• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11A
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• pp.1035-1046
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• 2005

This paper analyzes the channel assignment techniques and their performance in the On Board Processing (OBP) satellite communication system. It suggests the new Continuous Rate Assignment (CRA) and Dynamic Rare Assignment (DRA) for improving the efficiency of channel assignment at the OBP switch. Mathematical analysis and simulation are given to evaluate the system performance. Aggregate real-time and non-real-time services are considered as different classes. Higher priority is given to voice and video real-time services to avoid delay variation. Onboard scheduler uses CRA and DRA ways to arrange the capacity allocation dynamically. An improved algorithm is given to make the channel more efficient by doing some evaluation of the switching matrix.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.5
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• pp.577-582
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• 2012

If the mobile station requests the channel allocation in mobile networks, switching center is assigned a channel to mobile station that belong to each base station. Channel allocation schemes is a fixed channel allocation, dynamic channel allocation and a hybrid approach that combines the two forms. To assign a frequency well to use resources efficiently to provide quality service to our customers. In this paper, we proposed method to assign frequencies to minimize interference between channels and to minimizes the number of searching time. The proposed method by the genetic algorithm to improve accuracy and efficiency of the verification steps and reproduction stages were used. In addition, the proposed method by comparing with other methods showed that proposed method is better through the simulations.

• Journal of Communications and Networks
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• v.17 no.4
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• pp.406-418
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• 2015

Cognitive radio networks (CRNs) have emerged as a promising solution to the problem of spectrum under utilization and artificial radio spectrum scarcity. The paradigm of dynamic spectrum access allows a secondary network comprising of secondary users (SUs) to coexist with a primary network comprising of licensed primary users (PUs) subject to the condition that SUs do not cause any interference to the primary network. Since it is necessary for SUs to avoid any interference to the primary network, PU activity precludes attempts of SUs to access the licensed spectrum and forces frequent channel switching for SUs. This dynamic nature of CRNs, coupled with the possibility that an SU may not share a common channel with all its neighbors, makes the task of multicast routing especially challenging. In this work, we have proposed a novel multipath on-demand multicast routing protocol for CRNs. The approach of multipath routing, although commonly used in unicast routing, has not been explored for multicasting earlier. Motivated by the fact that CRNs have highly dynamic conditions, whose parameters are often unknown, the multicast routing problem is modeled in the reinforcement learning based framework of learning automata. Simulation results demonstrate that the approach of multipath multicasting is feasible, with our proposed protocol showing a superior performance to a baseline state-of-the-art CRN multicasting protocol.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.5
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• pp.269-274
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• 2004

In this paper, proposed is the dual-mode algorithm of blind decision feedback equalizer (DFE) for digital terrestrial television signals. According to channel impairments, the proposed dual-mode algorithm for blind DFE operates in decision-directed mode or in blind mode of operation. The error signals being used in tap update of the equalizer are generated in the best mode of operations, so that the confidence of equalizer tap coefficient update is more accurate. As a result, it is possible to track the channel characteristics variations by automatic switching over between two modes of operations. For 8-level vestigial sideband modulated digital television signals, the mean square errors and symbol error rates of the proposed algorithm are compared with those of conventional methods. And the usability of the proposed scheme is assessed by computer simulations under various static and dynamic multipath channel environments.

• Journal of Digital Convergence
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• v.10 no.9
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• pp.375-381
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• 2012

If a mobile station requests a channel allocation in its mobile networks, the switching center assigns a channel to a mobile station that belongs to each base station. There are three kinds of channel allocation schemes; a fixed channel allocation, a dynamic channel allocation and a hybrid combination of these two forms. In assigning a good frequency, it is our intention to provide quality service to our customers as well as to use resources efficiently. This paper proposes methods of assigning frequencies that minimize interference between channels and that also minimize the amount of searching time involved. In this paper, we propose an algorithm to per specific equipment, regardless of the number of channels that can be used as a general-purpose system, such as base stations, control stations, central office model is proposed, the existing operators manner similar to the fixed channel allocation based statistics and assigned when the conventional method and the improved method is proposed. Different ways and compared via simulations to verify the effectiveness of the proposed approach.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.12
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• pp.761-767
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• 1999

