• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3563-3570
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• 2010

MAC protocol has been studied for reducing energy consumption in wireless sensor networks. The overhearing and idle In the existing asynchronous MAC Protocol will occur due to unnecessary energy consumption. In this paper, to solve these problems, the Preamble to change the structure of the destination address, the Preamble of the end times, the data including the length of the Preamble and Data Overhearing reduce the length of the Check Interval Data generated according to the presence of the Dynamic Value dynamically adjustable by changing the DPL (Dynamic Preamble Length)-MAC protocol was proposed. Moreover, the existing asynchronous MAC protocol of wireless sensor networks and DPL-MAC protocol proposed in this paper to simulate the energy consumption and latency were assessed in terms of comparative analysis.

• KIISE Transactions on Computing Practices
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• v.23 no.7
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• pp.428-433
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• 2017

Recently, the demand for high performance non-volatile memory storage devices that can replace existing hard disks has been increasing in environments requiring high performance computing such as data-centers and social network services. The performance of such non-volatile memory can greatly depend on the interface between the host and the storage device. With the evolution of storage interfaces, the non-volatile memory express (NVMe) interface has emerged, which can replace serial attached SCSI and serial ATA (SAS/SATA) interfaces based on existing hard disks. The NVMe interface has a higher level of scalability and provides lower latency than traditional interfaces. In this paper, an evaluation and analysis are conducted of the performance of NVMe storage devices through various workloads. We also compare and evaluate the cost efficiency of NVMe SSD and SATA SSD.

• Journal of Broadcast Engineering
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• v.21 no.6
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• pp.986-994
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• 2016

In this paper, a digital closed-circuit television (CCTV) transmission system called the extended reach high definition serial digital interface (ER-SDI) is proposed to increase the transmission distance while preserving the quality using digital modulation. The current standard of HD-serial digital interface (HD-SDI) has the maximum transmission distance of 200 m. Recently, one system which transforms the digital signal to an analog signal and modulates color signal to extend the transmission distance is proposed. Another system which uses IP network is also proposed. However, the former system has a disadvantage of video quality and the latter system has high latency. The proposed ER-SDI is designed to extend the transmission distance of 518 m by adopting multilevel constellations and a channel code for a data rate of 1.485 Gbps. The maximum transmission distance of the proposed system is calculated using the specification of HD-SDI and the experiment result under coaxial cable environment.

• The Journal of the Korea Contents Association
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• v.20 no.8
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• pp.42-53
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• 2020

With the development of social network services, graph structures have been utilized to represent relationships among objects in various applications. Recently, a demand of subgraph matching in real-time graph streams has been increased. Therefore, an efficient approximate Top-k subgraph matching scheme for low latency in real-time graph streams is required. In this paper, we propose an approximate Top-k subgraph matching scheme considering data reuse in graph stream environments. The proposed scheme utilizes the distributed stream processing platform, called Storm to handle a large amount of stream data. We also utilize an existing data reuse scheme to decrease stream processing costs. We propose a distance based summary indexing technique to generate Top-k subgraph matching results. The proposed summary indexing technique costs very low since it only stores distances among vertices that are selected in advance. Finally, we provide k subgraph matching results to users by performing an approximate Top-k matching on the summary indexing. In order to show the superiority of the proposed scheme, we conduct various performance evaluations in diverse real world datasets.

• Journal of KIISE
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• v.44 no.8
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• pp.854-859
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• 2017

Caching popular videos in the storage of base stations is an efficient method to reduce the transmission latency. This paper proposes an incentive proactive cache mechanism in the wireless network to motivate the content providers (CPs) to participate in the caching procedure. The system consists of one/many Infrastructure Provider (InP) and many CPs. The InP aims to define the price it charges the CPs to maximize its revenue while the CPs compete to determine the number of files they cache at the InP's base stations (BSs). We conceive this system within the framework of Stackelberg game where InP is considered as the leader and CPs are the followers. By using backward induction, we show closed form of the amount of cache space that each CP renting on each base station and then solve the optimization problem to calculate the price that InP leases each CP. This is different from the existing works in that we consider the non-uniform pricing scheme. The numerical results show that InP's profit in the proposed scheme is higher than in the uniform pricing.

