Gang Uk Hwang

Bio: Gang Uk Hwang is an academic researcher from KAIST. The author has contributed to research in topics: Wireless network & Network packet. The author has an hindex of 16, co-authored 101 publications receiving 894 citations. Previous affiliations of Gang Uk Hwang include University of Waterloo & Electronics and Telecommunications Research Institute.

Contribution-Based Energy-Trading Mechanism in Microgrids for Future Smart Grid: A Game Theoretic Approach

Abstract: This paper designs a contribution-based energy-trading mechanism among microgrids in a competitive market. In each fixed time interval, each microgrid can be an energy provider or a consumer according to their energy generation and local demand. Under the trading mechanism, there is a distributor which gathers the surplus energy from providers and distributes it to the consumers based on the consumers’ historical contribution level. To design the trading mechanism, a novel contribution-based energy allocation policy (EAP) is proposed. Each consumer who knows this distribution rule decides the amount of requesting energy in order to maximize its utility, i.e., the quantity of energy it will receive. Finally, the economic benefits of such trading mechanism are studied by analyzing the decision-making procedures of consumers and distributor. The problem is formulated as a noncooperative energy competition game (ECG) among the consumers. The existence and the uniqueness of Nash equilibrium (NE) are shown, and the NE solution is given as a closed form. Also, even though there are foolish consumers which do not take the given NE solution, a consumer which takes the NE solution will not lose out on its utility. The proposed energy-trading mechanism is stable enough to be applied to a practical microgrid trading market.

Enhanced Markov Chain Model and Throughput Analysis of the Slotted CSMA/CA for IEEE 802.15.4 Under Unsaturated Traffic Conditions

Abstract: In this paper, we propose an analytical Markov chain model of the slotted carrier-sense multiple-access/collision-avoidance (CSMA/CA) protocol for IEEE 802.15.4 under unsaturated traffic conditions. Our proposed Markov chain model reflects the characteristics of the IEEE 802.15.4 medium-access control (MAC) protocol, such as a superframe structure, acknowledgements, and retransmissions with and without limit. We evaluate the throughput performance of the slotted CSMA/CA and verify the analytical model using simulation results.

On the Exact Analysis of a Discrete-Time Queueing System with Autoregressive Inputs

Abstract: In this paper, we provide an exact analysis of a discrete-time queueing system driven by a discrete autoregressive model of order 1 (DAR(1)) characterized by an arbitrary marginal batch size distribution and a correlation coefficient. Closed-form expressions for the probability generating function and mean queue length are derived. It is shown that the system performance is quite sensitive to the correlation of the arrival process. In addition, a comparison with traditional Markovian processes shows that arrival processes of DAR(1) type exhibit larger queue length as compared with the traditional Markovian processes when the marginal densities and correlation coefficients are matched.

Event-Driven Energy Trading System in Microgrids: Aperiodic Market Model Analysis With a Game Theoretic Approach

Abstract: This paper presents the design of an event-driven energy trading system among microgrids. Each microgrid can be either a provider or a consumer depending on the status of its energy generation and local demands. Under this approach, an aperiodic market model is newly proposed such that trading occurs when one of the consumers requests energy from the trading market. To promote the trading system, a consumer-side reward concept is introduced. The consumer makes a decision on the size of the posted reward to procure energy depending on its required energy level. Providers then react to this posted reward by submitting their energy bid. Accordingly, the posted reward is allocated to the providers in proportion to their energy bids. Moreover, for practical concerns, a transmission and distribution loss factor is considered as a heterogeneous energy trading system. The problem is then formulated as a non-cooperative Stackelberg game model. The existence and uniqueness of Stackelberg equilibrium (SE) are shown and the closed form of the SE is derived. Using the SE, an optimal trading algorithm for microgrids is provided. The stability of the energy trading system is verified due to the unique SE. In this approach, no expected waiting time for trading is required for sustaining an energy trading market.

Design of a fair scheduler exploiting multiuser diversity with feedback information reduction

Abstract: In this letter, we propose a new downlink fair scheduling scheme exploiting the multiuser diversity to enhance the transmission capacity. In the proposed scheme, only the MSs (mobile stations) whose normalized SNR (signal-to-noise ratio) values are larger than a given threshold feedback one-bit information to the BS (base station). As a result, while achieving the strict fairness, the proposed scheme can efficiently utilize the spectrum by reducing the considerable amount of the feedback information, compared to the proportional fair scheduling scheme where all the MSs feed back the normalized SNR values to the BS. Numerical studies show that the transmission capacity in the proposed scheme with a suitable value of the threshold is very close to that in the proportional fair scheduling scheme.

IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions

Abstract: This document provides updates to IEEE Std 802.16's MIB for the MAC, PHY and asso- ciated management procedures in order to accommodate recent extensions to the standard.

Applied Probability and Queues

Abstract: (1987). Applied Probability and Queues. Journal of the Operational Research Society: Vol. 38, No. 11, pp. 1095-1096.