• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.810-815
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• 2013

In case Wi-Fi network based First responder's position tracking system is used, range measurement must be generated from RSSI finger print database. However, it is impossible to build up finger print database and to perform rescue operation at same time in the scene of rescue. In this paper, improvised Wi-Fi network without finger print database and pedestrian dead reckoning based first responders tracking system is proposed.

• Journal of Digital Contents Society
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• v.13 no.4
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• pp.477-482
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• 2012

The mVoIP service is the technology which focuses on the wireless data service as the IP network having the transmission rate of 100 Mbps classes on the high-speed middle of movement through the WiFi, WiBro and 3G mobile radio communication network, and etc. and is developed. Since 2010, the mVoIP (mobile VoIP) service shows the rapid growth due to 4G-LTE service seriously disclosed from July with the Smart phone and 2,011 it begins to be rapidly popularized. In this research, additionally the mVoIP service industry activation plan is presented with the trends of technology development including the chip-set/module/terminal, etc. based upon local and foreign market trend searchlight through the market demand analysis. The mVoIP service downloads App to the mobile apparatus and or can provide the service as the software through the WiFi network. Therefore, the change which is large in the products development aspect is to be have no. Expected to is being provided as the added service in the case of 4G-LTE as a matter of course, the service deployment where it is based on the market principle and demand needs is needed.

• Journal of the Korea Society of Computer and Information
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• v.20 no.3
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• pp.1-8
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• 2015

The most used smart set-top box in home driven by the Android OS and based on Wi-Fi technology has to ensure nothing wrong with the Wi-Fi service regardless of the various user's installation environment. The direction test method about the nondirectional of the Wi-Fi doesn't be determined as the standard and each manufacturers devise the their own test methods and conduct the tests. In this paper, we created the 720 test cases considering 2 components of upload & download, the 10 elements of the vertical angle and the 36 elements of the horizontal angle looking at the wireless router in order to verify omni-directional Wi-Fi capability. In reality, from viewpoint in terms of cost and time constraint, it is difficult to test all the test cases. Therefore, we decided to reduce test cases by applying Pair-wise testing technique which is one of combinational testing techniques based on ISO / IEC 29119-4. And we obtained the test cases in which the Pair-wise technique was applied by Allpairs tool which output test cases automatically and conducted the test. It could be confirmed that the proposed technique shortened 48.61% of the time to be spent in progressing the existing test cases and that the trace about the part in which the problem was generated with the result of the simplified test case was possible enough.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.12
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• pp.2272-2293
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• 2011

Communication technology of future networks is predicted to provide a large variety of services including WiFi service in vehicular network. In this paper, we assume that vehicles are embedded with WiMAX antenna and in-vehicle terminals receive WiMAX traffic through WiFi interface. This assumption will impose severe performance degradation due to interference among mobile BSSs when WiFi access points (APs) are densely located. Existing interference avoidance techniques cannot properly resolve the above problems and do not cope with dynamically moving vehicular scenario since they focus only on the fixed network topology. In this paper, we propose a mobility-aware interference avoidance scheme for WiFi services. The proposed scheme computes the interference duration by exploiting mobility vector and location information of neighboring APs. If the interference duration is not negligible, our scheme searches for another channel in order to avoid interference. However, if the interference duration is negligible, our scheme continues to use the channel to reduce switching overhead. To measure the effectiveness of the proposed scheme against other existing techniques, we evaluated performance by using OPNET simulator. Through the simulation, we obtained about 60% reduction in the maximum interference frequency and about 67% improvement in throughput. Furthermore, our scheme provides fair channel usage.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.383-384
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• 2012

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.168-171
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• 2016

