• Smart Structures and Systems
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• v.11 no.3
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• pp.261-282
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• 2013

Structural health monitoring (SHM) is an application area of Wireless Sensor Networks (WSNs) which usually needs high data communication rate to transfer a large amount of monitoring data. Traditional sink node can only process data from one communication channel at the same time because of the single radio chip structure. The sink node constitutes a bottleneck for constructing a high data rate SHM application giving rise to a long data transfer time. Multi-channel communication has been proved to be an efficient method to improve the data throughput by enabling parallel transmissions among different frequency channels. This paper proposes an 8-radio integrated sink node design method based on Field Programmable Gate Array (FPGA) and the time synchronization mechanism for the multi-channel network based on the proposed sink node. Three experiments have been performed to evaluate the data transfer ability of the developed multi-radio sink node and the performance of the time synchronization mechanism. A high data throughput of 1020Kbps of the developed sink node has been proved by experiments using IEEE.805.15.4.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3D
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• pp.247-258
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• 2012

This research evaluates the serviceability of ZigBee device that provides a potential technology to realizing the ubiquitous computing by improving the productivity and effectiveness in construction and data acquisition. Literature review was conducted in various application areas such as bridge monitoring, slope management, road management, highway traffic control. In addition characteristics and challenges in various wireless technologies are described to identify their adoptability to construction environment. Among them, ZigBee technology was selected to introduce the functionality on hardware, network, and security. Then, questionnaire survey was implemented by four different group, construction engineers, students, hardware developers, and researchers to explore the success and failure factors of ZigBee technology in construction area. The results proposes a guideline of the applicability of ZigBee technology in the area of serviceability, application area, considerations, and future direction. This paper would provide valuable information for future researches and technology development in designing the wireless sensor network applications.

• Journal of Advanced Navigation Technology
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• v.13 no.1
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• pp.79-86
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• 2009

As information communication technology developed we could monitor temperature, weather, indoor and outdoor status which we need to monitor using various sensors. Even further we could monitor our body such as Sa02 and serologic chemical tests easily at home or office. It is possible though interlocking the house medical instrument with the wireless public data network. Data from sensors can be transmitted to the distant control room and will be essentially applied through wireless public data network. In this study we measured various sensor data for the telemetry in one system. The sensing items are mainly focused on the static and dynamic behaviors of the bridge, building, instruments. The study suggests the transmit system model utilized by the wireless public data network. The suggestion in the study of telemetry system provides movement and preservation. And it will exam various condition in distance or at home.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1185-1192
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• 2015

A wireless bridge is essential to transmit control and managing information to sensors or instruments from a central integrated ship area network station. In this paper, a WPAN protocol is adopted for development of a seamless N-screen wireless service in Indoor and Ship Area Networks. Furthermore, to provide the OSMU (One Source Multi Use) N-screen service through P2P streaming in the seamless WPAN protocol, a Grid-based WPAN networking technology is proposed and analyzed. The proposed Grid-based WPAN networking technology supports multi-path and fast path-setup functions for N-screen communications. The simulation results demonstrate that the proposed Grid-based WPAN networking technology outperforms the IEEE 802.15.4 based network in terms of N-screen transmission delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8A
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• pp.600-609
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• 2009

The traditional carrier sense multiple access (CSMA) protocol like IEEE 802.11 Distributed Coordination Function (DCF) does not handle the constraints adequately, leading to degraded delay latency and throughput as the network scales are enlarged. We present more efficient method of a medium access for real-time wireless sensor networks. Proposed MAC protocol is like the randomized CSMA protocol, but unlike previous legacy protocols, it does not use a time-varying contention window from which a node randomly picks a transmission slot. To reduce the latency for the delivery of event reports, we carefully decide to select a fixed-size contention window with non-uniform probability distribution of transmitting in each slot. We show that the proposed method can offer up to severaansimes latency reduction compared to legacy of IEEE 802.11 as the size of the sensor network scales up to 256 nodes using widely using network simulation package,caS-2. We finally show that proposed MAC scheme comes close to meet bounds on the best latency being achieved by a decentralized CSMA-based MAC protocol for real-time wireless sensor networks which is sensitive to delay latency.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.640-652
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• 2012

