• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.4
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• pp.609-616
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• 2023

In a wireless network environment, since sensors are not always connected to power, the life of a battery, which is an energy source supplied to sensors, is limited. Therefore, various studies have been conducted to extend the network life, and a layer-based routing protocol, LEACH(: Low-energy Adaptive Clustering Hierarchy), has emerged for efficient energy use. However, the LEACH protocol, which transmits fused data directly to the sink node, has a limitation in that it consumes as much energy as the square of the transmission distance when transmitting data. To improve these limitations, this paper proposes an algorithm that can minimize the transmission distance with multi-hop transmission where cluster heads are chained between cluster heads through relative distance calculation from sink nodes in every round.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.3
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• pp.331-335
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• 2010

Previous low-energy time synchronization methods have mainly focused on reducing the number of transmission or reception packets. However, this paper proposes a method that reduces the percentage of time a node has to be awake (the duty cycle), assuming that a periodic sleep-wake cycle is used to conserve energy. Based on our experience with actual WSN devices, a system model is proposed, and the potential performance of the proposed method, with different parameter values, is analyzed. To further demonstrate the feasibility of our method, experiments were conducted using nine WSN devices in a $3{\times}3$ grid network topology. The results show the average synchronization error is 107.57 $\mu{s}$ in duty cycle 5% and synchronization period 10 sec, and 130 $\mu{s}$ in duty cycle 2.5% and synchronization period 20 sec.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.369-372
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• 2008

무선 센서 네트워크(WSN)는 소규모, 저비용, 저전력 지능형의 센서 노드로 구성되고, 원격 환경 감시와 군사작전 및 재난 상황 등에 응용 될 수 있는 기술이다. 이러한 센서 네트워크에서 구성된 노드의 에너지 공급은 독립된 소형배터리를 통해 이루어진다. 따라서 각 노드에서의 에너지의 효율적인 관리가 무선 센서 네트워크의 최대 쟁점이 되고 있다. 본 논문에서는 이러한 노드의 제한된 배터리 자원을 보다 효율적으로 유지 관리하기 위한 방법으로 ASIT(Advanced Sensing Interval Time) 알고리즘을 제안한다. 제안된 ASIT란 입력된 센싱 값의 변화와 센서 노드의 에너지 잔여량에 따라 센싱 주기를 제어 관리하는 방법으로 이에 대한 모델링을 수립하고, 실제 노드 관리 결과와 모델링 된 결과의 오차를 관찰하여 적중율을 향상하는 기법을 제안한 것이다. 제안된 ASIT의 알고리즘으로부터 센서 노드의 수명을 향상 시켜 궁극적으로는 무선 센서 네트워크 전체의 망 접속의 신뢰성과 노드 관리 수명을 연장시키며, 망의 토폴로지 구성의 측면에서는 전체적인 영역의 커버리지를 향상시키는 동시에 제한된 배터리 자원을 효율적으로 관리 할 수 있는 걸과를 얻게 된다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.776-796
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• 2010

Integrated RFID-WSNs (wireless sensor networks) have recently been researched to provide object identities, sensing information, mobile service, and network functionalities. In integrated RFID-WSNs, the reader collision is one of the critical problems. Above all, due to the absence of universally applicable anti-collision protocols and the channel capture phenomenon, the medium access control protocols in integrated RFID-WSNs suffer from reader collision and starvation problems. In this paper, we propose an efficient MAC protocol, called EMP, to avoid the above problems in integrated RFID-WSNs. EMP is a CSMA-based MAC protocol which is compatible with sensor networks operating on integrated nodes which consist of an RFID reader and a senor node. EMP resolves not only the reader collision problem, but also the starvation problem using a power control mechanism. To verify the performance of EMP, we compared it with other anti-reader collision MAC protocols using simulations. As a result, the performance of EMP showed improvements in throughput, system efficiency, and energy consumption compared to the single data channel protocols (CSMA/CA, Pulse, and DiCa) in dense deployment environments.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.5
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• pp.139-145
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• 2015

This paper proposes to increase the node energy effienciecy, which rapidly drops during the transmission of LEACH (Low Energy Adaptive Clustering Hierachy), using the method of DL-LEACH (Dual-hop Layered LEACH). By introducing dual-hop method in the data transmission, the proposed single-hop method for short-range transmission and multi-hop transmission method between the cluster heads for remote transmission was introduce. By introducing a partial multi-hop method in the data transmission, a single-hop method for short range transmission method between the cluster heads for remote transmission was introduces. In the proposed DL-LEACH, the energy consumption of cluster head for remote transmission reduces and increases the energy efficiency of sensor node by reducing the transmission distance and simplifying the transmission routine for short-range transmission. As compared the general LEACH, it was adapted to a wider sensor field.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1423-1430
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• 2016

