• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.7
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• pp.1777-1791
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• 2012

This paper considers a downlink cognitive radio (CR) network where one secondary user (SU) and one primary user (PU) share the same base station (BS). The spectrum of interest is divided into a set of independent, orthogonal subchannels. The communication of the PU is of high priority and the quality of service (QoS) is guaranteed by the minimum rate constraint. On the other hand, the communication of the SU is of low priority and the SU opportunistically accesses the subchannels that were previously discarded by the PU during power allocation. The BS assigns fractions ?? and 1 ?? of the total available transmit power to the PU and the SU respectively. Two power allocation schemes with opportunistic subchannel access are proposed, in which the optimal values of ??'s are also obtained. The objective of one scheme is to maximize the rate of the SU, and the objective of the other scheme is to maximize the sum rate of the SU and the PU, both under the PU minimum rate constraint and the total transmit power constraint. Extensive simulation results are obtained to verify the effectiveness of the proposed schemes.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.509-516
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• 2011

This paper studies a novel method to find the profit-maximizing Nash Equilibriums in allocating generation quantities with consideration of ramp-rates under competitive market environment. Each GenCo in a market participates in a game to maximize its profit through competitions and play a game with bidding strategies. In order to find the Nash equilibriums it is necessary to search the feasible combinations of GenCos' strategies which satisfy every participant's profit and no one wants various constraints. During the procedure to find Nash equilibriums, the payoff matrix can be simplified as eliminating the dominated strategies. in each time interval. Because of the ramp-rate, generator's physically or technically limits to increase or decrease outputs in its range, it can restrict the number of bidding strategies of each generator at the next stage. So in this paper, we found the Nash Equilibriums for multi-stage generation allocation game considering the ramp-rate limits of generators. In the case studies, we analyzed the generation allocation game for a 12-hour multi-stage and compared it with the results of dynamic economic dispatch. Both of the two cases were considered generator's ramp-rate effects.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.1915-1919
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• 2003

A practical method of adaptive rate allocation to source and channel codings for an independent loss channel is proposed for Internet video. It is based on the observations that the values of residual loss probabilities at the optimal code rates for different packet loss probabilities are closely clustered to the average residual loss probability for a transmission frame size n in RS(n,k) code and for a total bit rate R. These observations aye then exploited to find the code rate for maximum PSNR. Simulation results demonstrate that the proposed method achieves a near-optimal bit-rate allocation in the joint source-channel coding of H.263 and RS(n,k) codings.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.565-581
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• 2019

This paper investigates the wireless powered two way relay network (WPTWRN), where two single-antenna users and one single-antenna relay firstly harvest energy from signals emitted by a multi-antenna power beacon (PB) and then two users exchange information with the help of the relay by using their harvested energies. In order to improve the energy transfer efficiency, energy beamforming at the PB is deployed. For such a network, to explore the performance limit of the presented WPTWRN, an optimization problem is formulated to obtain the achievable rate region bounds by jointly optimizing the time allocation and energy beamforming design. As the optimization problem is non-convex, it is first transformed to be a convex problem by using variable substitutions and semidefinite relaxation (SDR) and then solve it efficiently. It is proved that the proposed method achieves the global optimum. Simulation results show that the achievable rate region of the presented WPTWRN architecture outperforms that of wireless powered one way relay network architecture. Results also show that the relay location has significant impact on achievable rate region of the WPTWRN.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.59-65
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• 2008

In this paper, a new adaptive resource allocation scheme is proposed in orthogonal frequency-division multiple access(OFDMA) systems with rate proportionality constraints. The problem of maximizing the overall system capacity with constraints on bit error rate, total transmission power and rate-proportionality for user requiring different classes of service is formulated. Since the optimal solution to the constrained fairness problem is extremely complex to obtain, a low-complexity suboptimal algorithm that separates subchannel allocation and power allocation is proposed. Firstly, the number of subchannels to be assigned to each user is determined based on the users' average signal-to-noise ratio and rate-proportion. Subchannels are subsequently distributed according to the modified max-min criterion. Lastly, based on the subchannel allocation, the optimal power allocation by solving the Language dual problem is proposed. Additionally, in order to reduce the computational complexity, iterative rate proportionality tracking algorithm is proposed for maximizing the capacity together with maintaining the rate proportionality constraint.

