• Korean Journal of Remote Sensing
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• v.17 no.3
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• pp.243-251
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• 2001

GPS is one of today's most widely used surveying techniques. But, users can't acquire an enough accuracy in applications of the navigation or geodesy by the GPS positioning technique because of the effects of the ionosphere and troposphere. The solution of these restrictions in the DGPS technique that is to eliminate the common errors and can achieve a high accuracy. Although of sufficient density for good DGPS, accuracy of positioning is just not dense enough to provide complete coverage for real-time positioning, because distances between base and rover is short. In this paper, we suggest Realtime Long-Distance Transmission Method of DGPS Error Correction Signal, which consist of TCP, UDP and IP, which allows a user to increase the distance at which the rover receiver is located from the base, due to radio modem.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.6
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• pp.211-223
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• 2018

Mobile relay systems have been adopted by $4^{th}$ generation mobile systems as an alternative method to extend cell coverage as well as to enhance the system throughput at cell-edges. In order to achieve such performance gains, the mobile relay systems require path selection and resource allocation schemes that are specifically designed for these systems which make use of additional radio resources not needed in single-hop systems. This paper proposes an integrated path selection and resource allocation scheme for LTE-Advanced relay systems using collaborative communication. We first define the problem of maximizing the downlink throughput of LTE-Advanced relay systems using collaborative communication and transform it into a multi-dimensional multi-choice backpacking problem. The proposed Lagrange multiplier-based heuristic algorithm is then applied to derive the approximate solution to the maximization problem. It is shown through simulations that the approximate solution obtained by the proposed scheme can achieve a near-optimal performance.

• Journal of Advanced Navigation Technology
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• v.23 no.1
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• pp.90-96
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• 2019

LPWA is a cost-effective and time-saving technology with wide coverage. However, the LPWA is an ISM band that uses UHF radio waves, and its performance is very poor indoors because of its strong linearity. But, because of the possibility of achieving high performance compared to other communication in the room, this paper has studied the indoor communication performance by applying LoRa in LPWA technologies. After installing the data receiving module on the 4th floor, the transmission module was placed at the end of the building from the same floor to the 1st floor, and the data was collected. As a results, it installed on the 1st floor can be collected data with 98 ~ 99% probability, and the lowest RSSI is about -116dBm. Thus, considering the specification of LoRa with a maximum reception sensitivity -136dBm when the spreading factor is 12, the application of LPWA in the industrial field can be fully considered.

• Korean Journal of Occupational Health Nursing
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• v.28 no.4
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• pp.271-284
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• 2019

Purpose: This study aimed to examine the process from occurrence of a hospital nurse's suicide to workers' compensation approval, responses of the parties involved, issues debated during approval deliberations, and significant policy changes resulting from the incident. Methods: We conducted in-depth interviews with involved parties and collected various documents, including newspaper articles, forum proceedings, and the agency report on determination of workers' compensation. Content analysis was performed on the collected data. Results: A Joint Task Force continuously reported its progress and findings through mass media such as newspaper, radio, and TV. These activities exerted pressure on a government agency to conduct an occupational disease review and significantly impacted the workers' compensation approval. The agency recognized associations between the hospital's inadequate nurse training and the suicide but did not confirm the excessive overtime and workplace harassment experienced by the nurse as causes of the suicide. This case's media coverage and impact resulted in a law prohibiting workplace harassment and a hospital system dedicating at least one nurse to training activities. Conclusions: This incident had a significant social impact as the first case of workers' compensation approval for a hospital nurse's suicide. However, the case produced no structural changes in nurses' working conditions such as heavy workloads.

• The KIPS Transactions:PartC
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• v.9C no.3
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• pp.385-398
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• 2002

To accommodate the increasing number of mobile terminals in the limited radio spectrum, wireless systems have been designed as micro/picocellular architectures for a higher capacity. This reduced coverage area of a cell has caused a higher rate of hand-off events, and the hand-off technology for efficient process becomes a necessity to provide a stable service. Population-based Bandwidth Reservation(PBR) Scheme is proposed to provide prioritized handling for hand-off calls by dynamically adjusting the amount of reserved bandwidth of a cell according to the amount of cellular traffic in its neighboring cells. We analyze the performance of the PBR scheme according to the changes of a fractional parameter, f, which is the ratio of request reservation to the total amount of bandwidth units required for hand-off calls that will occur for the next period. The vague of this parameter, f should be determined based on QoS(Quality of Service) requirement. To meet the requirement the value of Parameter(f) must be able to be adjusted dynamically according to the changing traffic conditions. The best value of f can be determined by a function of the average speed of mobile stations, average call duration, cell size, and so on. This paper considers the average call duration and the cell size according to the speed of mobile stations. Although some difference exists as per speed, in the range of 0.4 $\leq$ f $\leq$ 0.6, Blocking Probability, Dropping Probability and Utilization show the best values.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10B
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• pp.639-647
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• 2005

When a DEV associates with an existing WPAN, the PNC checks the capabilities of the new DEV to see if it is more capable to be the PNC of the piconet based on the criteria defined in the IEEE Std 802.15. If the new DEV is more capable and the current security policies allow it, then the PNC has the option of handing over control of the piconet to the DEV that has just joined. And, If the PNC is shutting down or wants to leave the WPAN, it also uses the handover process to give control to another DEV in the piconet. However, IEEE 802.15.3 checks only DEV capability information for more PNC capable. For PNC selection, it should consider the radio coverage of new PNC capable DEVs. So, we propose the method of PNC selection with accessibility check. This method manages PNC candidate list in the current piconet. In this paper, we analyze accessibility problems for PNC selection in section 2. In section 3, we explain CI(Configuration Inquiry) process which is proposed by Sony Corporation and propose PCI(PNC Candidate Inquiry) process. Also, we perform numerical analysis to compare PCI process with CI process in section 4. Finally, we conclude in section 5.

• Journal of Advanced Navigation Technology
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• v.22 no.2
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• pp.76-83
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• 2018

In order to prevent overusing the fishing gear and to reduce discarded fishing gear, there is a need for a technique that can efficiently transmit the information including the type and location of the fishing gear and the user's real name to the fishing boat and the control center using IoT-based communication. In order to do this, it is necessary to be able to confirm the position information of a plurality of buoys that can be identified by the base stations on the land. In this paper, in order to service the maritime IoT communication system, we calculate the link budget between the land base station and the targets on the sea to derive the service coverage. To design a marine IoT radio network for building a fishing gear monitoring system, we calculate link budget for wireless service optimization at sea for NB-IoT using 1.8 GHz frequency band and LoRa service using 900 MHz frequency band. In addition, the link budget between the land base station and buoy, the link budget between the land base station and fishing boat are calculated and the results are analyzed.