• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.973-982
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• 2004

High-speed scheduling algorithms are required for high-performance input-queued switches to achieve good performance. Various Round-Robin scheduling algonthms for Virtual-Output-Queue (VOQ) switch architectures have been proposed, hke iSLIP, DRRM (Dual Round-Robin Matching). iSLIP can achieve high performance and have already been implemented in hardware. DRRM has been proved to achieve better performance and simpler than iSLIP But neither iSLIP nor DRRM can efficiently solve the problem of the Round-Robm pointers' desynchronization. In this paper, we have proposed "Well-Regulated Pseudo-request Dual Round-Robin Matching" Algorithm. It is developed from DRRM, and can always keep the pointers' desynchronization. Since our algorithm is based on the Round-Robin scheduling, it is also simple to be implemented. And simulation results also show that our proposed algonthm performs pretty well under various, traffic models.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.34 no.3
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• pp.365-378
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• 2024

The operating system (OS) of mobiles or embedded devices is based on the Linux kernel. These OSs request random numbers from the Linux kernel for system operation, such as encryption keys and security features. To provide random numbers reliably, the Linux kernel has a dedicated random number generator (Linux Pseudo Random Number Generator, LPRNG). Recently, LPRNG has undergone a major structural changes. However, despite the major changes, no security analysis has been published on the structure of the new LPRNG. Therefore, we analyze these structural changes as a preliminary study to utilize the security analysis of the new LPRNG. Furthermore, the differences between before and after the changes are divided into cryptographic and performance perspectives to identify elements that require security analysis. This result will help us understand the new LPRNG and serve as a base for security analysis.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.1-9
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• 2006

In this paper, we propose a MIMO-OFDMA (Multi Input Multi Output-Orthogonal Frequency Division Multiple Access) system based on beamforming for performance improvement of downlink real-time traffic transmission in harsh channel conditions with low CIR (Carrier-to-Interference Ratio). In the proposed system, we first consider the M-GTA-SBA (Modified-Grouped Transmit Antenna-Simple Bit Allocation) using effective CSI (Channel State Information) calculation procedure based on spatial resource grouping, which is adequate for the combination of MRT (Maximum Ratio Transmission) in the transmitter and MRC (Maximum Ratio Combining) in the receiver. In addition, to reduce feedback information for the beamforming, we also apply QEGT (Quantized Equal Gain Transmission) based on quantization of amplitudes and phases of beam weights. Furthermore, considering multi-user environments, we propose the P-SRA (Proposed-Simple Resource Allocation) algorithm for fair and efficient resource allocation. Simulation results reveal that the proposed MIMO-OFDMA system achieves significant improvement of spectral efficiency in low CRI region as compared to a typical open-loop MIMO-OFDMA system using pseudo-orthogonal space time block code and H-ARQ IR (Hybrid-Automatic Repeat Request Incremental Redundancy).

• Journal of the Korea Society for Simulation
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• v.17 no.4
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• pp.89-97
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• 2008

In wireless personal area networks (WPANs), the successful design of channel time allocation algorithm is a key factor in guaranteeing the various quality of service (QoS) requirements for the stringent real-time constraints of multimedia services. In this paper we propose a channel time allocation algorithm for achieving a high quality transmission and high channel error tolerance of MPEG stream in the IEEE 802.15.3 high-rate wireless PANs. Our algorithm exploits the characteristics of MPEG stream. When a new MPEG stream arrives, a DEV models it by the traffic envelope and delivers the traffic envelope to the piconet coordinator (PNC) along with the channel time request. The PNC performs channel time allocation according to the envelope. Performance of the proposed scheme is investigated by simulation and analysis. Our results show that compared to conventional scheme, the proposed scheme is very effective and provides a good performance under typical channel error conditions.

• The Korean Journal of Quaternary Research
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• v.18 no.2 s.23
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• pp.107-107
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• 2004

In this paper we have introduced some results of study on stand growth pattern and stand structure of larch forest which are located in selected forest sites of Khangai and Gobi-Altai mountain ranges of Mongolia. Our investigations showed that growth intensity and stand structure in western Mongolia are very specific from the other forest vegetation zones of Mongolia. Studies on the stand structure and growth trend indicate that tree types of stand structure and different types of growth of Larix sibrica are very common in Western Mongolia. These peculiarities of stand structure and growth of larch stands in Western Monolia could be used for inventory work and an improvement of the forest management in Western Mongolian region. The larch tree is the dominant tree species in Western Mogolia. Forest cover of the region is about 15%, which is two times higher than the country's average. In this region forest area is divided into 4 forest sub-regions: the Central Khangai, Western Khangai, North Eastern Khangai and South Easterun Khangai sub-regions including taiga, pseudo taiga, sub taiga, sub-alpine and forest steppe belts. Silviculture practices and forest research management request to study forest growth trends in local and general conditions, which means to indicate a change of taxonomic characteristics of stand from time to time including diameter, height, basal area, growth stock etc. The forest management practice mostly uses tables of forest growth and yield based on the results of long term research on forest growth. Forest yield tables and other relevant forest standards of Russia are used for the forest inventory and forest management. They are not able to determine forest structure and growth peculiatities of Mongolian forests. Studies on forest resource assessment in Mongolia indicate that after logging operations and forest fires the natural regeneration of desired species such as pine and larch often does not succeed. This situation forces to take a different approach of forest management and silviculture practice depending on the stand structure and growth rate of the forest stands. According to our investigation in last years, forest growth pattern of larch forest depends mostly on stand structure, stand age and growth condition including forest soil, climate and location in different slopes. Due to improve environmental function of forest ecosystem in the region, it is needed to conduct very comprehensive study of high mountain forest ecosystem in selected sub-regions.