• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.555-557
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• 2003

Location-based services allow consumers to receive services based on their geographic location data. For example, businesses can provide information to find traffic facility, public restaurant, a hospital, and a station based on the consumer’s location at a particular moment. Also, they wish to grasp a accurate location based service in mobile device or PDA. So, this paper shows that presentation service offers a base-map to be overlaid OpenLS (Open Location Services)’s directory service, route determination service, geocode and reverse-geocode service. The presentation service is the portrayal of a map and portrayal of feature as map overlays.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3B
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• pp.577-583
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• 2000

An efficient echo cancellation method, which controls the echo caused from the PSTN, is proposed. In our situation, the PSTN is connected to the mobile subscriber and the base-station which use different bit-rate CVSD(continuously variable slope delta modulation) coders and echo canceller is installed at the location of the base-station. By using the symmetry of the coder pairs. the proposed method shortens the echo pate length and reduces the nonlinear distortion inherent in the coders. And it is implemented in the decoded signal region, so fitted to the general-purpose DSP implementation. We also proposed a echo cancellation method using the combined bit-stream so as to implement without the multipliers onto the VLSI. It has an improved echo cancellation performance by reducing the high frequency noises in the coders. And it has an reduced complexity by reducing the excitation rate of the bit-stream.

• The Journal of the Korea Contents Association
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• v.11 no.9
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• pp.26-44
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• 2011

The Study was carreid out to see whether the intensity of electromagnetic waves in each floor of a building where the sharing base station has been established is harmful to a human body, and to expect the intensity of the waves in the building. The investigate was performed on both of sharing base station either with many scatterers or without any of them. To satisfy the international standard and the domestic TTA standard, rms for each of the electromagnetic wave of every floor in the building with the station was measured from 3 location of 3 heights(1.1m,1.5m, and 1.7m). Max of the measured rsm from the each of the frequencies in the nine location was confirmed to be 48.12%(the rooftop measured value) at most, compared to the human body protection standard. The value was confirmed to satisfy the human body protection standard for each frequency. And the total value of the calculated exposure indexes for each frequency was determined to be more than 7 times lower at most, which was 0.1445, compared to the 1 standard. Since P value in both of 868MHz and 2.14GHz electromagnetic waves intensity for each base station and floor was less than 0.05, it was revealed to be meaningful, and since R-Sq(adj) value showed a value more than 50%, the regression equation was determined to fully absorb the data information. However, although the P value of both of 868MHz and 2.14GHz electromagnetic waves intensities under the integrating terms of the base station data and the floor data was showed to be less than 0,05, since R-Sq(adj) value of 868MHz electromagnetic waves intensity presented a value smaller than 50%(34.15%), it was determined that the 868MHz electromagnetic waves intensity is very much influenced by an environment with a base station. Because the electromagnetic waves intensity of 2.14GHz show R-Sq(adj) value bigger then 50%(51.8%), The regression equation model of 2.14GHz electromagnetic waves intensity was confirmed to be proper. It also turned out not to be effected by the surrounding environment near a building with the base station and the intensity of electromagnetic waves for each floor of such building was expectable by the regression equation.

• Journal of Communications and Networks
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• v.8 no.1
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• pp.85-92
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• 2006

In this paper, we study a wireless cellular network design problem. It consists of selecting the location of the base station controllers and mobile service switching centres, selecting their types, designing the network into a tree-topology, and selecting the link types, while considering the location and the demand of base transceiver stations. We propose a constraint programming model and develop a heuristic combining local search and constraint programming techniques to find very good solutions in a reasonable amount of time for this category of problem. Numerical results show that our approach, on average, improves the results from the literature.

• KIISE Transactions on Computing Practices
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• v.22 no.2
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• pp.101-106
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• 2016

A femtocell network has been attracting attention as a promising solution for providing high data rate transmission over the conventional cellular network in an indoor environment. In this paper, we propose a distributed power control algorithm considering both indoor coverage and data load balancing in the femtocell network. As data traffic varies by time and location according to user distribution, each femto base station suffers from an unbalanced data load, which may degrade network performance. To distribute the data load, the base stations are required to adjust their transmission power dynamically. Since there are a number of base stations in practice, we propose a distributed power control algorithm. In addition, we propose the simple algorithm to detect the faulty base station and to recover coverage. We also explain how to insert a new base station into a deployed network. We present the simulation results to evaluate the proposed algorithms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.1
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• pp.343-364
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• 2021

