• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.502-504
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• 2005

S-MAC은 IEEE 802.11과 같이 경쟁 기반 MAC 프로토콜로써 무선 센서 네트워크에서 전력 소비를 줄이기 위해 제안된 프로토콜이다. 이 프로토콜은 idle listening으로 인한 전력 소모를 줄이기 위해 주기적으로 listen/sleep 상태를 반복하고 sleep 기간 동안 전력 소비를 절약하는 기법을 이용한다. 그러나 S-MAC은 데이터가 발생한 소스 노드에서 목적지 노드까지 데이터가 전달될 때 sleep 모드에 의해 데이터 전달 지연이 발생한다. 본 논문에서는 데이터 전달시 Sleep 모드에 의해 발생되는 데이터 전달 지연을 줄이기 위해 데이터 전달과 연관된 sleep 기간 중 어느 일정 기간을 데이터 송수신이 가능한 pseudo-listen 기간으로 전환하여 실시간 개념의 데이터 전달을 제공하는 프로토콜을 제안한다.

• Journal of Internet Computing and Services
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• v.8 no.2
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• pp.43-54
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• 2007

The effective power consumption is the primary issue in a sensor network which consists of the sensor nodes with limited battery power. So, most of the MAC protocols in sensor networks have been designed with the consideration of energy efficiency. Generally, these protocols make use of the listen and sleep mode periodically. However, this approach inevitably causes a long transmission delay on the data forwarding path, which is mainly resulted from the sleep time of the receiver node. This paper deals with a design of DT-MAC(Data Transmission centric MAC) protocol, with minimizes the data transmission delay while it forces each node to consume its energy efficiently. Thus, a node received a packet converts its remained sleep time to the pseudo_listen time, in which the node is able to transmit a packet. With benefit of the pseudo_listen period, the data transmission delay along with the data forwarding path will be shortened as much as it possible. Therefore, DT-MAC protocol is very suitable to the various applications which require a real time sensing data such as disaster and fire alarm.

• Journal of Korea Multimedia Society
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• v.10 no.4
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• pp.450-461
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• 2007

In this paper, we propose the method to use power-saving mode (PSM) applicable to non real-time traffic and PSM applicable to real-time traffic simultaneously, for VoIP traffic with silence suppression. The proposed method uses PSC II during talk-spurt interval of parties A and/or B and uses PSC I or probabilistic sleep interval decision (PSID) method during mutual silence interval, respectively. To evaluate the performance of hybrid PSM (HPSM) based on PSC II or PSID method, we present average buffering delay, energy consumption of mobile station and VoIP packet drop probability with simulation runs. Results shows that proposed HPSM decreases energy consumption of mobile station up to 25 % while satisfying the packet drop probability within QoS requirement in case of end-to-end VoIP connection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7B
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• pp.489-498
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• 2012

Recently, as the interest in Green IT is exponentially increased, EPON with sleep mode has been studied to reduce energy consumption in access network. In oder to guarantee cyclic sleep for ONU(Optical Network Units), EPON with sleep mode transmits upstream and downstream data at the same time. However, since conventional algorithms for sleep mode in EPON allocate bandwidth to each ONU according to upstream bandwidth request, the QoS of downstream data is not guaranteed when the offered load of OLT is larger than that of ONU. In this paper, we propose a bandwidth allocation algorithm for improving QoS in EPON with sleep mode. The proposed algorithm compares its size with an upstream request of ONU when a downstream buffer in the OLT exceeds a QoS threshold. And then it allocates selectively a bandwidth that satisfies the required QoS between the bandwidth request of ONU and OLT. Therefore, the proposed algorithm can save energy through cyclic sleep of ONUs while guaranteeing the QoS of up/downstream data. In order to evaluate the proposed algorithm, we perform simulation in terms of total sleep time of ONUs, queueing delay between OLT and ONU, and the utilization of allocated bandwidth at OLT through OPNET.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.1
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• pp.1-11
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• 2013

Reducing the energy that consumed by tag is a key requirement for the wider acceptance of the active RFID systems that use battery constrained tags. When the reader is not interrogating, the active RFID standard protocols try to reduce energy consumption of tags by using sleep mode. On sleep mode tags is active by receiving a specific signals from reader, until tag receive a sleep mode command from the reader, a tag waste energy for remaining in RX mode. Overhearing is a state of a tag in which it wastes energy for maintaining active RX state while there is no frame destined to it. According to our analysis, the amount of energy consumed by a tag due to overhearing is several time larger than that consumed by the effective communication. We propose RANO(Reservation Aloha for No Overhearing) that is designed to inform a tag of its effective communication intervals to eliminate overhearing problem in active RFID communication. The performance of the proposed protocol was evaluated through the real world by changing the number of tags and size of data. The result of an experiment, the proposed protocol performed saving about 22 times less than the standard protocol did.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06d
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• pp.238-242
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• 2007

