• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.6 s.324
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• pp.33-39
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• 2004

Design of efficient Medium Access Control (MAC) protocols with both high throughput performances is a major focus in distributed contention based MAC protocol research. In this paper, we propose an efficient contention based MAC protocol for wireless Local Area Networks, namely, the Developed Collision Resolution (DCR) algorithm. This algorithm is developed based on the following innovative ideas: to speed up the collision resolution, we actively redistribute the backoff timers for all active nodes; to reduce the average number of idle slots, we use smaller contention window sizes for nodes with successful packet transmissions and reduce the backoff timers exponentially fast when a fixed number of consecutive idle slots are detected. We show that the proposed DCR algorithm provides high throughput performance and low latency in wireless LANs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.4
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• pp.753-757
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• 2005

Wireless LAN was developed by alternative of LAN and because establishment was easy, have used into special field and special expenditure. Recently, Standard and a technology developed by leaps and bounds. Present is used into purpose of the Building to Building or wide connection etc. and relay of the high speed Internet and usage of picture communication that require multimedia band width. Specially, campus wireless LAM is thought that must secure radius $100\;\~\;200\;m$ dimension at the minimum 10Mbps speed as Internet transit trunk. But, there is difference as degressive here. In this paper, wireless LAN measured for effectiveness proof as Internet transit trunk in actuality utilization environment. Proved that should compose IEEE802.11b as AP more than minimum 3 when compose network to base as measuring result. Hereafter, there is the purpose that achieve performance evaluation of wireless UM in marine environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.941-944
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• 2003

This paper implement Telemetry System which is used Bluetooth. This System propose system which can detect a total amount of gas, electricity or water without a motorman, at home. BlueTooth is a close range wireless communication technology which uses a wireless frequency 2.4GHz and has a high trust and self - error correction technology according to a low power consumption quality and a high-speed frequency hopping. This makes get a high trust concerning a data transmission than an existing modem. In addition, though wireless modem is restricted by a minimal of a wireless terminal, it will be possible to coincide with the function of the portable with the low power consumption quality by using Bluetooth. And as the system on a chip of module progresses, the possibility of the snail size is present. And, Motorman who use mobility of embedded system can detect detect a total amount of gas, electricity or water outdoor. Embedded system use ARM processor that is low power processor. So it ran use long time efficiently.

• Journal of Broadcast Engineering
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• v.19 no.1
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• pp.14-23
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• 2014

This paper proposed controlling methods for SDN(Software Defined Network) based multiple radio access technology as the solutions of following two issues which were mainly occurred by explosive increasing of video traffic. The first one is a requirement for traffic off-loading caused by 3rd-party video service providers from the mobile network operator's viewpoint. The other one is a provision of high-speed video contents transmission services with low price. Furthermore, the performance evaluation was also conducted on the real test-bed which is composed of OpenStack cloud and SDN technology such as OpenFlow and Open vSwitch. A virtual machine running on the OpenStack provide a video service and the terminal which is able to use multiple radio access technology supports two 2.4GHz WLANs(Wireless Local Area Network) and three 5GHz WLANs, concurrently. Finally, we can get 820Mbps of the maximum transmission speed by using that five WLAN links for the single service at the same time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.275-281
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• 2014

Recently, the need for various underwater application systems targeting efficient resource exploration and aquatic ecosystem monitoring is rapidly increasing in littoral sea and inland waters. In this paper, we focus on the research and development of digital module of acoustic micro modem which can be used for underwater mobile communication systems and underwater sensor network systems. Specifically, a digital module of acoustic modem embedding digital signal processor is designed and implemented. On top of the developed hardware platform, physical layer frame generation and recovery and channel coding algorithms are mounted and tested in a water tank and a pond to verify its functionality and performance. According to experimental results, less than 1 percent of total computational power is consumed in the processing of frame control and convolutional code with the data rate of 1 kbps. Thus, the performance of micro modem could be improved by loading efficient baseband algorithms into the processor while maintaining the implemented hardware.