In recent years, indoor localization in Wi-Fi environment has been researched for its location determining capability. The fingerprint and RF propagation models has been the main approach in determining indoor positioning. With the use of fingerprint, a low-cost, versatile localization system can be achieved without the use of external hardware. However, only a few research have been made on virtual access points (VAPs) among indoor localization models. In this paper, the idea of indoor localization system using fingerprint with the addition of VAP in Wi-Fi environment is discussed. The idea is to virtually add APs in the existing indoor Wi-Fi system, this would mean additional virtually APs in the network. The experiments of the proposed algorithm shows the positive results when 2VAPs are used compared with only APs. A combination of 3APs and 2VAPs had the lowest average error in all 4 scenarios with 3.99 meters.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.05a
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• pp.73-75
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• 2018

LoRaWan(Long Range Wide Area Network)은 저전력, 장거리 특성을 가진 무선 통신기술로 그 특성상 스마트 시티(Smart City), IoT(Internet of Things) 등에 각광받고 있다. 또한 LoRaWan은 Chirp 신호 특성에 의해 실외 삼각측량에 따른 사용자 위치 추정 기술을 제공한다. 본 논문에서는 이러한 LoRaWan의 특성에 더해 Wi-Fi 지문 정보를 활용하여 위치 추정 정확도를 개선하고 또한 이웃 Wi-Fi 단말들, 가령 스마트폰 등의 위치 정보를 LoraWan 게이트웨이와 통신하여 최종적으로 서버에서 측위 할 수 있는 시스템을 제안한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.163-164
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• 2009

최근 감시카메라의 사용률이 증가하고 있다. 개인 사업체, 전문 감시업체, 일반 기업 및 공공기관 등 감시카메라는 폭넓게 사용된다. 하지만 현재 설치된 감시카메라는 녹화된 감시영상이나 카메라 컨트롤을 관리자가 언제 어디서나 확인하고 조절할 수 없다는 단점이 있다. 이러한 단점을 해결하기 위해 TCP/IP기반의 네트워크에서 PDA로 Wi-Fi를 이용하여 접속한 후 감시카메라를 제어하거나 영상을 확인하는 방법을 제안하고 구현하였다. 제안하는 시스템은 서버 컴퓨터는 카메라의 영상을 받고 팬틸트 컨트롤을 하게한다. 클라이언트 컴퓨터는 PC와 PDA를 이용하여 서버에 접속한 뒤 실시간으로 영상을 받아오고 카메라 팬틸트를 컨트롤 한다. 본 논문에서 제안한 내용은 Wi-Fi가 사용가능한 곳에 있는 사용자가 언제 어디서나 감시카메라의 영상을 보고 컨트롤 하는데 유용할 것이다.

• Journal of Communications and Networks
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• v.8 no.4
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• pp.369-377
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• 2006

Recently, the metropolitan area network (MAN) has attracted much attention in telecommunication research and has emerged as one of the most important research topics in the community. Several standards representing the first step for developing metropolitan networks have been published; IEEE 802.16 (WiMAX) has taken a relevant role in reaching the goal of realizing a full-service network all over a urban and suburban area. At the same time, the wireless local area networks (WLAN) have been widely used for in-home or short range communications, mainly basing on the IEEE 802.11 (WiFi) standard. A consequence is the increasing interest in interworking technology, that allows an interconnection between different standards by maintaining certain properties, mainly in terms of quality of service (QoS). One of the major issues is to design bridging devices capable of transparently interconnect different wireless technologies. In this paper, we propose two interconnection bridging solutions between WiMAX and WiFi links; the first is more based on the concept of maintaining a certain end-to-end QoS level independently from the wireless technologies used. The second method is more devoted to the reduction of the implementation complexity at the cost of no QoS assurance. The performance of the two methods are compared by resorting to computer simulations showing the advantages of each one technique.

• Spatial Information Research
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• v.23 no.3
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• pp.1-10
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• 2015

Due to recent improvement of various sensor technologies, indoor positioning becomes available. However, Indoor positioning technologies by Wi-Fi radio map and acceleration sensor and digital campus still have a certain level of errors and a number of researches have been done to increase the positioning accuracy of the indoor positioning. If we could provide a room level accuracy, indoor location based services with current indoor positioning methods such as Wi-Fi radio map and acceleration sensors would be possible. In this paper, we propose an indoor map matching method to provide a room level accuracy based on hidden markov model.