Seoungyoul Oh

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Adaptive bit allocation for Orthogonal Frequency Division Multiplexing (OFDM)-based systems are critical for avoiding performance degradation due to additional bit allocations when channel conditions are bad. In this paper, we present two novel bit-loading algorithms for OFDM-based systems with target bit rate and fixed energy constraints. The proposed(More)
Cognitive radio is one of the most promising solutions to spectrum-scarcity problem. In cognitive radio networks, the most important requirement is to avoid interference between the primary and secondary users. However, different primary users require different levels of protection. Moreover, the extent of interference that a primary user can tolerate may(More)
Orthogonal Frequency Division Multiplexing (OFDM) has been thoroughly investigated as an enabling technology for future broadband multimedia communication. In this paper, we suggest adaptive bit allocation algorithms that operate in a frequency selective fading channel environment by exploiting channel state information obtained through a feedback channel.(More)
1570-8705/$ see front matter 2012 Elsevier B.V. All rights reserved. q This paper is based partly on preliminary works presented at AINA 2009, Bradford, UK, May. 2009. ⇑ Corresponding author. Tel.: +82 54 279 5655; fax: +82 54 279 5699. E-mail addresses: (K.-S. Lee), (S.(More)
In conventional infrastructure wireless networks, access points and nodes use omni-directional antennas. In a crowded situation, users have experienced throughput degradation due to various reasons. In this paper, we propose wireless LANs equipped with switchable directional antennas and a directional MAC protocol designed for them. In the proposed wireless(More)
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