• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.6
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• pp.509-516
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• 1991

In this paper, we propose on objective evaluation model of telephone transmission qulity in order to estimate a satisfaction score regarding speech quality in a relephone network. As the degradantion factors of telephone transmission quality, this model takes into account transmission loss, noise, distortion, talker echo and sidetone. A performance index[PI] is introduced for five psychological factors affecting telephone speech qualty, and a Mean Opinion Score(MOS) is estimated from the sum of all Pis. The simulation results indicate theat the MOS obtained from the objective evaluation model is in good agreement with that of subjective evaluation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.501-504
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• 1999

Chua's circuit is a simple electronic network which exhibits a variety of bifurcation and attractors. The circuit consists of two capacitors, an inductor, a linear resistor, and a nonlinear resistor. In this paper, a transmitter and a receiver using two identical Chua's circuits are proposed and a synchronizations of lossless transmission line are investigated. Since the synchronization of the transmission system is impossible by coupled synchronization, the drive-response synchronization theory were used. As a result, the chaos synchronization has delay characteristics in the lossless transmission system caused by the line parameters L and C.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.10
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• pp.1147-1154
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• 2016

A faster-than-Nyquist (FTN) transmission scheme has been attracting great attention as a spectral efficient transmission scheme. In the FTN transmission scheme, modulated symbols are transmitted at a rate higher than Nyquist rate and thus, a performance loss due to the inter-symbol interference (ISI) is unavoidable. To minimize the performance loss in the FTN transmission scheme, parameters should be carefully optimized. Unfortunately, simulation-based parameter optimization requires significant amount of time and computing power, especially for 2-dimensional FTN systems. In this paper, we propose a 2-dimensional FTN transmission scheme using the optimized parameters based on numerical analysis and simulation results on the ISI. Compared with the conventional Nyquist system, the proposed 2-dimensional FTN transmission scheme not only offers virtually identical bit error performance but also offers higher spectral efficiency.

• Journal of Internet Computing and Services
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• v.15 no.2
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• pp.1-7
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• 2014

This paper presents an analytical method for finding the optimum transmission range in mobile ad hoc networks(MANETs). The results are particularly useful for the operation of military networks, as the transmission range affects the throughput, delay, and battery consumption. Plus, the proposed method allows the optimum transmission range to be determined in advance when deploying combatants with mobile terminals. And we analyze the battery life-time and the optimum transmission range under various propagation scenarios based on Hata propagation model. The proposed method obtains the optimum transmission range in a MANET based on the operational conditions.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.12
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• pp.5898-5916
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• 2018

In this paper, the downlink performance of multi-cell distributed antenna systems (DAS) with a single user in each cell is investigated. Assuming the channel state information is available at the transmitter, four transmission modes are formulated as combinations of remote antenna units (RAUs) selection and cooperative transmission, namely, non-cooperative transmission without RAU selection (NCT), cooperative transmission without RAU selection (CT), non-cooperative transmission with RAU selection (NCT_RAUS), and cooperative transmission with RAU selection (CT_RAUS). By using probability theory, the cumulative distribution function (CDF) of a user's signal to interference plus noise ratio (SINR) and the system ergodic capacity under the above four modes are determined, and their closed-form expressions are obtained. Furthermore, the system energy efficiency (EE) is studied by introducing a realistic power consumption model of DAS. An expression for determining EE is formulated, and the closed-form tradeoff relationship between spectral efficiency (SE) and EE is derived as well. Simulation results demonstrate their consistency with the theoretical analysis and reveal the factors constraining system EE, which provide a scientific basis for future design and optimization of DAS.

• Journal of Information Processing Systems
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• v.13 no.3
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• pp.630-642
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• 2017

In this paper, we propose the opportunistic non-orthogonal multiple access (NOMA)-based cooperative relaying system (CRS) with channel state information (CSI) available at the source, where CSI for the source-to-destination and source-to-relay links is used for opportunistic transmission. Using the CSI, for opportunistic transmission, the source instantaneously chooses between the direct transmission and the cooperative NOMA transmission. We provide an asymptotic expression for the average achievable rate of the opportunistic NOMA-based CRS under Rayleigh fading channels. We verify the asymptotic analysis through Monte Carlo simulations, and compare the average achievable rates of the opportunistic NOMA-based CRS and the conventional one for various channel powers and power allocation coefficients used for NOMA.

• Journal of Korea Multimedia Society
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• v.19 no.5
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• pp.924-931
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• 2016

In this paper, Various network adaptive MAC scheduling technique is proposed to effectively overcome limits of narrow bandwidth and low transmission speed in underwater. UPFC(Underwater Packet Flow Control) is a technique to reduce both the number of transmission and transmission time using three types (Normal, Blocked, Parallel) of data transmission. In this technique, the load information, in which a transmission node have, is transmitted to destination node using marginal bit in reserved header. Then the transmitted information is referred to determine weighting factor. According to the weighting factor, scheduling is dynamically changed adaptively. The performance of UPFC is analyzed and flow control technique which can be applied to Cluster Based Network and Ad Hoc network as well.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.4
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• pp.333-340
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• 1990

분산 송전송실정보에 의한 전력시스템의 경제운용=The transmission loss information produced in a line may be shared by both end buses connected to the line. Then, the loss may be seen as if it is discretely produced at both buses. Likewise, all transmission losses can be considered as if they are discretely produced at every bus distributed. The bus transmission loss equation can be defined, in which the loss information about connected lines are contained. This formulation can greatly enhance the computational efficiency for the economic control of both real powers and voltages. It requires solutions of two linear matrix equations, one for the calculation of incremental transmission losses and the other for the determination of voltage levels to be controlled. The Proposed approach is demonstrated through three sample systems and it is found that the solutions can be obtained after three iterations regardless of system sizes. This implies that only one-step search would be required for the solution if real informations would be available. Results are compared with those of optimal power flows.

• Journal of Ubiquitous Convergence Technology
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• v.1 no.1
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• pp.35-41
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• 2007

In mobile ad-hoc wireless networks, one of the most important challenging issues is how to conserve energy, maximizing the lifetime of route(networks) in the view points of both power and mobility of nodes. However, many transmission methods presented in the previous works can not satisfy these two objectives simultaneously. To obtain these two goals, in this paper we propose an architecture to support power saving transmission services with route stability in mobile ad-hoc wireless networks. The proposed architecture consists of two parts, the underlying route stability method to support route(network) lifetime and the power saving transmission methods. The performance evaluation of the proposed architecture is achieved via simulation and analysis.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.5
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• pp.2267-2285
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• 2016

Information Centric Networking that uses content name instead of IP address as routing identifier can handle challenges such as traffic explosion and user mobility, but it also suffers from scalability and incompatibility problems. In this paper by combining the concept of software defined networking and Internet end to end arguments, we propose a wide area deployable software defined information centric networking service model named SD-ICN. SD-ICN employs a dual space structure that separates edge service network and core transmission network. The enhanced SDN techniques are used in edge service network in order to implement intelligent data routing and caching, while traditional IP technique is reserved in core transmission network so as to provide wide area high speed data transmission. Besides, a distributed name resolution system based on the cooperation of different controllers is also presented. The prototype experiments in our campus network show that SD-ICN can be deployed in a scalable and incremental way with no modification of the core network, and can support typical communication modes such as multicast, mobility, multihoming, load balancing, and multipath data transmission effectively.