The MAC protocols, which are classified into synchronous and asynchronous MAC protocol in the wireless sensor network, have actively studied. Especially, the asynchronous MAC protocol needs to research on the algorithm synchronizing between nodes, since each node independently operates in its own duty cycle. Typically, Receiver-Initiated MAC protocol is the algorithm synchronizing particular nodes by using beacon immediately transmitted by each node when it wakes up. However, the sender consumes unnecessary energy because it blankly waits until receiving the receiver's beacon, even if it does not know when the receiver's beacon is transmitted. In this paper, we propose the MAC protocol which can improve the performance by selecting an optimal node between a sender and a receiver to overcome the disadvantages. The simulation results show that the proposed algorithm improves energy efficiency and decreases average delay time than the conventional algorithm.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.495-498
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• 2008

This paper describes design of a real-time, wearable reflectance pulse oximetry which is based Wireless Sensor Network. For the purpose of continuously monitoring vital signs of a human, wearable reflectance pulse oximetry is built into a wrist type that can be obtained $SpO_2$ value of patient unobtrusively. This designed $SpO_2$ module is based on a low-power 8 bit ATmega128L microcontroller operating in 3V. Low power operating $SpO_2$ module was integrated to wireless sensor node for user's health monitoring. This paper is focused on the successful integration of all these components into wearable reflectance pulse oximetry and evaluates its ability to measure patient' $SpO_2$ value. Information from this sensor was wirelessly transmitted to a base-station for storage and display purposes.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.6
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• pp.151-158
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• 2010

In line with the requirement of appropriate protocol support for such mission-critical wireless sensor network (WSN) applications as patient monitoring, we investigate the framework for designing medium access control (MAC) schemes. The data traffic in medical systems comes with inherent traffic heterogeneity as well as strict requirement of reliability according to the varied extents of devise-wise criticality in separate cases. This implies that the quality-of-Service (QoS) issues are very distinctly delicate requiring specialized consideration. Besides, there are features in such systems that can be exploited during the design of a MAC scheme. In a monitoring or routine surveillance application, there are degrees of regularity or predictability in traffic as coordinated from a node of central control. The coordinator thus takes on the role of marshaling the resources in a neighborhood of nodes deployed mostly for upstream traffic; in a collision-free scheme, it schedules the time slots for each superframe based on the QoS specifications. In this preliminary study, we identify the key artifacts of such a MAC scheme. We also present basic performance issues like the impact of superframe length on delay incurred, energy efficiency achieved in the network operation as obtained in a typical simulation setup based on this framework.

• Journal of the Korea Society of Computer and Information
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• v.29 no.6
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• pp.175-182
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• 2024

In wireless sensor networks, batteries limit lifespan, and heavy data transmission around the sink causes the hotspot problem. To address this, data collection amounts are allocated to child nodes to limit transmission. However, this approach has issues with nodes far from the sink having excessive energy and failing to transmit the allocated amount due to data transmission errors. This paper proposes a method to prevent sensor data loss through error recovery via retransmission. The method ensures that each node's retransmission volume stays within its allocated data amount and energy limits, using excess energy for error recovery. Simulations show that this technique effectively recovers data transmission errors, collects data, minimizes energy depletion around the sink, and increases data collection rates.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.5
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• pp.887-898
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• 2009

Conventional routing protocols proposed for wireless sensor networks (WSNs) cannot fully accommodate the characteristics of WSNs. In particular, although it is possible to largely obtain benefits in the solution of energy consumption and global identification problems through applying position information, there are few protocols that actively apply such position information. In the case of geographical and energy aware routing (GEAR) that is a typical algorithm, which uses position information, it does not fully represent the characteristics of WSNs because it is limited to forward query messages and assumed as fixed network environments. The routing protocols proposed in this paper defines the direction of data, which is routed based on the position information of individual and target nodes, in which each node configures its next hop based on this direction and routes signals. Because it performs data-centric routing using position information, it does not require certain global identifications in order to verify individual nodes and is able to avoid unnecessary energy consumption due to the forwarding of packets by defining its direction.