• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.2
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• pp.39-47
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• 2010

In Wireless Sensor Network, transmission errors are frequently occurred due to the node failure, battery discharge, and interference by objects. Although Directed Diffusion has been considered as a prominent Data-centric routing algorithm, it revealed some weaknesses at this kind of unexpected network errors. In order to address the problem, we proposed a radio-aware routing algorithm for improving reliability of Directed Diffusion in Wireless Sensor Networks. The proposed algorithm is aware of the network status based on the radio information of MAC and PHY layers using a cross-layer approach. The link quality and the node failure information from the acquired network status were used to decide an alternative path to provide a reliable data transmission in error-prone sensor networks. The proposed algorithm showed its effectiveness of the data delivery rate and data ratio with several simulations consisting of various error rates and the number of nodes.

• International Journal of Internet, Broadcasting and Communication
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• v.9 no.4
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• pp.38-43
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• 2017

Sensor Networks (WSNs) can be defined as a self-configured and infrastructure-less wireless networks to monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants and to cooperatively pass their data through the network to a main location or base-station where the data can be observed and analyzed. Typically a wireless sensor network contains hundreds of thousands of sensor nodes. The sensor nodes can communicate among themselves using radio signals. A wireless sensor node is equipped with sensing and computing devices, radio transceivers and power components. The individual nodes in a wireless sensor network (WSN) are inherently resource constrained: they have limited processing speed, storage capacity, communication bandwidth and limited-battery power. At present time, most of the research on WSNs has concentrated on the design of energy- and computationally efficient algorithms and protocols In order to extend the network life-time, in this paper we are looking into a routing protocol, especially LEACH and LEACH-related protocol. LEACH protocol is a representative routing protocol and improves overall network energy efficiency by allowing all nodes to be selected to the cluster head evenly once in a periodic manner. In LEACH, in case of movement of sensor nodes, there is a problem that the data transmission success rate decreases. In order to overcome LEACH's nodes movements, LEACH-Mobile protocol had proposed. But energy consumption increased because it consumes more energy to recognize which nodes moves and re-transfer data. In this paper we propose the new routing protocol considering nodes' mobility. In order to simulate the proposed protocol, we make a scenario, nodes' movements randomly and compared with the LEACH-Mobile protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.697-705
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• 2010

In Wireless Sensor Networks (WSNs), blanket (area) coverage analysis is generally carried to find the minimum number of active sensor nodes required to cover a monitoring interest area with the desired fractional coverage-threshold. Normally, the coverage analysis is performed using the stochastic geometry as a tool. The major component of such coverage analysis is the assumed sensing model. Hence, the accuracy of such analysis depends on the underlying assumption of the sensing model: how well the assumed sensing model characterizes the real sensing phenomenon. In this paper, we review the coverage analysis for different deterministic and probabilistic sensing models like Boolean and Shadow-fading model; and extend the analysis for Exponential and hybrid Boolean-Exponential model. From the analytical performance comparison, we demonstrate the redundancy (in terms of number of sensors) that could be resulted due to the coverage analysis based on the detection capability mal-characterizing sensing models.

• Composites Research
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• v.25 no.5
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• pp.136-140
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• 2012

This paper describes the bone healing process of fractured long bones such as a tibia applied by composite IM rods using finite element analysis. To simulated tissue differentiation process mechano-regulation theory with a deviatoric strain was implemented and a user's subroutine programmed by a Python code for an iterative calculation was used. To broadly find the appropriate rod modulus for healing bone fractures, composite IM rods were analyzed considering the stacking sequence. To compare mechanical stimulation at fracture gap, two kinds of initial loading conditions were applied. As a result, it was found that the initial loading condition was the most sensitive factor for the healing performance. In case a composite IM rod made of a plain weave carbon fiber/epoxy (WSN3k) had a stacking sequence of $[{\pm}45]_{nT}$, the healing efficiency was the most effective under a initial load of 10%BW.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.125-130
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• 2013

According to the law revision of TPMS mounting obligations in Korea, researches about energy harvester which is the alternative of the battery are actively performed by many groups. Because WSN (Wireless Sensor Network) has the proposition of "Install and forget" and the power supplier also has the same performance as the vehicle's lifetime. In this paper, electromagnetic induction type of energy harvester through the relative motion between the rotating wheel and the fixed brake disc is introduced by using the most efficient source as the rotating motion in the view of vehicle's mechanism. The coil on the wheel and the permanent magnet at the brake disc are arranged in several ways. These various arrangements are the number of coil turns are consisted of design variables. By using the orthogonal array to reduce the experimental cost, the optimal composition is verified through the experiment. Finally the validity of the module is considered by measuring the level of storable electrical energy.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.3-12
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• 2013