• The Transactions of the Korea Information Processing Society
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• v.4 no.11
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• pp.2662-2670
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• 1997

High speed network makes possible to transfer not only the test data but also multimedia data such as audio, image, and moving pictures and etc. In a multimedia applications, as a multimedia storage system, it is necessary to use a disk array to store and retrieve data by real time. It is important feature to various disk array parameters as a storage system on a real VOD system, such as configuration method of each disks and allocation method of multimedia data. In this paper, various parameters for the disk array are decided to be used for the video-on-demand system application by simulations in two ways. The real and simulation measurement are compared and analyzed on the performance. Simulation results shows that RAID level 5 and 256KB as striping unit and 185KB as data requests size per seconds are suitable parameter for the disk array architecture which provides MPEG-1 files with a rate of 1.5Mbps in two measurements of real and simulation.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.587-592
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• 2020

The giant information exchange enabled by the Internet of Things paradigm will likely exploit electrical lines as a ready-to-use infrastructure. The advantage of using the pre-installed infrastructure of wiring networks makes power line communication a competitive technology for broad-band communications. Therefore, there has been a growing interest towards the use of existing power line communication channels as an effective means for transmitting high speed data and Internet service. One of the main noise types affecting power line communication systems is the impulsive noise, and the focus of this work is on the impact of this impulsive noise on the performance of OFDM-QPSK systems. For the performance analysis of impulsive noise, data measured in three environments were used. Through the analysis, it is shown that OFDM-QPSK system outperforms QPSK system for most of the impulsive noise cases. Also, RS-coded OFDM-QPSK system can achieve good BER performance under 3 cases impulsive noise environment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.12
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• pp.41-49
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• 2004

Increase of internet users and new types of applied traffics, have led to demand for more bandwidth for each application. Hence, the amount of internet traffic has risen sharply and it has demanded to use limited resources, such as wavelength and bandwidth, more effectively. These kind of needs can be satisfied with OXC(Optical cross-connects) based on GMPLS that carry out IP packet switching and wavelength switching at the same time and Provide very wide bandwidth. In RSVP-TE signaling of GMPLS studied by IETF. every lambda router in core network should be able to convert wavelength. So, lots of wavelength converters and needed and building and managing cost is high. Another problem is that optimized traffic is limited. In this paper We suggest strengthened GMPLS RSVP-TE signaling algorithm for a better lightpath setup. When setup signaling is blocked suggested algorithm does not send PathErr message to Edge Router, but looks for nearest lambda router which can convert wavelength and carry out setup signaling from that node. Such algorithm can reduce the chance of blocked lightpath setup signaling and provide effective arrangement of lambda router in core network by calculating proper number of wavelength converter.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.3
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• pp.125-132
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• 2018

KVN(Korean VLBI Network) introduced the Mark6 system of the MIT haystack observatory as a recorder for data recording up to 32 Gbps for VLBI(Very Long Baseline Interferometry) observation. The Mark6 recorder can record data at up to 32Gbps when two systems and 64 HDDs are installed. However, because of the unique recording method that is characteristic of Mark6, we are introducing a large amount of data into a virtual file system, or using a general RAID method, which causes data loss when reading and transferring files at the highest recording speed or file system have. The Flexbuff system, a software recorder developed by JIVE(Joint Institute for VLBI ERIC), can be configured to operate as a data recorder through RAID configuration and network upgrades. In particular, when installed in the Mark6 system, it can record VLBI data at a maximum speed of 32 Gbps with less loss of data compared to the existing Mark6 by utilizing Mark6 resources well. In this paper, we propose that the existing Mark6 system can be operated as Mark6-Flexbuff by installing jive5ab software, and it is verified through experiment that it can be effectively used for VLBI observation operation through data recording test.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.7
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• pp.22-31
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• 2008

Cognitive radio should imply a proper sensing technique for detecting the presence of licensed users to identify the unused spectrum holes. Besides this, this information should also be used to opportunistically provide communication among secondary users. At the same time the performance of the primary user should not be declined by the secondary users. The detection of licensed users may be significantly difficult for shadowing effect. To prevail over this problem cooperative spectrum sensing, In which the combined observation information gained by multiple secondary users is employed to achieve higher performance of detection, has been inspected. However, the primary challenge of cooperative sensing lays in its ability to detect the presence of licensed user quickly and accurately. In this paper, we have used UltraWideBand (UWB) to detect the presence of licensed users and transmit the sensing information among the nodes of the network. UWB has the capability of transmitting data at a very high rate. It is unique in co-existence capability with narrow band systems. Here, we have shown that the detection probability of licensed user is improved by means of transmitting the spectrum sensing information via UWB. We also have analyzed the throughput of the proposed technique and compared the result with existing sensing method.