Poly-Si TFTs(polycrystalline silicon thin film transistors) fabricated on a low cost glass substrate have attracted a considerable amount of attention for pixel elements and peripheral driving circuits in AMLCS(active matrix liquid crystal display). In order to apply poly-Si TFTs for high resolution AMLCD, a high operating frequency and reliable circuit performances are desired. A new poly-Si TFT with CLBT(counter doped lateral body terminal) is proposed and fabricated to suppress kink effects and to improve the device stability. And this proposed device with BC(buried channel) is fabricated to increase ON-current and operating frequency. Although the troublesome LDD structure is not used in the proposed device, a low OFF-current is successfully obtained by removing the minority carrier through the CLBT. We have measured the dynamic properties of the poly-Si TFT device and its circuit. The reliability of the TFTs and their circuits after AC stress are also discussed in our paper. Our experimental results show that the BC enables the device to have high mobility and switching frequency (33MHz at $V_{DD}$ = 15 V). The minority carrier elimination of the CLBT suppresses kink effects and makes for superb dynamic reliability of the CMOS circuit. We have analyzed the mechanism in order to see why the ring oscillators do not operate by analyzing AC stressed device characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.731-741
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• 2009

Optical repeater is often installed at the isolated area. Spatial separation makes it possible to reduce the inter-code interference when secondary scrambling codes are used for traffic connected through repeater. In this paper, we propose five secondary scrambling code usage scenarios with the aids of optical repeater to maximize the user capacity. In order to evaluate the performance, dynamic system level simulation is performed. We also propose a base station-repeater switching where each active users can change access points by comparing the channel condition from base station and repeater thorough secondary common pilot channel (S-CPICH) signal to noise-interference ratio (SINR). Moreover, primary-secondary scramble code replacing scheme is proposed which replaces secondary scramble code with primary scramble code when a call using primary scramble code is ended and its corresponding OVSF code is available to users using the secondary scramble code

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.494-513
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• 2019

A multi-channel access problem based on hypergraph model in ultra-dense small cell networks is studied in this paper. Due to the hyper-dense deployment of samll cells and the low-powered equipment, cumulative interference becomes an important problem besides the direct interference. The traditional binary interference model cannot capture the complicated interference relationship. In order to overcome this shortcoming, we use the hypergraph model to describe the cumulative interference relation among small cells. We formulate the multi-channel access problem based on hypergraph as two local altruistic games. The first game aims at minimizing the protocol MAC layer interference, which requires less information exchange and can converge faster. The second game aims at minimizing the physical layer interference. It needs more information interaction and converges slower, obtaining better performance. The two modeled games are both proved to be exact potential games, which admit at least one pure Nash Equilibrium (NE). To provide information exchange and reduce convergecne time, a cloud-based centralized-distributed algorithm is designed. Simulation results show that the proposed hypergraph models are both superior to the existing binary models and show the pros and cons of the two methods in different aspects.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.245-248
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• 2004

본 논문에서는 텔레비전 수신기에서 채널 변경에 따른 음량 자동 보정 방법에 대해서 기술하고자 한다. 지금까지 텔레비전 수상기에서는 사용자가 방송 채널을 전환하는 경우 각 방송 채널마다 음량 레벨이 조금씩 다르다는 것을 느끼게 된다. 그러므로 이러한 채널 변경에 따른 음량 변화를 조정하기 위해 청취자가 리모컨으로 볼률을 조절하는 불편함을 줄이기 위해 자동으로 음량 변화를 보정하는 것이 요구된다. 본 논문은 채널 변경에 따른 음량 변화와 Dynamic Range 가 너무 큰 오디오 신호에 대해 자동으로 음량을 보정함으로써 청취자가 볼륨을 조절하는 불편함을 줄이는 자동 음량 보정 알고리즘을 제안하였다.

• Journal of the Optical Society of Korea
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• v.18 no.6
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• pp.739-745
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• 2014

We have demonstrated a $Ti:LiNbO_3$ electro-optic electric-field sensor utilizing a $1{\times}2$ Y-fed balanced-bridge Mach-Zehnder interferometric (YBB-MZI) modulator, which uses a 3-dB directional coupler at the output and has two complementary output waveguides. A dc switching voltage of ~25 V and an extinction ratio of ~12.5 dB are observed at a wavelength of $1.3{\mu}m$. For a 20 dBm rf input power, the minimum detectable electric fields are ~8.21, 7.24, and ~13.3 V/m, corresponding to dynamic ranges of ~10, ~12, and ~7 dB at frequencies of 10, 30, and 50 MHz respectively. The sensors exhibit almost linear response for an applied electric-field intensity from 0.29 V/m to 29.8 V/m.