Many studies have investigated the smart grid architecture and communication models in the past few years. However, the communication model and architecture for a smart grid still remain unclear. Today's electric power distribution is very complex and maladapted because of the lack of efficient and cost-effective energy generation, distribution, and consumption management systems. A wireless smart grid communication system can play an important role in achieving these goals. In this paper, we describe a smart grid communication architecture in which we merge customers and distributors into a single domain. In the proposed architecture, all the home area networks, neighborhood area networks, and local electrical equipment form a local wireless mesh network (LWMN). Each device or meter can act as a source, router, or relay. The data generated in any node (device/meter) reaches the data collector via other nodes. The data collector transmits this data via the access point of a wide area network (WAN). Finally, data is transferred to the service provider or to the control center of the smart grid. We propose a wireless cooperative communication model for the LWMN.We deploy a limited number of smart relays to improve the performance of the network. A novel relay selection mechanism is also proposed to reduce the relay selection overhead. Simulation results show that our cooperative smart grid (coopSG) communication model improves the end-to-end packet delivery latency, throughput, and energy efficiency over both the Wang et al. and Niyato et al. models.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.4 s.316
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• pp.36-44
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• 2007

In this paper, we implement the speech & face recognition system to support various ubiquitous sensor network application services such as switch control, authentication, etc. using wireless audio and image interface. The proposed system is consist of the H/W with audio and image sensor and S/W such as speech recognition algorithm using psychoacoustic model, face recognition algorithm using PCA (Principal Components Analysis) and LDPC (Low Density Parity Check). The proposed speech and face recognition systems are inserted in a HOST PC to use the sensor energy effectively. And improve the accuracy of speech and face recognition, we implement a FEC (Forward Error Correction) system Also, we optimized the simulation coefficient and test environment to effectively remove the wireless channel noises and correcting wireless channel errors. As a result, when the distance that between audio sensor and the source of voice is less then 1.5m FAR and FRR are 0.126% and 7.5% respectively. The face recognition algorithm step is limited 2 times, GAR and FAR are 98.5% and 0.036%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4B
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• pp.219-226
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• 2012

In wireless sensor networks (WSNs), location-based multicast routing (LMR) technique can increase the network life time and the channel capacity by reducing the number of duplicated data transmissions and control messages. However, previous LMR techniques can suffer from significant performance degradation due to concrete walls or other interfering objects deployed in the real environment, since they transmit the packets by using only the locations of the sensor nodes. To solve this problem, we propose an interference-aware location based multicast algorithm for WSNs. In the proposed algorithm, each node adjusts the energy cost for each link adaptively considering the interference effect and uses it for multicast decision in order to minimize the interference impact. Experimental results show that the proposed algorithm improves the delivery and energy performance when the network is affected by interference.

• Journal of KIISE:Databases
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• v.36 no.4
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• pp.292-305
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• 2009

Wireless sensor networks have a lot of application areas such as industrial process control, machine and resource management, environment and habitat monitoring. One of the main objects of using wireless sensor networks in these areas is the event detection. To detect events at a user's request, we need a join processing between sensor data and the predicates of the events. If there are too many predicates of events compared with a node's capacity, it is impossible to store them in a node and to do an in-network join with the generated sensor data This paper proposes a predicate-merge based in-network join approach to efficiently detect multiple events, considering the limited capacity of a sensor node and many predicates of events. It reduces the number of the original predicates of events by substituting some pairs of original predicates with some merged predicates. We create an estimation model of a message transmission cost and apply it to the selection algorithm of targets for merged predicates. The experiments validate the cost estimation model and show the superior performance of the proposed approach compared with the existing approaches.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.12
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• pp.1659-1665
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• 2019

In this paper, a novel design of a compact printed monopole antenna for wireless local area network (WLAN) applications is investigated. The radiator with a patch of different line width and step-shaped ground planes is used to reduce the antenna size. The size of the antenna is 16 × 17 × 1 ㎣ and is fabricated with a photolithography technique. The simulated and measured results agree well. The resonant frequency of the investigated antenna is about 5.2 GHz and can cover an impedance bandwidth of 1 GHz for the measurement result. In addition, we presented the measured radiation pattern, presented the gain and efficiency measured in the required WLAN 5 GHz frequency band (5.15-5.825 GHz), and confirmed that it can be used as a 5 GHz band WLAN antenna. The investigated antenna has a small size, light weight, low cost, omni-directional radiation pattern, high gain, and high efficiency.