• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3B
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• pp.114-129
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• 2005

In this paper, we examine Interleaved Polling with Adaptive Cycle Time (IPACT) algorithm which was proposed to control upstream traffic for Gigabit Ethernet-PONs, and we analyze the performance of the gated service and the limited service of the IPACT mathematically. For the mathematical performance analysis, we model IPACT algorithm as a polling system and use mean-value analysis. We divide arrival rate λ value into three regions and analyze each region accordingly. We obtain average packet delay, average queue size and average cycle time of both the gated and the limited service. We compare analytical results with simulation to verify the accuracy of the mathematical analysis. Upon now, simulation analysis have been used to evaluate the performance of EPONs, which require much time sud effort. Mathematical analysis can be widely used in the design of EPON systems since system designers can obtain various performance results rapidly.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2A
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• pp.86-96
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• 2006

In recent year, EPON(Ethernet PON) system is expected to be more attractive solutions for high speed, broadband access networks in next generation access networks due to the conversionce of low-cost ethernet equipment and low-cost fiber infrastructure. Upstream channel control algorithm is essential to hare upstream bandwidth in EPON. In this paper, we suggest HUHG(High Utilization and Hybrid Granting) algorithm for supporting high bandwidth utilization and QoS for different service class. This algorithm improves bandwidth utilization as removing or diminishing idle time of upstream channel using characteristics of fixed EF(Expedited Forwarding) sub-cycle. The proposed algorithm also minimizes the packet delay and delay variation of EF class. We conduct detailed simulation experiments using OPNET to study the performance and validate the effectiveness of the proposed algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.11
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• pp.993-1003
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• 2012

In this paper, we propose a method that wireless mobile nodes can obtain high throughput in heterogeneous wireless networks using multiple connections and it has low packet loses under handover situation. Currently, a mobile node exchanges data with server for one network connection. The proposed method can use high throughput because it doesn't only use one network(WLAN, 3G, etc.) but also use multiple wireless networks. When mobile nodes move to area to use multiple connection, mobile nodes request heterogeneous wireless networks using multiple connections message from the server and the server transmit packets using multiple connections. Also, this method doesn't disconnect previous networks, so packets losses are decreased. Using the NS-2 simulation, we verify that the propose method enhances throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11B
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• pp.1269-1276
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• 2011

In the Proxy Mobile IPv6 (PMIPv6), the data transmission performance may be degraded when the two communicating hosts are located within the same mobile domain, since all the data packet shall be delivered by way of Local Mobility Anchor (LMA). In this paper we propose an extensional scheme of PMIPv6 using binding query. In the proposed Query-based PMIPv6 (Q-PMIPv6) scheme, the Mobile Access Gateway (NAG) of Correspondent Node (CN) sends a binding query to LMA to obtain the Proxy Care-of-Address of Mobile Node (MN). Since then, CN and MN can communicate with each other by using an optimized data path. For comparison, we performed the numerical analysis and the ns-2 simulations for the proposed Q-PMIPv6 scheme and the existing PMIPv6 and PMIPv6 Localized Routing (PMIPv6-LR). From the results, we can see that the proposed scheme outperforms the existing PMIPv6 and PMIPv6-LR schemes in terms of the signaling control and data delivery costs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.9
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• pp.814-821
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• 2012

We propose a network processor called an OmniFlow processor capable of wire-speed flow management by a hardware-based flow admission control(FAC) in this paper. Because the OmniFlow processor can set up and release a wire-speed connection for flows, the update period of flows can be set to a short time, and only active flows can be effectively managed by terminating a flow that does not have a packet transmitted within this period. Therefore, the FAC can be used to provide a reliable transmission of UDP as well as TCP applications. This processor is fabricated in 65nm CMOS technology, and total gate count is 25 million. It has 40 Gb/s throughput performance in using the 32 RISC cores when maximum operating frequency is 555MHz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8A
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• pp.791-800
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• 2010

Recently wireless sensor networks as a field of ubiquitous computing technology was in the limelight. To use and collect the necessary information, Sink node mobility is essential. TTDD(Two-Tier Data Dissemination) proposed most common technique associated with Mobile sink node in wireless sensor networks, but issues exist that the use of many control packet falls into the energy efficiency. The technique for solving problems is Cluster-Based Energy-efficient Routing protocol (CBPER). But CBPER does not transmit the data correctly to sink node or source node. In this paper, we propose An Energy-Efficient Routing Protocol based on Static Grid using mobile sink nodes in order to solve the data transmission failure and reduce the energy consumption in Wireless Sensor Networks. We have evaluated it with the NS-2 simulator. Our results show that the proposed protocol saves the energy consumption up to 34% in comparison with CBPER. We also prove that the proposed protocol can transmit more accurate data to the sink de than CBPER.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.5
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• pp.435-446
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• 2014

Even if it is important to transmit high rate multimedia information without any transmission errors for surveillance systems, it is difficult to achieve error-free transmission due to infra-less adhoc networks. In order to reduce the transmission errors furthermore, additional signal overheads or retransmission of signals should be required, but they may lead to transmission delay. This paper represents a study on low delay and adaptive video transmission for the unmanned surveillance systems by developing system protocols. In addition, we introduce an efficient and adaptive control algorithm using system parameters for exploiting unmanned surveillance system properly over multi-channels.

