• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.1053-1056
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• 2012

Location information is considered to be of prime importance in Vehicular Ad Hoc NETworks (VANETs) because important decisions are made based on accurate and sound location information. Vehicles exchange their whereabouts in the form of scheduled beacon messages with their neighbors. These messages contain location, speed, time, and lane information etc. In this paper we aim at the location security in VANET and emphasize on the confidentiality and integrity of location information in case of Nonline-of-Sight (NLoS). For location confidentiality we propose a geolock-based mechanism whereas for location integrity we leverage cooperation among neighbors. In case of NLoS, the verifier vehicle asks its one-hop neighbors in an efficient way to verify the claimed location of the node on his behalf. On the basis of trust values and weightage assigned to neighbors, it is decided whether the verification is sound.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.127-128
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• 2009

위치기반 라우팅 프로토콜에서의 기본 가정인 이웃 노드들과의 주기적인 위치정보 교환은 노드의 이동성이 있는 경우, 그 성공률을 보장하기가 어렵다. GPSR[1]에서 제안하고 있는 1-홉 거리에 있는 노드들의 정보를 테이블로 관리하는 방식은 데이터 전달이 없는 지역에서도 주기적인 비콘의 교환으로 불필요한 에너지 소모가 있으며, 노드들의 위치가 변경되었을 때, 비콘 (beacon)을 수신한 시점의 위치정보와 데이터 전달시점의 위치정보의 불일치 가능성을 배제할 수 없다. 따라서, 본 논문에서는 노드의 이동성이 빈번한 환경의 위치기반 라우팅 프로토콜에서 데이터전달시점에 이웃 노드들의 정보를 바탕으로 다음 전송노드를 선택하는 방법을 제안한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.1
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• pp.198-205
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• 2007

In ubiquitous environment a user can be provided with context-aware services based on his or her current location, time, and atmosphere. LBS(Location-Based Services) play an important role for ubiquitous context-aware computing. Because deployment and maintenance of this specialized equipment is costly, many studies have been conducted on positioning using only wireless equipment under a wireless LAN infrastructure. Because a CPS(Cooperative Positioning System) that uses the RSSI (Received Signal Strength Indicator) between mobile equipments is more accurate than beacon based positioning system, it requires great concentration in its applications. This study investigates the relationship between nodes by analyzing a WiPS (Wireless LAN indoor Positioning System), a similar type of CPS, and proposes a improved WiCOPS-d(Wireless Cooperative Positioning System using node density) to increase performance by determining the convergence adjustment factor based on node density.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4B
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• pp.300-308
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• 2012

Many indoor location tracking technologies have been proposed. Generally indoor location tracking using TOA signal is used, there is a weak point that it's difficult to track the location due to obstacles like a refraction, reflection and dispersion of radio wave. In this paper, we apply ETOA(Estimated-TOA) algorithm in NLOS(Non-Line-Of-Sight) environment to solve above problem. In NLOS environment, TOA value between Beacon and Mobile node is predicted by ETOA algorithm and the tracking of indoor location is also possible to identify using two NLOS beacons of three beacons by this algorithm. We show that the proposed algorithm is accurate location tracking is accomplished using the applying the proposed algorithm to indoor moving robot and the inertia sensor of robot and Kalman filter algorithm.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.65-74
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• 2016

Ship ad-hoc network (SANET) extends the coverage of the maritime communication among ships with the reduced cost. To fulfill the growing demands of real-time services, the SANET requires an efficient clock time synchronization algorithm which has not been carefully investigated under the ad-hoc maritime environment. This is mainly because the conventional algorithms only suggest to decrease the beacon collision probability that diminishes the clock drift among the units. However, the SANET is a very large-scale network in terms of geographic scope, e.g., with 100 km coverage. The key factor to affect the synchronization performance is the signal propagation delay, which has not being carefully considered in the existing algorithms. Therefore, it requires a robust multi-hop synchronization algorithm to support the communication among hundreds of the ships under the maritime environment. The proposed algorithm has to face and overcome several challenges, i.e., physical clock, e.g., coordinated universal time (UTC)/global positioning system (GPS) unavailable due to the atrocious weather, network link stability, and large propagation delay in the SANET. In this paper, we propose a logical clock synchronization algorithm with multi-hop function for the SANET, namely multi-hop clock synchronization for SANET (MCSS). It works in an ad-hoc manner in case of no UTC/GPS being available, and the multi-hop function makes sure the link stability of the network. For the proposed MCSS, the synchronization time reference nodes (STRNs) are efficiently selected by considering the propagation delay, and the beacon collision can be decreased by the combination of adaptive timing synchronization procedure (ATSP) with the proposed STRN selection procedure. Based on the simulation results, we finalize the multi-hop frame structure of the SANET by considering the clock synchronization, where the physical layer parameters are contrived to meet the requirements of target applications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.493-496
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• 2011

Currently in the development of community wireless technology is gaining interest in location-based services and as a result, the importance of the location information is a growing trend. To calculate the location information is being suggested several ways, among them Trilateration is representative. Trilateration is three beacon nodes, the distance between the location in which you want to calculate with information. Beacon from a node to know where to get information when the distance between the obstacle and the distance error caused by the surrounding environment, which leads to the exact location can not be obtained. Currently due to distance error, location information has a variety of algorithms to reduce the error. However, a systematic analysis of these algorithms is not progress. This paper analyzes the location-aware technologies, and the error the distance of the location information to reduce errors in the various aspects of the algorithm for the systematic and empirical comparison was evaluated through the analysis.

