• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.161-166
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• 2006

In this paper, we propose optical subscriber access network to eliminate multiple access interference using 2 dimensional(D) optical frequency and time domain CDMA method. We have numerically analyzed the characteristics of proposed system. It is seen that the excess intensity noise is the major limiting factor to the system. Also it is seen that the number of simultaneous subscribers is four times as large as the conventional ID optical system under the same bit error ratio.

• The Transactions of the Korea Information Processing Society
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• v.6 no.5
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• pp.1189-1202
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• 1999

As compared with VOD data, NOD article data has the following characteristics: it is created at any time, has a short life cycle, is selected as not one article but several articles by a user, and has high access locality in time. Because of these intrinsic features, user access patterns of NOD article data are different from those of VOD. Thus, building NOD system using the existing techniques of VOD system leads to poor performance. In this paper, we analysis the log file of a currently running electronic newspaper, show that the popularity distribution of NOD articles is different from Zipf distribution of VOD data, and suggest a new popularity model of NOD article data MS-Zipf(Multi-Selection Zipf) distribution and its approximate solution. Also we present a life cycle model of NOD article data, which shows changes of popularity over time. Using this life cycle model, we develop LLBF (Largest Life-cycle Based Frequency) prefetching algorithm and analysis he performance by simulation. The developed LLBF algorithm supports the similar level in hit-ratio to the other prefetching algorithms such as LRU(Least Recently Used) etc, while decreasing the number of data replacement in article prefetching and reducing the overhead of the prefetching in system performance. Using the accurate user access patterns of NOD article data, we could analysis correctly the performance of NOD server system and develop the efficient policies in the implementation of NOD server system.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.3
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• pp.318-325
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• 2008

In this paper, a dynamic backoff adjustment method of IEEE 802.15.4 is proposed for time-critical sporadic data in a noisy factory environment. For this, a superframe of IEEE 802.15.4 is applied to a real-time mixed data (periodic data, sporadic data, and non real-time message) transmission in factory communication systems. To guarantee a channel access of real-time sporadic(non-periodic) data, a transmission method using the dynamic backoff is applied to wireless control networks. For the real-time property, different initial BE, CW parameters are used for the dynamic backoff adjustment method. The simulat-ion results show an enhancement of the real-time performance of sporadic emergency data. The proposed method provides the channel access of real-time sporadic data efficiently, and guarantee real-time transmission simultaneously within a limite-d timeframe.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.11
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• pp.1563-1567
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• 2017

Objective: The influence of substituting steam-flaked corn (SFC) for dry rolled corn (DRC) on feedlot cattle growth performance and dietary net energy when cattle are allowed either ad libitum or 2-h restricted access to the finishing diet was evaluated. Methods: Treatment effects were tested using 96 crossbred steers ($251{\pm}2kg$) during the initial 56 d of the finishing phase. Cattle were blocked by weight and randomly assigned within blocks to 16 pens (4 pens/treatment). Bunk space was sufficient (41 cm/head) to allow all steers access to the feed bunk at the same time. Treatments consisted of two finishing diets containing (dry matter basis) 77.1% corn grain processed by dry rolling (density = 0.50 kg/L) or steam flaking (density = 0.36 kg/L). Cattle were fed twice daily at 06:00 and 14:00 h, allowing for approximately 5% residual. In the case of restricted feeding, steers were allowed access to feeders for 1 h following each feeding, after which residual feed was withdrawn. Results: There were no treatment interactions on dry matter intake (DMI), average daily gain (ADG), gain efficiency (G:F), or dietary net energy (NE). Restricting feed access time reduced (p<0.01) feed intake, and hence, ADG. Substitution of SFC for DRC increased (p<0.01) ADG, feed efficiency (G:F), and estimated dietary NE, without affecting DMI. Based on tabular net energy of maintenance ($NE_m$) value (2.18 Mcal/kg) for DRC, the estimated $NE_m$ value for SFC using the replacement technique, averaged 2.44 Mcal/kg; an improvement of 10.7%. The ratio of observed-to-expected dietary NE was not affected by feed access time. Conclusion: Substitution of SFC for DRC in finishing diets for feedlot cattle enhanced ADG, gain efficiency, and the NE value of the diet. Although restriction of feed access time depressed DMI and ADG, it did not affect the comparative benefit of steam flaking toward enhancement of ADG, G:F, and dietary NE.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.46-48
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• 2005