무선이동기기의 에너지 소모를 줄이기 위해서는 무선인터페이스의 전력소모를 최대한 줄이는 것이 중요하다. 대표적인 무선통신인 IEEE 802.11 표준에서는 무선인터페이스를 수면모드로 전환하는 전력절약모드(PSM, Power Save Mode)를 정의하고 있다 그러나 수면모드로 동작하는 도중에는 데이터를 수신할 수 없으므로 전력절약과 전송지연 사이에서 조정(trade-off)을 하여야 한다. HTTP와 같이 요청-응답을 기본으로 하는 통신 응용에서는 요청 발생 후 응답이 도착할 때까지 걸리는 시간을 노드의 수면시간에 반영하면 데이터의 수신이 지연되는 문제를 완화하면서 전력절약을 할 수 있으며, 기존 연구들도 이에 착안하는 기법을 제안하고 있다. 그러나 기존 연구들은 HTTP통신이 다중적으로 발생하면 그 효과는 사라지게 된다. 본 연구에서는 기존에 제안된 기법이 갖는 문제점을 분석하고 이를 완화하기위해 응답시간 지연비율을 적용한 지연수면(Delayed Sleep) 스케줄링 기법을 제안하며 시뮬레이션을 통해 이를 검증하였다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.195-203
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• 2007

In this paper, an analytic model of sleep model operation in the IEEE 802.16e is investigated. A mobile subscribe. station (MSS) goes to sleep mode after negotiations with the base station (BS) and wakes up periodically for a short interval to check whether there is downlink traffic to it. If the arrival of traffic is notified, an MSS returns to wake mode. Otherwise, it again enters increased sleep interval which is double as the previous one. In order to consider the situation more practically, we propose the sleep mode starting threshold, during which MSS should await packets before it enters the sleep mode. By modifying the M/G/1 with multiple vacations model, energy consumption ratio(ECR) and average packet response time are calculated. Our analytic model provides potential guidance in determining the optimal parameters values such as sleep mode starting threshold, minimal sleep and maximal sleep window.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.1
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• pp.1-8
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• 2011

Efficient power management plays a crucial role to strengthen competitiveness in the market of portable mobile commodities. This paper presents a proactive power management technique, called by Energy-Aware Scheduling policY (EASY), to exploit the sleep time information of running applications. Different from previous power management approaches focusing on power conservation in standby mode, the proposed scheme characterizes each application program's operational characteristic in active mode by observing how long the task stays in sleep state of CPU scheduler. Based on the measured sleep time, the proposed EASY speculates an adequate CPU clock frequency according to the current CPU workload and scales the frequency directly to the predicted one. Experimental results show that the proposed scheme reduces the power consumption by 10-30% on average compared to traditional DPM approach, with a minimal impact on the performance overhead.

• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.4
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• pp.89-99
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• 2007

In this paper, an analytic model of a sleep mode operation in the IEEE 802.16e is investigated. A mobile subscriber station(MSS) goes to sleep mode after negotiations with the base station(BS) and wakes up periodically for a short interval to check whether there is downlink traffic to it. If the arrival of traffic is notified, an MSS returns to wake mode. Otherwise, it again enters increased sleep interval which is double as the previous one. In order to consider the situation more practically, we propose the sleep mode starting threshold, during which MSS should await packets before it enters the sleep mode. By modifying the M/G/l with multiple vacations model, energy consumption ratio(ECR) and average packet response time are calculated. Our analytic model provides potential guidance in determining the optimal parameters values such as sleep mode starting threshold, minimal sleep and maximal sleep window.

• The KIPS Transactions:PartC
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• v.17C no.3
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• pp.299-306
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• 2010

IPTV and VoIP services are considered as killer applications over Mobile WiMAX network, which provideshigh mobility and data rate. Among those which affect the quality of voice in those services, the jitter buffer or playout buffer can compensate the poor voice quality caused by the packet drop due to frequent route change or differences among routes between service endpoints. In this paper, we analyze the correlation between the sleep interval length and jitter buffer size in order to guarantee a predefined level of voice quality. For this purpose, we present an end-to-end delay model considering additional delay incurred by the WiMAX PSC-II sleep mode and a VoIP service quality requirement based on the delay constraints. Through extensive simulation experiments, we also show that the increase of jitter buffer size may degrade the voice quality since it can introduce additional packet drop in the jitter buffer under WiMAX power saving mode.