• The KIPS Transactions:PartC
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• v.16C no.6
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• pp.737-746
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• 2009

Given the increased interest in ubiquitous computing, wireless sensor network has been researched widely. The localization service which provides the location information of mobile user, is one of important service provided by sensor network. Many methods to obtain the location information of mobile user have been proposed. However, these methods were developed for only one mobile user so that it is hard to extend for multiple mobile users. If multiple mobile users start the localization process concurrently, there could be interference of beacon or ultrasound that each mobile user transmits. In the paper, we propose APL(Adaptive Power Control based Resource Allocation Technique for Efficient Localization Technique), the localization technique for multiple mobile nodes based on adaptive power control in mobile wireless sensor networks. In APL, collision of localization between sensor nodes is prevented by forcing the mobile node to get the permission of localization from anchor nodes. For this, we use RTS(Ready To Send) packet type for localization initiation by mobile node and CTS(Clear To Send) packet type for localization grant by anchor node. NTS(Not To Send) packet type is used to reject localization by anchor node for interference avoidance and STS(Start To Send) for synchronization between 모anchor nodes. At last, the power level of sensor node is controled adaptively to minimize the affected area. The experimental result shows that the number of interference between nodes are increased in proportion to the number of mobile nodes and APL provides efficient localization.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1294-1300
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• 2010

In an environment where all nodes move, the sensor node receives anchor node's position information within communication radius and modifies the received anchor node's position information by one's traveled distance and direction in saving in one's memory, where if there at least 3, one's position is determined by performing localization through trilateration. The proposed localization mechanisms have been simulated in the Matlab. In an environment where certain distance is maintained and nodes move towards the same direction, the probability for the sensor node to meet at least 3 anchor nodes with absolute coordinates within 1 hub range is remote. Even if the sensor node has estimated its position with at least 3 beacon information, the angle ${\theta}$ error of accelerator and digital compass will continuously apply by the passage of time in enlarging the error tolerance and its estimated position not being relied. Dead reckoning technology is used as a supplementary position tracking navigation technology in places where GPS doesn't operate, where one's position can be estimated by knowing the distance and direction the node has traveled with acceleration sensor and digital compass. The localization algorithm to be explained is a localization technique that uses Dead reckoning where all nodes are loaded with omnidirectional antenna, and assumes that one's traveling distance and direction can be known with accelerator and digital compass. The simulation results show that our scheme performed better than other mechanisms (e.g. MCL, DV-distance).

• Journal of the Korea Society of Computer and Information
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• v.12 no.4
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• pp.269-277
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• 2007

Wireless sensor network system is expected to get high attention in research for now and future owing to the advanced hardware development technology and its various applicabilities. Among variety of sensor network systems, the seashore and marine sensor network, which are extended to get sampling of marine resources, environmental monitoring to prevent disaster and to be applied to the area of sea route guidance. For these marine applications to be available, however, the provision of precise location information of every sensor nodes is essential. In this paper, the sequential localization algorithm for obtaining the location information of marine sensor nodes. The sequential localization is done with the utilization of a small number of beacon nodes along the seashore and gets the location of nodes by controling the sequences of localization and also minimizes the error accumulation. The key idea of this algorithm for localization is that the localization priority of each sensor nodes is determined by the number of reference nodes' information. This sequential algorithm shows the improved error performance and also provide the increased coverage of marine sensor network by enabling the maximum localization of sensor nodes as possible.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.6
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• pp.1493-1504
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• 2010

The localization service which provides the location information of mobile user, is one of important service provided by sensor network. Many methods to obtain the location information of mobile user have been proposed. However, these methods were developed for only one mobile user so that it is hard to extend for multiple mobile users. If multiple mobile users start the localization process concurrently, there could be interference of beacon or ultrasound that each mobile user transmits. In the paper, we propose LME, the localization technique for multiple mobile nodes in mobile wireless sensor networks. In LME, collision of localization between sensor nodes is prevented by forcing the mobile node to get the permission of localization from anchor nodes. For this, we use CTS packet type for localization initiation by mobile node and RTS packet type for localization grant by anchor node. NTS packet type is uevento reject localization by anchor node for interference avoidance.nghe experimental result shows that the number of interference between nodes are increased in proportion to the number of mobile nodes and LME provides efficient localization.