• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.10
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• pp.838-844
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• 2013

In this paper, we propose a novel spectrum sensing scheme based on sensing time partitioning for cognitive radio systems in high traffic environments. Specifically, we partition a sensing time into K sub-sections, and then, propose a spectrum sensing scheme that determines if a primary user signal is present based on the sensing results on the partitioned sub-sections. From numerical results, it is confirmed that the proposed scheme outperforms the conventional schemes in high traffic environments.

• Journal of KIISE:Information Networking
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• v.29 no.2
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• pp.181-187
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• 2002

Connection admission control(CAC), which decides whether or not to accept a new call request, is one of the most Important preventive congestion control techniques in asynchronous transfer mode(ATM) networks. To develop a practical CAC scheme, first we propose a "Modified Cell Loss Probability MP${\nu}"$, which is based on "Virtual Cell Loss Probability P${\nu}"$, taking into account mean burst duration of input traffic source and buffer size in ATM networks. MP${\nu}"$ computes more accurate cell loss probability than P${\nu}"$ without increasing computational complexity, since P${\nu}"$ is formulated simply form the maximum and the average cell rate of input traffic. P${\nu}"$ is overestimated as compared to the real cell loss probability when the mean burst duration is relatively small to the buffer capacity. Then, we Propose a CAC scheme, based on "Modified Virtual Bandwidth(MVB)" method, which may individualize the cell loss probabilities in heterogeneous traffic environments. For the proposed approach, we define the interference intensity to identify interferences between heterogeneous traffic sources and use it as well as MP${\nu}"$ to compute MVB. Our approach is well suitable for ATM networks since it provides high bandwidth utilization and guarantees simple and real time CAC computation for heterogeneous traffic environments.heterogeneous traffic environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10A
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• pp.1532-1538
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• 1999

In general, because error rate of wireless link is higher than that of wired link, DLC layer protocol for wired network with low error rate is not proper for wireless environments. In addition, the conventional DLC layer protocol for wireless network is optimized for the low-speed data service, so it is difficult to use conventional DLC protocol in the current mobile communication environments handing high-speed and multimedia services. Therefore, a DLC layer protocol that is suitable to current wireless communication environments is required. In this paper, we propose a novel error control scheme that supports a variety of traffic attribute and is applicable to high-speed and multimedia data service in WATM. The proposed scheme provides enhanced throughput performance for real-time traffic by using modified ASR ARQ without ACK and reduces loss rate by using FEC in the case of high error condition. Also, for non real-time traffic, the use of ASR ARQ without ACK enhances throughput performance and delay time is decreased by using FEC in the case of high error rate channel. As a result of simulation, the proposed scheme has better performance than conventional ASR ARQ protocol in view of delay and throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11B
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• pp.1676-1684
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• 2010

Tactical network environments are characterized by unreliable connectivity, communication links which has limited bandwidth compared to commercial networks and distributed architecture where users have high mobility. The best route should be selected based on the required traffic characteristics which can be a wireless channel environments and a status of nodes which are moving. Those characteristics are self aware and should be a routing decision factor in order to guarantee a reliable data transfer. In this paper we define the requirements of services and traffic characteristics on tactical network environments and suggest the new routing method "AODV-IMTC" based on selective routing metric to enable efficient data transfer in wireless ad hoc networks.

• Journal of Korea Society of Digital Industry and Information Management
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• v.13 no.4
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• pp.41-48
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• 2017

It is necessary to develop an LED traffic light lens having a snow removal function capable of clearly providing a traffic signal to the driver even when a traffic light is blurred due to heavy snow and wind in the winter season. This study is focused on the research and development of the traffic light lens in the process of developing the LED traffic light with the snow removal function. In the developed traffic light lens, instead of attaching the film heater, the coated nichrome wire was wound into a coil shape and inserted directly into the groove in the lens. The developed heater system facilitates the insertion of the heating wire with high elasticity into a curved lens and can provide a sufficient heat without deformation of the PC lens. The proposed traffic lights were tested in various external environments and the test results showed that complete snow removal is possible without tunnel effect.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.4
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• pp.237-250
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• 2015

