• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.9
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• pp.767-777
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• 2012

Topology control increases channel efficiency by controlling transmission power of a node, and as a result, network lifetime and throughput are increased. However, reducing transmission range causes a network connectivity problem, especially in mobile networks. When a network loses connectivity, the network topology should be re-configured. However, topology re-configuration consumes lots of energy because every node need to collect neighbor information. As a result, network lifetime may decrease, even though topology control is being used to prolong the network lifetime. Therefore, network connectivity time needs to be increased to expend network lifetime in mobile networks. In this paper, we propose an Adaptive-Redundant Transmission Range (A-RTR) algorithm to address this need. A-RTR uses a redundant transmission range considering a node status and flexibly changes a node's transmission range after a topology control is performed.

• Journal of the Korea Society of Computer and Information
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• v.19 no.2
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• pp.67-75
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• 2014

In this paper, we proposed offloading delay method which determines effectively offloading timing by measuring of handoff delay and offloading time at mobile node side in mobile environment. The propose method measures each of handoff delay and offloading time and making decision of proper offloading timing on mobile node side. Therefore, it is possible to support cloud computing without changing previous implemented cloud computing structure for fixed node in a mobile environment. We compare the energy consumption of server and node to analyze efficiency of proposed method by using existing method of energy consumption measurement. Simulation results shows the reducing energy consumption more than previous method and operation time similar to previous method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2B
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• pp.76-81
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• 2008

LEACH (Low Energy Adaptive Clustering Hierarchy) has been proposed as a routing protocol with a hierarchical structure, in order to achieve the energy efficiency that is of primary importance in the wireless sensor networks. A wireless sensor network adopting LEACH is composed of a few clusters, each of which consists of member nodes that sense the data, and head nodes that deliver the collected data from member nodes to a sink node that is connected to a backbone network. A head node in a cluster allocates TDMA slots to its member nodes without taking into account whether they have data to transmit or not, thus resulting in inefficiency of energy usage of head node that remains in active mode during the entire round time. This motivates us to propose a scheme to improve the energy efficiency of LEACH, by assigning TDMA slots only to those member nodes who have data to send. As a result, the head node can remain sleep during the period of no data transmission from member nodes, leading to the substantial energy saving. By using the ns-2 simulator, we evaluate the performance of the proposed scheme in comparison with the original LEACH. Experimental results validate our scheme, showing a better performance than original LEACH in terms of the number of outliving nodes and the quantity of energy consumption as time evolves.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4223-4239
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• 2016

In this paper, we consider an amplify-and-forward (AF) full-duplex relay network (FDRN) using simultaneous wireless information and power transfer, where a battery-free relay node harvests energy from the received radio frequency (RF) signals from a source node and uses the harvested energy to forward the source information to destination node. The time-switching relaying (TSR) protocol is studied, with the assumption that the channel state information (CSI) at the relay node is imperfect. We deliver a rigorous analysis of the outage probability of the proposed system. Based on the outage probability expressions, the optimal time switching factor are obtained via the numerical search method. The simulation and numerical results provide practical insights into the effect of various system parameters, such as the time switching factor, the noise power, the energy harvesting efficiency, and the channel estimation error on the performance of this network. It is also observed that for the imperfect CSI case, the proposed scheme still can provide acceptable outage performance given that the channel estimation error is bounded in a permissible interval.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.371-374
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• 2013

In this paper, a sensor node circuit using solar energy harvesting is proposed. PMU(Power Management Unit) manages the energy converted from a solar cell. In order to supply a constant voltage to the sensor node, an LDO (Low Drop Out Regulator) is used. The LDO drives a temperature sensor and a SAR ADC(Successive Approximate Register Analog-to-Digital Converter). The circuit has been designed in 0.35um CMOS process.

