Journal of Communications and Networks

  • 제10권1호
  • /
  • Pages.71-78
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  • 2008
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  • 1229-2370(pISSN)
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  • 1976-5541(eISSN)
한국통신학회 (The Korean Institute of Commucations and Information Sciences)
권호 표지

Sub-band Spreading Technique for Adaptive Modulation in OFDM Systems

  • Jung, Bang-Chul (KAIST Institute for Information Technology Convergence) ;
  • Kwon, Jae-Kyun (School of Electrical Engineering and Computer Science, Yeungnam University) ;
  • Jin, Hu (School of Electrical Engineering and Computer Science, KAIST) ;
  • Sung, Dan-Keun (School of Electrical Engineering and Computer Science, KAIST)
  • 발행 : 2008.03.31
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초록

We propose a sub-band spreading technique for adaptive modulation (AM) in orthogonal frequency division multiplexing (OFDM) systems in order to reduce signaling overheads and to average frequency selective fading channels causing different signal-to-noise ratio (SNR) values for subcarriers in each subband. The conventional sub-band based AM schemes can also reduce signaling overheads and complexity for allocating a resource per sub-band at a time. However, they may suffer from the channel variation in a sub-band when the sub-band size is larger than the channel coherence bandwidth (BW). The sub-band spreading at the transmitter enables the received symbols in each sub-band to have an identical reliability even in a frequency selective fading channel. We rigorously analyze the averaged SNR value at the receiver of the sub-band spreading system and the analyzed average SNR in a sub-band is used for an adaptation criterion. The proposed AM scheme outperforms the conventional sub-band based OFDM scheme without spreading, and it can yield better throughput performance than the conventional subcarrier based AM schemes when we consider the signaling overheads.

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참고문헌

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