In the 5G era, the communication networks tend to be ultra-densified, which will improve the accuracy of indoor positioning and further improve the quality of positioning service. In this study, we propose an indoor three-dimensional (3D) dynamic reconstruction fingerprint matching algorithm (DSR-FP) in a 5G ultra-dense network. The first step of the algorithm is to construct a local fingerprint matrix having low-rank characteristics using partial fingerprint data, and then reconstruct the local matrix as a complete fingerprint library using the FPCA reconstruction algorithm. In the second step of the algorithm, a dynamic base station matching strategy is used to screen out the best quality service base stations and multiple sub-optimal service base stations. Then, the fingerprints of the other base station numbers are eliminated from the fingerprint database to simplify the fingerprint database. Finally, the 3D estimated coordinates of the point to be located are obtained through the K-nearest neighbor matching algorithm. The analysis of the simulation results demonstrates that the average relative error between the reconstructed fingerprint database by the DSR-FP algorithm and the original fingerprint database is 1.21%, indicating that the accuracy of the reconstruction fingerprint database is high, and the influence of the location error can be ignored. The positioning error of the DSR-FP algorithm is less than 0.31 m. Furthermore, at the same signal-to-noise ratio, the positioning error of the DSR-FP algorithm is lesser than that of the traditional fingerprint matching algorithm, while its positioning accuracy is higher.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.9
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• pp.2402-2414
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• 1996

Registration is the process by which a base station gets the information of location and status about mobile stations. Registration will become an increasingly important issue in mobile cellular communications, especially in microcellular system with the increase of location updating traffic. Four typesof registration schemes, which are specified in US standard IS-95 and Korean standard TTA-KO-0062, power up registration scheme, power down registration scheme, distance based registration scheme and zone based registration scheme, will be mainly used in the future. In this paper, we derive the combined cost of signaling traffic of paging and registration for various parameters of mobile stations behavior(unencumbered call duration, power up and down rate, velocity, etc.) then we present numerical results for the perfroamnce of four registration schemes. The size of location area is provided for optimal operation.

• Journal of IKEEE
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• v.20 no.1
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• pp.1-8
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• 2016

In this paper, we propose an effective time-of-arrival (TOA)-based localization method with adaptive bias computation in indoor environments. The goal of the localization is to estimate an accurate target's location in wireless localization system. However, in indoor environments, non-line-of-sight (NLOS) errors block the signal propagation between target device and base station. The NLOS errors have significant effects on ranging between two devices for wireless localization. In TOA-based localization, finding the target's location inside the overlapped area in the TOA-circles is difficult. We present an effective localization method using compensated distance with adaptive bias computation. The proposed method is possible for the target's location to estimate an accurate location in the overlapped area using the measured distances with subtracted adaptive bias. Through localization experiments in indoor environments, estimation error is reduced comparing to the conventional localization methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12B
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• pp.1736-1743
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• 2011

In Network Centric Warfare (NCW) environment, having a tactical communication network which provides high data exchange rate is very important. In the process, Korean Army developed Mobile Subscriber Access Point (MSAP) which is based on the commercial Wireless BroadBand (Wibro). MSAP is a vehicle attached base station which provide high data exchange communication environment in a given area. Thus MSAP can provide high data exchange rate and mobility to accomplish missions in the battlefield more effectively. In this paper, we propose an operational strategy of using MSAP to provide tactical communication network in the battlefield. The idea is to find the optimal location point of the MSAP in the operational area where all the troops in the operational area can be supported by the MSAP with a minimum number of MSAP. Since the current Korean Army's basic idea of using MSAP is just distribute this MSAP to each troop, so by applying our strategy we can save MSAP devices for more flexible operation. We will show our strategy's benefits through the mathematical model and the algorithm of the presented problem.

• Journal of the Korea Society of Computer and Information
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• v.29 no.2
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• pp.1-12
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• 2024

Predicting path loss is one of the important factors for wireless network design, such as selecting the installation location of base stations in cellular networks. In the past, path loss values were measured through numerous field tests to determine the optimal installation location of the base station, which has the disadvantage of taking a lot of time to measure. To solve this problem, in this study, we propose a path loss prediction method based on machine learning (ML). In particular, an ensemble learning approach is applied to improve the path loss prediction performance. Bootstrap dataset was utilized to obtain models with different hyperparameter configurations, and the final model was built by ensembling these models. We evaluated and compared the performance of the proposed ensemble-based path loss prediction method with various ML-based methods using publicly available path loss datasets. The experimental results show that the proposed method outperforms the existing methods and can predict the path loss values accurately.