• The Journal of Korean Association of Computer Education
• /
• v.15 no.5
• /
• pp.55-62
• /
• 2012

With the development of mobile communications and Internet technology, there is a strong need to provide seamless and fast connectivity for roaming devices. Generally, the mobile host (MH) may have several available networks when entering a new wireless area. However, the standard of decision for user's internet connection is provided only the subsystem identification (SSID) and signal strength of access point (AP). These two standards could not enough to decide optimal AP to the MH. Therefore, to decide the optimal AP, more information is needed. In this paper, we present additional information such as status of MH, capacity, current load, and depth of network hierarchy, by router advertisement message at layer 3. Also, we proposed decision engine (DE) on the MH that analyzes APs and decides the optimal AP automatically by AP's status information. For the MH, wireless connection period is increased, the power consumption is decreased, and the signaling overhead is reduced. For AP and router, the load balancing is provided and the network topology can also be more efficient.

• Journal of Korea Multimedia Society
• /
• v.15 no.9
• /
• pp.1112-1125
• /
• 2012

To realize LBS (Location Based Service), typically GPS is mostly used. However, this system can be only used in out-sides. Furthermore, the use of the GPS in sensor networks is not efficient due to the low power consumption. Hence, we propose methods for the location positioning which is runnable at indoor in this paper. The proposed methods elaborate the location positioning system via applying K-NN(K-Nearest Neighbour) Algorithm with its intermediate values based on IEEE 802.15.4 technology; which is mostly used for the sensor networks. Logically the accuracy of the location positioning is proportional to the number of sampling sensor nodes' RSS according to the K-NN. By the way, numerous sampling uses a lot of sensor networks' resources. In order to reduce the number of samplings, we, instead, attempt to use the intermediate values of K-NN's signal boundaries, so that our proposed methods are able to positioning almost two times as accurate as the general ways of K-NN's result.

• Journal of Digital Convergence
• /
• v.12 no.11
• /
• pp.273-279
• /
• 2014

In this paper, we propose a novel algorithm for three dimensional positioning system and implement a system over indoor wireless channel. A commercial modules are used for mobile and fixed nodes which are product of German company Nanotron Co. This module adopts chirp spread spreading scheme as modulation method to improve the ranging resolution and the module satisfies the IEEE standard 802.15.4a. The distance computation is based on received signal strength(RSS) levels and trilateration method. A testbed was set up to measure and compare the positioning estimation error of the proposed algorithm. The experiments results showed that the accuracy of location estimation was sufficiently good as much as 1m distance error in a wireless environment in an office building.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39C no.11
• /
• pp.1216-1223
• /
• 2014

Internet traffic is rapidly increasing due to the spread of personal smart devices and the demand for multimedia contents. When designing a large ship such as cruise, network architecture is also considered which supports various IT services in a maritime environment similar to the ground environment. In this paper, we consider wireless P2P (peer-to-peer) communication for efficient multimedia content sharing and propose novel handover scheme for efficient download service. The proposed handover method shows that it can improve the download symbol rates for handover in a wireless P2P system considering the signal strength and quality of peers as well. The proposed system is expected to provide efficient contents distribution and reliable communication in the ship-area-network (SAN).

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.9
• /
• pp.1060-1068
• /
• 2016

The range-free localization using connectivity information has problems of mobile tracking. This paper proposes two Bayesian filter-based mobile tracking algorithms considering a propagation scenario. Kalman and Markov Chain Monte Carlo (MCMC) particle filters are applied according to linearity of two measurement models. Measurement models of the Kalman and MCMC particle filter-based algorithms respectively are defined as connectivity between mobiles, information fusion of connectivity information and received signal strength (RSS) from neighbors within one-hop. To perform the accurate simulation, we consider a real indoor map of shopping mall and degree of radio irregularity (DOI) model. According to obstacles between mobiles, we assume two types of DOIs. We show the superiority of the proposed algorithm over existing range-free algorithms through MATLAB simulations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2010.05a
• /
• pp.411-413
• /
• 2010

The wireless AP positioning system is under active progress regarding research and commercialization due to its merit of being able to overcome the representing demerits of existing GPS positioning, which are signal distortion and poor signal reception. This system's feature is to collect AP information distributed throughout the real world, store it on database, and execute positioning by comparing with searched AP information. The positioning process uses collected data, whereas comparison of database data uses the fingerprinting method. The fingerprinting method is a probabilistic modeling method that acquires as much of the data collected from one location upon database composition, to store the value's average value and use it in positioning. Yet, using the average value may contain the probability of errors. Such errors are fatal weaknesses for services based on the background of accurate positioning. This paper deals with the characteristics and problems of the previously used wireless AP positioning system, and proposes measures of using AP information for outdoor positioning in order to solve the aforementioned problems.