• Convergence Security Journal
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• v.13 no.6
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• pp.69-76
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• 2013

A lot of researches have been done to improve the energy efficiency of Wireless Sensor Networks. But all the current researches are based on the idea of direct communication between cluster head and sink node. Previous results assume that node can intelligently regulate signal energy according to the distance between nodes. It is difficult to implement algorithms based on this assumption. We present a multi-level routing algorithm from the sink node to all other nodes which have fixed radio wave radius. We also show the energy saving efficiency and the implementation in real WSN using the simulation result.

• Journal of Sensor Science and Technology
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• v.22 no.4
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• pp.268-275
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• 2013

Efficient energy management becomes a critical design issue for complex WSN (Wireless Sensor Network). Most of complex WSN employ the sleep mode to reduce the energy dissipation. However, it should cause the reduction of sensing coverage. This paper presents new wake-up algorithm for reducing energy consumption in complex WSN. The proposed wake-up algorithm is devised using geometric probability. It determined which node will be waked-up among the nodes having overlapped sensing coverage. The only one sensor node will be waked-up and it is ready to sense the event occurred uniformly. The simulation results show that the lifetime is increased by 15% and the sensing coverage is increased by 20% compared to the other scheduling methods. Consequently, the proposed wake-up algorithm can eliminate the power dissipation in the overlapped sensing coverage. Thus, it can be applicable for the various WSN suffering from the limited power supply.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.6
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• pp.2282-2303
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• 2021

To solve the problems of heavy computing load and system transmission pressure in energy internet (EI), we establish a three-tier cloud-edge integrated EI network based on a cloud-edge collaborative computing to achieve the tradeoff between energy consumption and the system delay. A joint optimization problem for resource allocation and task offloading in the threetier cloud-edge integrated EI network is formulated to minimize the total system cost under the constraints of the task scheduling binary variables of each sensor node, the maximum uplink transmit power of each sensor node, the limited computation capability of the sensor node and the maximum computation resource of each edge server, which is a Mixed Integer Non-linear Programming (MINLP) problem. To solve the problem, we propose a joint task offloading and resource allocation algorithm (JTOARA), which is decomposed into three subproblems including the uplink transmission power allocation sub-problem, the computation resource allocation sub-problem, and the offloading scheme selection subproblem. Then, the power allocation of each sensor node is achieved by bisection search algorithm, which has a fast convergence. While the computation resource allocation is derived by line optimization method and convex optimization theory. Finally, to achieve the optimal task offloading, we propose a cloud-edge collaborative computation offloading schemes based on game theory and prove the existence of Nash Equilibrium. The simulation results demonstrate that our proposed algorithm can improve output performance as comparing with the conventional algorithms, and its performance is close to the that of the enumerative algorithm.

• Journal of Sensor Science and Technology
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• v.25 no.5
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• pp.371-376
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• 2016

A self-powered piezoelectric energy harvester was developed for the application in wireless sensor node. The energy harvester was evaluated with power generation characteristics for the wireless sensor node for structural diagnosis of the electric power system. The self-powered wireless sensor node was set to measure temperature, vibration frequency of the electric power system. A piezoelectric harvester composed of 7 uni-morph cantilevers (functionalized as 6 generators and 1 vibration sensor) was connected to be an array and revealed to produce significantly high output power of approximately 10 mW at 120 Hz under 3.4 g((1 g = $9.8m/sec^2$). The wireless sensor node could work as the electric power generated by the developed piezoelectric harvester.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.791-795
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• 2006

하이브리드 센서 네트워크에서 static sensor node들이 초기 배치된 후, coverage-hole을 결정하여, hole을 커버할 mobile sensor node들의 필요한 수 및 위치를 결정하고 배치하는 연구는 상당한 수준에 이르렀다. 그러나 mobile sensor node들을 호출하고 배치하는데 너무 많은 에너지를 소모하고 있다. 본 논문에서는 coverage-hole에서 mobile sensor node들을 호출하기 전에 mobile sensor node들을 최대한 coverage-hole에 가깝게 배치하여, 호출하는데 소요되는 에너지를 획기적으로 절감하였다.