Wireless Sensor Network (WSN) is used in the railway field in terms of efficient management and maintenance. Sensor communication technology based on IEEE 802.15.4/ZigBee is used in low speed train. However, it is difficult to apply in the high speed train that exposed to severe wireless channel environments. In this paper, we propose the sensor communication algorithm for high speed train environment. we improve error rate and throughput using Equalizer, Multiple Input Multiple Output (MIMO), Flexible Spreading Factor (SF) and Modulation. Also, we have analyzed the performance of the IEEE 802.15.4/ZigBee based on the standard of physical layer of 2.4GHz band in each algorithms. Simulation results show that proposed algorithms can improve error rate and throughput of conventional system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.3
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• pp.943-961
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• 2020

With the advent of IoT technology and Big Data computing, the importance of WSNs (Wireless Sensor Networks) has been on the rise. For energy-efficient and collection-efficient delivery of any sensed data, lots of novel wireless medium access control (MAC) protocols have been proposed and these MAC schemes are the basis of many IoT systems that leads the upcoming fourth industrial revolution. WSNs play a very important role in collecting Big Data from various IoT sensors. Also, due to the limited amount of battery driving the sensors, energy-saving MAC technologies have been recently studied. In addition, as new IoT technologies for Big Data computing emerge to meet different needs, both sensors and sinks need to be mobile. To guarantee stability of WSNs with dynamic topologies as well as frequent physical changes, the existing MAC schemes must be tuned for better adapting to the new WSN environment which includes energy-efficiency and collection-efficiency of sensors, coverage of WSNs and data collecting methods of sinks. To address these issues, in this paper, a self-organization scheme for mobile sensor networks with mobile multiple sinks has been proposed and verified to adapt both mobile sensors and multiple sinks to 3-dimensional group management MAC protocol. Performance evaluations show that the proposed scheme outperforms the previous schemes in terms of the various usage cases. Therefore, the proposed self-organization scheme might be adaptable for various computing and networking environments with big data.

• Journal of Korea Multimedia Society
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• v.13 no.1
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• pp.122-132
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• 2010

The analysis of ocean environment offers us essential information for ocean exploration. But ocean environment has a lot of environmental variables such as the movements of nodes by an ocean current, corrosion by salt water, attenuation of radio wave, occurrences of multi-path and difficulty of sensor nodes' deployment. It is accordingly difficult and complex to gather and process the environmental information through ocean data communication due to these constraints of ocean environment unlike the terrestrial wireless networks. To overcome these problems, we organized ocean communication network for monitoring underwater environment by real experiment in Gyeongpoho similar to ocean environment. Therefore, this paper aims at overcoming major obstacles in ocean environment, effectively deploying sensor nodes for ocean environment monitoring and defining an efficient structure suitable for communication environment by the implementation of ocean environment monitoring system in Gyeongpoho.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.357-360
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• 2008

Vital sign monitoring system using IEEE 502.IS.4 based wireless sensor network(WSN) is designed and developed on mobile environment and sensor node platform. WSN and CDMA are integrated to create a wide coverage to support various environments like inside and outside. We developed query processor to use selective any devices(ECG, Blood pressure and sugar module) and control of the self-organizing network of sensor nodes in a wireless sensor network. Vital sign from wireless medical any devices are analysed in cell phone first for real time signal analyses and the abnormal vital signs are sent and save to hospital server for detail signal processing. wireless signal traffic in wireless sensor network environment or data communication inside the cell phone is reduced.

• The KIPS Transactions:PartC
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• v.17C no.1
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• pp.69-80
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• 2010

Wireless sensor networks (WSN) consisting of a large number of sensors aim to gather data in a variety of environments and are being used and applied to many different fields. The sensor nodes composing a sensor network operate on battery of limited power and as a result, high energy efficiency and long network lifetime are major goals of research in the WSN. In this paper we propose a novel tree-based clustering approach for energy efficient wireless sensor networks. The proposed scheme forms the cluster and the nodes in a cluster construct a tree with the root of the cluster-head., The height of the tree is the distance of the member nodes to the cluster-head. Computer simulation shows that the proposed scheme enhances energy efficiency and balances the energy consumption among the nodes, and thus significantly extends the network lifetime compared to the existing schemes such as LEACH, PEGASIS, and TREEPSI.