• Journal of Korean Academy of Nursing
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• v.26 no.1
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• pp.53-72
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• 1996

The Purpose of this study was to identify characteristics of fatigue and the relationship between fatigue and related factors in patients on hemodialysis. This study was a survey study using a cross-sectional design. The subjects for this study were 101 patients on hemodialysis who were registered in the six hemodialysis clinics among a total of eleven clinics in Seoul. The period of data collection was from February 28, 1995 to May 2, 1995. Data were collected through an interview with a structured packet and the physiological data. The tools used in this study were the Visual Analogue Scale-Fatigue developed by Lee et al(1990) and translated by Lee(1991), the fatigue interview schedule developed by this researcher, Zung's self rating depression scale(Zung, 1965), the self-efficacy scale developed by Sherer et al(1982) and the Norbeck Social Support Questionnaire(NSSQ) translated by Oh(1984). The collected data were analyzed using descriptive statistics(mean, standard deviation, frequency, range), Pearson correlation coefficients and Stepwise multiple regression. The results were as follows ; 1. Characteristics of Fatigue of hemodialysis patients : 1) 79 of 101 hemodialysis patients complained fatigue. 2) The mean fatigue score as measured by the VAS-F was 36.2mm. 3) The mean duration of fatigue was 2.9 hours 2. Characteristics of fatigue related factors : 1) The physiologic factor which included Hgb, Hct, BUN, creatinine, potassium and interdialytic weight gain deviated from normal range. 2) The psychological factor which included depression and self-efficacy was about the same level as for patients with other chronic diseases. 3) The environmental factor which included social support had wide variation. 3. The relationship between fatigue and related factors : 1) Interdialytic weight gain in the physiologica factor was the only valuable with fatigue （p＜.05） 2) The relationship between fatigue and the psychological factor of depression showed a positive and strong correlation（p＜.05）. According to the findings of this study, fatigue was highly correlated with the depression. This indicates that nurses should try to assess and control psychological factors when patients complain of fatigue rather than just considering physiological factors. Nursing has to develop effective nursing interventions to reduce fatigue in patients with chronic diseases using the relationship between fatigue and physiological, psychological and environmental factors.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.2
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• pp.40-49
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• 2015

PicoCast is a recently proposed short-range wireless communications technology that supports both low rate sensor/control data and high speed data such as voice and video traffic in the personal space, defined by the user-centric space of radius tens of meters, with one unified protocol. When the users are in the same area, personal spaces defined by each user may overlap. Since these PicoCast piconets may simultaneously operate, mutual interference is unavoidable. It is necessary to investigate the effect of mutual interference on data transmission and to conduct research on minimizing the interference among PicoCast devices. In this paper we analyze the effect of mutual interference between PicoCast piconets based on data throughput using OPNET network simulator. We have implemented the PicoCast protocol and measured the average throughput and packet loss rate.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.6
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• pp.445-453
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• 2016

Fixed robust routing is attracting attention as routing that achieves high robustness against changes in traffic patterns without conducting traffic measurement and performing dynamic route changes. Fixed robust routing minimizes the worst-case maximum link load by distributing traffic of every source-destination (s-d) router pair onto multiple candidate paths (multipath routing). Multipath routing, however, can result in performance degradation of Transmission Control Protocol (TCP) because of frequent out-of-order packet arrivals. In this paper, we first investigate the influence of multipath routing on TCP performance under fixed robust routing with a simulation using ns-2. The simulation results clarify that TCP throughput greatly degrades with multipath routing. We next propose a candidate path selection method to improve TCP throughput while suppressing the worst-case maximum link load to less than the allowed level under fixed robust routing. The method selects a single candidate path for each of a predetermined ratio of s-d router pairs in order to avoid TCP performance degradation, and it selects multiple candidate paths for each of the other router pairs in order to suppress the worst-case maximum link load. Numerical examples show that, provided the worst-case maximum link load is less than 1.0, our proposed method achieves about six times the TCP throughput as the original fixed robust routing.