• 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 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.

• The KIPS Transactions:PartC
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• v.16C no.1
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• pp.91-100
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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 IAL, the localization technique with interference avoidance for multiple mobile nodes in mobile wireless sensor networks. In IAL, interference is prevented by forcing the mobile node to get the permission of localization from anchor nodes. For this, we define LIP packet type for localization initiation by mobile node and LGP packet type for localization grant by anchor node. LRP packet type is used to reject localization by anchor node for interference avoidance. The experimental result shows that the number of interference between nodes are increased in proportion to the number of mobile nodes and IAL provides efficient localization.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.2
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• pp.406-423
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• 2014

The recent advances in wireless communication systems and semiconductor technologies are paving the way for new applications over wireless sensor networks. Health-monitoring application (HMA) is one such emerging technology that is focused on sensing and reporting human vital signs through the communication network comprising sensor devices in the vicinity of the human body. The sensed vital signs can be divided into two categories based on the importance and the frequency of occurrence: occasional emergency signs and regular normal signs. The occasional emergency signs are critical, so they have to be delivered by the specified deadlines, whereas the regular normal signs are non-critical and are only required to be delivered with best effort. Handling the occasional emergency sign is one of the most important attributes in HMA because a human life may depend on correct handling of the situation. That is why the underlying network protocol suite for HMA should ensure that the emergency signs will be reported in a timely manner. However, HMA based on IEEE 802.15.4 might not be able to do so owing to the lack of an appropriate emergency-handling mechanism. Hence, in this paper, we propose a new emergency-handling mechanism to reduce the emergency reporting delay in IEEE 802.15.4 through the modified superframe structure. A fraction of an inactive period is modified into three new periods called the emergency reporting period, emergency beacon period, and emergency transmission period, which are used opportunistically only for immediate emergency reporting and reliable data transmission. Extensive simulation is performed to evaluate the performance of the proposed scheme. The results reveal that the proposed scheme achieves improved latency and higher emergency packets delivery ratio compared with the conventional IEEE 802.15.4 MAC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8A
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• pp.575-582
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• 2009

The localization algorithm(LAtu) using the IDentification Code($C_{ID}$) is suggested in RSS(Received Signal Strength) based Wireless Sensor Network(WSN), and the localization system using the suggested algorithm is designed and implemented in this paper. In addition to this, the performance of ranging correction quality and localization error of the localization system(System(LAtu)) that is developed using the LAtu is analyzed and compared with that of the localization system(System(LAieee)) using the channel model of IEEE 802.15.4 standard(LAieee) by the actual experimentation. From the experimentation, the ranging correction quality is analyzed that the LAtu is highly better than the channel model of LAieee about 34% under the distance between the moving module and the beacon module($D_{MM-BM}$) is 2m, and is also a few better than that of the LAieee about average 5% under the $D_{MM-BM}$ is above 5m. The localization error quality of the System(LAtu) is lower than that of the System(LAieee)) about 1cm under the lecture room and 4cm in the large lecture room.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3B
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• pp.485-492
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• 2010

Intelligent Transport System(ITS) has been studied in various systems, such as road environment information offering, vehicle short-range wireless/wire communication, vehicle collision preventing and pedestrian safety offering systems. Related to this, the USN technology based on the sensing accuracy for motorists and pedestrians safety, the information reliability, the maintenance and convenience for Sensor Network is highlighted. This study uses various sensors to construct USN to the road, and connect it to the developed RSU so it collects the real-time road environment information and offers it to OBU and Traffic Control Surveillance Center with Road Weather Information System. RSU collects roadside information for driver's safety and analyzes it to offer IP and beacon service according to the service priority to OBU & upper layer terminal. In the upper layer terminal it is developed the IP based Settop Box application program to offer the urban traffic information & road environment, and environment sensor error, etc. Finally, RWIS develops the real-time collection of roadside information to complement the driver's safety to the intelligent traffic system, and presents various service modes with technology convergence.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.2
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• pp.119-124
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• 2013

Recent increasing demand on the indoor localization requires more advanced and hybrid technology. This paper proposes an application of the hybrid indoor localization method based on a position-coded pattern that can be used with other existing indoor localization techniques such as vision, beacon, or landmark technique. To reduce the pattern-recognition error rate, the error detection and correction algorithm was applied based on Hamming code. The indoor localization experiments based on the proposed algorithm were performed by using a QCIF-grade CMOS sensor and a position-coded pattern with an area of $1.7{\times}1.7mm^2$. The experiments have shown that the position recognition error ratio was less than 0.9 % with 0.4 mm localization accuracy. The results suggest that the proposed method could be feasibly applied for the localization of the indoor mobile service robots.

