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Design and Analysis of Medium Access Protocol: Throughput and Short-Term Fairness Perspective
Yunbae Kim,Ganguk Hwang IEEE 2015 IEEE/ACM transactions on networking Vol.23 No.3
<P>We consider a simple MAC protocol, called the renewal access protocol (RAP), that adopts all of the legacy 802.11 standard but the backoff stage feature. To meet two objectives in the design of the RAP-optimal throughput and high short-term fairness-we develop a mathematical model of the RAP and rigorously analyze the performance of the RAP. First, we show that the throughput performance of the RAP depends only on the expectation of the selection distribution where the backoff counter is selected, provided that the number of terminals is fixed, which is in accordance with a well-known result. Second, with the help of renewal and reliability theories, we analyze the short-term fairness of the RAP. We also show that if the RAP has a selection distribution of the New Better than Used in Expectation (NBUE) type, the RAP can guarantee high short-term fairness. Third, we construct a special binomial distribution that is obviously of the NBUE type that can achieve high short-term fairness as well as optimal throughput when used as the selection distribution of the RAP. Furthermore, by the Poisson approximation for binomial distributions, we propose to use in practice a Poisson distribution corresponding to the special binomial distribution. Numerical and simulation results are provided to validate our analysis.</P>
Kim, Yunbae,Park, Seungkeun IEEE 2018 IEEE communications letters Vol.22 No.3
<P>Recently, analytical calculations of spectrum requirements for 4G/5G systems have gained much attention from mobile industry and radio authority worldwide. Resource block (RB) scheduling based on devices’ channel conditions is important to guarantee quality of service in such systems. However, despite these attention and importance, there have been scarce works on stochastic modeling for the number of scheduled RBs in calculating spectrum requirements. Thus, in this letter, we derive a probability distribution of the number of scheduled RBs using 2-D Markov chain model, and present a calculation method and examples for LTE-A spectrum requirements based on the derived distribution.</P>
Yunbae Kim,Ganguk Hwang,Jungsun Um,Sungjin Yoo,Hoiyoon Jung,Seungkeun Park IEEE 2016 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.15 No.5
<P>As a promising solution for handling super dense wireless networks, wireless local area networks (WLANs) have been intensively considered due to their wide availability. However, the contention-based MAC protocol in WLANs should be modified because of its inefficiency. To this end, we consider a recently proposed novel MAC protocol called the renewal access protocol (RAP). With the RAP, we analyze two strategies for resolving collisions efficiently and achieving optimal throughput performance in super dense WLANs: strategies without and with grouping. First, we analyze the asymptotic behavior of the RAP itself (i.e., without grouping) as the number of terminals goes to infinity. We show that the RAP can achieve optimal throughput even in super dense WLANs and the relevant optimal access probability can be derived in a closed form. Second, we propose a grouping strategy in the RAP called the grouped RAP (G-RAP). While a grouping strategy in the IEEE 802.11ah standard is based on time division, our G-RAP is based on transmission attempts. So the G-RAP does not waste channel resources. We show that the G-RAP achieves the optimal network throughput for any group structure if terminals use the optimal access probability that we derive. Our analytical results are validated by simulation.</P>
Short-Term Fairness Analysis for the Renewal Access MAC Protocol
Yunbae Kim,Ganguk Hwang 한국산업응용수학회 2012 한국산업응용수학회 학술대회 논문집 Vol.7 No.2
As the demands for better quality of service (QoS) increases, requirements for high fairness performance for a short periods of time are also arisen in the Wireless Local Area Network (WLAN). Although the IEEE 802.11 Distributed Coordination Function (DCF) is the most widely used in WLAN, relatively little attention have been paid to improve the short-term fairness of the IEEE 802.11 DCF. In this study, we propose a simple random access protocol as an alternative of the IEEE 802.11 DCF, called the renewal access protocol, where each terminal selects a back off counter value from a priori probability distribution, called the selection distribution. We mathematically model the successful packet transmission behavior by delayed renewal process. And then we use this modeling and the Jain’s fairness index to measure the extent of short-term fairness. We conjecture that the short-term fairness is considerably affected by the variance value of selection distribution. This behavior is verified through numerical and simulation studies.
김경수(Kim Kyungsu),이영신(Lee Yungsin),김용국(Kim Yongkuk),이윤배(Lee Yunbae),김판구(Kim Panku) 한국정보처리학회 1998 정보처리학회논문지 Vol.5 No.5
In this paper, we propose the method that extract shape features using the DCT(Discrete Cosine Transform) via simple invariant normalization. To retrieve effectively, we used measures, circularity and eccentricity, as filters to reduce the number of retrieved images. The experimental results show that our method is better than the methods of Fourier Descriptors and Moment Invariant for various leaf images.