• Journal of the Korea Society for Simulation
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• v.32 no.4
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• pp.69-76
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• 2023

To improve the financial stability of the National Pension, an appropriate target rate of return should be established based on pension liabilities, and asset allocation policies should be formulated accordingly. The purpose of this study is to calculate the target rate of return considering the contributions of subscribers and the pension benefits, and based on this, derive an asset allocation. To do this, we utilized the internal rate of return methodology to calculate the target rate of return for each cohort. And then, we employed a Monte Carlo simulation-based re-sampling mean-variance model to derive asset allocation for each cohort that satisfy the target rate of return while minimizing risks. Our result shows that the target rate of return for each cohort ranged from 6.4% to 6.85%, and it decreased as the generations advanced due to a decrease in the income replacement rate of the National Pension. Consequently, the allocation of risky assets, such as stocks, was relatively reduced in the portfolios of future generations. This study holds significance in that it departs from the macroeconomic-based asset allocation methodology and proposes investments from an asset-liability management perspective, which considers the characteristics of subscribers' liabilities.

• Journal of Digital Contents Society
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• v.9 no.3
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• pp.433-439
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• 2008

A moving picture in online game is one of major ways to advertise online games, which gives a lot of help in playing game. In this case, a moving picture is compressed to variable bit rate for efficient storage use and network resource efficiency. Adaptable bandwidth allocation technique builds a transmission plan of a game moving picture. And, then some frames are discarded when transmission rate by the transmission plan is larger than available transmission rate, until transmission rate satisfies available transmission rate. Thus, performance evaluation factors in adaptable bandwidth allocation technique may be dependent on discarding order of a frame which transmission rate is much influenced. In this paper, in order to show the performance, a CBA algorithm, an MCBA algorithm, an MVBA algorithm, [6] and [7] algorithm were applied to a transmission plan in the adaptable band width allocation technique using various frame discard methods and performance evaluation factors were compared in among smoothing algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7A
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• pp.693-701
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• 2008

In OFDMA (Orthogonal Frequency Division Multiple Access) system that frequency reuse factor is 1, as the same channels in the neighborhood cells creates inter-cell co-channel interference which provides a resource underutilization problem, channel allocation schemes to minimize inter-cell interference have been studied. This paper proposes a new CNIR (Carrier to Noise and Interference Ratio)-based distributed Inter-cell DCA (Dynamic Channel Allocation) algorithm in the OFDMA environment with frequency reuse factor of 1. When a channel allocation is requested, if there is not a free channel in home cell or the available free channels in home cell do not satisfy a required threshold value, the proposed Inter-cell DCA algorithm finds CNIR values of available free channels in the neighborhood cells and then allocates a free channel with maximum CNIR value. Through the simulation results, we find that the proposed scheme decreases both new call block rate and forced termination rate due to new call generation at the same time because it increases channel allocation probability.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.379-382
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• 2001

In this paper, a new enhanced early fair rate allocation(EFRA＋) algorithm is proposed for ATM switches supporting ABR service. The central issue of explicit rate control algorithms for ABR service is the computation of max-min fair rates for every connection. The EFRA＋ inherits the main feature of the EFRA, uses the connection control information during the connection setup to prevent potential congestion in switches, and enhances the computation method of the max-min fair rate.

• Journal of information and communication convergence engineering
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• v.9 no.2
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• pp.155-160
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• 2011

In distributed source localization where sensors transmit measurements to a fusion node, we address the sensor selection problem where the goal is to find the best set of sensors that maximizes localization accuracy when quantization of sensor measurements is taken into account. Since sensor selection depends heavily upon rate assigned to each sensor, joint optimization of rate allocation and sensor selection is required to achieve the best solution. We show that this task could be accomplished by solving the problem of allocating rates to each sensor so as to minimize the error in estimating the position of a source. Then we solve this rate allocation problem by using the generalized BFOS algorithm. Our experiments demonstrate that the best set of sensors obtained from the proposed sensor selection algorithm leads to significant improvements in localization performance with respect to the set of sensors determined from a sensor selection process based on unquantized measurements.