This paper describes a hardware-oriented algorithm and its conceptual implementation in a real-time speed limit traffic sign detection system on an automotive-oriented field-programmable gate array (FPGA). It solves the training and color dependence problems found in other research, which saw reduced recognition accuracy under unlearned conditions when color has changed. The algorithm is applicable to various platforms, such as color or grayscale cameras, high-resolution (4K) or low-resolution (VGA) cameras, and high-end or low-end FPGAs. It is also robust under various conditions, such as daytime, night time, and on rainy nights, and is adaptable to various countries' speed limit traffic sign systems. The speed limit traffic sign candidates on each grayscale video frame are detected through two simple computational stages using global luminosity and local pixel direction. Pipeline implementation using results-sharing on overlap, application of a RAM-based shift register, and optimization of scan window sizes results in a small but high-performance implementation. The proposed system matches the processing speed requirement for a 60 fps system. The speed limit traffic sign recognition system achieves better than 98% accuracy in detection and recognition, even under difficult conditions such as rainy nights, and is implementable on the low-end, low-cost Xilinx Zynq automotive Z7020 FPGA.

• Journal of Korea Spatial Information System Society
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• v.10 no.4
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• pp.89-95
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• 2008

In this paper, we propose an integrated techniques for managing data quality in traffic data warehousing environments. We describe how to collect and construct the traffic data warehouses from the operational databases, such as FTMS and ARTIS. We explain how to configure the traffic data warehouses efficiently. Also, we propose a quality management techniques to provide high quality traffic data for various analytical transactions. Proposed techniques can contribute in providing high quality traffic data to the traffic related users and researcher, thus reducing data preprocessing and evaluation cost.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.307-312
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• 2000

In this paper, in order to improve the performance of TCP short traffic services in wireless Internet environments, the Split-ACKs(SPACK) scheme is proposed. In wireless networks, unlike wired networks, packet losses will occur more often due to high bit error rates. Therefore, each packet loss over wireless links results in congestion control procedure of TCP being invoked at the source. This causes severs end-to-end performance degradation of TCP. In this paper, to alleviate the TCP performance, the SPACK method split acknowledgement packets in the base station is proposed. Using computer simulation the performance of TCP using SPACK is analyzed and shows better performance than traditional TCP protocol.

• Journal of Preventive Medicine and Public Health
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• v.28 no.4 s.51
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• pp.773-782
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• 1995

The purpose of this study is to reveal how the road traffic noise influences on the response of teachers and students, which composed of conversation, studying, relaxation, and physical disturbances. The research method used in this study was self-administrated questionnaire. Samples of the survey were composed of 420 persons(114 teachers and 306 students) who are exposed to traffic noise less than 65 dB(A) from two junior high schools and 410 persons(140 teachers and 270 students) from two noisy junior high schools which the road traffic noise above 65 dB(A). In the response of both of the teachers and students in noisy(above 65 dB) schools complaints of disturbances of conversation, studying, relaxation, and physical disturbances are much higher than that of less noisy schools' teachers and students(p<0.01). On the occasion of time and season, the subjects answered the traffic noise cause high troublesome and stresses in the afternoon(12:00 - 17:00) and summer respectively. It is necessary to provide governmental comprehensive and fundamental measures to improve the noisy school environments.

• Journal of KIISE
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• v.42 no.2
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• pp.203-212
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• 2015

This paper proposes a traffic sign recognition method in real road environments. The video stream in driving environments has two different characteristics compared to a general object video stream. First, the number of traffic sign types is limited and their shapes are mostly simple. Second, the camera cannot take clear pictures in the road scenes since there are many illumination changes and weather conditions are continuously changing. In this paper, we improve a modified census transform(MCT) to extract features effectively from the road scenes that have many illumination changes. The extracted features are collected by histograms and are transformed by the dense descriptors into very high dimensional vectors. Then, the high dimensional descriptors are encoded into a low dimensional feature vector by Fisher-vector coding and Gaussian Mixture Model. The proposed method shows illumination invariant detection and recognition, and the performance is sufficient to detect and recognize traffic signs in real-time with high accuracy.