이동 컴퓨팅 환경에서 다수의 이동 클라이언트들에게 데이터를 전달할 때는 클라이언트들의 동시 데이터 접근을 지원하는 브로드캐스트 기법을 사용하면 무선 채널 대역폭의 협소함과 클라이언트 측의 에너지 제약과 같은 단점을 해결할 수 있다. 기존 기법들은 클라이언트의 데이터에 대한 접근빈도(access frequencies)와 클라이언트의 에너지 효율(energy efficiency)을 동시에 고려하지 않았다. 따라서 원하는 데이터가 올 때까지 계속해서 채널을 들어야 함으로 인해 에너지 소비를 많이 하거나, 데이터를 얻을 때까지 추가한 많은 양의 정보에 따른 지연이 발생하는 단점이 있다. 본 논문에서는 클라이언트의 에너지 절약을 위한 tuning time을 최소화하고 실제 데이터를 얻을 때까지 소요되는 access time의 효율을 높이기 위해 데이터의 접근빈도와 에너지 효율을 동시에 고려하는 HIDAF: Hybrid Index considering Data Access Frequencies 기법을 제한한다. 제안하는 기법은 트리기반 기법과 해싱기반 기법을 함께 적용하여 구성한 인덱스를 브로드캐스트 주기에 배치한다. HIDAF 기법은 데이터 접근빈도를 고려한 트리기반 인덱스를 배치함으로써 데이터를 얻기 위한 클라이언트들의 평균 access time을 줄일 수 있고, 이러한 인덱스에 해싱기반 기법을 추가함으로써 클라이언트의 에너지 효율을 최소화하는 새로운 브로드캐스팅 기법이다. HIDAF 기법은 브로드캐스트 추기에 데이터의 접근빈도를 고려한 인덱스를 교차로 추가하여 핫 데이터에 대한 클라이언트들의 access time을 줄임으로써 전체 사용자에 대한 평균 access time을 최소화하는 동시에 클라이언트들의 제한된 에너지 소비를 최소화하는데 목적이 있다. 제안기법에 대한 평가는 수학적 분석을 통해 HIDAF 기법과 기존의 브로드캐스트 기법의 성능을 비교 분석한다.하였으나 사료효율은 증진시켰으며, 후자(사양, 사료)와의 상호작용은 나타나지 않았다. 이상의 결과는 거세비육돈에서 1) androgen과 estrogen은 공히 자발적인 사료섭취와 등지방 침적을 억제하고 IGF-I 분비를 증가시키며, 2) 성선스테로이드호르몬의 이 같은 성장에 미치는 효과의 일부는 IGF-I을 통해 매개될 수도 있을을 시사한다. 약 $70 {\~} 90\%$의 phenoxyethanol이 유상에 존재하였다. 또한, 미생물에 대한 항균력도 phenoxyethanol이 수상에 많이 존재할수록 증가하는 경향을 나타내었다. 따라서, 제형 내 oil tomposition을 변화시킴으로써 phenoxyethanol의 사용량을 줄일 수 있을 뿐만 아니라, 피부 투과를 감소시켜 보다 피부 자극이 적은 저자극 방부시스템 개발이 가능하리라 보여 진다. 첨가하여 제조한 curd yoghurt는 저장성과 관능적인 면에서 우수한 상품적 가치가 인정되는 새로운 기능성 신제품의 개발에 기여할 수 있을 것으로 사료되었다. 여자의 경우 0.8이상이 되어서 심혈관계 질환의 위험 범위에 속하는 수준이었다. 삼두근의 두겹 두께는 남녀 각각 $20.2\pm8.58cm,\;22.2\pm4.40mm$으로 남녀간에 유의한 차이는 없었다. 조사대상자의 식습관 상태는 전체 대상자의 $84.4\%$가 대부분이 하루 세끼 식사를 규칙적으로 하고 있었으며 식사속도는 허겁지겁 빨리 섭취하는 경우가 남자는 $31.0\%$, 여자는 $21.4\%$로 나타났고 이들을 제외한 나머지 사람들은 보통 속도 혹은 충분한 시간을 가지고 식사를 하였다. 평소 식사량은 조금 적게 혹은 적당하게 섭취하는 사람이 대부분이었으며 남자가 여자보다는 배부르게 먹는 경 향이 유의적으로 높았다(p<0.05). 식사는 혼자 하는 경우가 남자