• The Journal of the Korea Contents Association
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• v.16 no.5
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• pp.251-258
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• 2016

Recently, the demand for fast storage devices is rapidly increasing in cloud platforms, social network services, etc. Despite the development of fast storage devices, the traditional Linux I/O stack is not able to exploit the full extent of the performance improvement since it has been optimized for disk-based storage devices. In this paper, we propose an optimized I/O stack which can fully utilize the I/O bandwidth and latency of fast storage devices. To this end, we design a new I/O interface to replace the current block I/O interface and optimize our I/O interface. Our optimized I/O interface bypasses operations/layers in block I/O subsystems of the current Linux I/O stack to fully exploit fast storage devices. We also optimize the Linux file systems such as ext2 and ext4 to run on our I/O interface. We evaluate our I/O stack with multiple benchmarks and the experimental results show that our I/O stack achieves 1.7 times better throughput compared to traditional Linux I/O stack.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.838-849
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• 2005

Fast handover protocol provides seamless handover in mobile Ipv6 networks by reducing handover latency. This paper proposes FMIP-M mechanism to apply this advantage of fast handover protocol to multicast service. The FMIP-M is a fast handover mechanism that supports a reliable multicast service in mobile Ipv6 networks. When hosts move other networks, they may have seine data missing and out-of-synch problems of multicast data. The proposed mechanism provides reliable multicast transmission by compensating data losses from the previous AR. Also it provides an additional function that is able to change multicasting service types dynamically in accordance with network status related with multicasting. So that it is able to make multicast paths very close to the optimum and more efficient multicast service is possible. The performance of the proposed mechanism is evaluated by a time analysis and simulations in various conditions.

• IMMUNE NETWORK
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• v.4 no.2
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• pp.73-80
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• 2004

Viruses are obligate intracellular parasites which cause infection by invading and replicating within cells. The immune system has mechanisms which can attack the virus in extracellular and intracellular phase of life cycle, and which involve both non-specific and specific effectors. The survival of viruses depends on the survival of their hosts, and therefore the immune system and viruses have evolved together. Immune responses to viral infection may be variable depending on the site of infection, the mechanism of cell-to-cell spread of virus, physiology of the host, host genetic variation, and environmental condition. Viral infection of cells directly stimulates the production of interferons and they induce antiviral state in the surrounding cells. Complement system is also involved in the elimination of viruses and establishes the first line of defence with other non-specific immunity. During the course of viral infection, antibody is most effective at an early stage, especially before the virus enters its target cells. The virus- specific cytotoxic T lymphocytes are the principal effector cells in clearing established viral infections. But many viruses have resistant mechanism to host immune responses in every step of viral infection to cells. Some viruses have immune evasion mechanism and establish latency or persistency indefinitely. Furthermore antibodies to some viruses can enhance the disease by the second infection. Immune responses to viral infection are very different from those to bacterial infection.

• Journal of the Korea Society of Computer and Information
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• v.15 no.10
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• pp.113-120
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• 2010

Video proxy server which is located near clients can store the frequently requested video data in storage space in order to minimize initial latency and network traffic significantly. However, due to the limited storage space in video proxy server, an appropriate video selection method is needed to store the videos which are frequently requested by users. Thus, we present a time constraint multiple access technique to efficiently store the video in video proxy server. If the video is requested by user, it is temporarily stored during the predefined interval and then, delivered to the user. A video which is stored is deleted or moved into the storage space of video proxy server depending on the request condition. In addition, we propose a video deletion method in video proxy server for newly stored video data. The simulation results show that the proposed method performs better than other methods in terms of the block hit rate and the number of block deletion.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.2
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• pp.1-10
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• 2010

Mapping virtual process topology to physical processor topology is one of the most important design issues in parallel programming. However, the mapping problem is complicated due to the topology irregularity and routing complexity. This paper proposes a new process mapping scheme called adjacency-based mapping (AM) for irregular cluster systems assuming that the two-dimensional mesh process topology is specified as an interprocess communication pattern. The cluster systems have been studied and developed for many years since they provide high interconnection flexibility, scalability, and expandability which are not attainable in traditional regular networks. The proposed AM tries to map neighboring processes in virtual process topology to adjacent processors in physical processor topology. Simulation study shows that the proposed AM results in better mapping quality and shorter interprocess latency compared to the conventional approaches.