• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.6
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• pp.42-47
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• 2008

In this article a novel constant amplitude precoding for impulse UWB system is proposed. According to IEEE 802.15.4a, impulse UWB can be used in indoor localization and sensor data transmission. Most USN(ubiquitous sensor networks) needs multiple access. However impulse UWB system has a limited capability to detect superpositioned signal induced by multiple access. To overcome this problem we have adopted the concept of CAMC(Constant Amplitude Multi-Code) deviced by Wada and Kim. The proposed system consists of systematic constant amplitude precoding and LDPC decoding. And this system shows a good BER performance in computer simulation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.3
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• pp.93-99
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• 2008

Most of the current research works on high-technology is being carried on to provide ubiquitous services to people. To make that possible, ubiquitous computing networks should be deployed in the first place, where ubiquitous sensor network (USN) will take a very big role. This paper is devoted to introduce a new transmission technique to make USN more independent and reliable as an infra-structure for ubiquitous services. The proposed scheme can elevate the network performance by ensuring the reliability of data transmission. Especially, the proposed scheme can reduce network traffic and communication cost by detecting data error without additional data and communication. In addition, it has an advantage of using the legacy routing protocols.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.3
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• pp.243-246
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• 2009

A cluster-based routing with a hierachical structure for continuous query stream ubiquitous sensor network is proposed in this paper. the proposed method realizes high energy-efficiency by using a head-set instead of head for transmitting node-messages to a base station. By using head-set, the method make network lifetime increased.

• ETRI Journal
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• v.34 no.5
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• pp.713-718
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• 2012

Sensor nodes in ubiquitous sensor networks require autonomous replacement of deteriorated gas sensors with reserved sensors, which has led us to develop an encapsulation technique to avoid poisoning the reserved sensors and an autonomous activation technique to replace a deteriorated sensor with a reserved sensor. Encapsulations of $In_2O_3$ nanoparticles with poly(ethylene-co-vinyl alcohol) (EVOH) or polyvinylidene difluoride (PVDF) as gas barrier layers are reported. The EVOH or PVDF films are used for an encapsulation of $In_2O_3$ as a sensing material and are effective in blocking $In_2O_3$ from contacting formaldehyde (HCHO) gas. The activation process of $In_2O_3$ by removing the EVOH through heating is effective. However, the thermal decomposition of the PVDF affects the property of the $In_2O_3$ in terms of the gas reactivity. The response of the sensor to HCHO gas after removing the EVOH is 26%, which is not significantly different with the response of 28% in a reference sample that was not treated at all. We believe that the selection of gas barrier materials for the encapsulation and activation of $In_2O_3$ should be considered because of the ill effect the byproduct of thermal decomposition has on the sensing materials and other thermal properties of the barrier materials.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.1
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• pp.105-114
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• 2006

Ubiquitous Sensor Network consists of a number of sensor nodes with a limited computation power and limited communication capabilities, and a sensor node is able to communicate with each other at anytime and in any place. Due to the rapid research and development in sensor networks, it will rapidly grow into environments where hmm beings can interact in an intuitive way with sensing objects which can be PDAs, sensors, or even clothes in the future. We are aiming at realizing an Unattended Secure Security System to apply it to Ubiquitous Sensor Network. In this paper, the vulnerabilities in the Unattended security system are identified, and a new protocol called OMAC-SNEP is proposed for the Unattended Secure Security System. Because the CBC-MAC in SNEP is not secure unless the message length is fixed, the CBC-MAC in SNEP was replaced with OMAC in SNEP. We have shown that the proposed protocol is secure for my bit length of messages and is almost as efficient as the CBC-MAC with only one key. OMAC-SNEP can be used not only in Unattended Security System, but also any other Sensor Networks.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.875-885
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• 2010

Recently, the role of Ubiquitous Sensor Network(USN) has been considered to be essential for supporting the near future Network Centric Warfare(NCW) and Tactical Information Communication Network(TICN). In this paper, we explore a set of data storage methods(external storage, local storage and data storage) and query processing methods in WSN. In particular, we focus on analyzing a novel data structure for supporting the local storage method, named the partial ordered tree(POT). The main idea behind POT is that sensor readings are usually correlated with the physical spatial domain. With the help of POT, only a small portion of sensor nodes participate in query processing tasks, and thus network lifetime is greatly increased. Through a series of simulation experiments, we demonstrate that the POT based local storage method clearly outperforms the existing data storage methods in terms of the energy-efficiency, which directly affects the network lifetime, for processing exact match queries, range queries and top-k queries.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5B
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• pp.557-565
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• 2011

In this paper, we assume that sensor nodes organize the multi-hop networks, are fixed, and operate as full function devices(FFD). The wireless sensor network(WSN) only consists of mobile nodes without the assistance from the fixed infrastructure, which increases the flexibility of the network. However, it is difficult to perform routing in the WSN, since sensor nodes freely join in and drop out of the network, and some sensor nodes have very low power. We propose the algorithm combining routing schemes based on the bitmap and cluster methods in this paper. Through computer simulations, we show the validity of the proposed algorithm.

• Journal of Korea Spatial Information System Society
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• v.8 no.3
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• pp.117-130
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• 2006

With the rapid development of technologies related to Ubiquitous Sensor Network (USN), sensors are being utilized in various application areas. In general, the data sensed by each sensor node on ubiquitous sensor networks are stored into the central server for efficient search. Because update is delayed to reduce the cost of update in this environment, uncertain data can be stored in the central server. In addition, Uncertain data make query processing produce wrong results in the central server. Thus, this paper examines how to process uncertain data in ubiquitous sensor networks and suggests a new index for efficient processing of uncertain data. The index reduces the cost of update by delaying update in uncertainty areas. Uncertainty areas are areas where uncertain data are likely to exist. In addition, it solves the problem of low accuracy in search resulting from update delay by delaying update only for specific update areas. Lastly, we analyze the performance of the index and prove the superiority of its performance by comparing its performance evaluation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.513-516
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• 2008

The sensor node's performance is expected to be improved and the price will be largely decreased. As USN-applied field is expanded, multiple application services are expected to be provided through one USN soon. Multiple applications be required a periodic data reporting, consecutive information monitoring, event-driven data and query-based data as the data pattern that USN is delivered. Accordingly, the mechanism which can assure QoS according to each data characteristic is required. In this paper, A proposed protocol apply the duty cycle of S-MAC protocol variably and flexible according QoS level. This method largely reduces the delay on the delay-sensitive traffic, while keeping the energy efficiency.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.2
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• pp.71-78
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• 2008

The sensor node's performance is expected to be improved and the price will be largely decreased. As USN-applied field is expanded, multiple application services are expected to be provided through one USN soon. Multiple applications be required a periodic data reporting, consecutive information monitoring, event-driven data and query-based data as the data pattern that USN is delivered. Accordingly, the mechanism which can assure QoS according to each data characteristic is required. In this paper, A proposed protocol apply the duty cycle of S-MAC protocol variably and flexible according QoS level. This method largely reduces the delay on the delay-sensitive traffic, while keeping the energy efficiency.