• The KIPS Transactions:PartA
• /
• v.16A no.5
• /
• pp.381-388
• /
• 2009

The spread of wireless Internet technology development and applications with location information in the form of location-based services are becoming more diverse. In particular, where you recognize the location of objects such as people and things and to provide valuable services based on the ubiquitous and location-based services are emerging as an important service. The collision between the vehicle position measurement in this thesis and offers related service system. Used in the proposed system, the GPS PACKET with information about the location and time of collision for the vehicle crash, the vehicle consists of a NodeID. Cause a conflict between these data at the vehicle, the vehicle through the gateway from the server to decide whether to go on to determine that an emergency situation, Emergency Center, the location information and giving information about whether the conflict is measured. Also, for such an emergency, such as a family on the outside of the wireless terminal related to Wireless (PDA, Phone) is to let me know. The server to want to save the crash information to the database of configuration. Additionally, the proposed U-LBS system to verify the validity of the experiment was performed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2014.05a
• /
• pp.574-577
• /
• 2014

Multimedia contents sharing services based on DLNA (Digital Living Network Alliance) technology such as Allshare or Smartshare in wireless home networks is widely adapted in Korea. However, the characteristics of the wireless network - frequently fluctuated bandwidth and signal strength could degrade the quality perceived by users. To minimize the impact of the challenge there are active researches in dynamic adaptive streaming. This paper proposes a dynamic adaptive streaming approach designed in a wireless network taking into account of the specifications of the user device such as resolution and processor. We modify the Kalman filter considering the characteristics of the device and demonstrate that the proposed approach determines Bit Rate using the modified filter.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2006.05a
• /
• pp.1385-1388
• /
• 2006

위치기반서비스는 기본적으로 사용자의 위치를 파악해야 한다. 측위방법은 옥외용과 옥내용으로 구분되며, 옥외용에는 GPS 방법, 이동통신망을 이용한 방법, GPS와 이동통신망을 복합적으로 활용한 방법이 있고, 옥내용에는 적외선을 이용한 방법, 초음파를 이용한 ActiveBat과 Cricket, RF 신호를 이용한 RADAR가 있다. 기존의 옥외용 측위방법은 옥내에서는 사용이 제한되고, 기존의 옥내용 측위방법은 특수한 환경을 꾸며주어야 하는 단점이 있다. 본 논문에서는 이러한 단점을 보완한 방법으로 GPS 수신모듈과 무선LAN용 AP의 신호의 세기를 이용하여 사용자의 위치를 판단하는 옥내외 통합 측위시스템을 소개한다. 검증을 위해 제안하는 시스템을 구현해 보았으며, 실험 결과로 성능평가를 한다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.2 no.2
• /
• pp.85-90
• /
• 1991

군사장비에 대한 EMI문제는 2차 세계대전 이후 전자장비에 대한 의존도가 높아짐에 따라 크게 변화하였다. 2차 세계대전 초기에는 주로 항공기의 엔진점화장치에서 발생되는 3~30MHz 대역의 무선주 파수간섭(RFI)이 통신장비에 문제가 되었으며 간섭현상도 그다지 심각하지 않았다. 그러나 전자공학의 급 속한 발전에 따라 고성능 통신장비 및 레이다가 등장하였으며 각종 전자장비도 고출력화, 고밀도화됨에 따 라 장비자체에서 방사되는 전자파잡음의 세기가 증가하게 되었다. 이에 반해 체계(System)탑재 전자장비 들이 점차 마이크로프로세서화 됨에 따라 제어신호의 수준은 더 낮아져서 전자파간섭에 더욱 취약하게 되 었다. 또한 현대의 전장(Battle Field)은 수많은 전기/전자장비가 동시에 운용됨에 따라 발생되는 전자파로 인해 더욱 복잡한 전자파환경이 형성된다.