• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.9
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• pp.4408-4428
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• 2019

Due to the rapid advancement in smart phones, numerous new specifications are developed for variety of applications ranging from health monitoring to navigations and tracking. The word indoor navigation means location identification, however, where GPS signals are not available, accurate indoor localization is a challenging task due to variation in the received signals which directly affect distance estimation process. This paper proposes a hybrid approach which integrates fingerprinting based K-Nearest Neighbors (K-NN) and lateration based MinMax position estimation technique. The novel idea behind this hybrid approach is to use Euclidian distance formulation for distance estimates instead of indoor radio channel modeling which is used to convert the received signal to distance estimates. Due to unpredictable behavior of the received signal, modeling indoor environment for distance estimates is a challenging task which ultimately results in distance estimation error and hence affects position estimation process. Our proposed idea is indoor position estimation technique using Bluetooth enabled smart phones which is independent of the radio channels. Experimental results conclude that, our proposed hybrid approach performs better in terms of mean error compared to Trilateration, MinMax, K-NN, and existing Hybrid approach.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.114-124
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• 2002

In this paper, we proposed the image-based 3D ray tracing indoor propagation model using a patch scattering model for fading analysis of indoor propagation environments. An image-based 3D ray tracing technique is mainly used, which allows the rapid generation of the complex channel impulse response for any given location and polarization of transmitter and receiver. Due to the site specific nature of indoor environment, we took into account the location and the electrical properties of individual walls and objects such as windows, doors and plaster board in our propagation model. Besides, the 3D radiation beam-patterns and polarizations of arbitrary antennas were considered, and using patch scattering model we can consider the change of the polarization due to the scattering from the various indoor objects, like desks, chairs and etc. the are almost impossible to be modeled with the basic image-based ray tracing method. The model will predict the impulse response, the rms delay spread, the fading characteristics of the channel and performances of the polarization diversity schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7B
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• pp.1058-1065
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• 2010

In the recent, the importance of ubiquitous-related technique is increased as many companies and researchers make an effort to create a new service model using ubiquitous computing and network technologies. Especially, the research of indoor location recognition has gained a lot of interest because it is a critical component for supporting ubiquitous services. Nevertheless, the simulation tool for indoor location recognition hardly has studied compared to their importance. In this paper, we propose a Ptolemy-based simulator over UWB channel that provides short-range and high-bandwidth communication. Finally, we conduct experiments using the proposed simulator and analyze the performance of various location recognition algorithms.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.688-697
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• 2008

In this paper, an analysis method for indoor optical wireless channel properties based on photon model is presented for characterization of communication environment. In contrast to radio waves, optical waves have very short wave-lengths and very high frequencies, so that material properties become important. Channel models including diffuse reflections and absorption effects due to material surface textures make conventional electromagnetic wave analysis methods based on ray tracing consume enormous time. To overcome these problems, an analysis method using photon model is presented that approximates light intensity by a density of photons. The photon model ensures that simulation time is within a predictable limit.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.846-849
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• 2008

In recent years there has been growing interest in wireless sensor networks (WSNs) for a variety of indoor applications. In this paper, we present the RSSI-based localization in indoor environments. In order to evaluate the relationship between distance and RSSI, the log-normal path loss shadowing model is used. By tagging users with a sensor node and deploying a number of nodes at fixed position in the building, the RSSI can be used to determine the position of tagged user. This system operates by recording and processing signal strength information at the base stations. It combines Euclidean distance technique with signal strength matrix obtained during real-time measurement to determine the location of user. The experimental results presented the ability of this system to estimate user's location with a accuracy.

• Journal of Korea Society of Digital Industry and Information Management
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• v.16 no.4
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• pp.1-7
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• 2020

Over the past few years, Wi-Fi signal based indoor positioning system (IPS) has been researched extensively because of its low expenses of infrastructure deployment. There are two major aspects of location-related information contained in Wi-Fi signals. One is channel state information (CSI), and one is received signal strength indicator (RSSI). Compared to the RSSI, the CSI has been widely utilized because it is able to reveal fine-grained information related to locations. However, the conventional IPS that employs a single access point (AP) does not exhibit decent performance especially in the environment of non-line-of-sight (NLOS) situations due to the reliability degeneration of signals caused by multipath fading effect. In order to address this problem, in this paper, we propose a novel method that utilizes multiple APs instead of a single AP to enhance the robustness of the IPS. In our proposed method, a hybrid neural network is applied to the CSIs collected from multiple APs. By relying more on the fingerprint constructed by the CSI collected from an AP that is less affected by the NLOS, we find that the performance of the IPS is significantly improved.

• Journal of Advanced Navigation Technology
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• v.25 no.5
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• pp.357-362
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• 2021

UWB(ultra wide band) communication systems employ short pulses to transmit information which spreads the signal energy over a very wide frequency spectrum. Received signal-to-noise power ratio of UWB signals is an important factor in determining the accuracy of a positioning system. As the signal to noise power ratio gets higher, positioning errors decrease since noise becomes less effective. Calculation of signal to noise power ratio as a function of communication distance provides important guidelines for the system design. And the performance of a positioning system also depends heavily on the channel model. As a result of the analysis, it was found that the performance of the received signal to noise power ratio according to the communication distance was better in the LOS channel environment than in the Non LOS(line of sight) channel environment. And as the symbol interval of the preamble signal increases at a specific communication distance, the channel capacity of the UWB system increases.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.216-216
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• 2006

• Journal of information and communication convergence engineering
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• v.5 no.3
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• pp.229-232
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• 2007

This paper investigates on the use of constant-amplitude zero-autocorrelation (CAZAC) sequence for channel estimation in multiple-input multiple-output (MIMO) system over indoor wireless channel. Since the symbol-length of the conventional 4-phase CAZAC sequence is short, there is a limitation to use it for MIMO system in multipath environments. An algorithm which generates longer CAZAC sequences is proposed to overcome that problem. Flexible symbol-length of 4-phase CAZAC sequences can be made by the proposed algorithm. Therefore appropriate symbol-length of CAZAC sequences could be utilized as preambles in accordance with the number of transmit antennas and channel condition. The effect of the number of CAZAC sequences for channel estimation is presented in terms of mean square error (MSE).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.4865-4886
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• 2017

The user experience of practical indoor power line communication (PLC) applications is greatly affected by the system quality-of-service (QoS) criteria. With a general broadcast-and-multi-access (BMA) relay scheme, in this work we investigate the joint source and relay power optimization of the amplify-and-forward (AF) relay systems used under indoor broad-band PLC environments. To achieve both time diversity and spatial diversity from the relay-involved PLC channel, which is time-varying in nature, the source node has been configured to transmit an identical message twice in the first and second signalling phase, respectively. The QoS constrained power allocation problem is not convex, which makes the global optimal solution is computationally intractable. To solve this problem, an alternating optimization (AO) method has been adopted and decomposes this problem into three convex/quasi-convex sub-problems. Simulation results show the fast convergence and short delay of the proposed algorithm under realistic relay-involved PLC channels. Compared with the two-hop and broadcast-and-forward (BF) relay systems, the proposed general relay system meets the same QoS requirement with less network power assumption.