• Journal of Computing Science and Engineering
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• v.9 no.2
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• pp.83-97
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• 2015

IEEE 802.15.4 is a global standard designed for emerging applications in low-rate wireless personal area networks (LR-WPANs). The standard provides beneficial features, such as a beacon-enabled mode and guaranteed time slots for realtime data delivery. However, how to optimally operate those features is still an open issue. For the optimal operation of the features, this paper proposes a holistic optimization method that jointly optimizes three cross-related problems: cluster-tree construction, nodes' power configuration, and duty-cycle scheduling. Our holistic optimization method provides a solution for those problems so that all the real-time packets can be delivered within their deadlines in the most energy-efficient way. Our simulation study shows that compared to existing methods, our holistic optimization can guarantee the on-time delivery of all real-time packets while significantly saving energy, consequently, significantly increasing the lifetime of the network. Furthermore, we show that our holistic optimization can be extended to take advantage of the spatial reuse of a radio frequency resource among long distance nodes and, hence, significantly increase the entire network capacity.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.381-384
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• 2007

RF 신호 강도인 RSSI(Received Signal Strength indication)를 이용해 지역화를 하는 방법론이나 알고리즘은 많이 연구되어 왔다. 그러나 대다수의 연구에서 추가적인 장비를 요구하거나, 복잡한 시스템 환경을 필요로 한다. 본 논문에서는 일반적인 무선랜 환경을 사용할 수 있는 노트북에서, Windows 기반의 802.11의 RSSI를 이용해 지역화를 수행하였다. IEEE 802.11의 네트워킹 구성을 한 센서노드들 중에 AP(Access Point) 역할을 하는 한 개의 고정노드(Anchor)를 중심으로 다수의 움직일 수 있는 모바일 노드들의 위치를 추적해가는 방법이며, Anchor가 많아지거나 모바일 노드가 늘어나면 지역화의 정확도는 증가하게 된다. 이 방법은 일반적인 802.11의 무선랜 환경이 가능한 랩톱에서도 쉽게 적응이 가능하며, 부가적인 장비의 의존성이 전혀 없고 소프트웨어 적인 방법론으로 해결하였다. 또한 지역화가 가능함과 동시에 각각의 센서 노드들은 802.11을 이용한 데이터 송수신이 가능하다. 본 논문에서는 MS의 Windows 플랫폼 기반으로 테스트하였고, 효과적으로 Beacon 패킷을 송출하기 위한 해법을 제시한다.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06d
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• pp.165-169
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• 2010

무선 센서 네트워크에서 LBS(Location Based Services) 에 적합한 기술적인 요구사항이 증가하고 있다. 최근 LBS의 가장 기본이 되는 위치추정(Localization) 에 관련하여 많은 알고리즘이 제안되고 있지만 센서 네트워크를 위한 요구사항을 만족하지 못하고 있다. 본 논문에서는 센서 네트워크에서 5가지 주된 위치추정방식의 요구사항을 정의하고 이를 만족하는 SCORE 알고리즘을 제안한다. 고정노드는 다중 파워의 비콘신호를 전승하게 되며, 이때 고정노드는 센서노드에게 위치정보를 비콘 신호에 담아서 전승하게 되는데 이때 다중 비콘신호에 신호 순서에 해당하는 SCORE 라고 고정노드로부터 센서노드까지의 거리에 대한 값을 포함하여서 전승하게 된다. 여러 고정노드로부터 수신한 위치정보를 수집한 센서노드는 간단한 연산과정을 거쳐 자신의 위치를 분산적으로 추정하게 된다. CAB 위치추정 알고리즘의 2 가지 알고리즘을 동시에 사용하는 복잡성 문제와 Diffusion 알고리즘의 네트워크 외곽에서 발생하는 큰 위치추정 오류의 문제점을 SCORE 알고리즘에서는 해결하였다. 시뮬레이션 결과 SCORE 알고리즘은 독립적인 알고리즘 사용임에도 불구하고 CAB 위치추정 알고리즘과 비슷한 성능을 나타내었으며, Diffusion 알고리즘에서 발생한 네트워크 외곽 센서노드들의 오류를 평균 7% 이상 향상 시켰다.