• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2011-2018
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• 2009

The international society under the internet technology have been declining boundaries of the global economy. After this step, a social revolution will be happen from the ubiquitous technology which gives objects intelligence to serve people. And then it is expected that every part of a city competitive power is defined by both in quality and in quantity of the ubiquitous information unit in the future. On this score, now each nation is trying to set relative services and broadband networks to lead the ubiquitous industry. Therefore this paper analyzed about the progress and prospect of a local U-city plan in our nation. And than we propose a method of configurating broadband self-communication network on the base of cost and utilization Especially we propose a new city development model which use U-city and self-communication network to improve a city competitive power.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.3
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• pp.15-23
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• 2020

As the IoT industry expands, various application services based on location information of devices are released. In order to transmit the location information, various wireless communication technologies such as Bluetooth and Wi-Fi are used. However, these technologies have limited coverage, and cellular networks with relatively wide coverage have the disadvantage of paying for use. In this paper, we implemented our own location information system using LoRa, a low power long distance wireless communication technology. As a result, no cost is incurred and it has relatively wider coverage than other wireless communication technologies using LoRa technology. The implementation system enables LoRa communication based on IPv6 using CoAP and 6LoWPAN, and enables multiple devices to interwork with the existing Internet environment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.2
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• pp.72-78
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• 2011

Localization information of an object can be a very useful element for many application areas. Presently, GPS is typically used for it, but many researches on the wireless localization technology are going on recently actively using mobile communication network, wireless sensor network, and ad hoc network in order to overcome the limitations of the GPS such as indoor, cost, power consumption, and etc. Therefore, this article surveys the most representative wireless localization techniques, which can be deployed in the wireless networks, and their principles and performances are analyzed based on the researched papers. In a conclusion, selection of a localization technique should consider the key design elements to a given application from the design elements such as localization environment, accuracy, time to fix, computation amount, implementation ease, and etc.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.293-298
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• 2010

The key of USN(Ubiquitous Sensor Network) technology is low power wireless communication technology and proper resource allocation technology for efficient routing. The distinguished resource allocation method is needed for efficient routing in sensor network. To solve this problems, we propose an algorithm that can be adopted in USN with making up for weak points of PQ and WRR in this paper. The proposed algorithm produces the control discipline by the fuzzy theory to dynamically assign the weight of WRR scheduler with checking the Queue status of each class in sensor network. From simulation results, the proposed algorithm improves the packet loss rate of the EF class traffic to 6.5% by comparison with WRR scheduling method and that of the AF4 class traffic to 45% by comparison with PQ scheduling method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.207-214
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• 2011

In this paper, using Zigbee-based wireless sensor networks and Lego MindStorms NXT robot, a remote monitoring and navigation system for mobile robot has been developed. Mobile robot can estimate its position using encoder values of its motor, but due to the existing friction and shortage of motor power etc., error occurs. To fix this problem and obtain more accurate position of mobile robot, a ultrasound module on wireless sensor networks has been used in this paper. To overcome disadvantages of ultrasound which include straightforwardness and narrow detection coverage, we rotate moving node attached to mobile robot by $360^{\circ}$ to measure each distance from four fixed nodes. Then location of mobile robot is estimated by triangulation using measured distance values. In addition, images are sent via a network using a USB Web camera to smart phone. On smart phones we can see location of robot, and images around places where robot navigates. And remote monitoring and navigation is possible by just clicking points at the map on smart phones.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.8
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• pp.3366-3383
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• 2020

The Poisson point process (PPP) is widely used in wireless network modeling and performance analysis because it can provide tractable results for heterogeneous cellular networks (HetNets) analysis. However, it cannot accurately reflect the spatial distribution characteristics of the actual base stations (BSs). Considering the fact that the distribution of macro base stations (MBSs) is exclusive, the deployment of MBSs is modeled by the Matérn hard-core point process (MHCPP), and the deployment of pico base stations (PBSs) is modeled by PPP. This paper studies the performance of multiantenna HetNets and improves the energy efficiency (EE) of HetNets by optimizing the transmit power of PBSs. We use a simple approximate method to study the signal-to-interference ratio (SIR) distribution in two-tier MHCPP-PPP HetNets and derive the coverage probability, average data rate and EE of HetNets. Then, an optimization algorithm is proposed to improve the EE of HetNets. Finally, three transmission technologies are simulated and analyzed. The results show that multiantenna transmission has better system performance than single antenna transmission and that selecting the appropriate transmit power for a PBS can effectively improve the EE of the system. In addition, two-tier MHCPP-PPP HetNets have higher EE than two-tier PPP-PPP HetNets.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4760-4765
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• 2010

Time out-medium access control (T-MAC) protocol is one of the well-known MAC protocols designed for wireless sensor networks (WSN), and is proposed to enhance the poor performance of the S-MAC protocol. In this paper, we are reviewed about security vulnerability in T-MAC, and analyzed the power which is consumed at each stage of T-MAC protocol according to vulnerability of denial of service (DoS) and replay problem. From our analytical results, it can be considered the need of power efficient authentication scheme which provides the reliability, efficiency, and security for a general T-MAC communication. This is the case study of possible DoS vulnerability and its power consumption in T-MAC.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.1038-1041
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• 2009

Wireless sensor network with wireless sensor nodes which equipped with temperature, humidity, illumination, or soil sensor etc, get a natural environment information and analyze and utilized variety way.these network consist of a short distance wireless communication and multi-hop techniques with multiple nodes equipped low-power wireless transceivers. so the characteristic of the data collected through the wireless sensor network is obtained from compact nodes within a limited range. However, to get a data from the wireless sensor nodes scattered in a wide range, this network needs a wireless transceiver that consumes many power or a lot of intermediate nodes. then, merit of low cost and low electrical energy decrease. To solve this problem, this paper offers environment monitoring system using autonomous mobile robot that collect data from groups of each sensor networks scattered widely.

• ETRI Journal
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• v.40 no.3
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• pp.318-329
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• 2018

Femtocell (FC) technology envisaged as a cost-effective approach to attain better indoor coverage of mobile voice and data service. Deployment of FCs over macrocell forms a heterogeneous network. In urban areas, the key factor limits the successful deployment of FCs is inter-cell interference (ICI), which severely affects the performance of victim users. Autonomous FC transmission power setting is one straightforward way for coordinating ICI in the downlink. Application of intelligent control using soft computing techniques has not yet explored well for wireless networks. In this work, autonomous FC transmission power setting strategy using Adaptive Neuro Fuzzy Inference System is proposed. The main advantage of the proposed method is zero signaling overhead, reduced computational complexity and bare minimum delay in performing power setting of FC base station because only the periodic channel measurement reports fed back by the user equipment are needed. System level simulation results validate the effectiveness of the proposed method by providing much better throughput, even under high interference activation scenario and cell edge users can be prevented from going outage.

• International Journal of Internet, Broadcasting and Communication
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• v.10 no.2
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• pp.7-12
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• 2018

The spread of IoT (Internet of Things) technology that connects objects based on wired / wireless networks is accelerating, and IoT-based smart home technology that constitutes a super connected network connecting sensors and home appliances existing inside and outside the home is getting popular. In addition, demand for alternative energy technologies such as photovoltaic power generation is rapidly increasing due to rapid increase of consumption of energy resources. Recently, small solar power systems for general households as well as large solar power systems for installation in large buildings are being introduced, but they are effectively implemented due to limitations of small solar panels and lack of power management technology. In this paper, we have studied smart home structure and IoT / IoL device discovery algorithm for energy harvesting system based on photovoltaic power generation, It is possible to construct an efficient smart home system for device control.