing (SM) gain. In this paper, we describe several practical deployment cases where repeater links (or relay links), such as those present with an indoor distributed antenna system (DAS), can act as keyholes to degenerate the rank property of MIMO communications. In this case, we cannot exploit MIMO SM gain in indoor environment. We propose a novel MIMO communication scheme which uses simple converter in the devices in repeater links to resolve the rank degeneration issue and to ensure MIMO SM gain in highly MIMO-favorable indoor environment. MIMO SM is possible over the indoor DAS with single cable line through use of simple converters, which enables practical deployment in real fields.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3A
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• pp.157-165
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• 2003

The purpose of this paper is to analyze the performance requirements of wireless systems on ultra wide band, which is set by FCC(Federal Communications Commission). Normally the calculation of performance requirements is used in the standard form of each communication systems, but there is no standard in the wireless systems on Ultra WideBand. Therefore, I derive each system parameters through the analysis of new system performance on the basis of the method of Indoor Communication Systems. Additionally, I compare the conditions that are given by FCC with resolution of the performance by domestic law.

• Journal of Sensor Science and Technology
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• v.23 no.1
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• pp.1-6
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• 2014

In many medical image devices, dc noise often prevents normal diagnosis. In wireless capsule endoscopy systems, multipath fading through indoor wireless links induces inter-symbol interference (ISI) and indoor electric devices generate impulsive noise in the received signal. Moreover, dc noise, ISI, and impulsive noise are also found in optical fiber communication that can be used in remote medical diagnosis. In this paper, a blind signal processing method based on the biased probability density functions of constant modulus error that is robust to those problems that can cause error propagation in decision feedback (DF) methods is presented. Based on this property of robustness to error propagation, a DF version of the method is proposed. In the simulation for the impulse response of optical fiber channels having slowly varying dc noise and impulsive noise, the proposed DF method yields a performance enhancement of approximately 10 dB in mean squared error over its linear counterpart.

• ETRI Journal
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• v.34 no.3
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• pp.319-329
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• 2012

Closed-loop transmit diversity is considered an important technique for improving the link budget in the third generation and future wireless communication standards. This paper proposes several transmit diversity algorithms suitable for small wireless terminals and presents performance assessment in terms of average signal-to-noise ratio (SNR) and outage improvement, convergence, and complexity of operations. The algorithms presented herein are verified using data from measured indoor channels with variable antenna spacing and the results explained using measured radiation patterns for a two-element array. It is shown that for a two-element array, the best among the proposed techniques provides SNR improvement of about 3 dB in a tightly spaced array (inter-element spacing of 0.1 wavelength at 2 GHz) typical of small wireless devices. Additionally, these techniques are shown to perform significantly better than a single antenna device in an indoor channel considering realistic values of latency and propagation errors.