• 대한임베디드공학회논문지
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• 제1권2호
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• pp.104-112
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• 2006

ZigBee is the emerging industrial standard for ad hoc networks based on IEEE 802.15.4. It is used for low data rate and low power wireless network applications. Expected applications of ZigBee include wireless sensor networks for remote monitoring, home control, and industrial automation. Since one of the most important design goals of ZigBee is to reduce the installation and running costs, the ZigBee stack is embedded in the cheap and small micro-controller unit. The hierarchical routing algorithm is used for ZigBee end devices which have very limited resources. Using the block addressing scheme, end devices can send data to the destination without a routing table. However, hierarchical routing has the problem that the packets follow the tree hierarchy to the destination even if the destination is located nearby. In this paper, we propose a scheme to improve the hierarchical routing algorithm in ZigBee networks by employing the neighbor table that is originally used together with the routing table. We suggest selecting the neighbor node that has the minimum remaining hops to the destination as the next hop node. Simulation result shows that the proposed scheme saves more than 30% of the hop counts compared with the original hierarchical routing.

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.658-665
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• 2013

While the chirp signal is extensively used in radar and sonar systems for target decision in wireless communication systems, it has not been widely used for positioning in indoor environments. Recently, the IEEE 802.15.4a standard has adopted the chirp spread spectrum (CSS) as an underlying technique for low-power and low-complexity precise localization. Chirp signal based ranging solutions have been established and deployed but their ranging performance has not been analyzed in multipath environments. This paper presents a ranging performance analysis of a chirp signal and suggests a method to suppress multipath error by using a type of non-linear chirp signal. Multipath ranging performance is evaluated using a conventional linear chirp signal and the proposed non-linear chirp signal. We verify the feasibility of both methods using two-ray multipath model simulation. Our results demonstrate that the proposed non-linear chirp signal can successfully suppress the multipath error.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2008년도 추계종합학술대회 B
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• pp.365-368
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• 2008

This paper presents a new concept of IP-based wireless sensor networks and also introduces a routing protocol that is based on clustering for global healthcare information system. Low-power wireless personal area networks (LoWPANs) conform the standard by IEEE 802.15.4-2003 to IPv6 that makes 6lowpan. It characterized by low bit rate, low power, and low cost as well as protocol for wireless connections. The 6lowpan node with biomedical sensor devices fixed on the patient body area network that should be connected to the gateway in personal area network. Each 6lowpan nodes have IP-addresses that would be directly connected to the internet. With the help of IP-address service provider can recognize or analysis patient biomedical data from anywhere on globe by internet service provider equipments such as cell phone, PDA, note book. The system has been evaluated by technical verification, clinical test, user survey and current status of patient. We used NS-2.33 simulator for our prototype and also simulate the routing protocols. The result shows the performance of biomedical data packets in multi-hope routing as well as represents the topology of the networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권9호
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• pp.1528-1543
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• 2011

With increasing the using of wireless technologies in essential fields such as the medical application, this paper proposes different scenarios for the transmission of images over wireless networks. The paper uses the IEEE ZigBee 802.15.4 for applying the proposed schemes. It is a Wireless Personal Area Network (WPAN). This paper presents a novel chaotic interleaving scheme against error bursts. Also, the paper studies the proposed interleaver with the convolutional code with different constraint lengths (K). A comparison study between the standard scheme and proposed schemes for image transmission over a correlated fading channel is presented. The simulation results show the superiority of the proposed chaotic interleaving scheme over the traditional schemes. Also, the chaotic interleaver packet-by-packet basis gives a high quality image with (K=3) and reduces the need for the complex encoder with K=7.

• 한국인터넷방송통신학회논문지
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• 제11권2호
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• pp.119-126
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• 2011

유비쿼터스 환경에서 위치추적 서비스를 구현하기 위해서는 위치 정보 및 이를 기반으로 한 주변의 상황에 대한 정보와 최적화된 위치 서비스 제공이 필요하다. 본 논문에서 제안하는 위치보정 기법은 실제 위치하는 측정태그와 보정태그와의 거리계산을 통하여 최적의 위치 값을 추출해내는 기법으로써 우선적으로 앤커에 수신된 태그의 위치 값 계산을 한 후 보정태그와의 거리 오차 계산을 통하여 위치 값을 보정한다. 본 논문에서는 CSS기반의 RF칩을 이용하여 실내에서 각 노드 간의 위치를 측정하는 시스템을 개발하고, 이에 대한 정밀도를 높이는 알고리즘을 제안하고자 한다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2008년도 추계종합학술대회 B
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• pp.265-269
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• 2008

Home health care with compact wearable units sounds to be a convenient solution for the elderly people living independently. This paper presents a method to detect fall from the other activities of daily living and also to classify those activities. This kind of ambulatory monitoring enables them to get an emergency help in the case of the fatal fall event and can provide their general health status by observing the activities being performed in daily life. A tri-axial accelerometer sensor is used to get the acceleration anomalies associated with the user's movements. The three axis acceleration data are transferred to the base station sensor node via an IEEE 802.15.4 compliant zigbee module. The base station sensor node sends the data to base station PC for an offline processing. This work shows the feature set preparation using the principal component analysis (PCA) for the designing of neural network. The work includes the most common activities of daily living (ADL) like Rest, Walk and Run along with the detection of fall events from ADL. The angle from the vertical is found to be the most significant feature parameter for classification of fall while mean, standard deviation and FFT coefficients were used as the feature parameter for classifying the other activities under consideration. The accuracy for detection of fall events is 86%. The overall accuracy for ADL and fall is 94%.