157,610 research outputs found
Performance analysis of M-QAM scheme combined with multiuser diversity over Nakagami-m fading channels
No full textIn this paper, we consider an M-ary quadrature amplitude modulation (M-QAM) scheme combined with multiuser diversity over Nakagami-m fading channels. Assuming that delayed but error-free signal-to-noise ratio (SNR) feedback is available, we derive closed-form formulas for the average transmission rate and the average bit error rate (BER), which are also shown to be generalizations of many previous results. Through numerical studies and simulations, we check the validity of our analysis. In addition, we investigate the impact of the Nakagami fading parameter m and feedback delay on system performance.This research was supported by the MIC (Ministry of Information and Communication), Korea, under the ITRC (Information Technology Research Center) support program supervised by the IITA (Institute of Information Technology Assessment).
Y. Kim and G. U. Hwang are with the Department of Mathematical Sciences and Telecommunication Engineering Program, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea (Email: jd [email protected]; [email protected])
Efficient Improvements on Hwang-Chen's Multi-Proxy Multi-Signature Schemes
No full textLyuu and Wu proposed a new insider attack to forge multi-proxy multi-signature in Hwang-Chen's scheme without clerks. On Hwang-Chen's scheme with clerks, they also proposed their improvement. Except the extra computation cost announced by Lyuu and Wu, the communication cost cannot be reduced in their scheme while the cost can be reduced in Hwang-Chen's scheme. Moreover, their improvement needs a center which is more trustworthy than the one in Hwang-Chen's scheme. To remove extra costs and overhead of trustworthy centers, two efficient improvements are proposed.中華民國資訊安全學會國內20050609~20050610紙本Y臺北市, 臺
Enhanced Markov Chain Model and Throughput Analysis of the Slotted CSMA/CA for IEEE 802.15.4 Under Unsaturated Traffic Conditions
No full textIn 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.Manuscript received July 24, 2007; revised January 17, 2008. This study has been supported in part by a grant “Next Generation PC Project” from the
Institute of Information Technology Assessment (IITA). The review of this
paper was coordinated by Prof. Jie Li.
C. Y. Jung, H. Y. Hwang, and D. K. Sung are with the School of Electrical Engineering and Computer Science, KAIST, Korea. (e-mail:
[email protected], [email protected], and [email protected])
G. U. Hwang is with the Department of Mathematical Sciences, KAIST,
Korea. (e-mail: [email protected]
A Biochemical Aspects of Phylogenetic Study of Bambusaceae in Taiwan IV. The Genera Arundinaria, Pseudosasa, Semiarundinaria, Shibataea, Sinobambusa, and Yushania
No full textA Korean Confucian way of life and thought: The Chasŏngnok (Record of self-reflection) by Yi Hwang (T’oegye)
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