• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3A
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• pp.221-229
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• 2007

In this paper, we propose and analyze the optimized sleep mode for a mobile node (MN) in IEEE 802.16e wireless metropolitan area networks. Because a MN in a sleep mode specified in 802.16e specification should maintain state information with the base station currently attached, it must renew sleep state with a new base station after handover which leads to unnecessary waste of battery power. Noting that the mobility pattern of a MN is independent of call arrival patterns, we propose an optimized sleep mode to eliminate unnecessary standby period of a MN in sleep state after handover. We also propose an analytical model for the proposed scheme in terms of power consumption and the initial call response time. Simulation studies that compare the performance between the sleep mode and the optimized sleep mode show that our scheme marginally increases initial call response delay with the huge reduction in power consumption.

• Journal of KIISE:Information Networking
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• v.31 no.5
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• pp.532-543
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• 2004

Mobile Ad hoc NETworks (MANET) consist of mobile nodes which are usually powered by battery Approaches for minimizing power consumption have been proposed for all network layers and devices. IEEE 802.11 DCF (Distributed Coordination Function), a well-known medium access control protocol for MANETS, also defines a power save mode operation. The nodes in power save mode periodically repeat the awake state and the doze state in synchronized fashion. When all nodes are in the awake state, the exchange the announcements for the subsequent message transmission with neighbors. The nodes that send or receive the announcements stay awake for data transmission, and others go into the dole state. The previous works for enhancing the power save mode operation have focused on shortening the duration of the awake state. We observed that the longer sleeping period results in seriously long delivery latency and the consequent unnecessary power consumption as well, because the packets can move forward only one hop for a fixed interval. In this paper, we propose an improved protocol for the power save mode of IEEE 802.11 DCF, which allows the flooding packets to be forwarded several hops in a transmission period. Our approach does not reduce the duration of compulsory awake period, but maximizes its utilization. Each node propagates the announcements for next flooding to nodes of several hops away, thus the packets can travel multiple hops during one interval. Simulation results of comparison between our scheme and the standard show a reduction in flooding delay maximum 80%, and the unicasting latency with accompanying flooding flows near 50%, with slight increase of energy consumption.

• Information and Communications Magazine
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• v.28 no.11
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• pp.49-55
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• 2011

무선센서네트워크를 위한 무선센서노드는 한정된 전력원을 이용하여 수천에서 수만시간의 동작을 가능하게 해야하므로 초저전력 (Ultra Low Power: ULP) 소모가 매우 중요한 설계 요구조건이 된다. 이를 위해 센서노드의 동작 주기(Duty Cycling)를 제어하는 기법이 전체 전력소모를 줄이는 매우 중요한 기술로 사용되고 있다. 회로의 전력 소모 감소를 위한 몇 가지 중요한 기술에는 회로적으로는 전류 재사용기술과 송수선기 구조로는 Super-regenerative 구조와 On-Off Keying 송수신기 구조가 있다. 또한 ULP Radio가 휴면모드에도 Wake-up을 가능하게 하기 위해서는 초저전력 클락 발생기 회로가 1${\mu}W$이하의 전력소모로 구현할 수 있어야 한다. 이러한 사항들을 적절히 고려함으로써 초저전력 CMOS Radio를 구현할 수 있다.

• The Journal of the Korea Contents Association
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• v.12 no.5
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• pp.22-31
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• 2012

A Smartphone is an intelligent device combined mobile phone and pc's support functions, and can perform multiple functions to satisfy the demands of users. It has excellent processing power and communication modules(DMB, Wi-Fi, Bluetooth, NFC etc) to carry out the demands of users. But continuous using of battery power on processor and equipped modules causes acceleration of battery consumption. This means that effective power management in devices like smartphone is important. Therefore, the management of power consumption on system execution and communication module is a serious issue in this field of study. In this paper, we would like to propose a communication module selection algorithm based on energy consumption parameter of each communication module and data transfer time. Our scheme automatically select appropriate communication system to reduce high energy consumption on bluetooth sleep mode so that this scheme is more efficient and effective thus improving user convenience in longer usage time. Experimental results showed the 20% energy saving.

• Journal of KIISE:Information Networking
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• v.36 no.4
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• pp.339-350
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• 2009

In wireless sensor networks, the limited battery resources of sensor nodes have a direct impact on network lifetime. To reduce unnecessary power consumption, it is often the case that only a minimum number of sensor nodes operate in active mode while the others are kept in sleep mode. In such a case, however, the network service can be easily unreliable if any active node is unable to perform its sensing or communication function because of an unexpected failure. Thus, for achieving reliable sensing, it is important to maintain the sensing level even when some sensor nodes fail. In this paper, we propose a new fault-tolerance scheme, called FCP(Fault-tolerant Coverage Preserving), that gives an efficient way to handle the degradation of the sensing level caused by sensor node failures. In the proposed FCP scheme, a set of backup nodes are pre-designated for each active node to be used to replace the active node in case of its failure. Experimental results show that the FCP scheme provides enhanced performance with reduced overhead in terms of sensing coverage preserving, the number of backup nodes and the amount of control messages. On the average, the percentage of coverage preserving is improved by 87.2% while the additional number of backup nodes and the additional amount of control messages are reduced by 57.6% and 99.5%, respectively, compared with previous fault-tolerance schemes.