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.911-923
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• 2014

Ad hoc cognitive radio wireless sensor networks allow secondary wireless sensor nodes to recognize spectrum opportunities and transmit data. Most existing protocols proposed for ad hoc cognitive radio wireless sensor networks require a dedicated common control channel. Allocating one channel just for control packet exchange is a waste of resources for channel-constrained networks. There are very few protocols that do not rely on a common control channel and that exchange channel-negotiation control packets during a pre-allocated time on the data channels. This, however, can require a substantial amount of time to access the channel when an incumbent is present on the channel, where the nodes are intended to negotiate for the data channel. This study examined channel access delay on cognitive radio wireless sensor networks that have no dedicated common control channel.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.83-87
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• 2009

The MAC protocol of HiperLAN/2 is based on TDMA/TDD. Mobile terminal acquires a data transmission opportunity as successfulness in channel competition through RCH (Random CHannel) phase. Therefore, AP (Access Point) be able to dynamically assign optimum RCH at next frame according to the number of success and collision. In this paper, we suggest scheme that fluctuate RCH (Random CHannel) number as fixed value considering success and collision for improvement of performance in HiperLAN/2. To prove efficiency of proposed scheme, a lots of simulations are conducted and analyzed in view of throughput and access delay.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.275-280
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• 2009

Femtocells are viewed as a promising option for mobile operators to improve coverage and provide high-data-rate services in a cost-effective manner Femtocells can be used to serve indoor users, resulting in a powerful solution for ubiquitous indoor and outdoor coverage. TThe frequency accuracy and phase alignment is necessary for ensuring the quality of service (QoS) forapplications such as voice, real-time video, wireless hand-off, and data over a converged access medium at the femtocell. But, the GPS has some problem to be used at the femtocell, because it is difficult to set-up, depends on the satellite condition, and very expensive. The IEEE 1588 specification provides a low-cost means for clock synchronisation over a broadband Internet connection. The Time of Packet (ToP) specified in IEEE 1588 is able to synchronize distributed clocks with an accuracy of less than one microsecond in packet networks. However, the timing synchronization over packet switched networks is a difficult task because packet networks introduce large and highly variable packet delays. This paper proposes an enhanced filter algorithm to reduce ths packet delay variation effects and maintain ToP slave clock synchronization performance. The results are presented to demonstrate in the intra-networks and show the improved performance case when the efficient ToP filter algorithm is applied.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.682-687
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• 2010

The IEEE 802.15.4a specification targets the low-rate (LR) Impulse-radio (IR) ultra-wideband (UWB) system which is now widely applied in the WPANs considering rather short distance communications with low complexity and power consumption. The physical (PHY) layer uses concatenated coding with mixed binary phase-shift keying and binary pulse-position modulation (BPSK-BPPM), and direct sequence spreading with time hopping in order that both coherent and non-coherent receiver architectures are supported. In this paper, the performances of multiple access schemes compliant with IEEE 802.15.4a specification are investigated with energy detection receiver, which allow avoiding the complex channel estimation needed by a coherent receiver. However, the performance of energy detection receiver is severely degraded by multi-user interference (MUI), which largely diminishes one of the most fascinating advantages of UWB, namely robustness to MUI as well as the possibility to allow parallel transmissions. So as to improve the performance of multiple access schemes, we propose to apply the novel TH sequences as well as to increase the number of TH positions. The simulation results show that our novel multiple access schemes significantly improve the performance against MUI.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.5
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• pp.225-231
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• 2002

This paper proposes a discriminative collision resolution scheme for the wireless Medium Access Control (MAC) protocols to support the Quality of Service (QoS) requirements of real-time applications. Our scheme deals with access requests in different ways depending on their delay requirements. In our scheme, a Collision Resolution Period (CRP) is used to quickly resolve collisions for the delay sensitive traffic in order to support their delay requirements. Performance analysis and simulation results show that our algorithm may successfully meet the delay requirements of real time applications by reducing access delays and collisions.